A method to improve a resolution of digital PWM generator for DC-DC converter control

In recent years, digitization of all control parts in switching power supplies including PWM generators is progressing for demands such as intelligent performances and common use of hardware, etc. Then, a problem is in the resolution of digital PWM generators for improving control performances. Since the digital PWM generator is constituted using a counter, a carrier wave turns into a stairs wave, and step amplitudes is decided with a clock cycle. When the clock cycle is fixed, the resolution becomes low as the switching frequency becomes high. Consequently, the accuracy of output voltage becomes bad. In this paper, a method for remarkably improving the resolution of the digital PWM generator using the pulse composite technique is proposed. The method is realizable by some parts and easy computation, and is applied to the digital PWM generator built-in DSP. The usefulness and practicality are verified by experiments