GB1215376A - Device for producing a pair of signals with phase displacement - Google Patents

Abstract

1,215,376. Pulse shaping and phase changing Circuits. MOBIL OIL CORP. 11 Jan., 1968 [12 Jan., 1967], No. 1626/68. Heading H3T. [Also in Division H2] In a system for producing a pulse train displaced in phase from an input train, e.g. for driving a synchronous motor, the input train is converted to a train of double the frequency and half the width and edges of one polarity in the train are used to define the leading and trailing edges of the output train. As shown, pulses XI from block 34 are differentiated at 36 and the negative output removed at 38. They are also inverted at 42, differentiated at 44 and the negative pulses removed at 46 so that the output of the OR gate 40 is a double-frequency positive pulse train. These pulses each cause a storage element 48 to quickly charge and this is dissipated in a contsant current discharge circuit in 50 so that sawtooth waves are produced. These are applied to a Schmitt trigger 54 to convert the waves to a square wave train each pulse of which reverses the state of a divide-bytwo bi-stable circuit which therefore provides a square wave output displaced in phase by 90 degrees from the input from 34. The two trains are applied through 62 and 60 to a synchronous motor. As described the circuit is used to control the motor in dependence upon pulses received in a sensor 10 in the fuel injection line of a diesel engine. The output of the sensor is applied via a source follower 12 and an inverter 14 to a Schmitt trigger 18 via a threshold level setter 18. The output of the Schmitt circuit operates a mono-stable circuit 20 to ensure that closely spaced pulses appear as a single rectangular pulse. The resulting output is amplified and inverted at 22, differentiated at 24 and the negative pulses removed at 26. The remaining positive pulses cause a storage circuit 28 to rapidly charge and this charge is dissipated in a constant current circuit 28 to produce sawtooth waves. These waves are centered about a zero level in 32 and applied to a Schmitt trigger to provide the square wave XI referred to above. Conventional transistor circuits for use in the blocks are described with reference to Figs. 2, 3 and 4 (not shown) which respectively include the combinations of blocks as indicated in Fig. 1.