Power Control for Pulse-Density Modulation Resonant Converters

PDM can be used to drive resonant power converters and is a good alternative to pulse width modulation (PWM). Its main advantages are its simplicity and that it allows power device´s zero-current (or voltage) switching (ZCS or ZVS), while performing load power regulation. This technique is suitable for designing power converters that show an overall good power factor and a low total harmonic distortion (THD). PDM can be used to drive resonant (series or parallel) power converters. Frequently, these converters are used in induction heating applications and they are required to operate at high frequencies. Despite its advantages, PDM converters´ output power response is discrete and often nonlinear. This leads to strategies to realize a reliable load power regulation. This paper presents the implementation of a power control for pulse density modulation (PDM) power converters. The strategy used to drive the converter is entirely digital. A feed-back control technique that combines an anticipation algorithm and a hysteresis control is used in order to achieve proper load power regulation. A digital signal controller is employed to drive the whole system. Output power is calculated by acquisition and filtering of current flowing through the load. Simulation and experimental results are in good agreement and show that power regulation can be accurately made over a wide range of power outputs