Abstract: A synchronous rectifier is able to operate at higher frequencies and provides an output having lower noise than prior art FET synchronous rectifier system by using field effect switching devices which contain only one conductivity type of semiconductor material and connecting a high speed, low charge storage diode in parallel. Schottky diodes are preferred whereby there is no junction diode in the structure. Conventional FETs may be used when paralleled with a Schottky diode which prevents the FET's parasitic internal diode from becoming conductive.

Abstract: A power semiconductor device incorporates in its active, or current-carrying, region a main current section and an emulation current section. The active region is surrounded by a common device termination region. This is accomplished through provision of respective separate cathodes for the main and emulation current regions, while the device anode is common to both the main and emulation current sections. The current level in the emulation current section provides an accurate representation of the current level in the main current section since the main and emulation current sections are closely coupled both thermally and electrically and, further, are formed in the same fabrication process. The current level in the main current section can be economically determined with low power circuitry by way of sensing the current level in the emulation current section.

Abstract: A parallel resonant induction cooking surface unit comprises a voltage fed inverter which drives a load circuit, comprised of a main induction drive coil, a tuning capacitor coupled in parallel with the main induction drive coil, and an inductor coupled in series with the main induction drive coil, with a square wave voltage, causing the main induction drive coil to generate a time variant magnetic field resulting in eddy currents being induced in the surface of a metallic, food-containing utensil positioned adjacent to the main induction drive coil, and hence, utensil heating. By tuning the load circuit to resonance at or near the square wave frequency, reactive currents therein are minimized, resulting in improved power factor. Moreover, resultant main induction drive coil voltage and current are nearly sinusoidal, thereby achieving reduced electromagnetic interference radiation at frequencies greater than the square wave frequency.

Abstract: A variable frequency AC power source drives a gas discharge lamp which is connected in parallel with the capacitance of a series resonant circuit. The polarity of the voltage applied to the resonant circuit is commutated at such times as the rate-of-change of current flow in the resonant circuit is below an adjustable threshold value. The setting of a threshold adjusting circuit determines the brightness of the lamp. The polarity is also commutated at such times as the current flow from the source reaches a predetermined level. Lamp current is thus independently and variably controlled in the variable power mode.

Abstract: The secondary winding of a current transformer is driven by a high frequency AC source to excite the core to alternating, uniformly equal positive and negative peaks of current excitation. An inductance sensor alternately senses the secondary winding inductances at corresponding points adjacent the positive and negative peaks of the flux wave generated in the core. Any difference in these inductances is a function of low frequency primary current and is utilized to develop a current flowing through a tertiary core winding to equalize these inductances. This tertiary winding current thus becomes a precise measure of the primary current.

Abstract: A high frequency inverter power supply includes a high power inverter section powered by substantially unfiltered rectified a.c., and a control section including rectifier and filter means for providing substantially pure d.c. to maintain continuous instantaneous control over the high power inverter section. High frequency transformer means and optional output rectifiers and filters provide for a.c. or d.c. output.

Abstract: An AC electrical output is produced in the secondary windings of a transformer by alternately switching DC current in a primary winding with active element switches whose alternate switching action is controlled by the stored energy variations in a tertiary winding included with the output transformer and by a high efficiency switching control circuit which facilitates the switching transition of the active elements. This control is achieved in part, by providing a current sensitive latch which is triggered to its conductive state when a predetermined level of primary winding current is detected to thereby initiate a switching transition. This latch circuit is connected to conduct stored electrical charge with respect to the active element switch during the switching transition thus facilitating and promoting the efficiency of the switching operation.

Abstract: No-load losses normally associated with transformer-isolated inverter circuits employing high frequency switching devices are substantially eliminated by electrically short-circuiting the load terminals of the inverter to quickly and efficiently shut down inverter operation and thereby reduce the no-load losses to at least the fall-back current losses of the inverter.

Abstract: A signal pickup means is provided in a power supply having an inverter driven transformer therewithin for producing a cancellation signal substantially equal in magnitude and opposite in phase with respect to an unwanted common mode interference signal which otherwise appears on the electrical output from the secondary windings of the transformer with respect to an electrically isolated electromagnetic shield about the exterior of the power supply. This signal pickup is connected to the secondary winding and to an electrostatic shield about the secondary winding so as to effectively add the cancellation signal to the interference signal thereby substantially eliminating and reducing the unwanted common mode emanations from the output of the power supply. Preferably, the signal pickup is connected to substantially reduce unwanted common mode potentials between the center tap of the secondary windings and other shielding of the power supply in spite of electrical isolation therebetween.

Abstract: An AC electrical output is produced in the secondary windings of a transformer by alternately switching DC current in a primary winding with active element switches whose alternate switching action is controlled by the stored energy variations in a tertiary winding included with the output transformer and by a high efficiency switching control circuit which facilitates the switching transition of the active elements. This control is achieved in part, by providing a current sensitive latch which is triggered to its conductive state when a predetermined level of primary winding current is detected to thereby initiate a switching transition. This latch circuit is connected to conduct stored electrical charge with respect to the active element switch during the switching transition thus facilitating and promoting the efficiency of the switching operation.

Abstract: An electrical inverter circuit for converting d.c. electrical input into an a.c. electrical output involving the control of active switch elements in the primary of an output transformer circuit by, in part, providing a further controllable active element in circuit with the active element switches such that the primary winding current also flows therethrough. Synchronous control means are provided for synchronously controlling this further active element so as to increase its electrical impedance during at least a portion of each switching transition of the active element switch means so as to further aid and promote the rapid and efficient transitioning of the active element switches. Various alternative circuits are shown for this and for detecting the switch point as a function of primary transformer winding current and for further controlling the transition of the active switches in combination with the increased electrical impedance of the further controllable active element in circuit therewith.

Abstract: An electrical inverter circuit for converting d.c. electrical input into an a.c. electrical output involving the control of active switch elements in the primary of an output transformer circuit by, in part, providing a further controllable active element in circuit with the active element switches such that the primary winding current also flows therethrough. Synchronous control means are provided for synchronously controlling this further active element so as to increase its electrical impedance during at least a portion of each switching transition of the active element switch means so as to further aid and promote the rapid and efficient transitioning of the active element switches. Various alternative circuits are shown for this and for detecting the switch point as a function of primary transformer winding current and for further controlling the transition of the active switches in combination with the increased electrical impedance of the further controllable active element in circuit therewith.