Pulse width modulation synchronisation of switched mode power converters

摘要

The present invention is directed to switch mode power supplies operating in a master-slave configuration and provides synchronisation of PWM outputs from the master and the slave devices to avoid problems such as the generation of beat frequencies. The synchronisation procedure involves coarse and fine stages. The procedure includes the steps of i) determining if the frequency of the slave is within a predetermined range of a sync signal from the master, ii) adjusting the slave frequency and then iii) phase aligning the slave to the master. Comparison of slave and master frequencies may be carried out by counting sync pulses. The method provides the advantage that the slave can re-synchronise if synchronisation with the master is lost.