Fluorescent lamp electronic ballast circuit diagram

How the circuit works

The fluorescent lamp electronic ballast circuit consists of a rectifier filter circuit, a high-frequency oscillation circuit and an output circuit.

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In the circuit, the rectifier filter circuit consists of rectifier diodes VD1 to V D4 and filter capacitors C1 and C2; the high-frequency oscillator consists of transistors vi, V2, resistors R1 to R7, capacitors C3, C4, C6, diodes VD5 to V D8 and It is composed of high-frequency transformer T (W1-W3 are wound around the same magnetic ring to form a high-frequency transformer); the output circuit is composed of chokes L1, L2 and capacitors C'L-C10.

After power on, the AC 220V voltage is rectified by VD1-VD4 and filtered by Cl and C2, and a DC voltage of about 280V is generated at both ends A and C, which is used as the working power supply of the high-frequency oscillator. Under the action of the capacitors C3, C4, C6-C10 and the W1-W3 windings of T, the transistors V1 and V2 quickly enter a high-frequency oscillation state of alternate conduction and cutoff , producing an approximate sine wave between points A and B. The high-frequency alternating voltage of the waveform is added to the filaments of the fluorescent tubes ELI and EL2 through L1, LZ and C7 to C10, causing ELI and EL2 to light up. After ELI and EL2 are lit, the internal resistance of their filaments drops sharply, and the high ignition voltage at both ends of C9 and C10 drops to normal values, maintaining the normal light emission of the fluorescent tube.