Development of Integrated Magnetic Circuits for Low-Voltage, High-Current Applications

A lot of low voltage output applications require relatively high input voltage, e.g., 48 V, 100 V, etc., because high voltage is more efficient in distributing current. To minimize the power loss and protect the output load from possible over-voltage due to the failure of the semiconductor devices, a step-down isolation transformer is required in this type of low voltage power supply design. In the past, a lot of research efforts have been carried out to improve the efficiency of power converters [C1-C28]. There are several popular topologies for low voltage converter applications: i. Active clamp forward converter with synchronous rectifiers (ACFCSR) [C2, C3, ii. Half-bridge center-tapped rectifier with synchronous rectifiers (HBCTRSR) and asymmetrical duty cycle control [C9, C19, C20, C23]. iii. Half-bridge current doubler rectifier with synchronous rectifiers (HBCDRSR) and asymmetrical duty cycle control [B16, C7]. iv. Forward current doubler rectifier with synchronous rectifiers (FCDRSR) [B18, Operated at 50% duty cycle, all of these topologies can provide the optimum secondary waveform for direct self-driven synchronous rectifications. All of the card-mounted power modules require very high efficiency for low voltage and high current output because of limited spacing for the heat sink. An application example seen in the aircraft power system, Example 2-1, is the initial driving force of the topology development in this work because it has the most stringent requirements in every physical dimension (profile and footprint) and efficiency. In the following discussion, this