Dell 1909Wf, Руководство по обслуживанию

Страница: 9 / 71

Service Manual
8
2.1.2)Output Circuit and Protection Circuit:(fig.3)
Fig.3
The transformer (T1) secondary winding leakage inductance and output
capacitance(C19) forms a lower pass filter,which converts the square-wave driving
signal into a sinusoidal output voltage signal for CCFL.
The voltage signal on negative pole of ZD1 sensed through R14 comes to Pin8 of
U1-ISEN (Lamp Current Detection & Control). The CCFL current is detected through
R14 and reaches a regulated value. The CCFL current detected at resistor R14 is
converted to a voltage level and input to the ISEN pin. Once the voltage at the ISEN
pin reaches the lamp on threshold, the IC switches from the striking mode to the
normal operation mode and the PWM dimming control is activated.
C6 is used to dump noise. Once the CCFLs are ignited and current is sensed
through resistor R14 ,capacitor C3 performs the loop compensation function. The