阅读说明：本技术 可变切换频率开关式储能转换器及相关方法 (Variable switching frequency switch-mode energy storage converter and related method ) 是由 S·G·帕斯托里纳 T·G·比昂迪 T·S·澎 A·皮祖泰利 M·D·麦克吉姆赛 A·J· 于 2020-01-07 设计创作，主要内容包括：一种用于控制开关式储能转换器(STC)的方法包括：(a)当该STC对具有第一大小的负载进行供电时以第一频率并且使用第一固定接通时间驱动该STC的第一谐振储能电路,以获得该STC的输出电压与该STC的输入电压的第一固定比率,以及(b)当该STC对具有第二大小的负载进行供电时以第二频率并且使用该第一固定接通时间驱动该STC的第一谐振储能电路,以获得该STC的输出电压与该STC的输入电压的该第一固定比率。该第二频率小于该第一频率,并且该第二大小小于该第一大小。(A method for controlling a switched-mode energy storage converter (STC) comprising: (a) driving a first resonant tank of the STC at a first frequency and with a first fixed on-time when the STC powers a load of a first size to obtain a first fixed ratio of an output voltage of the STC to an input voltage of the STC, and (b) driving a first resonant tank of the STC at a second frequency and with the first fixed on-time when the STC powers a load of a second size to obtain the first fixed ratio of the output voltage of the STC to the input voltage of the STC. The second frequency is less than the first frequency, and the second magnitude is less than the first magnitude.)

1. A method for controlling a switched-mode energy storage converter (STC), the method comprising:

driving a first resonant tank circuit of the STC at a first frequency and with a first fixed on-time to obtain a first fixed ratio of an output voltage of the STC to an input voltage of the STC when the STC powers a load having a first size; and

when the STC powers a load having a second magnitude, a first resonant tank of the STC is driven at a second frequency and with the first fixed on-time to obtain the first fixed ratio of an output voltage of the STC to an input voltage of the STC, the second frequency being less than the first frequency, and the second magnitude being less than the first magnitude.

2. The method of claim 1, further comprising initiating driving of a first resonant tank circuit of the STC in response to the output voltage of the STC crossing a first threshold.

3. The method of claim 2, further comprising adjusting the first threshold such that each pulse of current through the first resonant tank circuit of the STC has a first predetermined magnitude.

4. The method of claim 2 further comprising initiating driving of a first resonant tank circuit of the STC in response to the output voltage of the STC not crossing the first threshold for a predetermined amount of time.

5. The method of claim 1, further comprising:

determining a magnitude of current flowing through the STC; and

the second frequency is controlled according to the magnitude of the current flowing through the STC.

6. The method of claim 5 further comprising controlling the second frequency such that each pulse of current through the first resonant tank of the STC has a first predetermined magnitude.

7. The method of claim 6 further comprising increasing the frequency of the first resonant tank circuit driving the STC in response to an increase in the size of a load powered by the STC.

8. The method of claim 5 further comprising increasing the frequency of the first resonant tank circuit driving the STC in response to a change in polarity of a load powered by the STC.

9. The method of claim 5 further comprising increasing the frequency of the first resonant tank circuit driving the STC in response to the magnitude of the output voltage of the STC decreasing.

10. The method of claim 5 further comprising increasing the frequency of the first resonant tank driving the STC in response to an increase in the magnitude of the output voltage of the STC.

11. The method of claim 1, further comprising:

a second resonant tank circuit that drives the STC at the first frequency when the STC powers a load of the first size; and

the second resonant tank circuit of the STC is driven at the second frequency when the STC powers a load having the second magnitude.

12. The method of claim 1, further comprising preventing the second frequency from falling below a second threshold.

13. The method of claim 1, further comprising:

driving a first resonant tank of the STC at the first frequency when the STC powers a load of the first magnitude such that each pulse of current through the resonant tank of the STC has a first duration; and

the first resonant tank of the STC is driven at the second frequency when the STC powers a load of the second magnitude such that each pulse of current through the resonant tank of the STC has the first duration.

14. The method of claim 13 wherein the first duration is a resonant half-cycle of the first resonant tank circuit of the STC.

15. The method of claim 1, wherein:

driving the first resonant tank circuit of the STC at the first frequency when the STC powers a load of the first size includes alternately driving the first resonant tank circuit with a first pair of switching devices and a second pair of switching devices; and

driving the first resonant tank circuit of the STC at the second frequency when the STC powers a load of the second size includes alternately driving the first resonant tank circuit with the first pair of switching devices and the second pair of switching devices.

16. The method of claim 15, further comprising:

controlling the first pair of switching devices and the second pair of switching devices with a first control signal and a second control signal, respectively; and

the phases of the first control signal and the second control signal are exchanged in response to a change in polarity of the load.

17. A variable switching frequency switched energy storage converter (STC), comprising:

a first resonant tank circuit;

a first pair of switching devices configured to drive the first resonant tank circuit;

a second pair of switching devices configured to drive the first resonant tank circuit; and

a controller configured to:

controlling the first and second pairs of switching devices to drive the first resonant tank circuit at a first frequency and with a first fixed on-time when the STC powers a load of a first magnitude to obtain a first fixed ratio of an output voltage of the STC to an input voltage of the STC, and

controlling the first and second pairs of switching devices to drive the first resonant tank circuit at a second frequency and with the first fixed on-time when the STC powers a load of a second magnitude to obtain the first fixed ratio of the output voltage of the STC to the input voltage of the STC, the second frequency being less than the first frequency, and the second magnitude being less than the first magnitude.

18. The STC of claim 17, wherein:

the first pair of switching devices includes a first switching device and a second switching device, each switching device being electrically coupled in series with the first resonant tank circuit; and is

The second pair of switching devices includes a third switching device and a fourth switching device, each switching device electrically coupled in series with the first resonant tank circuit.

19. The STC of claim 17, wherein the controller is further configured to control the first pair of switching devices and the second pair of switching devices to alternately drive the first resonant tank circuit using the first pair of switching devices and the second pair of switching devices.

20. The STC of claim 17, further comprising:

a second resonant tank circuit;

a third pair of switching devices configured to drive the second resonant tank circuit; and

a fourth pair of switching devices configured to drive the second resonant tank circuit;

wherein the controller is further configured to:

controlling the third pair of switching devices and the fourth pair of switching devices to drive the second resonant tank circuit of the STC at the first frequency when the STC powers a load of the first magnitude, and

controlling the third pair of switching devices and the fourth pair of switching devices to drive the second resonant tank circuit at the second frequency when the STC powers a load having the second magnitude.

Background

A switched-mode energy storage converter (STC) is a resonant converter that includes one or more switching stages, where each switching stage operates with a fixed on-time. The ratio of the output voltage to the input voltage is fixed and is determined by the number of switching stages and the connections between the switching stages. For example, in some STCs the ratio of output voltage to input voltage is fixed at fifty percent, while in some other STCs the ratio of output voltage to input voltage is fixed at twenty-five percent. The STC operates with zero current switching and therefore may be able to achieve high efficiency.

Applications of the STC include, but are not limited to, generating an unregulated intermediate voltage power rail from a high voltage power rail, where the intermediate voltage power rail powers one or more points of a load voltage regulator. For example, the STC may be used to generate an unregulated 12 volt power rail from a 48 volt power rail, and the point of load regulator may be used to generate a low voltage (e.g., less than 5 volts) power rail from the unregulated 12 volt power rail, where the low voltage power rail is used to power one or more devices that require a tightly regulated low voltage power source.

Disclosure of Invention

In a first aspect, a method for controlling a switched-mode energy storage converter (STC), the method comprising: (1) driving a first resonant tank circuit of the STC at a first frequency and with a first fixed on-time when the STC powers a load having a first size to obtain a first fixed ratio of an output voltage of the STC to an input voltage of the STC; and (2) driving a first resonant tank circuit of the STC at a second frequency and with the first fixed on-time when the STC powers a load having a second size, the second frequency being less than the first frequency, and the second size being less than the first size, to obtain the first fixed ratio of an output voltage of the STC to an input voltage of the STC.

In an embodiment of the first aspect, the method further comprises initiating driving of a first resonant tank circuit of the STC in response to the output voltage of the STC crossing a first threshold.

In another embodiment of the first aspect, the method further comprises adjusting the first threshold such that each pulse of current through the first resonant tank of the STC has a first predetermined magnitude.

In another embodiment of the first aspect, the method further comprises initiating driving of the first resonant tank circuit of the STC in response to the output voltage of the STC not crossing the first threshold for a predetermined amount of time.

In another embodiment of the first aspect, the method further comprises: (1) determining a magnitude of current flowing through the STC; and (2) controlling the second frequency according to a magnitude of a current flowing through the STC.

In another embodiment of the first aspect, the method further comprises controlling the second frequency such that each pulse of current through the first resonant tank of the STC has a first predetermined magnitude.

In another embodiment of the first aspect, the method further comprises increasing the frequency of the first resonant tank driving the STC in response to an increase in the size of a load powered by the STC.

In another embodiment of the first aspect, the method further comprises increasing a frequency of a first resonant tank driving the STC in response to a change in polarity of a load powered by the STC.

In another embodiment of the first aspect, the method further comprises increasing the frequency of the first resonant tank driving the STC in response to a decrease in the magnitude of the output voltage of the STC.

In another embodiment of the first aspect, the method further comprises increasing a frequency of a first resonant tank driving the STC in response to an increase in a magnitude of the output voltage of the STC.

In another embodiment of the first aspect, the method further comprises: (1) a second resonant tank circuit that drives the STC at the first frequency when the STC powers a load of the first size; and (2) driving a second resonant tank of the STC at the second frequency when the STC powers a load having the second size.

In another embodiment of the first aspect, the method further comprises preventing the second frequency from falling below a second threshold.

In another embodiment of the first aspect, the method further comprises: driving a first resonant tank of the STC at the first frequency when the STC powers a load of the first magnitude such that each pulse of current through the resonant tank of the STC has a first duration; and (2) driving the first resonant tank of the STC at the second frequency when the STC powers a load of the second magnitude such that each pulse of current through the resonant tank of the STC has the first duration.

In another embodiment of the first aspect, the first duration is a resonant half-cycle of the first resonant tank circuit of the STC.

In another embodiment of the first aspect, driving the first resonant tank at the first frequency when the STC powers a load of the first size includes alternately driving the first resonant tank with a first pair of switching devices and a second pair of switching devices, and driving the first resonant tank at the second frequency when the STC powers a load of the second size includes alternately driving the first resonant tank with the first pair of switching devices and the second pair of switching devices.

In another embodiment of the first aspect, the method further comprises: (1) controlling the first pair of switching devices and the second pair of switching devices with a first control signal and a second control signal, respectively; and (2) exchanging the phases of the first control signal and the second control signal in response to a change in polarity of the load.

In a second aspect, a variable switching frequency switched energy storage converter (STC) comprises: (1) a first resonant tank circuit; (2) a first pair of switching devices configured to drive the first resonant tank circuit; (3) a second pair of switching devices configured to drive the first resonant tank circuit; (4) and a controller configured to: (a) controlling the first and second pairs of switching devices to drive the first resonant tank circuit at a first frequency and with a first fixed on-time when the STC powers a load of a first size to obtain a first fixed ratio of an output voltage of the STC to an input voltage of the STC; and (b) controlling the first pair of switching devices and the second pair of switching devices to drive the first resonant tank circuit at a second frequency and with the first fixed on-time when the STC powers a load of a second magnitude to obtain the first fixed ratio of the output voltage of the STC to the input voltage of the STC, the second frequency being less than the first frequency, and the second magnitude being less than the first magnitude.

In an embodiment of the second aspect, the first pair of switching devices comprises a first switching device and a second switching device, each switching device being electrically coupled in series with the first resonant tank, and the second pair of switching devices comprises a third switching device and a fourth switching device, each switching device being electrically coupled in series with the first resonant tank.

In another embodiment of the second aspect, the controller is further configured to control the first pair of switching devices and the second pair of switching devices to alternately drive the first resonant tank using the first pair of switching devices and the second pair of switching devices.

Another embodiment of the second aspect further comprises: (1) a second resonant tank circuit; (2) a third pair of switching devices configured to drive the second resonant tank circuit; and (3) a fourth pair of switching devices configured to drive the second resonant tank circuit, wherein the controller is further configured to: (1) controlling the third pair of switching devices and the fourth pair of switching devices to drive the second resonant tank circuit of the STC at the first frequency when the STC powers a load of the first size; and (2) controlling the third pair of switching devices and the fourth pair of switching devices to drive the second resonant tank circuit at the second frequency when the STC powers a load of the second size.

Drawings

Figure 1 is a graph illustrating the efficiency as a function of load size for a hypothetical conventional STC.

Fig. 2 is a schematic diagram illustrating a variable switching frequency STC according to an embodiment.

Fig. 3 is a schematic diagram illustrating an example application of the STC of fig. 2 operating as a buck converter.

Fig. 4 is a schematic diagram illustrating one example application of the STC of fig. 2 operating as a boost converter.

Fig. 5 is a graph illustrating an example of operation of the STC of fig. 2 when the load size varies, according to an embodiment.

Fig. 6 is a graph illustrating another example of operation of the STC of fig. 2 when the load size varies, according to an embodiment.

Fig. 7 is a diagram illustrating one embodiment of a controller for the STC of fig. 2.

Fig. 8 is a diagram illustrating another embodiment of the controller of the STC of fig. 2.

Fig. 9 is a graph illustrating an example of operation of the STC of fig. 2 when the controller of fig. 8 is used, according to an embodiment.

Fig. 10 is a diagram illustrating another embodiment of the controller of the STC of fig. 2.

Fig. 11 is a schematic diagram illustrating a controller according to an embodiment that is similar to the controller of fig. 10, but includes additional circuitry for enabling the controller to rapidly increase the switching frequency in response to an increase in load magnitude.

FIG. 12 is a schematic diagram illustrating a controller according to an embodiment that is similar to the controller of FIG. 11, but includes additional circuitry for enabling the controller to rapidly increase the switching frequency in response to an over-voltage condition or an under-voltage condition.

Fig. 13 is a schematic diagram illustrating a variable switching frequency STC comprising two power stages according to an embodiment.

Fig. 14 is a schematic diagram illustrating a controller similar to that of fig. 12 but modified for use with two power stages according to an embodiment.

Fig. 15 is a flow chart illustrating a method for controlling an STC according to an embodiment.

Figure 16 is a graph illustrating an example of operation of an embodiment of the STC of figure 2 configured to exchange control signal phases in response to load polarity reversal, according to an embodiment.

Fig. 17 is a schematic diagram illustrating a controller configured to exchange control signal phases in response to load polarity reversal, according to an embodiment.

Detailed Description

While conventional STCs can achieve high efficiencies at medium load sizes, applicants have determined that conventional STCs may suffer from inefficiencies at light load sizes. Specifically, at a load magnitude where the conduction loss is approximately equal to the switching loss, the STC will reach peak efficiency. As the load size decreases, the conduction loss decreases, but the switching loss remains substantially unchanged. Therefore, efficiency at light load sizes is generally low.

For example, fig. 1 is a graph 100 illustrating efficiency as a function of load size for a hypothetical conventional STC. The horizontal axis 102 represents load size and the vertical axis 104 represents STC efficiency. Peak efficiency occurs at the load magnitude 106, where the conduction loss is approximately equal to the switching loss, and efficiency drops significantly when the load magnitude drops below the load magnitude 106.

Applicants have developed variable switching frequency STCs and related methods that can overcome, at least in part, the efficiency limitations of the light load size of conventional STCs discussed above. In particular, while conventional STCs operate at fixed switching frequencies, new STCs developed by the applicant have variable switching frequencies, e.g. the switching frequency is at least partially a function of the load size. In some embodiments, the switching frequency decreases as the load size decreases, resulting in a decrease in switching losses as the load size decreases. Thus, in certain embodiments, efficiency does not significantly decrease with decreasing load size, such that high efficiency may be achieved at light load sizes. In addition, reducing the switching frequency as the load size decreases may facilitate fast transient response by maintaining a high peak resonant tank current at light load sizes.

Figure 2 is a schematic diagram illustrating a variable switching frequency STC200, which is one embodiment of a new variable frequency STC developed by the applicant. The STC200 includes a switching stage 202 and a controller 204, and the STC200 optionally further includes a first capacitor 206 and a second capacitor 208. The first capacitor 206 is electrically coupled between the first supply node 210 and the reference node 212, and the second capacitor 208 is electrically coupled between the second supply node 214 and the reference node 212. For example, the first capacitor 206 and the second capacitor 208 provide a path for the ripple current generated by the switching stage 202.

During operation of STC200, voltage V₁A voltage V that exists between the first power supply node 210 and the reference node 212 and during operation of the STC200₂Exists between the second supply node 214 and the reference node 212. During operation of STC200, voltage V₂And voltage V₁Is approximately 0.5. In one application of the STC200 shown in fig. 3, connecting the first power supply node 210 and the reference node 212 to a power supply 302 to power the STC200, and connecting the second power supply node 214 and the reference node 212 to a load 304 powered by the STC200, causes the STC200 to operate as a buck converter, where the voltage V, V₂Is about voltage V₁50% of the size of (c). In this application, the voltage V₁Is the input voltage of STC200, and the voltage V₂Is the output voltage of STC 200. In another application of the STC200 shown in fig. 4, connecting the second power supply node 214 and the reference node 212 to a power source 402 to power the STC200, and connecting the first power supply node 210 and the reference node 212 to a load 404 powered by the STC200, causes the STC200 to operate as a boost converter, wherein the voltage V, V₁Is large in sizeAbout voltage V₂Twice the size of (a). In this application, the voltage V₁Is the output voltage of STC200, and the voltage V₂Is the input voltage of STC 200.

Referring again to fig. 2, the switching stage 202 includes a first switching device 216, a second switching device 218, a third switching device 220, a fourth switching device 222, and a resonant tank circuit 224. In certain embodiments, each of the first switching device 216, the second switching device 218, the third switching device 220, and the fourth switching device 222 includes one or more transistors, for example, Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) or Bipolar Junction Transistors (BJTs) configured to operate as switches. The first switching device 216 and the second switching device 218 together form a first pair of switching devices configured to drive the resonant tank circuit 224. The first switching device 216 is electrically coupled between the first power supply node 210 and the resonant tank 224, and the second switching device 218 is electrically coupled between the resonant tank 224 and the second power supply node 214. Thus, the resonant tank 224 is electrically coupled between the first switching device 216 and the second switching device 218, and the first switching device 216 and the second switching device 218 are each electrically coupled in series with the resonant tank 224. The resonant tank circuit 224 includes an inductor 226 and a capacitor 228 electrically coupled in series with each other. Each of the first switching device 216 and the second switching device 218 is generated by the first control signal Φ generated by the controller 204₁And (5) controlling. In particular, when the first control signal Φ₁When asserted, each of the first switching device 216 and the second switching device 218 operates in its closed or "on" state and when the first control signal Φ₁When de-asserted, each of the first switching device 216 and the second switching device 218 operates in its open or "off" state.

The third switching device 220 and the fourth switching device 222 together form a second pair of switching devices configured to drive a resonant tank circuit 224. The third switching device 220 is electrically coupled between the resonant tank 224 and the second supply node 214, and the fourth switching device 222 is electrically coupled between the resonant tank 224 and the reference node 212. Therefore, willThe resonant tank 224 is electrically coupled between the third switching device 220 and the fourth switching device 222, and the third switching device 220 and the fourth switching device 222 are each electrically coupled in series with the resonant tank 224. The third switching device 220 and the fourth switching device 222 are each generated by the second control signal Φ generated by the controller 204₂And (5) controlling. In particular, when the second control signal Φ₂When asserted, each of the third switching device 220 and the fourth switching device 222 operates in its closed or "on" state and when the second control signal Φ is asserted₂When de-asserted, each of the third switching device 220 and the fourth switching device 222 operates in its open or "off" state. The connection between the controller 204 and the switching stage 202 is not shown in fig. 2 in order to make the description clearer.

The controller 204 is formed, for example, by analog electronic circuitry and/or digital electronic circuitry. In some embodiments, the controller 204 includes a processor configured to execute instructions stored in a memory to perform one or more functions of the controller 204. Although the controller 204 is illustrated as a discrete element, the controller 204 may be combined with one or more elements without departing from the scope thereof.

The STC200 optionally further includes current sensing circuitry configured to determine a magnitude of a current flowing through the STC. For example, fig. 2 illustrates an STC200 that includes optional current sensing circuitry 230 configured to generate a current I representative of a current through a second pair of switching devices (a third switching device 220 and a fourth switching device 222)₂Current sense signal 232. The configuration of the optional current sensing circuitry 230 may be modified without departing from its scope. For example, in an alternative embodiment, the current sensing circuitry 230 is configured to generate a current I that is representative of the current through the first pair of switching devices (the first switching device 216 and the second switching device 218)₁Current sense signal 232. As another example, in another alternative embodiment, the current sensing circuitry 230 is configured to generate the respective representative currents I₁Magnitude and current I of₂Two current sense signals of magnitude.

The controller 204 is configured to generate a first control signal Φ₁And a second control signal phi₂To control the STC200 such that the first pair of switching devices (the first switching device 216 and the second switching device 218) and the second pair of switching devices (the third switching device 220 and the fourth switching device 222) alternately drive the resonant tank 224. In certain embodiments, the controller 204 is configured to generate the first control signal Φ₁And a second control signal phi₂Causing each of the first, second, third and fourth switching devices 216, 218, 220 and 222 to switch between its open and closed states to switch in a current I through the resonant tank circuit 224_LCThe voltage across the resonant tank circuit 224 is switched when it drops to zero or near zero. For example, in certain embodiments, the controller 204 monitors the current I through the resonant tank circuit 224_LCAnd in response to the current I_LCDecreases to zero and initiates a handover of the first or second pair of switching devices. In addition, the controller 204 is configured to generate a first control signal Φ₁And a second control signal phi₂The STC200 is made to have a variable switching frequency, wherein the switching frequency at a large load size is greater than the switching frequency at a light load size to improve light load efficiency.

For example, fig. 5 is a graph 500 illustrating an example of the operation of the STC200 as a function of load size. The graph 500 includes a horizontal axis 502 representing time, a vertical axis 504 representing size, and curves 506 through 516. Curves 506 and 508 represent the first control signal Φ, respectively₁And a second control signal phi₂. In the example of fig. 5, the first control signal Φ is in a logic high state₁And a second control signal phi₂Is asserted, although STC200 is not limited to control signal Φ₁And phi₂Of the polarity of (a). The curve 510 represents the size of the load, e.g., the size of the load 304 in fig. 3 or the size of the load 404 in fig. 4, that is powered by the STC 200. Curve 512 represents the current I through the resonant tank circuit 224_LCAnd curve 514 represents the current I through the first pair of switching devices (first switching device 216 and second switching device 218)₁The size of (2). Curve 516 represents the current I through the second pair of switching devices (the third switching device 220 and the fourth switching device 222)₂The size of (2).

As can be seen in the graph 500, the controller 204 generates a first control signal Φ₁And a second control signal phi₂Such that the two control signals are asserted in an alternating manner. In other words, the first control signal Φ₁Is asserted, the second control signal phi₂Is next asserted, the first control signal phi₁Next asserted, and so on. First control signal phi₁And a second control signal phi₂Each of which is of duration T_wIs asserted. Thus, the current I through the resonant tank circuit 224_LCEach pulse of (a) has a uniform duration T_pWherein the current pulse duration T_pIs the control signal duration T_wAs a function of (c). In certain embodiments, the controller 204 is configured to have a control signal duration T_wThis results in a current pulse duration T_pEqual to the resonant half cycle of the resonant tank circuit 224 to achieve zero current switching when the current I through the resonant tank circuit 224 is zero_LCIs zero or close to zero, the first control signal phi₁And a second control signal phi₂Changing their respective states.

Graph 500 illustrates a time period t_a、t_b、t_cAnd t_dAn example of operation of the STC 200. At a time period t_aDuring this time, the size of the load supplied by the STC200 is relatively large. Thus, the controller 204 generates the first control signal Φ₁And a second control signal phi₂So that the two control signals are nearly complementary, i.e., when one control signal is deasserted, the other control signal is asserted, and vice versa. However, at the first control signal Φ₁Is deasserted and the second control signal phi₂There is a small dead time between assertions and vice versa to prevent the firstThe switching device and the second pair of switching devices are simultaneously turned on. This dead time is evident from examination of the curve 512, which shows the I through the resonant tank 224 after each switching transition_LCDecreases to zero. STC200 at time period t_aHaving a switching frequency F₁Wherein the switching frequency F₁Is a time period t_aPeriod of switching T₁The reciprocal of (c). First control signal phi₁And a second control signal phi₂The common control switching stage 202 is in the time period t_aDuring the switching frequency F₁Driving the resonant tank circuit 224. In particular, when the first control signal Φ₁When asserted to drive the resonant tank circuit 224 with the first polarity, the first switching device 216 and the second switching device 218 are closed, and when the second control signal Φ is₂When asserted to drive the resonant tank circuit 224 with a second polarity opposite the first polarity, the third switching device 220 and the fourth switching device 222 are closed. Thus, during the time period t_aDuring this time, the resonant tank circuit 224 is at the switching frequency F₁The driving is alternately driven with a first polarity and a second polarity.

Load powered by STC200 for time period t_bIs smaller than during the time period t_aThe size of (2). Thus, the controller 204 generates the first control signal Φ₁And a second control signal phi₂So that during the time period t_bDuring which the switching frequency F of the STC200₂Less than during the time period t_aDuring which the switching frequency F of the STC200₁Wherein the switching frequency F₂Is a time period t_bPeriod of switching T₂The reciprocal of (c). First control signal phi₁And a second control signal phi₂The common control switching stage 202 is in the time period t_bDuring the switching frequency F₂Driving the resonant tank circuit 224. In particular, when the first control signal Φ₁When asserted to drive the resonant tank circuit 224 with the first polarity, the first switching device 216 and the second switching device 218 are closed, and when the second control signal Φ is₂Is asserted to be on the time period t_bDuring which the resonant tank circuit is driven with a second polarity opposite to the first polarity224, the third switching device 220 and the fourth switching device 222 are closed. Thus, during the time period t_bDuring this time, the resonant tank circuit 224 is at the switching frequency F₂The driving is alternately driven with a first polarity and a second polarity.

Load powered by STC200 for time period t_cIs smaller than during the time period t_aAnd t_bThe size of each of them. Thus, the controller 204 generates the first control signal Φ₁And a second control signal phi₂So that during the time period t_cDuring which the switching frequency F of the STC200₃Are respectively less than STC200 in the time period t_aAnd t_bDuring switching frequency F₁And F₂Wherein the switching frequency F₃Is a time period t_cPeriod of switching T₃The reciprocal of (c). First control signal phi₁And a second control signal phi₂The common control switching stage 202 is in the time period t_cDuring the switching frequency F₃Driving the resonant tank circuit 224. In particular, when the first control signal Φ₁When asserted to drive the resonant tank circuit 224 with the first polarity, the first switching device 216 and the second switching device 218 are closed, and when the second control signal Φ is₂Is asserted to be on the time period t_cDuring which the resonant tank circuit 224 is driven with a second polarity, opposite the first polarity, the third switching device 220 and the fourth switching device 222 are closed. Thus, during the time period t_cDuring this time, the resonant tank circuit 224 is at the switching frequency F₃The driving is alternately driven with a first polarity and a second polarity.

At a time period t_dOf the load supplied by the STC200 and during the time period t_aThe size of the load being supplied by the STC200 is the same. Thus, the STC200 is at the time period t_dWith the STC200 for the time period t_aI.e. STC200 is at time period t_dIs equal to the switching frequency F₁。

STC200 at time period t_bAnd t_cThe reduction of the switching frequency during the period reduces the switching loss of the STC200 during the time periods, thereby improving the light load efficiencyAnd (4) rate. Thus, in some embodiments, the efficiency of the STC200 does not significantly decrease when the load size decreases from a value where the switching loss is equal to the conduction loss.

In addition, STC200 is used for a time period t_bAnd t_cThe reduction in switching frequency during these periods may improve the transient response of the STC200 during these time periods. To help understand this advantage of STC200, consider first a conventional STC, where the resonant tank peak current is linearly related to the load current due to the conventional STC operating at a fixed frequency. When the STC is unloaded, the resonant tank peak current in conventional STCs drops to zero, requiring a significant amount of time for the current through the resonant tank to ramp up in response to an increase in load magnitude. Thus, conventional STCs may suffer from significant output voltage undershoot when the step load is powered from near zero.

In contrast, in certain embodiments of the STC200, the reduction in switching frequency at light load sizes enables the magnitude of the peak current through the resonant tank to be maintained at a relatively large value at light loads. Thus, the STC200 may be able to respond to a stepped load relatively quickly from near zero, thereby facilitating fast transient response and helping to minimize output voltage undershoot.

In some embodiments, the controller 204 is configured to generate the first control signal Φ₁And a second control signal phi₂To achieve a switching frequency such that the current I through the resonant tank circuit 204_LCHas a predetermined magnitude that does not change as the switching frequency of the STC200 decreases. For example, FIG. 5 illustrates at time period t_a、t_b、t_cAnd t_dDuring each period of time (c), the current I through the resonant tank circuit 204_LCEach pulse having a predetermined magnitude Δ i. When the switching frequency is reduced, the current I is reduced_LCThe pulse of (a) is kept at a constant magnitude to help prevent the efficiency of the STC200 from decreasing as the magnitude of the load powered by the STC200 decreases.

In some embodiments, the controller 204 is configured to directly control the negative of the STC200 as being powered by the STC200The switching frequency is a function of the magnitude of the load, such as by determining the magnitude of the load and decreasing the magnitude of the switching frequency as the magnitude of the load decreases. In some other embodiments, the controller 204 is configured to indirectly control the switching frequency of the STC200 as a function of the size of the load powered by the STC 200. For example, in some embodiments, the controller 204 is configured to determine a magnitude of a current flowing through the STC200 and to control a switching frequency of the STC200 at least partially in proportion to the magnitude of the current. In these embodiments, the magnitude of the current flowing through the STC200 is indicative of the magnitude of the load powered by the STC. In certain embodiments, the controller 204 determines the current I through the first pair of switching devices₁And the current I through the second pair of switching devices₂To determine the magnitude of the current flowing through the STC 200.

Output voltage of STC200 (e.g., voltage V in FIG. 3)₂Or the voltage V in FIG. 4₁) The size of the load powered by the STC200 may also be expressed because the output voltage will generally decrease as the load size increases due to conduction losses in the STC 200. Accordingly, in some embodiments, the controller 204 is configured to control the switching frequency of the STC200 in inverse proportion to the magnitude of the output voltage or in response to the magnitude of the output voltage crossing a threshold.

In some applications of the STC200, it may be desirable to prevent the switching frequency of the STC200 from falling below a minimum value, such as to help ensure electromagnetic compatibility of the STC200 with other devices. Accordingly, in some embodiments, the controller 200 is configured to prevent the switching frequency of the STC200 from falling below a predetermined threshold representing a minimum acceptable switching frequency of the STC 200.

In the example of fig. 5, the controller 204 generates the first control signal Φ₁And a second control signal phi₂Such that the two control signals are asserted 180 degrees out of phase with each other regardless of the switching frequency of the STC 200. However, the controller 204 is not limited to this configuration. For example, fig. 6 is a graph 600 illustrating another example of operation of the STC200 as a function of load size. Graph 600 includes the same curves as graph 500 of fig. 5. Shown in FIG. 6Example is similar to the example illustrated in fig. 5, except that the controller 204 is configured such that the first control signal Φ₁And a second control signal phi₂At a time period t_fAnd t_gThe periods are asserted 120 degrees out of phase with each other, wherein the size of the load powered by the STC200 is relatively small. During a time period t in which the magnitude of the load supplied by the STC200 is relatively large_eAnd t_hDuring the first control signal phi₁And a second control signal phi₂Are asserted 180 degrees out of phase with each other.

Discussed below with respect to fig. 7-12 are several possible embodiments of the controller 204. It should be understood, however, that the controller 204 is not limited to the embodiments of these figures.

Fig. 7 is a schematic diagram illustrating a controller 700. The controller 700 is one embodiment of the controller 204 and certain embodiments of the controller 700 are capable of controlling the STC200 in a manner similar to that shown by the graph 500 (fig. 5). The controller 700 includes a comparator 702, a one-shot pulse generator 704, a pulse divider 706, and a threshold voltage source 708. The controller 700 optionally further includes a minimum frequency controller 710 and an offset adjuster 712. Although fig. 7 shows each of comparator 702, one-shot pulse generator 704, pulse divider 706, threshold voltage source 708, minimum frequency controller 710, and offset adjuster 712 as separate elements, two or more of these elements may be combined without departing from their scope. The controller 700 is implemented, for example, by analog circuitry and/or digital circuitry. In some embodiments, the controller 700 includes a processor that executes instructions stored in a memory to perform one or more of the functions of the controller 700.

The inverting input of the comparator 702 is configured to receive the output voltage of the STC200, e.g., the voltage at the second supply node 214 in fig. 3 or the voltage at the first supply node 210 in fig. 4. The non-inverting input of the comparator 702 is configured to receive a first threshold 714 generated by the threshold voltage source 708. In certain embodiments, threshold voltage source 708 is configured to generate first threshold 714 such that first threshold 714 is determined as follows:

first of allThreshold 714K V_{Input device}–V_{Offset of}(equation 1)

In equation 1 above, K is the transfer function of STC200, which depends on the application of STC 200. For example, in the application of FIG. 3, K is equal to 0.5 because of the output voltage (V)₂) And an input voltage (V)₁) The ratio of (a) to (b) is 0.5. As another example, in the application of FIG. 4, K is equal to 2.0 because of the output voltage (V)₁) And an input voltage (V)₂) The ratio of (a) to (b) is 2.0. V_{Input device}Is the input voltage of STC200, e.g. V in FIG. 3₁Or V in FIG. 4₂。V_{Offset of}Is an offset selected, for example, to achieve a current I through the resonant tank circuit 204_LCDesired pulse size. In embodiments including optional offset adjuster 712, offset adjuster 712 is configured to adjust V_{Offset of}As discussed below.

The comparator 702 generates the trigger signal 716 in response to the output voltage crossing (i.e., falling below) the first threshold 714. The one-shot pulse generator 704 generates a pulse signal 718 having a predetermined duration in response to the trigger signal 716. The one-shot pulse generator 704 is configured, for example, such that the pulse signal 718 has a predetermined duration, resulting in a current pulse duration T_p(fig. 5) is equal to the resonant half-cycle of the resonant tank circuit 224.

In some embodiments, the one-shot pulse generator 704 is further configured to generate a pulse 718 in response to the trigger signal 716 not being asserted for a predetermined amount of time, thereby causing the controller 700 to initiate driving of the resonant tank 204 in response to the output voltage of the STC200 not crossing the first threshold 714 for the predetermined amount of time. The one-shot pulse generator 704 is further configured to provide a predetermined delay between successive pulse signals 718 in this case. This configuration advantageously facilitates a smooth transition between the variable switching frequency operation and the fixed switching frequency operation of the STC 200.

The pulse distributor 706 generates a first control signal Φ in response to the pulse signal 718₁And a second control signal phi₂. Specifically, the pulse distributor 706 is operativeAsserting the first control signal Φ in an alternating manner in response to receiving the pulse signal 718₁And a second control signal phi₂。

In embodiments that include the minimum frequency controller 710, the minimum frequency controller 710 cooperates with the one-shot pulse generator 704 to prevent the switching frequency of the STC200 from falling below a predetermined second threshold. Specifically, if the comparator 706 does not generate the trigger signal 716 at a rate sufficient to prevent the switching frequency from falling below the predetermined second threshold, the minimum frequency controller 710 causes the one-shot pulse generator 704 to generate the pulse signal 718 at a rate that maintains the minimum switching frequency at the predetermined second threshold.

Current I through the resonant tank circuit 204_LCIs of a magnitude of V_{Offset of}Is determined. For example, current I_LCEach pulse of (a) with V_{Offset of}Increases in size. Thus, in some embodiments including optional offset adjuster 712, offset adjuster 712 is configured to adjust V_{Offset of}Such that each pulse of current through the resonant tank circuit 224 has a predetermined magnitude, e.g., to help maintain the efficiency of the STC200 as the magnitude of the load being powered by the STC200 decreases.

In some applications of STC200, the load powered by STC200 may sometimes be negative, such that the load acts as a power source rather than a power sink. When the STC200 has a low switching frequency, a negative load may cause an undesirable rise in the output voltage in the STC 200. Accordingly, in some embodiments, the controller 204 is configured to increase the switching frequency in response to a change in polarity of the load being powered by the STC200 (e.g., in response to a change in polarity of the load from positive to negative).

For example, fig. 8 is a schematic diagram illustrating a controller 800 capable of increasing the switching frequency in response to a negative load on the STC 200. Controller 800 is an embodiment of controller 204, and controller 800 is similar to controller 700 except that controller 800 further includes a second comparator 802 and a second threshold voltage source 804. Although fig. 8 shows each of comparator 702, one-shot pulse generator 704, pulse divider 706, threshold voltage source 708, minimum frequency controller 710, offset adjuster 712, second comparator 802, and second threshold voltage source 804 as separate elements, two or more of these elements may be combined without departing from their scope. Controller 800 is implemented, for example, by analog circuitry and/or digital circuitry. In some embodiments, the controller 800 includes a processor that executes instructions stored in a memory to perform one or more of the functions of the controller 800.

The non-inverting input of the comparator 802 is configured to receive the output voltage of the STC200, e.g., the voltage at the second supply node 214 in fig. 3 or the voltage at the first supply node 210 in fig. 4. The inverting input of comparator 802 is configured to receive a second threshold 806 generated by a second threshold voltage source 804. In certain embodiments, second threshold voltage source 804 is configured to generate second threshold 806 such that second threshold 806 is determined as follows:

second threshold 806K V_{Input device}+V_{Offset 2}(equation 2)

In equation 2 above, K and V_{Input device}The same as in equation 1. V_{Offset 2}Is an offset selected, for example, to achieve a current I through the resonant tank circuit 204_LCDesired pulse size. In some embodiments, V_{Offset 2}And V of equation 1_{Offset 1}The same is true.

The comparator 802 generates a trigger signal 808 in response to the output voltage crossing (i.e., rising above) the second threshold 806. The one-shot pulse generator 704 generates a pulse signal 718 having a predetermined duration in response to the trigger signal 716 or the trigger signal 808. The one-shot pulse generator 704 and pulse distributor 706 operate in the same manner as discussed above with respect to fig. 7.

Fig. 9 is a graph 900 illustrating an example of operation of the STC200 as a function of load size when the controller 204 is embodied as the controller 800 of fig. 8. Graph 900 includes the same curves as graph 500 of fig. 5. Graph 900 illustrates a time period t_i、t_j、t_kAnd t_lAn example of operation of the STC 200. STC200 to the STC200 for the time period t of fig. 5_a、t_bAnd t_dIn the same manner as in the case of (1) during a time period t_i、t_jAnd t_lAnd (4) carrying out the operation. However, during the time period t_kThe polarity of the load powered by the STC200 changes such that the magnitude of the load is negative, as shown by curve 510 below the dashed line 902 representing zero load. Thus, the magnitude of the output voltage repeatedly rises above the second threshold 806, causing the comparator 802 to repeatedly generate the trigger signal 808, causing the STC200 to repeatedly generate the trigger signal for the time period t_kHaving a switching period T in between₁And a switching frequency F₁。

Fig. 10 is a schematic diagram illustrating the controller 1000. The controller 1000 is another embodiment of the controller 204 and certain embodiments of the controller 1000 are capable of controlling the STC200 in a manner similar to that presented by the curve 600 (fig. 6). Controller 1000 includes peak detection circuitry 1002, oscillator 1004, pulse divider 1006, and low pass filter 1008. Although fig. 10 shows each of the peak detection circuitry 1002, the oscillator 1004, the pulse divider 1006, and the low pass filter 1008 as separate elements, two or more of these elements may be combined without departing from their scope. The controller 1000 is implemented, for example, by analog circuitry and/or digital circuitry. In some embodiments, the controller 1000 includes a processor that executes instructions stored in a memory to perform one or more of the functions of the controller 1000.

The peak detection circuitry 1002 receives the current sense signal 232 from the current sensing circuitry 230, and the peak detection circuitry 1002 is configured to generate an envelope signal 1010 from the current sense signal 232. The envelope signal 1010 represents an envelope of the current sensed by the current sensing circuitry 230, e.g., the current I through the second pair of switching devices₂The envelope of (c). The low pass filter 1008 filters the envelope signal 1010 to generate a filtered envelope signal 1012, and the oscillator 1004 is configured to generate an oscillation signal 1014 having a frequency proportional to a magnitude of the filtered envelope signal 1012. The pulse distributor 1006 generates a first control signal Φ in response to the oscillation signal 1014₁And a second control signal phi₂. Specifically, the pulse distributor 1006 asserts the first control signal Φ in an alternating manner in response to the oscillation signal 1014₁And a second control signal phi₂. Thus, the controller 1000 causes the STC200 to have a current I corresponding to the current through the second pair of switching devices₂Proportional to the switching frequency. The controller 1000 may be modified to receive current sense signals other than the current sense signal 232 (e.g., current sense signals representing current flowing through different portions of the STC 200) without departing from the scope thereof.

Fig. 11 is a schematic diagram illustrating a controller 1100 that is similar to the controller 1000 of fig. 10, but further includes additional circuitry for enabling the controller 1100 to rapidly increase the switching frequency in response to an increase in the size of the load being powered by the STC 200. Specifically, controller 1100 includes the elements of controller 1100 except that (a) controller 1100 includes peak detection circuitry 1102 in place of peak detection circuit 1002, and (b) controller 1100 further includes low pass filter 1104, low pass filter 1106, threshold voltage source 1108, and comparator 1110. Although fig. 11 shows each of the peak detection circuitry 1102, the oscillator 1004, the pulse divider 1006, the low pass filter 1008, the low pass filter 1104, the low pass filter 1106, the threshold voltage source 1108, and the comparator 1110 as separate elements, two or more of these elements may be combined without departing from the scope thereof. Controller 1100 is implemented, for example, by analog circuitry and/or digital circuitry. In some embodiments, the controller 1100 includes a processor that executes instructions stored in a memory to perform one or more of the functions of the controller 1100.

The peak detection circuitry 1102 of fig. 11 is similar to the peak detection circuitry 1002 of fig. 10, but the peak detection circuitry 1102 is further configured to generate a peak envelope signal 1112 and an average envelope signal 1114 in addition to the envelope signal 1010. The peak envelope signal 1112 represents a peak of the envelope of the current sensed by the current sensing circuitry 230 and the average envelope signal 1114 represents an average of the envelope of the current sensed by the current sensing circuitry 230. The low pass filter 1104 filters the peak envelope signal 1112 to generate a filtered peak envelope signal 1116 and the low pass filter 1106 filters the average envelope signal 1114 to generate a filtered average envelope signal 1118. The filtered average envelope signal 1118 increases the voltage of the threshold voltage source 1108 to generate the comparison signal 1120. The comparator 1110 compares the filtered peak envelope signal 1116 to the comparison signal 1120, and the comparator 1110 asserts the current increase signal 1122 in response to the magnitude of the filtered peak envelope signal 1116 exceeding the comparison signal 1120.

The oscillator 1004 responds to the current increase signal 1122 by increasing the magnitude of the oscillation signal 1014, which results in an increase in the switching frequency of the STC 200. Accordingly, the peak detection circuitry 1102, the low pass filter 1104, the low pass filter 1106, the threshold voltage source 1108, and the comparator 1110 enable the controller 1100 to rapidly increase the switching frequency of the STC200 in response to an increase in the magnitude of the load powered by the STC 200. The voltage of the threshold voltage source 1108 determines the magnitude of the load increase required for the comparator 1110 to assert the current increase signal 1122. Specifically, the increased sensitivity of the comparator 1100 to loading is inversely proportional to the magnitude of the voltage generated by the threshold voltage source 1108.

The controller 1000 and the controller 1100 may be modified to increase the switching frequency in response to additional events, such as the output voltage of the STC200 increasing beyond a threshold and/or the output voltage of the STC200 falling below a threshold. For example, fig. 12 is a schematic diagram illustrating a controller 1200 that is similar to the controller 1100 of fig. 11, but further includes additional circuitry for enabling the controller 1200 to rapidly increase the switching frequency in response to an under-voltage (UV) or over-voltage (OV) condition in the STC 2000. In addition to the elements of controller 1100, controller 1200 also includes UV detection circuitry 1202 and OV detection circuitry 1204. Although fig. 12 shows each of peak detection circuitry 1102, oscillator 1004, pulse divider 1006, low pass filter 1008, low pass filter 1104, low pass filter 1106, threshold voltage source 1108, comparator 1110, UV detection circuitry 1202, and OV detection circuitry 1204 as separate elements, two or more of these elements may be combined without departing from their scope. The controller 1200 is implemented by, for example, analog circuitry and/or digital circuitry. In some embodiments, the controller 1200 includes a processor that executes instructions stored in a memory to perform one or more of the functions of the controller 1200.

The UV detection circuitry 1202 is configured to respond to the output voltage of STC200 (e.g., voltage V in fig. 3)₂And the voltage V in FIG. 4₁) Crossing the UV threshold (i.e., falling below the UV threshold) asserts the UV signal 1206. The OV detection circuitry 1204 is configured to assert the OV signal 1208 in response to the output voltage of the STC200 crossing (i.e., rising above) an OV threshold, where the OV threshold is greater than the UV threshold.

The oscillator 1004 responds to the UV signal 1206 or the OV signal 1208 by increasing the magnitude of the oscillating signal 1014, which results in an increase in the switching frequency of the STC 200. Accordingly, the controller 1200 is configured to rapidly increase the switching frequency of the STC200 in response to the UV condition or the OV condition.

The STC200 may be modified to have one or more additional power stages electrically coupled in series and/or parallel with the power stage 202. For example, fig. 13 is a schematic diagram showing an STC 1300, which is an alternative embodiment of an STC200 that includes two instances of a power stage 202, hereinafter referred to as power stage 202(a) and power stage 202 (b). The STC 1300 may be modified to include additional power levels 202 without departing from its scope. The STC 1300 additionally includes a bulk capacitor 1302, a first bulk switching device 1304, and a second bulk switching device 1306. The first and second switching devices 216 and 218 of the power stage 202(a) are electrically coupled to the first and second power supply nodes 210 and 214, respectively. The third switching device 220 of the power stage 202(a) is electrically coupled to the bulk node 1308 and the fourth switching device 222 of the power stage 202(a) is electrically coupled to the reference node 212. The first switching device 216 and the second switching device 218 of the power stage 202(b) are electrically coupled to the bulk node 1308 and the second supply node 214, respectively. The third switching device 220 and the fourth switching device 222 of the power stage 202(b) are electrically coupled to the second supply node 214 and the reference node 212, respectively.

Bulk capacitor 1302 is electrically coupled to largeCapacity node 1308, and switching node 1310. The first bulk switching device 1304 is electrically coupled between the switching node 1310 and the reference node 212, and the second bulk switching device 1306 is electrically coupled between the switching node 1310 and the second power supply node 214. The first large capacity switching device 1304 is a first control signal Φ generated by the controller 204₁And (5) controlling. In particular, when the first control signal Φ₁When asserted, the first bulk switching device 1304 operates in its closed or "on" state and when the first control signal Φ₁When de-asserted, the first mass switching device 1304 operates in its off or "off" state. The second large capacity switching device 1306 is a second control signal Φ generated by the controller 204₂And (5) controlling. In particular, when the second control signal Φ₂When asserted, the second bulk switching device 1306 operates in its closed or "on" state and when the second control signal Φ₂When de-asserted, the second mass switching device 1306 operates in its open or "off" state. The connection between the controller 204 and the switching device is not shown in fig. 13 in order to make the description clearer.

The STC 1300 optionally further includes current sensing circuitry configured to determine a magnitude of a current flowing through the STC. For example, fig. 13 shows an STC200 that includes optional current sensing circuitry 230 and current sensing circuitry 1312. The current sensing circuitry 230 is configured to generate a current sense signal 232 representative of a magnitude of current through the second pair of switching devices (the third switching device 220 and the second switching device 222) of the power stage 202(a), and the current sensing circuitry 1312 is configured to generate a current sense signal 1314 representative of a magnitude of current through the second pair of switching devices (the third switching device 220 and the second switching device 222) of the power stage 202 (b). The configuration of the optional current sensing circuitry 230 and current sensing circuitry 1312 may be modified without departing from its scope. For example, in an alternative embodiment, the current sensing circuitry 230 and 1312 is configured to generate the current sense signal 232 and the current sense signal 1314, respectively, that are representative of the magnitude of the current through the first pair of switching devices (the first switching device 216 and the second switching device 218) of its corresponding power stage 204. As another example, in another alternative embodiment, each of the current sensing circuitry 230 and 1312 is configured to generate two current sense signals that are representative of the magnitude of current through two different portions of its corresponding power stage 202.

During operation of STC 1300, voltage V₂And voltage V₁Is about 0.25. Although not required, in some embodiments of the STC 1300, the controller 204 is embodied in a manner similar to that discussed above with respect to fig. 7-12. For example, in one embodiment of the STC 1300, the controller 204 is embodied as shown in one of fig. 7 and 8. As another example, in another embodiment of the STC 1300, the controller 204 is embodied as illustrated in fig. 14. Fig. 14 is a schematic diagram illustrating a controller 1400 that is similar to the controller 1200 of fig. 12, but modified for use with two power stages 202. Specifically, controller 1400 includes the elements of controller 1200 except that (a) controller 1400 includes peak detection circuitry 1402 instead of peak detection circuitry 1202, and (b) controller 1400 further includes summing device 1404, summing device 1406, and summing device 1408. Although fig. 14 shows each of peak detection circuitry 1402, oscillator 1004, pulse divider 1006, low pass filter 1008, low pass filter 1104, low pass filter 1106, threshold voltage source 1108, comparator 1110, UV detection circuitry 1202, OV detection circuitry 1204, summing device 1404, summing device 1406, and summing device 1408 as separate elements, two or more of these elements may be combined without departing from their scope. Controller 1400 is implemented, for example, by analog circuitry and/or digital circuitry. In some embodiments, the controller 1400 includes a processor that executes instructions stored in a memory to perform one or more of the functions of the controller 1400.

The peak detection circuitry 1402 of fig. 14 is similar to the peak detection circuitry 1202 of fig. 12, but the peak detection circuitry 1402 is further configured to generate an envelope signal 1410, a peak envelope signal 1412, and an average envelope signal 1414 in addition to the envelope signal 1010, the peak envelope signal 1112, and the average envelope signal 1114. The envelope signal 1410 represents an envelope of current sensed by the current sensing circuitry 1312, e.g., an envelope of current through the second pair of switching devices of the power stage 202 (b). The peak envelope signal 1412 represents the peak of the envelope of the current sensed by the current sensing circuitry 1312 and the average envelope signal 1414 represents the average of the envelope of the current sensed by the current sensing circuitry 1312.

The summing device 1404 sums the envelope signal 1010 and the envelope signal 1410 to generate a summed envelope signal 1416, and the summing device 1406 sums the peak envelope signal 1112 and the peak envelope signal 1412 to generate a summed peak envelope signal 1418. The summing device 1408 sums the average envelope signal 1114 and the average envelope signal 1414 to generate a summed average envelope signal 1420. The low pass filter 1008 filters the summed envelope signal 1416 to generate a filtered envelope signal 1012 and the low pass filter 1104 filters the summed peak envelope signal 1418 to generate a filtered peak envelope signal 1116. The low pass filter 1106 filters the average envelope signal 1420 to generate a filtered average envelope signal 1118. The controller 1400 operates in accordance with the filtered envelope signal 1012, the filtered peak envelope signal 1116 and the filtered average envelope signal 1118, as discussed above with respect to fig. 10 and 11. Controller 1400 may be modified to support additional power stages 202 by: (a) generate an additional envelope signal, a peak envelope signal, and an average envelope signal for each additional power stage, (b) sum all envelope signals at summing device 1404, (c) sum all filtered envelope signals at summing device 1406, and (d) sum all average envelope signals at summing device 1408.

Fig. 15 is a flowchart illustrating a method for controlling the STC. In step 1502, a first resonant tank of the STC is driven at a first frequency when the STC powers a load having a first size. In one example of step 1502, when the STC200 powers a load having a medium size, the controller 800 (fig. 8) initiates driving of the resonant tank 224 such that the STC200 operates at a first switching frequency in response to the output voltage of the STC200 falling below the first threshold 714. In another example of step 1502, when the STC200 is powering a load having a medium size, the controller 1200 (fig. 12) causes the STC200 to have a switching frequency that is proportional to an envelope of current through the second pair of switching devices of the power stage 202 such that the STC200 operates at the first switching frequency.

In step 1504, the first resonant tank of the STC is driven at a second frequency when the STC powers a load having a second size, the second frequency being less than the first frequency and the second size being less than the first size. In one example of step 1402, when the STC200 powers a load having a small size, the controller 800 initiates driving of the resonant tank 224 such that the STC200 operates at the second switching frequency in response to the output voltage of the STC200 falling below the first threshold 714. In another example of step 1502, when the STC200 powers a load having a small size, the controller 1200 causes the STC200 to have a switching frequency proportional to an envelope of current through a second pair of switching devices of the power stage 202 such that the STC200 operates at the second switching frequency. Step 1502 and step 1504 are optionally repeated indefinitely, as illustrated in fig. 15.

In some embodiments, the controller 204 is further configured to: (a) detecting a first change in polarity of a load powered by the STC 200; (b) exchanging a first control signal phi in response to a detected first change of polarity of the load₁And a second control signal phi₂The phase of (d); (c) detecting a second change in polarity of a load powered by the STC 200; and (d) re-exchanging the first control signal Φ in response to a detected second change in polarity of the load₁And a second control signal phi₂The phase of (c). Applicants have found that such a phase exchange can significantly improve the transient response during load polarity reversal. In exchange for a first control signal phi₁And a second control signal phi₂In one example of the phase of (1), the first control signal Φ₁And a secondControl signal phi₂Initially with corresponding phases of zero and 180 degrees and after exchanging the phases the first control signal Φ₁And a second control signal phi₂With corresponding 180 degrees and zero degrees of phase. As a function of the exchange of the first control signal phi₁And a second control signal phi₂Another example of the phase of (b), the first control signal Φ₁And a second control signal phi₂Initially with corresponding zero and 120 degrees phases and after exchanging the phases the first control signal Φ₁And a second control signal phi₂With corresponding 120 degrees and zero degrees of phase. In certain embodiments, the controller 204 is configured to respond only to the first control signal Φ₁And a second control signal phi₂Exchange the first control signal phi when both are deasserted₁And a second control signal phi₂The phase of (c).

Fig. 16 is a graph 1600 illustrating an example of operation of an embodiment of the STC200, wherein the controller 204 is configured to exchange the first control signal Φ in response to a load polarity reversal₁And a second control signal phi₂The phase of (c). Graph 1600 includes the same curves as graph 500 of fig. 5. Graph 1600 illustrates time period t_m、t_oAnd t_pAn example of operation of the STC 200. The STC200 is in the time period t of figure 5 with the STC200_aIn the same manner as in the case of (1) during a time period t_mAnd (4) carrying out the operation. The polarity of the load powered by the STC200 changes at time 1604 such that the magnitude of the load changes over time period t_oMedium is negative as shown by curve 510 below the dashed line 1602 representing zero load. In response to a change in load polarity at time 1604, the first control signal Φ₁And a second control signal phi₂Is exchanged and thus the first control signal Φ₁There is an additional pulse 1606 shortly after time 1604. In addition, the second control signal Φ₂The pulse is skipped after time 1604. The polarity of the load powered by the STC200 again changes at time 1608, such that the magnitude of the load changes at time period t_pMedium is positive as shown by curve 510 above dashed line 1602. In response to negation at time 1608Change of polarity, first control signal phi₁And a second control signal phi₂Is exchanged again, and thus the second control signal Φ₂There is an additional pulse 1610 shortly after time 1608. In addition, the first control signal Φ₁The pulse is skipped after time 1608. Thus, the first control signal Φ₁And a second control signal phi₂At a time period t_oIs switched and the first control signal phi₁And a second control signal phi₂At a time period t_pTo return to its initial value.

FIG. 17 is a schematic diagram illustrating a controller 1700, which is one embodiment of the controller 204, configured to exchange a first control signal Φ in response to a load polarity reversal₁And a second control signal phi₂The phase of (c). However, it should be appreciated that the controller 204 may be implemented in other ways while still being configured to exchange the first control signal Φ in response to a load polarity reversal₁And a second control signal phi₂The phase of (c). Controller 1700 is similar to controller 800 of fig. 8, but: (a) pulse distributor 706 is replaced by pulse distributor 1706; (b) the trigger signal 808 is communicatively coupled to the pulse divider 1706 and to the one-shot pulse generator 704; and (c) a trigger signal 716 communicatively coupled to the pulse divider 1706 and to the one-shot pulse generator 704. The pulse distributor 1706 operates like the pulse distributor 706, but the pulse distributor 1706 is further configured to exchange the first control signal Φ in response to an assertion of the trigger signal 808 (e.g., in response to a load polarity changing from positive to negative)₁And a second control signal phi₂The phase of (c). As discussed above, the trigger signal 808 is asserted in response to an increase in the output voltage due to a change in load polarity. Additionally, the pulse distributor 1706 is further configured to exchange the first control signal Φ in response to the assertion of the trigger signal 716 (e.g., in response to the load polarity changing from negative to positive)₁And a second control signal phi₂The phase of (c). Controller 1700 otherwise operates in the same manner as controller 800.

Changes may be made in the above methods, apparatus and systems without departing from the scope of the invention. It is therefore to be noted that the subject matter contained in the above description and shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover both the generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall therebetween.