An electronic ballast with self-recovery and restart function of overvoltage protection

Abstract

The invention relates to an electronic ballast with overvoltage protection and self-recovery restart functions. The electronic ballast comprises a rectifying circuit connected with external alternating current input. The output of the rectifying circuit is connected with a filter circuit, the output end of the filter circuit is connected with a start circuit and a high-frequency conversion circuit, a protection circuit is further connected between the output end of the filter circuit and the start circuit, and the start circuit is connected with the control end of the high-frequency conversion circuit. The start circuit controls the high-frequency conversion circuit to be started for converting the direct current output by the filter circuit into a high-frequency power source, and the high-frequency power source output by the high-frequency conversion circuit lightens a modulator tube through a resonance circuit. According to the electronic ballast, the modulator tube can be protected after the electronic ballast is subjected to overvoltage, after the voltage returns to normal, outage does not need to be conducted on ballast, power supply to the modulator can be recovered automatically, and the modulator tube is lightened again.

Description

technical field [0001] The invention relates to an electronic ballast, in particular to an electronic ballast with a simple overvoltage protection function. Background technique [0002] Such as figure 1 As shown, it is a typical electronic ballast circuit diagram. As shown in the figure, the electronic ballast rectifies and filters the mains power, and then passes through a DC-AC converter (also known as a half-bridge inverter circuit) Generate high-frequency voltage to light fluorescent lamps, therefore, it usually includes a rectification filter circuit, a starting circuit, a high-frequency conversion circuit, a resonant circuit and a fluorescent lamp. [0003] The rectification and filtering circuit changes the 220V power frequency AC into about 300V DC to provide power Vdc for the electronic rectifier; the start-up circuit includes a resistor R1, a capacitor C1 and a bidirectional trigger diode D1. By charging the capacitor C1, the transistor VT2 is turned on ;The hig...

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Problems solved by technology

[0004] exist figure 1 On the basis of the circuit shown, in order to protect the fluorescent lamp, a protection circuit is usually added, but after the existing protection circuit performs overvoltage protection on the fluorescent lamp, if the voltage returns to normal, the ballast will not work, and the entire circuit needs to be cut off. The ballast can resume normal operation only after the power supply of the ballast is connected to the power supply again.

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