CN214544119U - Buck type single-switch multi-path constant-current output switch converter - Google Patents

Abstract

The utility model provides a Buck type single switch multichannel constant current output switch converter. The front-stage buck PFC converter and the rear-stage DC-DC current-sharing converter are integrated together through a single switch. In a half power frequency period, the on-time of the switching tube in each switching period is controlled to be basically unchanged, so that the input current changes in a sine trend along with the input voltage, the power factor correction is further realized, and the harmonic content of the input current is reduced. The rear-stage DC-DC unit realizes multi-path current sharing by utilizing a resonance capacitor charge-discharge balance principle. The integrated structure not only reduces the number of the switching tubes and simplifies the control circuit, but also effectively balances the input power and the output power, improves the dynamic response characteristic of the converter through fast loop control and reduces output ripples.

Description

Buck type single-switch multi-path constant-current output switch converter

Technical Field

The utility model relates to a LED driver field, the output that specially adapted multichannel flow equalizes and require to be higher to the electric current ripple, need realize that LED does not have stroboscopic occasion of work.

Background

High-brightness light-emitting diodes (HB-LEDs) are widely used in the production and life of people, because they have the advantages of high efficiency, fast response speed, wide color gamut, small volume, long service life, high brightness, etc. in place of traditional cold light lamps and incandescent lamps. Meanwhile, the International Electrotechnical Commission (IEC) has a series of requirements for the harmonics of the input current of the lighting device. In order to meet the requirements of IEC61000-3-2ClassC, LED driving Power supplies with Power Factor Correction (PFC) converter units are widely used.

Fig. 1 shows a conventional single-stage conversion active PFC circuit including Boost, Buck-Boost, Flyback, and the like. The LED driver formed by the single-stage active PFC has the advantages of high electric energy conversion efficiency, small size, light weight and the like on the basis of realizing power factor correction and output current regulation. However, because instantaneous energy imbalance exists between the ac input and the dc output, the output current of the single-stage LED driver includes a double power frequency ripple, so that the LEDs have a stroboscopic phenomenon. The LED stroboscopic phenomenon can threaten human health.

In view of the above problem, fig. 2 shows a structural block diagram of a two-stage conversion active PFC converter. The two-stage conversion active PFC mainly comprises a front-stage PFC converter and a rear-stage DC-DC converter which are cascaded. The front-stage PFC converter mainly comprises the Boost, Buck-Boost, Flyback and other basic single-stage PFC converters, and is used for shaping input current and realizing high power factor. The rear-stage DC-DC converter takes the output of the front-stage PFC converter as the input thereof, and carries out direct current conversion on the output of the front stage so as to realize output voltage or current with high quality, low output ripple and quick dynamic response. The LED driving power supply formed by the two-stage conversion structure can realize the non-stroboscopic work of the LED, but because the two-stage active PFC converter is provided with two converters and needs two switching tubes, two sets of control systems respectively control the PFC stage and the DC-DC stage, the circuit structure is complex, the control is complex, and the cost is high. In addition, because the two-stage active PFC converter performs power conversion twice, the converter has low efficiency, and the application of the converter is limited.

Disclosure of Invention

The utility model discloses adopt integrated structure to above-mentioned problem, with preceding stage buck PFC converter and back level resonant mode DC-DC converter that flow equalizes through the single switch integration together. Compared with the traditional single-stage PFC converter, the LED drive circuit can effectively restrain output current ripples and realize non-stroboscopic work of the LED. Compared with the traditional two-stage PFC converter, the number of switching tubes is reduced, the control circuit is simplified, the switching loss is reduced, and the manufacturing cost is reduced.

In order to solve the technical problem, the utility model discloses a technical scheme is:

the Buck type single-switch multi-path constant-current output switch converter is characterized in that the power circuit main components of the Buck type single-switch multi-path constant-current output switch converter are as follows: IIPole tube rectifier bridge, input filter inductorL _fInput filter capacitorC _fPower switch tubeS ₁Free wheeling diodeD _B1、D _B2、D _B3InductanceL _B、L _mCapacitorC _BResonant capacitor C_r1、C_r2And an output capacitorC _o1、C _o2、C_o3；

The input filter circuit adopts an inverted L structure and a filter inductorL _fAn input filter capacitor connected in series with the main circuitC _fIs connected in parallel to the rectifier bridgeD _bAndL _fan output terminal of (a); buck inductanceL _BOne end of which is connected to the freewheeling diodeD _B2AndL _f another end is connected with the capacitorC _BThe positive electrode of (1); active switchS ₁Is connected to the diode rectifier bridgeD _bThe drain electrode of the lower output end is connected withL _mAnd a freewheeling diodeD _B2The gate of the transistor is connected to the control loop; capacitor with a capacitor elementC _BIs connected to the positive stageL _BOne end of the negative electrode is connected with the output diodeD _B2Cathode andD _B3between the anodes; resonance capacitorC _r1Is connected with one end toL _mSecondary side and output freewheel diodeD ₃Is connected with an output diode D₁An anode andD ₂between the cathodes; resonant capacitor C_r2One end of the capacitor is connected to the output capacitorC _o2AndC _o3one end of the cathode is connected with the output capacitorC _o1The negative electrode of (1); load connected in parallel to output capacitorC _o1、C _o2、C _o3Two ends; the front-stage Buck converter and the rear-stage resonant multi-path constant current converter pass through the inductorL _mAnd (4) connecting.

Fig. 3 is an integrated BuckLED driver main power circuit. The main power circuit is composed of diode rectifier bridgeD _bInput filter inductorL _fInput filter capacitorC _fBuck PFC unit andand the resonant DC-DC unit. The Buck PFC unit consists of an inductorL _BFreewheel diodeD _kB[] (k = 1, 2, 3) and energy storage capacitorC _BAnd (4) forming. The resonant DC-DC unit is composed of a resonant capacitorC _ir[] (i= 1, 2, 3), freewheeling diodeD _i[] (i= 1, 2, 3), filter capacitanceC _io[] (i= 1, 2, 3) and transformerTAnd (4) forming. In a half power frequency period, the on-time of the switching tube in each switching period is controlled to be basically unchanged, so that the input current changes in a sine trend along with the input voltage, the power factor correction is further realized, and the harmonic content of the input current is reduced. The rear-stage DC-DC unit realizes multi-path current sharing by utilizing a resonance capacitor charge-discharge balance principle.

Fig. 4 is an integrated buck led driver voltage mode control loop consisting of an error amplifier, a zero current detection circuit, a comparator, a triangle generator, an RS trigger, and a gate drive circuit. Output currenti _o1Is controlled toV _ref/R _sWhereinR _sIs an electric currenti _o1The sampling resistance of (a) is set,V _refis the reference voltage of the control loop. After receiving the zero-crossing detection signal, the controller generates a setting pulse to set and output the RS triggerQ ₁The switching tube is turned on, and simultaneously the triangular wave generator linearly rises from zero with a fixed slope. The error comparator is used for sampling the signalV _rsAnd a reference signalV _refComparing to generate an error signalv _eWhen a triangular wave signalu _sawGreater than the error signalv _eWhen the switch tube is turned off, a reset signal is generated, and the switch tube is turned off. The output current is controlled at a set value by controlling the on and off of the switching tube. Meanwhile, the fast loop speed improves the dynamic response characteristic of the converter, and reduces the output current ripple.

Compared with the prior art, the beneficial effects of the utility model are that: the front-stage PFC unit and the rear-stage resonant multi-path output unit are integrated together through the single switch, so that the number of switching tubes is reduced, and a control circuit is simplified. Meanwhile, the integrated structure can effectively balance input and output power, the dynamic response characteristic of the converter is improved through fast loop control, and output ripples are reduced.

Drawings

Fig. 1 shows a single-stage conversion active Power Factor Correction (PFC) circuit.

Fig. 2 is a block diagram of a two-stage conversion active PFC converter.

Fig. 3 is an integrated single-switch multi-channel current-sharing stroboflash-free LED driver main power circuit.

Fig. 4 is an integrated single-switch multi-channel current-sharing strobe-free LED driver control circuit.

Fig. 5 is a waveform diagram of input voltage and input current within a half power frequency period.

FIG. 6 is a waveform diagram of an input voltage and an input current experiment when the input voltage is 220V.

Fig. 7 is a waveform diagram of the voltage and current of the resonant capacitor and the output diode in one switching period.

Fig. 8 is a waveform diagram of an output current when an input voltage is 220V.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

The LED has the advantages of high luminous efficiency, wide color gamut, long service life, small volume and the like, and is widely used for replacing the traditional cold cathode fluorescent lamp and incandescent lamp. In order to reduce harmonic pollution of power electronic equipment to a power grid, the standards of IEC61000-3-2Class C and the like provide limitation requirements for each harmonic current of input current of the power electronic equipment. Therefore, it is of great significance to research the low-output ripple LED driving power supply with power factor correction.

Fig. 5 is a waveform diagram of input voltage and input current within a half power frequency period. In the figure,. mu.lv _inI is the rectified input voltage instantaneous value,V _Bis a capacitorC _BThe voltage of (a) is set to be,V _pkin order to be the peak value of the input voltage,i _pkin order to input the peak value of the current,i _{in_av}is the average value of the input current,θin order to turn on the triggering angle,βin order to obtain a conduction angle of the conductive paste,L _Bfor the inductance of the BuckPFC,T _sin order to be the switching period of the switch,t _onthe on-time of the switch tube is the on-time of the switch tube,Dis the duty cycle.

The average value of the input current obtained from the waveform of fig. 6 is as follows:

(1)

according to the formula, the average value of the input current changes in a sine trend along with the input voltage when the conduction time of the switching tube is unchanged in a half power frequency period.

FIG. 6 is a waveform diagram of an experiment of 220V AC input voltage and input current. The utility model discloses a can realize the power factor correction function from the picture.

Fig. 7 is a waveform diagram of the resonant capacitor and the output diode in one switching period.T _sIn order to be the switching period of the switch,t _onthe on-time of the switch tube is the on-time of the switch tube,t _offthe turn-off time of the switching tube;v _cr1is a resonant capacitorC _cr1The voltage of (a) is set to be,v _cr2is a resonant capacitorC _cr2Voltage of, Δv _cr1、Δv _cr2Are respectively asC _cr1、C _cr2Voltage variation in one switching period;i _cr1is a resonant capacitorC _cr1The resonant current of (a) is set,i _cr2is a resonant capacitorC _cr2The resonant current of (a) is set,Q _1ch、Q _2chthe amount of charge stored for the resonant capacitor,Q _1dis、Q _2disthe amount of charge released for the resonant capacitor;i _D1、i _D2、i _D3to output the current of the diode.

According to the charge-discharge balance principle of the capacitor, the charge quantity stored when the capacitor is charged in one switching period is equal to the charge quantity released when the capacitor is discharged, and then:

(2)

resonance capacitorC _cr1Through the output diodeD ₁Charging through an output diodeD ₂The discharge, during one switching cycle,

(3)

i _D1-avgandi _D2-avgare respectively asD ₁ AndD ₂average current over one switching period.

Because the output capacitor is large enough, the voltage of the output capacitor is kept constant in a half power frequency period, and the output current isi _o1、i _o2Andi _o3respectively equal to the output diodeD ₁、D ₂AndD ₃average value of the current of (1). Therefore, the temperature of the molten metal is controlled,

(4)

the same can be obtainedi _o2Is equal toi _o3Therefore, the multi-path output realizes current sharing.

Fig. 8 is a waveform diagram of the output current at the input voltage of 220Vac, and the three output currents are balanced at the moment of starting. The measured output current ripple is only 15mA, and the LED non-stroboscopic work can be realized.

Claims (1)

1. A Buck type single-switch multi-path constant-current output switch converter is characterized in that a power loop of the Buck type single-switch multi-path constant-current output switch converter comprises the following main components: diode rectifier bridge, input filter inductorL _fInput filter capacitorC _fPower switch tubeS ₁Free wheeling diodeD _B1、D _B2、D _B3InductanceL _B、L _mCapacitorC _BResonant capacitor C_r1、C_r2And an output capacitorC _o1、C _o2、C_o3；

The input filter circuit adopts an inverted L structure and a filter inductorL _fAn input filter capacitor connected in series with the main circuitC _fIs connected in parallel to the rectifier bridgeD _bAndL _fan output terminal of (a); buck inductanceL _BOne end of which is connected to the freewheeling diodeD _B2AndL _f another end is connected with the capacitorC _BThe positive electrode of (1); active switchS ₁Is connected to the diode rectifier bridgeD _bThe drain electrode of the lower output end is connected withL _mAnd a freewheeling diodeD _B2The gate of the transistor is connected to the control loop; capacitor with a capacitor elementC _BIs connected to the positive stageL _BOne end of the negative electrode is connected with the output diodeD _B2Cathode andD _B3between the anodes; resonance capacitorC _r1Is connected with one end toL _mSecondary side and output freewheel diodeD ₃Is connected with an output diode D₁An anode andD ₂between the cathodes; resonant capacitor C_r2One end of the capacitor is connected to the output capacitorC _o2AndC _o3one end of the cathode is connected with the output capacitorC _o1The negative electrode of (1); load connected in parallel to output capacitorC _o1、C _o2、C _o3Two ends; the front-stage Buck converter and the rear-stage resonant multi-path constant current converter pass through the inductorL _mAnd (4) connecting.

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