Patent GB-845905-A (GB)
Title: Electrical circuit with two stable states
Inventor: BONN THEODORE HERTZ
IPC: H03K3/45
Filed: 1957-03-21
Abstract: 845,905. Magnetic amplifiers. SPERRY RAND CORPORATION. March 21, 1957, No. 9303/57. Class 40 (9). Circuit arrangements employ magnetic cores wound with control- and load windings which are gated to have alternate control and load half-cycles, the arrangement being such that one of two output circuits is energized depending on whether a feedback path is energized or inhibited. The invention may utilize the component circuits shown in Figs. 1 and 13. In Fig. 1 a core carries an input winding 17 and output winding 12 and 19. Positive half cycles from a square wave source PP energize winding 12 and if, during a preceding negative half-cycle, control winding 17 is energized so that the core is driven to saturation in one direction, the subsequent pulse in winding 12 switches the core to its other state. Magnetizing current necessary to switch the core is absorbed by sneak suppressor 13, 14, 15 and the voltage induced in winding 19 appears on lead D from across load 21. If no input is applied to energize the control winding 17 in the preceding half-cycle, the positive pulse in winding 12 meets low impedance and appears on the lead C. A source of blocking pulses BP and the negative half-cycles of source PP are used to back off voltages induced in windings 17 and 12. In Fig. 13 a separate driving winding 134 is provided to drive the core 130 to saturation in one direction in which condition the potential of battery 137 appears on output lead C. If an output pulse to winding 131 reverses the saturation of the core during a negative halfcycle of source PP the next positive halfcycle of PP turns the core back to its initial state inducing an output voltage in winding 132 which appears on lead D and also induces a voltage in winding 133 which backs off the voltage of battery 137 and removes the output on lead C. Circuits of the type shown in Figs. 1 and 13 are illustrated in Fig. 4 by the symbols 43 and 44 each of which have input terminals I, output terminals C and D, and are energized by square wave sources PP-1, PP-2, in antiphase. The outputs C and D of the circuits 43 and 44 are connected in common and the outputs D are connected over an inhibition gate 39 to control gates 41 and 42 in cross connections made between the sources PP-1 and PP-2 and the circuits 43 and 44. If a set input on terminal 40 enables gates 41 and 42, a positive pulse from source PP-1 or PP-2 is applied as an input to circuit 44 or 43 to ensure one output D in the following half cycle this output being fed back to hold the gates 41 and 42 enabled and permitting further inputs and a D.C. output on the lead 49d. If a reset input is applied to terminal 40a to inhibit gate 39, gates 41 and 42 block inputs to the circuits 43 and 44 which in consequence revert to a C output and produce a D.C. output on lead 49c with the D outputs and the feed-back path unenergized. A D.C. output on lead 49d may be re-established by a further set input on terminal 40. As an alternative to the arrangement of Fig. 4 the feed-back may be taken from the combined C outputs instead of the D outputs in which event inhibition gates are placed in the cross connections between sources PP-1, PP-2, and the inputs to circuits 43, 44 in place of the gates 41, 42. D outputs can then be obtained by the direct injection of a positive input to either or both circuits 43, 44, while C outputs are produced in response to the direct injection of a positive pulse in the feed-back path which had no need for the inhibition gate 39. In Fig. 9 the D output of circuit 90 is combined with the C output of circuit 91 and vice versa, the combined C and D outputs of circuits 90 and 91, respectively, being fed back to inhibit the input of pulses from sources PP-1 to circuit 90 while enabling gate 93 to permit the input of pulses from source PP-2 to circuit 91. With the feed-back path energized therefore circuit 90 produces C outputs and circuit 91 produces D outputs resulting in a D.C. output on head 96. If a set input is applied directly to the input of circuit 90, or to inhibition gate 94 to block the application of the feed-back signal to gate 93 and thereby block the input to circuit 91, circuit 90 switches from a C to a D output, or circuit 91 switches from a D to a C output, in either event removing the feed-back signal to allow continued input pulses to circuit 90 and no input to circuit 91 so that a D.C. output is supplied to lead 95. The D.C. output on lead 96 may be re-established by applying a reset input to circuit 91 or by applying a reset input to inhibit gate 92 and cut-off the input to circuit 90. A further alternative arrangement is shown in Fig. 14 and uses cores 140, 141, the control windings on which are energized from D.C. sources +E4 and the controlled windings on which are energized from sources PP-6 to PP-9 having waveforms as shown in Fig. 15. With control windings energized sources PP-6 and PP-8 meet a high impedance as they switch the core with their positive half-cycles and in consequence they provide no output on lead D, sneaks being suppressed by 128, 129, - E2. Sources PP-7 and PP-9 also find high impedance in windings 155 and 157 when their voltage goes to earth and in consequence the source of D.C. + E3 appears as an output on lead C limited to the voltage +V. If a pulse of + E4 is applied to the normally grounded terminal 142 one of the control windings is isolated and a positive pulse from source PP-6 or PP-8 meets low impedance in winding 149 or 150 thereby putting an output on leads D and cutting off rectifier 151. With 151 blocked the potential of + E4 normally on terminal 143 is connected to feed-back path 158 and is applied to the upper ends of control windings 146, 147 to prevent their energization independently of the input pulse on terminal 142. Both sources PP-6 and PP-8 therefore meet low impedance in their associated windings and supply alternate positive pulses to put a D.C. output on the lead D. Output on lead C is prevented as the windings 155 and 157 have low impedance when the core is not being switched and the lead C is therefore effectively earthed alternately by sources PP-7 and PP-9. To reset the arrangement to its initial state an earth pulse is applied to terminal 143 to earth the feed-back path and re-establish current in the control windings 146, 147. Sources PP-6 and PP-8 now switch the cores and their positive half-cycles are thereby dissipated without putting an output on the D leads. Windings 155 and 157 have high impedance and disconnect the earth provided by alternate halfcycles of sources PP-7 and PP-9 so that the source of potential +V appears on the C lead. In Fig. 16 an arrangement is shown which uses a single core in conjunction with delay lines. Here sources PP-4, PP-5 each produce a square waveform, PP-4 alternating between +V and -V while PP-5 alternates between ground and +2V in antiphase. The control winding 161 is energized from a D.C. source of + E4 over a resistor 180 to a source of -V. During negative half-cycles of PP-4 the control winding saturates the core in one direction while the subsequent positive half-cycle of PP-4 switches the core back, magnetizing current through winding 162 being taken by sneak suppressor - V3, 182, 183, and no voltage therefore being applied to lead D. Winding 163 has a high impedance in this half-cycle so that a source of potential of +V limited to +V1 is applied to the C lead over resistor 177 and continues to be applied for as long as the core is being switched. If a pulse of +E4 is applied to the terminal 164 the control winding is disconnected and a positive pulse from PP-4 finds low impedance in winding 162 and is applied to lead D and also to delay line 166 which re-applies the pulse to the D lead at the end of the pulse from PP-4 and until the next pulse from PP-4 arrives. A D.C. signal is therefore present on the lead D and is applied to a potential chain of resistors 189, 171, between sources of +V and -V to cut-off a rectifier 170 which is normally conducting and at earth potential. With rectifier 170 disconnected the potential of point 173 rises from earth to a value of +E normally on terminal 165 which is fed back to hold the control winding 161 disconnected and preserve the output on lead D. No output appears on the lead C as winding 163 has low impedance when PP-5 goes to ground and the potential of +V is dissipated over resistance 177. When PP-5 rises to +2V rectifier 176 is cut off but any tendency of the lead C to rise above earth is removed due to the fact that the left-hand end of delay line 167 was earthed in the preceding half-cycle and in consequence the right-hand end provides an earth in the subsequent half-cycle. To remove output from the D lead and produce output on the C lead the potential of +E on terminal 165 is destroyed by an earth pulse to ground the feedback line and permit re-energization of the control windings. Windings 162 and 163 now have high impedance as the core is being switched, positive pulses from PP-4 are consequently dissipated and produce no D output while the potential +V1 appears as a C output.