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Feedback Control

IP.com Disclosure Number: IPCOM000091902D
Original Publication Date: 1968-Jul-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Johnson, AK: AUTHOR [+3]

Abstract

Input drive signals to solid state devices coupled in a bridge arrangement are logically controlled. Such assures proper operating sequences without shorting of the devices while minimizing the delay of turnon time.

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Feedback Control

Input drive signals to solid state devices coupled in a bridge arrangement are logically controlled. Such assures proper operating sequences without shorting of the devices while minimizing the delay of turnon time.

The bridge comprising transistors 10...13 is shown controlling motor 15. Assume normal forward operation occurs when 11 and 12 are on. Normal reverse operation occurs when 10 and 13 are on. Forward stopping is accomplished by turning off 11 and 12, turning 10 and 13 on for a brief period, the forward plug, and then turning 13 off and 11 on for dynamic braking. The backward plug is provided by turning 10 and 13 off, after which 11 and 12 are turned on with 10 and 11 providing following dynamic braking. A problem can arise if there is a delay in turning off a transistor so that both 10 and 12 or both 11 and 13 should be simultaneously on, thus shorting power source -V to ground. This problem has been resolved in the past by delaying the turnon input signals for a fixed length of time. This necessarily means that the transistors must be inoperative for a longer period than is actually needed. The circuit shown logically inhibits the on signals until no shorting condition can occur.

When 11 is turning off while a conduction input signal for 13 is being introduced at 16, the base voltage of 11 is compared against a reference voltage at 17 in voltage comparator 18. The output of 18 is Anded with 16 in And 19. When the base voltage of 11 approaches a level indicating that 11 ceases conduction, 18 completes the conditioning of 19 and a signal is passed through driver amplifier 20 to tu...