Browse Prior Art Database

Electronic Load

IP.com Disclosure Number: IPCOM000059929D
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Brunken, J: AUTHOR [+2]

Abstract

This article relates to an electronic load EL for drawing a desired load current from a power supply for the automated testing of the latter. As shown in Fig. 1, the electronic load consists of a series of metal-oxide semiconductor field-effect transistors (MOSFETs). The total load current IL, drawn from the power supply under test (PSUT), is controlled by a control unit CU which may form part of a microprocessor. For each binary weight, unit CU supplies a gate control signal d0 to d7 to eight MOSFETs MF0 to MF7. For low-order signals, one MOSFET, such as MF0, is provided for each weight, whereas for high-order signals, it may be necessary to connect two or more MOSFETs, such as MF7A and MF7B, in parallel, if the current controlled by the respective weight exceeds the maximum admissible MOSFET current.

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Electronic Load

This article relates to an electronic load EL for drawing a desired load current from a power supply for the automated testing of the latter. As shown in Fig. 1, the electronic load consists of a series of metal-oxide semiconductor field-effect transistors (MOSFETs). The total load current IL, drawn from the power supply under test (PSUT), is controlled by a control unit CU which may form part of a microprocessor. For each binary weight, unit CU supplies a gate control signal d0 to d7 to eight MOSFETs MF0 to MF7. For low-order signals, one MOSFET, such as MF0, is provided for each weight, whereas for high-order signals, it may be necessary to connect two or more MOSFETs, such as MF7A and MF7B, in parallel, if the current controlled by the respective weight exceeds the maximum admissible MOSFET current. The control circuit for each MOSFET MF is shown in Fig. 2. Signal b is applied to a driver DR by means of an optocoupler OK. The driver output signal is adjusted by series-connected resistor R and trimmer potentiometer P, such that the amplitude of signal d at the MOSFET gate causes the desired current I to flow through the MOSFET. Current I is measured by a jaw-type current probe. For high currents, it may be necessary to provide one or several parallel-connected MOSFETs on a heat sink HS. As the current through a MOSFET decreases in response to a temperature increase, the gate voltage should be raised accordingly to maintain a temperature-independent current. This can be achieved by also providing a temperature-dependent negative temperature coefficient resistor NTC on the heat sink and using this resistor to generate a reference voltage for an integrated circuit regulated power sup...