Energy-saving lamp electronic ballast

The circuit of a 16W2D single-ended internal start electronic ballast dedicated to energy-saving lamps is shown in Figure 1-60. The circuit consists of a radio frequency interference
filter , a zinc oxide varistor protector, a bridge rectifier, a high-frequency oscillator, and an LC connected in series It is composed of output stage and other parts.
    The radio frequency interference filter is composed of inductors Ll, ​​L2 and capacitor Cl. At the same time, capacitor Cl also has
a certain correction effect on the power factor of the circuit. RV is a zinc oxide varistor. When the power grid is out of phase or the voltage increases unexpectedly, it can be quickly turned on, causing
the fast fuse FU to blow, thereby protecting the electronic ballast and lamp from damage.
    The bridge rectifier circuit is composed of VDI ~ VD4, and then filtered by the C2 capacitor. The high-frequency oscillator uses a transformer-coupled self
-oscillation circuit. At the moment when the power is turned on, although the circuit parameters of the VTI and VT2 loops are exactly the same, due to
the discrete nature of the components, one of the transistors will inevitably be turned on first, and then rely on The coupling effect of transformer T2 causes the other
transistor to conduct, and the first conductive transistor changes from the on state to the off state. Through the positive and negative periodic changes of T2's magnetic flux
, VTI and VT2 are turned on and off in turn to saturation, and oscillation is quickly established. Once the oscillator circuit is excited, the high-frequency signal
passes through the series circuit composed of choke coil L3 and capacitor C7, causing series resonance. As a result, a high
resonant voltage is generated at both ends of C7 , and the lamp H is started and ignited at one time. Once the lamp is ignited, the Lc series circuit is detuned. As long as the circuit component parameters
are appropriately selected, the lamp can work in the normal rated state.