TW201419934A - LED driving circuit - Google Patents

Abstract

The present invention is a LED driving circuit, which includes: a protection unit connected to an AC power source; a rectifying filtering unit electrically connected to the protection unit; a control unit with one end electrically connected to the rectifying filtering unit; a LED driving unit provided with a LED, a first capacitor and a transistor. The LED is connected in parallel with the first capacitor. The LED has a positive electrode and a negative electrode. The positive electrode of the LED is electrically connected to the rectifying filtering unit and the control unit, and a detection current feedback unit is disposed between the LED driving unit and the control unit. Thereby, the detecting current feedback unit forms a protective circuit so as to prevent power increase from high AC power voltage input.

Description

LED drive circuit

The invention relates to an LED driving circuit, in particular to an LED driving circuit which uses a transistor to operate in a linear region, has no switching frequency, and does not need to use electromagnetic interference, and the detecting current feedback unit forms a high voltage. The compensation circuit for feedback compensation can avoid the situation that the voltage input of the AC power source is too high and the power is increased.

First, as shown in Fig. 1, the conventional LED driving circuit is a DC power supply that provides a constant current and power in a manner of a flyback circuit 72 and a pulse width modulation (PWM) 71. The missing is that there is a pulse. The cost of the wave width modulator and the required parts of the EMI filter.

Furthermore, the LED driver circuit is not used, and there is no protection circuit using high-voltage feedback compensation. If it uses a linear power supply, although there is no electromagnetic interference, the higher the voltage of the input AC power supply, the electricity on the opposite circuit. The higher the cross-voltage of the crystal, the higher the AC power supply voltage input, resulting in a rapid rise in power (W) (as shown in Figure 2), so the LED cannot be protected and the LED is easily overheated.

In view of this, the present inventors have devoted themselves to research and design, and have been able to provide an LED driving circuit that uses a transistor to operate in a linear region without switching frequency without using an electromagnetic interference filter LED driving circuit, and The protection circuit with high-voltage feedback compensation can avoid the situation that the voltage input of the AC power source is too high and the power is increased, which is the creative motive for the invention to be developed.

The main object of the present invention is to provide an LED driving circuit which uses a transistor to operate in a linear region without switching frequency without using a filter for electromagnetic interference, which makes the circuit structure simple and low in cost.

Another object of the present invention is to provide an LED driving circuit which has a detecting current feedback unit to form a protection circuit, which can avoid the situation that the voltage input of the AC power source is too high and the power is increased.

In order to achieve the above object, the present invention is an LED driving circuit, comprising: a protection unit connected to an AC power supply; a rectifying and filtering unit electrically connected to the protection unit; and a control unit electrically connected to the rectification at one end a filter unit; an LED driving unit is provided with a light emitting diode, a first capacitor and a transistor, the light emitting diode system is connected in parallel with the first capacitor, and the light emitting diode has a positive electrode and a negative An electrode, the positive electrode of the light emitting diode is electrically connected to the rectifying and filtering unit and the control unit; and a detecting current feedback unit is disposed between the LED driving unit and the control unit, and the detecting current is back The unit is provided with a first resistor, a second resistor, a third resistor and a fourth resistor. One end of the first resistor is electrically connected to one end of the second resistor and the control unit, and the first resistor is One end is electrically connected to the negative electrode of the light emitting diode, and the other end of the second resistor is electrically connected to the transistor, one end of the third resistor and one end of the fourth resistor, wherein the third resistor and the fourth resistor Joint, and the other end of the third resistor and the fourth resistor and ground. Thereby, the transistor is operated in the linear region, and there is no switching frequency, and the filter without using electromagnetic interference is used, so that the circuit structure is simple and the cost is low, and the detection current is fed back to the unit to form a protection circuit. Avoid situations where the voltage input to the AC power supply is too high and the power is increased.

For a fuller understanding of the features, features and aspects of the present invention, reference should be made to the accompanying drawings.

Please refer to the third to fifth embodiments, the present invention is an LED driving circuit, comprising: a protection unit 10, is connected to an AC power supply 60; a rectification and filtering unit 20, is electrically connected to the protection unit 10; A control unit 30 is electrically connected to the rectifying and filtering unit 20 at one end. An LED driving unit 40 is provided with a light emitting diode 41, a first capacitor 43 and a transistor 42. The LED diode 41 is coupled to The first capacitors 43 are connected in parallel, and the light-emitting diodes 41 have a positive electrode 411 and a negative electrode 412. The positive electrode 411 of the light-emitting diode 41 is electrically connected to the rectifying and filtering unit 20 and the control unit 30; A detection current feedback unit 50 is disposed between the LED driving unit 40 and the control unit 30. The detection current feedback unit 50 is provided with a first resistor 51, a second resistor 52, and a a third resistor 53 and a fourth resistor 54 are electrically connected to one end of the second resistor 52 and the control unit 30, and the other end of the first resistor 51 is electrically connected to the negative of the LED. An electrode 412, the other end of the second resistor 52 is electrically connected to the transistor 42, One end of the third resistor and the fourth resistor 53 at one end 54, 53 in parallel with the fourth resistor 54, and the third resistor 53 and the other end of the third resistor and the fourth resistor 54 and ground. The first resistor 51, the second resistor 52, the third resistor 53, and the fourth resistor 54 provide an effect of detecting current feedback and achieving high and low voltage compensation protection, and The control unit 30 drives the light emitting diodes in a linear constant current manner.

The control unit 30 includes a voltage regulator 301, a voltage reference unit 302, an operational amplifier 304, and a temperature protection unit. The control unit 30 has a high voltage terminal (HV) 311 and a low voltage. a terminal (VDD) 312, a detecting terminal (CS) 315, a grounding terminal (GND) 313, and a gate terminal (GATE) 314; the voltage regulator 301 is connected to the high voltage terminal (HV) 311 at one end, and the voltage is adjusted. The other end of the 301 is connected to the low voltage terminal (VDD) 312. The operational amplifier 304 has a positive phase input terminal 305, an inverting input terminal 306 and an output terminal 307. The positive phase input terminal 305 is connected to the voltage reference unit 303. The inverting input terminal 306 is connected to the detecting terminal (CS) 315, and the output terminal 307 is connected to the temperature protection unit 302 and the gate terminal (GATE) 314. The gate terminal (GATE) 314 of the control unit 30 is electrically connected to the transistor 42 of the LED driving unit 40. The high voltage terminal (HV) 311 is electrically connected to the rectifying and filtering unit 20 via a fifth resistor 33. A second capacitor 32 is connected between the low voltage terminal (VDD) 312 and the ground terminal 313. The detecting terminal (CS) 315 is electrically connected to one end of the first resistor 51 and the second resistor 52. The fifth resistor 33 is used to control the high voltage start current limit, and the second capacitor 32 is used to provide filtering noise.

Furthermore, the transistor 42 of the LED driving unit has a 汲 terminal 421, a gate terminal 422 and a source terminal 423. The gate terminal 422 of the transistor 42 is connected to the gate terminal (GATE) 314 of the control unit 30. The terminal 421 is connected to the other end of the second resistor 52 and one end of the third resistor 53 and the fourth resistor 54. Wherein the transistor 42 is a metal oxide semiconductor field effect transistor (MOSFET), by the control unit 30 and the detection current feedback unit 315, the transistor 42 is operated in a linear region, and the heating source of the transistor 42 and the light emitting diode The light panels of the body 41 (not shown) are combined to provide heat dissipation. Further, the light-emitting diode 41 is connected in parallel with the first capacitor 43. The first capacitor 43 can reduce the voltage and current ripple of the light-emitting diode 41 and have a voltage-stabilizing effect.

The protection unit 10 includes a fuse 11, a thermistor (NTC) 12 and a varistor (TVR) 13, and the AC power source 60 has a live end (L) 61 and a ground end (N). 62, one end of the fuse 11 is connected to the live end 61 of the AC power source 60, and the other end of the fuse 11 is connected to the thermistor (NTC) 12 and one end of the varistor (TVR) 13, and the varistor (TVR) The other end of the 13 is connected to the ground terminal (N) 62 of the AC power source 60 and the rectifying and filtering unit 20. Thereby, the fuse 11 is used to provide short circuit protection, the thermistor (NTC) 12 provides protection against surge current, and the varistor (TVR) 13 provides protection surge voltage.

The rectifying and filtering unit 20 includes a bridge rectifier 21 and a filter capacitor 22. The bridge rectifier 21 has a first pin 211, a second pin 212, a third pin 213, and a fourth. The first pin 211 is connected to the other end of the thermistor (NTC) 12 of the protection unit 10 by a sixth resistor 14. The second pin 212 is grounded, and the third pin 213 is connected to the AC. The ground terminal (N) 62 of the power supply and the other end of the varistor (TVR) 13 are electrically connected to the filter capacitor 22, the control unit 30, and the LED driving unit 40. Thereby, the bridge rectifier 21 is rectified corresponding to the AC power source 60, and the filter capacitor 22 is used to filter out high frequency noise.

Finally, please refer to FIG. 6 , which is a schematic diagram of the input voltage corresponding to the output power (W) of the LED driving circuit of the present invention. Please also refer to the figures 3 to 5, when the input AC power voltage is lower. The lower the voltage across the transistor 42 on the circuit of the output LED diode 41, the first resistor 51 and the second resistor 52 are used to detect the voltage across the transistor 42, and the relative feedback voltage ΔV is also lower. The lower the voltage detected by the third resistor 53 in parallel with the fourth resistor 54, the lower the output current of the LED diode 41, thereby forming a protection circuit.

When the input voltage of the AC power source is higher, the voltage across the transistor 42 on the circuit of the output LED diode 41 is higher, and the first resistor 51 and the second resistor 52 are used to detect the voltage across the transistor 42. The higher the relative feedback voltage ΔV, the third resistor 53 is connected in parallel with the voltage division on the fourth resistor 54 to lower the output current of the LED diode 41, thereby forming a protection circuit to prevent the AC power supply voltage from being input too high. And the power (W) rises.

Features of the invention:

1. The LED driving circuit of the present invention uses a linear power supply, and is not a pulse width modulation (PWM) method, and has no electromagnetic interference (EMI) problem.

2. The LED driving circuit of the invention has no electromagnetic interference (EMI), which can reduce the cost of safety parts.

3. The linear power factor of the LED driving circuit of the invention, PF=0.7~0.9, because no large capacitor is placed after the bridge rectification, but is connected in parallel to the positive and negative electrodes of the LED to stabilize and protect. Light-emitting diode.

4. When the input AC power voltage is lower, the voltage across the output LED circuit is lower, and the first resistor and the second resistor are used to detect the voltage across the transistor, and the voltage is relatively feedback. The lower the ΔV, the more the voltage detected by the third resistor in parallel with the fourth resistor Low will lower the output current of the LED to form a protection circuit.

5. When the input voltage of the AC power source is higher, the voltage across the output LED circuit is higher. The first resistor and the second resistor are used to detect the voltage across the transistor. The higher the voltage ΔV, plus the third resistor and the voltage division above the fourth resistor will lower the output current of the LED, thereby forming a protection circuit, which can avoid the AC power supply voltage input is too high and cause power (W) rise.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The equivalent structural changes of the present invention and the contents of the drawings are all included in the scope of the present invention. , combined with Chen Ming.

10‧‧‧Protection unit

11‧‧‧Fuse

12‧‧‧Thermistor (NTR)

13‧‧‧ varistor (TVR)

14‧‧‧6th resistor

20‧‧‧Rectifier Filter Unit

21‧‧‧Bridge rectifier

211‧‧‧First pin

212‧‧‧second pin

213‧‧‧ third pin

214‧‧‧fourth pin

22‧‧‧Filter capacitor

30‧‧‧Control unit

301‧‧‧Voltage regulator

302‧‧‧Temperature protection unit

303‧‧‧Voltage reference unit

304‧‧‧Operational Amplifier

305‧‧‧Positive input

306‧‧‧Inverting input

307‧‧‧output

311‧‧‧High voltage terminal (HV)

312‧‧‧Low voltage terminal (VDD)

313‧‧‧ Ground (GND)

314‧‧‧Gate Extreme (GATE)

315‧‧‧Detection (CS)

32‧‧‧second capacitor

33‧‧‧ fifth resistor

40‧‧‧LED drive unit

41‧‧‧Lighting diode

411‧‧‧ positive electrode

412‧‧‧negative electrode

42‧‧‧Optoelectronics

421‧‧‧汲 Extreme

422‧‧ ‧ gate extreme

423‧‧‧ source extreme

43‧‧‧first capacitor

50‧‧‧Detection current feedback unit

51‧‧‧First resistance

52‧‧‧second resistance

53‧‧‧ Third resistor

54‧‧‧fourth resistor

60‧‧‧AC power supply

61‧‧‧Firewire end (L)

62‧‧‧ Ground end (N)

71‧‧‧ Pulse width modulation (PWM)

72‧‧‧Return-type circuit

Figure 1 is a circuit diagram of a conventional LED driver circuit.

Figure 2 is a schematic diagram of the input voltage corresponding to the output power (W) of the conventional LED driver circuit.

Figure 3 is a block diagram of the LED driving circuit of the present invention.

Figure 4 is a schematic diagram of the LED driving circuit of the present invention.

Figure 5 is a block diagram of the internal unit of the control unit of the present invention.

Figure 6 is a schematic diagram of the input power corresponding to the output power (W) of the LED driving circuit of the present invention.

10‧‧‧Protection unit

20‧‧‧Rectifier Filter Unit

30‧‧‧Control unit

40‧‧‧LED drive unit

50‧‧‧Detection current feedback unit

60‧‧‧AC power supply

Claims (6)

An LED driving circuit includes: a protection unit connected to an AC power source; a rectifying and filtering unit electrically connected to the protection unit; and a control unit electrically connected to the rectifying and filtering unit at one end; an LED driving unit The invention is provided with a light-emitting diode, a first capacitor and a transistor. The light-emitting diode system is connected in parallel with the first capacitor, and the light-emitting diode has a positive electrode and a negative electrode, and the light-emitting diode has The positive electrode is electrically connected to the rectifying and filtering unit and the control unit; and a detecting current feedback unit is disposed between the LED driving unit and the control unit, and the detecting current feedback unit is provided with: a resistor, a second resistor, a third resistor, and a fourth resistor, wherein the first resistor is electrically connected to one end of the second resistor and the control unit, and the other end of the first resistor is electrically connected to the LED a negative electrode of the body, the other end of the second resistor is electrically connected to the transistor, one end of the third resistor and one end of the fourth resistor, wherein the third resistor is connected in parallel with the fourth resistor, and the third resistor is another End of the fourth resistor and ground. The LED driving circuit of claim 1, wherein the control unit comprises: a voltage regulator, a voltage reference unit, an operational amplifier and a temperature protection unit, and the control unit has a high voltage externally. a low voltage terminal, a detecting terminal, a grounding terminal and a gate terminal; the voltage regulator is connected to the high voltage terminal at one end, and the other end of the voltage regulator is connected to the low voltage terminal, the operational amplifier has a positive phase An input terminal, an inverting input terminal and an output terminal, wherein the non-inverting input terminal is connected to the voltage reference unit, and the inverting input is The input terminal is connected to the detecting end, and the output terminal is connected to the temperature protection unit and the gate terminal. The LED driving circuit of claim 2, wherein the gate of the control unit is electrically connected to the transistor of the LED driving unit, and the high voltage terminal is electrically connected to the rectifying and filtering unit via a fifth resistor. A second capacitor is connected between the low voltage end of the control unit and the ground end, and the detecting end is electrically connected to the first resistor and one end of the second resistor. The LED driving circuit of claim 3, wherein the transistor of the LED driving unit has a 汲 terminal, a gate terminal and a source terminal, and the gate terminal of the transistor is connected to the gate terminal of the control unit. The 汲 terminal is connected to the negative electrode of the illuminating diode, and the source terminal is connected to the other end of the second resistor and one end of the third resistor and the fourth resistor. The LED driving circuit of claim 1, wherein the protection unit comprises: a fuse, a thermistor and a varistor, wherein the AC power source has a live terminal and a ground terminal, the fuse One end is connected to the live end of the AC power source, and the other end of the fuse is connected to the thermistor and one end of the varistor, and the other end of the varistor is connected to the ground of the AC power source and the rectifying and filtering unit. The LED driving circuit of claim 5, wherein the rectifying and filtering unit comprises: a bridge rectifier and a filter capacitor, and the bridge rectifier has a first pin, a second pin, and a first a third pin and a fourth pin; the first pin is connected to the other end of the thermistor of the protection unit by a sixth resistor, the second pin is grounded, and the third pin is connected to the ground of the AC power source The line end and the other end of the varistor are electrically connected to the filter capacitor, the control unit and the LED driving unit.