A voltage regulator for converting an unregulated input voltage into a regulated D.C. voltage. The voltage regulator includes a driver transformer which periodically receives energizing current from a voltage source through a transistor switch. A switching regulator controller regulates the conduction time of the transistor so as to control the amount of energizing current supplied to the driver transformer. The driver transformer secondary windings drive the base of output transistors which, when conducting, connect the primary windings of an output transformer to the voltage supply. A capacitor is connected in parallel with the primary winding of the driver transformer so as to short circuit the primary winding of the drive transformer when the driver transistor is turned off. The current flow in the secondary of the driver transistor causes removal of the stored base charge from the output transistors which decreases the turn off time of the output transistors. The primary windings of the output transformer are connected in series with first and second capacitors connected between the common junction of the primary windings and the voltage supply to effectively create a virtual ground at the common junction. One end of each of the secondary windings of the output transformer is connected to Schottky diodes arranged in a full-wave, center tapped rectifier configuration. A hollow ferrite sleeve is disposed around a conductor connecting each Schottky diode with a secondary winding and provides sufficient inductance to protect the Schottky diodes from transient reverse overvoltages.
The inverter includes a DC to AC converter circuit including a plurality of transistors which are switched on and off to convert a DC signal into an AC signal. The converter circuit also includes diodes which are alternately forward and reverse biased during the operation of the converter circuit, the diode having a reverse recovery period whenever the diode is switched from a forward to a reverse biased condition during which the reverse resistance of the diode is substantially zero. An inductor is connected to the diode for limiting the current through the diode during the reverse recovery period such that shoot through currents which pass through both the diode and the inductor are limited to desired levels.
A switched mode regulated DC to DC converter for supplying a regulated voltage to a load includes a switching frequency generator of a switching cycle having positive and negative portions. A device, responsive to the outputs of the switching frequency generator, accumulates a voltage during the positive and negative portions of the switching cycle. The demand for voltage by a load is sensed and circuitry generates a first and second trigger otuput during the respective positive and negative portion of the switching cycle when the accumulated voltage equals the sensed load voltage demand, the time required to generate the second trigger output being equal to the time required to generate the first trigger output. A transformer apparatus, responsive to the first and second generated trigger outputs, generates currents of positive and negative polarity during the positive and negative portions of the switching cycle. A first electronic switch, responsive to the generated currents of positive polarity, connects a load voltage source to a load during the positive portion of the switching cycle. Similarly, a second electronic switch, responsive to the generated currents of positive polarity, connects the load voltage source to the load during the negative portion of the switching cycle.
A printed circuit board having a selectable circuit routing configuration comprises a substrate, a plurality of electrical traces mounted to the substrate for interconnecting electrical components, and at least one fusible connector mounted to the substrate. Each of the fusible connectors has a fuse line formed from a conductive layer of the printed circuit board and forms a fusible connection between at least two of the electrical traces. The circuit routing configuration can be selected by application of a predetermined current through at least one of the fusible connectors to break the fusible connection formed by the fusible connector.
An inductive device composed of a bead of magnetic material, such as ferrite, has an aperture through which an electrical conductor is adapted to pass. The bead is formed unsymmetrically about at least one axis. The asymmetry of the bead alters the magnetic characteristic of the bead so as to increase its ability to absorb volt-seconds on the conductor and thereby prevent destructively high currents. The inductive device is advantageously used in the d.c. supply to the power transistors of an inverter to protect the transistors from current surges due to the simultaneous conduction of the transistors.
A high speed shunt regulator comprises a DC current source, a DC voltage reference/current shunt circuit, and first and second Schottky diodes connected in series with each other between the DC current source and the DC voltage reference/current shunt circuit. An output port for the load is connected between the first and second Schottky diodes. The Schottky diodes have little parasitic capacitance and virtually no reverse recovery. Consequently, the amount of current passing through the Schottky diodes can change in one nanosecond and the shunt regulator can accommodate high frequency fluctuations in the load while maintaining rated voltage. In other words, the Schottky diodes serve the function of "isolating" the slower semiconductors of the DC current source and reference voltage/current shunt circuit from the load.
