Patent GB-1274191-A (GB)
Title: Improvements in or relating to an electric controller device having means for stabilizing a voltage stored on a capacitor
Inventor: HUTCHEON IAN CARRODUS
IPC: G05B11/26
Filed: 1968-02-05
Abstract: 1,274,191. Transistor oscillators. GEORGE KENT Ltd. 2 May, 1969 [5 Feb., 1968], No. 5749/68. Heading H3T. [Also in Division G3] A controller having a memory capacitor whose voltage is automatically stabilized to prevent drift during manual operation (see Division G3) includes the circuit shown in Fig. 4, in which transistors 51, 52 form part of a slow oscillator providing a ramp waveform comprising portions ascending to and declining from the capacitor voltage, Fig. 5 (not shown), and transistors 63, 64 form part of a fast oscillator providing a sawtooth pulse train which begins with the ramp waveform and dies away rapidly during the reset (declining) portion thereof. The ascending ramp portion is obtained with transistor 51 conducting and the emitter of transistor 52 going positive, the portion terminating when the emitter reaches the capacitor voltage applied to the transistor base through a diode 54. The collector of transistor 51 may be positive with respect to the base of transistor 52, and a capacitor 55 ensures instantaneous positive feedback and rapid switchover at the end of the ascending portion if the self-capacitance of diode 56 is not sufficient. Transistor 63 is set into oscillation at the start of the. ascending portion by a positive potential on the collector of transistor 51 which also switches off transistor 64 through diode 65. At the end of the ascending portion the collector of transistor 51 goes magnetic and turns off the oscillator gradually by carrying the base of transistor 64 with it, the arrangement being such that the cycle in progress is completed without substantial degradation. Simultaneously the collector of transistor 52 goes positive to briefly operate a transistor 38, which normally shunts the output of the fast oscillator and is opened to allow this output (if any) to be applied, through members 39, 40, 66, as a correction pulse to the capacitor. A capacitor 67 prevents transmission of spikes from the fast to the slow oscillator. A split timing capacitor 92, 94 is used to provide the sawtooth waveform. The modification shown in Fig. 6 has a low value capacitor 70 in the output line 72 of the oscillator, which is stopped by positive potential on the collector of the transistor 51 of the slow oscillator whose ramp waveform is similar to that previously mentioned, Fig. 7 (not shown), It is explained how the correction pulse from the fast oscillator to the capacitor may comprise a single or a double pulse according to whether the collector of transistor 51 goes negative during the negative or the positive portion of the sawtooth waveform of the fast oscillator, Fig. 8 (not shown). A capacitor 84, which prevents interaction between the two oscillators, also introduces a small repeatable delay at starting and stopping of the circuit to ensure that the transistor 38 opens before a correction pulse occurs, increase of the delay modifying the double correction pulse without affecting the operation of the fast oscillator. Members 95, 96, 98 provide the sawtooth waveform. The gating diodes of the oscillators may be replaced by a transistor and resistors and a capacitor may be added to ensure instantaneous positive feed-back at the end of the slow oscillator ascending portion, Fig. 9 (not shown). A resistor, capacitor and diode circuit may be added to control the base of transistor 38 to limit the number of spurious operations of the latter during each slow oscillator cycle, Fig. 10 (not shown). Also transistor 38 cannot be opened until a predetermined time after it has opened to pass a correction pulse.