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# A Circuit to Prevent Shutdown Against Branch and Power Supply Short

IP.com Disclosure Number: IPCOM000014846D
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2003-Jun-20
Document File: 2 page(s) / 42K

IBM

Malik, R: AUTHOR

## Abstract

Problem A large system uses multiple processors and RAID systems to process information as shown in Figure 1. In such systems, each branch circuit can draw up to 240 VA power. If the branch tries to draw more than this VA limit, a signal is generated to shut down the whole power system. Prior Art Figure 1 shows three power supplies PS1, PS2 and PS3 in parallel to provide a bus voltage of V. Individual outputs from each power supply are ORed on a power back-plane which serves as a distribution point for all the power delivered to the system. The back plane has a current sense circuit for each branch to limit the power to 240 VA. In Figure 1, Rcs1 and Rcs2 are current sense resistors. As and when the current in a current sense resistor exceeds 240VA threshold requirement, it generates an over-current signal to shut down the whole system as shown in Figure 2.

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A Circuit to Prevent Shutdown Against Branch and Power Supply Short

Problem

A large system uses multiple processors and RAID systems to process information as shown in Figure 1. In such systems, each branch circuit can draw up - to 240 VA power. If the branch tries to draw more than this VA limit, a signal is generated to shut down the whole power system.

Prior Art

Figure 1 shows three power supplies PS1, PS2 and PS3 in parallel to provide a bus voltage of V. Individual outputs from each power supply are ORed on a power back-plane which serves as a distribution point for all the power delivered to the system. The back plane has a current sense circuit for each branch to limit the power to 240 VA. In Figure 1, Rcs1 and Rcs2 are current sense resistors. As and when the current in a current sense resistor exceeds 240VA threshold requirement, it generates an over-current signal to shut down the whole system as shown in Figure 2.

Problem Solved

The proposed circuit has a switching transistor for each branch. Instead of using a Schottky diode in the power supply, a low drop switching transistor which can be turned on and off is used in each branch. In case of a particular branch fault, the branch transistor is turned off but the other branch continues to provide power to the system. The proposed circuit is more efficient and scalable for branch protection.

Circuit Description

Figure 2 shows a circuit to protect the power system from shutdown. For example, if there is an overload on the system 1, Q1A, Q2A and Q3a are turned off by sensing the fault current by resistor Rcs1. System 2 remains unaffected. Similarly system 1 which is powered by branch 1 is not affected if there is an overload fault in branch 2.

The proposed circuit is scalable depending upon the system requirement. Multiple processors and RAID systems are used in medium to largeserver systems. Most of these processors operate in parallel and the RAID configuration stores identical data on multiple hard drives. Each processor and its associated circuitry can be powered on its own independent power branch and therefore it is very essential that the whole server should never shutdown if any one of the branches get...