32W fluorescent lamp ballast circuit diagram

The circuit is shown below. The circuit consists of three parts: rectifier filter capacitor, high-frequency oscillation circuit and output load circuit.

AC 220V is rectified and filtered to output about 300V DC to provide power for the oscillation circuit. After starting up, the power supply charges C3 through R5, causing Vc3 to rise rapidly, so that VT2 quickly reaches saturation and conduction; at this time, VTI is cut off due to the feedback effect of T. Once VT2 is turned on, Vc3 decreases and the current flowing through L2 decreases, causing a negative voltage on both ends of L2. According to the principle of the same terminal, L1 gets the upper positive and lower negative feedback voltage, so that VTI quickly saturates and conducts. At the same time, the positive feedback effect of T causes VT2 to quickly cut off, and so on, forming an oscillating square wave over and over again (R6D6 and R3D5 play the role of freewheeling) . The load loop is composed of L3, L4, and C4. The high-frequency oscillating square wave generated by VTI and VT2 is added to the load as an excitation source by L3. Before the lamp is lit, a large resonant electric comb formed by C4, L4, etc. flows through the filament, ionizing the hydrogen in the tube and turning the mercury into mercury vapor. The high voltage at both ends of C4 causes the mercury vapor to form an arc discharge and excite the tube. Wall phosphor glows. After the lamp is lit, C4 basically has no effect, and L4 plays a blocking role at this time.

Common malfunctions

1. The breakdown of VTl and VT2 will lead to the breakdown of D1-D4, which will cause a short circuit in the power supply;

2.R4 offset is damaged;

3. L5 and L6 in the oscillation circuit are easily damaged;

4. C4 in the load circuit is easily broken down due to high voltage.

Finally, please note that all kinds of 40W, 32W energy-saving fluorescent lamps and various ring lights currently on the market can be analyzed with reference to this circuit.