A Control Technique for Galvanically Isolated DC–DC Converters with a Single Channel

This paper presents an on–off power control technique for galvanically isolated dc–dc converters, which implements a feedback control loop for power regulation on the same isolation transformer used for power transfer. To this aim, the power oscillator is controlled with a PWM scheme, and the control signal is transmitted through the galvanic barrier by using an ASK modulation that acts on the secondary winding of the isolation transformer. The key building block of the proposed architecture is a PLL that allows the reconstruction of the PWM control signal when the power oscillator is turned off and data transmission is disabled. The effectiveness of the proposed power control architecture is validated by designing an isolated dc–dc converter based on a thick polyimide transformer. It complies with reinforced isolation while addressing the power requirements of applications such as low-power sensor interfaces, medical devices, and housekeeping power, e.g., gate drivers or controllers for power converters. At a 20 V output voltage, 110 mW isolated output power is delivered. The dc–dc converter also provides PWM power regulation against PVT variations.