Service manual

Principles of Operation
Chopper-type switching regulator circuit
The power supply circuit includes a chopper-type switching regulator. The step
down circuit operates as follows:
Figure 2-10. Step Down Circuit
Figure 2-10 shows the chopper-type step down switching regulator circuit. When
the transistor is on, voltage Vi is applied to coil L and capacitor C. Load current I1
flows and electromagnetic energy Wl accumulates in choke coil L. When the
transistor goes off, energy Wl is applied to the load via flywheel diode D.
Therefore, output voltage Vo is the average value:
LQ-200/AP3000
2-11