{386} Startup resistor calculation in SMPS design

in this video number {386} Startup resistor calculation in SMPS design, i discussed How to Calculate Startup Resistor or startup Resistance or bootstrap resistor or VCC resistor or Rstartup, to Design SMPS Switch Mode Power Supply. it is useful for calculation to design switch mode power supply (SMPS) for current mode controller using UC3842, uc3843, uc3844, uc3845 or KA3845 or KA3842 or KA3843 or KA3844 or any current mode smps which uses external mosfet to give a UVLO upper limit threshold charging at vcc capacitor. it provides a limited current of 0.5mA to 1mA to charge hold-up capacitor, when ic monitors that the voltage are at UVLO-ON threshold, then the IC takes soft start to drive transformer, so we take output at secondary and vcc / auxiliary / bias winding, which further provides operating current to the ic at 17mA 00:00 vcc startup resistor calculation in smps 00:51 what is startup circuit in SMPS 01:34 how to calculate startup resistance