Panasonic TH-37PX60U, Technical Manual

Page: 38 / 98

ACFB (Active Clamp Full Bridge Switching) Circuit
The PFC 395VDC is applied to the switching circuit (Q408, Q409, Q412, and Q413). The operation of this
switching circuit is controlled by the transformer T402 which is driven by the V-low power control IC, IC520.
1. A “high” from pin 15 of IC501 is used to turn on the power control IC (IC520) to energize the primary of
transformer T402 and allow the switching circuit to drive transformer T404.
2. The secondary circuit of transformer T404 outputs the Vsus, Vda, and 15V voltage sources.
3. The 15V is applied to the DC-DC converter (Q556). The output of Q556 is controlled by pin 4.
4. Pin 18 goes low to turn off Q524. When Q524 is off, 22V is applied to pin 4 of Q556 turning it on. At
this time pins 1, 2, and 3 of Q556 output the F_STB15V.
5. The F_STB15V is applied to pins 7, 8, and 9 of connector P6.
38