Abstract: A double forward DC-to-DC converter with soft-PWM switching provides two voltage pulses to the output low-pass filter within one switching cycle (hence, the name double forward). The double forward DC to DC converter includes a transformer having a single primary winding and a two secondary windings. A main switch, under the control of a PWM control circuit, is connected is series with the primary winding. An auxiliary switch is coupled across with the main switch by way of a resonant capacitor. The resonant capacitor and auxiliary switch are used to automatically reset the transformer core while the main switch is on back to the voltage source connected to the transformer primary. A diode and snubber capacitor is connected across the drain-source terminals for both the main and auxiliary switches for minimizing switching losses. The current mirror used in prior art is abandoned in order to avoid the locked-up mode of operation.

Abstract: A full-bridge converter 10 is provided which performs soft switching based on pulse width modulated switching signals. The, converter 10 includes a primary side 12 and a secondary side 14 interconnected through a transformer 13. The primary side 12 includes a power source connected in parallel with leading and trailing legs 20 and 22, respectively. The leading leg 20 includes first and second switching transistors Q1 and Q2 connected in series, while the trailing leg 22 includes third and fourth switching transistors Q3 and Q4 connected in series. The switching transistors Q1-Q4 each include parasitic diodes D1-D4 and parasitic capacitances C1-C4. A control circuit 15 generates pulse width modulated (PWM) switching signals applied to gates G1-G4 of the transistors Q1-Q4. The control circuit 15 simultaneously turns on transistors Q1 and Q3 during a first energy transfer stage and simultaneously turns on transistors Q2 and Q4 during a second energy transfer stage.

Abstract: A DC to DC converter (50, 60, 70) that includes a switching circuit (10) responsive to a DC input, a magnetic amplifier controller (20) responsive to the switching circuit for providing an AC output, and an AC current to DC voltage rectifying circuit (30) responsive to the output of the magnetic amplifier controller for providing a DC output voltage. The magnetic amplifier controller includes a variable inductance (L1) that cooperates with the switching circuit to form a resonant DC to AC inverter (110) that provides to the magnetic amplifier controller a current whose amplitude is controlled by the variable inductance. The magnetic amplifier controller provides an approximately sinusoidal output current which is a function of the current input thereto, and the DC voltage output of the AC current to DC voltage rectifier is a proportional to the input current provided by the magnetic amplifier controller.