Multi-Frequency Oscillator with Dead Time in Electronic Ballasts

Abstract

The invention discloses a multi-frequency oscillator which has dead time and is applied to an electronic ballast, and mainly solves the problems of no pre-heating, insufficient pre-heating time and short service life of a pre-heating fluorescent lamp. The multi-frequency oscillator comprises a reference current and mirror image circuit (1), a control voltage generation circuit (2), a minimum current generation circuit (3), a discharge current control circuit (4), a charge current control circuit (5), an oscillator circuit (6) and a dead logic circuit (7); an output end of the control voltage generation circuit (2) is connected with the charge current control circuit (5) to generate gradually-changing charge current; the minimum current generation circuit (3) generates minimum charge current; the oscillation circuit (6) generates a time signal with gradually-variable frequency; and an output end of the oscillation circuit (6) is connected with the dead logic circuit (7) to generate a high-end control signal and a low-end control signal which are used for stabilizing the dead time. By the multi-frequency oscillator, the normal operation of the pre-heating fluorescent lamp can be ensured, the service life of the lamp can be prolonged, and the light efficiency is improved.

Description

technical field [0001] The invention belongs to the technical field of electronic circuits, and relates to an analog integrated circuit, in particular to a multi-frequency oscillator, which can be applied to electronic ballasts for preheating fluorescent lamps. Background technique [0002] Multi-frequency oscillators are widely used in electronic ballasts for preheating fluorescent lamps. By changing the oscillation frequency in different time periods, the preheating, ignition and normal lighting of fluorescent lamps can be realized. According to the characteristics of the preheating fluorescent lamp, its normal operation has three stages: 1. When the lamp circuit is at a higher frequency point f ph 2. When the frequency gradually decreases and tends to the natural frequency point f of the LCC series resonant parallel load circuit 0 3. Finally, make the fluorescent lamp work at a constant frequency f run , normally emit light under rated power. [0003] figure 1 It is a...

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Problems solved by technology

[0007] 1. The circuit structure is complex and not easy to integrate;

[0008] 2. The minimum operating frequency generated by the circuit is fixed. If the resistance characteristics of the filament are changed, the light efficiency of the fluorescent lamp will be deteriorated;

[0009] 3. When applied to electronic ballast chips, the output signal of the circuit needs to pass through the high-end dead zone generating circuit to obtain the high-end control signal and the low-end dead zone generating circuit to obtain the low-end control signal, and these two dead zone generating circuits are due to Inconsistently affected by process deviation and ambient temperature, resulting in unstable dead time

If the dead time is too small, the switching tube in the external inverter circuit cannot meet the zero-voltage conversion conditions when it is turned on, thereby increasing heat loss and even damaging the switching tube.

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