Abstract: This apparatus can limit the power by limiting the duty cycle of current carried by a pair of lines. These lines intermittently conduct electrical power. A clock can provide a periodic timing signal. This clock is resettable to change the phasing of the timing signal. A switch serially coupled to at least one of the lines can periodically interrupt current of the lines with a period proportional to the period of the periodic timing signal. A resetter coupled to at least one of the lines can reset the clock in response to the average magnitude of voltage across the lines increasing by a predetermined extent.

Abstract: A battery charger can charge a battery from a primary power source having a peak voltage exceeding the maximum battery voltage independently producible by the battery. The charger has output terminals, a switch and a feedback circuit. The output terminals are adapted for connection to the battery. The switch can periodically couple the primary power source to the output terminals to raise their voltage above the maximum battery voltage. The feedback device is responsive to the charging occuring at the terminals for limiting the current thereto by varying the duty cycle of the switch.

Abstract: This apparatus can apply electrical power to a supply terminal from a pair of lines having a variable current and voltage. The apparatus has a voltage tapper and a series device. The voltage tapper is coupled to the lines and to the terminal for applying to the latter power drawn from the lines when their voltage difference exceeds a predetermined value. The series device is serially coupled into a given one of the lines for producing a voltage drop. The series device is coupled to the supply terminal for supplying power thereto as a predetermined function of the voltage drop of the series device.

Abstract: Apparatus can limit power by limiting the duty cycle of current carried by a pair of lines. The lines intermittently conduct electrical power. The apparatus has a clock, a converter and a switch system. The clock can provide a timing signal. The converter is driven by the lines and can convert its intermittent electrical signals to uninterrupted power and can supply this uninterrupted power to the clock. The switch system responds to the timing signal and can periodically interrupt at least one of the lines.