Switching circuit for operation and dynamic braking of a dc motor

Claim 2

A switching circuit for selectively controlling the operation and dynamic braking of a direct current motor having first and second armature terminals, comprising: a driving circuit for connecting a direct current power source across said first and second armature terminals of said motor to drive said motor in a forward direction, which driving circuit comprises; a first diode having an anode for connection to a positive side of said direct current power source and a cathode for connection to said first armature terminal, a NPN transistor having a collector for connection to said second armature terminal and an emitter for connection to a negative side of said direct current power source, and a resistor connected between the base of the NPN transistor and the cathode of the first diode. whereupon, when the first diode cathode is connected to said first armature terminal and the NPN transistor collector is connected to said second armature terminal and the NPN transistor emitter is connected to said negative side of said direct current power source, the connection of the first diode anode to said positive said of said direct current power source enables the NPN transistor to conduct thereby completing the driving circuit to drive said motor in said forward direction, and a dynamic braking circuit for connection across said armature terminals of said motor to dynamically brake said driven motor upon the driving circuit being opened so that said armature is coasting in said forward direction, which dynamic braking circuit comprises; a PNP transistor having an emitter connected to the cathode of the first diode, having a base connected to the anode of the first diode, and having a collector operatively connected to the collector of the NPN transistor. a second diode having a cathode connected to the collector of the NPN transistor, and a second resistor connected between the base of the PNP transistor and the anode of the second diode, whereupon, when the driving circuit is connected to said direct current power source and to said armature terminals and said motor is being driven in said forward direction, the opening of the driving circuit by disconnecting the anode of the first diode from said positive side of said direct current power source to terminate conduction in the NPN transistor thereby causes the armature to coast in the forward direction to generate electrical energy and also thereby enables the PNP transistor to conduct in response to said generated electrical energy to complete the dynamic braking circuit across said first and second armature terminals.

Claim 3

A switching circuit according to claim 1 for selectively controlling the direction of operation and dynamic braking of a direct current motor, further comprising: a second driving circuit for connecting said direct current power source across said first and second armature terminals of said motor to drive said motor in a reverse direction, which driving circuit comprises: a third diode having an anode for connection to said positive side of said direct current power source and a cathode for connection to said second armature terminal, a second NPN transistor having a collector for connection to said first armature terminal and an emitter for connection to said negative side of said direct current power source, and a third resistor connected between the base of the second NPN transistor and the cathode of the third diode, whereupon, when the third diode cathode is connected to said second armature terminal and the second NPN transistor collector is connected to said first armature terminal and the second NPN transistor emitter is connected to said negative side of said direct current power source, the connection of the third diode anode to said positive side of said direct current power source enables the second NPN transistor to conduct thereby completing the second driving circuit to drive said motor in said reverse direction: and a second dynamic braking circuit for connection across said armature terminals of said motor to dynamically brake said driven motor upon the second driving circuit being opened so that said armature is coasting in the reverse direction, which second dynamic braking circuit comprises: a second PNP transistor having an emitter connected to the cathode of the third diode and having a base connected to the anode of the third diode, a fourth diode having an anode connected to the collector of The second PNP transistor and a cathode connected to the collector of the second NPN transistor, a fifth diode having a cathode connected to the collector of the second NPN transistor, and a fourth resistor connected between the base of the second PNP transistor and the anode of the fifth diode, whereupon when the second driving circuit is connected to said direct current power source and to said armature terminals and said motor is being driven in said reverse direction, the opening of the second driving circuit by disconnecting the anode of the third diode from said positive side of said direct current power source to terminate conduction in the second NPN transistor thereby causes the armature to coast in the reverse direction to generate electrical energy and also thereby enables the second PNP transistor to conduct in response to said generated electrical energy to complete the second dynamic braking circuit across said first and second armature terminals; and the dynamic braking circuit according to claim 1 further comprises a sixth diode having an anode connected to the collector of the PNP transistor and a cathode connected to the collector of the NPN transistor.