Pulsewidth-Modulator-Based Transfer Function Measurement Method for Variable Frequency-Controlled Half- and Full-Bridge Converters

Variable frequency control is widely used in half-bridge and full-bridge converters. Measuring the switching-frequency-to-output-voltage transfer function is critical to verify a derived model and guide the design of closed-loop parameters. The existing voltage-controlled-oscillator-based measurement method is complicated in circuit implementation and the accuracy could be affected by the bandwidth of the voltage-controlled current source. In this letter, a pulsewidth-modulator-based measurement method is proposed, which is much simpler in the circuit and more accurate. The principle of this method is analyzed in detail. Finally, the experimental results of a half-bridge and a full-bridge series-series compensated wireless power transfer systems are presented to verify the proposed method.