Electrical power supply having a variable output

An electrical power supply having an output of variable e.m.f., comprising:

• at least two pairs of source circuits, each of said source circuits comprising at least two sources of e.m.f. each connected in series with a first diode means, means including a first switch interconnecting the junction between the sources of e.m.f. and the respective first diode means of each source circuit, said first switch being effective to cause said sources of e.m.f. in each of said source circuit to energize terminals of said source circuits in parallel when said first switches are open and in series when said first switches are closed, each of said source circuits being connected in series with a second diode means, the series combination of each said source circuit and said second diode means being connected in parallel, means including a second switch interconnecting the junction between each said source circuits and said second diode means at the terminals of each said source circuits, and said second switch being effective to connect said source circuits in parallel when said second switch is open and said source circuits in series when said second switch is closed, control means sensitive to the requirements of the load connected to the power supply for opening and closing said first and second switches to vary the e.m.f. of said power supply, said control means including a memory having a memory state corresponding to each output level of e.m.f. of said power supply wherein at least one of said memory states contains several switching arrangements for said first and second switches which are able to produce a substantially equal e.m.f., said control means further including a clock circuit connected to said memory for cyclically switching to each switching state within a memory state for equalizing the use of said sources of e.m.f. over a time period.