| 摘要 |
1,106,654. Transistor switching circuits. ROBERT BOSCH G.m.b.H. 9 July, 1965 [10 July, 1964], No. 29113/65. Heading H3T. [Also in Divisions F1 and G1] In a monostable switching circuit both inductive and capacitive feedback circuits are used to control the duration of the unstable period. A positive input at 11 turns transistor 15 off and causes transistor 19 to conduct. The rising collector current through 19 induces a voltage pulse in primary winding 20 to control 15. As transistor 19 begins to conduct, diodes 26, 27 turn off because the voltage at junction 29 of potential divider 23, 24 becomes more positive. The voltage induced in winding 20 decays (Fig. 2, not shown), until the voltage across diode 26 causes it to conduct and allow capacitor 25 to discharge so as to maintain transistor 19 conducting for a longer period and so lengthen the unstable state of the circuit. When the resultant voltage from the winding 20 and capacitor 25 has fallen sufficiently the circuit reverts to its stable state, transistor 15 on and transistor 19 off. The time constant of the capacitive circuit 32 may be varied, e.g. by variable resistor 23 and the width of the pulses produced by the monostable circuits can be further varied by adjusting the inductive coupling. A further capacitive feed-back circuit (Fig. 3, not shown) may be connected in place of or in parallel with circuit 32 so as to correct overheating in electromagnetically controlled inlet manifold petrol injection by including a temperature sensitive resistor (43) in a position corresponding to resistor 23. In a still further circuit (Fig. 4, not shown), which may be connected in place of or in parallel with the other feedback circuits, the time delay which may occur in the operation of electromagnetically operated injection valves as the.supply voltage varies may be compensated by including a Zener diode (40) in the feedback circuit. |
