Control circuit and control method for light emitting diode (LED) driver

Abstract

The invention relates to a control method for a control circuit of a light emitting diode (LED) driver. The LED driver has a flyback topological structure; the control circuit is positioned on a primary side of a transformer and comprises a sampling circuit, a conduction time detection circuit of an output diode on a secondary side of the transformer, a regulation signal generation circuit and a pulse width modulation (PWM) control circuit, wherein the sampling circuit is used for acquiring a sampling signal for representing an output signal of the LED driver on the primary side of the transformer; the conduction time detection circuit is used for detecting conduction time of the diode; the regulation signal generation circuit is used for regulating conduction time of the sampling signal,a reference source and the output diode on the secondary side of the transformer and generating a regulation signal; and the PWM control circuit is used for receiving the regulation signal and generating a control signal to control the turning on and turning off of a switching device in the LED driver, so stable output of the LED driver is retained.

Description

technical field [0001] The invention relates to the field of electronic technology, in particular to a control circuit of an LED driver and a control method thereof. Background technique [0002] With the continuous innovation and rapid development of the lighting industry, coupled with the increasing importance of energy saving and environmental protection, LED lighting, as a revolutionary energy-saving lighting technology, is developing rapidly. However, since the brightness of an LED lamp is related to the light output intensity parameter, it is directly proportional to its current and forward voltage drop, and changes with temperature. Therefore, LEDs need an additional circuit to generate a constant current to drive them. Such as figure 1 As shown, it is a functional block diagram of a traditional off-line constant current driver for LEDs, which is realized by an isolated flyback converter with an output current regulation circuit. The main structure of the LED drivi...

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Problems solved by technology

[0005] (1) For long-life power supply applications, due to the aging of the optocoupler over time, the current transmission ratio gradually decreases, which has an adverse effect on the stability and service life of the circuit;

[0006] (2) Moreover, in such an implementation, the number of components is large, which means that larger board space, higher cost, and lower reliability are required;

[0007] (3) The added induction detection circuit additionally increases the power consumption of the circuit and reduces the efficiency of the constant current regulation power supply;

[0008] (4) For today's applications, the efficiency and energy saving requirements of LED drivers are becoming more and more important, and LED applications also require smaller sizes, so the traditional circuits that sample the above implementation methods can no longer meet the relevant requirements

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