A battery feed circuit with a current-controlled feedback loop supplying DC current to a load. The circuit is particularly adjustable to telephone systems and is characterized by low power dissipation.

Current controlled battery feed circuit

In one branch of the subscriber feed circuit (Ra, Rb, BS) is a FET transistor (Tr) is a current limiting element, which is driven upon reaching a limit value of the feed stream so that it limits the feed current. the limiting operating Lasts a first time period, then the supply current circuit is interrupted by blocking of the transistor. A through controlling the transistor into conduction is possible again only after a second longer period of time has elapsed which is sufficient to cool. The threshold value is not fixed but varies according to the amplitude and direction of the feed stream superimposed Storlangsstromen.

Circuit arrangement for overcharge protection of a subscriber current supply circuit, especially in a digital telephone exchange

A regulated power supply for application in a cable signal distribution amplifier comprises a filter, voltage doubler and current sense transformer controlled by a control technique known in the art. In the event of a high impedance short condition causing severe overcurrents, the known control technique is ineffective. To alleviate the problem, a high impedance current fault control circuit includes a sampling circuit, a level adjusting circuit, a differential amplifier for providing a monitor output control voltage and a buffer circuit to the controller. In the event of a high impedance current fault, the control circuit kicks in and interrupts controller operation saving power supply components from damage caused by the overcurrent condition.

Regulated current power supply with isolated secondary and output current limiting

Intrinsically safe battery pack e g for a miner's lamp

A method and apparatus for controlling the magnitude of an analog current through a load to be proportional to the magnitude of an input voltage. A sensing resistor is connected in series with the load. A controllable voltage is applied across the series connection of the load and sensing resistor for driving a current therethrough. A pulse width modulator receives the input voltage and a feedback voltage corresponding to the voltage drop across the sensing resistors when current is conducted thereby and produces square wave pulses each having a pulse width which is adjusted in response to a difference between the magnitudes of the input voltage and the feedback voltage. The magnitude of the controllable voltage is adjusted as a function of the pulse width of the square wave pulses until the magnitude of the current flowing through the load and sensing resistor causes the magnitude of feedback voltage to correspond to the magnitude of the input voltage so that the current through the load is maintained proportional to the magnitude of the input voltage.

Low power dissipation analog current loop output circuit

A current regulator for a pulse code modulated (PCM) transmission line is interposed between a voltage potential and a load (consisting of repeater amplifiers along the PCM transmission line) for limiting the current flow to the load. During normal operation, the regulator provides a relatively low impedance path from the voltage potential to the load through a series pass transistor and a sensing resistor. During an overload condition, which is sensed by the sensing resistor, the series pass transistor is deprived of base drive thereby providing a high impedance path with an accompanying increased voltage drop across the series pass transistor of the series regulator. This voltage drop is used to drive a timer which turns the series pass transistor off and on, with a low on time or duty cycle, in order to minimize power dissipation during the overload condition. After the overload condition has been alleviated, the series pass transistor is turned back on by the timer, and due to the low current flowing to the load, the series pass transistor is again returned to its relatively low impedance conducting condition.

Larry D. Bishop

Papers

Low power dissipation series regulator for PCM repeater lines