CN203435182U - Staggered parallel flyback LED driving power supply and PFM control circuit thereof - Google Patents

Abstract

The utility model discloses a staggered parallel flyback LED driving power supply and a PFM control circuit thereof. A main circuit of the driving power supply is formed by staggering and parallel connection of two flyback converters, and comprises an alternating-current input end, an EMI filter, a bridge rectifier, the two parallel flyback converters, an output rectifier and an LED load. By the aid of the staggered parallel main circuit structure, current stress of switching tubes is reduced, input and output current ripple is reduced, the EMI filter design is simplified, power level of the driving power supply is increased, and the like. A PFM control method is adopted in the control circuit of the driving power supply; compared with a common PWM control method, the PFM control method has the advantages that by the aid of the PFM control circuit, the driving power supply can change in switching tube turning-on time and switching frequency simultaneously when the load changes, working loss during light load of the driving power supply is reduced, and power supply efficiency is improved. The driving power supply is suitable for applications of an LED driving power supply with an automatic dimming function.

Description

A kind of crisscross parallel inverse-excitation type LED driving power and PFM control circuit thereof

Technical field

The utility model belongs to power electronics applied technical field, is specifically related to a kind of crisscross parallel inverse-excitation type LED driving power and PFM control circuit thereof, is applicable to especially LED driving power application of Switching Power Supply.

Background technology

Switching Power Supply is modern society's requisite power electronic equipment of living, and it all has a very wide range of applications in fields such as electronics, communication, electric, the energy, illumination, Aero-Space, military affairs and household electrical appliances.Along with further developing of power electronic technology, the volume of society to Switching Power Supply, reliability, cost, the requirement of the aspects such as energy-conserving and environment-protective further improves, increasingly mature along with LED lighting technology in recent years, LED driving power becomes the focus of research, simultaneously increasing country and tissue have been put into effect a series of policies and regulations and have been come specification switch power supply market, " Energy Star " solid-state illumination files specify that for example USDOE issues: the LED driving power of any power grade must possess power factor emendation function, to test and Safety Approval etc. by EMI simultaneously.

At present, the topological structure such as Switching Power Supply generally adopts normal shock, flyback, recommend, wherein flyback topological structure is because it is simple in structure, can realize input and output isolation, and has power factor emendation function and in being widely used in lower powered Switching Power Supply.LED driving power is widely used two kinds of topological structures, a kind of is single stage type flyback topological structure, the second is two-stage type structure (power factor correction stage and DC/DC conversion stage), but the shortcoming such as complex structure, required components and parts are more, high expensive that two-stage type structure exists, and single stage type flyback topological structure can not be applied to powerful occasion, along with the increase of power, single-stage inverse-excitation type driving power there will be the series of problems such as switch stress becomes greatly, output stability variation, EMI increase, current ripples increase.Simultaneously current most of Switching Power Supply adopts PWM to control, and under the certain condition of frequency, regulates duty ratio to carry out the break-make of control switch pipe, certainly exists and when underloading, because switching frequency is constant, cause very large switching loss under this control mode.Due to above a series of problem, people have to seek other LED driving power circuit topological structure and control method thereof.

Summary of the invention

The deficiency that the utility model exists in actual use for existing LED driving power, as shortcomings such as switch stress are large, power supply EMI is large, current ripples is large, power source life is short, propose a kind of crisscross parallel inverse-excitation type LED driving power and PFM control circuit thereof, make driving power in performance, obtain very large optimization.

The utility model adopts following technical scheme:

Inverse-excitation type LED driving power and a PFM control circuit thereof, the main power circuit of driving power adopts two-way anti exciting converter crisscross parallel; The control circuit of driving power adopts PFM control circuit.

Described main power circuit comprises interchange input, EMI filtering, rectifier bridge, capacitor C _iN, the single-stage anti exciting converter of two-way parallel connection, rectifier diode D5, rectifier diode D6, output capacitance C _out, sampling resistor R and LED load, first via single-stage anti exciting converter comprises transformer T1 and switching tube Q1; The second road anti exciting converter comprises transformer T2 and switching tube Q2; Civil power exchanges input process EMI filtering again through rectifier bridge, and the positive pole of rectifier bridge output connects capacitor C _iNarmature winding one end of one end, transformer T1 and transformer T2, the drain electrode of the other end connecting valve pipe Q1 of transformer T1 armature winding, the source class of switching tube Q1 connects capacitor C _iNthe other end after be connected with the negative pole of rectifier bridge output; One end of transformer T1 secondary winding connects the positive pole of rectifier diode D5, negative pole, the output capacitance C of the negative pole of rectifier diode D5 and rectifier diode D6 _outone end and one end of LED load be connected, the other end of transformer T1 secondary winding and output capacitance C _outone end and the output ground end of the other end, sampling resistor R be connected, the other end of sampling resistor R is connected with the other end of LED load; The drain electrode of the other end connecting valve pipe Q2 of transformer T2 armature winding, the source class of switching tube Q2 connects rectifier bridge output negative pole; One end of transformer T2 secondary winding connects the positive level of output rectifier diode D6, and the other end of transformer T2 secondary winding connects output ground end.

Described PFM control circuit comprises feedback circuit, sampled voltage V ₁, sampled voltage V _rEF, controlled current source aI ₁, constant-current source I ₂, constant-current source I ₃, switch M1, switch M2, capacitor C 1, capacitor C 2, voltage stabilizing didoe D _z, three voltage comparators, two rest-set flip-flops, divider resistance R1, d type flip flop DFF1, two and door, not gate and double switch tube drive circuit; Feedback circuit is by optical coupler, resistance R _fminand resistance R _fmaxform, output current feedback sample connects the light emitting stage of optical coupler, optical coupler receiver stage ground end ground connection, its other end and resistance R _fmaxone end be connected, resistance R _fmaxthe other end and resistance R _fminone end be connected, resistance R _fminother end ground connection, resistance R _fmaxand resistance R _fminpoint and sampled voltage V are connected ₁be connected; Controlled current source aI ₁positive terminal connects sampled voltage V _rEF, negative pole connects constant-current source I ₂positive pole, constant-current source I ₂negative pole connecting valve M1, switch M1 other end ground connection, one end of capacitor C 1 connects current source I ₂positive pole, connect the positive input terminal of voltage comparator COM1 and the negative input end of voltage comparator COM2 simultaneously, the other end ground connection of capacitor C 1, the output of voltage comparator COM1, voltage comparator COM2 connects respectively S end and the R end of rest-set flip-flop SR1, the break-make of the driving stage control switch of the Q output connecting valve M1 of rest-set flip-flop SR1; The negative input end of voltage comparator COM3 connects controlled current source aI ₁negative pole and one end of divider resistance R1, the other end ground connection of divider resistance R1; The positive input terminal of voltage comparator COM3 connects voltage stabilizing didoe D _znegative electrode, one end of capacitor C 2, one end of switch M2, constant-current source I ₃negative pole, voltage stabilizing didoe D _zanode and the other end of capacitor C 2, the other end of switch M2 is connected and ground connection, constant-current source I ₃positive pole connect sampled voltage V _rEF; The output of voltage comparator COM3 connects the R end of rest-set flip-flop SR2, and the S end of rest-set flip-flop SR2 connects the driving stage of output and the switch M2 of voltage comparator COM2 simultaneously; The Q output of rest-set flip-flop SR2 connect with one end of door AND1, with door one end of AND2 and the CP of d type flip flop DFF1 end, the D input of d type flip flop DFF1 and its

output is connected, and the Q output of DFF1 connects the other end and the not gate input with door AND1, and non-gate output terminal connects the other end with door AND2, two with output be connected respectively the grid that connects respectively two switching tubes after double switch tube drive circuit.

Compared with prior art, the utlity model has following beneficial effect:

(1) the utility model can effectively reduce the current stress of switching tube, and system works frequency has increased by one times, and input, output current ripple obviously reduce, and simplifies EMI design, improves power density.

(2) two anti exciting converters of the utility model are operated in DCM pattern, and driving power can obtain High Power Factor and low THD value in full voltage range.

(3) the utility model is in parallel by two-way anti exciting converter, can effectively improve output power of power supply grade, can be applied in more powerful application scenario.

(4) the PFM control circuit the utility model proposes, ON time and the switching frequency that can realize switching tube change with load variations simultaneously, and realize power supply increases ON time, reduces switching frequency when underloading, reduces switching loss, improves power-efficient.

Accompanying drawing explanation

A kind of crisscross parallel inverse-excitation type of Fig. 1 LED driving power main power circuit figure;

A kind of crisscross parallel inverse-excitation type of Fig. 2 LED driving power PFM control circuit figure;

Fig. 3 control circuit oscillogram.

Embodiment

Below in conjunction with accompanying drawing, the utility model is further described.

Referring to Fig. 1, be main power circuit figure of the present utility model, electric main input connects the rectifier bridge consisting of diode D1, D2, D3, D4 through electromagnetic interface filter, its anodal output is armature winding one end of connection transformer T1, T2 respectively, the drain electrode of the other end connecting valve pipe Q1 of transformer T1 armature winding, the source class of switching tube Q1 connects the negative pole of rectifier bridge; One end of transformer T1 secondary winding connects the sun level of output rectifier diode D5, the negative electrode of output rectifier diode D5 and negative electrode, the output capacitance C of output rectifier diode D6 _outone end and one end of LED load be connected, the other end of transformer T1 secondary winding and output capacitance C _outone end and the output ground end of the other end, sampling resistor R be connected, the other end of sampling resistor R is connected with the other end of LED load; The drain electrode of the other end connecting valve pipe Q2 of transformer T2 armature winding, the source class of switching tube Q2 connects the negative pole of rectifier bridge; One end of transformer T2 secondary winding connects the sun level of output rectifier diode D6, and the other end of transformer T2 secondary winding connects output ground end.

Referring to Fig. 2, be the utility model PFM control circuit figure, Fig. 3 is control circuit oscillogram, below in conjunction with Fig. 2, Fig. 3, specifically describes this control method principle:

Optical coupler in feedback loop receives the output current signal of output current sample circuit, and output current information is fed back to I ₁

$I_1=\frac{V_1}{R_{f\min }}+\frac{V_1-V_{\mathrm{op}}}{R_{f\max }}---\left(1\right)$

Output current I _outlarger, V _opless, I ₁to be larger, controlled current source aI ₁for I ₁a doubly.Suppose at t ₀constantly, switch M1 conducting, and constant-current source I ₂much larger than controlled current source aI ₁, now capacitor C 1 repid discharge, the voltage drop on C1 is during to V3, voltage comparator COM2 moment is exported high level, now rest-set flip-flop SR1 resets, SR2 set, turn-offs after switch M2 transient switching, after capacitor C 2 sparks by constant-current source I ₃charging, the Q output output low level of rest-set flip-flop SR1, switch M1 turn-offs, and SR2 exports high level, and d type flip flop DFF1 exports high level, with door AND1 output high level, switching tube Q1 conducting; Because switch M1 turn-offs, M2 turn-offs, controlled current source aI ₁give capacitor C 1 charging, constant-current source I ₃give capacitor C 2 chargings; t ₁voltage in capacitor C 2 rises to V constantly _r1(V _r1by resistance R 1 dividing potential drop, obtained) time, voltage comparator COM3 exports high level, and rest-set flip-flop SR2 resets, the Q end output low level of SR2, AND1 output low level, switching tube Q1 turn-offs, ON time T _onas shown in the formula

$T_{\mathrm{on}}=C_2\frac{{V_R}_1}{I_3}=C_2\frac{{\mathrm{aI}}_1\·R_1}{I_3}---\left(2\right)$

Q1 closes the capacitor C 1 of having no progeny, C2 continues charging, t ₂capacitor C 1 is charged to V2 constantly, now voltage comparator COM1 output high level, so rest-set flip-flop SR1 set, the Q end output high level of SR1, switch M1 conducting again, capacitor C 1 repid discharge is to V3, repeat a cycle, voltage comparator COM2 moment is exported high level, the Q end output low level of rest-set flip-flop SR1, switch M1 turn-offs, capacitor C 1 charging, SR2 set simultaneously, existence due to d type flip flop, AND1 is output low level still, and AND2 exports high level, switching tube Q2 conducting.When capacitor C 1 discharges into V3 rapidly from V2 again, comparator C OM2 is moment output high level again, now Q1 conducting again, and switching tube Q1, Q2 alternate conduction thus, switch periods is the capacitor C twice in 1 charging interval,

$T_L=2C_1\·\frac{V_2-V_3}{{\mathrm{aI}}_1}---\left(3\right)$

From formula (2), (3)

$T_{\mathrm{on}}=2C_1\·C_2\·R_1\·\frac{V_2-V_3}{I_3}\·f_L=m\·f_L---\left(4\right)$

From above formula, ON time is proportional to switching frequency, when driving power is operated in different load conditions, and I ₁oN time different switching tube change corresponding to switching frequency, during the work of driving power underloading, the main power loss of power supply is switching loss, now electric current I ₁less, ON time, the switching frequency of switching tube are less, thereby reduce switching loss; Electric current I during the fully loaded work of driving power ₁larger, switching tube ON time, switching frequency are large, driving power working stability, and output current ripple is little.

Claims (3)

1. crisscross parallel inverse-excitation type LED driving power and a PFM control circuit thereof, is characterized in that, the main power circuit of driving power adopts two-way anti exciting converter crisscross parallel; The control circuit of driving power adopts PFM control circuit.

2. a kind of crisscross parallel inverse-excitation type LED driving power according to claim 1 and PFM control circuit thereof, is characterized in that, described main power circuit comprises interchange input, EMI filtering, rectifier bridge, capacitor C _iN, the single-stage anti exciting converter of two-way parallel connection, rectifier diode D5, rectifier diode D6, output capacitance C _out, sampling resistor R and LED load, first via single-stage anti exciting converter comprises transformer T1 and switching tube Q1; The second road anti exciting converter comprises transformer T2 and switching tube Q2;

Civil power exchanges input process EMI filtering again through rectifier bridge, and the positive pole of rectifier bridge output connects capacitor C _iNarmature winding one end of one end, transformer T1 and transformer T2, the drain electrode of the other end connecting valve pipe Q1 of transformer T1 armature winding, the source class of switching tube Q1 connects capacitor C _iNthe other end after be connected with the negative pole of rectifier bridge output; One end of transformer T1 secondary winding connects the positive pole of rectifier diode D5, negative pole, the output capacitance C of the negative pole of rectifier diode D5 and rectifier diode D6 _outone end and one end of LED load be connected, the other end of transformer T1 secondary winding and output capacitance C _outone end and the output ground end of the other end, sampling resistor R be connected, the other end of sampling resistor R is connected with the other end of LED load;

The drain electrode of the other end connecting valve pipe Q2 of transformer T2 armature winding, the source class of switching tube Q2 connects rectifier bridge output negative pole; One end of transformer T2 secondary winding connects the positive level of output rectifier diode D6, and the other end of transformer T2 secondary winding connects output ground end.

3. a kind of crisscross parallel inverse-excitation type LED driving power according to claim 1 and 2 and PFM control circuit thereof, is characterized in that, described PFM control circuit comprises feedback circuit, sampled voltage V ₁, sampled voltage V _rEF, controlled current source aI ₁, constant-current source I ₂, constant-current source I ₃, switch M1, switch M2, capacitor C 1, capacitor C 2, voltage stabilizing didoe D _z, three voltage comparators, two rest-set flip-flops, divider resistance R1, d type flip flop DFF1, two and door, not gate and double switch tube drive circuit;

Feedback circuit is by optical coupler, resistance R _fminand resistance R _fmaxform, output current feedback sample connects the light emitting stage of optical coupler, optical coupler receiver stage ground end ground connection, its other end and resistance R _fmaxone end be connected, resistance R _fmaxthe other end and resistance R _fminone end be connected, resistance R _fminother end ground connection, resistance R _fmaxand resistance R _fminpoint and sampled voltage V are connected ₁be connected;

Controlled current source aI ₁positive terminal connects sampled voltage V _rEF, negative pole connects constant-current source I ₂positive pole, constant-current source I ₂negative pole connecting valve M1, switch M1 other end ground connection, one end of capacitor C 1 connects current source I ₂positive pole, connect the positive input terminal of voltage comparator COM1 and the negative input end of voltage comparator COM2 simultaneously, the other end ground connection of capacitor C 1, the output of voltage comparator COM1, voltage comparator COM2 connects respectively S end and the R end of rest-set flip-flop SR1, the break-make of the driving stage control switch of the Q output connecting valve M1 of rest-set flip-flop SR1;

The negative input end of voltage comparator COM3 connects controlled current source aI ₁negative pole and one end of divider resistance R1, the other end ground connection of divider resistance R1; The positive input terminal of voltage comparator COM3 connects voltage stabilizing didoe D _znegative electrode, one end of capacitor C 2, one end of switch M2, constant-current source I ₃negative pole, voltage stabilizing didoe D _zanode and the other end of capacitor C 2, the other end of switch M2 is connected and ground connection, constant-current source I ₃positive pole connect sampled voltage V _rEF; The output of voltage comparator COM3 connects the R end of rest-set flip-flop SR2, and the S end of rest-set flip-flop SR2 connects the driving stage of output and the switch M2 of voltage comparator COM2 simultaneously; The Q output of rest-set flip-flop SR2 connect with one end of door AND1, with door one end of AND2 and the CP of d type flip flop DFF1 end, the D input of d type flip flop DFF1 and its

output is connected, and the Q output of DFF1 connects the other end and the not gate input with door AND1, and non-gate output terminal connects the other end with door AND2, two with output be connected respectively the grid that connects respectively two switching tubes after double switch tube drive circuit.

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