Start -Up Circuit: Vin - Daewoo DTH-29U3 Service Manual

CP830F Service Manual

5.9.2.1 Start -up Circuit: VIN

The start-up circuit is used to start and stop the operation of the control IC, by detecting a voltage appearing at VIN pin
(pin 4).
When the power switch is pushed on, VIN increases slowly. During this time, C806 is charged through R802.
As soon as VIN reaches 16V, the STR-F6654 control circuit starts operating. Then, VIN is obtained by smoothing the
winding voltage which appears between pin6 and pin7 of the SMPS transformer.
As this winding voltage does not increase to the set voltage immediately after the control circuit starts operating, VIN
starts dropping. However, as this winding voltage reaches the set value before VIN voltage drops to the shutdown
voltage (at 11V), the control circuit continues operating (see below VIN voltage at start-up). R805 resistor prevents that
VIN pin voltage varies according to the secondary side output current.
VIN must be set higher than the shutdown voltage (VIN (off) = 11Vmax) and lower than the O.V.P.
(overvoltage protection) operating voltage
(VOVP = 20.5Vmin)
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