Abstract: Inverter-switch currents are sensed using a conventional a-c current transformer whose primary winding is connected to the inverter-switch and whose secondary winding is connected to a signal-developing resistor. An a-c switch is driven by the inverter-switch timing signals and disconnects the output of the transformer when the inverter-switch is in an off state. Alternatively, a Rogowski coil senses the inverter-switch currents and delivers an output voltage that is proportional to the di/dt of the inverter-switch. An integrator is coupled to the output of the Rogowski coil and delivers a signal that represents the inverter-switch current. A reset circuit, responsive to the inverter-switch control signal, resets and holds the output of the integrator to zero during the off-time of the inverter-switch.

Abstract: A surface mount package is provided with a U-shaped heatsink which is coupled to exposed portions of a bottom plate of the package. The bottom plate of the surface mount package is provided with border strips which extend beyond the edge of an encapsulated portion of the package such that the heatsink may be coupled thereto.

Abstract: A high power DC blocking device is provided which blocks DC current, passes AC current, and limits the voltage across it under fault conditions. A DC blocking capacitor is used to block the flow of DC current, while allowing the passage of normal AC currents. A main bypass path includes switching devices which provide a low impedance path across the capacitor under fault conditions. Auxiliary switching devices are used to connect a storage capacitor across the device at the initiation of a fault, thereby charging the storage capacitor to a stored voltage level before the main switching devices are fired. After the fault passes, the auxiliary switching devices are fired once again to apply the stored voltage in the storage capacitor to the main switching devices to commutate them off. The storage capacitor and auxiliary switching devices also form part of a voltage clamp circuit which dissipates inductive energy stored in a system to which the DC blocking device is connected.

Abstract: An electrical isolation device is connected at input terminals in lines between a structure to be cathodically protected and a ground, or between two cathodically protected structures, to block selected low levels of DC voltage while freely conducting normal AC currents and all fault currents. The device has two diode stacks, formed of layers, and the stacks are connected in parallel with one another in opposite polarity and in parallel with a capacitor across the input terminals of the device. Each diode layer include a junction wafer and a conducting metal disk. The layers in each stack are preferably pressed tightly together and to metal bus conductors by a clamp to maximize the contact of the diode layers to each other and to the conductors to minimize contact resistance. AC currents are conducted (e.g., to ground) through the capacitor while low level DC voltages are blocked by the cumulative threshold voltages of the plural diode layers connected in series in each of the stacks.

Abstract: A resonant power supply for use in conjunction with power transistor switching circuits. In one embodiment, a series-connected LC resonant circuit is coupled to the high voltage pulsed output of the power transistors and designed to draw power from the pulsed output and deliver the same to a low voltage output capacitor at which a low voltage output is provided. The low voltage output is regulated by a zener diode connected in parallel with the output capacitor. A starting resistor of a relatively high value, typically in the Megohm range, supplies initial charge to the output capacitor to permit the first switching event to occur so that the resonant power supply can begin to provide power. The resonant frequency of the LC circuit is significantly higher than the maximum switching frequency of the power transistors, enabling the resonating high frequency wave forms of the LC circuit to supply repeated charge bursts to the output capacitor.

Abstract: An isolator surge protector for use with corrosion protection systems which are an inherent part of or coupled to an electrical power system, for power transformers, and for DC transmission systems, where it is necessary to present a high impedance to DC and a low impedance to AC up to a predetermined voltage level. Anti-paralleled thyristors in the isolator surge protector turn on during power surges. A bypass circuit insures turn off of the thyristors after a triggering event such as lightning or a 60 Hz surge has ended. The bypass circuit shunts DC bias currents, such as that which may be provided by a DC bias voltage source for cathodic protection, from the thyristors to ensure that the voltage across each thyristor falls below its holding voltage or current, and thus prevents the thyristor from being stuck in a continuous conduction mode. Power to operate the bypass circuit may be tapped from the surge which caused the thyristor to trigger so that the bypass circuit operates autonomously.

Abstract: A four-terminal, unity power factor, electronic rectifier module. The electronic rectifier module is self-contained and includes therein bridge diodes which form a full wave bridge rectifier, a control circuit, and a diode which components act together to draw a sinusoidal current from the line. The self-contained, four-terminal module is designed to permit a high-frequency input capacitor and a line inductor to be connected to its input terminals and a smoothing capacitor to its output terminal. The module avoids the need to provide a separate pair of power terminals for the standard filtering components, resulting in a more economical package and in an easier-to-use module.

Abstract: A universal battery charger circuit has polarized capacitors disposed in the input a-c lines to a bridge-connected rectifier. A voltage clamping circuit is connected to the d-c terminals of the bridge and diodes are connected in parallel with each of the polarized capacitors to define a circuit for the flow of charging current. Regulation circuits are provided for both battery voltage and charging current so that any battery of given voltage output can be charged from different input voltage sources.

Abstract: Two or more buck converter circuits are cascaded in such a manner that the output of one serves as the input to the next, with the input voltage to each succeeding buck converter stage being reduced in magnitude. The total circuit losses are substantially reduced as compared to the losses generated in a single buck converter having the same input voltage range and the same output voltage and output current. Both positive and negative output terminals may be provided for an output stage.

Abstract: A power module contains IGBT die along with integrated circuit driver chips and opto isolators or isolation transformers within the same module housing. Output terminals are provided which can be interfaced directly to control logic or microprocessors for operating the module. The IGBTs may have current-sensing electrodes to simplify current measurement and control functions.

Abstract: An energizing circuit for printer hammer drive coils is provided in which a single MOSFET transistor and a single diode is employed for each drive coil. Two voltage source means, one of which may be a capacitor, are connected in series. The drive coil is connected in series with the single MOSFET transistor and one of the voltage sources and is energized when the transistor is on. The drive coil discharges in a series circuit including the diode and the other of the voltage sources and charges the later voltage source when the transistor is off. An energy recuperation circuit is disclosed for receiving energy from the later voltage source and returning it to the first voltage source.

Abstract: A switching power supply is disclosed using a single transistor circuit which provides a constant output voltage for a range of input voltages extending from a nominal 115 volt power supply to a nominal 220/240 volt power supply without requiring a change in the circuit configuration throughout the range of input voltages. The circuit is disclosed in connection with a single transistor forward converter circuit, in which the transformer winding of the converter circuit is provided with a uni-directional clamp to prevent the transformer voltage of a given polarity from exceeding the clamping voltage magnitude. By clamping one polarity of the transformer voltage which is in series with the switching transistor, the maximum peak-to-peak voltage on the transistor is reduced from that which would be produced in the absence of clamping and enables the use of a power MOSFET transistor for the circuit.

Abstract: A naturally-commutated, voltage-fed direct-current (DC) to alternating-current (AC) power converter employing thyristor elements couples a DC power system with an AC power system without the requirement to force commutation. To effect natural commutation, the fundamental component of current flowing between the DC system and the AC system must lead the DC system switching voltage.

Abstract: A naturally commutated cycloconverter having at the input a source of higher frequency than at its output is used as a static reactive power generator to correct displacement angle in an alternating current power system when coupled thereto at the output. Reactive power correction is obtained with such "high frequency link" by automatically controlling the output voltage of the cycloconverter so as to deviate by a required amount from the AC power system voltage. At the same time, a circulating current is established between the positive and negative banks of thyristors of the cycloconverter of such a magnitude as to compensate for the variations of the lagging quadrature component of the input current of the cycloconverter caused by output current variations, thereby permitting optimization of the high frequency link.