Pls help anybody knows the burnt resistor (R1) value of the Vcc of UC3844?

Discussion in 'General Electronics Chat' started by wkyong, Oct 27, 2009.

  1. wkyong

    Thread Starter Active Member

    Apr 29, 2008
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  2. SgtWookie

    Expert

    Jul 17, 2007
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    Extrapolating from the example design in the datasheet (ST Microelectronics, Figure 11, page 8)

    For 117VAC in, they're using a 56k Ohm 2 Watt resistor to supply the circuit's needs. The rectified AC would measure around 163v.
    For 560v, you'd then need a 193.4k resistor rated at 7W.

    You could get close by using 110k and 82k 5W resistors in series.
     
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