Motor speed control circuit

Claim 2

A switching circuit responsive to two complementary constant frequency pulses of variable duration for the controlled application of DC power through a DC motor load, comprising: a transformer having a primary and a secondary winding, said primary winding having one end thereof for connection through a DC motor load to a positive source of direct current power, one end of said secondary winding being connected to a common circuit ground, the polarity of said secondary winding being selected such that a current is conducted from said one end of said secondary winding in response to a current entering said one end of said primary winding; a first controlled rectifier having an annode, a cathode, and a gate electrode, said annode being connected to the other end of said primary winding, said cathode being connected to said common circuit ground, said gate electrode and said common ground being adapted to be connected to a source of one of the two Complementary constant frequency pulses of variable duration; a diode having an annode and a cathode, said annode being connected to the other end of said secondary winding; a second controllable rectifier having an annode, cathode, and a gate electrode, said cathode being connected to said common circuit ground, said annode being connected to the cathode of said diode; a resistor connected between said gate electrode and said cathode of said second controllable rectifier; a first capacitor having one end thereof connected to said gate electrode of said second controllable rectifier, the other end of said capacitor and said common ground being adapted to be connected to a source of the other of said two complementary constant frequency pulses of variable duration; a second resistor having one end thereof connected to the annode of said first controllable rectifier; and a second capacitor connected between the other end of said second resistor and the annode electrode of said second controllable rectifier.

Claim 3

The switching circuit described in claim 1 further including: an oscillator for providing a constant frequency periodic signal; a monostable multivibrator having an input and output, said input being connected to said oscillator, said constant frequency periodic signal of said oscillator triggering said monostable multivibrator to produce a constant frequency pulse at said output, said monostable multivibrator having a variable resistor to control the duration of said constant frequency pulse; driver means having an input connected to said monostable multivibrator output, said driving means having an output connected between said common ground and said gate electrode of said first controllable rectifier whereby the constant frequency pulse of controllable duration from said monostable multivibrator is said source of one of two complementary constant frequency pulses of variable duration which is applied between said common ground and said gate electrode of said first controllable rectifier to render said first controllable rectifier conductive which in turn renders said second controllable rectifier non-conductive if said second controllable rectifier was in a conductive state; and inverter and driver means connected between said multivibrator output and said other end of said first capacitor for inverting the monostable multivibrator output and said other end of said first capacitor for inverting the monostable multivibrator pulse output and applying it between said common ground and said first capacitor and through said first capacitor to the gate electrode of said second controllable rectifier whereby the constant frequency pulse of controllable duration from said inverter and driver means is said source of the other of two complementary constant frequency pulses of variable duration which renders said second controllable rectifier conductive and in turn renders said first controllable rectifier non-conductive if said first controllable rectifier was in a conductive state.

Claim 4

The switching circuit described in claim 2 wherein said oscillator is a constant frequency unijunction transistor oscillator circuit.

Claim 5

The switching circuit described in claim 3 wherein said monostable multivibrator is an integrated circuit.

Claim 6

The switching circuit described in claim 4 further including: a direct current motor load connected between said one end of said primary winding and the positive source of direct current power; and a diode having an anode and a cathode electrode, said anode electrode being connected to said one end of said primary winding and said cathode electrode being connected to the positive side of a source of DC power to which said motor is connected whereby said diode provides a short circuit to voltages and currents generated by said motor load when power is removed therefrom by said first controllable rectifier being rendered non-conductive.