Abstract: An electrical power inverter with a controllable output voltage waveform is disclosed. In a preferred embodiment, the electrical power inverter has a trapezoidal output voltage waveform with rising and falling edges that are controlled such that their slopes are kept below a selected value.

Abstract: A transient voltage protection circuit includes a normally closed switch connected between a rectifier circuit and a DC to DC converter. This switch is caused to switch to a current limit state when the voltage input to the DC to DC converter exceeds a first predetermined value, thereby protecting the DC to DC converter from voltages that exceed the converter's operational limits. The switch is returned to its normally closed state when the voltage input to the converter drops below a second predetermined lower value. A capacitor connected across the input terminals of the converter is charged up when the switch is closed and functions to supply power to the DC to DC converter when the switch is in its current limit state.

Abstract: An electrical power converter system having a power factor correction circuit and a switching power converter. The power factor correction circuit converts the AC line voltage into an unregulated DC voltage referred to as the PFC voltage, which supplies an unregulated DC input voltage to the switching power converter. The switching power converter converts the unregulated DC input voltage into one or more regulated DC output voltages. The PFC voltage automatically adjusts to an appropriate value for achieving the desired power factor correction, converter efficiency, and converter temperature. In a preferred embodiment, the value of the PFC voltage is adjustable in response to a control signal produced by a PFC control circuit. The PFC control circuit measures the peak value of the input line current to determine whether the power factor is acceptable. If the power factor is acceptable, the PFC voltage will be maintained at a relatively low value.

Abstract: Size reduction in a clamped power converter can be achieved, and stability of the converter under no-load and transient loads can be substantially improved, by operating the converter in a continuous flyback mode.

Abstract: A detection circuit for use in an electrical power converter having at least one negative output rail, for detecting the voltage of the negative output rail and for converting the voltage to a positive output voltage. The detection circuit includes an input port for receiving the negative output rail voltage from an electrical power converter, an output port, a ground reference potential, a node having a voltage that is positive with respect to the ground reference potential, and a circuit for generating a measurement current from the node to the ground reference potential. The value of this measurement current is a function of the negative output rail voltage received at the input port. A circuit is further provided for generating an output voltage at the output port that is positive with respect to said ground reference potential and whose value is a function of said measurement current.

Abstract: A power factor corrected rectifying circuit is disclosed. The invention may be implemented using only passive elements and, in such an embodiment, achieves a power factor of about 80%. The invention comprises two rectifying circuits for providing two rectified current paths from an AC input port to an output port. The coupling of current along one of the rectified current paths is delayed. As the sum of the delayed and undelayed currents, the input current pulse is widened to approximate a sinusoid, thereby increasing the power factor.

Abstract: An improved electrical power converter is disclosed. The electrical power converter utilizes a pulse width modulator responsive to the voltage across a tertiary winding of the power transformer. The electrical power converter includes a feedback control circuit for providing a regulating voltage to the pulse width modulator that is substantially proportional to the voltage across the tertiary winding with the voltage spikes caused by any leakage inductance in said power transformer removed. The feedback control circuit includes a spike compensator circuit that utilizes leakage inductance produced voltage spikes to compensate for output voltage degradation due to heavy loads.

Abstract: An improved electrical power converter is disclosed. The electrical power converter utilizes a step-gapped power transformer having a ferromagnetic core, a primary winding, and one or more secondary windings. The ferromagnetic core is step-gapped such that it has a continuous portion and a gapped portion. A power switch, preferably a MOSFET, alternately couples an input voltage across the primary winding of the transformer, inducing voltage pulses across the secondary windings that are filtered to produce one or more output voltages. The gate terminal of the MOSFET is preferably driven by the voltage induced across a tertiary winding of the transformer.

Abstract: An improved temperature control system for a power conversion circuit having two or more power converters operating in parallel and providing output power to a single load. The temperature control system maintains the temperature of each of these power converters at approximately the average temperature of the power converters. A detector coupled to each power converter detects the temperature of the power converter and generates a measurement signal that is a function thereof. A reference signal is generated that is a function of each measurement signal. A control circuit responsive to the measurement signal of each power converter adjusts the output power of that respective converter as a function of the difference between that converter's measurement signal and the reference signal such that the temperature of each power converter approximates the average of temperature of the power converters.

Abstract: The present invention provides a heat sink and electromagnetic interference shield assembly for a plurality of semiconductor elements. The semiconductor elements are connected with other circuit elements to form an electrical circuit. Each semiconductor element has a metal portion for dissipating heat generated by the semiconductor element. The metal portion also emits electrical energy as a result of the operation of the semiconductor element thereby causing unwanted electromagnetic interference. The assembly comprises an insulator attached to the meted portion of the semiconductor element and a substrate for mounting the plurality of semiconductor elements. The insulator is of a thermally conductive material to facilitate the conduction of thermal energy away from the semiconductor element. The substrate has a metal base layer, a middle insulating layer, and a plurality of metal mounting areas for mounting the plurality of semiconductor elements.

Abstract: An improved gate drive circuit for use with a switching power device in a power converter and other power-transfer type circuits and the like is described. The gate drive circuit according to the present invention requires fewer components and space that convention prior art gate drive circuits. The drive circuit provides isolation between the control circuitry and the device without storing a significant amount of long-term (i.e., D.C.) energy and is also more energy efficient than many prior art gate drive circuits. Additionally, the present invention comprises means for cleanly terminating the drive signal to the switching power device when the control circuitry terminates operation. This prevents an incorrect signal to the switching power device, which may conduct at an inappropriate time, causing damage to the power converter or power-transfer circuit. Many prior art drive circuits have D.C.

Abstract: A flyback-type power converter having a secondary-side resonant circuit which shapes the current waveform in the secondary winding and secondary circuit to reduce the RMS current values therein is described. The shaping reduces conduction losses and improves conversion efficiency. With the resonant circuit, the energy stored in the transformer is transferred during the OFF-period in substantially a fixed time duration, enabling a fixed-OFF period operation mode. The converter may further have a primary-side resonant circuit for capturing and recycling the energy stored the leakage inductance of the primary winding, which is normally wasted in snubber circuitry.

Abstract: A multicell battery power system for providing power to a load is disclosed. The battery power system includes a plurality of battery modules and power bus for transmitting power between the battery modules and the primary load. Each of the battery modules includes a battery for providing electrical power and connection circuitry for connecting the battery to the power bus. The battery modules each include circuitry for monitoring the power output and status of the battery means. Each battery module also includes a programmable battery controller for controlling the operation of the battery and the connection circuitry. The battery controller is programmably responsive to the power monitoring circuitry, and in an illustrated embodiment is also be responsive to a system power controller or to one or more other battery modules. A battery charger may also be included in each module to provide programmably controlled individual recharging of batteries by module.

Abstract: An electrical power inverter having an output voltage waveform that closely corresponds to a reference waveform under a wide range of load conditions is disclosed. The present invention allows for excess energy present at the output port of the electrical power inverter to be coupled back to the input port to maintain the correspondence of the output voltage waveform with the reference waveform when the inverter is providing power to inductive or light resistive loads.

Abstract: A boost-type power factor correction circuit is disclosed in which output voltage of the convertor is proportional to the peak input voltage. To achieve this, the circuit includes a peak rectifier D2, C2 which senses peak input voltage and provides a reference to which the output voltage derived through resistors R3, R4 is compared to give an error signal dependent upon variation from the peak input voltage derived reference. The error signal is used to control a MOSFET switch 120 to provide an output voltage V.sub.out dependent upon the reference.

Abstract: A circuit for utilizing the magnetizing current in the transformer of a power converter to reset the transformer's core and to provide a zero voltage switching condition on the converter's primary switch is disclosed. The transformer includes a primary winding and a secondary winding, the secondary winding being coupled to an output load and a primary switch connected in series between the primary winding and a voltage source. The closing of the primary switch causes energy to be stored in the transformer and the opening of the primary switch causes the energy to be released from the transformer. A transformer flux reversal circuit is used to reverse the direction of the magnetic flux built up in the transformer when the primary switch is opened. A secondary switch is coupled in series with the secondary winding of the transformer and is operated to prevent any loading effects of the load from disrupting the creation of the zero voltage switching condition.

Abstract: A circuit for the fast turn off of a field effect transistor (FET) for use in circuits such as a power converter circuit. The FET turn off circuitry includes a gate current sink transistor and a capacitor linked between the base of the gate current sink transistor and the drain of the FET. This capacitor increases the current into the base of the gate current sink transistor, and enables an increased magnitude of current to flow from the FET, thereby increasing the speed with which the FET turns off. A diode is preferably also connected between the base and the emitter of the gate current sink transistor to provide a return path to discharge the capacitor.

Abstract: A dual active clamp (DAC) converter comprising two active-clamp, zero-voltage switching (ZVS) converters for converting electrical power from an input source to an output load is described. The two active-clamp ZVS converters are coupled in parallel to one another at their respective inputs and outputs, and are operated in a manner which reduces the overall input and output ripple currents of the DAC converter, which reduces the EMI emissions of the DAC converter. Each of the active-clamp ZVS converters achieves zero-voltage switching on its primary switch means, which also improves EMI emissions. Each active-clamp ZVS converter includes a transformer having a primary winding and a secondary winding, the secondary winding being coupled to the output load and the primary switch means being coupled between the primary winding and a voltage source, and an active clamp circuit comprising a series combination of a storage capacitor and a first switch means.

Abstract: A battery charging circuit comprising means to supply a DC output from the mains supply for inter alia recharging a rechargeable battery, switch means in series with the battery across the DC output which are normally closed but which open from time to time to disconnect the battery from the DC output, battery voltage monitoring means for measuring the potential or emf of the battery at the time when the switch means are open, and means for determining a maximum potential and therefore fully charged state for the battery and decreasing the charging current from the DC output to the battery when a fully charged state is determined.

Abstract: A efficient circuit for driving two switching transistors of an electrical power transfer circuit in an anti-phase relationship is described. The drive circuit is applied to a power transfer circuit, such as a switching-type power converter, having a first switching transistor, a second switching transistor, and a magnetic storage element electrically coupled to the first switching transistor. The first switching transistor is coupled to the magnetic storage element and operates to vary the magnetic flux in the storage element. The present invention comprises a drive circuitry for operating the first switching transistor, the drive circuitry being responsive to a first control signal generated by the power transfer circuit. For driving the second switching transistor, the present invention comprises circuitry for generating a second control signal as a function of the magnetic flux in the magnetic storage element.