Protective circuit when lamp tube life end in electronic ballast

Abstract

This invention discloses a protection circuit in the electronic ballast at the end of the lamp life time including a first comparator, a second comparator and a MOS tube for automatic restart, among which, the positive of the first comparator samples the negative half-cycle, its negative terminal is the reference point, positive of the second comparator is connected to the negative terminal of the first comparator, which samples the positive half-cycle of the lamp voltage. Output ends of the two comparators are connected to the power supply end of an oscillation drive circuit by the thyristor. When a lamp ends its life time, the voltage at positive and negative half-cycles reduces, the two comparators detect such variance and trigger to conduct the thyristor to let the drive circuit stop oscillating, so the product is protected, when the lamp is changed, MDS is turned on, so the conducted circuit of the thyistor is cut off to stop the thyristor, and the product is restarted after changing a lamp.

Description

technical field [0001] The invention relates to a protection circuit of an electronic ballast, in particular to a protection circuit for a lamp tube in the electronic ballast at the end of its service life. Background technique [0002] Today's electronic ballasts are more and more widely used, and the requirements for electronic ballasts are getting higher and higher, especially some protection functions, especially the appearance of T5 and other small-diameter products, which have a great impact on the end of life and lifeless The protection requirements of the lamp are particularly prominent. At present, the protection when the lamp is end of life or no lamp is connected, and the technology of automatic restart after the lamp is replaced usually uses a chip circuit. For example, the ballast protection circuit of PHILPS uses a 2010T chip. technology, but the circuit is more complex. Contents of the invention [0003] The present invention aims to solve the above-mention...

AI Technical Summary

Problems solved by technology

[0002] Today's electronic ballasts are more and more widely used, and the requirements for electronic ballasts are getting higher and higher, especially some protection functions, especially the appearance of T5 and other small-diameter products, which have a great impact on the end of life and lifeless The protection requirements of the lamp are particularly prominent. At present, the protection when the lamp is end of life or no lamp is connected, and the technology of automatic restart after the lamp is replaced usually uses a chip circuit. For example, the ballast protection circuit of PHILPS uses a 2010T chip. technology, but the circuit is more complex

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