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Reversible DC Motor "H" Driver Circuit with Short Circuit and Totem Pole Protection

IP.com Disclosure Number: IPCOM000051908D
Original Publication Date: 1981-Apr-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Arter, NK: AUTHOR [+3]

Abstract

This is a circuit for protecting DC motors against the most common failures without using high maintenance protectors, such as fuses. This circuit is designed to be failsafe when the motor terminals are shorted to ground or to each other. Additionally, this circuit eliminates "totem pole" failures.

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Reversible DC Motor "H" Driver Circuit with Short Circuit and Totem Pole Protection

This is a circuit for protecting DC motors against the most common failures without using high maintenance protectors, such as fuses. This circuit is designed to be failsafe when the motor terminals are shorted to ground or to each other. Additionally, this circuit eliminates "totem pole" failures.

The figure shows a DC motor 10 with terminals 11 and 12. A power source Vcc is connected to terminal 11 through transistor switch Q3, and to ground by transistor Q6. For running the motor in reverse, terminal 12 is connected to Vcc through transistor Q5 and to ground by transistor Q4. Transistor Q3 is triggered by transistor Q1 through PNP transistor Q2. Operational Amplifier 0A1 triggers transistor Q1 in response to an input signal. Similarly, Q5 is triggered by Q8 through PNP transistor Q7, and Op Amp 0A2 triggers Q8 in response to an input signal. Note that terminal 11 is connected to the output of 0A1 through diode D1, and terminal 12 is connected to the output of 0A2 through diode D2.

During operation, either Q1 or Q8 is turned on by the respective operational amplifier 0A1 or 0A2. If Q1 is operative, Q3 will turn on and D1 will be reverse biased. Q6 is turned on by Q1, thus establishing the current flow path through motor 10. Operation in the reverse direction is similar. Use is made of the motor inductive delay to keep point 13 from being clamped through D1 and Q6 when motor impe...