MC7773N6 Datasheet, PDF (6/11 Pages) Cystech Electonics Corp. – Current Mode PWM Controller

CYStech Electronics Corp.
Spec. No. : C151N6
Issued Date : 2012.11.08
Revised Date :
Page No. : 6/11
OPERATION DESCRIPTION
Over-view description
The MC7773N6 includes all necessary function to build an easy and cost effective solution for low power supplies to
meet the international power conservation requirements.
Start-up current
Startup current of MC7773N6 is designed to be very low so that VDD could be charged up above UVLO (exit)
threshold level and device starts up quickly. Also a large value startup resistor can be used to minimize the power
loss.
Green Mode Operation （Patent）
At light load or no load condition, the switch loss become the major loss of the power supply, to reduce the power
wasted in light and no load condition, based on a special designed voltage controlled oscillator, green mode
operation of the power supply can be achieved by using MC7731N6. The controller will judge the load condition
based on the voltage of FB pin. In light load the FB voltage will decrease, when VFB is lower than a set threshold
voltage, a FB depending time (TR2) will be generated by the oscillator and decrease the operating frequency of the
power supply, the minimum frequency is set about 22kHZ. The function block and the working waveform can be
depicted as below:
When VFB decreases further, the power supply will enter into burst mode operation to decrease the power
consumed at no load condition. Besides there is no audible noise in any load condition.
MC7773N6
CYStek Product Specification