Circuit Schematic Fluorescent Lamp Driver with Starter

Light. - Here is Circuit Schematic Fluorescent Lamp Driver with Starter. About the CD4049 there are contradictional info’s. My data book from 1981 states that pin 16 is “3 to 15 V but more than at pin 1 ” and it works fine when connecting them (voltage is equal). The infos in www.alldatasheet.com indicate that pin 16 is not connected. There must have been a change some time ago. There are 6 inverters. The first two are connected to form an oscillator, relevant for the frequency is the 100k resistor, the 330p capacitor and the potentiometer. The 2 diodes on the trimmer makes the impulse/period-relation variable. The four parallel inverters are just to drive the driver transistors in a push-pull configuration.


Figure 1. Schematic Fluorescent Lamp Driver with Starter
(Source: www.electroschematics.com)
The transformer is the key component. The winding data are given in the schematic. I used Teflon tape for insulation. Remember that if you stretch it, it becomes thinner. You need an adequate insulation between primary and secondary, and a very good insulation between secondary and the “upper” heater winding. This is because there are several hundred volts over the capacitor.

The capacitor is needed to keep off DC content, because the lamp will try to generate a DC-content and pre-magnetize the core and bring it into an unwanted operational state. The lamp partly behaves like a diode. This is one of the odd features of fluorescents, in addition to having a nonlinear response to voltage and frequency.

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