WO2018107618A1

WO2018107618A1 - Pfc and llc resonance-based smart full bridge correction wave voltage conversion circuit

Info

Publication number: WO2018107618A1
Application number: PCT/CN2017/079184
Authority: WO
Inventors: 廖志刚
Original assignee: 广东百事泰电子商务股份有限公司
Priority date: 2016-12-15
Filing date: 2017-04-01
Publication date: 2018-06-21
Also published as: CN106787793A

Abstract

A power-factor correction (PFC) and LLC resonance-based smart full bridge correction wave voltage conversion circuit, comprising: an input rectifying unit (10); a filtering unit (20); a PFC boosting unit (30); an LLC isolating converter unit (40), comprising a first switch tube (Q6), a second switch tube (Q7), a first flyback diode (D6), a second flyback diode (D5), a transformer (T1), a resonant capacitor (C4), and a discharging resistor (R2B); a drain of the first switch tube (Q6) is connected to an output terminal of the PFC boosting unit (30), while a source of the first switch tube (Q6) is connected to a first terminal of the transformer (T1), a second terminal of the transformer (T1) being connected to a front end ground by means of the resonant capacitor (C4); a drain of the second switch tube (Q7) is connected to the source of the first switch tube (Q6), while a source of the second switch tube (Q7) is connected to the front end ground by means of the discharging resistor (R2B), and a center tap of a secondary side winding of the transformer (T1) acts as an output terminal of the LLC isolating converter unit (40). The voltage conversion circuit may increase the power factor (PF) value of a voltage conversion device, improve the quality of output voltage, and achieve the effects of safety, reliability, and the like.

Description

Intelligent full bridge modified wave voltage conversion circuit based on PFC and LLC resonance

Technical field

The invention relates to a voltage conversion circuit, in particular to an intelligent full bridge correction wave voltage conversion circuit based on PFC and LLC resonance.

Background technique

In the prior art, the intelligent buck-boost conversion device from AC to AC is also called a travel strip. In this device, the PFC, LLC and full-bridge modified wave voltage conversion circuit topology is its key circuit, which is a kind of realization. The AC-AC conversion circuit can realize the function of buck-boost and stabilize voltage and frequency in AC-AC conversion. However, most of the current AC-AC portable device market is a non-isolated topology circuit with low PF value, low output voltage quality, and poor safety and reliability.

Summary of the invention

The technical problem to be solved by the present invention is to provide an intelligent full-bridge modified wave voltage conversion circuit based on PFC and LLC resonance for improving the PF value of the voltage conversion device and improving the output voltage quality, and the prior art. Get safe and reliable results.

In order to solve the above technical problems, the present invention adopts the following technical solutions.

An intelligent full-bridge modified wave voltage conversion circuit based on PFC and LLC resonance, comprising: an input rectifying unit, wherein an input end is connected to a power grid for rectifying a grid voltage; and a filtering unit is connected to the input rectifying unit The output end is used for filtering the voltage outputted by the input rectifying unit; a PFC boosting unit is connected to the output end of the filtering unit for boosting the voltage outputted by the filtering unit; and an LLC isolation converter unit, including a first switch tube, a second switch tube, a first freewheeling diode, a second freewheeling diode, a transformer, a resonant capacitor and a discharge resistor, wherein a drain of the first switch tube is connected to an output end of the PFC boost unit, a source of the first switch is connected to a first end of the transformer, a second end of the transformer is connected to the front end through a resonant capacitor, and a drain of the second switch is connected to a source of the first switch. The source of the second switch tube is connected to the front end through a discharge resistor, and the gate of the first switch tube and the gate of the second switch tube are used to load two PWM pulse signals with opposite phases The first switch tube and the second switch tube are alternately turned on, the first end of the transformer secondary winding is connected to the anode of the first freewheeling diode, and the second end of the transformer secondary winding is connected to An anode of the second freewheeling diode, a cathode of the first freewheeling diode and a cathode of the second freewheeling diode are connected to a rear end, and an intermediate tap of the secondary winding of the transformer serves as an output of the LLC isolated converter unit; a DC voltage filtering unit includes a first electrolytic capacitor, and an anode of the first electrolytic capacitor is connected to the LLC An output terminal of the isolating converter unit, a negative electrode of the first electrolytic capacitor is connected to a rear end; an inverter inverting unit is connected to an output end of the LLC isolating converter unit, and the inverter inverting unit is used for the LLC The output voltage of the isolated converter unit is inverted and converted to output alternating current.

Preferably, a first pull-down resistor is connected between the gate and the source of the first switch.

Preferably, a second pull-down resistor is connected between the gate and the source of the second switch.

Preferably, the filtering unit comprises a filtering capacitor connected between the output end of the input rectifying unit and the front end ground.

Preferably, the PFC boosting unit includes a boosting inductor, a third switching transistor, a first rectifier diode and a second electrolytic capacitor, and a front end of the boosting inductor is connected to an output end of the filtering unit, the boosting inductor The back end is connected to the drain of the third switch tube, the source of the third switch tube is connected to the front end, and the gate of the third switch tube is used to access a PWM control signal, the third switch tube The drain is connected to the anode of the first rectifier diode, the cathode of the first rectifier diode is used as the output end of the PFC boosting unit, and the cathode of the first rectifier diode is connected to the anode of the second electrolytic capacitor, and the cathode of the second electrolytic capacitor Connect to the front end.

Preferably, a third pull-down resistor is connected between the gate of the third switch tube and the front end ground.

Preferably, an MCU control unit is further included, the gate of the first switch tube, the gate of the second switch tube and the gate of the third switch tube are respectively connected to the MCU control unit, and the MCU control unit is used for respectively The PWM signal is output to the first switch tube, the second switch tube and the third switch tube to control the on/off state of the first switch tube, the second switch tube and the third switch tube.

Preferably, the method further includes an AC sampling unit connected between the input end of the input rectifying unit and the MCU control unit, wherein the AC sampling unit is configured to collect the voltage of the AC side of the input rectifying unit and feed back to the MCU control. unit.

Preferably, a first sampling resistor is connected between the source and the front end of the third switching transistor, and a source of the third switching transistor is connected to the MCU control unit, and the MCU is used by the first sampling resistor. The control unit collects an electrical signal of the source of the third switching transistor.

Preferably, the method further includes a DC voltage sampling unit, the DC voltage sampling unit includes a second sampling resistor and a third sampling resistor connected in series, and a front end of the second sampling resistor is connected to an output of the LLC isolation converter unit. The back end of the third sampling resistor is connected to the MCU control unit, and the MCU control unit acquires an electrical signal of the output of the LLC isolated converter unit by the second sampling resistor and the third sampling resistor.

In the intelligent full-bridge modified wave voltage conversion circuit based on PFC and LLC resonance disclosed in the present invention, the grid voltage is rectified by the input rectifying unit, and then filtered by the filtering unit to output the pulsating DC voltage, and then the PFC is utilized. The boosting unit boosts the pulsating DC voltage. In the LLC isolating converter unit, the first switching transistor, the second switching transistor, the resonant capacitor, the discharge resistance and the leakage inductance of the primary side of the transformer and the primary exciting inductance constitute LLC resonance. a circuit, and transferring power to the secondary winding of the transformer during state transition of the LLC resonant circuit, rectifying into a unidirectional ripple level by the first freewheeling diode and the second freewheeling diode, by changing the primary winding of the transformer The turns ratio can adjust the level of the output voltage to achieve step-up or step-down conversion. Based on the above structure, the present invention not only realizes the isolated transmission of voltage, but also improves the PF value of the step-up/step-down conversion device, and also improves the output voltage quality, making the voltage conversion process more secure and reliable.

DRAWINGS

1 is a schematic diagram of a full bridge modified wave voltage conversion circuit of the present invention.

2 is a circuit schematic diagram of an AC sampling unit in a preferred embodiment of the present invention.

3 is a circuit schematic diagram of an MCU control unit in a preferred embodiment of the present invention.

detailed description

The invention will now be described in greater detail with reference to the drawings and embodiments.

The invention discloses an intelligent full bridge correction wave voltage conversion circuit based on PFC and LLC resonance, which is combined with FIG. 1 to FIG. 3 and includes:

An input rectifying unit 10, the input end of which is connected to the power grid for rectifying the grid voltage;

a filtering unit 20 is connected to the output end of the input rectifying unit 10 for filtering the voltage output by the input rectifying unit 10;

a PFC boosting unit 30 is connected to the output end of the filtering unit 20 for boosting and converting the voltage output by the filtering unit 20;

An LLC isolation converter unit 40 includes a first switching transistor Q6, a second switching transistor Q7, a first freewheeling diode D6, a second freewheeling diode D5, a transformer T1, a resonant capacitor C4, and a discharging resistor R2B. The drain of a switch Q6 is connected to the output of the PFC boost unit 30. The source of the first switch Q6 is connected to the first end of the transformer T1, and the second end of the transformer T1 is connected through the resonant capacitor C4. The front end of the second switch tube Q7 has a drain connected to the source of the first switch tube Q6, and the source of the second switch tube Q7 is connected to the front end through a discharge resistor R2B, the first switch tube Q6 The gates of the gates and the second switching transistors Q7 are used to load two PWM pulse signals of opposite phases to alternately conduct the first switching transistor Q6 and the second switching transistor Q7, and the secondary winding of the transformer T1 The first end is connected to the anode of the first freewheeling diode D6, the second end of the secondary winding of the transformer T1 is connected to the anode of the second freewheeling diode D5, the cathode of the first freewheeling diode D6 and the second continuation The cathodes of the flow diode D5 are all connected to the back end, The intermediate tap of the secondary winding of the transformer T1 serves as the output of the LLC isolated converter unit 40;

a DC voltage filtering unit 50 includes a first electrolytic capacitor C3, an anode of the first electrolytic capacitor C3 is connected to an output end of the LLC isolation converter unit 40, and a cathode of the first electrolytic capacitor C3 is connected to a rear end;

An inverter inverting unit 70 is connected to the output end of the LLC isolating converter unit 40, and the inverter inverting unit 70 is configured to invert and convert the output voltage of the LLC isolating converter unit 40 to output an alternating current.

In the full bridge correction wave voltage conversion circuit, the grid voltage is rectified by the input rectifying unit 10, and then filtered by the filtering unit 20 to output a pulsating DC voltage, and then the PFC boosting unit 30 is used to boost the pulsating DC voltage. In the LLC isolating converter unit 40, the first switching transistor Q6, the second switching transistor Q7, the resonant capacitor C4, the discharging resistor R2B and the primary side of the transformer T1 and the primary exciting inductance constitute an LLC resonant circuit, and in the LLC resonance During the state transition of the circuit, the power is transmitted to the secondary winding of the transformer T1, and is rectified into a unidirectional ripple level by the first freewheeling diode D6 and the second freewheeling diode D5, by changing the number of turns of the primary and secondary windings of the transformer T1. In comparison, the output voltage can be adjusted to achieve boost or buck conversion. Based on the above structure, the present invention not only realizes the isolated transmission of voltage, but also improves the PF value of the step-up/step-down conversion device, and also improves the output voltage quality, making the voltage conversion process more secure and reliable.

In this embodiment, in order to increase the switching speed of the first switching transistor Q6 and the second switching transistor Q7, a first pull-down resistor R25 is connected between the gate and the source of the first switching transistor Q6. A second pull-down resistor R26 is connected between the gate and the source of the second switching transistor Q7.

As a preferred mode, the filtering unit 20 includes a filtering capacitor C1 connected between the output end of the input rectifying unit 10 and the front end ground.

Further, the PFC boosting unit 30 includes a boosting inductor L2, a third switching transistor Q5, a first rectifier diode D1, and a second electrolytic capacitor C2. The front end of the boosting inductor L2 is connected to the output of the filtering unit 20. The back end of the boosting inductor L2 is connected to the drain of the third switching transistor Q5, the source of the third switching transistor Q5 is connected to the front end, and the gate of the third switching transistor Q5 is used for accessing. a PWM control signal, the drain of the third switching transistor Q5 is connected to the anode of the first rectifier diode D1, the cathode of the first rectifier diode D1 is the output terminal of the PFC boosting unit 30, and the first rectifier diode D1 The cathode is connected to the positive electrode of the second electrolytic capacitor C2, and the negative electrode of the second electrolytic capacitor C2 is connected to the front end.

In the PFC boosting unit 30, when the C1 output half-wave AC voltage is detected, the PFC enters the boost mode to improve the PF value of the AC-to-AC intelligent buck conversion topology circuit, and the voltage after the boosting is C2 filtered. 400V. The specific boosting principle is as follows: When Q5 is turned on, the current on C1 forms a loop through the boost inductors L2 and Q5 to GND, and the boost inductor L2 stores energy; when Q5 is turned off, the boost inductor forms a specific input voltage. a much higher induced electromotive force, The induced electromotive force is rectified by the freewheeling tube D1 to form a unidirectional pulse voltage and then sent to the C2 capacitor for filtering, and filtered into a DC voltage of 400V. Q5 is based on the input AC sine wave change taken by the MCU control unit 80 to increase or decrease the on-time of Q5, so that the current and voltage phases are consistent to increase the PF value.

In this embodiment, in order to increase the switching speed of the third switching transistor Q5, a third pull-down resistor R22 is connected between the gate of the third switching transistor Q5 and the front end ground.

As a preferred manner, the embodiment further includes an MCU control unit 80. The gate of the first switch Q6, the gate of the second switch Q7, and the gate of the third switch Q5 are respectively connected to the MCU control. The unit 80, the MCU control unit 80 is configured to respectively output PWM signals to the first switch tube Q6, the second switch tube Q7 and the third switch tube Q5 to control the first switch tube Q6, the second switch tube Q7 and the third unit The switch tube Q5 is on and off. Further, the MCU control unit 80 includes a single chip U1 and its peripheral circuits.

In order to facilitate the monitoring of the electrical signal on the AC side, the embodiment further includes an AC sampling unit 90, the AC sampling unit 90 is connected between the input end of the input rectifying unit 10 and the MCU control unit 80, and the AC sampling unit 90 is used. The voltage on the AC side of the input rectification unit 10 is collected and fed back to the MCU control unit 80.

Regarding the specific composition of the AC sampling unit 90, the AC sampling unit 90 includes an operational amplifier U9B, and two input ends of the operational amplifier U9B are respectively connected to an input end of the input rectifying unit 10 through a current limiting resistor, The output of the operational amplifier U9B is connected to the MCU control unit 80.

In order to facilitate real-time acquisition of the current, a first sampling resistor R2A is connected between the source and the front end of the third switching transistor Q5, and the source of the third switching transistor Q5 is connected to the MCU control unit 80. The first sampling resistor R2A causes the MCU control unit 80 to collect an electrical signal of the source of the third switching transistor Q5.

As a preferred manner, in order to collect the DC side electrical signal, the embodiment further includes a DC voltage sampling unit 60, and the DC voltage sampling unit 60 includes a second sampling resistor R13 and a third sampling resistor R15 connected in series. The front end of the second sampling resistor R13 is connected to the output end of the LLC isolation converter unit 40, and the rear end of the third sampling resistor R15 is connected to the MCU control unit 80, and the second sampling resistor R13 and the The three-sampling resistor R15 causes the MCU control unit 80 to acquire an electrical signal at the output of the LLC isolated converter unit 40.

Regarding the inverter portion, the inverter inverter unit 70 includes an inverter bridge composed of a fourth switching transistor Q1, a fifth switching transistor Q2, a sixth switching transistor Q3, and a seventh switching transistor Q4, and the fourth switching transistor The gate of Q1, the gate of the fifth switching transistor Q2, the gate of the sixth switching transistor Q3, and the gate of the seventh switching transistor Q4 are respectively connected to the MCU control unit 80, and are controlled by the MCU control unit 80. The four switching transistors Q1, the fifth switching transistor Q2, the sixth switching transistor Q3, and the seventh switching transistor Q4 are turned on or off to cause the inverter inverting unit 70 to output an alternating voltage.

In the inverter inverter unit 70, the DC voltage filtered by C3 is looped through Q1, load, and Q4. The load supply forms the first half cycle power frequency level; the second half cycle power frequency level forms a loop through Q2, load, and Q3, thus forming a complete power frequency correction wave AC voltage on the load. The PWM signal outputted by the control chip U1 is sent to the GATE poles of Q1, Q2, Q3, and Q4 by the PWM1H, PWM1L, PWM2H, and PWM2L through the driving circuit. The phase and frequency in the inverter inverter circuit operate in accordance with the mode set in the control chip.

The invention discloses an intelligent full-bridge modified wave voltage conversion circuit based on PFC and LLC resonance, which is compared with the prior art. Firstly, the invention has a high PF value, realizes isolation between the power grid and the output end, and has high security. At the same time, the output voltage can be automatically adjusted within the input full voltage range, and the output frequency is fixed. Again, the output voltage is a modified wave output, and the AC voltage has an automatic shaping function. In addition, the present invention includes a voltage and current sampling circuit. It can prevent surge voltage and current.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. All modifications, equivalents, and improvements made within the technical scope of the present invention are intended to be included within the scope of the present invention.

Claims

An intelligent full-bridge modified wave voltage conversion circuit based on PFC and LLC resonance, characterized in that it comprises:

An input rectifying unit, the input end of which is connected to the power grid for rectifying the grid voltage;

a filtering unit is connected to the output end of the input rectifying unit for filtering the voltage output by the input rectifying unit;

a PFC boosting unit is connected to the output end of the filtering unit for boosting and converting the voltage output by the filtering unit;

An LLC isolated converter unit includes a first switching transistor, a second switching transistor, a first freewheeling diode, a second freewheeling diode, a transformer, a resonant capacitor and a discharge resistor, and a drain of the first switching transistor is connected to An output end of the PFC boosting unit, a source of the first switching tube is connected to a first end of the transformer, a second end of the transformer is connected to the front end through a resonant capacitor, and a drain of the second switching tube is connected to a source of the first switching transistor, a source of the second switching transistor is connected to the front end through a discharge resistor, and a gate of the first switching transistor and a gate of the second switching transistor are used to load two PWMs with opposite phases And a pulse signal, wherein the first switch tube and the second switch tube are alternately turned on, the first end of the transformer secondary winding is connected to the anode of the first freewheeling diode, and the second end of the transformer secondary winding Connected to the anode of the second freewheeling diode, the cathode of the first freewheeling diode and the cathode of the second freewheeling diode are connected to the rear end, and the center tap of the secondary winding of the transformer serves as the output of the LLC isolated converter unit end;

a DC voltage filtering unit includes a first electrolytic capacitor, an anode of the first electrolytic capacitor is connected to an output end of the LLC isolation converter unit, and a cathode of the first electrolytic capacitor is connected to a rear end;

An inverter inverting unit is connected to an output end of the LLC isolating converter unit, and the inverter inverting unit is configured to invert and convert an output voltage of the LLC isolated converter unit to output an alternating current.
The intelligent full-bridge modified wave voltage conversion circuit based on PFC and LLC resonance according to claim 1, wherein a first pull-down resistor is connected between a gate and a source of the first switching transistor.
The intelligent full-bridge modified wave voltage conversion circuit based on PFC and LLC resonance according to claim 1, wherein a second pull-down resistor is connected between the gate and the source of the second switching transistor.
The intelligent full-bridge modified wave voltage conversion circuit based on PFC and LLC resonance according to claim 1, wherein the filtering unit comprises a filter capacitor, and the filter capacitor is connected to the output end and the front end of the input rectifying unit. between.
The intelligent full-bridge modified wave voltage conversion circuit based on PFC and LLC resonance according to claim 1, wherein the PFC boosting unit comprises a boosting inductor, a third switching transistor, a first rectifier diode, and a second An electrolytic capacitor, a front end of the boosting inductor is connected to an output end of the filtering unit, a rear end of the boosting inductor is connected to a drain of the third switching transistor, and a source of the third switching transistor is connected to the front end The gate of the third switching transistor is used to access a PWM control signal, the drain of the third switching transistor is connected to the anode of the first rectifier diode, and the cathode of the first rectifier diode is used as the output terminal of the PFC boosting unit. And the cathode of the first rectifier diode is connected to the anode of the second electrolytic capacitor, and the second electrolytic battery The negative pole of the capacitor is connected to the front end.
The intelligent full-bridge modified wave voltage conversion circuit based on PFC and LLC resonance according to claim 5, wherein a third pull-down resistor is connected between the gate of the third switching transistor and the front end ground.
The intelligent full-bridge modified wave voltage conversion circuit based on PFC and LLC resonance according to claim 5, further comprising an MCU control unit, a gate of the first switch tube, and a gate of the second switch tube And the gates of the third switch tube are respectively connected to the MCU control unit, wherein the MCU control unit is configured to respectively output PWM signals to the first switch tube, the second switch tube and the third switch tube to control the first switch tube, The two switching tubes and the third switching tube are in an on-off state.
The intelligent full-bridge modified wave voltage conversion circuit based on PFC and LLC resonance according to claim 7, further comprising an AC sampling unit connected to the input end of the input rectifying unit and the MCU control unit The AC sampling unit is configured to collect the voltage of the AC side of the input rectifying unit and feed back to the MCU control unit.
The intelligent full-bridge modified wave voltage conversion circuit based on PFC and LLC resonance according to claim 7, wherein a first sampling resistor is connected between a source and a front end of the third switching transistor, The source of the three-switching transistor is connected to the MCU control unit, and the MCU control unit collects the electrical signal of the source of the third switching transistor by the first sampling resistor.
The intelligent full-bridge modified wave voltage conversion circuit based on PFC and LLC resonance according to claim 7, further comprising a DC voltage sampling unit, wherein the DC voltage sampling unit comprises a second sampling resistor connected in series and a third sampling resistor, a front end of the second sampling resistor is connected to an output end of the LLC isolation converter unit, a rear end of the third sampling resistor is connected to the MCU control unit, and the second sampling resistor and the third The sampling resistor causes the MCU control unit to acquire an electrical signal at the output of the LLC isolated converter unit.