Impedance compensation circuit for LED driver and LED driver

Abstract

The invention relates to an LED driver and an impedance compensation circuit used for the same. The impedance compensation circuit comprises a voltage sampler and a time modulator, wherein the voltage sampler is used for sampling voltage of a bus; and the time modulator is used for adjusting equivalent resistance of a switching circuit and compensating capacitive reactance of an EMI capacitor through a control circuit according to the relationship between the sampled bus voltage and a threshold voltage. The LED driver comprises a thyristor, a rectifying circuit, the EMI capacitor, the control circuit, the switching circuit and the impedance compensation circuit, is used for compensating the capacitive reactance of the EMI capacitor, compensating input impedance of the LED driver after passing through the rectifying circuit and the EMI capacitor, and adjusting input current of the LED driver passing through the rectifying circuit. Compared with the prior art, the LED driver provided by the invention can provide sufficient ''holding current'', and has better compatibility for the thyristor.

Description

technical field [0001] The invention relates to the field of lighting driving circuits, in particular to an impedance compensation circuit for an LED driver and the LED driver. Background technique [0002] In traditional lighting (incandescent lighting) circuits, such as figure 1 As shown, the thyristor (Triac) dimming technology is widely used. Its schematic diagram is as follows figure 2 as shown, figure 2 for figure 1 Schematic of the equivalent circuit of the incandescent lighting circuit shown. [0003] Since the equivalent circuit of an incandescent lamp is a resistor, the compatibility of incandescent lamps with thyristors is very good. For LED lighting, its basic circuit is composed of a switching power supply, and since the switching power supply needs to pass the EMI test, a large capacitor needs to be connected in parallel at both ends, such as image 3 shown. [0004] image 3 It is the current LED lighting driving circuit diagram, the control chip can...

AI Technical Summary

Problems solved by technology

[0013] The defect of the prior art is: due to the existence of the EMI capacitor C1, the equivalent input impedance after the rectification bridge is not purely resistive, which will make the compatibility of the LED driver with the thyristor worse, which is reflected in problems such as flashing

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