Winding multiplexing soft switching flyback circuit

Abstract

The winding multiplexing soft switching flyback circuit comprises an energy storage unit, a main control unit, a switch unit, a VCC power supply soft switching unit, a sampling unit, a high-frequency transformer unit and a rectification output unit. According to the utility model, the second primary winding of the flyback switching power supply is used as the main power winding, the VCC power supply winding and the soft switching auxiliary winding to supply power to the main control unit and realize the soft switching of the main switch, compared with the conventional flyback topology, the flyback topology circuit can realize the ZVS of the main power tube, and can realize the soft switching of the main switch. Meanwhile, a soft switch auxiliary winding does not need to be added, loss is reduced, transformer primary side framework pins can be effectively reduced, and therefore the size of the transformer is reduced.

Description

TECHNICAL FIELD

[0001] The utility model belongs to electronic circuit technical field, especially relate to a winding multiplex soft switch flyback circuit. BACKGROUND

[0002] The traditional flyback converter, when the switch tube is turned on, the voltage across the switch tube and the current flowing through it have a clear overlap region, and the switching loss generated in this overlap region will cause low system efficiency and switch tube heating problems, and with the increase of switching frequency, the temperature rise of the switch tube will further intensify, thus limiting the high-frequency development of the switching power supply, and it is difficult to reduce the size of the system and improve the power density, if the flyback circuit can make the voltage across the source and drain electrodes drop to zero before the switch tube is turned on, eliminate the voltage and current overlap region in the on process, and realize the ZVS opening of the switch tube, the system performance of the source drive converter can be greatly improved, the commonly used method to reduce the opening loss on the market is to use quasi-resonant control to turn on at the "bottom" of the intermittent oscillation of the switch tube, but the "bottom" turn-on cannot realize complete ZVS, and there is always voltage and current overlap loss, and with the increase of frequency, this part of the loss will become larger and larger, resulting in serious heating of the switch tube, and another way to realize soft switching needs to add an auxiliary winding, and uses the negative current generated by the reverse excitation of the auxiliary winding to realize the soft switching of the main switch, but a winding needs to be added, which does not meet the miniaturization requirement of the switching power supply. SUMMARY

[0003] Therefore, the utility model wants to solve the technical problem to provide a winding multiplex soft switch flyback converter, which can effectively reduce the switching loss of the switch tube, realize the ZVS opening of the main switch tube, improve the efficiency of the switching power supply, and does not need to add an auxiliary winding, and can also save a VCC winding, further reduce the size of the transformer skeleton, and meet the miniaturization requirement of the switching power supply.

[0004] In order to realize the above purpose, the utility model adopts the following technical scheme:

[0005] The utility model embodiment provides a winding multiplex soft switch flyback circuit, the winding multiplex soft switch flyback circuit includes energy storage unit, main control unit, switch unit, VCC power supply soft switch unit, sampling unit, high frequency transformer unit and rectifier output unit;

[0006] The first end of the energy storage unit is connected to the positive input port and the opposite end of the first primary winding of the high-frequency transformer respectively, the same end of the first primary winding is connected to the first end of the switch unit, the second end of the switch unit is connected to the first end of the sampling unit and the first end of the master control unit respectively, the second end of the sampling unit is connected to the opposite end of the second primary winding of the high-frequency transformer unit and the first end of the VCC power soft switch unit respectively, the same end of the second primary winding is connected to the negative input port, the second end of the energy storage unit and the second end of the VCC power soft switch unit respectively, the same end of the secondary winding of the high-frequency transformer unit is connected to the first end of the rectifier output unit, the opposite end of the secondary winding is connected to the second end of the rectifier output unit, the output end of the VCC power soft switch unit is connected to the input end of the master control unit, and the output end of the master control unit is connected to the control end of the switch unit.

[0007] When the VCC power soft switch unit is turned on, the energy stored in the rectifier output unit is transmitted to the second primary winding through the VCC power soft switch unit for reverse excitation, so that the first primary winding and the second primary winding generate negative current, so that the switch unit realizes zero voltage turn-on.

[0008] Optionally, the energy storage unit includes a first capacitor, the first end of the first capacitor is connected to the positive input port and the opposite end of the first primary winding respectively, and the second end of the energy storage unit is connected to the negative input port, the same end of the second primary winding and the second end of the VCC power soft switch unit respectively.

[0009] Optionally, the master control unit includes a control chip, the CS sampling pin of the control chip is connected to the second end of the switch unit and the first end of the sampling unit respectively, the power supply pin of the control chip is connected to the output end of the VCC power soft switch unit, the driving pin of the control chip is connected to the control end of the switch unit, and the IC ground pin of the control chip is connected to the ground end.

[0010] Optionally, the switch unit includes a first switch tube, the first end of the first switch tube is connected to the same end of the first primary winding, the second end of the first switch tube is connected to the first end of the sampling unit and the first end of the master control unit respectively, and the control end of the first switch tube is connected to the output end of the master control unit.

[0011] Optionally, the sampling unit comprises a first resistor, a first end of the first resistor is connected to the second end of the switch unit and the first end of the main control unit respectively, and a second end of the first resistor is connected to the opposite end of the second primary winding of the high-frequency transformer unit and the first end of the VCC power soft switch unit respectively.

[0012] Optionally, the VCC power soft switch unit comprises a second switch tube and a second capacitor, a first end of the second capacitor is connected to the opposite end of the second primary winding and the second end of the sampling unit respectively, a first end of the second switch tube is connected to the second end of the second capacitor and the input end of the main control unit respectively, and a second end of the second switch tube is connected to the negative input port, the second end of the energy storage unit and the same end of the second primary winding respectively.

[0013] Optionally, the VCC power soft switch unit comprises a first diode, an auxiliary switch and a second capacitor, a first end of the second capacitor is connected to the opposite end of the second primary winding and the second end of the sampling unit respectively, a cathode of the first diode is connected to the second end of the second capacitor and the input end of the main control unit respectively, an anode of the first diode is connected to the negative input port, the second end of the energy storage unit and the same end of the second primary winding respectively, and the auxiliary switch is connected in parallel with the first diode.

[0014] Optionally, the rectification output unit comprises a second diode and a third capacitor, an anode of the second diode is connected to the same end of the secondary winding, a cathode of the second diode is connected to the opposite end of the secondary winding through the third capacitor, a positive pole of the third capacitor is connected to the positive output port, and a negative pole of the third capacitor is connected to the negative output port.

[0015] Optionally, the sampling unit comprises a current transformer, a first end of the current transformer is connected to the second end of the switch unit and the first end of the main control unit respectively, and a second end of the current transformer is connected to the opposite end of the second primary winding of the high-frequency transformer unit and the first end of the VCC power soft switch unit respectively.

[0016] Optionally, the main control unit comprises a single-chip microcomputer, a sampling end of the single-chip microcomputer is connected to the second end of the switch unit and the first end of the sampling unit respectively, a power supply end of the single-chip microcomputer is connected to the output end of the VCC power soft switch unit, a driving end of the single-chip microcomputer is connected to the control end of the switch unit, and a grounding end pin of the single-chip microcomputer is connected to the ground end.

[0017] Optionally, a fourth capacitor and a third switch tube are further included, a first end of the fourth capacitor is connected to the positive input port, a second end of the fourth capacitor is connected to a first end of the third switch tube, and a second end of the third switch tube is connected to the same end of the first primary winding.

[0018] Compared with the prior art, the utility model has the following advantages and beneficial effects:

[0019] The utility model discloses a second primary winding of flyback switching power supply is as main power winding, also as VCC power supply winding and soft switch auxiliary winding, and the main control unit is powered and realizes the soft switch of main switch, relative to conventional flyback topology, the utility model discloses a ZVS of main power tube can be realized, and the soft switch auxiliary winding is not needed to increase simultaneously, not only reduce the loss, can effectively reduce transformer primary skeleton pin, thereby reduce the transformer volume. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is the principle block diagram of a winding multiplexing soft switch flyback circuit of the utility model;

[0021] Figure 2 It is the circuit principle diagram of a winding multiplexing soft switch flyback circuit first embodiment of the utility model;

[0022] Figure 3 It is the circuit principle diagram of a winding multiplexing soft switch flyback circuit second embodiment of the utility model;

[0023] Figure 4 It is the control timing diagram of soft switch in a winding multiplexing soft switch flyback circuit embodiment of the utility model;

[0024] Figure 5 It is the circuit principle diagram of a winding multiplexing soft switch flyback circuit third embodiment of the utility model. DETAILED DESCRIPTION

[0025] The utility model and its beneficial effects will be explained in further detail by combining with specific implementation and the drawings of specification, obviously, the described embodiment is a part of the utility model embodiment, instead of all embodiments. Based on the embodiment in the application, all other embodiments obtained by the person skilled in the art without making creative labor should belong to the scope of the application protection.

[0026] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims of the present application are intended to cover a non-exclusive inclusion, for example, a covering of an array of elements, units, or control sequences not necessarily limited to those explicitly listed, but can include additional elements, units, or control sequences that are not expressly listed or inherent to such circuitry.

[0027] In addition, the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0028] It should be understood that in the specification and claims, when it is described that an element is "connected" to another element, the element can be "directly connected" to the other element, or "connected" to the other element through a third element.

[0029] Reference Figure 1 and Figure 2 The embodiment of the utility model provides a winding multiplexing soft switch flyback circuit, including energy storage unit, main control unit, switch unit, VCC power supply soft switch unit, sampling unit, high frequency transformer unit and rectification output unit,

[0030] The first end of the energy storage unit is connected to the positive input port and the opposite name end of the first primary winding in the high frequency transformer respectively, the same name end of the first primary winding is connected to the first end of the switch unit, the second end of the switch unit is connected to the first end of the sampling unit and the first end of the main control unit respectively, the second end of the sampling unit is connected to the opposite name end of the second primary winding in the high frequency transformer unit and the first end of the VCC power supply soft switch unit respectively, the same name end of the second primary winding is connected to the negative input port, the second end of the energy storage unit and the second end of the VCC power supply soft switch unit respectively, the same name end of the secondary winding in the high frequency transformer unit is connected to the first end of the rectification output unit, the opposite name end of the secondary winding is connected to the second end of the rectification output unit, the output end of the VCC power supply soft switch unit is connected to the input end of the main control unit, and the output end of the main control unit is connected to the control end of the switch unit, when the VCC power supply soft switch unit is turned on, the energy stored in the rectification output unit is reversed to excite the second primary winding through the VCC power supply soft switch unit, so that the first primary winding S1 and the second primary winding generate negative current, so that the switch unit realizes zero voltage opening.

[0031] In the first embodiment, the energy storage unit is a first capacitor C1, the master control unit is a control chip U1, the switching unit is a first switch Q1, the sampling unit is a first resistor R1, the VCC power supply soft switching unit includes a second switch Q2 and a second capacitor C2, and the rectified output unit includes a second diode D2 and a third capacitor C3, wherein the first switch Q1 and the second switch Q2 can be implemented by using MOS tubes, field effect tubes or transistors, and in the embodiment, the first switch Q1 and the second switch Q2 are both NMOS tubes. The rectified output unit on the secondary side can also be a MOS tube for synchronous rectification, and the switch in the VCC power supply soft switching unit can also be in the form of a switching diode.

[0032] See Figure 2 The connection mode is as follows: the positive input port VIN+ is connected to the positive end of the first capacitor C1 and the non-identical end of the first primary winding S1 of the high-frequency transformer, the identical end of the first primary winding S1 is connected to the drain of the first switch Q1, the source of the first switch Q1 is connected to one end of the first resistor R1 and the CS sampling pin of the control chip U1, the other end of the first resistor R1 is connected to the ground pin of the control chip U1 and the negative end of the second capacitor C2, and the non-identical end of the second primary winding S2 of the high-frequency transformer is connected to the source of the second switch Q2 of the VCC power supply soft switching unit and the negative end of the first capacitor C1 and the VIN- of the input port, the drain of the second switch Q2 of the VCC power supply soft switching unit is connected to the positive end of the second capacitor C2 and the VCC power supply pin of the control chip U1, the PWM drive pin of the control chip U1 is connected to the gate of the first switch Q1, the identical end of the secondary winding S3 of the high-frequency transformer is connected to the anode of the second diode D2, the cathode of the second diode D2 is connected to the positive end of the third capacitor C3 and the positive output port VOUT+, and the non-identical end of the secondary winding S3 is connected to the negative end of the third capacitor C3 and the negative output port VOUT-.

[0033] The working principle of the embodiment is as follows:

[0034] The control timing sequence of the embodiment is as shown in Figure 4 The driving signal waveform of the first switch Q1 is Q1, the driving signal waveform of the second switch Q2 is Q2, and the current waveform flowing through the first primary winding S1 and the second primary winding S2 is iL.

[0035] Excitation stage: at t0-t1, the PWM gives the first switch Q1 a high-level signal, the first switch Q1 is turned on, and the first primary winding S1 and the second primary winding S2 store energy; at t1, the first switch Q1 is turned off.

[0036] Demagnetization stage: at t1-t2, the first primary winding S1 and the second primary winding S2 pass through the secondary winding S3 and the diode D2 for demagnetization, and the body diode of the switch tube Q2 charges the third capacitor C3; at t2, the energy stored in the first primary winding S1 and the second primary winding S2 in the excitation stage is released, and the excitation current iL flowing through the winding inductance S1 and S2 is zero.

[0037] Reverse excitation stage: at t2-t3, the first switch tube Q1, the second switch tube Q2 and the diode D2 do not work, the voltage of the first primary winding S1 and the second primary winding S2 is no longer clamped, so the voltage of the first primary winding S1 and the second primary winding S2 resonates with some parasitic parameters (inductance, capacitance) in the circuit; at t3, the second switch tube Q2 is turned on, and the energy stored in the third capacitor C3 is used to reverse excitation of the second primary winding S2; at t4, the second switch tube Q2 is turned off.

[0038] ZVS stage: during the dead time of t4-t5, the reverse current extracts the energy of the parasitic capacitor of the first switch tube Q1, and the internal parasitic body diode is turned on; at t5, the first switch tube Q1 is turned on, and the first switch tube Q1 realizes ZVS turn-on.

[0039] Second embodiment:

[0040] Figure 3 The principle diagram of the winding multiplexing soft switching flyback circuit of the utility model second embodiment, compared with the first embodiment, the difference lies in: in the embodiment, the first diode D1 and the auxiliary switch W1 replace the switch tube Q2 in the first embodiment, the same name end of the high frequency transformer S2 winding is connected with the anode of the diode D1 and one end of the switch W1, the cathode of the diode D1 is connected with the other end of the switch W1 and the positive end of the VCC capacitor, and the working principle is same with the first embodiment, which will not be described here.

[0041] Third embodiment:

[0042] Figure 5 The principle diagram of the winding multiplexing soft switching flyback circuit of the utility model third embodiment, compared with the first embodiment, the difference lies in that the soft switching auxiliary winding is realized by the first primary winding S1, and the IC power supply winding is realized by the second primary winding S2, in the embodiment, the same name end of the high frequency transformer first primary winding S1 is connected with the source electrode of the second switch tube Q2, the drain electrode of the second switch tube Q2 is connected with one end of the fourth capacitor C4, the other end of the fourth capacitor C4 is connected with the different name end of the winding S1 and one end of the capacitor C1, and the working principle and control mode are same with the first embodiment, which will not be described here.

[0043] The above embodiment of the present application is only an example for illustrating the present application, and is not a limitation on the embodiment of the present application. For those skilled in the art, other different forms of changes and variations can be made on the basis of the above description. Here, all the embodiments cannot be exhausted. Any obvious changes or variations derived from the technical scheme of the present application are still within the protection scope of the present application.

Claims

1. A winding multiplex soft-switching flyback circuit, characterized in that: The winding multiplexing soft switching flyback circuit comprises an energy storage unit, a main control unit, a switching unit, a VCC power supply soft switching unit, a sampling unit, a high-frequency transformer unit and a rectification output unit. The first end of the energy storage unit is connected to a positive input port and a different name end of a first primary winding in the high-frequency transformer respectively, the same name end of the first primary winding is connected to the first end of the switching unit, the second end of the switching unit is connected to the first end of the main control unit and the first end of the sampling unit respectively, the second end of the sampling unit is connected to the different name end of a second primary winding in the high-frequency transformer unit and the first end of the VCC power supply soft switching unit respectively, the same name end of the second primary winding is connected to a negative input port, the second end of the energy storage unit and the second end of the VCC power supply soft switching unit respectively, the same name end of a secondary winding in the high-frequency transformer unit is connected to the first end of the rectification output unit, the different name end of the secondary winding is connected to the second end of the rectification output unit, the output end of the VCC power supply soft switching unit is connected to the input end of the main control unit, and the output end of the main control unit is connected to the control end of the switching unit. When the VCC power supply soft switching unit is turned on, the energy stored in the rectification output unit is transmitted to the second primary winding through the VCC power supply soft switching unit to realize reverse excitation, negative current is generated in the first primary winding and the second primary winding, and the switching unit realizes zero voltage turn-on.

2. The winding multiplexing soft-switching flyback circuit of claim 1, wherein: The energy storage unit comprises a first capacitor, the first end of the first capacitor is connected to a positive input port and the different name end of the first primary winding respectively, and the second end of the energy storage unit is connected to a negative input port, the same name end of the second primary winding and the second end of the VCC power supply soft switching unit respectively.

3. The winding multiplexing soft-switching flyback circuit of claim 1, wherein: The main control unit comprises a control chip, the CS sampling pin of the control chip is connected to the second end of the switching unit and the first end of the sampling unit respectively, the power supply pin of the control chip is connected to the output end of the VCC power supply soft switching unit, the driving pin of the control chip is connected to the control end of the switching unit, and the IC ground pin of the control chip is connected to a ground end.

4. The winding multiplexing soft-switching flyback circuit of claim 1, wherein: The switching unit comprises a first switch tube, the first end of the first switch tube is connected to the same name end of the first primary winding, the second end of the first switch tube is connected to the first end of the main control unit and the first end of the sampling unit respectively, and the control end of the first switch tube is connected to the output end of the main control unit.

5. The winding multiplexing soft-switching flyback circuit of claim 1, wherein: The sampling unit comprises a first resistor, the first end of the first resistor is connected to the second end of the switching unit and the first end of the main control unit respectively, and the second end of the first resistor is connected to the different name end of the second primary winding in the high-frequency transformer unit and the first end of the VCC power supply soft switching unit respectively.

6. The winding multiplexing soft-switching flyback circuit of claim 1, wherein: The VCC power supply soft switching unit comprises a second switch tube and a second capacitor, the first end of the second capacitor is connected to the opposite end of the second primary winding and the second end of the sampling unit respectively, the first end of the second switch tube is connected to the second end of the second capacitor and the input end of the master control unit respectively, and the second end of the second switch tube is connected to the negative input port, the second end of the energy storage unit and the same end of the second primary winding respectively.

7. The winding multiplexing soft-switching flyback circuit of claim 1, wherein: The VCC power supply soft switching unit comprises a second capacitor, a first diode and an auxiliary switch, the first end of the second capacitor is connected to the opposite end of the second primary winding and the second end of the sampling unit respectively, the cathode of the first diode is connected to the second end of the second capacitor and the input end of the master control unit respectively, the anode of the first diode is connected to the negative input port, the second end of the energy storage unit and the same end of the second primary winding respectively, and the auxiliary switch is connected in parallel with the first diode.

8. The winding multiplexing soft-switching flyback circuit of claim 1, wherein: The rectified output unit comprises a second diode and a third capacitor, the anode of the second diode is connected to the same end of the secondary winding, the cathode of the second diode is connected to the opposite end of the secondary winding through the third capacitor, the positive pole of the third capacitor is connected to the positive output port, and the negative pole of the third capacitor is connected to the negative output port.

9. The winding multiplexing soft-switching flyback circuit of claim 1, wherein: The sampling unit comprises a current transformer, the first end of the current transformer is connected to the second end of the switching unit and the first end of the master control unit respectively, and the second end of the current transformer is connected to the opposite end of the second primary winding of the high-frequency transformer unit and the first end of the VCC power supply soft switching unit.

10. The winding multiplexing soft-switching flyback circuit of claim 1, wherein: The master control unit comprises a single-chip microcomputer, the sampling end of the single-chip microcomputer is connected to the second end of the switching unit and the first end of the sampling unit respectively, the power supply end of the single-chip microcomputer is connected to the output end of the VCC power supply soft switching unit, the driving end of the single-chip microcomputer is connected to the control end of the switching unit, and the grounding end pin of the single-chip microcomputer is connected to the ground end.

11. The winding multiplexing soft-switching flyback circuit of claim 1, wherein: Further comprising a fourth capacitor and a third switch tube, the first end of the fourth capacitor is connected to the positive input port, the second end of the fourth capacitor is connected to the first end of the third switch tube, and the second end of the third switch tube is connected to the same end of the first primary winding. The VCC power supply soft switching unit comprises a second capacitor and a first diode, the first end of the second capacitor is connected to the opposite end of the second primary winding and the second end of the sampling unit respectively, the anode of the first diode is connected to the negative input port, the second end of the energy storage unit and the same end of the second primary winding respectively, and the cathode of the first diode is connected to the second end of the second capacitor and the input end of the master control unit.

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