TRIAC dimmable LED driver circuit

Abstract

A TRIAC dimmable light-emitting diode (LED) driver circuit is disclosed, compromising: An alternating-current (AC) voltage connected to a rectifier bridge; An LED load, which is connected to an inductor or a transformer, a power MOS transistor, a low voltage MOS transistor and a current sensing resistor. The LED driver also compromises: a peak current comparator which is used to compare the voltage between a current sensing resistor and a reference voltage; a maximum on-time timer, which is used to detect the on time of the low voltage MOS transistor. When the voltage on the current sensing resistor is higher than the reference voltage or the on time of the low voltage MOS transistor reaches the preset time of the maximum on-time timer, the low voltage MOS transistor is turned off.

Description

CROSS-REFERENCE TO RELATED DOCUMENT[0001]The present application claims priority from CN 201310257527.8 filed on Jun. 26, 2013, the disclosure of which is hereby incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates generally to Light-Emitting Diode (“LED”) driver circuits, and in particular, to TRIAC dimmable LED driver circuits.BACKGROUND OF THE INVENTION[0003]FIG. 1 (Prior Art) is a diagram of a conventional TRIAC dimmable LED driver. As shown in FIG. 1, an alternating-current (AC) voltage source 101 is in series with a TRIAC dimmer 102, and is connected to the input terminal of a diode bridge 103. The diode bridge 103 rectifies the input AC voltage and generates a sinusoidal voltage on capacitor C1. Resistor R4 and capacitor C2 generates a DC voltage to start up the control IC 104.[0004]The transformer T1 has three windings, including a primary winding connected with capacitor C1 and the drain of the power M1, a secondary winding connected wi...

AI Technical Summary

Benefits of technology

The present invention provides a TRIAC dimmable LED driver circuit which eliminates the bleeper circuit and reduces system complexity and cost. The circuit eliminates the need for a separate bleeder circuit and uses the converter input current to provide the holding current for the TRIAC dimmer. Additionally, the circuit drives the power MOS transistor and reduces the driving current of the power. This results in a simple, efficient, and widely compatible TRIAC dimmable LED driver circuit.

Problems solved by technology

First, the bleeding resistor R1 and bleeding switch M2 dissipate too much power, losing the LED driver efficiency and inducing too much heat . The LED driver suffers from high temperature and low reliability.

Second, the control circuit is complex, and the system cost is relatively high.

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