Abstract: Method and apparatus for electrosurgery including tissue coagulation using very high voltage pulses of electrical energy applied to the electrosurgical probe. This minimizes heating of the surrounding tissue in the probe and is especially suitable for precise and limited coagulation and fulguration without excessive tissue charring or other damage. The power at rated load of the applied pulses to the probe is typically over 300W and the duration of the on time is very short, so each group of pulse bursts is of relatively low duty cycle. An RF generator is also provided for delivering electrical energy to an electrosurgical probe with the proper characteristics, including fast switching times.

Abstract: An apparatus for estimating a property of an earth formation penetrated by a borehole, the apparatus having: a carrier configured to be conveyed through the borehole; a transmitter disposed at the carrier and configured to transmit electromagnetic energy at a first frequency into the formation; a first antenna disposed at the carrier and configured to receive electromagnetic signals from the formation as a result of the transmitted electromagnetic energy interacting with the formation; and an active filter coupled to the antenna and configured to filter electromagnetic signals received by the antenna to let the electromagnetic signals at the first frequency pass for processing to estimate the property.

Abstract: An integrated exciter-igniter architecture is disclosed that integrates compact, direct-mounted exciter electronics with an aerospace designed igniter to reduce overall ignition system complexity. The integrated exciter-igniter unit hermetically seals exciter electronics within a stainless steel enclosure or housing. The stainless enclosure enables the exciter electronics to remain near atmospheric pressure while the unit is exposed to vacuum conditions. The exciter electronics include a DC-DC converter, timing circuitry, custom-designed PCBs, a custom-designed main power transformer, and a high voltage ignition coil. All of which are packaged together in the stainless steel enclosure. The integrated exciter-igniter unit allows for efficient energy delivery to the spark gap and eliminates the need for a high voltage cable to distribute the high voltage, high energy pulses.

Abstract: Resonant gate driver circuits provide for efficient switching of, for example, a MOSFET. However, often an operation of the resonant gate driver circuit does not allow for an application where high switching frequencies are required. According to the present invention, a pre-charging of the inductor of the resonant gate driver circuit is performed. This allows for a highly efficient and fast operation of the MOSFETs.

Abstract: An exemplary embodiment includes a system for measuring and controlling a thyristor comprising a thyristor, a Rowgoski coil in operable communication therewith the thyristor, and a processor operative to receive signals from the Rowgoski coil, determine a direct current value of the thyristor, and control the thyristor.

Abstract: A method and apparatus for generating low-jitter, high-voltage and high-current pulses for driving low impedance loads such as detonator fuses uses a MOSFET driver which, when triggered, discharges a high-voltage pre-charged capacitor into the primary of a toroidal current-multiplying transformer with multiple isolated secondary windings. The secondary outputs are suitable for driving an array of thyristors that discharge a precharged high-voltage capacitor and thus generating the required high-voltage and high-current pulse.

Abstract: Systems consistent with this invention comprise a trigger circuit for triggering a silicon device having a control terminal, where the silicon device is subject to variations in the intrinsic control requirements. The trigger circuit comprises a source of direct current (DC) supply voltage, and a DC-to-DC current mode Buck converter for converting the supply voltage into an output DC current not subject to undesired variations due to variations in the supply voltage, the Buck converter supplying to the control terminal a minimum current to turn on the silicon device despite the variations in the intrinsic control requirements. The silicon device may comprise a silicon controlled rectifier (SCR) with a gate terminal, an anode terminal, and a cathode terminal, and wherein the control terminal is the gate terminal, and wherein the variations in the intrinsic control requirements are variations in the intrinsic gate-to-cathode control current and voltage requirements.

Abstract: An inductive ignition circuit (10) especially adapted for use with micro-turbine and other small-sized turbine engines such as are used in electric generators. The inductive ignition circuit (10) includes a flyback transformer (14), a drive circuit (16) for energizing the primary (22) of the transformer (14), and a control circuit (18) that temporarily disables the drive circuit (16) once the transformer primary (22) has been sufficiently energized. The drive circuit includes a switching transistor (20) which is biased on to draw current through the primary (22). The control circuit (18) includes two feedback circuits (42,44), one of which initiates disabling of the transistor (20) to cause the transformer flyback and the second of which sets the spark rate. The first feedback circuit (42) monitors the primary current and disables the transistor (20) once the current exceeds a pre-selected level.

Abstract: A method for turning a GTO on and off and a corresponding driving circuit are specified. A turn-on current and a holding current are generated from voltage pulses which are converted into currents with the aid of an electric energy store. In terms of circuitry, it is particularly advantageous when the required voltage pulses are drawn from the same energy source, or the same energy store, as the pulse required to generate the turn-off current. The holding current is preferably generated by repeating voltage pulses. The repetition frequency of said voltage pulses can then be increased or reduced as required. The frequency is reduced, in particular, when the gate-cathode voltage becomes negative, and is increased again when the voltage is positive again.

Abstract: In a gate driver device, cathode conductor 2, gate conductor 3, and positive and negative conductors 8 and 9 between the principal turn-on and turn-off capacitors and MOSFET switching elements Q11-Q1i and Q21-Q2j are disposed on a wide plate. A thin insulation layer is inserted between conductor 3 and conductors 8 and 9. Numerous chip-type ceramic capacitors C11-C1m and C21-C2n to be used as principal capacitors are arranged in rows in the space between conductor 2 and conductors 8 and 9. The gate voltage of switching elements Q11-Q1i is reduced exponentially by time constant circuit TC, and the leak inductance of transformer Thf is employed to smooth the charging current.

Abstract: A highly efficient compact multiple output voltage generation circuit is designed for use in integrated circuit devices such as DRAMs which require multiple internal voltage supplies for optimum performance. An oscillator is connected to a primary coil of a microtransformer. The microtransformer secondary coil has multiple taps one of which is connected to ground. A second transformer tap is connected to a transformer output node. The oscillating transformer output signal is capacitively coupled to a voltage rectifier. The input to the rectifier is biased to one diode drop below Vcc. The output of the rectifier is an internal supply voltage greater than ground. Another transformer tap is connected to a negative oscillation output node. The negative oscillating signal is rectified to produce a negative internal supply voltage. The voltage generation circuit operates effectively at low Vcc input levels where capacitor based voltage pumps often fail. The circuit is compatible with CMOS manufacturing processes.

Abstract: A GTO gate driver circuit includes a GTO; a MOS gate driver; a turn-on rectifier for receiving power from a high voltage isolation transformer; a turn-on capacitor coupled in parallel with the turn-on rectifier; and a turn-on MOSFET having a drain coupled to a first side of the turn-on capacitor, a gate coupled to the MOS gate driver, and a source coupled to a gate of the GTO. In one embodiment the circuit includes a turn-off rectifier coupled to the turn-on rectifier; a turn-off capacitor coupled in parallel to the turn-off rectifier with a cathode of the GTO being coupled to a second side of the turn-on capacitor and a first side of the turn-off capacitor; and a turn-off MCT having a gate coupled to the MOS gate driver, an anode coupled to the source of the MOSFET and a cathode coupled to a second side of the turn-off capacitor.

Abstract: A current switch for borehole logging tools operating at high temperatures with high load currents, which includes a driver unit that responds to an input digital control signal by holding an output field effect transistor in a turn-off state until its gate electrode is fully charged before allowing the transistor to supply current to an inductive or acoustic load, and by effecting a rapid discharge of the gate electrode to turn the transistor off. A digital coupler is inserted between the source of the input digital control signal and the driver unit to electrically decouple the load current from the source. The effects of spurious noise contaminants including power spikes in the load, fly-back coupling, and Miller's capacitance thereby are minimized and a switching action with minimal transition time is achieved.

Abstract: A current source gate drive circuit for simultaneous firing of a set of series or parallel thyristors is described. The circuit includes two current loops, each of which serves as a current transformer primary. Electrically insulating tubes enclose the current loops. Current transformer cores, around which are wound a certain number of secondary turns, surround the current loops, thus magnetically coupling the primary current of the current transformer to the secondary turns. Thyristor gate driver circuits are electrically coupled to the current transformer cores. Each of the thyristor gate driver circuits receives and rectifies ac current signals from the current loops and forms a current pulse train firing signal. Each thyristor gate driver circuit has a corresponding thyristor that is fired by the current pulse train firing signal. The thyristors operate at a high voltage, but are electrically isolated from the current loops by the insulating tubes.

Abstract: A gate driver circuit includes a timing circuit, an anti-Miller surge protection circuit, and charging and discharging circuits for driving an output transistor, such as an IGBT. The anti-Miller surge protection circuit prevents the output transistor from being accidentally turned on. The gate driver circuit provides a high impedance input, so as to allow such a gate driver circuit to be driven by a relatively smaller isolation transformer. Further, the timing circuit in the gate driver circuit of the present invention allows such isolation transformer a relative lower frequency of operation. In one embodiment, the capacitance of the output transistor's gate terminal is used to determine the time constant of the timing circuit.

Abstract: An impedance-steerable circuit for an industrial phase controller inserts precise steerable trigger pulses in the sine and cosine excursions of a sine wave of high-energy capacitive and related discharge systems. Multiple pulses and Barkhausen effects are eliminated. The controller can lock capacitive discharge systems into precise phase or, in extended embodiments, serve as a power controller for radar systems, laser systems, and beam weapons. Thyristors and thyratrons provide steered elements (pulses) activated in a pulse-feedback mode.

Abstract: A power driver circuit for turning a semiconductor switching device on and off in response to receipt of a control signal includes a trigger circuit that turns on a latching switch at a speed that is independent of the rate of change of the control signal. The trigger circuit is responsive to the control signal to apply a current from the semiconductor switching device to the latching switch. A high speed SCR may be used as the latching switch and may be triggered by a small trigger current from the gate of the semiconductor switching device fed to both the anode and cathode gates of the SCR. High speed diodes may also be used to increase the speed of the circuit. The power driver circuit improves the efficiency of the semiconductor switching device by decreasing the time the switching device spends in transition its two steady states.

Abstract: In a circuit for hard driving a GTO, the conductor inductance (L1) and the internal inductance of the GTO (L2) form, together with a first capacitor (C1) situated in parallel via a switch (S), a series resonance circuit inside the gate circuit. In this connection, the chosen sizes of the first capacitor (C1) and of the first inductance (L1) are such that, if the first capacitor (C1) discharges via the two inductances (L1, L2), the gate current originating from the first capacitor (C1) exceeds half the value of a GTO anode current to be turned off within less than 5 .mu.s in the first quarter cycle of the series oscillatory circuit. Moreover, first means are provided which uncouple the first capacitor (C1) from the generation of the gate current after the first quarter cycle of the resonance circuit and allows the gate current to decay slowly in such a way that, at any time, it is greater than the tail current of the GTO.

Abstract: A gate power supply circuit including a switching device and a gate drive circuit connected to the switching device for generating a gate signal to be supplied to a gate of the switching device. The gate power supply circuit further includes a series circuit of a snubber capacitor and a snubber diode connected in parallel with the switching device, and an inductor, a first terminal of which is connected to a connection point of the switching device and the snubber diode. The gate power supply circuit also includes a series circuit of power disposing circuit and a first diode, connected between a series connection point of the snubber capacitor and the snubber diode and a second terminal of the inductor. The gate power supply circuit further includes a series circuit of a power supplying capacitor and a second diode, connected in parallel with the inductor.

Abstract: A sense amplifier for implementing a wide or multiple input NOR gate for receiving a product term of a group of array cells in a programmable logic device (PLD). Array cells signals which are all normally received by the sense amplifier in a single product term input are instead connected to the sense amplifier in smaller groups of sub-product terms. Each smaller group of sub-product terms is then connected through a transistor cascode amplifier in the sense amplifier to form the single product term enabling a reduction of capacitance and an increase of output speed of the sense amplifier.