阅读说明：本技术 一种高增益变换电路及其控制方法 (High-gain conversion circuit and control method thereof ) 是由 贾鹏宇 于 2019-10-28 设计创作，主要内容包括：本发明提供了一种高增益变换电路及其控制方法,变换电路包括：一次侧电路,用于提供输入电流；变压器,所述变压器的一次侧线圈与所述一次侧电路的输出端连接,所述变压器的二次侧线圈连接于二次侧电路的输入端；二次侧电路,包括谐振电路,第二开关电路和滤波电路,所述谐振电路的输入端与所述变压器的二次侧耦合,所述谐振电路的输出端与所述第二开关电路连接,所述第二开关电路的输出端与负载连接。根据本发明的变换电路及其控制方法,减少了一次侧的开关数,使一次侧功率损耗控制在很小的范围内,同时在二次侧新增谐振回路,大大降低了谐振电容器的电流应力,减小了等效串联电阻引起的功率损耗。(The invention provides a high-gain conversion circuit and a control method thereof, wherein the conversion circuit comprises: a primary side circuit for providing an input current; a primary side coil of the transformer is connected with the output end of the primary side circuit, and a secondary side coil of the transformer is connected with the input end of the secondary side circuit; and the secondary side circuit comprises a resonant circuit, a second switch circuit and a filter circuit, wherein the input end of the resonant circuit is coupled with the secondary side of the transformer, the output end of the resonant circuit is connected with the second switch circuit, and the output end of the second switch circuit is connected with a load. According to the conversion circuit and the control method thereof, the switching number of the primary side is reduced, the power loss of the primary side is controlled within a small range, and meanwhile, a resonant circuit is additionally arranged on the secondary side, so that the current stress of a resonant capacitor is greatly reduced, and the power loss caused by equivalent series resistance is reduced.)

1. A high-gain conversion circuit, comprising:

a primary side circuit for providing an input current;

a primary side coil of the transformer is connected with the output end of the primary side circuit, and a secondary side coil of the transformer is connected with the input end of the secondary side circuit;

and the secondary side circuit comprises a resonant circuit, a second switch circuit and a filter circuit, wherein the input end of the resonant circuit is coupled with the secondary side of the transformer, the output end of the resonant circuit is connected with the second switch circuit, and the output end of the second switch circuit is connected with a load.

2. The converter circuit according to claim 1, wherein the primary-side circuit includes:

a first switch, a first input terminal of which is connected to a first terminal of a primary coil of the transformer;

a positive input end of the input circuit is connected with a second end of the primary side coil of the transformer, and the input current comprises a current source;

a second switch, a second input terminal of which is connected to a third terminal of the primary coil of the transformer;

the first output terminal of the first switch, the negative input terminal of the input circuit and the second output terminal of the second switch are connected to ground.

3. The converter circuit of claim 2, wherein the transformer comprises: the primary side coil of the transformer comprises a first end, a second end and a third end, the secondary side coil of the transformer comprises a fourth end and a fifth end, and the turn ratio of the transformer is 1:1: N.

4. The conversion circuit of claim 3, wherein the resonant circuit comprises: one end of the inductor is connected with the fourth end of the secondary side coil of the transformer, and the other end of the inductor is connected to one end of the first capacitor and one end of the second capacitor respectively;

the second switching circuit includes:

the first diode branch comprises a first diode and a second diode which are connected in series, the anode of the first diode is connected with the cathode of the second diode, and one end of the first diode branch comprises the cathode of the first diode;

the second diode branch comprises a third diode and a fourth diode which are connected in series, the anode of the third diode is connected with the cathode of the fourth diode, and one end of the third diode branch comprises the cathode of the third diode;

the first capacitor branch comprises a third capacitor and a fourth capacitor which are connected in series;

one end of the first diode branch and one end of the second diode branch are connected to the anode of a fifth diode, and the cathode of the fifth diode is connected with one end of the first capacitor branch;

the other end of the first diode branch and the other end of the second diode branch are connected to the cathode of a sixth diode, and the anode of the sixth diode is connected with the other end of the first capacitor branch;

the first capacitor is connected in parallel with the first diode, and the second capacitor is connected in parallel with the second diode.

5. The conversion circuit according to any one of claims 1 to 4, further comprising a controller that controls the first switching circuit.

6. The method of controlling a converter circuit according to claim 4, wherein the method comprises:

during a first time period, the first switch is closed and the second switch is open, the resonant circuit resonates, and a resonant current passes through a first resonant path including the second capacitor and the fourth diode, and/or through a second resonant path including the first capacitor, the fifth diode, and the third capacitor.

7. The method of claim 6, further comprising: during a second time period, the first switch is closed and the second switch is open, the resonant circuit stops resonating, the resonant current decreases, the first diode and the fifth diode are closed, and the second diode, the third diode and the fourth diode are open.

8. The method of claim 7, further comprising: in a third time period, the first switch is closed and the second switch is opened, the resonant current is reduced to 0, and the first diode, the second diode, the third diode, the fourth diode and the fifth diode are all opened.

9. The method of claim 8, wherein the method comprises:

during a fourth time period, the first switch is open and the second switch is closed, the resonant circuit resonates, and a resonant current passes through a third resonant path including the first capacitor and the third diode, and/or through a fourth resonant path including the second capacitor, a sixth diode, and a fourth capacitor.

10. The method of claim 9, wherein the method comprises:

in a fifth time period, the first switch is opened and the second switch is closed, the resonant circuit stops resonating, the resonant current decreases, the second diode and the sixth diode are closed, and the first diode, the third diode and the fourth diode are opened.

Technical Field

The present invention relates to the field of circuits, and more particularly to conversion circuits.

Background

With the rapid development of power supply technology, in many applications such as fuel cell electric vehicles, photovoltaic power generation, etc., a boost converter circuit is one of the indispensable key technologies. Due to the limitation of parasitic parameters when the duty cycle is very large, the primary side input current in a conventional boost converter accounts for a large portion of the total power loss. Meanwhile, high voltage stress of the secondary side element is also a big problem.

Therefore, the conventional technology has the problems of large number of primary side switches, large power loss and high secondary side voltage stress.

Disclosure of Invention

The present invention has been made in view of the above problems. The invention provides a high-gain conversion circuit and a control method thereof, which aim to solve the problems in the prior art.

According to a first aspect of the present invention, there is provided a high-gain conversion circuit comprising:

a primary side circuit for providing an input current;

a primary side coil of the transformer is connected with the output end of the primary side circuit, and a secondary side coil of the transformer is connected with the input end of the secondary side circuit;

and the secondary side circuit comprises a resonant circuit, a second switch circuit and a filter circuit, wherein the input end of the resonant circuit is coupled with the secondary side of the transformer, the output end of the resonant circuit is connected with the second switch circuit, and the output end of the second switch circuit is connected with a load.

According to a second aspect of the present invention, there is provided a control method of the conversion circuit according to the first aspect, comprising:

during a first time period, the first switch is closed and the second switch is open, the resonant circuit resonates, and a resonant current passes through a first resonant path including the second capacitor and the fourth diode, and/or through a second resonant path including the first capacitor, the fifth diode, and the third capacitor.

According to the high-gain conversion circuit and the control method thereof, the push-pull structure is adopted at the primary side, so that the number of active switches is reduced, and the power loss of the primary side is controlled in a small range; a resonance loop is additionally arranged on the secondary side, so that the current stress of the resonance capacitor is greatly reduced, and the power loss caused by equivalent series resistance is reduced.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail embodiments of the present invention with reference to the attached drawings. The accompanying drawings are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings, like reference numbers generally represent like parts or steps.

Fig. 1 is a schematic diagram of a conversion circuit provided according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a translation circuit during a first time period according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a translation circuit during a second time period according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a transform circuit during a third time period according to an embodiment of the invention;

FIG. 5 is a schematic diagram of a transform circuit during a fourth time period according to an embodiment of the invention;

FIG. 6 is a schematic diagram of a transform circuit during a fifth time period according to an embodiment of the invention;

FIG. 7 is a schematic diagram of a translation circuit during a sixth time period according to an embodiment of the present invention;

fig. 8 is a diagram illustrating exemplary waveforms in each mode of steady-state operation of the inverter circuit according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, exemplary embodiments according to the present invention will be described in detail below with reference to the accompanying drawings. It is to be understood that the described embodiments are merely a subset of embodiments of the invention and not all embodiments of the invention, with the understanding that the invention is not limited to the example embodiments described herein. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the invention described herein without inventive step, shall fall within the scope of protection of the invention.

Referring to fig. 1, fig. 1 illustrates a conversion circuit 10 according to an embodiment of the present invention, where the conversion circuit 10 may include:

a primary side circuit 11 for supplying an input current;

a transformer 12, a primary side coil of which is connected with an output end of the primary side circuit, and a secondary side coil of which is connected with an input end of the secondary side circuit;

and the secondary side circuit 13 comprises a resonant circuit, a second switch circuit and a filter circuit, wherein the input end of the resonant circuit is coupled with the secondary side of the transformer, the output end of the resonant circuit is connected with the second switch circuit, and the output end of the second switch circuit is connected with a load.

Alternatively, the primary-side circuit 11 includes:

a first switch S1, a first input terminal of the first switch S1 being connected to a first terminal of the primary winding of the transformer 12;

an input circuit Vg, a positive input end of which is connected to a second end of the primary coil of the transformer 12, the input circuit Vg including a current source;

a second switch S2, a second input terminal of the second switch S2 being connected to a third terminal of the primary winding of the transformer 12;

the first output terminal of the first switch S1, the negative input terminal of the input circuit Vg, and the second output terminal of the second switch S2 are connected to ground.

Optionally, the transformer 12 comprises: the primary side coil of the transformer 12 comprises the first end, the second end and the third end, the secondary side coil of the transformer 12 comprises the fourth end and the fifth end, and the turn ratio of the transformer is 1:1: N.

Optionally, the resonant circuit comprises: a first capacitor C1, a second capacitor C2 and an inductor L, one end of the inductor L is connected with the fourth end of the secondary side coil of the transformer 12, and the other end of the inductor L is connected to one end of the first capacitor C1 and one end of the second capacitor C2 respectively.

Optionally, the second switching circuit comprises:

a first diode branch comprising a first diode D1 and a second diode D2 connected in series, the anode of the first diode D1 being connected to the cathode of the second diode D2, one end of the first diode branch comprising the cathode of the first diode D1;

a second diode branch comprising a third diode D3 and a fourth diode D4 connected in series, the anode of the third diode D3 being connected to the cathode of the fourth diode D4, one end of the third diode branch comprising the cathode of the third diode D3;

a first capacitive branch comprising a third capacitor C3 and a fourth capacitor C4 connected in series;

one end of the first diode branch and one end of the second diode branch are connected to the anode of a fifth diode D5, and the cathode of the fifth diode D5 is connected to one end of the first capacitor branch;

the other end of the first diode branch and the other end of the second diode branch are connected to the cathode of a sixth diode D6, and the anode of the sixth diode D6 is connected to the other end of the first capacitor branch;

the first capacitor C1 is connected in parallel with the first diode D1, and the second capacitor C2 is connected in parallel with the second diode D2.

Optionally, one end of the first capacitor C3 and one end of the fourth capacitor C4 are connected to the load.

Optionally, the conversion circuit of claim 2, wherein the first switch and the second switch comprise controllable switches. For example, an IGBT, a MOS transistor, etc.

Optionally, the conversion circuit further comprises a controller, the controller controlling the first switching circuit. It should be noted that the controller may be independent from the conversion circuit, or may be implemented in the same device as the conversion circuit, which is not limited herein.

In some embodiments, the controller may be implemented by software, hardware, firmware or a combination thereof, and may use at least one of a Circuit, a single or multiple Application Specific Integrated Circuits (ASIC), a Digital Signal Processor (DSP), a Digital Signal Processing Device (DSPD), a Programmable Logic Device (PLD), a Field Programmable Gate Array (FPGA), a Central Processing Unit (CPU), a controller, a microcontroller, and a microprocessor.

In the converter circuit 10 of the present invention shown in fig. 1, the transformer 12 is a step-up transformer, and the turns ratio of the transformer 12 is 1/1/N. Capacitors C1 and C2 serve as resonant capacitors, connected in parallel with the clamping diodes D1 and D2. The C3 and C4 capacitors are large enough to provide a low impedance path for the resonance process and also act as an output filter. Therefore, the capacitors C1 and C2 and the leakage inductor L form a resonant tank, and the load current is represented by iLoad. The switches S1 and S2 operate in opposite phases with a duty cycle of 0.5 and a switching period Ts, and each switching period has six operating modes, and the operation principle is as follows:

(1) first mode I, referring to fig. 2, fig. 2 shows a schematic diagram of a conversion circuit according to an embodiment of the present invention during a first time period. At t₀<t<t₁When t is₀Time of day, S₁Opening, S₂Closing, D₄And D₅And is simultaneously turned on. The equivalent voltage of the secondary side winding before the inductor L is NV_g. At this stage, the inductor L and the capacitor C₁And C₂Participate in the resonance process. The resonant current iL increases from zero and passes through two paths. Wherein one resonant path is formed by C₂And D₄The other resonant path consists of C₁、D₅And C₃Composition (because of C)₃Has a sufficiently low impedance, so v can be considered to be_C3Is a constant voltage source equal to V_o/2). Input current i_gAlso increases from 0 and passes through switch S₁And i_LHave the same waveform, so that the switch S₁The turn-on process of ZCS is achieved.

(2) Second mode II, referring to fig. 3, fig. 3 shows a schematic diagram of a conversion circuit according to an embodiment of the invention during a second time period. At t₁<t<t₂Within, at t₁Time, v_C2Increase to V_o/2，v_C1To 0. D₁Start of conduction, D₄Opening, D₄The reverse voltage of the diode is zeroExcept that D₄But the current decay rate is high. Resonance process at t₁The moment is suspended. At v_C3Under the action of (i), the inductive current i_LLinear decrease equal to V_o/2. Corresponding to i_D1And i_D5Current decrease rate of and i_LLikewise, the reverse recovery problem is also alleviated.

(3) Third mode III, referring to fig. 4, fig. 4 shows a schematic diagram of a conversion circuit according to an embodiment of the invention during a third time period. At t₂<t<t₃Within, at t₂Time of day, inductor current i_LFalls to zero, input current i_gAlso drops to zero. Switch S₁Still conducting but no current passes. Thus, at this stage, the input and output of the converter are decoupled, the load being fed by the output capacitor C₃And C₄Providing energy. At t₃Time of day, switch S₁Is turned off, switch S₂Is turned on. Since no current passes through S₁Switch S₁A ZCS shutdown procedure is implemented. Inductor current i_LBegins to increase in reverse, so switch S₂A ZCS turn-on process is achieved.

(4) Fourth mode IV, referring to fig. 5, fig. 5 shows a schematic diagram of a conversion circuit according to an embodiment of the present invention during a fourth time period. At t₃<t<t₄When t is₃Time of day, S₂Opening, S₁Closing, D₃And D₆And is simultaneously turned on. The equivalent voltage of the secondary side winding before the inductor L is NV_g. At this stage, the inductor L and the capacitor C₁And C₂Participate in the resonance process. The resonant current iL increases from zero and passes through two paths. Wherein one resonant path is formed by C₁And D₃The other resonant path consists of C₂、D₆And C₄Composition (because of C)₄Has a sufficiently low impedance, so v can be considered to be_C4Is a constant voltage source equal to V_o/2). Input current i_gAlso increases from 0 and passes through switch S₂And i_LHave the same waveform, so that the switch S₂The turn-on process of ZCS is achieved.

(5) Fifth mode V, referring to fig. 6, fig. 6 shows a schematic diagram of a conversion circuit according to an embodiment of the present invention during a fifth time period. At t₄<t<t₅Within, at t₄Time, v_C1Increase to V_o/2，v_C2To 0. D₂Start of conduction, D₃Opening, D₃The reverse voltage of the diode is zero, eliminating D₃But the current decay rate is high. Resonance process at t₄The moment is suspended. At v_C4Under the action of (i), the inductive current i_LLinear decrease equal to V_o/2. Corresponding to i_D2And i_D6Current decrease rate of and i_LLikewise, the reverse recovery problem is also alleviated.

(6) Sixth mode VI, referring to fig. 7, fig. 7 shows a schematic diagram of a conversion circuit according to an embodiment of the present invention during a sixth time period. At t₅<t<t₆Within, at t₅Time of day, inductor current i_LFalls to zero, input current i_gAlso drops to zero. Switch S₂Still conducting but no current passes. Thus, at this stage, the input and output of the converter are decoupled, the load being fed by the output capacitor C₃And C₄Providing energy. At t₆Time of day, switch S₂Is turned off, switch S₁Is turned on. Since no current passes through S₂Switch S₂A ZCS shutdown procedure is implemented. Inductor current i_LBegins to increase in reverse, so switch S₁A ZCS turn-on process is achieved.

According to the high-gain conversion circuit provided by the embodiment of the invention, the fourth mode IV, the fifth mode V and the modulo sixth mode VI are respectively symmetrical to the working processes of the first mode I, the second mode II and the third mode III. Referring to fig. 8, fig. 8 is a diagram illustrating exemplary waveforms in each mode of steady state operation of the inverter circuit according to an embodiment of the present invention.

Therefore, the voltage gain M and the normalized frequency fm (e.g., fs/fr) of the transform circuit 10 according to the embodiment of the present invention are obtained. It can be seen that the voltage gain M is linear with respect to fm as follows:

where M is the voltage gain, N is the transformer turn ratio of FIG. 1, C_rIs a resonant capacitor, R_LIs a load resistance, f_sTo the switching frequency, f_rAt natural resonant frequency, R₀Is a characteristic impedance; the relationships are as follows:

the conversion circuit 10 operates in a quasi-resonant state with the resonant phases in the first mode I and the fourth mode IV, and the diode freewheel phases in the second mode II and the fifth mode V and the input-output decoupling phases in the third mode III and the sixth mode VI. The corresponding constraints are:

wherein, the quality factor Q is:

in summary, according to the high-gain conversion circuit and the control method thereof in the embodiments of the invention, the conversion circuit has high gain and high efficiency. The push-pull structure is adopted at the primary side, so that the number of active switches is reduced, and the power loss of the primary side is controlled within a small range; a resonance loop is additionally arranged on the secondary side, so that the current stress of the resonance capacitor is greatly reduced, and the power loss caused by equivalent series resistance is reduced; the improved symmetrical quadruple voltage rectifier structure at the secondary side also reduces the voltage stress of the secondary side diode and the capacitor.

In the description provided herein, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments may be used in any combination.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The usage of the words first, second and third, etcetera do not indicate any ordering. These words may be interpreted as names.