CN104968070B - A kind of LED drive circuit - Google Patents

Abstract

The invention discloses an LED drive circuit, comprising an overcurrent protection circuit (1), an EMI protection circuit (2), a rectification circuit (3), a constant current control circuit (4), and an LED lamp group (5). When the power supply voltage fluctuates, the current of the LED drive circuit can still fluctuate within a small range, and the constant current control circuit can automatically adjust when the system is disturbed, so that the output voltage and current are stable, and the constant current characteristic can be maintained. Under the premise, the electromagnetic interference is greatly reduced.

Description

A kind of LED driving circuit

technical field

The invention relates to the lighting field, in particular to an LED driving circuit.

Background technique

With the development of science and technology, LED, as a new type of light source, has the advantages of small size, low power consumption, high light efficiency, long life, environmental protection, etc., and is widely used in the field of lighting, and various LEDs have emerged The driving circuit, in practical applications, the driving current of the LED light source has a direct impact on the luminous efficiency and life.

At present, DC-DC chopping technology is used to drive LED in low-voltage places. It has the advantages of low power consumption, high efficiency, stability and reliability, etc., but its cost is high, the circuit is complex, easy to damage, and has strong high frequency. Defects such as interference have brought inconvenience to users. In the application, the LED drive circuit needs to maintain the constant current characteristics as much as possible, that is, when the power supply voltage fluctuates, the current of the LED drive circuit can still fluctuate within a small range. On the premise of maintaining the constant current characteristics, the protection function Also very important, such as overvoltage protection, anti-electromagnetic interference, etc.

Contents of the invention

The main purpose of the present invention is to solve the above problems and provide an LED drive circuit that can provide stable voltage, stable current and resist electromagnetic interference.

In order to achieve the purpose of the above invention, the present invention provides an LED drive circuit, which is characterized in that it includes an overcurrent protection circuit (1), an EMI protection circuit (2), a rectification circuit (3), a constant current control circuit (4), and an LED lamp Group (5), the input terminal of the overcurrent protection circuit (1) is connected to AC alternating current, the output terminal is connected to the EMI protection circuit (2), the output terminal of the EMI protection circuit (2) is connected to the rectification circuit (3), and the output terminal of the rectification circuit The constant current control circuit (4) is connected, and the constant current control circuit (4) is connected to the LED lamp group (5), wherein the constant current control circuit (4) provides stable input voltage and current for the LED lamp group.

Further, the overcurrent protection circuit includes a fuse, the EMI protection circuit includes a capacitor C1, a capacitor C2, an inductor L1, and an inductor L2, and the rectifier circuit adopts a bridge rectifier circuit.

Furthermore, terminals 1 and 2 of the bridge rectifier circuit (3) are input terminals of the rectification power supply, terminals 3 and 4 are output terminals of the rectification circuit, and the constant current control circuit (4) includes a power chip U1, a transformer T, MOS tube Q1, optocoupler OC, operational amplifier OPA1 and operational amplifier OPA2, the two ends of the bridge rectifier circuit (3) are connected to the HV pin of the power supply chip U1 through the diode D1, and the resistor R3 is connected to both ends of the diode D1 in parallel. The 3 terminals of the rectifier circuit are grounded after the inductor L4, the 4 terminals of the bridge rectifier circuit are connected to one end of the primary winding of the transformer T after the inductor L3, the other end of the primary winding of the transformer T is connected to the drain of the MOS transistor Q1, and the source of the MOS transistor Q1 The electrode is grounded after passing through the resistor R6, the Adj pin of the power chip U1 is grounded after passing through the resistor R4, the Gnd pin of the power chip U1 is grounded, the FB pin of the power chip U1 is connected to the input terminal of the photosensitive transistor in the optocoupler OC, and the output terminal of the photosensitive transistor is grounded The CS pin of the power chip U1 is connected to the source of the MOS transistor Q1, the NC pin of the power chip U1 is empty, the VCC pin of the power chip U1 is grounded after passing through the capacitor C6, and the Drv pin of the power chip U1 is connected to the gate of the MOS transistor Q1. Capacitor C5, resistor R5, and diode D2 constitute a clamping circuit connected across the two ends of the primary winding of the transformer T, one end of the secondary winding of the transformer T is connected to the anode of the LED lamp group 5 after passing through the diode D3, and the other end of the secondary winding of the transformer T One end is grounded, the negative pole of the LED lamp group 5 is connected to one end of the resistor R15, the other end of the resistor R15 is grounded, the capacitor C12 is connected in series with the resistor R7 and connected to both ends of the diode D3, and the capacitors C8 and C9 are respectively connected to the negative pole of the diode D3 and Between the ground, one end of the resistor R8 is connected to the negative pole of the diode D3, the other end is connected to the negative pole of the Zener diode ZD1 and one end of the resistor R10, the positive pole of the Zener diode ZD1 is respectively connected to the positive pole of the light-emitting diode of the optocoupler OC and the ground, and the capacitor C10 The resistor R11 is connected in parallel with the two ends of the Zener diode ZD1, the other end of the resistor R10 is respectively connected to the positive input end of the operational amplifier OPA1 and one end of the resistor R13, and the other end of the resistor R13 is connected to the positive input end of the operational amplifier OPA2 , the positive input terminal of the operational amplifier OPA2 is grounded after being passed through the resistor R14, the positive pole of the Zener diode ZD2 is grounded, the negative pole is connected to the positive input terminal of the operational amplifier OPA1, one end of the voltage dividing resistor R9 is connected to the positive pole of the LED lamp group 5, and the other end Connect one end of the voltage dividing resistor R12, the other end of the voltage dividing resistor R12 is grounded, the connection point of the voltage dividing resistor R9 and the voltage dividing resistor R12 is connected to the reverse input terminal of the operational amplifier OPA1, and the output terminal of the operational amplifier OPA1 is connected to the negative pole of the diode D4 , the anode of the diode D4 is connected to the cathode of the light-emitting diode in the optocoupler OC, the cathode of the LED lamp group 5 is connected to the reverse input terminal of the operational amplifier OPA2 through the resistor R16, and the reverse input terminal of the operational amplifier OPA2 is connected in series through the resistor R17, Capacitor C11 is connected to the cathode of diode D5, the anode of diode D5 is connected to the cathode of light-emitting diode in optocoupler OC, and the operational amplifier The output terminal of the amplifier OPA2 is connected to the cathode of the diode D5.

Further, the power chip U1 adopts the NCP1203 power control chip.

When the power supply voltage fluctuates, the present invention can still keep the current of the LED drive circuit fluctuating within a small range, and through the constant current control circuit, it can automatically adjust when the system is disturbed, so that the output voltage and current are stable Under the premise of the flow characteristics, the electromagnetic interference is greatly reduced.

Description of drawings

Fig. 1 is a functional schematic diagram of the LED driving circuit of the present invention.

Fig. 2 is a specific circuit connection diagram of the LED driving circuit of the present invention.

detailed description

The present invention will be further described and described in detail below in conjunction with the accompanying drawings and embodiments.

Embodiment: This embodiment provides an LED driving circuit, as shown in FIG. 1 , including an overcurrent protection circuit 1 , an EMI protection circuit 2 , a rectification circuit 3 , a constant current control circuit 4 , and an LED lamp group 5 .

As shown in Figure 2, the overcurrent protection circuit 1 includes a fuse, and the EMI protection circuit 2 includes a capacitor C1, a capacitor C2, an inductor L1, and an inductor L2. The capacitor C1 is connected in series with one end of the inductor L1 and the inductor L2, and the capacitor C2 is connected in series with the inductor. At the other end of L1 and inductor L2, the rectifier circuit 3 adopts a bridge rectifier circuit, in which terminals 1 and 2 of the bridge rectifier circuit are input terminals of the rectifier power supply, terminals 3 and 4 are output terminals of the rectifier circuit, and constant current control Circuit 4 includes power chip U1, transformer T, MOS tube Q1, optocoupler OC, operational amplifier OPA1 and operational amplifier OPA2. The two ends of the bridge rectifier circuit are connected to the HV pin of the power chip U1 through the diode D1, and the resistor R3 is connected to the diode At both ends of D1, the 3rd end of the bridge rectifier circuit is grounded after passing through the inductor L4, the 4th end of the bridge rectification circuit is connected to one end of the primary winding of the transformer T after passing through the inductor L3, and the other end of the primary winding of the transformer T is connected to the drain of the MOS tube Q1 The source of the MOS tube Q1 is grounded after the resistor R6, the Adj pin of the power chip U1 is grounded after the resistor R4, the Gnd pin of the power chip U1 is grounded, and the FB pin of the power chip U1 is connected to the input terminal of the photosensitive transistor in the optocoupler OC. , the output terminal of the phototransistor is grounded, the CS pin of the power chip U1 is connected to the source of the MOS tube Q1, the NC pin of the power chip U1 is left empty, the VCC pin of the power chip U1 is grounded after passing through the capacitor C6, and the Drv pin of the power chip U1 is connected to The gate of the MOS transistor Q1, the capacitor C5, the resistor R5, and the diode D2 form a clamping circuit connected across the two ends of the primary winding of the transformer T, and one end of the secondary winding of the transformer T is connected to the anode of the LED lamp group 5 after passing through the diode D3. The other end of the secondary winding of the transformer T is grounded, the negative pole of the LED lamp group 5 is connected to one end of the resistor R15, the other end of the resistor R15 is grounded, the capacitor C12 is connected in series with the resistor R7 and connected to both ends of the diode D3, and the capacitors C8 and C9 are respectively Connected between the negative pole of diode D3 and the ground, one end of resistor R8 is connected to the negative pole of diode D3, the other end is respectively connected to the negative pole of Zener diode ZD1 and one end of resistor R10, and the positive pole of Zener diode ZD1 is respectively connected to the light emitting diode of optocoupler OC The anode of the diode and the ground, the capacitor C10 and the resistor R11 are respectively connected in parallel to both ends of the Zener diode ZD1, the other end of the resistor R10 is respectively connected to the positive input end of the operational amplifier OPA1 and one end of the resistor R13, and the other end of the resistor R13 is connected to the operational The positive input terminal of the amplifier OPA2, the positive input terminal of the operational amplifier OPA2 is grounded after the resistor R14, the positive pole of the Zener diode ZD2 is grounded, the negative pole is connected to the positive input terminal of the operational amplifier OPA1, and one end of the voltage dividing resistor R9 is connected to the LED lamp The positive pole of group 5, the other end is connected to one end of the voltage dividing resistor R12, the other end of the voltage dividing resistor R12 is grounded, the connection point of the voltage dividing resistor R9 and the voltage dividing resistor R12 is connected to the reverse input terminal of the operational amplifier OPA1, and the connection point of the operational amplifier OPA1 The output terminal is connected to the cathode of the diode D4, the anode of the diode D4 is connected to the cathode of the light-emitting diode in the optocoupler OC, and the LED lamp group 5 The negative terminal of the operational amplifier OPA2 is connected to the reverse input terminal of the operational amplifier OPA2 through the resistor R16, and the negative terminal of the operational amplifier OPA2 is connected to the negative terminal of the diode D5 through the serially connected resistor R17 and capacitor C11, and the positive terminal of the diode D5 is connected to the light-emitting diode in the optocoupler OC The negative pole of the operational amplifier OPA2 is connected to the negative pole of the diode D5.

Wherein the power chip U1 in this embodiment adopts the NCP1203 power control chip.

When the output voltage exceeds the preset voltage, the operational amplifier OPA1 outputs a pull-down signal, and the current flows to the light-emitting diode in the OC, thereby pulling down the current of the phototransistor in the OC. When the current exceeds the threshold current value of the feedback pin of the power chip U1, the power supply The chip U1 outputs a control signal to turn off the MOS transistor Q1. When the output voltage is lower than the preset voltage, the power chip U1 outputs a control signal to turn on the MOS transistor Q1; when the current flowing through the LED lamp group is greater than the preset current value, The operational amplifier OPA2 outputs a pull-down signal, and the current flows to the light-emitting diode in the OC, thereby pulling down the current of the phototransistor in the OC. When the current exceeds the threshold current value of the feedback pin of the power chip U1, the power chip U1 outputs a control signal to turn off the MOS transistor Q1. When the output voltage is lower than the preset voltage, the power supply chip U1 outputs a control signal to turn on the MOS transistor Q1. Through the above adjustment, the output voltage and current can be kept basically constant.

When the power supply voltage fluctuates, the present invention can still keep the current of the LED drive circuit fluctuating within a small range, and through the constant current control circuit, it can automatically adjust when the system is disturbed, so that the output voltage and current are stable Under the premise of the flow characteristics, the electromagnetic interference is greatly reduced.

What is described in this specification is only a preferred specific embodiment of the invention, and the above embodiments are only used to illustrate the technical solution of the present invention, not to limit the invention. All technical solutions that can be obtained by those skilled in the art through logical analysis, reasoning or limited experiments according to the concept of the present invention shall be within the scope of the present invention.

Claims (2)

1. a kind of LED drive circuit, including current foldback circuit（1）, EMI protection circuit（2）, bridge rectifier（3）, constant current Control circuit（4）, LED light group（5）, current foldback circuit（1）Input termination AC alternating currents, output termination EMI protection circuit （2）, EMI protection circuit（2）Output termination bridge rectifier, bridge rectifier output termination constant-current control circuit （4）, constant-current control circuit（4）Connect LED light group（5）, wherein constant-current control circuit（4）Stable input electricity is provided for LED light group Pressure and electric current, current foldback circuit include fuse, and EMI protection circuit includes electric capacity C1, electric capacity C2, inductance L1, inductance L2, its It is characterised by, bridge rectifier（3）1 end, 2 ends be rectifier power source input, 3 ends, 4 ends be rectification circuit output End, constant-current control circuit（4）Including power supply chip U1, transformer T, metal-oxide-semiconductor Q1, optocoupler OC, operational amplifier OPA1 and computing Amplifier OPA2, bridge rectifier（3）2 ends power supply chip U1 HV pin are connect through diode D1, resistance R3 is attempted by two poles Pipe D1 two ends, 3 ends of bridge rectifier are grounded after inductance L4, and 4 ends of bridge rectifier are followed by transformation through inductance L3 One end of device T armature windings, another termination metal-oxide-semiconductor Q1 of transformer T armature windings drain electrode, metal-oxide-semiconductor Q1 source electrode is through resistance It is grounded after R6, power supply chip U1 Adj pin are grounded after resistance R4, power supply chip U1 Gnd pin ground connection, power supply chip U1 FB Pin connects the phototriode input in optocoupler OC, and the output head grounding of phototriode, power supply chip U1 CS pin connect metal-oxide-semiconductor Q1 source electrode, power supply chip U1 NC pin are empty, and are grounded after power supply chip U1 VCC foot meridian capacitors C6, power supply chip U1 Drv Pin connects metal-oxide-semiconductor Q1 grid, and electric capacity C5, resistance R5, diode D2 constitute clamp circuit and be connected across the two of transformer T armature windings End, one end of transformer T secondary windings is connected to the positive pole of LED light group 5 after diode D3, transformer T secondary windings it is another One end is grounded, the negative pole connecting resistance R15 of LED light group 5 one end, and resistance R15 other end ground connection, electric capacity C12 and resistance R7 goes here and there Diode D3 two ends are connected to after connection, electric capacity C8, C9 are connected between diode D3 negative pole and ground, the one of resistance R8 Terminating diode D3 negative pole, the other end connects voltage-regulator diode ZD1 negative pole and resistance R10 one end, voltage-regulator diode respectively ZD1 positive pole connects optocoupler OC light emitting diode positive pole and ground respectively, and electric capacity C10 and resistance R11 are connected in parallel in surely respectively Diode ZD1 two ends are pressed, the resistance R10 other end connects operational amplifier OPA1 positive input and resistance R13 respectively One end, resistance R13 another termination operational amplifier OPA2 positive input, operational amplifier OPA2 positive input It is grounded after resistance R14, voltage-regulator diode ZD2 plus earth, negative pole connects operational amplifier OPA1 positive input, partial pressure The positive pole of a resistance R9 termination LED light group 5, another termination divider resistance R12 one end, divider resistance R12 another termination Ground, divider resistance R9 and divider resistance R12 tie point connect operational amplifier OPA1 reverse input end, operational amplifier OPA1 Output terminating diode D4 negative pole, diode D4 positive pole connects the negative pole of light emitting diode in optocoupler OC, LED light group 5 Negative pole is followed by operational amplifier OPA2 reverse input end through resistance R16, and operational amplifier OPA2 reverse input end is through concatenation Resistance R17, electric capacity C11 be followed by diode D5 negative pole, diode D5 positive pole connects the negative pole of light emitting diode in optocoupler OC, Operational amplifier OPA2 output terminating diode D5 negative pole.

2. a kind of LED drive circuit as claimed in claim 1, it is characterised in that power supply chip U1 uses NCP1203 power supply controls Coremaking piece.