Closed-loop control circuit for LED constant current drive circuit

A closed-loop control circuit and constant-current drive technology, applied in electric lamp circuit arrangement, electric light source, lighting device, etc., can solve the problems of LED output current deviating from the theoretical value, affecting the constant current accuracy of LED output current, etc., so as to improve the anti-interference ability. and stability, improve line and load regulation, reduce losses

CN104333936AActive Publication Date: 2015-02-04深圳天源中芯半导体有限公司
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2015-02-04

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Abstract

The invention discloses a closed-loop control circuit and method for an LED constant current drive circuit and belongs to the technical field of circuit control. The closed-loop control circuit comprises an output average current sampling unit, an output average current reference voltage unit, an error amplifier unit, a comparator unit, an inductance zero current detection unit, a valley bottom conduction detection unit and a logic and drive unit. According to the closed-loop control circuit for the LED constant current drive circuit, LED output average current sampling voltage average value is allowed to be equal to the output average current reference voltage through the closed-loop control mode, thereby realizing constant-current control of LED output average current, and improving precision of the LED output constant current; and a system can automatically carry out corresponding adjustment according to the change of application conditions through closed loop feedback, thereby effectively improving linear and load adjustment capability of the LED output current and improving anti-interference capability and stability of an LED driving power source.
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Description

[0001] technical field

[0002] The invention belongs to the technical field of circuit control, and in particular relates to a closed-loop control circuit for an LED constant current drive circuit.

[0003] Background technique

[0004] In the non-isolated LED constant current drive power supply, the step-down LED constant current drive circuit is the most widely used one. At present, the step-down LED constant current drive circuit generally adopts an open-loop control method combining inductor peak current detection and inductor current zero-crossing detection to achieve the purpose of LED constant current output.

[0005] figure 1 It is a traditional step-down LED constant current drive circuit that adopts open-loop control mode, usually including: rectifier bridge D1~D4, input filter capacitor C1, power supply resistor R1, power supply capacitor C2, control chip U1, peak current sampling resistor R2, Power switch tube Q1, inductor L1, freewheeling diode D5, output ca...

Examples

Embodiment 1

[0035] Such as figure 2 Shown is Embodiment 1 of the closed-loop control circuit for LED constant current drive circuit of the present invention. The closed-loop control circuit for LED constant current drive circuit includes: output average current sampling unit 201, output average current reference voltage unit 202, error amplifier unit 203, comparator unit 204, inductance zero current detection unit 205, valley conduction detection unit 206 and logic and drive unit 207.

[0036] The LED constant current drive circuit also includes: a rectifier bridge 208, an input filter capacitor 209, a starting resistor 210, a power supply capacitor 211, an inductance auxiliary winding 212, resistor divider resistors 213, 214, a rectifier diode 215, and a peak current sampling resistor 216 , a power switch tube 217 , a freewheeling diode 218 , an inductor 219 , an output capacitor 220 , an output resistor 221 and an LED load 222 .

[0037] During the conduction period of the power swit...

Embodiment 2

[0040] Such as Figure 4 Shown is Embodiment 2 of the closed-loop control circuit for the LED constant current drive circuit of the present invention. The closed-loop control circuit for LED constant current drive circuit includes: output average current sampling unit 401, output average current reference voltage unit 402, error amplifier unit 403, comparator unit 404, inductor zero current detection unit 405, valley conduction detection unit 406 and logic and drive unit 407 . The LED constant current drive circuit also includes: rectifier bridge 408, input filter capacitor 409, start resistor 410, power supply capacitor 411, resistor divider resistors 412, 413, rectifier diode 414, power switch tube 415, peak current sampling resistor 416 , freewheeling diode 417 , inductor 418 , output capacitor 419 , output resistor 420 and LED load 421 .

[0041] Specifically, the design of the closed-loop control circuit of this embodiment is the same as that of Embodiment 1, and the wo...