Power converter and its control circuit and control method

Abstract

This invention relates to a power converter and its control circuit and method. The power converter includes a first power switch and a second power switch, which are connected in series to form a bridge arm. The control circuit includes: a first control unit that generates a first compensation signal based on a feedback signal, using the midpoint of the bridge arm as a first reference ground; and a second control unit that generates a first control signal and a second control signal based on the first compensation signal, using the ground terminal of the bridge arm as a second reference ground; wherein the first control signal is used to control the first power switch, and the second control signal is used to control the second power switch.

Description

Technical Field

[0001] This invention relates to power electronics technology, and more specifically, to a power converter and its control circuit and control method. Background Technology

[0002] Figure 1 This is a schematic diagram of the circuit structure of an existing power converter. (Reference) Figure 1 As shown, the existing power converter is a charge pump type half-bridge resonant driver. The primary side of this power converter is a half-bridge inverter circuit. AC power is input after rectification by rectifier circuit 10. Capacitor Cr is a resonant capacitor, and inductor Lr is a resonant inductor. Rectifier circuit 10, capacitors Cboost and Cbus, diode D1, capacitor Cr, and inductor Lr constitute a charge pump type PFC. Switches Q1 and Q2 are connected in series to form bridge arm 11. Switches Q1 and Q2 alternately turn on and off, thereby generating a high-frequency AC signal on the primary side of the half-bridge inverter circuit, which is transmitted to the secondary side via transformer T1. On the secondary side of transformer T1, the high-frequency AC signal is rectified by rectifier circuit 12, filtered by capacitor Co, and then supplies power to the LED load.

[0003] The conventional half-bridge control circuit 13 uses the ground terminal COM2 of bridge arm 11 as a reference ground. It generates a compensation signal Vcomp by comparing the current feedback signal Vsense with the first reference signal Vref1, and then generates half-bridge control signals VGH and VGL via the control signal generation circuit 132. The half-bridge control signals VGH and VGL use the ground terminal COM2 of bridge arm 11 as a reference ground. The conventional half-bridge drive circuit 133 includes a level conversion circuit 133a, a first drive circuit 133b, and a second drive circuit 133c. The level conversion circuit 133a receives the half-bridge control signal VGH and converts it into intermediate signals ON and OFF, with the midpoint COM1 of bridge arm 11 as a reference ground. The first drive circuit 133b generates a drive signal DRH based on the intermediate signals ON and OFF. The drive signal DRH uses COM1 as a reference ground and is used to drive the switching transistor Q1 to turn on and off. The second drive circuit 133c generates a drive signal DRL based on the half-bridge control signal VGL. The drive signal DRL uses COM2 as a reference ground and is used to drive the switching transistor Q2 to turn on and off.

[0004] Continue to refer to Figure 1 As shown, in the prior art, when the conventional half-bridge drive circuit 133 is used to drive the half-bridge, the conventional half-bridge control circuit 13 must use the ground terminal COM2 of the bridge arm 11 in the half-bridge circuit as the reference ground, which causes the current feedback signal Vsense to not reflect the complete resonant current information, thereby reducing the control accuracy of the LED drive current. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a power converter and its control circuit and control method, which can improve the current control accuracy while being compatible with traditional half-bridge drive technology.

[0006] In a first aspect, the present invention provides a control circuit for a power converter, the power converter including a first power switch and a second power switch, the first power switch and the second power switch being connected in series to form a bridge arm, the control circuit including: a first control unit, which generates a first compensation signal based on a feedback signal, using the midpoint of the bridge arm as a first reference ground; and a second control unit, which generates a first control signal and a second control signal based on the first compensation signal, using the ground terminal of the bridge arm as a second reference ground; wherein the first control signal is used to control the first power switch, and the second control signal is used to control the second power switch.

[0007] Furthermore, the first control unit includes: an error amplification module, which generates the first compensation signal based on the feedback signal and the first reference signal, wherein the first compensation signal uses the first reference ground as the reference ground.

[0008] Furthermore, the second control unit includes: a signal transmission circuit that generates a second compensation signal based on the first compensation signal, the second compensation signal taking the second reference ground as the reference ground; and a control signal generation circuit that generates the first control signal and the second control signal based on the second compensation signal.

[0009] Specifically, when the second control signal is valid, the signal transmission circuit makes the second compensation signal follow the first compensation signal, and when the second control signal is invalid, it makes the second compensation signal remain at the first compensation signal just before the second control signal changes from valid to invalid.

[0010] Preferably, the signal transmission circuit includes: a switch having a first terminal, a second terminal, and a control terminal, the first terminal being used to receive the first compensation signal, the control terminal being used to receive the second control signal; and a first capacitor, the first terminal of the first capacitor being connected to the second terminal of the switch to output the second compensation signal, and the second terminal of the first capacitor being connected to the second reference ground.

[0011] Furthermore, the control circuit also includes a half-bridge drive circuit, which generates a first drive signal according to the first control signal and a second drive signal according to the second control signal. The first drive signal is used to control the on and off of the first power switch, and the second drive signal is used to control the on and off of the second power switch.

[0012] Furthermore, when the first control signal is valid, the first drive signal is valid and the first power switch is turned on; when the first control signal is invalid, the first drive signal is invalid and the first power switch is turned off; when the second control signal is valid, the second drive signal is valid and the second power switch is turned on; when the second control signal is invalid, the second drive signal is invalid and the second power switch is turned off.

[0013] Furthermore, the feedback signal is used to characterize the resonant current of the power converter.

[0014] Secondly, the present invention provides a power converter, comprising: a bridge arm, including a first power switch and a second power switch connected in series, wherein an intermediate node between the first power switch and the second power switch serves as the midpoint of the bridge arm and a first reference ground, and a second power terminal of the second power switch is connected to the ground of the power converter, the ground of the power converter serving as a second reference ground; a control circuit, including a first control unit and a second control unit, wherein the first control unit generates a first compensation signal based on a feedback signal, using the first reference ground as a reference ground; and the second control unit generates a first control signal and a second control signal based on the first compensation signal, using the second reference ground as a reference ground; and a resonant circuit, including a second capacitor and an inductor connected in series; wherein the first control signal is used to control the first power switch, and the second control signal is used to control the second power switch.

[0015] Furthermore, the power converter further includes: a first rectifier circuit, the positive output terminal of which is connected to the first power terminal of the first power switch, and the negative output terminal of which is connected to the second capacitor; the first rectifier circuit is adapted to connect to an AC power supply; a transformer, including a primary winding and a secondary winding, the same-named terminal of the primary winding being connected to the first control unit of the control circuit, and the opposite-named terminal of the primary winding being connected to the inductor; a current sampling circuit connected between the first reference ground and the same-named terminal of the primary winding; a second rectifier circuit connected between the same-named terminal and the opposite-named terminal of the secondary winding; and an output capacitor, the first and second terminals of which are respectively connected to the positive and negative output terminals of the second rectifier circuit, and the output capacitor is adapted to connect to a load.

[0016] Furthermore, the power converter also includes a charge pump circuit, which includes: a diode, the anode of which is connected to the second reference ground and the cathode of which is connected to the negative output terminal of the first rectifier circuit; a third capacitor connected between the positive and negative output terminals of the first rectifier circuit; and a fourth capacitor, the first terminal of which is connected to the positive output terminal of the first rectifier circuit and the second terminal of which is connected to the anode of the diode; wherein the charge pump circuit and the resonant circuit are used for power factor correction.

[0017] Furthermore, the first control unit includes: an error amplification module, which generates the first compensation signal based on the feedback signal and the first reference signal, wherein the first compensation signal uses the first reference ground as the reference ground.

[0018] Furthermore, the second control unit includes: a signal transmission circuit that generates a second compensation signal based on the first compensation signal, the second compensation signal taking the second reference ground as the reference ground; and a control signal generation circuit that generates the first control signal and the second control signal based on the second compensation signal.

[0019] Preferably, when the second control signal is valid, the signal transmission circuit causes the second compensation signal to follow the first compensation signal, and when the second control signal is invalid, the second compensation signal is kept at the level of the first compensation signal just before the second control signal changes from valid to invalid.

[0020] Preferably, the signal transmission circuit includes: a switch having a first terminal, a second terminal, and a control terminal, the first terminal being used to receive the first compensation signal, the control terminal being used to receive the second control signal; and a first capacitor, the first terminal of the first capacitor being connected to the second terminal of the switch to output the second compensation signal, and the second terminal of the first capacitor being connected to the second reference ground.

[0021] Furthermore, the control circuit also includes a half-bridge drive circuit, which generates a first drive signal according to the first control signal and a second drive signal according to the second control signal. The first drive signal is used to control the on and off of the first power switch, and the second drive signal is used to control the on and off of the second power switch.

[0022] Specifically, when the first control signal is valid, the first drive signal is valid and the first power switch is turned on; when the first control signal is invalid, the first drive signal is invalid and the first power switch is turned off; when the second control signal is valid, the second drive signal is valid and the second power switch is turned on; when the second control signal is invalid, the second drive signal is invalid and the second power switch is turned off.

[0023] Furthermore, the feedback signal is used to characterize the resonant current of the power converter.

[0024] Thirdly, the present invention provides a control method for a power converter, the power converter including a first power switch and a second power switch, the first power switch and the second power switch being connected in series to form a bridge arm, the method including the following steps: generating a first compensation signal based on a feedback signal; generating a first control signal and a second control signal based on the first compensation signal; and controlling the first power switch based on the first control signal and controlling the second power switch based on the second control signal; wherein the first compensation signal uses the midpoint of the bridge arm as a first reference ground, and the first control signal and the second control signal use the grounding terminal of the bridge arm as a second reference ground.

[0025] Furthermore, the method further includes: generating a second compensation signal based on the first compensation signal; and generating the first control signal and the second control signal based on the second compensation signal respectively; wherein the second compensation signal uses the grounding terminal of the bridge arm as a second reference ground.

[0026] Specifically, when the second control signal is valid, the second compensation signal follows the first compensation signal; when the second control signal is invalid, the second compensation signal remains at the level of the first compensation signal just before the second control signal changes from valid to invalid.

[0027] Furthermore, the method further includes: generating a first drive signal according to the first control signal; and generating a second drive signal according to the second control signal; the first drive signal is used to control the on and off of the first power switch, and the second drive signal is used to control the on and off of the second power switch; wherein, when the first control signal is valid, the first drive signal is valid and the first power switch is turned on; when the first control signal is invalid, the first drive signal is invalid and the first power switch is turned off; when the second control signal is valid, the second drive signal is valid and the second power switch is turned on; when the second control signal is invalid, the second drive signal is invalid and the second power switch is turned off.

[0028] Furthermore, the feedback signal is used to characterize the resonant current of the power converter.

[0029] Because the present invention adopts the above technical solution, it has the following significant advantages compared with the prior art:

[0030] Based on the traditional half-bridge control circuit, the technical solution of this invention divides the control circuit into a first control unit, a second control unit, and a half-bridge drive circuit. By setting the first control unit with the midpoint of the bridge arm of the power converter as the first reference ground, the first control unit can acquire a feedback signal and generate a first compensation signal based on the feedback signal. Simultaneously, by transmitting the first compensation signal to the second control unit, the second control unit can generate a first control signal and a second control signal based on the first compensation signal, and drive the bridge arm of the power converter via the half-bridge drive circuit, thereby effectively improving the current control accuracy. Furthermore, the control circuit of this invention is compatible with traditional half-bridge technology, simplifies the process platform, and reduces process difficulty and production costs. Attached Figure Description

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0032] Figure 1 This is a schematic diagram of the circuit structure of an existing power converter;

[0033] Figure 2 This is a schematic diagram of the circuit structure of a power converter according to an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the circuit structure of a control circuit for a power converter according to an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the signal waveform of a power converter according to an embodiment of the present invention;

[0036] Figure 5 This is a flowchart of a control method according to an embodiment of the present invention. Detailed Implementation

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0038] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the invention is not limited to the specific embodiments disclosed below.

[0039] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0040] In detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure will be partially enlarged and not to scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0041] For ease of description, spatial relation terms such as “below,” “below,” “lower than,” “below,” “above,” “upper,” etc., may be used herein to describe the relationship of an element or feature shown in the accompanying drawings to other elements or features. It will be understood that these spatial relation terms are intended to include orientations of the device in use or operation other than those depicted in the accompanying drawings. For example, if the device in the accompanying drawings is flipped, the orientation of an element described as “below,” “below,” or “below” to other elements or features will change to “above” said other elements or features. Thus, the exemplary terms “below” and “below” can encompass both upward and downward directions. The device may also have other orientations (rotated 90 degrees or in other orientations), and therefore the spatial relation descriptors used herein should be interpreted accordingly. Furthermore, it will be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or there may be one or more layers in between.

[0042] In the context of this application, the structure described above the second feature may include embodiments in which the first and second features are formed in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0043] It should be understood that when a component is referred to as "on another component," "connected to another component," "coupled to another component," or "in contact with another component," it can be directly on, connected to, coupled to, or in contact with that other component, or there may be an intervening component. In contrast, when a component is referred to as "directly on another component," "directly connected to," "directly coupled to," or "directly in contact with" another component, there is no intervening component. Similarly, when a first component is referred to as "electrically contacting" or "electrically coupled to" a second component, there is an electrical path between the first and second components that allows current to flow. This electrical path may include capacitors, coupled inductors, and / or other components that allow current to flow, even if there is no direct contact between the conductive components.

[0044] The following embodiments of the present invention provide a control circuit for a power converter, which can improve current control accuracy while being compatible with traditional half-bridge drive technology.

[0045] Figure 2 This is a schematic diagram of the circuit structure of a power converter according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the circuit structure of a control circuit for a power converter according to an embodiment of the present invention. The following is in conjunction with... Figure 2 and Figure 3 The structure of the control circuit will be described below. It is understood that the following description is merely exemplary, and those skilled in the art can make various changes without departing from the spirit of the invention.

[0046] refer to Figure 2 As shown, the power converter 2 includes a first rectifier circuit 10, a charge pump circuit 11, a resonant circuit 12, a control circuit 20, a bridge arm 13, a current sampling circuit, a transformer T1, a second rectifier circuit 14, and an output capacitor Co.

[0047] The first rectifier circuit 10 is connected between the AC power supply AC and the charge pump circuit 11. It is used to rectify the AC input voltage to obtain a DC input voltage and output it to the charge pump circuit 11.

[0048] The charge pump circuit 11 is connected to the opposite terminal of the primary winding Np of transformer T1 through the resonant circuit 12. The charge pump circuit 11 and the resonant circuit 12 work together to achieve power factor correction.

[0049] A current sampling circuit is connected between the corresponding terminal of the primary winding Np of transformer T1 and the midpoint of bridge arm 13 to sample the resonant current and obtain the feedback signal Vsense. Preferably, the current sampling circuit can be a sampling resistor Rcs.

[0050] Bridge arm 13 can be a half-bridge inverter circuit, including a first power switch Q1 and a second power switch Q2. Control circuit 20 is connected to the current sampling circuit and bridge arm 13 respectively, and is used to generate a first drive signal DRH and a second drive signal DRL according to the feedback signal Vsense, and to control the conduction and turn-off of the first power switch Q1 and the second power switch Q2 respectively.

[0051] The second rectifier circuit 14 is connected to the secondary winding Ns of transformer T1. It rectifies the AC output voltage of the secondary winding Ns and generates a DC output voltage after filtering by the output capacitor Co, which then supplies power to the load Load.

[0052] Specifically, the charge pump circuit 11 includes a diode D1, a third capacitor Cboost, and a fourth capacitor Cbus. The cathode of diode D1 is connected to the negative output terminal of rectifier circuit 11, and the anode of diode D1 is connected to the second terminal of the fourth capacitor Cbus, serving as the ground of power converter 2. The third capacitor Cboost is connected in parallel between the positive and negative output terminals of the first rectifier circuit 10. The first terminal of the fourth capacitor Cbus is connected to the positive output terminal of the first rectifier circuit 10 and is connected to the first power terminal of the first power switch Q1. The second power terminal of the first power switch Q1 is connected to the first power terminal of the second power switch Q2. The intermediate node between the first power switch Q1 and the second power switch Q2 is the midpoint of bridge arm 13, and the second power terminal of the second power switch Q2 is grounded.

[0053] The resonant circuit 12 includes a second capacitor Cr and an inductor Lr. The second capacitor Cr and the inductor Lr are connected in series between the cathode of diode D1 and the opposite terminal of the primary winding Np of transformer T1. It is easy to understand that the combination of charge pump circuit 11 and resonant circuit 12 is only one implementation method for achieving power factor correction; other circuit structures capable of achieving the above function can also be applied to this embodiment.

[0054] The control circuit 20 includes a first control unit 201 and a second control unit 202. The first control unit 201 uses the midpoint of the bridge arm 13 as a first reference ground COM1 to acquire a feedback signal Vsense. Preferably, the feedback signal Vsense is used to characterize the resonant current of the power converter 2. The first control unit 201 is configured to generate a first compensation signal Vcomp1 based on the feedback signal Vsense. The second control unit 202 uses the ground terminal of the bridge arm 13 as a second reference ground COM2 and is configured to generate a first control signal VGH and a second control signal VGL based on the first compensation signal Vsense. The first control signal VGH is used to control the first power switch Q1, and the second control signal VGL is used to control the second power switch Q2.

[0055] It should be understood that the first power switch Q1 and the second power switch Q2 may include, but are not limited to, electrically controlled switching elements such as metal-oxide-semiconductor transistors (MOSFETs), bipolar transistors (BJTs), and insulated-gate transistors (IGBTs).

[0056] In some embodiments, the control circuit 20 further includes a half-bridge drive circuit 203. The half-bridge drive circuit 203 is configured to generate a first drive signal DRH based on a first control signal VGH and a second drive signal DRL based on a second control signal VGL. The first drive signal DRH uses a first reference ground COM1 as a reference ground and is used to control the on and off states of the first power switch Q1; the second drive signal DRL uses a second reference ground COM2 as a reference ground and is used to control the on and off states of the second power switch Q2.

[0057] Specifically, when the first control signal VGH is valid, the first drive signal DRH is valid, and the first power switch Q1 is turned on; when the first control signal VGH is invalid, the first drive signal DRH is invalid, and the first power switch Q1 is turned off. When the second control signal VGL is valid, the second drive signal DRL is valid, and the second power switch Q2 is turned on; when the second control signal VGL is invalid, the second drive signal DRL is invalid, and the second power switch Q2 is turned off.

[0058] In one embodiment of the present invention, the first control unit 201 includes an error amplification module. The error amplification module generates a first compensation signal Vcomp1 based on the feedback signal Vsense and the first reference signal Vref1. The first compensation signal Vcomp1 uses the first reference ground COM1 as its reference ground.

[0059] Preferred, Reference Figure 3 As shown, the error amplification module may include an error amplifier 201a and a follower 201b. The error amplifier 201a is configured to generate a first compensation signal Vcomp1 based on the feedback signal Vsense and the first reference signal Vref1. The follower 201b is configured to follow the output of the first compensation signal Vcomp1.

[0060] In some embodiments, the first reference signal Vref1 can be used to characterize the expected value of the resonant current of the power converter 2, but the present invention is not limited thereto.

[0061] refer to Figure 3As shown, in one embodiment of the present invention, the second control unit 202 includes a signal transmission circuit 202a and a control signal generation circuit 202b. The signal transmission circuit 202a is configured to generate a second compensation signal Vcomp2 based on a first compensation signal Vcomp1. The control signal generation circuit 202b is configured to generate a first control signal VGH and a second control signal VGL based on the second compensation signal Vcomp2. The second compensation signal Vcomp2 uses a second reference ground COM2 as its reference ground.

[0062] Preferably, the signal transmission circuit 202a can also be configured to, when the second control signal VGL is valid, make the second compensation signal Vcomp2 follow the first compensation signal Vcomp1, and when the second control signal VGL is invalid, make the second compensation signal Vcomp2 remain at the first compensation signal Vcomp1 at the moment before the second control signal VGL changes from valid to invalid.

[0063] In one embodiment of the present invention, the signal transmission circuit 202a includes a switch S1 and a first capacitor Chold. The switch S1 has a first terminal, a second terminal, and a control terminal. The first terminal of the switch S1 is used to receive a first compensation signal Vcomp1, and the control terminal of the switch S1 is used to receive a second control signal VGL. The first terminal of the first capacitor Chold is connected to the second terminal of the switch S1 to output a second compensation signal Vcomp2, and the second terminal of the first capacitor Chold is connected to a second reference ground COM2.

[0064] When the second control signal VGL is valid, switch S1 is turned on, and the second compensation signal Vcomp2 follows the first compensation signal Vcomp1; when the second control signal VGL is invalid, switch S1 is turned off, and the second compensation signal Vcomp2 remains at the level of the first compensation signal Vcomp1 just before the second control signal VGL changes from valid to invalid.

[0065] For example, the control signal generation circuit 202b can generate a first control signal VGH and a second control signal VGL using a PWM (Pulse Width Modulation) modulation method. In other examples, modulation methods such as PFM (Pulse Frequency Modulation) can also be used. It should be understood that those skilled in the art can select the specific modulation method of the control signal generation circuit 202b according to actual needs, and the present invention is not limited thereto.

[0066] Figure 4 This is a schematic diagram of the signal waveform of a power converter according to an embodiment of the present invention. (Reference) Figure 4 As shown, for Figure 2In the power converter 2 shown, the first control signal VGH, the second control signal VGL, the first drive signal DRH, and the second drive signal DRL are all active high and inactive low. The first control signal VGH is completely synchronized with the first drive signal DRH, and the second control signal VGL is completely synchronized with the second drive signal DRL.

[0067] Continue to refer to Figure 4 As shown, between times t0 and t1, the second control signal VGL is active, and the second compensation signal Vcomp2 completely follows the first compensation signal Vcomp1. Between times t1 and t2, the second control signal VGL is inactive, and the second compensation signal Vcomp2 remains at the level of the first compensation signal Vcomp1 just before the second control signal VGL changes from active to inactive.

[0068] The control circuit 20 of the present invention sets the first control unit 201 with the midpoint of the bridge arm 13 of the power converter 2 as the first reference ground COM1. The first control unit 201 can acquire the feedback signal Vsense and generate a first compensation signal Vcomp1 based on the feedback signal Vsense. At the same time, by transmitting the first compensation signal Vcomp1 to the second control unit 202, the second control unit 202 can generate a first control signal VGH and a second control signal VGL based on the first compensation signal Vcomp1, and drive the bridge arm 13 of the power converter 2 through the half-bridge drive circuit 203, thereby effectively improving the current control accuracy.

[0069] It should be noted that those skilled in the art can make appropriate adjustments to the specific structure of the power converter 2 according to actual needs, and the present invention is not limited thereto.

[0070] The above embodiments of the present invention provide a power converter and its control circuit, which can improve the current control accuracy while being compatible with traditional half-bridge drive technology.

[0071] Another aspect of the present invention proposes a control method for a power converter, which can improve the current control accuracy of the power converter.

[0072] Figure 5 This is a flowchart of a control method according to an embodiment of the present invention. The following is in conjunction with… Figure 2 , Figure 3 and Figure 5 The steps of this control method are described below. It is understood that the following description is merely exemplary, and those skilled in the art can make various changes without departing from the spirit of the invention.

[0073] refer to Figure 2As shown, the power converter 2 includes a first power switch Q1 and a second power switch Q2, which are connected in series to form a bridge arm 13. The above control method includes the following steps:

[0074] Step S100: Generate a first compensation signal based on the feedback signal.

[0075] refer to Figure 2 As shown, a first compensation signal Vcomp1 is generated based on the feedback signal Vsense. The first compensation signal Vsense uses the midpoint of bridge arm 13 as the first reference ground COM1.

[0076] Preferably, the feedback signal Vsense can be used to characterize the resonant current of the power converter 2.

[0077] refer to Figure 3 As shown, in one embodiment of the present invention, the first control unit 201 includes an error amplifier 201a and a follower 201b. The error amplifier 201a is configured to generate a first compensation signal Vcomp1 based on a feedback signal Vsense and a first reference signal Vref1. The follower 201b is configured to follow the output of the first compensation signal Vcomp1.

[0078] In some embodiments, the first reference signal Vref1 can be used to characterize the expected value of the resonant current of the power converter 2, but the present invention is not limited thereto.

[0079] In step S200, a first control signal and a second control signal are generated based on the first compensation signal.

[0080] refer to Figure 2 As shown, a first control signal VGH and a second control signal VGL are generated based on the first compensation signal Vsense. The first control signal VGH and the second control signal VGL use the ground terminal of bridge arm 13 as the second reference ground COM2.

[0081] In one embodiment of the present invention, the control method further includes: generating a second compensation signal Vcomp2 based on a first compensation signal Vcomp1, and generating a first control signal VGH and a second control signal VGL based on the second compensation signal Vcomp2. The second compensation signal Vcomp2 uses the ground terminal of bridge arm 13 as the second reference ground COM2.

[0082] For example, refer to Figure 3As shown, the second control unit 202 includes a signal transmission circuit 202a and a control signal generation circuit 202b. The signal transmission circuit 202a is configured to generate a second compensation signal Vcomp2 based on a first compensation signal Vcomp1. The control signal generation circuit 202b is configured to generate a first control signal VGH and a second control signal VGL based on the second compensation signal Vcomp2. The second compensation signal Vcomp2 uses the ground terminal of bridge arm 13 as a second reference ground COM2.

[0083] In one embodiment of the present invention, when the second control signal VGL is valid, the second compensation signal Vcomp2 follows the first compensation signal Vcomp1; when the second control signal VGL is invalid, the second compensation signal Vcomp2 remains at the level of the first compensation signal Vcomp1 just before the second control signal VGL changes from valid to invalid.

[0084] For example, refer to Figure 3 As shown, the signal transmission circuit 202a can also be configured to, when the second control signal VGL is valid, make the second compensation signal Vcomp2 follow the first compensation signal Vcomp1, and when the second control signal VGL is invalid, make the second compensation signal Vcomp2 remain at the first compensation signal Vcomp1 at the moment before the second control signal VGL changes from valid to invalid.

[0085] The control signal generation circuit 202b can generate a first control signal VGH and a second control signal VGL using modulation methods such as PWM or PFM. It should be understood that those skilled in the art can select the specific modulation method for the control signal generation circuit 202b according to actual needs, and this invention is not limited thereto.

[0086] Step S300: Control the first power switch according to the first control signal and control the second power switch according to the second control signal.

[0087] refer to Figure 2 As shown, the first power switch Q1 is controlled according to the first control signal VGH, and the first power switch Q2 is controlled according to the second control signal VGL.

[0088] In one embodiment of the present invention, the control method further includes: generating a first drive signal DRH according to a first control signal VGH; and generating a second drive signal DRL according to a second control signal VGL. The first drive signal DRH is used to control the on and off of the first power switch Q1, and the second drive signal DRL is used to control the on and off of the second power switch Q2.

[0089] Specifically, when the first control signal VGH is valid, the first drive signal DRH is valid, and the first power switch Q1 is turned on; when the first control signal VGH is invalid, the first drive signal DRH is invalid, and the first power switch Q1 is turned off; when the second control signal VGL is valid, the second drive signal DRL is valid, and the second power switch Q2 is turned on; when the second control signal VGL is invalid, the second drive signal DRL is invalid, and the second power switch Q2 is turned off.

[0090] For example, refer to Figure 3 As shown, the control circuit 20 also includes a half-bridge drive circuit 203. The half-bridge drive circuit 203 is configured to generate a first drive signal DRH based on a first control signal VGH and a second drive signal DRL based on a second control signal VGL. The first drive signal DRH is used to control the on / off state of the first power switch Q1, and the second drive signal DRL is used to control the on / off state of the second power switch Q2.

[0091] The above uses Figure 5 The flowchart shown illustrates the steps / operations performed by the control method according to embodiments of this application. It should be understood that these steps / operations are not necessarily performed precisely in sequence. Instead, various steps / operations can be processed in reverse order or simultaneously. Furthermore, other steps / operations may be added to these processes, or one or more steps / operations may be removed from these processes.

[0092] It should be noted that the above control methods can be used in, for example... Figure 2 The power converter 2 shown is implemented in the form of a variation thereof. However, those skilled in the art can make corresponding adjustments to the specific structure and arrangement of the power converter 2 according to actual needs, and the present invention is not limited thereto.

[0093] Other implementation details of the control method in this embodiment can be found in [reference]. Figures 2 to 4 The described embodiments will not be elaborated further here. Those skilled in the art can make appropriate adjustments to the priority order of the specific operation steps of the control method according to actual needs, and the present invention is not limited thereto.

[0094] The above embodiments of the present invention provide a control method for a power converter, which can improve the current control accuracy of the power converter.

[0095] It is understood that although some inventive embodiments that are currently considered useful have been discussed through various examples in the above disclosure, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover any combination of modifications and equivalents that conform to the substance and scope of the embodiments of this application.

[0096] It should be understood that the embodiments described above are merely illustrative. The embodiments described herein can be implemented in hardware, software, firmware, middleware, microcode, or any combination thereof. For hardware implementation, the processing unit can be implemented within one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and / or other electronic units designed to perform the functions described herein, or combinations thereof.

[0097] The basic concepts have been described above. Obviously, for those skilled in the art, the above disclosure is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, and therefore remain within the spirit and scope of the exemplary embodiments of this application.

[0098] Furthermore, this application uses specific terms to describe embodiments of the application. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0099] Furthermore, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this application are not intended to limit the order of the processes and methods of this application. Although the foregoing disclosure has discussed some currently considered useful embodiments of the invention through various examples, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments; rather, the claims are intended to cover all modifications and equivalent combinations that conform to the substance and scope of the embodiments of this application. For example, while the system components described above can be implemented using hardware devices, they can also be implemented solely through software solutions, such as installing the described system on existing servers or mobile devices.

[0100] Similarly, it should be noted that, in order to simplify the description of the present application and thus aid in the understanding of one or more embodiments, the foregoing description of the embodiments of the present application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, this disclosure method does not imply that the subject matter of the present application requires more features than those mentioned in the claims. In fact, the embodiments contain fewer features than all the features of the single embodiments disclosed above.

[0101] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of scope in some embodiments of this application are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0102] Although the present invention has been described with reference to specific embodiments, those skilled in the art should recognize that the above embodiments are merely illustrative of the invention, and various equivalent changes or substitutions can be made without departing from the spirit of the invention. Therefore, any changes or modifications to the above embodiments within the essential spirit of the invention will fall within the scope of the claims of this application.

Claims

1. A control circuit for a power converter, the power converter comprising a first power switch and a second power switch, the first power switch and the second power switch being connected in series to form a bridge arm, the control circuit comprising: The first control unit takes the midpoint of the bridge arm as the first reference ground, acquires a feedback signal, and generates a first compensation signal based on the feedback signal. as well as The second control unit includes: a signal transmission circuit that generates a second compensation signal based on the first compensation signal, the second compensation signal using a second reference ground as the reference ground; and a control signal generation circuit that generates a first control signal and a second control signal based on the second compensation signal, using the grounding terminal of the bridge arm as the second reference ground. The signal transmission circuit wherein, when the second control signal is valid, the second compensation signal follows the first compensation signal, and when the second control signal is invalid, the second compensation signal is kept at the first compensation signal at the moment before the second control signal changes from valid to invalid; Wherein, the first control signal is used to control the first power switch, and the second control signal is used to control the second power switch.

2. The control circuit as described in claim 1, characterized in that, The first control unit includes: The error amplification module generates the first compensation signal based on the feedback signal and the first reference signal, wherein the first compensation signal uses the first reference ground as the reference ground.

3. The control circuit as described in claim 1, characterized in that, The signal transmission circuit includes: A switch having a first terminal, a second terminal, and a control terminal, wherein the first terminal is used to receive a first compensation signal, and the control terminal is used to receive a second control signal; and A first capacitor, the first end of which is connected to the second end of the switch to output the second compensation signal, and the second end of which is connected to the second reference ground.

4. The control circuit as described in claim 1, characterized in that, The control circuit further includes a half-bridge drive circuit, which generates a first drive signal according to the first control signal and a second drive signal according to the second control signal. The first drive signal is used to control the turn-on and turn-off of the first power switch, and the second drive signal is used to control the turn-on and turn-off of the second power switch.

5. The control circuit as described in claim 4, characterized in that, When the first control signal is valid, the first drive signal is valid and the first power switch is turned on; when the first control signal is invalid, the first drive signal is invalid and the first power switch is turned off. When the second control signal is valid, the second drive signal is valid and the second power switch is turned on; when the second control signal is invalid, the second drive signal is invalid and the second power switch is turned off.

6. The control circuit as described in claim 1, characterized in that, The feedback signal is used to characterize the resonant current of the power converter.

7. A power converter, comprising: The bridge arm includes a first power switch and a second power switch connected in series. The intermediate node between the first power switch and the second power switch serves as the midpoint of the bridge arm and a first reference ground. The second power terminal of the second power switch is connected to the ground of the power converter, and the ground of the power converter serves as a second reference ground. The control circuit includes a first control unit and a second control unit. The first control unit takes the first reference ground as the reference ground, acquires a feedback signal, and generates a first compensation signal based on the feedback signal. The second control unit includes: a signal transmission circuit that generates a second compensation signal based on the first compensation signal, the second compensation signal using the second reference ground as a reference ground; and a control signal generation circuit that generates a first control signal and a second control signal based on the second compensation signal, using the ground terminal of the bridge arm as the second reference ground, wherein the signal transmission circuit, when the second control signal is valid, causes the second compensation signal to follow the first compensation signal, and when the second control signal is invalid, causes the second compensation signal to remain at the level of the first compensation signal just before the second control signal changes from valid to invalid; and A resonant circuit includes a second capacitor and an inductor connected in series; Wherein, the first control signal is used to control the first power switch, and the second control signal is used to control the second power switch.

8. The power converter as described in claim 7, characterized in that, The power converter also includes: A first rectifier circuit, wherein the positive output terminal of the first rectifier circuit is connected to the first power terminal of the first power switch transistor, and the negative output terminal of the first rectifier circuit is connected to the second capacitor, and the first rectifier circuit is adapted to be connected to an AC power supply. A transformer includes a primary winding and a secondary winding. The same-named terminals of the primary winding are connected to the first control unit of the control circuit, and the opposite-named terminals of the primary winding are connected to the inductor. A current sampling circuit is connected between the first reference ground and the corresponding terminal of the primary winding; A second rectifier circuit is connected between the same-named and opposite-named terminals of the secondary winding; and An output capacitor, the first and second ends of which are respectively connected to the positive and negative output terminals of the second rectifier circuit, and the output capacitor is suitable for connecting to a load.

9. The power converter as described in claim 8, characterized in that, The power converter further includes a charge pump circuit, which comprises: A diode, wherein the anode of the diode is connected to the second reference ground, and the cathode of the diode is connected to the negative output terminal of the first rectifier circuit; The third capacitor is connected between the positive and negative output terminals of the first rectifier circuit; and The fourth capacitor has its first terminal connected to the positive output terminal of the first rectifier circuit, and its second terminal connected to the anode of the diode. The charge pump circuit and the resonant circuit are used for power factor correction.

10. The power converter according to any one of claims 7-9, characterized in that, The first control unit includes: The error amplification module generates the first compensation signal based on the feedback signal and the first reference signal, wherein the first compensation signal uses the first reference ground as the reference ground.

11. The power converter as described in claim 7, characterized in that, The signal transmission circuit includes: A switch having a first terminal, a second terminal, and a control terminal, wherein the first terminal is used to receive a first compensation signal, and the control terminal is used to receive a second control signal; and A first capacitor, the first end of which is connected to the second end of the switch to output the second compensation signal, and the second end of which is connected to the second reference ground.

12. The power converter according to any one of claims 7-9, characterized in that, The control circuit further includes a half-bridge drive circuit, which generates a first drive signal according to the first control signal and a second drive signal according to the second control signal. The first drive signal is used to control the turn-on and turn-off of the first power switch, and the second drive signal is used to control the turn-on and turn-off of the second power switch.

13. The power converter as described in claim 12, characterized in that, When the first control signal is valid, the first drive signal is valid and the first power switch is turned on; when the first control signal is invalid, the first drive signal is invalid and the first power switch is turned off. When the second control signal is valid, the second drive signal is valid and the second power switch is turned on; when the second control signal is invalid, the second drive signal is invalid and the second power switch is turned off.

14. The power converter according to any one of claims 7-9, characterized in that, The feedback signal is used to characterize the resonant current of the power converter.

15. A control method for a power converter, applied to the power converter as described in any one of claims 7-14, the power converter comprising a first power switch and a second power switch, the first power switch and the second power switch being connected in series to form a bridge arm, the method comprising the following steps: Acquire a feedback signal and generate a first compensation signal based on the feedback signal; A first control signal and a second control signal are generated based on the first compensation signal; as well as The first power switch is controlled according to the first control signal and the second power switch is controlled according to the second control signal; The first compensation signal uses the midpoint of the bridge arm as the first reference ground, and the first control signal and the second control signal use the grounding terminal of the bridge arm as the second reference ground.

16. The control method as described in claim 15, characterized in that, The method further includes: A second compensation signal is generated based on the first compensation signal; and The first control signal and the second control signal are generated according to the second compensation signal, respectively. The second compensation signal uses the grounding terminal of the bridge arm as the second reference ground.

17. The control method as described in claim 16, characterized in that, When the second control signal is valid, the second compensation signal follows the first compensation signal; when the second control signal is invalid, the second compensation signal remains at the level of the first compensation signal just before the second control signal changes from valid to invalid.

18. The control method as described in claim 15, characterized in that, The method further includes: A first drive signal is generated according to the first control signal; and A second drive signal is generated based on the second control signal; The first drive signal is used to control the turn-on and turn-off of the first power switch, and the second drive signal is used to control the turn-on and turn-off of the second power switch. Specifically, when the first control signal is valid, the first drive signal is valid and the first power switch is turned on; when the first control signal is invalid, the first drive signal is invalid and the first power switch is turned off; when the second control signal is valid, the second drive signal is valid and the second power switch is turned on; when the second control signal is invalid, the second drive signal is invalid and the second power switch is turned off.

19. The control method as described in claim 15, characterized in that, The feedback signal is used to characterize the resonant current of the power converter.

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