阅读说明：本技术 供电电路及用其供电的负载的状态监测方法 (Power supply circuit and method for monitoring state of load supplied by power supply circuit ) 是由 杨小华 彭胜军 于 2018-07-12 设计创作，主要内容包括：提供了一种供电电路及用其供电的负载的状态监测方法。根据本公开的实施例,供电电路包括：功率器件,其电流路径连接在第一和第二参考电压之间以在导通时在第一和第二参考电压之间形成电流通道以便向负载供电,该功率器件的控制端子接收通/断控制信号；限流电阻器,连接在所述电流通道中；箝位器件,连接在第一和第二参考电压之一与功率器件的控制端子之间,并具有预定的阈值电压,从而当所述电流通道中的电流增大而使得箝位器件两端的电压超出其预定阈值电压时,箝位器件导通并因此相对于其所连接到的参考电压而将功率器件的基极箝位,其中,功率器件和箝位器件彼此热耦合。根据本公开的实施例,可以可靠地实现电源限流/短路保护。(A power supply circuit and a method for monitoring the state of a load supplied with power by the power supply circuit are provided. According to an embodiment of the present disclosure, a power supply circuit includes: a power device having a current path connected between first and second reference voltages to form a current path between the first and second reference voltages when conducting to supply power to a load, a control terminal of the power device receiving an on/off control signal; a current limiting resistor connected in the current path; a clamping device connected between one of the first and second reference voltages and the control terminal of the power device and having a predetermined threshold voltage, such that when the current in said current path increases such that the voltage across the clamping device exceeds its predetermined threshold voltage, the clamping device conducts and thus clamps the base of the power device with respect to the reference voltage to which it is connected, wherein the power device and the clamping device are thermally coupled to each other. According to the embodiment of the present disclosure, power supply current limiting/short circuit protection can be reliably realized.)

1. A power supply circuit comprising:

a power device having a current path connected between a first reference voltage and a second reference voltage to form a current path between the first reference voltage and the second reference voltage to supply power to a load when the power device is turned on, a control terminal of the power device receiving an on/off control signal;

a current limiting resistor connected in the current path;

a clamp device connected between one of a first reference voltage and a second reference voltage and a control terminal of the power device, the clamp device having a predetermined threshold voltage such that when a current in the current path increases such that a voltage across the clamp device exceeds its predetermined threshold voltage, the clamp device conducts and thereby clamps the base of the power device relative to the reference voltage to which it is connected,

wherein the power device and the clamp device are thermally coupled to each other.

2. The power supply circuit of claim 1, wherein the clamping device and the power device are in different packages, the package of the clamping device further comprising an additional pin electrically isolated from the clamping device, the additional pin thermally coupled to the power device to enable heat transfer from the power device to an interior of the package of the clamping device.

3. A supply circuit according to claim 2, wherein the extra pin is connected to the power device, in particular to a collector thereof, by a thermally conductive wire.

4. A supply circuit as claimed in claim 2 or 3, wherein the package of the clamping device comprises two sets of diodes, wherein a first set of diodes is connected between one of the first and second reference voltages and the control terminal of the power device as the clamping device, and a second set of diodes is thermally coupled to the power device via the additional pin.

5. A supply circuit as claimed in claim 4, wherein the two sets of diodes are fabricated on the same substrate.

6. A supply circuit as claimed in claim 1, wherein the power device is a P-type device, the emitter of which is connected to a first reference voltage through the current limiting resistor, and the clamping device is connected between the first reference voltage and the base of the P-type device.

7. The power supply circuit of claim 1, further comprising:

and the current monitoring circuit monitors the current in the current channel.

8. The power supply circuit of claim 7, wherein the current monitoring circuit monitors current based on a voltage across the current limiting resistor.

9. The power supply circuit of claim 8, wherein the current monitoring circuit comprises an operational amplifier differential amplifier having differential inputs receiving the voltage across the current limiting resistor and an output outputting a voltage value proportional to the current in the current path.

10. A power supply circuit as claimed in any one of claims 7 to 9, wherein the monitoring of the current is commenced after a predetermined time has elapsed after the on/off control signal has controlled the power device to conduct.

11. The power supply circuit according to any one of claims 7 to 9, further comprising:

and the controller is used for switching off the power device through the on/off control signal when the current monitoring circuit monitors that the current is abnormal.

12. The power supply circuit according to claim 11, wherein the controller turns on the power device again by the on/off control signal after turning off the power device for a predetermined time, and monitors the current again by the current monitoring circuit, wherein the controller turns off the power supply circuit and issues an alarm when a predetermined number of cycles of turning off, turning on again, and monitoring abnormality have elapsed.

13. A supply circuit as claimed in any preceding claim, wherein the load is a fan in an inverter.

14. A frequency converter, comprising:

a fan; and

a power supply circuit for a fan, the power supply circuit as claimed in any one of claims 1 to 13.

15. A method of condition monitoring a load powered using the power supply circuit of claim 1, comprising:

monitoring the current in the current channel; and

and when the current is monitored to be abnormal, the power device is switched off through the on/off control signal.

16. The method of claim 15, further comprising:

after turning off the power device for a predetermined time, turning on the power device again by the on/off control signal and monitoring the current again by the current monitoring circuit;

and when the cycle of switching off, switching on again and monitoring abnormity is carried out for a preset number of times, the power supply circuit is switched off and an alarm is given.

Technical Field

The present disclosure relates generally to power electronics, and more particularly, to a power supply circuit with improved performance and a method of monitoring a condition of a load powered therewith.

Background

Fans are used in frequency converters. Fig. 1 shows a circuit commonly used to power fans. As shown in fig. 1, in this circuit, the control side of the fan is isolated from the power supply side by an opto-coupler OPP. On the control side, an on/off control signal for the FAN is received through the port FAN _ C. For example, the port is connected to a controller of the frequency converter, such as a single chip Microcomputer (MCU). The on/off control signal may control the switching of a switching device T1, such as a transistor, and transfer this switching state to the supply side via an opto-coupler OPP, more specifically may control the switching of a switching device T2, such as a transistor. One end of the FAN may be connected to a supply voltage and the other end may be connected to port FAN _ C1. The port FAN _ C1 selectively connects the ground voltage FGND to the FAN according to the on/off of the switching device T2. Thus, the start and stop of the fan can be controlled.

However, such circuits do not provide a detection of the fan operating condition and require manual work to determine the fan operating condition. In addition, protection and alarm cannot be provided in time when the fan is blocked or short-circuited, which may cause circuit damage.

Disclosure of Invention

In view of the above, it is an object of the present disclosure to provide a power supply circuit with improved performance and a method for monitoring a state of a load supplied with the power supply circuit.

According to an aspect of the present disclosure, there is provided a power supply circuit including: a power device having a current path connected between a first reference voltage and a second reference voltage to form a current path between the first reference voltage and the second reference voltage to supply power to a load when the power device is turned on, a control terminal of the power device receiving an on/off control signal; a current limiting resistor connected in the current path; a clamp device connected between one of a first reference voltage and a second reference voltage and a control terminal of the power device, the clamp device having a predetermined threshold voltage such that when a current in the current path increases such that a voltage across the clamp device exceeds its predetermined threshold voltage, the clamp device conducts and thereby clamps a base of the power device relative to the reference voltage to which it is connected, wherein the power device and the clamp device are thermally coupled to each other.

Since the power device and the clamp device are thermally coupled to each other, in the case where the temperature rises due to, for example, an overload or a short circuit, etc., the characteristic variation of the power device with temperature and the characteristic variation of the clamp device with temperature can be at least partially cancelled, thereby suppressing the characteristic variation of the power supply circuit, such as the variation of the maximum current.

According to embodiments of the present disclosure, the clamping device and the power device may be in different packages, and the package of the clamping device may further include an additional pin electrically isolated from the clamping device, which may be thermally coupled to the power device to enable heat transfer from the power device to the interior of the package of the clamping device. For example, the extra pin may be connected to the power device, in particular to the collector thereof, by a thermally conductive wire. Thus, the thermal coupling between the two can be achieved relatively easily.

According to an embodiment of the disclosure, the package of the clamping device may comprise two sets of diodes, wherein a first set of diodes may be connected between one of the first and second reference voltages and the control terminal of the power device as the clamping device, and a second set of diodes may be thermally coupled with the power device through the additional pin. Advantageously, the two sets of diodes may be fabricated on the same substrate. Thus, thermal coupling inside and outside the package can be achieved using redundant components within the same package.

According to an embodiment of the disclosure, the power device may be a P-type device, an emitter of which may be connected to a first reference voltage through the current limiting resistor, and the clamp device may be connected between the first reference voltage and a base of the P-type device. The P-type device is adapted to connect the positive terminal of the load to the supply voltage.

According to an embodiment of the present disclosure, the power supply circuit may further include: and the current monitoring circuit monitors the current in the current channel. For example, the current monitoring circuit monitors the current based on the voltage across the current limiting resistor. In this way, the current limiting resistor functions as a current limiting function as described above on the one hand, and also functions as a current monitoring part on the other hand.

According to an embodiment of the present disclosure, the current monitoring circuit may include an operational amplifier having a differential input terminal receiving a voltage across the current limiting resistor and an output terminal outputting a voltage value proportional to a current in the current path. By operating the differential amplifier, for example, by setting its gain (amplification factor), the voltage across the current limiting resistor (reflecting the current in the power device) can be relatively easily converted to a set range (e.g., the rated input voltage range of the controller).

According to an embodiment of the present disclosure, the monitoring of the current may be started after a predetermined time elapses after the on/off control signal controls the power device to be turned on. In this way, unstable conditions that may occur during the settling period just after the circuit begins to operate can be avoided.

According to an embodiment of the present disclosure, the power supply circuit may further include: and the controller is used for switching off the power device through the on/off control signal when the current monitoring circuit monitors that the current is abnormal. In this way, damage to the circuit due to an abnormal condition can be avoided.

According to an embodiment of the present disclosure, the controller may turn on the power device again by the on/off control signal after turning off the power device for a predetermined time, and monitor the current again by the current monitoring circuit, wherein the controller turns off the power supply circuit and issues an alarm when a predetermined number of cycles of turning off, turning on again, and monitoring an abnormality have passed. Thus, the circuit can be kept in an operating state as much as possible while avoiding a temporary abnormality.

According to an embodiment of the present disclosure, the load may be a fan in a frequency converter.

According to another aspect of the present disclosure, there is provided a frequency converter including: a fan; and a power supply circuit for the fan as described above.

According to another aspect of the present disclosure, there is provided a method for monitoring a state of a load powered by the above power supply circuit, including: monitoring the current in the current channel; and when the current is monitored to be abnormal, the power device is switched off through the on/off control signal.

According to an embodiment of the present disclosure, the method may further include: after the power device is turned off for a preset time, the power device is turned on again through the on/off control signal, and the current is monitored again through the current monitoring circuit; and when the cycle of switching off, switching on again and monitoring abnormity is carried out for a preset number of times, the power supply circuit is switched off and an alarm is given.

Drawings

The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:

FIG. 1 shows a circuit commonly used to power fans;

fig. 2 is a schematic circuit diagram illustrating a power supply circuit according to an embodiment of the present disclosure.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The words "a", "an" and "the" and the like as used herein are also intended to include the meanings of "a plurality" and "the" unless the context clearly dictates otherwise. Furthermore, the terms "comprises," "comprising," and the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.

Fig. 2 is a schematic circuit diagram illustrating a power supply circuit according to an embodiment of the present disclosure.

As shown in fig. 2, the power supply circuit 200 according to this embodiment includes a power device T02. A load, such as a fan, is powered by the power device T02. More specifically, the current path of the power device T02 may be connected between a first reference voltage VDD (e.g., 24V in a frequency converter application) and a second reference voltage GND. In this way, when the power device T02 is turned on, a current path may be formed between the first reference voltage VDD and the second reference voltage GND, and thus power may be supplied to the load at the output port VDD _ FAN. In this example, the ground voltage GND is taken as the second reference voltage, but the present disclosure is not limited thereto. In addition, the control terminal of the power device T02 may receive an on/off control signal to enable the start and stop of the power supply.

In the above current path, a current limiting resistor R5 is connected. Thus, the current flowing through the power device T02 also flows through the current limiting resistor R5. The current limiting resistor R5, in accordance with embodiments of the present disclosure, together with the clamping device described below, may achieve a current limiting effect, which will be described in further detail below.

In one example, the power device T02 may be a P-type device, more specifically, a P-type triode. In this case, a current path of the P-type transistor may be formed between an emitter and a collector of the P-type transistor, and a base thereof may serve as a control terminal of the P-type transistor. In addition, the emitter may be connected to the high reference voltage (e.g., the first reference voltage VDD) side, and the collector may be connected to the low reference voltage (the second reference voltage GND) side. The current limiting resistor R5 may be connected between the emitter and the first reference voltage VDD.

In the case of a P-type device, the logic inversion of the control signal may be achieved using the switching device T01. Specifically, for a P-type device connected as shown in figure 2, it is on when low at its base and off when high at its base. In general, the on/off control signal provided at the control terminal FAN _ C may be active high (i.e., power is desired to be supplied at this time), and the on/off control signal at the control terminal FAN _ C may be inverted by the switching device T01. In one example, the switching device T01 is an N-type triode, the collector of which is connected to the first reference voltage VDD (through resistors R3, R4, R3 being 4.7K Ω for example, and R4 being a parallel connection of 10K Ω and 22K Ω resistors for example), the emitter of which is grounded, and the base of which receives the on/off control signal (through a voltage divider network of resistors R1, R2, R1 being 4.7K Ω for example, and R2 being 10K Ω for example).

More specifically, when the on/off control signal at the control terminal FAN _ C is high level, the switching device T01 may be turned on, and thus the base potential of the power device T02 may be pulled low to turn on the power device T02. On the other hand, when the on/off control signal at the control terminal FAN _ C is a low level, the switching device T01 may be turned off, and thus the base potential of the power device T02 may be pulled up to the first reference voltage VDD so that the power device T02 is turned off.

According to the embodiment of the present disclosure, at the control terminal of the power device T02, a clamping device is also connected. In the example of fig. 2, two serially connected diodes (the diode between pins 1, 2 of the integrated component IC) are used as clamping devices. This is because when a diode is conducting, the voltage drop across it is its junction voltage. Here, for the case of a P-type power device, a clamp device may be connected between the control terminal of the power device T02 and the first reference voltage VDD to clamp the base potential with respect to the first reference voltage VDD (related to the emitter potential of the power device VDD) (thereby enabling control of the base-emitter voltage of the power device T02).

In operation, when the switching device T01 is turned on and thus the power device T02 is turned on according to the on/off control signal, when the current in the current path of the power device T02 becomes large, the emitter potential of the power device T02 will be lowered with respect to the first reference voltage VDD due to the presence of the current limiting resistor R5. As the emitter potential decreases, the base potential (the base-emitter junction voltage different from the emitter potential) of the power device T02 also decreases relative to the first reference voltage VDD. When the current becomes large to a certain extent, the base potential is causedWhen the difference from the first reference voltage VDD exceeds the threshold voltage of the clamp device, the clamp device will conduct and thus clamp the base potential as described above (clamped to about VDD-U)_ICWherein U is_ICIs the junction voltage of the clamp device at turn-on, with a typical value of about 1.25V in the case of the 2 diodes shown). In this case, if the current continues to increase, causing the emitter potential to continue to drop, the base-emitter voltage of the power device T02 will be lower than its threshold voltage, causing the power device T02 to turn off. That is, there is a maximum allowable output current as shown below:

I_max≤(U_IC–U_{be_T02})/R，

wherein, U_{be_T02}The base-emitter junction voltage of the power device T02, typically about 0.65V; r is the resistance of the current limiting resistor R5. For example, in the case where R is 2.75 Ω, I_maxIs typically around 218 mA.

It should be noted here that the current limiting resistor R5 may be provided according to practical circumstances. For example, a current limiting resistor of a certain resistance value may be realized by a parallel circuit of a plurality of resistors. In one example, a 2.75 Ω current limiting resistor may be implemented with 8 22 Ω resistors in parallel.

When the load current is less than I_maxAt this time, the power device T02 may be in a saturation state, and thus a voltage drop (collector-emitter voltage difference V) across the power device T02_ce) Can be small and its power consumption and junction temperature can be kept within the nominal range.

When the external load current exceeds the maximum allowable output current I_maxWhile, the voltage drop V of the power device T02_ceCan be equal to VDD-I_max×R_loadWherein R is_loadIs a load resistor. When R is_loadWhen reduced, the voltage drop V across the power device T02_ceIs increased so that the power device T02 can be in an amplified state. According to power P ═ I_max×V_ceIt can be seen that the power device T02 follows R_loadDecreasing and increasing power consumption, resulting in increased junction temperature. So that the base-emitter junction voltage U of the power device T02_{be_T02}Will be reduced, for example, to about 2 mV/deg.C. If the U of the clamp device is present_ICIf the maximum allowable output current I is kept constant, the maximum allowable output current I is obtained according to the formula_maxWill increase. Thus, the junction temperature rise of the power device T02 may further rise, forming a vicious circle.

To avoid such vicious circle, according to an embodiment of the present disclosure, the clamp device and the power device T02 are thermally coupled to each other. Thus, as the power device T02 heats up, the clamp device will also heat up, which may affect the clamp voltage U of the clamp device_IC. For example, in the case where the clamping device is a diode, the temperature rise will affect the junction characteristics of the clamping device, particularly the junction voltage. Here, the clamping voltage U of the clamping device_ICThe trend of the change along with the temperature can be related to the junction voltage U of the power device T02_{be_T02}The trend is the same with temperature, in this example, both decrease with increasing temperature. E.g. U_ICThe rate of decrease that can increase with temperature can be about 4 mV/deg.C. In this way, the junction temperature rise of the power device T02 can be counteracted to enable the maximum allowable output current I_maxAn increased influence.

The thermal coupling between the clamp device and the power device T02 may be accomplished in a variety of ways. For example, they may be disposed close to each other, and a heat conducting mechanism such as a heat conducting paste or the like may be disposed therebetween. If the clamp device and the power device T02 are included in separate packages, thermal coupling to each other may be accomplished through pins or heat sinks (if present) of the respective packages. For example, the package of the clamping device (i.e., the integrated component IC) may also include additional pins (e.g., pins 3, 4, 5 of the integrated component IC) that are electrically isolated from the clamping device (the diode between pins 1, 2 of the integrated component IC), through which thermal coupling with the power device T02 may be achieved to enable heat transfer from the power device T02 to the interior of the package of the integrated component IC to affect the clamping device within the package. For example, these additional pins may be connected to power device TR02, and particularly to its collector in the case of power device T02 being a P-type triode, by thermally conductive wires such as metal traces on a Printed Circuit Board (PCB) to thermally couple each other. To avoid affecting the electrical characteristics of the circuit, these extra pins and their associated devices (e.g., in the example of fig. 2, the other two diodes between the 4, 5 pins of the integrated component IC) may not form any circuit function. Advantageously, the clamping device (two diodes between pins 1, 2) and the other devices involved in the thermal coupling (two further diodes between pins 4, 5) in the integrated component IC can be fabricated on the same substrate, which facilitates the transfer of heat to the clamping device.

When the load is shorted, the voltage drop VDD (e.g., 24V) will be applied entirely across the power device T02. Since the maximum allowable output current is substantially stable as described above, the power consumption of the power device T02 at this time is about 24V × 218mA — 5.23W. Selecting the rated power consumption of the power device T02 to be greater than this value (e.g., about 20W) may enable short circuit protection (in conjunction with the current limiting shutdown function described below).

As described above, by means of the thermal coupling between the clamping device and the power device, the maximum allowable output current can be effectively stabilized in the case of overload or short circuit of the load, and device damage can be avoided as much as possible.

In addition, an inductor C (e.g., about 100nF) may be connected at the collector of the power device T02 for supply stability. In addition, at the output terminal VDD _ FAN, a protection circuit D (e.g., BAW56) may also be connected. By this protection circuit D, it is possible to clamp the voltage at the output terminal VDD _ FAN at VDD during plugging and unplugging of a load such as a FAN.

According to the embodiment of the disclosure, the current in the current channel can be monitored, and corresponding control is realized according to the monitoring result, for example, the circuit can be cut off when the overcurrent is monitored.

Various current monitoring circuits exist in the art. In the example of fig. 2, since the current in the current path also flows through the current limiting resistor R5, the current monitoring can then be converted into a monitoring of the voltage drop across the current limiting resistor R5. An example of such a current monitoring circuit (in fact a voltage sensing circuit that monitors the voltage drop across the current limiting resistor R5) is shown in dashed box in fig. 2. A typical amplification circuit based on an operational differential amplifier C, shown in dashed line in fig. 2, amplifies the voltage received at the input. The details of the amplifying circuit will not be described here. Exemplary values of the respective resistors and capacitors are shown in the figure, but the present disclosure is not limited thereto.

At the output port FAN _ I of the current monitoring circuit, the obtained voltage U is:

U＝VREF-I*R*G，

where VREF is the reference voltage connected at the non-inverting input of the operational differential amplifier C, I is the current in the current channel, R is the resistance of the current limiting resistor R5, and G is the gain of the amplification circuit (G is 100K Ω/(33K Ω +3.3K Ω) ≈ 2.755, set according to the example in fig. 2). This voltage U can be fed to a controller (e.g. an MCU in a frequency converter) in order to achieve a corresponding protection, for example by switching off the circuit by means of an on/off control signal.

Thus, the normal range of the voltage U can be determined according to the current range when the load is operating normally. When the monitored voltage U exceeds the normal range, it can be determined that the current in the current path exceeds the normal range.

For example, taking a fan as an example, assuming that the rated parameter of the fan is 100mA/24V, the current after locked-rotor self-protection is <20mA, and the half-locked-rotor current is >130 mA. The fan is assumed to operate normally at a current of 30-130 mA. The normal range of voltage U is 1.59V-0.84V when VREF is 1.82V, R is 2.75 Ω and G is 2.755. Voltage U outside this range may indicate a fan abnormality.

According to an embodiment of the present disclosure, the current monitoring (reading of the voltage U) may be started after the power supply circuit is turned on for a certain time (for example, 1 second) according to the on/off control signal. If the voltage U is within the normal range (e.g., 1.59V-0.84V), the load is judged to be operating normally. If it is detected that the voltage U is out of the normal range for a certain time (for example, 2 seconds), it may be determined that the load operates abnormally, the power supply of the power supply circuit 200 may be directly cut off, and an alarm may be issued to the outside. Alternatively, the power supply may be switched off for a certain time (e.g., 5 seconds), then switched on again by the on/off control signal, and the current monitored after a certain time (e.g., 1 second). The above process may be repeated several times. If the current is monitored to be normal, power supply can be continued; if the current is detected to be abnormal, the power supply circuit 200 can be completely cut off and an alarm can be given to the outside.

Although the fan used in the inverter is described above as an example, the present disclosure is not limited thereto. The power supply circuit of the present disclosure may be used for other different types of loads.

The embodiments of the present disclosure have been described above. However, these examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although the embodiments are described separately above, this does not mean that the measures in the embodiments cannot be used in advantageous combination. The scope of the disclosure is defined by the appended claims and equivalents thereof. Various alternatives and modifications can be devised by those skilled in the art without departing from the scope of the present disclosure, and such alternatives and modifications are intended to be within the scope of the present disclosure.