Multi-discharge lamp parallel driving circuit and driving method

Abstract

The invention relates to a multi-discharge lamp parallel driving circuit which comprises a control device. The control device comprises a switch driving circuit, a PWM control circuit, a self-adaptingfrequency sweep circuit, a terminal voltage detecting circuit, a lamp current detecting circuit and a lamp open-circuit detecting circuit, wherein the terminal voltage detecting circuit is coupled between a load network and the self-adapting frequency sweep circuit and outputs a terminal voltage sampling signal to the self-adapting frequency sweep circuit; the lamp current detecting circuit is coupled between the load network and the lamp open-circuit detecting circuit and outputs a lamp current sampling signal to the lamp open-circuit detecting circuit; the lamp open-circuit detecting circuit is coupled between the lamp current detecting circuit and the self-adapting frequency sweep circuit and outputs a corresponding lamp open-circuit signal to the self-adapting frequency sweep circuit;the self-adapting frequency sweep circuit is coupled with the PWM control circuit, the lamp open-circuit detecting circuit and the terminal voltage detecting circuit and outputs a self-adapting frequency sweep signal to the PWM control circuit; and the PWM control circuit is coupled between the switch driving circuit and the self-adapting frequency sweep circuit and outputs a switch control signal to the switch driving circuit.

Description

technical field [0001] The invention relates to a driving circuit and a driving method for multiple discharge lamps, in particular to a parallel driving circuit and a driving method for multiple discharge lamps. Background technique [0002] Nowadays, discharge lamps, such as cold cathode fluorescent lamps (Cold Cathode Fluorescent Lamp, CCFL), are widely used as backlight sources for liquid crystal displays (Liquid Crystal Display, LCD). CCFL needs a very high terminal voltage (such as one or two thousand volts) to light it, and once it is lit, its terminal voltage will drop to a lower value (such as several hundred volts). CCFL needs a driving circuit to provide high-frequency AC driving voltage and stable lamp current. Generally speaking, a CCFL driving circuit includes a control device, a switching device, a transformer and a resonant device. [0003] When a CCFL is removed, malfunctions, or extinguishes due to environmental reasons, it presents an open circuit conditi...

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Problems solved by technology

The other is to set the operating frequency of the driving circuit to a preset frequency higher than the normal operating frequency when an open circuit of the CCFL is detected, so as to increase the terminal voltage V out , but in the multi-lamp parallel drive circuit with capacitive current sharing, because the load characteristics are different when different numbers of lamps are open, the preset frequency under this method is difficult to determine, and it cannot meet the requirements of various open circuits with different numbers of lamps. Happening

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