GB924361A - Regulated transistor oscillator - Google Patents

Abstract

924,361. Automatic voltage control systems. LEAR Inc. Oct. 18, 1960, No. 35652/60. Class 38 (4). [Also in Group XL (c)] A push-pull inverter oscillator of the saturable core type (see Group XL (c)) has retroactive means for maintaining the output constant. In the basic non-retroactively controlled circuit shown in Fig. 4, when, for example, transistor 132 is conducting, the voltage between points 114 and 116 is limited by the voltage drop in the emitter base path of transistor 132 together with the forward voltage drop in diode 148 and the zener voltage drop in diode 146. In addition, the positive spike of voltage which appears at the base of transistor 132 when the transistor saturates is limited by a circuit comprising the emitter base diode of transistor 130 the forward path of diode 150 and the zener voltage of diode 148 while the negative spike which appears at the base of transistor 130 renders the transistor momentarily conducting so producing a cancelling current in the transformer winding. If the voltage of the supply 154 exceeds a predetermined value a zener diode 144 breaks down causing a transistor 140 to short-circuit the zener diode 146 and reduce the output voltage to a substantially zero value. In the retroactively controlled circuit of Fig. 5, the diode 146 is replaced by a transistor 200 having its base connected through diodes 174 and 212 to tappings on the output transformer. In operation the voltage produced by the diodes is sufficient to break down a zener diode 196 causing the transistor 200 to conduct and so maintain the amplitude of oscillation constant. If the supply voltage 210 exceeds the maximum safe value, zener diode 204 again conducts, reducing the output to substantially zero value. Corresponding circuits using NPN transistors are also described (Figs. 5, 6 and 8, not shown).