Multi-output resonant flyback converter

Abstract

The invention discloses a multi-output resonant flyback converter, which comprises a half-bridge circuit, a resonant capacitor, a resonant cavity and a multi-output circuit, and is characterized in that one end of the resonant inductor is connected to a central point of a half-bridge power switch tube of the half-bridge circuit, and the other end of the resonant inductor is connected in series with a synonym end of a primary excitation inductor of a transformer; one end of the resonant capacitor is connected in series with a dotted terminal of an excitation inductor of the transformer, the other end of the resonant capacitor is connected with a primary side reference potential of the transformer, and a synonym terminal of each secondary side winding of the multi-output winding is connected with an output synchronous rectification module matched with each output winding; the multi-output circuit comprises two output circuits; according to the invention, multipath isolated output can be realized, the resonant cavity is in a resonant state, the primary side switch tube can realize ZVS, and the transmission efficiency is improved.

Description

Technical Field

[0001] The invention relates to the field of switch circuits, and in particular to a resonant flyback converter with multiple outputs. Background Art

[0002] At present, the power level of power adapters is mostly in the range of 50W-300W, and the main topologies used are quasi-resonant flyback converter and active clamp flyback converter (ACF). Among them, quasi-resonant or active clamp flyback converter adopts pulse width modulation (PWM) working mode. Adjusting the output voltage gain by changing the switch duty cycle is a derivative of the traditional flyback converter, which overcomes the hard switching of the traditional flyback converter and the low efficiency caused by the leakage inductance energy of the transformer. In order to solve the energy loss problem caused by leakage inductance, the active clamp flyback converter introduces an additional auxiliary switch tube in the main circuit of the transformer. Its driving waveform is complementary to the PWM waveform of the main switch tube, thereby realizing the absorption and negative of leakage inductance energy, reducing the switching loss and output switching noise caused by reverse recovery, thereby reducing electromagnetic interference and device stress, and effectively improving the working efficiency and reliability of the converter.

[0003] Compared with the traditional flyback converter, the output power of the quasi-resonant converter is positively correlated with the size of the transformer, and the output power cannot be increased; although the active clamp flyback converter achieves zero voltage switching operation with the help of the auxiliary switch, improving the working efficiency of the converter. However, since the transformer of the active clamp flyback converter works in a unidirectional excitation state, the volume of its magnetic core is relatively large, which is not conducive to the realization of device miniaturization and the transmission of load energy. Summary of the invention

[0004] The embodiment of the present application solves the technical problems of large size of the flyback converter magnetic core and low energy transfer efficiency in the prior art by providing a resonant flyback converter with multiple outputs.

[0005] An embodiment of the present application provides a resonant flyback converter with multiple outputs, including a half-bridge circuit, a resonant capacitor, a resonant cavity and a multiple output circuit, characterized in that one end of the resonant inductor is connected to the center point of the half-bridge power switch tube of the half-bridge circuit, and the other end is connected in series with the opposite-name end of the primary excitation inductor of the transformer, one end of the resonant capacitor is connected in series with the same-name end of the transformer excitation inductor, and the other end of the resonant capacitor is connected to the primary reference potential of the transformer, and the opposite-name ends of each secondary winding of the multiple output windings are connected to the output synchronous rectification module matching each output winding; the multiple output circuit includes two output circuits.

[0006] Preferably, the resonant cavity includes a resonant inductor and a resonant capacitor.

[0007] Preferably, the resonant inductor may be a leakage inductance of a transformer.

[0008] Preferably, the output circuit includes an output winding, an output filter capacitor, an active clamping module, and a synchronous rectification module.

[0009] Preferably, the active clamping module includes an active clamping switch tube.

[0010] Preferably, the synchronous rectification module includes a synchronous rectification switch tube.

[0011] Preferably, the half-bridge power switch tubes of the half-bridge circuit are driven by complementary signals with dead zones.

[0012] Preferably, the minimum value of the dead time configuration needs to satisfy the requirement that within the dead time, the resonant current existing in the resonant cavity is sufficient to charge the output capacitor of a power switch tube of the upper and lower bridge arms to the bus voltage state and discharge the charge retained in the output capacitor of the tube so that the output capacitor voltage is close to the 0 voltage state.

[0013] The technical solution provided in the embodiments of the present application has the following technical effects or advantages:

[0014] 1. By introducing the advantages of LLC resonant converter into the flyback converter, using the resonant cavity to store energy, realizing ZVS turn-on on the primary side of the transformer and ZCS turn-off on the secondary side, the power density of the traditional flyback converter can be greatly improved.

[0015] 2. A multi-channel output circuit is adopted, and a synchronous rectification drive circuit and an active clamping drive circuit are set to ensure that the secondary side switch tube can be turned off at zero current, thereby improving the rectification efficiency. At the same time, it can absorb the voltage spikes of the first and second windings of the secondary side and reduce the voltage stress of the synchronous rectification switch tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of a resonant flyback converter with multiple outputs in this application;

[0017] Figure 2 A schematic diagram of a synchronous rectification driving circuit in a multi-channel output circuit of the present application;

[0018] Figure 3 This is a schematic diagram of an active clamping driving circuit in a multi-channel output circuit of the present application. DETAILED DESCRIPTION

[0019] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0020] like Figure 1As shown, it is a structural schematic diagram of a multi-output resonant flyback converter provided by the present invention. The multi-output resonant flyback converter includes a half-bridge power switch tube, a resonant capacitor, a resonant cavity and a multi-output circuit. One end of the resonant inductor is connected to the center point of the half-bridge power switch tube, and the other end is connected in series with the opposite-name end of the primary excitation inductor of the transformer. One end of the resonant capacitor is connected in series with the same-name end of the transformer excitation inductor, and the other end of the resonant capacitor is connected to the primary reference potential of the transformer. The opposite-name ends of each secondary winding of the multi-output windings are connected to the output synchronous rectification module matched with each output winding.

[0021] The resonant cavity includes two resonant inductors L m , L r、 and resonant capacitor C r The multi-output circuit includes a transformer, an output circuit 1 and an output circuit 2. The output circuit 1 includes an output winding pin34, an output filter capacitor C50, an active clamp switch tube Q5, and a synchronous rectifier switch tube Q3; the output circuit 2 includes an output winding pin56, an output filter capacitor C51, an active clamp switch tube Q6, and a synchronous rectifier switch tube Q4.

[0022] When the switch tube Q1 is turned on and the switch tube Q2 is turned off, the output synchronous rectification switch tube is in the cut-off state, and the bus voltage Vbus+ passes through Q1 via the resonant inductor L4 and the excitation inductor L m The resonant inductor L is charged to the resonant capacitor C41 m When the switch tube Q1 is turned off and the switch tube Q2 is turned on, the resonant inductor L m The current decreases and energy is released. The output synchronous rectifier switch is in the on state. At this time, the two ends of the excitation inductor are clamped by the output voltage according to the transformer turns ratio. The excitation current drops linearly from the peak value at the turn-off moment. The resonant cavity oscillates with the resonant capacitor voltage and resonant current at the time when Q1 is turned off as the initial conditions. The difference between the excitation current and the resonant current is the current output to the load. When the excitation current drops to the same as the resonant current, Q1 is turned on again and Q2 is turned off, and the power supply injects energy into the resonant cavity again. This cycle repeats, injecting energy during the turn-on period of Q1 and transferring energy to the load during the turn-off period of Q1.

[0023] During the period from Q1 turning on to Q1 turning off and the dead time, the clamped excitation current can be adjusted to charge the output parasitic capacitors of Q1 and Q2 by adjusting the length of the dead time, so that Q2 can be turned on with zero voltage; during the period from Q2 turning on to Q2 turning off and the dead time, the reverse excitation current charges the output parasitic capacitors of Q1 and Q2, so that Q1 can be turned on with zero voltage. The secondary side synchronous rectification switch tube can achieve zero current shutdown. The minimum value of the dead time configuration needs to satisfy that during the dead time, the resonant current existing in the resonant cavity is sufficient to charge the output capacitor of a power switch tube of the upper and lower bridge arms to the bus voltage state and discharge the charge retained in the output capacitor of the tube so that the output capacitor voltage is close to the 0 voltage state.

[0024] like Figure 2 As shown, the present invention provides a schematic diagram of a synchronous rectification drive circuit in a multi-channel output circuit, U9 and U10 are gate drivers of the synchronous rectification switch tube, and the DSP_SR1 and DSP_SR2 signals issued by the controller drive the synchronous rectification switch tubes of the output circuit 1 and the output circuit 2 respectively through the gate drivers U9 and U10, which can realize zero current shutdown of the secondary side switch tube and improve the rectification efficiency.

[0025] like Figure 3 As shown, the present invention provides a schematic diagram of an active clamping drive circuit in a multi-channel output circuit, U11 and U12 are gate drivers of the active clamping switch tube, and the DSP_AC1 and DSP_AC2 signals sent by the controller drive the active clamping switch tubes of the output circuit 1 and the output circuit 2 respectively through the gate drivers U11 and U12, which can absorb the voltage spikes of the secondary output circuit 1 and the output circuit 2 and reduce the voltage stress of the synchronous rectification switch tube.

[0026] The embodiments of this specific implementation mode are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention should be included in the protection scope of the present invention. Although the preferred embodiments of the present invention have been described, once the technical personnel in this field know the basic creative concept, they can make other changes and modifications to these embodiments. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, the technical personnel in this field can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. In this way, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and variations.

Claims

1. A resonant flyback converter with multiple outputs, comprising a half-bridge circuit, a resonant capacitor, a resonant cavity and a multiple output circuit, characterized in that: One end of the resonant inductor is connected to the center point of the half-bridge power switch tube of the half-bridge circuit, and the other end is connected in series with the opposite-name end of the primary excitation inductor of the transformer. One end of the resonant capacitor is connected in series with the same-name end of the transformer excitation inductor, and the other end of the resonant capacitor is connected to the primary reference potential of the transformer. The opposite-name ends of each secondary winding of the multi-output winding are connected to the output synchronous rectification module matched with each output winding; the multi-output circuit includes two output circuits.

2. The resonant flyback converter according to claim 1, characterized in that: The resonant cavity includes a resonant inductor and a resonant capacitor.

3. The resonant flyback converter according to claim 2, characterized in that: The resonant inductor may be a leakage inductance of a transformer.

4. The resonant flyback converter according to claim 1, characterized in that: The output circuit includes an output winding, an output filter capacitor, an active clamping module, and a synchronous rectification module.

5. The resonant flyback converter according to claim 4, characterized in that: The active clamping module includes an active clamping switch tube.

6. The resonant flyback converter according to claim 4, characterized in that: The synchronous rectification module includes a synchronous rectification switch tube.

7. The resonant flyback converter according to claim 1, characterized in that: The half-bridge power switch tubes of the half-bridge circuit are driven by complementary signals with dead zones.

8. The resonant flyback converter according to claim 7, characterized in that: The minimum value of the dead time configuration of the half-bridge power switch tube needs to satisfy the requirement that during the dead time, the resonant current existing in the resonant cavity is sufficient to charge the output capacitor of a power switch tube of the upper and lower bridge arms to the bus voltage state and discharge the charge retained in the output capacitor of the tube so that the output capacitor voltage is close to the 0 voltage state.

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