Asymmetric half-bridge circuit, power supply circuit and charger

Abstract

The invention discloses an asymmetric half-bridge circuit, a power supply circuit and a charger. The asymmetric half-bridge circuit comprises a first switching tube, a second switching tube, a resonant inductor, a variable resonant module, a transformer and a control module, and the control module is connected with the first switch tube and the second switch tube, is also connected with the variable resonance module, and is used for obtaining sampling data corresponding to the variable resonance module and adjusting resonance parameters of the variable resonance module according to the sampling data. The variable resonance module with adjustable resonance parameters is arranged in the asymmetric half-bridge circuit, and in the working process of the circuit, the resonance parameters of the variable resonance module can be adjusted based on sampling data on the variable resonance module, so that the phenomenon that the asymmetric half-bridge circuit works in an under-resonance state due to device tolerance is prevented; the problems of small resonance period and low power supply efficiency caused by device tolerance can be solved, the conduction time of the secondary side is ensured to be long enough, and the power supply efficiency is compliant.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and in particular to an asymmetric half-bridge circuit, a power supply circuit, and a charger. Background Art

[0002] Currently, asymmetric half-bridge circuits are widely used in PD power supplies, such as Figure 1 As shown, an asymmetric half-bridge circuit typically includes a first switching tube Q1, a second switching tube Q2, a resonant inductor L1, a resonant capacitor C, and a transformer T1 connected in series. When the asymmetric half-bridge circuit is in operation, it can control Q1 and Q2 to alternately conduct, causing the resonant inductor L1, the resonant capacitor C, and the excitation inductor LM on the primary winding of the transformer T to resonate, thereby transmitting energy to the secondary winding of the transformer. When Q1 is on and Q2 is off, energy is stored in the resonant cavity. When Q2 is on and Q1 is off, energy is transferred from the primary winding of the transformer to the secondary winding. The secondary freewheeling diode D1 is turned on, and the excitation current on the primary winding of the transformer decreases linearly according to the slope of NVout / LM. When the excitation current is equal to the resonant current on the resonant capacitor C and the resonant inductor L1, the freewheeling diode D1 is turned off.

[0003] During the primary-secondary energy transfer process, the conduction time of the secondary freewheeling diode D1 is affected by the resonant frequency of the resonant inductor L1 and the resonant capacitor C, as well as the demagnetization speed of LM. If the conduction time of the freewheeling diode D1 is short and the turn-off time is too fast, the peak current on the secondary winding of the transformer T1 must be relatively large to achieve sufficient energy transmission in a short time, which will cause the effective value of the current to increase, and then lead to increased line loss of the transformer T1 and switch tube loss, resulting in poor efficiency of the power supply.

[0004] When an asymmetric half-bridge circuit is actually used in a switching power supply circuit, the actual hardware parameters may differ from the calibrated parameters due to the "tolerance" of the resonant inductor L1 and resonant capacitor C used. For example, the resonant inductor L1 is usually the leakage inductance of transformer T1 or a discrete inductor. Because the inductance of the magnetic component is usually controlled by the size of the air gap in the magnetic column, and the processing tolerance of the air gap exists, the actual inductance varies between samples, and the tolerance of the inductance is generally about ±7%. When the inductance of the resonant inductor L1 and the capacitance of the resonant capacitor C are both smaller than the calibrated values, the actual resonant period will be smaller than the theoretical value, and the freewheeling diode D1 will turn off too quickly, resulting in poor power supply efficiency. Summary of the Invention

[0005] Embodiments of the present invention provide an asymmetric half-bridge circuit, a power supply circuit, and a charger to solve the problem of low power efficiency of the asymmetric half-bridge circuit caused by tolerances between the inductor and capacitor components in the asymmetric half-bridge circuit and the calibrated values.

[0006] An embodiment of the present invention provides an asymmetrical half-bridge circuit, which includes a first switching tube, a second switching tube, a resonant inductor, a variable resonant module, a transformer, and a control module; The first switching tube and the second switching tube are connected in series between a signal input end and the ground. A connection node between the first switching tube and the second switching tube is connected to a first end of a primary winding of the transformer through the resonant inductor, and a second end of the primary winding of the transformer is grounded through the variable resonant module; The control module is connected to the first switching tube and the second switching tube, and is also connected to the variable resonant module, and is configured to alternately control one of the first switching tube and the second switching tube to conduct and the other to turn off, obtain sampling data corresponding to the variable resonant module, and adjust a resonant parameter of the variable resonant module according to the sampling data.

[0007] Preferably, the control module includes a control chip and a sampling unit; A first control end of the control chip is connected to the first switching tube, and a second control end of the control chip is connected to the second switching tube, and is configured to alternately control one of the first switching tube and the second switching tube to conduct and the other to turn off; A first end of the sampling unit is connected to the variable resonant module, and a second end of the sampling unit is connected to a signal receiving end of the control chip, and is configured to collect sampling data corresponding to the variable resonant module; A third control end of the control chip is connected to the variable resonant module, and is configured to adjust a resonant parameter of the variable resonant module based on the sampling data.

[0008] Preferably, the sampling unit includes a first resistor and a first capacitor; A first end of the first capacitor is connected to a connection node between a second end of a primary winding of the transformer and the variable resonant module. A second end of the first capacitor is connected to a first end of the first resistor, and a second end of the first resistor is grounded; The signal receiving end of the control chip is connected to a connection node between the first resistor and the first capacitor; Alternatively, the sampling unit includes a sampling resistor; A first end of the sampling resistor is connected to the variable resonant module, a second end of the sampling resistor is grounded, and the signal receiving end of the control chip is connected to a connection node between the sampling resistor and the variable resonant module; Alternatively, the sampling unit includes a Hall sensor; The Hall sensor is connected to the signal receiving end of the control chip and is configured to perform non-contact measurement on a current on the variable resonant module.

[0009] Preferably, the control chip is configured to determine the resonance period based on the sampling data, and adjust the resonance parameters of the variable resonance module according to the resonance period and a preset reference period.

[0010] Preferably, the sampling data includes a sampling voltage; The sampling voltage is the voltage of the variable resonance module collected by the sampling unit when the first switch tube is turned off and the second switch tube is turned on; The control chip is configured to determine the resonance period based on the sampling voltage.

[0011] Preferably, the determining the resonance period based on the sampling voltage includes: Obtaining a sampling voltage change rate based on two adjacent sampling voltages and a sampling interval time; Obtaining a time interval between the moment when the sampling voltage is 0 and the moment when the sampling voltage change rate is 0; Determining the resonance period based on the time interval.

[0012] Preferably, the variable resonance module includes a third switch tube, a main resonance capacitor, and an auxiliary resonance capacitor; The first end of the main resonance capacitor is connected to the second end of the primary winding of the transformer, and the second end of the main resonance capacitor is grounded; The auxiliary resonance capacitor and the third switch tube are connected in series between the second end of the primary winding of the transformer and the ground; The control chip is connected to the third switch tube, and is configured to determine the resonance period based on the sampling data, and control the operation of the third switch tube according to the resonance period and a preset reference period.

[0013] Preferably, the control chip is configured to control the third switch tube to be turned on when the resonance period is less than a preset reference period.

[0014] An embodiment of the present invention further provides a power supply circuit, including a rectifier bridge and a PFC circuit, an electrolytic capacitor, a secondary rectification and filtering circuit, and the asymmetrical half-bridge circuit according to any one of the above; The input end of the rectifier bridge and the PFC circuit is used to connect to a mains circuit, and the output end of the rectifier bridge and the PFC circuit is connected to the electrolytic capacitor; The signal input end of the asymmetrical half-bridge circuit is connected to the electrolytic capacitor, and the output end of the asymmetrical half-bridge circuit is connected to the input end of the secondary rectification and filtering circuit; The output end of the secondary rectification and filtering circuit is used to connect to an external load to supply power to the external load.

[0015] An embodiment of the present invention further provides a charger, including the above power supply circuit.

[0016] An embodiment of the present invention provides an asymmetric half-bridge circuit, a power supply circuit, and a charger. A variable resonance module with adjustable resonance parameters is provided in the asymmetric half-bridge circuit. During circuit operation, the resonance parameters of the variable resonance module can be adjusted based on sampled data on the variable resonance module to prevent the asymmetric half-bridge circuit from operating in a sub-resonant state due to component tolerances. This can compensate for the problems of a small resonance period and low power efficiency caused by component tolerances, ensure that the secondary side conduction time is long enough, and ensure that the power efficiency complies with regulations. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0018] Figure 1 This is a schematic diagram of the circuit structure of an asymmetric half-bridge circuit in the prior art; Figure 2 1 is a schematic diagram of the circuit structure of an asymmetric half-bridge circuit in one embodiment of the present invention; Figure 3 This is a working waveform diagram of an asymmetric half-bridge circuit in the prior art; Figure 4 This is another working waveform diagram of the asymmetric half-bridge circuit in the prior art; Figure 5 This is another working waveform diagram of the asymmetric half-bridge circuit in the prior art; Figure 6 FIG. 4 is a working waveform diagram of an asymmetric half-bridge circuit according to an embodiment of the present invention.

[0019] In the figure: 1. Variable resonance module; 2. Control module; 21. Sampling unit. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] It should be understood that the present invention can be implemented in different forms and should not be construed as limited to the embodiments set forth herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. The same reference numerals throughout the drawings denote the same elements.

[0022] It should be understood that when an element or layer is referred to as being "on", "adjacent to", "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on", "directly adjacent to", "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or portions, these elements, components, regions, layers and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or portion from another element, component, region, layer or portion. Thus, a first element, component, region, layer or portion discussed below may be denoted as a second element, component, region, layer or portion without departing from the teachings of the present invention.

[0023] Spatial relationship terms such as "under", "below", "beneath", "underneath", "above", "over", etc. are used herein for convenience in describing the relationship of one element or feature to another element or feature shown in the figures. It should be understood that, in addition to the orientation shown in the figures, spatial relationship terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figures is flipped, then an element or feature described as "under" or "beneath" or "underneath" another element or feature will be oriented "over" the other element or feature. Thus, the exemplary terms "under" and "beneath" can include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatial descriptors used herein are to be interpreted accordingly.

[0024] The purpose of the terms used herein is only to describe specific embodiments and is not a limitation of the present invention. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, specify the presence of the stated features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups. As used herein, the term "and / or" includes any and all combinations of the associated listed items.

[0025] To thoroughly understand the present invention, detailed structures and steps will be presented in the following description to illustrate the technical solutions proposed by the present invention. The preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may also have other embodiments.

[0026] An embodiment of the present invention provides an asymmetrical half-bridge circuit, as Figure 2 shown, which includes a first switching transistor Q1, a second switching transistor Q2, a resonant inductor L1, a variable resonant module 1, a transformer T1, and a control module 2. The first switching transistor Q1 and the second switching transistor Q2 are connected in series between the signal input terminal and the ground. The connection node between the first switching transistor Q1 and the second switching transistor Q2 is connected to the first end of the primary winding of the transformer T1 through the resonant inductor L1. The second end of the primary winding of the transformer T1 is grounded through the variable resonant module 1. The control module 2 is connected to the first switching transistor Q1 and the second switching transistor Q2, and is also connected to the variable resonant module 1, and is used to alternately control one of the first switching transistor Q1 and the second switching transistor Q2 to conduct and the other to turn off, and obtain the sampling data on the variable resonant module 1, and control and adjust the resonant parameters of the variable resonant module 1 according to the sampling data.

[0027] As an example, the asymmetrical half-bridge circuit includes a first switching transistor Q1, a second switching transistor Q2, a resonant inductor L1, a variable resonant module 1, a transformer T1, and a control module 2. The first switching transistor Q1 and the second switching transistor Q2 are connected in series between the signal input terminal and the ground. The connection node between the first switching transistor Q1 and the second switching transistor Q2 is connected to the first end of the primary winding of the transformer T1 through the resonant inductor L1. The second end of the primary winding of the transformer T1 is grounded through the variable resonant module 1. The control module 2 is connected to the first switching transistor Q1 and the second switching transistor Q2, and is also connected to the variable resonant module 1.

[0028] In the prior art, as Figure 1 shown, the asymmetrical half-bridge circuit includes two upper and lower switching transistors Q1 and Q2 connected in series, a resonant inductor L1, a resonant capacitor C, and a transformer T1. When the asymmetrical half-bridge circuit works, the working waveform is as Figure 3 shown: (1) Stage t0 - t2. Before t0, the body diode of the first switching transistor Q1 gradually conducts, and the voltage at the VHB point gradually rises from 0V to Vbus, providing conditions for the first switching transistor Q1 to achieve zero-voltage switching (ZVS). At the moment of t0, the control chip outputs a high level to the gate of the first switching transistor Q1, causing the current to transfer from the body diode of the first switching transistor Q1 to the channel.

[0029] During the time period from t1 to t2, the resonant cavity current flows through the resonant inductor L1, the magnetizing inductor LM of the primary side of the transformer T1, and the resonant capacitor C in sequence. The current is denoted as I_Mag_pos and linearly increases, storing energy in the resonant cavity.

[0030] (2) Stage from t2 to t5. At t2, the control chip outputs a low level to the gate of the first switch Q1. I_Mag_pos freewheels through the body diode of the second switch Q2, and the voltage at the VHB point drops from Vbus to 0, providing conditions for achieving ZVS for the second switch Q2. At t3, the control chip outputs a high level to the gate of the second switch Q2, and the current transfers from the body diode of the second switch Q2 to the channel. During the time period from t3 to t5, the energy stored in the resonant cavity is released to the secondary side. At this time, the output freewheeling diode D1 connected to the secondary side of the transformer T1 conducts. During this time period, the voltage across the magnetizing inductor LM is clamped at NVout, where N represents the ratio of the number of turns of the primary side to the number of turns of the secondary side of the transformer T1, and Vout represents the output voltage. Therefore, the magnetizing current linearly decreases at a slope of NVout / LM; at the same time, the resonant inductor L1 and the resonant capacitor C resonate, and the resonant current changes according to the law of a sine wave. When the resonant current is equal to the magnetizing current, the output freewheeling diode turns off, corresponding to t5.

[0031] Therefore, the resonant frequency of the resonant inductor L1 and the resonant capacitor C and the demagnetization speed of LM will affect the conduction time of the output freewheeling diode D1, and its conduction time is denoted as Toff = t5 - t3.

[0032] Denote the time of a switching period as T. Refer to Figure 2 , T = t6 - t0, and Toff = t5 - t3. The secondary side only provides energy to the output terminal during the Toff time period, that is, energy transmission needs to be completed during the Toff time period in a switching period T. Refer to Equation (1) below. If the Toff time becomes smaller, that is, the ratio of Toff / T becomes smaller, then the peak value of the secondary side current Isec needs to be relatively large to achieve sufficient energy transmission in a short time, which will cause the effective value of the current to increase, and then cause the line loss of the transformer T1 and the loss of the switch to increase, resulting in a poor efficiency of the power supply.

[0033] According to the law of conservation of charge, the following relationship is satisfied. In the formula, Io is the output current. Since the output voltage needs to be controlled stably, the amount of charge flowing in and out within one cycle needs to be balanced.

[0034] (Equation (1)) When operating at full load, the asymmetrical half-bridge circuit has two operating states: over-resonance and under-resonance. (1) Over-resonance operating state Such as Figure 4As shown, at time t5, the resonant currents Ir and Imag do not converge. Toff = t5 - t3, the conduction time of the secondary side is the longest, and the peak current of the secondary side is denoted as Is1. In this operating state, the effective value of the current is small and the operating efficiency is high.

[0035] (2) Under-resonant operating state As Figure 5 shown, before time t5, the resonant currents Ir and Imag have converged, and the conduction time of the secondary side Toff < t5 - t3. According to Equation 1, Is2 > Is1, and the effective value of the current on the secondary side is greater than that in the over-resonant state, resulting in a lower efficiency.

[0036] In an asymmetrical half-bridge circuit, there are certain "tolerances" in the resonant inductor L1 and the resonant capacitor C used, which will cause differences between the actual parameters of the hardware and the calibrated parameters. For example, the resonant inductor L1 is usually the leakage inductance of the transformer T1 or a discrete inductor. Since the inductance of the magnetic component is usually controlled by the size of the air gap in the middle column of the magnetic component, there is a tolerance in the processing of the air gap, so there are differences in the actual inductance values between samples. Usually, the tolerance of the inductance is about ±7%. When the inductance value of the resonant inductor L1 and the capacitance value of the resonant capacitor C are both smaller than the calibrated values, it will cause the actual resonant period to be smaller than the theoretical value, resulting in the asymmetrical half-bridge circuit operating in the under-resonant state and the power supply efficiency deteriorating.

[0037] In this example, the control module 2 can control and change the resonant parameters of the variable resonant module 1. In the initial state, the variable resonant module 1 can be in an initial resonant parameter. For example, part of the resonant capacitors in the variable resonant module 1 participate in the circuit resonance, and the initial resonant parameter is the capacitance value of the part of the resonant capacitors currently participating in the resonance. Under the initial resonant parameter, the control module 2 controls the first switch tube Q1 and the second switch tube Q2 to conduct alternately, so that the resonant inductor L1, the primary winding of the transformer T1, and the variable resonant module 1 resonate to transfer energy to the secondary winding of the transformer T1. At the same time, the control module 2 also obtains the sampling data on the variable resonant module 1 and controls and adjusts the resonant parameters of the variable resonant module 1 according to this sampling data to prevent the asymmetrical half-bridge circuit from operating in the under-resonant state due to device tolerances. Specifically, the control module 2 can obtain the resonant current on the variable resonant module 1, calculate the resonant period according to this resonant current. When the resonant period is less than the preset reference period calculated based on the initial resonant parameter, the control module 2 controls and adjusts the resonant parameters of the variable resonant module 1 to expand the resonant period, compensate for the problem of the resonant period being too small caused by device tolerances, ensure that the conduction time of the secondary side is long enough, and the power supply efficiency meets the requirements.

[0038] In one embodiment, the control module 2 includes a control chip U1 and a sampling unit 21; a first control terminal HG of the control chip U1 is connected to a first switching transistor Q1, and a second control terminal LG of the control chip U1 is connected to a second switching transistor Q2, configured to alternately control one of the first switching transistor Q1 and the second switching transistor Q2 to be turned on and the other to be turned off; a first terminal of the sampling unit 21 is connected to the variable resonance module 1, and a second terminal of the sampling unit 21 is connected to a signal receiving terminal Vcs of the control chip U1, configured to collect sampling data corresponding to the variable resonance module 1; a third control terminal G0 of the control chip U1 is connected to the variable resonance module 1, configured to adjust the resonance parameters of the variable resonance module 1 based on the sampling data.

[0039] As an example, the control module 2 includes a control chip U1 and a sampling unit 21. A first control terminal HG of the control chip U1 is connected to a first switching transistor Q1, and a second control terminal LG of the control chip U1 is connected to a second switching transistor Q2, configured to alternately control one of the first switching transistor Q1 and the second switching transistor Q2 to be turned on and the other to be turned off; a first terminal of the sampling unit 21 is connected to the variable resonance module 1, and a second terminal of the sampling unit 21 is connected to a signal receiving terminal Vcs of the control chip U1; a third control terminal G0 of the control chip U1 is connected to the variable resonance module 1.

[0040] In an initial state, the variable resonance module 1 may be at an initial resonance parameter. At the initial resonance parameter, when the control chip U1 controls the first switching transistor Q1 to be turned on and the second switching transistor Q2 to be turned off, the resonance current sequentially flows through the resonance inductor L1, the primary winding of the transformer T1, and the variable resonance module 1, and the value of the resonance current linearly increases, storing energy in the resonance cavity. When the control chip U1 controls the first switching transistor Q1 to turn off and the second switching transistor Q2 to turn on, the sampling unit 21 may collect sampling data corresponding to the variable resonance module 1, and the control chip U1 adjusts the resonance parameters of the variable resonance module 1 based on the sampling data to prevent the asymmetrical half-bridge circuit from operating in an under-resonance state due to device tolerances.

[0041] In one embodiment, the sampling unit 21 includes a first resistor R1 and a first capacitor C1; a first end of the first capacitor C1 is connected to a connection node between a second end of a primary winding of a transformer T1 and a variable resonance module 1, a second end of the first capacitor C1 is connected to a first end of the first resistor R1, and a second end of the first resistor R1 is grounded; a signal receiving end Vcs of a control chip U1 is connected to the connection node between the first resistor R1 and the first capacitor C1; alternatively, the sampling unit 21 includes a sampling resistor; a first end of the sampling resistor is connected to the variable resonance module 1, a second end of the sampling resistor is grounded, and the signal receiving end Vcs of the control chip U1 is connected to the connection node between the sampling resistor and the variable resonance module 1; alternatively, the sampling unit includes a Hall sensor; the Hall sensor is connected to the signal receiving end Vcs of the control chip U1 and is configured to perform a non-contact measurement on a current on the variable resonance module 1.

[0042] As an example, the sampling unit 21 may include a first resistor R1 and a first capacitor C1; a first end of the first capacitor C1 is connected to a connection node between a second end of a primary winding of a transformer T1 and a variable resonance module 1, a second end of the first capacitor C1 is connected to a first end of the first resistor R1, and a second end of the first resistor R1 is grounded; a signal receiving end Vcs of a control chip U1 is connected to the connection node between the first resistor R1 and the first capacitor C1. The first capacitor C1 is used for energy storage and filtering, and a sampling voltage Vcs obtained by the sampling unit 21 is the same as the voltage across the first resistor R1.

[0043] As another example, the sampling unit 21 may also include a sampling resistor, one end of the sampling resistor is connected in series with the variable resonance module 1, the other end of the sampling resistor is grounded, a signal receiving end Vcs of the control chip U1 is connected to the connection node between the sampling resistor and the variable resonance module 1, and a sampling voltage Vcs obtained by the sampling unit 21 is the same as the voltage across the sampling resistor.

[0044] As another example, the sampling unit 21 may also include a Hall sensor. The Hall sensor is connected to the signal receiving end Vcs of the control chip U1 and is disposed close to the variable resonance module 1. It can perform a non-contact measurement on the current on the variable resonance module 1 based on the principle of electromagnetic induction and send the detected sampling voltage Vcs to the control chip U1.

[0045] In one embodiment, the control chip U1 is configured to determine a resonance period based on sampling data and adjust resonance parameters of the variable resonance module 1 according to the resonance period and a preset reference period.

[0046] As an example, the control chip U1 can obtain the sampling data on the variable resonance module 1 through the sampling unit 21. Based on this sampling data, the control chip U1 calculates and obtains the resonance period of the asymmetrical half-bridge circuit when the variable resonance module 1 is at the current resonance parameters, so as to adjust the resonance parameters of the variable resonance module 1 according to the resonance period and the preset reference period. Among them, the preset reference period is the theoretical resonance period calculated based on the calibrated inductance value of the resonance inductor L1 in the current asymmetrical half-bridge circuit and the calibrated capacitance value of the resonance capacitor participating in resonance in the variable resonance module 1 in the initial state. Usually, this theoretical resonance period is set to 2 , where L is the calibrated inductance value of the resonance inductor L1, and C is the calibrated capacitance value of the resonance capacitor participating in resonance in the variable resonance module 1 in the initial state.

[0047] In an embodiment, the sampling data includes a sampling voltage Vcs; the sampling voltage Vcs is the voltage of the variable resonance module 1 collected by the sampling unit 21 when the first switching tube Q1 is turned off and the second switching tube Q2 is turned on; the control chip U1 is configured to determine the resonance period based on the sampling voltage Vcs.

[0048] As an example, when the control chip U1 controls the first switching tube Q1 to be turned on and the second switching tube Q2 to be turned off, the resonance current flows through the resonance inductor L1, the primary winding of the transformer T1, and the variable resonance module 1 in sequence, and the resonance current value rises linearly, storing energy in the resonance cavity. When the control chip U1 controls the first switching tube Q1 to turn into the off state and the second switching tube Q2 to turn into the on state, the energy stored in the resonance cavity is released to the secondary of the transformer T1. As Figure 6 shown, the control chip U1 controls the first switching tube Q1 to turn into the off state and the second switching tube Q2 to turn into the on state corresponding to the moment t1. At this time, the resonance inductor L1 and the variable resonance module 1 resonate, and the resonance current starts to change according to the law of a sine wave. The sampling unit 21 outputs the sampling voltage Vcs to the control chip U1 based on the resonance current of the variable resonance module 1. The control chip U1 can calculate and obtain the resonance period based on the sampling voltage Vcs, and adjust the resonance parameters of the variable resonance module 1 based on the resonance period. For example, when the resonance period is less than the preset reference period, it is controlled to increase the capacitance value of the resonance capacitor in the variable resonance module 1 to extend the resonance period to make it meet the preset, compensating for the problem of the resonance period being too small caused by device tolerances and ensuring that the conduction time of the secondary side is long enough and the power supply efficiency is compliant.

[0049] In an embodiment, determining the resonance period based on the sampling voltage Vcs includes: obtaining the sampling voltage change rate based on two adjacent sampling voltages Vcs and the sampling interval time; obtaining the time interval between the moment when the sampling voltage Vcs is 0 and the moment when the sampling voltage change rate is 0; and determining the resonance period based on the time interval.

[0050] As an example, when the variable resonance module 1 is under the initial resonance parameters, as Figure 6 shown, after the control chip U1 controls the first switching transistor Q1 to turn off from the on state and the second switching transistor Q2 to turn on from the off state at time t1, the sampling unit 21 can continuously sample the resonance current on the variable resonance module 1, obtain a series of sampling voltages Vcs, record the voltage values corresponding to each sampling voltage Vcs, and calculate the sampling voltage change rate according to two adjacent sampling voltages Vcs and the sampling interval time. When the control chip U1 detects that the sampling voltage Vcs is 0 at time t2, it means that the current value of the resonance current on the current variable resonance module 1 is 0, the direction of the resonance current changes, from positive current to negative current, and the current moment is the zero-crossing point of the resonance current. When the sampling voltage change rate is 0 at time t3, it means that the current change rate of the resonance current on the current variable resonance module 1 is 0, the current resonance current is in the negative current peak state, and the current moment is the resonance current peak point. Since the resonance current changes according to the sine wave law after the control chip U1 controls the first switching transistor Q1 to turn off from the on state and the second switching transistor Q2 to turn on from the off state, the time interval between the zero-crossing point moment of the resonance current and the resonance current peak point is one-fourth of the resonance period. The control chip U1 obtains the time interval between the moment when the voltage value of the sampling voltage Vcs is 0 and the moment when the sampling voltage change rate is 0, and then quadruples this time interval to obtain the resonance period.

[0051] In an embodiment, the variable resonance module 1 includes a third switching transistor Q3, a main resonance capacitor C2, and an auxiliary resonance capacitor C3; the first end of the main resonance capacitor C2 is connected to the second end of the primary winding of the transformer T1, and the second end of the main resonance capacitor C2 is grounded; the auxiliary resonance capacitor C3 and the third switching transistor Q3 are connected in series between the second end of the primary winding of the transformer T1 and the ground; the control chip U1 is connected to the third switching transistor Q3 and is configured to determine the resonance period based on the sampling data and control the third switching transistor Q3 to operate according to the resonance period and a preset reference period.

[0052] As an example, the variable resonance module 1 includes a third switching transistor Q3, a main resonance capacitor C2, and an auxiliary resonance capacitor C3. The main resonance capacitor C2 is connected between the second end of the primary winding of the transformer T1 and the ground; wherein, the third switching transistor Q3 can be an NMOS transistor, the drain of the NMOS transistor is connected to the second end of the primary winding of the transformer T1, the source of the NMOS transistor is connected to the auxiliary resonance capacitor, and the gate of the NMOS transistor is connected to the third control terminal G0 of the control chip U1 in the control module 2.

[0053] In the initial state, the third switch Q3 in the variable resonance module 1 can be turned off so that only the main resonance capacitor C2 in the variable resonance module 1 works, and the capacitance value of the main resonance capacitor C2 is used as the initial resonance parameter. During the operation of the asymmetrical half-bridge circuit, the control chip U1 controls the interleaved conduction of the first switch Q1 and the second switch Q2. The control chip U1 calculates and obtains the resonance period according to the sampling voltage Vcs acquired by the sampling unit 21, and controls the operation of the third switch Q3 according to the resonance period and the preset reference period. For example, when the resonance period is less than the preset reference period, the control chip U1 outputs a high-level signal to the third switch Q3 to change the state of the third switch Q3 from off to on, so that the main resonance capacitor C2 and the auxiliary resonance capacitor C3 in the variable resonance module 1 are used in parallel to extend the resonance period to meet the preset, compensate for the problem of the resonance period being too small caused by device tolerances, ensure that the conduction time of the secondary side is long enough, and the power supply efficiency is compliant.

[0054] In one embodiment, the control chip U1 is configured to control the third switch Q3 to turn on when the resonance period is less than the preset reference period.

[0055] As an example, in the initial state, the third switch Q3 in the variable resonance module 1 can be in the off state. When the control chip U1 detects that the resonance period is less than the reference resonance period, the control chip U1 controls the third switch Q3 to turn on, so that the auxiliary resonance capacitor C3 and the main resonance capacitor C2 participate in the circuit resonance together to extend the resonance period, compensate for the problem of the resonance period being too small caused by device tolerances, ensure that the conduction time of the secondary side is long enough, and the power supply efficiency is compliant.

[0056] The embodiment of the present invention further provides a power supply circuit, including a rectifier bridge, a PFC circuit, an electrolytic capacitor, a secondary rectification and filtering circuit, and the asymmetrical half-bridge circuit in the above embodiment; the input end of the rectifier bridge and the PFC circuit is used to connect to the mains circuit, and the output end of the rectifier bridge and the PFC circuit is connected to the electrolytic capacitor; the signal input end of the asymmetrical half-bridge circuit is connected to the electrolytic capacitor, and the output end of the asymmetrical half-bridge circuit is connected to the input end of the secondary rectification and filtering circuit; the output end of the secondary rectification and filtering circuit is used to connect to an external load to supply power to the external load.

[0057] As an example, the power supply circuit includes a rectifier bridge, a PFC circuit, an electrolytic capacitor, a secondary rectification and filtering circuit, and the asymmetrical half-bridge circuit in the above embodiment; the input end of the rectifier bridge and the PFC circuit is used to connect to the mains circuit, and the output end of the rectifier bridge and the PFC circuit is connected to the electrolytic capacitor; the signal input end of the asymmetrical half-bridge circuit is connected to the electrolytic capacitor, and the output end of the asymmetrical half-bridge circuit is connected to the input end of the secondary rectification and filtering circuit; the output end of the secondary rectification and filtering circuit is used to connect to an external load to supply power to the external load. In this example, a variable resonance module 1 with adjustable resonance parameters is provided in the power supply circuit. During the operation of the circuit, based on the sampled data on the variable resonance module 1, the resonance parameters of the variable resonance module can be adjusted to prevent the asymmetrical half-bridge circuit from operating in an under-resonance state due to device tolerances, and to compensate for the problems of a relatively small resonance period and low power supply efficiency caused by device tolerances, ensuring that the conduction time on the secondary side is long enough and the power supply efficiency meets the standards.

[0058] An embodiment of the present invention further provides a charger, including the power supply circuit in the above embodiment.

[0059] As an example, the charger includes the power supply circuit in the above example. A variable resonance module 1 with adjustable resonance parameters is provided in the power supply circuit. During the operation of the circuit, based on the sampled data on the variable resonance module 1, the resonance parameters of the variable resonance module can be adjusted to prevent the asymmetrical half-bridge circuit from operating in an under-resonance state due to device tolerances, and to compensate for the problems of a relatively small resonance period and low power supply efficiency caused by device tolerances, ensuring that the conduction time on the secondary side is long enough and the power supply efficiency meets the standards.

[0060] The above-described embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention and should all be included within the protection scope of the present invention.

Claims

1. An asymmetric half-bridge circuit, characterized in that: It includes a first switching tube, a second switching tube, a resonant inductor, a variable resonant module, a transformer and a control module; The first switching transistor and the second switching transistor are connected in series between the signal input terminal and the ground. A connection node between the first switching transistor and the second switching transistor is connected to a first end of the primary winding of the transformer via the resonant inductor. A second end of the primary winding of the transformer is grounded via the variable resonant module. The control module is connected to the first switching tube and the second switching tube, and is also connected to the variable resonance module, and is used to staggeredly control one of the first switching tube and the second switching tube to be turned on and the other to be turned off, obtain sampling data corresponding to the variable resonance module, and adjust the resonance parameters of the variable resonance module according to the sampling data.

2. The asymmetric half-bridge circuit according to claim 1, characterized in that: The control module includes a control chip and a sampling unit; The first control terminal of the control chip is connected to the first switch tube, and the second control terminal of the control chip is connected to the second switch tube, for alternately controlling one of the first switch tube and the second switch tube to be turned on and the other to be turned off; The first end of the sampling unit is connected to the variable resonance module, and the second end of the sampling unit is connected to the signal receiving end of the control chip, for collecting sampling data corresponding to the variable resonance module; The third control terminal of the control chip is connected to the variable resonance module and is used to adjust the resonance parameters of the variable resonance module based on the sampled data.

3. The asymmetric half-bridge circuit according to claim 2, characterized in that: The sampling unit includes a first resistor and a first capacitor; A first end of the first capacitor is connected to a connection node between the second end of the primary winding of the transformer and the variable resonance module, a second end of the first capacitor is connected to a first end of the first resistor, and a second end of the first resistor is grounded; The signal receiving end of the control chip is connected to the connection node between the first resistor and the first capacitor; Alternatively, the sampling unit includes a sampling resistor; A first end of the sampling resistor is connected to the variable resonance module, a second end of the sampling resistor is grounded, and a signal receiving end of the control chip is connected to a connection node between the sampling resistor and the variable resonance module; Alternatively, the sampling unit includes a Hall sensor; The Hall sensor is connected to the signal receiving end of the control chip and is used to perform non-contact measurement of the current on the variable resonance module.

4. The asymmetric half-bridge circuit according to claim 2, characterized in that: The control chip is used to determine a resonance period based on the sampled data, and adjust a resonance parameter of the variable resonance module according to the resonance period and a preset reference period.

5. The asymmetric half-bridge circuit according to claim 4, characterized in that: The sampled data includes a sampled voltage; The sampled voltage is the voltage of the variable resonance module collected by the sampling unit when the first switch tube is turned off and the second switch tube is turned on; The control chip is used to determine the resonance period based on the sampled voltage.

6. The asymmetric half-bridge circuit according to claim 5, characterized in that: The determining of the resonance period based on the sampled voltage includes: Obtaining a sampling voltage change rate based on two adjacent sampling voltages and a sampling interval; Obtain the time interval between the moment when the sampled voltage is 0 and the moment when the sampled voltage change rate is 0; A resonance period is determined based on the time interval.

7. The asymmetric half-bridge circuit according to claim 4, characterized in that: The variable resonance module includes a third switch tube, a main resonance capacitor and an auxiliary resonance capacitor; The first end of the main resonant capacitor is connected to the second end of the primary winding of the transformer, and the second end of the main resonant capacitor is grounded; The auxiliary resonant capacitor and the third switch are connected in series between the second end of the primary winding of the transformer and the ground; The control chip is connected to the third switch tube, and is used to determine the resonance period based on the sampling data, and control the operation of the third switch tube according to the resonance period and a preset reference period.

8. The asymmetric half-bridge circuit according to claim 7, characterized in that: The control chip is used to control the third switch tube to be turned on when the resonance period is less than the preset reference period.

9. A power supply circuit, characterized in that: It comprises a rectifier bridge and a PFC circuit, an electrolytic capacitor, a secondary rectifier filter circuit and the asymmetric half-bridge circuit according to any one of claims 1 to 8; The input end of the rectifier bridge and the PFC circuit is used to connect to the mains circuit, and the output end of the rectifier bridge and the PFC circuit is connected to the electrolytic capacitor; The signal input end of the asymmetric half-bridge circuit is connected to the electrolytic capacitor, and the output end of the asymmetric half-bridge circuit is connected to the input end of the secondary rectifier and filter circuit; The output end of the secondary rectifier and filter circuit is used to connect to an external load to supply power to the external load.

10. A charger, characterized in that: Includes the power supply circuit according to claim 9.

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