32W fluorescent lamp ballast analysis circuit diagram

Photocoupler

The circuit is shown below. The circuit is composed of a rectifying and filtering capacitor, a high-frequency oscillating circuit and an output load circuit. The AC 220V is rectified and filtered to output about 300V DC to supply power to the oscillating circuit. After the power is turned on, the power supply charges C3 through R5, so that Vc3 rises rapidly, so that VT2 quickly reaches saturation conduction; at this time, the VTI is cut off due to the feedback effect of T. Once VT2 is turned on, Vc3 falls, and the current flowing through L2 decreases, causing a negative voltage on both ends of L2. According to the principle of the same name, L1 gets the positive and negative feedback voltage, so that the VTI quickly saturates and conducts, and the positive feedback of T makes VT2 cut off quickly, so that the oscillation square wave is formed repeatedly (R6D6, R3D5 from the freewheeling action) . The load circuit consists 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 turned on, a large resonant comb is formed by C4, L4, etc. to flow through the filament, so that the hydrogen in the tube is ionized, and then the mercury becomes mercury vapor. The high voltage at both ends of C4 causes the vapor vapor to form an arc discharge, and the excitation tube Wall phosphors illuminate. After the lamp is lit, C4 basically does not work, and L4 acts as a choke.

Common faults 1. VTl, VT2 breakdown leads to D1-D4 being broken down, which will cause short circuit of power supply; 2. R4 bias is damaged; 3. L5.L6 is easily damaged in the oscillation circuit; 4. C24 due to load circuit The high voltage is easily broken down. Finally, the various 40W, 32W energy-saving fluorescent lamps and various ring lights that are currently seen on the market can be analyzed with reference to this circuit.