Abstract: The base electrode of the switching transistor in a converter is resistively connected to the output terminal of a pulse width modulator and connected through first and second series connected diodes to a ground reference potential which is also connected to the emitter of the transistor, the junction between the diodes being electrically connected through a large capacitor to the modulator output terminal. Voltage pulses at the output terminal cause the transistor to pass collector current and the second diode to conduct for charging the capacitor. On termination of voltage pulses, the modulator connects the output terminal thereof to ground. This causes the charge voltage on the capacitor to turn the first diode on to pull the base voltage sharply negative for rapidly drawing minority carriers out of the base region.

Abstract: A power supply in carrier subscriber terminal equipment includes a switched DC-to-DC converter that is powered by a DC line voltage and driven by a pulse width modulator for producing a first DC voltage on a bus line that powers the modulator and an oscillator which keys the modulator. Circuitry for starting the converter, modulator, and oscillator includes a first transistor and Zener diode that are resistively connected in series across the line voltage for producing a second DC voltage on the Zener, which is less than the first voltage. A second transistor is turned on by the second DC voltage for coupling it to the bus line to initially energize the oscillator and modulator, which then drives the converter to cause it to produce the first voltage on the bus line. A second output of the oscillator is also coupled through a voltage doubler to the first transistor for turning it and the Zener off.

Abstract: A switched DC-to-DC converter in a power supply is powered by input line current from an external power source and driven by voltage pulses from a variable duty cycle pulse width modulator for converting a DC input voltage to a DC supply voltage of a different value that is applied to a load impedance. A comparator monitors the supply voltage for producing an error voltage that biases the modulator for adjusting the width of the voltage pulses, and thus the duty cycle of the converter, for maintaining the supply voltage relatively constant. An RC circuit integrates the voltage pulses for producing an indication of the average value thereof, which is directly related to the value of line current drawn by the converter. When the average value of voltage pulses exceeds a reference voltage, the value of bias voltage is limited for establishing the maximum width of voltage pulses and duty cycle of the converter, and thereby limit the maximum line current drawn by the power supply.

Abstract: In this converter, a common transistor Q2 is one of the two transistors Q1 and Q2 of a multivibrator and is also one of a pair of power switching transistors Q2 and Q3 that are connected in series across an input port receiving an input voltage-V of one polarity. The other transistor Q1 of the multivibrator is also connected across the input port. The multivibrator causes the switching transistors Q2 and Q3 to be alternately conducting and nonconducting. A pair of capacitors C3 and C4 and unidirectional diodes D4, D5, and D6 are connected to the switching transistors Q2 and Q3 in such a manner that only one capacitor C3 is charged in one direction during conduction of the common transistor Q2, and that this one capacitor C3 discharges through the other capacitor C4 to charge the latter and produce an output voltage of the other polarity across it and an output port only during conduction of the other switching transistor Q3.

Abstract: In a system employing half-span preemphasis of transmitted signals on a cable pair telephone line, equalization is accomplished in a circuit arrangement including first and second complementary constant-resistance networks having the input impedances thereof in the emitter and collector circuits, respectively, of a common emitter amplifier. These impedances control the feedback and gain of the amplifier such that their effects are additive in a particular manner in the collector-output circuit thereof. The terminating resistances of the networks are the resistances produced by a pair of differentially controlled thermistors. A DC error signal that is proportional to line length controls the current driving the thermistors and thus the resistances thereof. When the circuit arrangement is at half-span spacing, a difference circuit causes the terminating resistances of the thermistors to be the same values, which make the impedance characteristics of the networks such that the net gain of the amplifier is flat.

Abstract: A direct current power supply is capable of delivering up to 1 ampere at 60 to 80% power efficiency from a storage battery source, providing a positive DC power output free from inductor-generated type switching transients. The converter embodies a regenerative switching mode means which alternately drives two sets of paired power transistors, turning on each one pair of power transistors for one-half cycle. Each one of the power transistor pair alternately transfers electron charges to a first one of two switch-coupled capacitors, thence to the second one of the two capacitors, and then to a positive voltage terminal. RC clipping circuitry is coupled to each one of the pair of power transistors providing faster resetting times for the power transistors, increasing the converter power efficiency by decreasing storage-time delay. By decreasing power transistor direct shorting time during power transistor switching between transistor pairs, power loss is decreased.