Battery charger

A battery charger comprising a source of unidirectional current pulses adapted to be supplied to a battery,

• a controllable switching device in series with said current source,
• a first timing capacitor,
• a controllable current source operating in synchronism with the current pulses and connected to the timing capacitor,
• a gating circuit including a unijunction transistor with its emitter circuit connected to the timing capacitor, producing control pulses coupled to said switching device to place it in conduction for a portion of the period of each unidirectional current pulse, said control pulses being in synchronism with said current pulses but having a variable period with respect thereto,
• a battery voltage responsive control circuit producing a signal indicative of the difference between the battery voltage and a reference voltage, said signal being coupled to the controllable current source to control the charging rate of said capacitor,
• transistor switching means coupled to the controllable current source to override the signal from the voltage control circuit and place said controllable current source in a condition of maximum supply, and timer means controlling said transistor switching means, said timer means including an FET, a second timing capacitor connected in the gate circuit of the FET, said second timing capacitor being charged from the power supply for said transistor switching means.