Browse Prior Art Database

Low Voltage Drop, Redundant Power Circuit

IP.com Disclosure Number: IPCOM000120821D
Original Publication Date: 1991-Jun-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Ferry, M: AUTHOR [+2]

Abstract

An electronic circuit is disclosed which allows providing a load with a power supply voltage from one or the other of two separate sources.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 65% of the total text.

Low Voltage Drop, Redundant Power Circuit

      An electronic circuit is disclosed which allows providing
a load with a power supply voltage from one or the other of two
separate sources.

      Compared to prior art circuits, the input to output voltage
drop in the disclosed circuit is greatly reduced.
1. REDUNDANT POWER SUPPLY CIRCUIT - PRIOR ART

      As shown in Fig. 1, the more commonly used circuit for
providing power supply redundancy is based on rectifier diodes. The
main drawback is the voltage drop, from 0.5 to 1 volt, which prevents
the circuit designer from using this simple circuit when, for
example, the power supply sources are specified at 5 volts +/- 5%,
and the load requires 5 volts +/- 10%.
2. REDUNDANT POWER SUPPLY CIRCUIT - LOW VOLTAGE DROP

      The disclosed circuit is shown in Fig. 2. The use of very low
resistance power MOSFET transistors, T1 and T2, is the key to the low
voltage drop.

      These transistors are driven by two comparators, M1 and M2,
which are connected in a SR Latch arrangement. The source terminals
of the N channel MOSFET transistors T1 and T2 are connected to the
power supply sources +5A and +5B, and their drain terminals are
commoned on the circuit output +5R. An important feature is that the
intrinsic diodes, D1 and D2, of T1 and T2 are thus connected in such
a way, that they participate to the redundancy and, also, isolate the
two power sources from each other.

      The circuit functionality can be...