Browse Prior Art Database

Zero Current Switch

IP.com Disclosure Number: IPCOM000086700D
Original Publication Date: 1976-Oct-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

McDowell, JR: AUTHOR

Abstract

A zero-current switch provides a logic-level signal which indicates whether the output current of a solar cell device is positive or negative. The switch is designed to provide a precise switching level, to minimize delay time and has an inherent hysteresis which minimizes the effect of noise.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 76% of the total text.

Page 1 of 2

Zero Current Switch

A zero-current switch provides a logic-level signal which indicates whether the output current of a solar cell device is positive or negative. The switch is designed to provide a precise switching level, to minimize delay time and has an inherent hysteresis which minimizes the effect of noise.

The first operational amplifier stage 11 converts the input current from the solar cell source 13 to a clamped voltage output. Resistors 15 and 17 bias the operational amplifier while minimizing the effect of input offset currents. Resistors 19 and 21 balance the input to the operational amplifier and compensate for small DC offsets in the input current. This compensation is made by using resistor 21 to adjust the voltage across resistor 19 within a voltage reference generated by the zener diodes and associated diode resistor network, which is designed to track the temperature response of the solar cell input.

The output voltage of the operational amplifier stage 11 is generated by the amplification and clamping action of resistor 27, zener diodes 29 and 31 and their associated diodes and resistors. With a drive current into the operational amplifier, the inverting input is driven more positive than the noninverting input causing the output to be driven negative until clamped by zener diode 29 and its associated diode.

The second operational amplifier stage 33 provides hysteresis to minimize the effect of noise. The positive feedback across the operation...