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Current Sensing Circuit for High Potential Direct Current Bus

IP.com Disclosure Number: IPCOM000080792D
Original Publication Date: 1974-Feb-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Felton, BC: AUTHOR [+4]

Abstract

In the two circuits of the drawing, a voltage Vin is produced across a resistor that is connected in an electrical bus, which has a potential that is significantly higher with respect to ground than the operating voltage of semiconductor components. The two circuits each produce an output voltage Vo with respect to ground that is proportional to Vin, and thus is proportional to the current in the high-potential bus. In Fig. 1, a differential amplifier 2 has its inputs connected to receive the voltage Vin, so that its output voltage is a function of the current in the bus. However, amplifier 2 receives its operating voltage from two zener diodes 3 and 4 that are at about the potential of the bus.

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Current Sensing Circuit for High Potential Direct Current Bus

In the two circuits of the drawing, a voltage Vin is produced across a resistor that is connected in an electrical bus, which has a potential that is significantly higher with respect to ground than the operating voltage of semiconductor components. The two circuits each produce an output voltage Vo with respect to ground that is proportional to Vin, and thus is proportional to the current in the high-potential bus. In Fig. 1, a differential amplifier 2 has its inputs connected to receive the voltage Vin, so that its output voltage is a function of the current in the bus. However, amplifier 2 receives its operating voltage from two zener diodes 3 and 4 that are at about the potential of the bus. Thus, the output of amplifier 2 has a component that is proportional to Vin, and it has a component that is proportional to the bus potential with respect to ground.

A differential amplifier 5 receives the output of amplifier 2 and receives a signal from zener diodes 3 and 4. At the output of amplifier 5, the components that are proportional to the potential of the bus cancel and the signal Vo is proportional to the bus current. The resistors in the circuit isolate the output of amplifier 5 from the high potential of the bus. These resistors have the following values that simplify the relationship of Vo to Vin. R3 over R1 = R4 over R2 R7 over R5 = R8 over R6. For these resistor values, Vo = Vin x R3 over R1 x R7 over R5.

In the circuit...