CN102711343A

CN102711343A - LED (light emitting diode) lighting driving circuit and electronic equipment

Info

Publication number: CN102711343A
Application number: CN2012102196224A
Authority: CN
Inventors: 王建辉; 代成志
Original assignee: CHENGDU CHIP-RAIL MICROELECTRONIC Co Ltd
Current assignee: CHENGDU CHIP-RAIL MICROELECTRONIC Co Ltd
Priority date: 2012-06-28
Filing date: 2012-06-28
Publication date: 2012-10-03

Abstract

The invention provides an LED (light emitting diode) lighting driving circuit and electronic equipment, belonging to the field of analog circuits. The LED lighting driving circuit is characterized in that two output pins of an optical coupler are respectively connected with a feedback pin fb of a PWM (pulse-width modulation) controller and the ground, a first resistor is connected in parallel between two input pins of the optical coupler, one input pin of the optical coupler is connected with the ground, a second resistor is connected in series between the other input pin of the optical coupler and a first connecting point, a third resistor is connected in series between the ground and the first connecting point, and the first connecting point is a connecting point of the LED lighting driving circuit and a load. The optical coupler is directly utilized for realizing the constant-current LED lighting driving, without additional various constant-current circuits, electrical isolation guarantee safety is realized for input and output, and the circuit is simple in structure and low in cost.

Description

A kind of LED illumination driving circuit and electronic equipment

Technical field

The present invention relates to the Analog Circuit Design field, particularly a kind of LED illumination driving circuit and electronic equipment.

Background technology

Under the background that the worry of current global energy shortage raises once again; Energy savings is the important problem that we shall face future; At lighting field, the application of LED luminous product is just attracting common people's sight, and LED is as a kind of novel green light source product; Must be developing tendency in future, it be the novel illumination light source epoch of representative that 21st century will get into LED.LED be called as the 4th generation lighting source or green light source, have characteristics such as energy-saving and environmental protection, the life-span is long, volume is little, the energy-conservation energy is pollution-free to be environmental protection.More energy-conservation more than 80% in the equal illumination effect than conventional light source.Led light source has person, and it is a long-life lamp, means the lamp that never extinguishes.The solid cold light source, epoxy encapsulation does not have loosening part yet in the lamp body, do not exist filament light-emitting to be prone to shortcomings such as burning, heat deposition, light decay, can reach 60,000 to 100,000 hours useful life, and is longer more than 10 times than the conventional light source life-span.Environmental benefit is better, does not have ultraviolet ray and infrared ray in the spectrum, has not both had heat, does not also have radiation, and dazzle is little, and discarded object is recyclable, does not pollute not contain mercury element, and cold light source can safe touch, belongs to typical green illumination light source.Compare with the illumination effect that conventional light source is dull; Led light source is the low pressure microelectronic product; Computer technology, the network communications technology, image processing techniques, embedded Control technology etc. have successfully been merged; So also be the digital information product, be semiconductor photoelectric device " high-new point " technology, have flexible and changeable characteristics.Can be widely used in fields such as various indications, demonstration, decoration, backlight, general lighting and urban landscape.Ac-powered LED illumination can reduce cost, but voltage ripple of power network can cause the LED overcurrent to drive and influence its useful life, is important so in the occasion of Alternating Current Power Supply LED is carried out constant-current driving.Led drive circuit mainly adopts schemes such as non-isolation Buck step-down scheme, PSR former limit feedback and isolation pulse width modulation (PWM) Switching Power Supply at present.Non-isolation Buck step-down scheme cost is low, but imports and export the electric electrical isolation that do not have, and safety can not be protected, and the former limit of PSR feedback is to transformer requirement height, and the batch process consistency is bad.The PWM Switching Power Supply scheme constant-current circuit main method of LED illumination driving circuit has; The LED operating current is sampled, obtain sampled voltage and reference voltage and compare and enlarge the rear drive optocoupler PWM integrated circuit is carried out close-loop feedback control, this method constant current accuracy is high; But owing to need special-purpose constant-current circuit; Peripheral circuit is complicated, is not easy, and cost is than higher.

This shows in the prior art and exist: the baroque problem of PWM Switching Power Supply scheme constant-current circuit of LED illumination driving circuit.

Summary of the invention

In order to address the above problem; The purpose of the embodiment of the invention provides a kind of LED illumination driving circuit; There are the baroque problem of PWM Switching Power Supply scheme constant-current circuit of LED illumination driving circuit, this LED illumination driving circuit in the solution prior art; Two output pins of optocoupler are connected with ground with the feedback pin fb of pulse width modulation (PWM) controller respectively; Be parallel with first resistance between two input pins of optocoupler, and an input pin of optocoupler is connected with ground, is in series with second resistance between another input pin of optocoupler and first tie point; Between the ground and first tie point, be in series with the 3rd resistance, first tie point is a tie point of LED illumination driving circuit and load.

Further, be parallel with the fb shunt capacitance between the feedback pin fb of PWM controller and the ground.

Further, be parallel with the Zener voltage-stabiliser tube between first tie point and second tie point, second tie point is another tie point of LED illumination driving circuit and load.

Further, two outputs of input rectifying filter circuit are parallelly connected with VDD filter capacitor that is connected in series and starting resistance, and VDD filter capacitor one end is connected with ground, and PWM controller VDD pin links to each other with the tie point of VDD filter capacitor and starting resistance.

Further, primary inductance two ends connect an output of PWM controller drain pin and input rectifying filter circuit respectively, and this output is not connected with ground.

Further, the primary inductance is parallelly connected with the clamped circuit of RCD.

Further, transformer is assisted winding one end ground connection, and the other end links to each other through the tie point of VDD rectifier diode with VDD filter capacitor and starting resistance.

Further, transformer secondary output winding one end connects second tie point, other end ground connection through the output rectifier diode.

Further, the current monitoring end pin cs of PWM controller is through current sample input resistance ground connection.

The embodiment of the invention also provides a kind of electronic equipment, comprises aforesaid LED illumination driving circuit on the body.

Owing to directly utilize optocoupler to realize that the constant-current LED illumination drives, need not add various constant-current circuits, input realizes that with output electrical isolation guarantees safety, and circuit structure is simple, and cost is low.

Description of drawings

Fig. 1 representes LED illumination driving circuit schematic diagram of the present invention.

Embodiment

Carry out detailed explanation below in conjunction with accompanying drawing and embodiment.

Fig. 1 is LED illumination driving circuit figure; 117 two output pins of optocoupler are connected with ground with the feedback pin fb of pulse width modulation (PWM) controller 107 respectively; Be parallel with resistance 116 between 117 two input pins of optocoupler, and an input pin of optocoupler 117 is connected with ground, is in series with resistance 114 between another input pin of optocoupler 117 and the load 111; Between ground and load 111, be in series with current sampling resistor 115, load 111 is connected to first tie point of LED illumination driving circuit during work.Be parallel with fb shunt capacitance 118 between the feedback pin fb of PWM controller 107 and the ground.Be parallel with another tie point that Zener voltage-stabiliser tube 113, the second tie points are LED illumination driving circuit and load 111 between first tie point and second tie point.Two outputs of input rectifying filter circuit 101 and VDD filter capacitor that is connected in series 104 and starting resistance 102 parallel connections; VDD filter capacitor 104 1 ends are connected with ground, and PWM controller 107VDD pin links to each other with the tie point of VDD filter capacitor 104 with starting resistance 103.Transformer 109 primary inductance two ends connect an output of PWM controller 107 drain pin and input rectifying filter circuit 101 respectively, and this output is not connected with ground.The clamped circuit of transformer 109 primary inductances and RCD 108 is parallelly connected.Transformer 109 auxiliary winding one end ground connection, the other end links to each other with the tie point of VDD filter capacitor 104 with starting resistance 102 through VDD rectifier diode 103.Transformer 109 secondary winding one end connects second tie point, other end ground connection through output rectifier diode 110.The current monitoring end pin cs of PWM controller 107 is through current sample input resistance 106 ground connection.String has gate driving power supply input resistance 105 between PWM controller 107VDD pin and the PWM controller 107VDDG pin.

It is initial to power on; AC power is charged through 102 pairs of VDD filter capacitors of starting resistance 104 through input rectifying filter circuit 101; When voltage is higher than chip UVLO_OFF on the VDD filter capacitor 104; PWM controller 107 starts, and sends and enable the conducting of signal triggering internal power switching tube, and the electric current that flows through transformer 109 primary inductances in internal power pipe conduction period flows through CS peak current sampling input resistance 106 with the controlled rate of rise; PWM controller 107 detects the pressure drop that produces on the CS peak current sampling input resistance 106, thereby control internal power switching tube turn-offs; After power tube turn-offs; The crest voltage at 108 pairs of transformers of the clamped circuit of RCD, 109 elementary winding two ends carries out clamped; Transformer 109 secondary winding provide energy through 110 pairs of outputs of output rectifier diode, and transformer 109 auxiliary windings provide energy through 103 couples of VDD of VDD rectifier diode simultaneously; The unlatching VF that optocoupler 117 infrarede emitting diodes own are used in the output constant current is about 1.05V as the reference voltage comparison point, and the voltage on LED load 111 current sampling resistors 115 surpasses the VF voltage of optocoupler 117 infrarede emitting diodes; When input ac voltage changed or LED load 111 changes, PWM controller 107 feedback control loops were with closure, and output current is able to regulate the realization high precision constant current.For example when load current decline; Then the sampling and outputting voltage of current sampling resistor 115 has minor variations, but optocoupler 117 electric currents descend significantly, and the FB voltage of PWM controller 107 is risen; PWM controller 107 will increase duty ratio, and LED load 111 electric currents are increased; Same methods analyst can be known, if LED load 111 electric currents increase, the FB voltage of PWM controller 107 is descended, and PWM controller 107 will reduce duty ratio, and LED load 111 electric currents are reduced, thereby realizes high accuracy optocoupler constant current output.Setting LED load 111 electric currents calculating worker formula is: constant current ≈ 1.05V/ current sampling resistor 115 values.Resistance 114,116 can be regulated the DC current gain in the whole feedback, if LED load 111 is broken off, through the Zener voltage-stabiliser tube output voltage is limited in the set maximum voltage range, thereby guarantees safety.

The LED illumination driving circuit that the embodiment of the invention provides has the following advantages: directly utilize optocoupler to realize that the constant-current LED illumination drives, need not add various constant-current circuits, input realizes that with output electrical isolation guarantees safety, and circuit structure is simple, and cost is low; Input (85V-264V) and output voltage (12V-70V) wide ranges; Constant current accuracy is high, produces constant current accuracy in batches>5%; The V-I curve cut-in voltage of the forward input of the infrarede emitting diode of optocoupler has negative temperature coefficient feature, when ambient temperature increases, also can keep output current constant.

The above only is a preferred implementation of the present invention; Should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; Can also do some improvement and retouching, these improvement and retouching also should be regarded as protection scope of the present invention.

Claims

1. LED illumination driving circuit; It is characterized in that two output pins of optocoupler are connected with ground with the feedback pin fb of pulse width modulation (PWM) controller respectively, be parallel with first resistance between two input pins of optocoupler; And an input pin of optocoupler is connected with ground; Be in series with second resistance between another input pin of optocoupler and first tie point, between the ground and first tie point, be in series with the 3rd resistance, first tie point is a tie point of LED illumination driving circuit and load.

2. LED illumination driving circuit according to claim 1 is characterized in that, is parallel with the fb shunt capacitance between the feedback pin fb of PWM controller and the ground.

3. LED illumination driving circuit according to claim 2 is characterized in that, is parallel with the Zener voltage-stabiliser tube between first tie point and second tie point, and second tie point is another tie point of LED illumination driving circuit and load.

4. LED illumination driving circuit according to claim 1; It is characterized in that; Two outputs of input rectifying filter circuit are parallelly connected with VDD filter capacitor that is connected in series and starting resistance; VDD filter capacitor one end is connected with ground, and PWM controller VDD pin links to each other with the tie point of VDD filter capacitor and starting resistance.

5. LED illumination driving circuit according to claim 4 is characterized in that, primary inductance two ends connect an output of PWM controller drain pin and input rectifying filter circuit respectively, and this output is not connected with ground.

6. LED illumination driving circuit according to claim 4 is characterized in that, the primary inductance is parallelly connected with the clamped circuit of RCD.

7. LED illumination driving circuit according to claim 4 is characterized in that, transformer is assisted winding one end ground connection, and the other end links to each other through the tie point of VDD rectifier diode with VDD filter capacitor and starting resistance.

8. LED illumination driving circuit according to claim 4 is characterized in that, transformer secondary output winding one end connects second tie point, other end ground connection through the output rectifier diode.

9. LED illumination driving circuit according to claim 1 is characterized in that, the current monitoring end pin cs of PWM controller is through current sample input resistance ground connection.

10. an electronic equipment is characterized in that, comprises on the body like the described LED illumination driving circuit of the arbitrary claim of claim 1 to 9.