High-frequency bridge type synchronous rectification circuit

Abstract

The utility model discloses a high frequency bridge type synchronous rectification circuit, comprising an LLC high frequency transformer, synchronous rectification chips, a first MOS tube, a second MOS tube and a resonance capacitor, the synchronous rectification chips comprise a first synchronous rectification chip, a second synchronous rectification chip, a third synchronous rectification chip and a fourth synchronous rectification chip; the first synchronous rectification chip, the second synchronous rectification chip, the third synchronous rectification chip and the fourth synchronous rectification chip are arranged in a full-bridge structure and are arranged on the secondary side of the LLC high-frequency transformer; the first MOS transistor, the second MOS transistor and the resonant capacitor are arranged on the primary side of the LLC high-frequency transformer, the first MOS transistor and the second MOS transistor are connected in series, and the second MOS transistor and the resonant capacitor are connected in parallel. The synchronous rectification chip integrated with the MOS is adopted to replace a rectification diode, the problem of loss during rectification under high current is solved, and meanwhile, compared with an existing transformer, the high-frequency transformer can reduce one winding.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of switching power supply circuit, especially relates to a high frequency bridge type synchronous rectification circuit. BACKGROUND

[0002] The development of modern electronic technology makes the working voltage of the circuit lower and the current larger and larger, for example, the fast charging technology adopted by the mobile phone manufacturers needs to increase the current under the environment of as low voltage as possible to improve the charging power of the fast charging plug.

[0003] In the case of low voltage and large current output, the conduction voltage drop of the rectifier diode is high, and the loss of the output rectifier tube is particularly prominent, for example, the current required by a 65W switching power supply under a 3.3V power supply voltage is nearly 20A, at this time, the SRD diode rectification loss is close to 50% of the power output, and the traditional diode rectification circuit cannot meet the needs of low voltage, large current switching power supply high efficiency and small size.

[0004] In the prior art, the secondary winding of the LLC topology high-frequency transformer generally adopts full-wave rectification, which is composed of two diodes, as shown in the following formula: Figure 1 As the demand for energy saving and environmental protection increases, the power conversion efficiency is required to be higher and higher while ensuring low voltage, and the use of diode rectification will increase the rectification loss and reduce the power efficiency.

[0005] Synchronous rectification is a technology that uses a special power MOSFET with extremely low on-resistance to replace the rectifier diode to reduce the rectification loss.

[0006] The on-resistance of the MOSFET is only mΩ, if the on-resistance of the MOSFET is 4mΩ, the on-resistance is 80mV when the current of 20A is turned on, and the use of MOSFET as a rectifier will greatly improve the output efficiency of the low-voltage and large-current converter and improve the power efficiency.

[0007] As disclosed in Chinese patent CN103997223B, a synchronous rectification driving circuit, the circuit uses a MOS tube instead of a rectifier diode at the secondary side of the transformer to reduce the rectification loss, but the MOS tube is used for accurate switching control of the MOS tube, and the base of the MOS tube needs to be connected to an additional driving chip to drive the switching of the MOS tube, or a source voltage acquisition circuit and a conversion circuit are added to accurately control the switching of the MOS tube. In this way, the electrical elements in the circuit are increased, and the circuit size and use cost are increased. Utility model content

[0008] The utility model discloses a high frequency bridge type synchronous rectification circuit, adopt integrated MOS's synchronous rectification chip instead of rectifier diode, solve the problem of loss when rectifying under high current, and the synchronous rectification chip integrated MOS brings the advantages of peripheral circuit simplification and ultra-low cost, and simultaneously high frequency transformer can reduce a winding relative to the existing transformer, and it is favorable to reduce transformer cost and improve power conversion efficiency.

[0009] The utility model discloses a high frequency bridge type synchronous rectification circuit, adopt integrated MOS's synchronous rectification chip instead of rectifier diode, solve the problem of loss when rectifying under high current, and the synchronous rectification chip integrated MOS brings the advantages of peripheral circuit simplification and ultra-low cost, and simultaneously high frequency transformer can reduce a winding relative to the existing transformer, and it is favorable to reduce transformer cost and improve power conversion efficiency.

[0010] The first synchronous rectification chip, the second synchronous rectification chip, the third synchronous rectification chip and the fourth synchronous rectification chip are arranged in full-bridge structure and are arranged on the secondary side of the LLC high frequency transformer.

[0011] The first MOS tube, the second MOS tube and the resonance capacitor are arranged on the primary side of the LLC high frequency transformer.

[0012] The utility model discloses a further setting that the first synchronous rectification chip's drain electrode and the second synchronous rectification core's drain electrode are connected and serve as the positive output end, and the third synchronous rectification chip's source electrode and the fourth synchronous rectification chip's source electrode are connected and serve as the negative output end.

[0013] The utility model discloses a further setting that the first synchronous rectification chip's drain electrode and the second synchronous rectification core's drain electrode are connected and serve as the positive output end, and the third synchronous rectification chip's source electrode and the fourth synchronous rectification chip's source electrode are connected and serve as the negative output end.

[0014] The utility model discloses a further setting that the first MOS tube and the second MOS tube are connected in series, and the second MOS tube and the resonance capacitor are connected in parallel.

[0015] The utility model discloses a further setting that the first MOS tube and the second MOS tube are connected in series, and the second MOS tube and the resonance capacitor are connected in parallel.

[0016] The utility model discloses a further setting that the first MOS tube and the second MOS tube are connected in series, and the second MOS tube and the resonance capacitor are connected in parallel.

[0017] The utility model discloses further provide: the synchronous rectification chip is built -in MOS pipe, and synchronous rectification chip is integrated drive.

[0018] The utility model discloses further provide: the synchronous rectification chip model is KP42261 or same type specification model.

[0019] The utility model discloses further provide: first synchronous rectification chip, second synchronous rectification chip, third synchronous rectification chip and fourth synchronous rectification chip are same model or same type specification model.

[0020] The utility model discloses further provide: the base of first MOS pipe and second MOS pipe is connected drive control chip.

[0021] Compared with prior art, the utility model has following beneficial effects: 1, this circuit utilizes low -voltage MOS pipe m omega level's on -resistance characteristic greatly reduced the on -resistance loss, 3, synchronous rectification chip replaces rectifier diode and solves the loss heating problem caused by diode PN junction voltage reduction, 3, while transformer can reduce a winding and be favorable to reduce transformer cost, 4, synchronous rectification chip integrates MOS and simplifies peripheral circuit, reduces circuit area, and has obvious cost advantage. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is prior art diode rectifier circuit schematic diagram.

[0023] Figure 2 It is high frequency bridge type synchronous rectification circuit schematic diagram in embodiment.

[0024] In the drawing: 100, LLC high frequency transformer, 101, first synchronous rectification chip, 102, second synchronous rectification chip, 103, third synchronous rectification chip, 104, fourth synchronous rectification chip, 105, secondary winding first end, 106, secondary winding tail end, 107, primary winding first end, 108, primary winding tail end, 109, first MOS pipe, 110, second MOS pipe, 111, resonance capacitor. DETAILED DESCRIPTION

[0025] The technical scheme in the embodiments of the utility model will be described clearly and completely below with reference to the drawings in the embodiments of the utility model; Obviously, the described embodiments are only part of the embodiments of the utility model, not all the embodiments, based on the embodiments in the utility model, all other embodiments obtained by the ordinary skill in the art without creative labor belong to the protection scope of the utility model.

[0026] As Figure 2As shown, the embodiment discloses a high-frequency bridge synchronous rectification circuit, which adopts a bridge synchronous rectification scheme to solve the problem of diode loss when rectifying under high current of a high-frequency transformer, and the high-frequency transformer can reduce one winding compared with an existing transformer, which is conducive to reducing the cost of the transformer and improving the power conversion efficiency.

[0027] The high-frequency bridge synchronous rectification circuit comprises an LLC high-frequency transformer 100 and synchronous rectification chips, wherein the synchronous rectification chips comprise a first synchronous rectification chip 101, a second synchronous rectification chip 102, a third synchronous rectification chip 103 and a fourth synchronous rectification chip 104; the synchronous rectification chips are internally provided with MOSFETs, and the first synchronous rectification chip 101, the second synchronous rectification chip 102, the third synchronous rectification chip 103 and the fourth synchronous rectification chip 104 are arranged in a full-bridge structure and are arranged at a secondary side of the LLC high-frequency transformer 100.

[0028] As shown in the Figure 2 LLC high-frequency transformer 100 at the secondary side, the first synchronous rectification chip 101 is connected to the source of the third synchronous rectification chip 103, and the tail end 106 of the secondary side winding of the LLC high-frequency transformer 100 is connected to the source of the second synchronous rectification chip 102 and the drain of the fourth synchronous rectification chip 104; the drain of the first synchronous rectification chip 101 and the drain of the second synchronous rectification chip are connected and serve as a positive output end, and the source of the third synchronous rectification chip 103 and the source of the fourth synchronous rectification chip 104 are connected and serve as a negative output end.

[0029] As shown in the Figure 2 LLC high-frequency transformer 100 at the primary side, the first MOS tube 109 is connected to the source of the second MOS tube 110, and the tail end 108 of the primary side winding of the LLC high-frequency transformer 100 is connected to one pole of the resonant capacitor 111; the other pole of the resonant capacitor 111 is connected to a grounding point GND, the drain of the first MOS tube 109 is connected to a power supply end, and the source of the second MOS tube 110 is connected to the grounding point GND.

[0030] The synchronous rectification chip is integrated with MOSFET, and the synchronous rectification chip drives rectification output by using the MOSFET; the source and the base of the MOSFET in the synchronous rectification chip are connected; meanwhile, the synchronous rectification chip is integrated with filter elements, so that peripheral circuit elements can be simplified.

[0031] The synchronous rectification chip in the embodiment adopts a synchronous rectification chip of model KP42261 or a synchronous rectification chip of the same type and specification, and the first synchronous rectification chip 101, the second synchronous rectification chip 102, the third synchronous rectification chip 103 and the fourth synchronous rectification chip 104 are of the same model or the same type and specification, wherein the synchronous rectification chips of the same type and specification can be mixed.

[0032] When the LLC high-frequency transformer 100 is input with low-voltage and high-frequency alternating voltage on the primary side, the LLC high-frequency transformer 100 simultaneously outputs voltage on the secondary side, and the voltage range can be between several volts and tens of volts. The output voltage can be reduced according to the primary and secondary coil turn ratio of the LLC high-frequency transformer 100, and then a suitable bias voltage MOSFET is selected according to different voltages. The output alternating voltage can be a square wave or a sine wave or a similar square wave or a trapezoidal wave and the like.

[0033] When the input voltage of the LLC high-frequency transformer 100 is a forward waveform in time sequence, the Vsg of the MOSFET in the first synchronous rectification chip 101 is forward biased, the first synchronous rectification chip 101 is turned on and output, and in the return flow, the Vsg of the MOSFET in the fourth synchronous rectification chip 104 is forward biased, the fourth synchronous rectification chip 104 is turned on and input, and the LLC high-frequency transformer 100 forms a loop.

[0034] When the input voltage of the LLC high-frequency transformer 100 is a reverse waveform in time sequence, the Vsg of the MOSFET in the third synchronous rectification chip 103 is forward biased, the third synchronous rectification chip 103 is turned on and output, and in the return flow, the Vsg of the MOSFET in the second synchronous rectification chip 102 is forward biased, the second synchronous rectification chip 102 is turned on and input, and the LLC high-frequency transformer 100 forms a loop.

[0035] The bases of the first MOS tube 109 and the second MOS tube 110 are respectively connected with a drive control chip, the drive control chip outputs a drive signal, and the MOS tube and the synchronous rectification chip group are complementary turned on and turned off. When the current flows from the load loop to the primary loop, the MCU receives the current signal and the voltage signal, and calculates and processes to send a control signal with a set frequency, a duty cycle and a certain dead zone. The control signal is converted into a drive signal by a drive circuit, and the MOS tube and the synchronous rectification tube group are complementary turned on and turned off.

[0036] The above only describes a preferred embodiment of the present application, and equivalent changes or modifications made according to the structure, features and principles described in the patent application range of the present application are included in the patent application range of the present application.

Claims

1. A high-frequency bridge synchronous rectification circuit, characterized in that: The invention comprises an LLC high-frequency transformer (100), a synchronous rectification chip, a first MOS transistor (109), a second MOS transistor (110) and a resonant capacitor (111); the synchronous rectification chip comprises a first synchronous rectification chip (101), a second synchronous rectification chip (102), a third synchronous rectification chip (103) and a fourth synchronous rectification chip (104); The first synchronous rectifier chip (101), the second synchronous rectifier chip (102), the third synchronous rectifier chip (103) and the fourth synchronous rectifier chip (104) are arranged in a full-bridge structure and are provided on the secondary side of the LLC high-frequency transformer (100); The first MOS transistor (109), the second MOS transistor (110) and the resonant capacitor (111) are arranged on the primary side of the LLC high-frequency transformer (100).

2. The high-frequency bridge synchronous rectification circuit according to claim 1, characterized in that: The secondary winding head end (105) of the LLC high-frequency transformer (100) is connected to the source of the first synchronous rectifier chip (101) and the drain of the third synchronous rectifier chip (103), and the secondary winding tail end (106) of the LLC high-frequency transformer (100) is connected to the source of the second synchronous rectifier chip (102) and the drain of the fourth synchronous rectifier chip (104).

3. The high-frequency bridge synchronous rectification circuit according to claim 2, characterized in that: The drain of the first synchronous rectifier chip (101) and the drain of the second synchronous rectifier core are connected and serve as a positive output terminal, and the source of the third synchronous rectifier chip (103) and the source of the fourth synchronous rectifier chip (104) are connected and serve as a negative output terminal.

4. The high-frequency bridge synchronous rectification circuit according to claim 1, wherein: The first MOS transistor (109) and the second MOS transistor (110) are connected in series, and the second MOS transistor (110) and the resonant capacitor (111) are connected in parallel.

5. The high-frequency bridge synchronous rectification circuit according to claim 4, characterized in that: The primary side winding head end (107) of the LLC high-frequency transformer (100) is respectively connected to the source of the first MOS transistor (109) and the drain of the second MOS transistor (110); the primary side winding tail end (108) of the LLC high-frequency transformer (100) is connected to one pole of the resonant capacitor (111), and the other pole of the resonant capacitor (111) is connected to a ground point.

6. The high-frequency bridge synchronous rectification circuit according to claim 5, characterized in that: The drain of the first MOS transistor (109) is connected to a power supply terminal, the source of the first MOS transistor (109) is connected to the drain of the second MOS transistor (110), and the source of the second MOS transistor (110) is connected to a ground point.

7. The high-frequency bridge synchronous rectification circuit according to claim 1, characterized in that: The synchronous rectification chip is integrated with MOSFET.

8. The high-frequency bridge synchronous rectification circuit according to claim 7, characterized in that: The synchronous rectifier chip model is KP42261 or a model of the same type and specification.

9. The high-frequency bridge synchronous rectification circuit according to claim 8, characterized in that: The first synchronous rectification chip (101), the second synchronous rectification chip (102), the third synchronous rectification chip (103) and the fourth synchronous rectification chip (104) are of the same model or the same type and specification.

10. The high-frequency bridge synchronous rectification circuit according to claim 1, characterized in that: The bases of the first MOS transistor (109) and the second MOS transistor (110) are connected to a driving control chip.

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