This technical brief describes a microcontroller based Soft-Start Controller circuit for a switching power supply. Start-up is a stressful time for the power driver section of a switching power supply. Because the output voltage is initially zero, the feedback error initially jumps to its maxi- mum. The large feedback error then drives the loop filter to its limit, which drives the power switching transistors in the driver section of the power supply at their maximum rating. This condition continues until the output voltage of the power supply approaches its nominal value. If the load being driven by the power supply is capacitive, the problem is exaggerated due to the large transient currents required to charge the capacitive load. In extreme instances, the repeated high stress of start-up can result in catastrophic failures in the driver section, typically, the power MOSFET transistors or the power rectifiers. TB081 Soft-Start Controller For Switching Power Supplies Authors: John Day IMPLEMENTATION Keith Curtis Microchip Technology Inc. Hardware OVERVIEW The hardware for the soft-start circuit consists of three components; a PIC10F200 microcontroller, a 0.1 uF This technical brief describes a microcontroller based capacitor and a 10 k pull-down resistor. The ramping Soft-Start Controller circuit for a switching power supply. PWM function is implemented e……