CN207884928U - A kind of LED constant current constant voltage power supply circuit - Google Patents

Abstract

The utility model discloses a kind of LED constant current constant voltage power supply circuits comprising exchange input rectifying filter circuit, flyback transformer, constant voltage source management circuit, output rectifier and filter and feedback circuit；The constant voltage source management circuit output pwm control signal gives the flyback transformer, it is set to export constant voltage, it powers to LED using output rectifier and filter, the feedback circuit acquires the output voltage of the output rectifier and filter, feed back to the constant voltage source management circuit, it adjusts constant voltage source and manages circuit output pwm control signal, make flyback transformer output constant current constant-voltage power supply.The utility model is without using special current constant control IC, you can realizes constant current constant voltage function, cost is low compared to IC schemes, and circuit is simple, has good economic value.

Description

A kind of LED constant current constant voltage power supply circuit

Technical field

The utility model is related to power technique fields more particularly to a kind of LED constant current constant voltage power supply circuits.

Background technology

The LED power in industry is exported based on constant voltage source with output constant current power supply at present, few to accomplish constant pressure The LED drive power coexisted with constant current, the existing constant voltage constant current power complex circuit coexisted, must use turn constant current constant voltage control IC, and LED is constant current operation device, so having to, using expensive current constant control IC, have in many LED drivers Circuit must increase a group transformer coil and power to constant current IC, increase complicated feedback line.

Utility model content

In order to solve the above-mentioned technical problem, the purpose of this utility model is to provide a kind of LED simple in structure, cost-effective Constant voltage supply circuit.

Technical solution used by the utility model is：A kind of LED constant current constant voltage power supply circuit comprising exchange input is whole Flow filter circuit, flyback transformer, constant voltage source management circuit, output rectifier and filter and feedback circuit, the friendship Stream input rectifying filter circuit output end connect with the input terminal of the flyback transformer, the flyback transformer it is defeated Outlet is connect with the input terminal of the output rectifier and filter, the constant voltage source management circuit and the flyback transformer The input terminal of connection, the output end of the feedback circuit and the constant voltage source management circuit is connect, the feedback circuit it is defeated Enter end to connect with the output end of the output rectifier and filter；The constant voltage source management circuit output pwm control signal is given The flyback transformer makes it export constant voltage, powers to LED using output rectifier and filter, the feedback electricity Road acquires the output voltage of the output rectifier and filter, feeds back to the constant voltage source management circuit, adjusts constant voltage source Circuit output pwm control signal is managed, flyback transformer output constant current constant-voltage power supply is made.

Further, the constant voltage source management circuit includes SD4843 chips and its peripheral circuit.

Further, the feedback circuit includes sampling resistor, divider resistance, triode, optocoupler and zener diode, institute The cathode for stating sampling resistor one end and LED connects, the other end respectively with the negative output terminal of the output rectifier and filter and Divider resistance connects, and the other end of the divider resistance connect with the base stage of the triode, the emitter of the triode and The negative output terminal of the output rectifier and filter connects, and the collector of the triode is connect with 2 feet of the optocoupler, institute 1 foot for stating optocoupler is connect with the positive output end of the flyback transformer, the FB of 4 feet of the optocoupler and the SD4843 chips Foot connects, and 3 feet of the optocoupler are connect with the positive of the zener diode, the cathode of the zener diode with it is described The FB feet of SD4843 chips connect, anode and the negative output terminal for exchanging input rectifying filter circuit of the zener diode Connection.

Further, further include peak absorbing circuit, the peak absorbing circuit includes the second diode, the first radio frequency electrical Resistance, the second radio-frequency resistance and filter capacitor, the anode of the primary coil of the flyback transformer are sequentially connected the second radio frequency Resistance, the first radio-frequency resistance are connect with the negative terminal of second diode, the anode of the diode and the inverse-excitation type transformation The negative terminal of the primary coil of device connects, and the filter capacitor is in parallel with second radio-frequency resistance.

Further, the exchange input rectifying filter circuit includes rectifier bridge and by the first inductance, the second capacitance and second The filter circuit of capacitance composition.

Further, the output rectifier and filter includes third diode, the second inductance and third capacitance, described anti- The positive output end of sharp formula transformer passes sequentially through third diode and the second inductance and is connect with the anode of institute LED, the third electricity Hold one end to connect with the positive output end of the flyback transformer, the other end is connect with the negative terminal of the flyback transformer.

The utility model has the beneficial effects that：The utility model is without using special current constant control IC, you can realizes permanent Pressure-keeping functions are flowed, cost is low compared to IC schemes, and circuit is simple, has good economic value.

Description of the drawings

Specific embodiment of the present utility model is described further below in conjunction with the accompanying drawings：

Fig. 1 is the circuit function module schematic diagram of the utility model；

Fig. 2 is the circuit diagram in one specific embodiment of the utility model.

Specific implementation mode

It should be noted that in the absence of conflict, the features in the embodiments and the embodiments of the present application can phase Mutually combination.

As shown in Figure 1, a kind of LED constant current constant voltage power supply circuit comprising exchange input rectifying filter circuit, inverse-excitation type become Depressor, constant voltage source management circuit, output rectifier and filter and feedback circuit, the exchange input rectifying filter circuit Output end is connect with the input terminal of the flyback transformer, and the output end of the flyback transformer is filtered with the output rectification The input terminal of wave circuit connects, and the constant voltage source management circuit is connect with the flyback transformer, the feedback circuit The input terminal that output end manages circuit with the constant voltage source is connect, and the input terminal of the feedback circuit is filtered with the output rectification The output end of wave circuit connects；The constant voltage source management circuit output pwm control signal gives the flyback transformer, makes it Constant voltage is exported, is powered to LED using output rectifier and filter, the feedback circuit acquires the output rectification filter The output voltage of circuit feeds back to the constant voltage source management circuit, adjusts constant voltage source management circuit output PWM control letters Number, make flyback transformer output constant current constant-voltage power supply.

Embodiment

As shown in Fig. 2, it illustrates a kind of circuit diagrams of LED constant current constant voltage power supply circuit, wherein the constant pressure is electric Power management circuits include SD4843 chips U1 and its peripheral circuit.The Drain feet output PWM controls of the SD4843 chips U1 Signal provides the energy storage exoergic condition of high frequency for flyback transformer T1, and the VCC feet of SD4843 chips U1 are connect with SGND, The 4th resistance R4 and the 5th resistance R5 is parallel between PGND feet and SGND feet, SGND feet pass through the first capacitance C1, third electricity Resistance R3 is connect with the negative terminal of the first diode D1, and the anode of the first diode is connect with the N2 coil anodes of flyback transformer, The N1 that the SGND feet of SD4843 chips U1 pass through the first capacitance C1, second resistance R2, first resistor R1 and flyback transformer U1 The anode HV+ connections of coil.

Feedback circuit includes sampling resistor RS1, divider resistance R13, triode Q12, optocoupler U2 and zener diode The cathode of ZD1, the one end the sampling resistor RS1 and LED connect, and the other end is negative defeated with the output rectifier and filter respectively Outlet and divider resistance R13 connections, the other end of the divider resistance R13 are connect with the base stage of the triode Q12, institute The emitter for stating triode Q12 is connect with the negative output terminal PGND of the output rectifier and filter, the collection of the triode Q12 Electrode is connect with 2 feet of the optocoupler U2, and 1 foot of the optocoupler U2 is connect with the positive output end V+ of the flyback transformer, 4 feet of the optocoupler U2 are connect with the FB feet of the SD4843 chips U1,3 feet and the zener diode of the optocoupler U2 The anode connection of ZD1, the cathode of the zener diode ZD1 are connect with the FB feet of the SD4843 chips U1, the voltage stabilizing two The anode of pole pipe ZD1 is connect with the negative output terminal SGND of the exchange input rectifying filter circuit.

The FB feet of SD4843 chips U1 can will protect (U1 not works there are one maximum voltage value, the maximum value U1 more than FB Make), so zener diode ZD1 is set in the range of FB maximum values.When the pressure drop that LED load is a fixed Vf When, the first sampling resistor RS1 will produce a pressure drop, and the base stage that triode Q12 is divided to by R resistance 14 and resistance R13 generates One fixed Ibe electric current, Ice=Ibe* β, optocoupler U2 accelerates conducting to make SD4843 chips under the action of the pull-down current of Ice For the FB feet clamper of U1 to a fixed value, SD4843 chips U1, which exports a fixed pwm signal, makes flyback transformer T1 store up Energy exoergic is certain value, and output LED load is a fixed current；When LED load Vf voltages are got higher, that is, exports energy and increase Add, since primary current increases the electric current increase on i.e. resistance R4 and resistance R5, SD4843 chips under the action of T1 induction transformations The voltage of the FB feet of U1 can gradually be got higher, while the pressure drop on the first sampling sampling resistor RS1 increases, and Ibe electric currents increase, Ice =Ibe* β increase, and optocoupler U2 conduction amounts increase pulls down to fixed value by the FB of SD4843 chips U1, and output current is allowed to maintain Fixed value；Pressure drop when LED load Vf voltages are lower on the first sampling resistor RS1 can also decline, and Ice current reduces, Ice Also can reduce, optocoupler U2 conduction amounts reduce, the FB feet of its SD4843 chip U1 is made to be discharged into certain value；No matter the pressure drop on LED How to change, the electric current exported on LED is a fixed value always, to realize constant current.

Exchange input rectifying filter circuit includes rectifier bridge DB1 and by the first inductance L1, the electricity of the second capacitance EC 1 and second Hold the filter circuit that EC 2 is formed.

Output rectifier and filter includes third diode D 3, the second inductance L2 and third capacitance EC 3, the flyback The positive output end V+ of formula transformer U1 passes sequentially through third diode D3 and the second inductance L2 is connect with the anode of institute LED, described Third one end capacitance EC3 is connect with the positive output end V+ of the flyback transformer U1, the other end and the flyback transformer The negative terminal of U1 connects.

It is further used as preferred embodiment, further includes peak absorbing circuit, the peak absorbing circuit includes the Two diode D2, the first radio-frequency resistance RF1, the second radio-frequency resistance RF2 and filter capacitor CF1, the flyback transformer U1 The anode HV+ of primary coil be sequentially connected the second radio-frequency resistance RF2, the first radio-frequency resistance RF1 and the second diode D2 Negative terminal connection, the anode of the diode D2 connect with the negative terminal of the primary coil of the flyback transformer U1, the filter Wave capacitance CF1 and 2 resistor coupled in parallel of the second radio frequency

.Since flyback transformer leakage inductance influences, power switch tube can cause due to voltage spikes, therefore the two or two when off Pole pipe D2, the first radio-frequency resistance RF1, the second radio-frequency resistance RF2, filter capacitor CF1 form RCD clamper absorbing circuits.

It is to be illustrated to the preferable implementation of the utility model, but the utility model creation is not limited to institute above State embodiment, those skilled in the art can also make various etc. without departing from the spirit of the present invention It with deformation or replaces, these equivalent deformations or replacement are all contained in the application claim limited range.

Claims (6)

1. a kind of LED constant current constant voltage power supply circuit, it is characterised in that：It includes exchange input rectifying filter circuit, inverse-excitation type change Depressor, constant voltage source management circuit, output rectifier and filter and feedback circuit, the exchange input rectifying filter circuit Output end is connect with the input terminal of the flyback transformer, and the output end of the flyback transformer is filtered with the output rectification The input terminal of wave circuit connects, and the constant voltage source management circuit is connect with the flyback transformer, the feedback circuit The input terminal that output end manages circuit with the constant voltage source is connect, and the input terminal of the feedback circuit is filtered with the output rectification The output end of wave circuit connects；

The constant voltage source management circuit output pwm control signal gives the flyback transformer, it is made to export constant voltage, then It powers to LED by output rectifier and filter, the feedback circuit acquires the output voltage of the output rectifier and filter, The constant voltage source management circuit is fed back to, constant voltage source is adjusted and manages circuit output pwm control signal.

2. LED constant current constant voltage power supply circuit according to claim 1, it is characterised in that：The constant voltage source manages circuit Including SD4843 chips and its peripheral circuit.

3. LED constant current constant voltage power supply circuit according to claim 2, it is characterised in that：The feedback circuit includes sampling The cathode of resistance, divider resistance, triode, optocoupler and zener diode, described sampling resistor one end and LED connect, another End connect respectively with the negative output terminal of the output rectifier and filter and divider resistance, the other end of the divider resistance and The base stage of the triode connects, and the emitter of the triode is connect with the negative output terminal of the output rectifier and filter, The collector of the triode is connect with 2 feet of the optocoupler, the positive output of 1 foot and the flyback transformer of the optocoupler End connection, 4 feet of the optocoupler are connect with the FB feet of the SD4843 chips, 3 feet and the zener diode of the optocoupler Anode connection, the cathode of the zener diode connect with the FB feet of the SD4843 chips, and the zener diode is just Pole is connect with the negative output terminal of the exchange input rectifying filter circuit.

4. LED constant current constant voltage power supply circuit according to claim 1, it is characterised in that：It further includes peak absorbing circuit, The peak absorbing circuit includes the second diode, the first radio-frequency resistance, the second radio-frequency resistance and filter capacitor, the flyback It is negative with second diode that the anode of the primary coil of formula transformer is sequentially connected the second radio-frequency resistance, the first radio-frequency resistance End connection, the anode of the diode connect with the negative terminal of the primary coil of the flyback transformer, the filter capacitor and Second radio-frequency resistance is in parallel.

5. LED constant current constant voltage power supply circuit according to claim 1, it is characterised in that：The exchange input rectifying filtering Circuit includes rectifier bridge and the filter circuit that is made of the first inductance, the second capacitance and the second capacitance.

6. LED constant current constant voltage power supply circuit according to claim 1, it is characterised in that：The output rectifier and filter Including third diode, the second inductance and third capacitance, the positive output end of the flyback transformer passes sequentially through the three or two Pole pipe and the second inductance are connect with the anode of institute LED, the positive output end of third capacitance one end and the flyback transformer Connection, the other end are connect with the negative terminal of the flyback transformer.