PREHEATING CIRCUIT APPLIED TO FLUORESCENT LAMP ELECTRONIC BALLAST

摘要

The present invention discloses a preheat circuit for electronic ballast of fluorescent lamp, comprising a diode and a first capacitor which are connected in series with each other and then connected in parallel with the secondary winding of magnetic loop, a third resistor and a second capacitor which are connected in series with each other and then connected in parallel with the first capacitor, a first control switch that is connected in parallel with the series branch composed of the diode and the first capacitor, and a second control switch that is connected in parallel with the series branch composed of the third resistor and the second capacitor; when the self-excited magnetic loop driving circuit starts up, the first capacitor and the second capacitor will be charged in turn, and the first control switch and the second control switch will be alternately closed and opened. The preheat circuit provided in the present invention drives the electrical current in the secondary side of the magnetic loop via the control switch to change the working frequency of the half-bridge circuit, so as to control the voltage between both ends of the lamp, thereby the preheat startup of lamp is achieved; there is no additional energy consumption and therefore the efficiency of ballast is improved..