CN201479428U - A constant current and constant voltage LED lighting circuit - Google Patents

Abstract

The utility model discloses a constant current constant voltage LED lighting circuit, comprising a rectification filter circuit (1), a voltage stabilization circuit (2), an LED load (3), a constant current control circuit (4), a constant current control circuit (4 ) is connected with the voltage stabilizing circuit (2) and the LED load (3), and the constant current control circuit (4) includes a constant current control IC (U2), a current sampling resistor (R11), a power MOSFET (Q2), and a constant current control IC (U2) includes a positive power supply terminal (VDD), a ground terminal (VSS), an output terminal (G), and a current feedback terminal (CS). The two ends of (R11) are respectively connected to the ground terminal (VSS) and the current feedback terminal (CS), the gate of the power MOSFET (Q2) is connected to the output terminal (G), and the source of the power MOSFET (Q2) and the drain are respectively connected to the current feedback terminal (CS) and the LED load (3). The utility model can be applied to the field of LED lighting.

Description

A constant current and constant voltage LED lighting circuit

technical field

The utility model relates to a constant current and constant voltage LED lighting circuit.

Background technique

At present, the application of LEDs is becoming more and more extensive, and LED lamps for daily indoor and outdoor lighting are also becoming more and more popular. In the circuit of LED lamps, although the power consumption of the LED is not large, it is required that the necessary current and voltage of the provided power supply remain relatively stable within a certain range, and at the same time, it is required to have a certain over-current and over-voltage protection for the LED. LED lighting circuits generally need to output 220V AC power up to 300-400V DC after rectification and filtering. Due to the discreteness of the forward voltage drop of LEDs, it is necessary to directly drive LED strings at voltages up to 300-400V. Current drive, in order to eliminate the inconsistency of the total voltage drop of each group of LEDs, to solve the power supply of this type of load is usually a constant current or regulated power supply, and it is also necessary to add some components in the load in the power circuit under abnormal conditions Under the overcurrent protection circuit, this makes this type of power supply have the disadvantages of many components, complex circuits, and a large proportion of power consumption. Current LED drive circuits are generally provided with constant current or constant voltage circuits separately, and circuits with both constant current and constant voltage functions are rare. Figure 1 is an existing isolated switching power supply voltage stabilization circuit. The so-called "isolated" means that the ground terminals on both sides of the transformer are independent. Although the voltage at the output terminal of the power supply of this circuit can be kept stable, the LED After working at high temperature for a long time, its conduction voltage will drop, so if the voltage across the LED remains constant, its operating current will increase. Therefore, in the actual application of the voltage stabilizing circuit, after a period of use, the phenomenon that the LED is burned due to the increase of the current often occurs, shortening the service life. Figure 2 is an existing non-isolated power supply LED constant current circuit. Although this circuit can ensure the current stability of the output terminal, but in the case of multiple loads connected in parallel, it will cause uneven current in each branch. distribution, so that after one LED is burned out, it is easy to accelerate the burning of all branch LEDs.

Utility model content

The technical problem to be solved by the utility model is to overcome the deficiencies of the prior art and provide an LED lighting circuit with both functions of constant current and constant voltage. The constant current and constant voltage LED lighting circuit has simple structure, high efficiency and low power consumption. Low cost, energy saving, can prolong the service life of LED load.

The technical scheme adopted in the utility model is: the utility model includes a rectification filter circuit, a voltage stabilization circuit, and an LED load, and the alternating current is rectified and filtered by the rectification filter circuit and then converted into direct current, and then stabilized by the voltage stabilization circuit to become The constant-voltage direct current flows through the LED load, and the constant-current constant-voltage LED lighting circuit also includes a constant-current control circuit, which is connected to the voltage-stabilizing circuit and the LED load. The constant current control circuit includes a constant current control IC, a current sampling resistor, and a power MOSFET. The constant current control IC includes a power supply positive terminal, a ground terminal, an output terminal, and a current feedback terminal. To obtain a voltage, the two ends of the current sampling resistor are respectively connected to the ground terminal and the current feedback terminal, the gate of the power MOSFET is connected to the output terminal, and the source of the power MOSFET and the drain are respectively connected to the current feedback end and the LED load.

The constant current control IC includes a reference voltage generation circuit and at least one output comparator, the reference voltage generation circuit includes a reference comparator, a first triode, a second triode, a first resistor, a second resistor, a second Three resistors, the bases of the first transistor and the second transistor are connected to the output terminal of the reference comparator and the non-inverting input terminal of the output comparator to form a reference voltage sampling point, The collectors of the first triode and the second triode are connected to the positive terminal of the power supply, and the emitter of the first triode is connected to the ground terminal through the third resistor. connected, the emitter of the second triode is connected in series with the ground terminal through the first resistor and the second resistor, and the non-inverting input terminal of the reference comparator is connected to the first resistor , the voltage dividing point of the second resistor is connected, the inverting input terminal of the reference comparator is connected with the emitter of the first triode, the output terminal and the inverting input terminal of the output comparator respectively connected to the output terminal and the current feedback terminal of the constant current control IC.

The LED load includes at least one group of several LEDs connected in series.

Each group of LEDs is connected in series with one of the constant current control circuits, and several groups after series connection are connected in parallel with the voltage stabilizing circuit.

Alternatively, each group of LEDs is connected in parallel and then connected in series with one of the constant current control circuits as a whole, and connected to the voltage stabilizing circuit.

Further, the constant current control IC includes several output comparators, the several output comparators are connected in parallel and the non-inverting input ends are all connected to the reference voltage sampling point.

The LED load includes several groups of LEDs connected in series, and the constant current control IC includes several groups of output terminals and current feedback terminals connected in parallel, and each group of output terminals and current feedback terminals is connected to a group of LEDs. in series.

The voltage stabilizing circuit is a switching power supply, and the voltage stabilizing circuit includes a power factor correction circuit.

The constant current and constant voltage LED lighting circuit also includes an EMI circuit, the EMI circuit is connected between the input terminal of the AC power supply and the rectification and filtering circuit, and the rectification and filtering circuit adopts bridge rectification.

The constant current and constant voltage LED lighting circuit also includes a short circuit protection circuit connected between the input terminal of the AC power supply and the EMI circuit.

The beneficial effects of the utility model are: since the utility model includes a rectification and filtering circuit, a voltage stabilizing circuit, an LED load, and a constant current control circuit, the alternating current is rectified and filtered by the rectifying and filtering circuit to become direct current and then passed through the stabilizing circuit The constant voltage becomes constant voltage direct current and flows through the LED load. The constant current control circuit is connected with the voltage stabilization circuit and the LED load. The constant current control circuit includes a constant current control IC, a current sampling Resistor, power MOSFET, the constant current control IC includes a power supply positive terminal, a ground terminal, an output terminal, and a current feedback terminal, the power supply positive terminal obtains voltage from the voltage stabilizing circuit, and the two ends of the current sampling resistor are respectively It is connected to the ground terminal and the current feedback terminal, the gate of the power MOSFET is connected to the output terminal, and the source and drain of the power MOSFET are respectively connected to the current feedback terminal and the current feedback terminal. The LED load is connected, and a stable voltage output is obtained through the rectification filter circuit and the voltage stabilizing circuit. Even if the LED load works at a high temperature for a long time, when the current of the LED load changes, the constant The current control IC can prevent current changes, prolong the service life of the LED load, and avoid burning out. The constant current control IC is an independent device, which is convenient to replace the peripheral constant voltage and current stabilization circuits of other existing circuits, so that the circuit components are greatly reduced. , The circuit is simple, so the utility model has two functions of constant current and constant voltage. The current overvoltage protection function, applying it to the LED lighting circuit can save the power consumption of the entire circuit.

Description of drawings

Fig. 1 is a schematic diagram of an existing isolated switching power supply voltage stabilizing circuit;

Fig. 2 is a schematic diagram of an existing non-isolated power supply LED constant current circuit;

Fig. 3 is a schematic circuit diagram of Embodiment 1 of the utility model;

Fig. 4 is a schematic diagram of the internal circuit of the constant current control IC of Embodiment 1 of the present utility model;

Fig. 5 is a schematic circuit diagram of a second embodiment of the utility model;

Fig. 6 is a schematic circuit diagram of a third embodiment of the utility model;

7 is a schematic circuit diagram of Embodiment 4 of the utility model;

FIG. 8 is a schematic diagram of the internal circuit of the constant current control IC according to Embodiment 4 of the present invention.

Detailed ways

Embodiment one:

As shown in Figure 3 and Figure 4, this embodiment is a non-isolated constant current and constant voltage LED lighting circuit, including a rectification filter circuit 1, a voltage stabilization circuit 2, an LED load 3, a constant current control circuit 4, and an EMI circuit 5 , short-circuit protection circuit 6, the alternating current is rectified and filtered by the rectifying and filtering circuit 1 to become direct current, and then the voltage is stabilized by the voltage stabilizing circuit 2 to become a constant voltage direct current, and then flows through the LED load 3; the rectifying and filtering Circuit 1 adopts bridge rectification, including rectifier bridge D1, filter capacitor C5; said EMI circuit 5 includes transformer T1 and four capacitors C1, C2, C3, C4, connected to the input end of the AC power supply and said rectifier filter circuit 1 between; the short-circuit protection circuit 6 includes a fuse F1 for overcurrent and short-circuit protection, and is connected between the input terminal of the AC power supply and the EMI circuit 5; the voltage stabilizing circuit 2 is a switching power supply, and the stabilizing circuit 2 The voltage circuit 2 includes a power factor correction circuit U1. The power factor correction circuit U1 adopts a power supply PFC power factor control circuit of the model L6561 produced by ST Company. It has the advantages of simple circuit and high efficiency, and is currently widely used in energy-saving lamps. In a power supply circuit that requires power factor correction, its peripheral components include five capacitors C6~C10, ten resistors R1~R10, two diodes D2, D3, a MOS transistor Q1, a voltage regulator transistor Z1, and a transformer T2; The constant current control circuit 4 is connected with the voltage stabilizing circuit 2 and the LED load 3, the constant current control circuit 4 includes a constant current control ICU2, a current sampling resistor R11, a power MOSFET Q2, the constant current The control IC U2 includes a positive power supply terminal VDD, a ground terminal VSS, an output terminal G, and a current feedback terminal CS. The positive power supply terminal VDD obtains voltage from the voltage stabilizing circuit 2, and the two ends of the current sampling resistor R11 are respectively connected to the The ground terminal VSS and the current feedback terminal CS are connected, the gate of the power MOSFET Q2 is connected to the output terminal G, and the source and drain of the power MOSFET Q2 are respectively connected to the current feedback terminal. The terminal CS is connected to the LED load 3; the constant current control IC U2 includes a reference voltage generation circuit and an output comparator OP1, and the reference voltage generation circuit includes a reference comparator OP0, a first triode Q10, a second Two transistors Q20, a first resistor R21, a second resistor R22, and a third resistor R23, the bases of the first transistor Q10 and the second transistor Q20 are connected to the reference comparator OP0 The output terminal and the non-inverting input terminal of the output comparator OP1 are connected to form a reference voltage sampling point Vref, and the collectors of the first transistor Q10 and the second transistor Q20 are connected to the positive terminal of the power supply. VDD is connected, the emitter of the first transistor Q10 is connected to the ground terminal VSS through the third resistor R23, and the emitter of the second transistor Q20 is connected to the ground terminal VSS through the first resistor R21, The second resistor R22 is connected in series and connected to the ground terminal VSS The non-inverting input terminal of the reference comparator OP0 is connected to the voltage dividing point of the first resistor R21 and the second resistor R22, and the inverting input terminal of the reference comparator OP0 is connected to the first three The emitter of the pole tube Q10 is connected, the output terminal and the inverting input terminal of the output comparator OP1 are connected to the output terminal G of the constant current control IC U2 and the current feedback terminal CS respectively, and the The positive terminal VDD of the power supply obtains an operating voltage suitable for the constant current control IC U2 from the voltage stabilizing circuit 2, and the output terminal of the output comparator OP1 directly drives the gate of the power MOSFET Q2 to flow the current The current of the sampling resistor R11 generates a voltage that is fed back to the inverting input terminal of the output comparator OP1 to control the output of the output comparator OP1, so that the current through the power MOSFET Q2 is stabilized at the following value: Vref/ R11, this value is the constant current value designed; the LED load 3 includes a group of N LEDs connected in series, each of the LEDs is connected in series with one of the constant current control circuits 4, and then connected to the voltage regulator circuit 4 in series. The circuits 2 are connected to form a loop.

The utility model obtains a stable voltage output through the rectification filter circuit 1 and the voltage stabilizing circuit 2. Even if the LED load 3 works at high temperature for a long time, when the current of the LED load 3 changes, the The constant current control IC U2 can prevent current changes, prolong the service life of the LED load, and avoid burning out. As an independent device, the constant current control IC U2 is convenient to replace the peripheral constant voltage and current stabilization circuits of other existing circuits, making the circuit The components are greatly reduced, the circuit is simple, and the service life of the LED load can be extended. Therefore, the utility model can provide the load with stable voltage and current output at the same time, and is especially suitable for the LED load with high service life requirements. The constant current and constant voltage LED lighting The circuit has high efficiency, low power consumption, energy saving and over-current and over-voltage protection function, and it can save the power consumption of the whole circuit by applying it to the LED lighting circuit.

Embodiment two:

As shown in Figure 5, the difference between this embodiment and Embodiment 1 is that the LED load 3 of this embodiment includes M groups of LEDs, and each group has N LEDs connected in series, and the M groups are connected in parallel. After the LEDs are connected in parallel, they are connected in series with the constant current control circuit 4 as a whole, and connected with the voltage stabilizing circuit 2 to form a loop. This embodiment can only control the overall current of each group of LEDs connected in parallel.

The remaining features of this embodiment are the same as those of Embodiment 1.

Embodiment three:

As shown in Figure 6, the difference between this embodiment and Embodiment 1 is that the load 3 of this embodiment includes two groups of several LEDs connected in series, each group has N LEDs, and each group of LEDs is connected to a The 4 phases of the constant current control circuit are connected in series, and the two groups connected in series are connected in parallel with the voltage stabilizing circuit 2 to form a loop. Therefore, there are two constant current control ICs U2, U3 and their current sampling resistors in this embodiment. R11, R12, power MOSFET Q2, Q3. Of course, the loads 3 are not limited to two groups, and may also be multiple groups. In this embodiment, several constant current control circuits 4 can individually control the current of the LEDs in their respective groups.

The remaining features of this embodiment are the same as those of Embodiment 1.

Embodiment four:

As shown in Figure 7 and Figure 8, the difference between this embodiment and Embodiment 1 is that the LED load 3 of this embodiment includes four groups of LEDs connected in series, each group has N LEDs, and the constant current control IC U2 includes four output comparators OP1, OP2, OP3, OP4, the four output comparators OP1, OP2, OP3, OP4 are connected in parallel and the non-inverting input terminals are all connected to the reference voltage sampling point Vref, the constant The flow control IC U2 includes four sets of parallel output terminals G1, G2, G3, G4 and current feedback terminals CS1, CS2, CS3, CS4, each group of output terminals G1, G2, G3, G4 and current feedback terminals CS1, CS2 , CS3, CS4 are each connected in series with a group of LEDs, and at the same time, the number of the current sampling resistor and the power MOSFET is consistent with the number of the output comparator. In this embodiment, the current of each group of LEDs can be independently controlled by one constant current control circuit 4 .

The remaining features of this embodiment are the same as those of Embodiment 1.

The utility model can be widely used in the field of LED lighting.

Claims (10)

1. constant current constant voltage LED lighting circuit, comprise current rectifying and wave filtering circuit (1), voltage stabilizing circuit (2), LED load (3), alternating current passes through the described LED load (3) of flowing through behind the direct current that described voltage stabilizing circuit (2) voltage stabilizing becomes constant voltage again after (1) rectification of described current rectifying and wave filtering circuit and filtering become direct current, it is characterized in that: described constant current constant voltage LED lighting circuit also comprises constant-current control circuit (4), described constant-current control circuit (4) is connected with described voltage stabilizing circuit (2) and described LED load (3), described constant-current control circuit (4) comprises constant current control IC (U2), current sampling resistor (R11), power-type MOSFET (Q2), described constant current control IC (U2) comprises power positive end (VDD), earth terminal (VSS), output (G), current feedback terminal (CS), described power positive end (VDD) obtains voltage from described voltage stabilizing circuit (2), the two ends of described current sampling resistor (R11) respectively with described earth terminal (VSS), described current feedback terminal (CS) is connected, the grid of described power-type MOSFET (Q2) is connected with described output (G), the source electrode of described power-type MOSFET (Q2), drain electrode is connected with described current feedback terminal (CS) and described LED load (3) respectively.

2. LED light fixture energy-saving control circuit according to claim 1, it is characterized in that: described constant current control IC (U2) comprises generating circuit from reference voltage and at least one output comparator (OP1), described generating circuit from reference voltage comprises reference comparator (OP0), first triode (Q10), second triode (Q20), first resistance (R21), second resistance (R22), the 3rd resistance (R23), the base stage of described first triode (Q10) and described second triode (Q20) all with the output of described reference comparator (OP0), the in-phase input end of described output comparator (OP1) is connected and constitutes reference voltage sampling point (Vref), the collector electrode of described first triode (Q10) and described second triode (Q20) all is connected with described power positive end (VDD), the emitter of described first triode (Q10) is connected with described earth terminal (VSS) by described the 3rd resistance (R23), the emitter of described second triode (Q20) is by described first resistance (R21), described second resistance (R22) is in series and is connected with described earth terminal (VSS), the in-phase input end of described reference comparator (OP0) and described first resistance (R21), the dividing point of described second resistance (R22) is connected, the inverting input of described reference comparator (OP0) is connected with the emitter of described first triode (Q10), the output of described output comparator (OP1), inverting input respectively with the described output (G) of described constant current control IC (U2), described current feedback terminal (CS) is connected.

3. LED light fixture energy-saving control circuit according to claim 1 and 2 is characterized in that: described LED load (3) comprises at least one group of several LED that are in series.

4. constant current constant voltage LED lighting circuit according to claim 3 is characterized in that: every group of described LED all is in series with a described constant-current control circuit (4), and after the series connection some groups in parallel again is connected with described voltage stabilizing circuit (2).

5. constant current constant voltage LED lighting circuit according to claim 3 is characterized in that: each is organized to remake after the described LED parallel connection and as a wholely is in series with a described constant-current control circuit (4), and is connected with described voltage stabilizing circuit (2).

6. LED light fixture energy-saving control circuit according to claim 2, it is characterized in that: described constant current control IC (U2) comprises several output comparators (OP1, OP2, OP3, OP4), and several described output comparators (OP1, OP2, OP3, OP4) are in parallel and in-phase input end all is connected with described reference voltage sampling point (Vref).

7. constant current constant voltage LED lighting circuit according to claim 6, it is characterized in that: described LED load (3) comprises some groups of several LED that are in series, described constant current control IC (U2) comprises the output (G1, G2, G3, G4) and the current feedback terminal (CS1, CS2, CS3, CS4) of some groups of parallel connections, and each is in series every group of described output (G1, G2, G3, G4) and current feedback terminal (CS1, CS2, CS3, CS4) with one group of described LED.

8. constant current constant voltage LED lighting circuit according to claim 1 and 2 is characterized in that: described voltage stabilizing circuit (2) is a Switching Power Supply, and described voltage stabilizing circuit (2) comprises circuit of power factor correction.

9. constant current constant voltage LED lighting circuit according to claim 1 and 2, it is characterized in that: described constant current constant voltage LED lighting circuit also comprises EMI circuit (5), described EMI circuit (5) is connected between the input and described current rectifying and wave filtering circuit (1) of AC power, and described current rectifying and wave filtering circuit (1) adopts bridge rectifier.

10. constant current constant voltage LED lighting circuit according to claim 9; it is characterized in that: described constant current constant voltage LED lighting circuit also comprises short-circuit protection circuit (6), and described short-circuit protection circuit (6) is connected between the input and described EMI circuit (5) of AC power.

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