Peak and valley current mode control using double compensation ramp

Abstract

A method for controlling peak and valley of a controlled current in a switched mode power supply comprising a current mode control loop and being connected to an electrical power source. The method comprises providing an upper compensation ramp signal for controlling a peak of the controlled current, the upper compensation ramp signal being a sawtooth signal with a negative, falling, substantially linear slope (−S), starting periodically in time. The method further comprising providing a lower compensation ramp signal for controlling a valley of the controlled current, the lower compensation ramp signal being a sawtooth signal with a positive, raising, substantially linear slope (S), starting periodically in time. The method additionally comprising providing a reference voltage signal (V), to the control loop, and obtaining a signal indicative of the controlled current (I). Finally, the method comprises comparing alternatingly the signal indicative of the controlled current referenced to the reference voltage signal to the lower compensation ramp and the upper compensation ramp, respectively, to switch on or off the electrical power from the electrical power source into the control loop, and switching the electrical power with modulation at a fixed frequency (f).