| 摘要 |
907,743. Converting. INVENTIO A.G. Oct. 28, 1960 [Nov. 5, 1959], No. 37114/60. Class 38 (2). [Also in Group XL (c)] In a pulse width modulator for controlling semiconductor switching amplifiers, the control potential is converted into pulses of corresponding amplitude which are amplified without transfer of D.C. component and used to charge a capacitor which is discharged to a fixed potential during the intervals between pulses. A further stage is provided to convert the sawtooth waveform thus formed into pulses of corresponding duration. The control potential shown at a in Fig. 2 is fed to terminals 11, 12 of Fig. 1. The normally conductive transistor 2 is cut off by pulses b so that pulses c, provided at the collector, may be amplified by an A.C. coupled-amplifier 4 giving waveform d. Capacitor 5 is charged from waveform d via the base emitter circuit of transistor 7. At the end of each pulse d transistor 7 is cut off until capacitor 5, discharging with constant current via resistor 9, again renders transistor 7 conductive, giving waveforms e at the base and f at the collector. Waveform f is squared by an overdriven amplifier or a Schmitt trigger 10 giving waveform g which is used to control semiconductor switching amplifiers the outputs of which control semiconductor or gaseous rectifiers or the control winding of a D.C. machine or magnetic amplifier. The system may be used with an A.C. or A.C. + D.C. control voltage applied to terminals 11, 12 if pulses b are synchronized with the A.C. input. |
