| 摘要 |
1,188,189. Inverting. VARO Inc. 7 Aug., 1967 [9 Aug., 1966], No. 36169/67. Heading H2F. In a pulse width modulated inverter, a highfrequency oscillator 3 triggers a bi-stable circuit 4 to control the switching of an inverter 2 fed from a D.C. source 1. The square wave output from the inverter is pulse width modulated at a lower frequency by switching circuits 7 which periodically connects the output from the inverter 2 to a filter 6, depending on the state of bi-stable circuits 12A, 12B. Each bi-stable circuit 12A, 12B is controlled by a control circuit 10A, 10B comprising a tunnel diode, e.g. 24, which is switched by a high-frequency ramp signal from unit 11 superimposed on a lowfrequency sine wave signal from oscillator 8. In operation the output from oscillator 8 is compared with the output from the filter 6 in comparator 9, to provide a control signal which determines the point on the ramp at which the tunnel diodes are triggered from one state to the other. During a first time period T1, Fig. 11, transistor 26, 28 are conductive to close switches 16, 18 and thus short circuit terminals 33, 34 so that no signal is applied to filter 16. During period T1, bi-stable circuit 12A changes its state and terminals 33, 35 and 34, 36 are connected to feed the output, Fig. 12, of inverter 2 to filter 16. Thus the waveform of Fig. 12 is periodically connected to, and disconnected from the input of filter 16 to provide an input to filter 16 as shown in Fig. 13. After passing through the filter, the resulting output signal is a sine-wave phase locked to that from the reference oscillator 8. The circuit may be modified for polyphase operation, Fig. 15 (not shown), by providing a phase splitter (37) at the output of the oscillator 8 and repeating the units 9, 10, 12, 13, 7, 6 for each phase. |
