The Slope Compensation (SC) module is designed to provide the necessary slope compensation for fixed frequency, continuous current, current mode switched power supplies. Slope Compensation in a PIC® MCU device works by quickly discharging an internal capacitor at the beginning of each PWM period of the switching power supply control signal. An internal current sink charges this capacitor at a programmable rate. As the capacitor charges, the capacitor voltage is subtracted from the current reference voltage, producing a linear voltage decay at the required rate.
A block diagram of the Slope Compensation circuit is below.
The PIC16F753 is an example of a PIC® MCU device with slope compensation included.
The core of the SC module contains the following:
- on-chip capacitor in series with the voltage source
- shorting switch across the capacitor
- calibrated current sink
- one-shot pulse generator to ensure the switch is closed long enough to completely discharge the capacitor
The input to the SC module can be connected to the following signals:
The output of the SC module can be connected to the follow signals: