A Multi-Mode PFM/APWM Controlled Modular Resonant Converter for Magnetron Applications

A 300VDC/4kVDC 1600W modular Parallel-Input Series-Output (PISO) resonant converter has been designed for the Magnetron application. CLL resonant converters have been used in the high voltage circuit and an LLC resonant circuit has been utilized in the low voltage circuit to power up the Filament winding. To facilitate the design of the converter and achieve a high voltage level while meeting the isolation requirements, the power and the output voltage of the high-voltage (HV) terminal are split between multiple modules and each HV module generates 1kV at the output. To reduce the number of semiconductor devices, each HV module consists of a half-bridge inverter and a voltage-doubler diode rectifier. In addition, to reduce the overall size of the converter, planar magnetics along with a high switching frequency have been used in the resonant tank. Furthermore, to achieve a smooth soft-start and a wide voltage gain profile throughout the whole loading spectrum, a multi-mode PFM/APWM operation has been incorporated in the design of the control system. All the switches and diodes are able to achieve soft-switching to enhance the circuit efficiency. Experimental results are also provided on a proof-of-concept prototype to highlight the merits of the proposed converter.