Quasi-synchronous, magnetic amplifier regulated dc-dc converter

#1. Field of the Invention

#This invention relates to switched-mode power supplies and more specifically to magnetic amplifier regulated dc—dc converters.

#2. Description of the Related Art

#FIG. 1 is a schematic diagram of a prior art full-wave, mag-amp regulated dc—dc converter circuit;

#FIG. 2 is a schematic diagram of a circuit in accordance with a first embodiment of the invention;

#FIG. 3 is a schematic diagram of an amplifier circuit which is suitable for use as the magnetic amplifier feedback circuit in FIG. 1;

#The regulated power supply circuit of the invention includes a half or full bridge converter coupled through a transformer to one or more output circuits, each output circuit including a pair of magnetic amplifier delay devices (saturable core inductors). The magnetic amplifier delay devices are connected in series with a pair of switching devices operating as synchronous rectifiers. The outputs of the switching devices, as well as a “freewheeling” diode, provide current to an output inductor, which in turn provides output current for a load.

#In accordance with the invention, the switching devices operate as synchronous rectifiers in combination with the non-synchronous, freewheeling diode. The freewheeling diode supplies current during a period (“blocking period”) during which a saturable core inductor blocks current through the switching devices. As a result the converter operates in a quasi-synchronous mode. Thus, the quasi-synchronous rectification in accordance with the invention includes three phases: a first phase, during which current is blocked by a saturable core inductor in a reset condition, while current is maintained through a “freewheeling” (preferably Schottky) diode; a second phase during which the saturable core inductor is saturated and conducting current, along with the first switching device; and a third and fourth phase, complementary to the first and second phase.

#Quasi-synchronous operation allows for simplified inverter circuitry and reduced sensitivity to timing problems; furthermore, zero voltage switching of all primary and secondary switching devices is enabled under all load conditions.