GB962647A - Improvements in or relating to the generation of electric oscillations - Google Patents

Abstract

962,647. Frequency changing. FERGUSON RADIO CORPORATION Ltd. July 3, 1961 [May 11, 1960], No. 16635/60. Heading H2F. [Also in Division H3] A frequency conversion system comprises a switching circuit which connects an A.C. power source to a smoothing circuit when the magnitude of a lower frequency reference voltage is less than that of the power source and greater than that of the smoothing circuit whereby power at the reference frequency is supplied to a load connected across the smoothing circuit. In Fig. 1 a source of power at a frequency of 4 kc/s. is applied at terminals 10 and 12 and 18 is a reference source of 50 cycle frequency. Transistors 15 and 16 conduct when the reference voltage magnitude is less than the power source voltage but greater than the voltage across the output smoothing circuit 20 so that the output power is derived from the input power source but the output voltage is of the frequency and waveform of the reference voltage. Diodes 14 prevent the transistors conducting in the forward direction of the collector diode and a resistor 17 prevents source 18 being unduly loaded when the collector voltage falls below the reference voltage. Fig. 2 shows an alternative embodiment in which the transistor switches (represented at 21) are controlled by comparators 22. Thus, switch 21 is rendered conductive by comparator 22 when the instantaneous voltage applied to the comparator from the 4 kc/s. generator is greater than the voltage applied to the comparator from the reference voltage source provided operation of the comparator is not inhibited by a further comparator 23 which provides the inhibiting voltage when the reference voltage is less than the load voltage. In a further embodiment (Fig. 3, not shown) each of the switches 15, 16 of Fig. 1 is duplicated to provide full wave operation so that the 4 kc/s. frequency current in the load is reduced. In addition an inductor in series with the load further reduces the 4 kc/s. output component. It is also stated that switching arrays common in power rectification practice may be used, for example full wave and bridge arrays and that such arrays may be used with a polyphase reference and separate phase filtering may be provided so that a polyphase lowfrequency supply may be provided from a single phase or polyphase high-frequency source.