DC-DC Buck Converter with Constant Off-Time Peak Current Mode Control

The paper presents an upgrade of the Peak Current Mode Control (PCMC) for a Buck DC-DC Converter. Constant Off-Time algorithm has a fixed off-switch phase, and, conversely to the typical PCMC, the duration of the switching period is free to change depending on the load and the battery voltage. In this way the instability issues, typical of a PCMC, are solved. The circuit is able to robustly sink 3 +/- 5%A average current from a car battery source, in a 3:5 V output voltage - 212kHz maximum frequency application. In addition, the circuit intrinsically provides protection against over-current and allows precise control over the current features (peak, average and ripple). The concept will result in a fully integrated system without external pad to sense the current, thanks to the proposed integrated sensing technique. The power consumption is also reduced since the current is read only during the on-switch phase.