A high resolution digital phase-shift modulation scheme for ultra-high frequency dual active bridge converters

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Abstract
The conventional digital PWM modules satisfy the resolution requirement of the phase-shift modulation signals for the dual active bridge type converters when the switching frequency is smaller than 25kHz. However, at ultra high frequency the resolution is too low to control the converter. A high resolution digital phase-shift modulation scheme to improve the resolution of the phase-shift angle by a factor around 50 is proposed for a 500kHz dual active bridge type converter. The implementation issues such as the micro-edge positioning and deadtime generation are discussed. The experimental measurement of the gate signal time change with different input angles verifies the high resolution of the phase-shift angle with the proposed scheme. When the maximum phase-shift angle is 30°, a resolution of 0.09% is obtained and the closed-loop digital control with presented high resolution modulation scheme is validated in a 500kHz prototype.

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