Abstract: An improved dual voltage automotive electrical system in which low voltage loads are powered by a series resonant DC-DC converter operated at a fixed switching frequency below the resonant frequency of its tank circuit. With this arrangement, the converter provides a fixed conversion ratio from the regulated upper system voltage, and operates with the beneficial attributes of zero current switching and inherent overload protection. In a first embodiment, a transformer inductively couples the converter tank circuit to the low voltage loads, providing full input/output galvanic isolation. In a second embodiment, the converter is configured so that a portion of the power supplied to the low voltage loads is directly coupled from the upper system voltage source, with the remaining portion being coupled through the converter.

Abstract: A transformer assembly in which an isolation transformer and two additional inductor elements of a series/parallel resonant converter are physically integrated in a cost and space-efficient design. The transformer and two inductors are integrated through the simultaneous control of the leakage inductance and the magnetizing inductance of the assembly. The primary and secondary windings of the transformer are wound in a prescribed manner on a closed-path ferromagnetic core, the magnetizing inductance of the unit being determined by the desired inductance of second inductor, and the leakage inductance of the unit being determined by the inductance of the first inductor, which predominates the total series inductance of the tank circuit. The desired magnetizing inductance is achieved by controlling an air gap disposed in the magnetic flux path of the core, while the desired leakage inductance is achieved by winding a certain portion of the secondary turns on a loosely coupled leg of the core.

Abstract: An improved sub-resonant converter which retains the advantages generally associated with simple series resonant converters while additionally providing improved form factor and efficiency, and reducing EMI. The overall tank circuit includes at least a first inductor and first capacitor connected in series, a second capacitor connected in parallel with the load circuit, and a second inductor connected in parallel with the second capacitor for providing voltage boost capability. In addition to reducing dv/dt in the load circuit, the second capacitor draws a current that has the effect of reducing the form factor of the supplied current while shortening the negative portion of its cycle so that reverse current through the anti-parallel diode of one switching device is terminated, or nearly so, by the turn on of the next switching device, thereby reducing EMI associated with a rapid initial rise in current at such turn on.

Abstract: An LC resonant circuit. The resonant circuit includes a resonant capacitor and a transformer. The transformer comprises a magnetic core having a primary winding, secondary winding and control winding wound on the core. The primary winding is loosely coupled with the secondary winding. The resonant capacitor of the circuit is connected in series with the primary winding of the transformer. The control winding saturates the core in response to the application of direct current thereto to control the output of the resonant circuit.

Abstract: A push-pull or forward switching power supply is operable over a voltage range of 4.5 to 40 volts at high efficiency. At low voltages a primary winding or pair of windings are activated by a PWM control to regulate the output current. At high voltages, an additional primary winding in series with each of the other winding or windings is also activated by a PWM control.

Abstract: An LC resonant circuit for a resonant converter includes a resonant capacitor and an inductor coupled to a fixed frequency AC supply. A controlled inductor in parallel with the resonant capacitor is controlled by a DC current to vary its inductance. The controlled inductor comprises a magnetic core having one or more power windings, and a control winding wound on the core. The DC current in the control winding produces core flux which effects core permeability. The controlled inductor has the effect of changing the capacitor impedance and thus influences the converter output. Multiple, independently controlled and regulated outputs may be driven by one power switching stage.

Abstract: A multi-phase AC to DC harmonic neutralizing power converter. The power converter includes a plurality of non-isolated inputs for respective phases of a multi-phase source of AC power and a plurality of first rectifiers connected respectively to the inputs. A multi-phase harmonic neutralizing converter includes a power switching inverter having an input connected to the outputs of each of the first rectifiers, the inverter including LC resonant circuits. A plurality of second rectifiers having respective inputs connected to the output of the inverter through a plurality of respective transformers having outputs that are connected in voltage additive relationship to the outputs of the respective individual phase first rectifiers.