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led driving circuit and constant current driver

A technology of LED driving and constant current, which is applied in the direction of lamp circuit layout, electric light source, lighting device, etc., can solve the problems of large size of inductor L1, unfavorable miniaturization of LED driving circuit, and high cost, and achieve the effect of miniaturization

Active Publication Date: 2018-02-27
HANGZHOU SILAN MICROELECTRONICS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In order to control the conduction time from being too small, the inductance of the inductor L1 is generally required to be large enough, otherwise the circuit will not work normally, and the volume of the inductor L1 will become very large at this time, which will increase the cost and is not conducive to the overall Miniaturization of LED drive circuits

Method used

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  • led driving circuit and constant current driver
  • led driving circuit and constant current driver
  • led driving circuit and constant current driver

Examples

Experimental program
Comparison scheme
Effect test

no. 1 example

[0060] refer to image 3 , image 3 The LED driving circuit of the first embodiment is shown. The LED driving circuit is a step-down structure and mainly includes: a constant current driver 200, a resistor R1, an input capacitor C2, a compensation capacitor C3, an output current sampling circuit 210, an inductor L1, and a capacitor C1 and freewheeling diode D1.

[0061] Wherein, the constant current driver 200 may include: a power switch circuit, an error amplifier 203 , a peak current comparator 202 , an off-time control circuit 201 , a logic and driving circuit 204 and a positive and negative level conversion circuit 205 .

[0062] The input terminal of the power switch circuit is connected to the voltage input terminal to receive the input voltage Vin, the output terminal of the power switch circuit is connected to the input terminal of the sampling resistor, and the control terminal of the power switch circuit is connected to the output terminal of the logic and driving c...

no. 2 example

[0080] refer to Figure 5 , Figure 5 The LED driver circuit shown with image 3 Basically the same, the main difference is that the second terminal of the current sampling circuit 210 is connected to the reference ground GND2 of the constant current driver 200, and the sampling voltage Vcs is output from the first terminal of the current sampling circuit 210, so that the sampling voltage Vcs is relative to the constant current driver 200 The reference ground GND2 is a positive voltage, and there is no need to perform polarity conversion through a positive and negative level conversion circuit.

[0081] But when Figure 5 In the shown LED driving circuit, since the output current Iout flowing through the output terminal Vout is the sum of the current flowing through the sampling resistor Rcs and the current flowing to the reference ground GND2 of the constant current driver 200, the accuracy of current control is relatively image 3 slightly lower.

no. 3 example

[0083] refer to Image 6 , Image 6 The LED driver circuit shown with image 3 Basically the same, the main difference is that the structure of the power switch circuit in the constant current driver 200 is different.

[0084] In the third embodiment, the power switch circuit includes a third power transistor M3, a fourth power transistor M4 and a built-in sampling resistor Rcs2 connected in parallel. Wherein, the drain of the third power transistor M3 is connected to the voltage input terminal to receive the input voltage Vin, its source is connected to the first input terminal of the peak current comparator 202, and its gate is connected to the output terminal of the logic and driving circuit 204. and the drive circuit 204 to control on and off; the first end of the built-in sampling resistor Rcs2 is connected to the source of the third power transistor M3, and its second end is connected to the input end of the sampling resistor; the drain of the fourth power transistor M...

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Abstract

The present invention provides an LED driving circuit and its constant current driver. The driver includes: a power switch circuit, the input terminal receives the input voltage, and the output terminal is connected to the sampling resistor input terminal; the error amplifier connects the sampling voltage with the preset first reference The voltage is compared to generate an error signal; the peak current comparator compares the conduction voltage with a preset second reference voltage, and its output terminal generates a shutdown signal in response to the conduction voltage reaching the second reference voltage, and the conduction voltage corresponds to The conduction current during the turn-on period of the power switch circuit; the turn-off time control circuit determines the turn-off time according to the error signal, and generates a turn-on signal in response to the timing reaching the turn-off time; the logic and drive circuit turns on the power in response to the turn-on signal The switch circuit turns off the power switch circuit in response to the shutdown signal. In the case of very small output current, the present invention can still use a small inductance to realize constant current control, which is beneficial to realize miniaturization of the LED driving circuit.

Description

technical field [0001] The invention relates to switching power supply technology, in particular to an LED driving circuit and a constant current driver. Background technique [0002] refer to figure 1 , the traditional source-driven step-down LED drive circuit mainly includes a constant current driver 100, a resistor R1, a freewheeling diode D1, an output load capacitor C1, an input capacitor C2, an inductor L1, a first power switch M1, and a sampling resistor Rcs , wherein the constant current driver 100 includes a zero-crossing detection circuit 101, a logic sum drive circuit 102, a comparator circuit 103, an RS flip-flop circuit 104 and a second power switch M2. When the first power switch M1 is turned on and the second power switch M2 is also turned on, the input current flows through the output load capacitor C1 and the output terminal, the inductor L1, the second power switch M2, the first power switch M1, and the sampling resistor Rcs, The current on the inductor L...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H05B37/02
Inventor 姚云龙
Owner HANGZHOU SILAN MICROELECTRONICS