Browse Prior Art Database

Using the Power Supply's EPOW Signal To Capture And Log Non-Disruptive Power Line Disturbances

IP.com Disclosure Number: IPCOM000013577D
Original Publication Date: 2000-Apr-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Abstract

The power subsystem of a Netfinity server is typically equipped with an EPOW (emergency power off warning) signal line. The purpose of this line is to warn the system that AC power has dropped below its normal voltage range. This allows the system to shut down in an orderly fashion and not risk data integrity or unpredictable behavior if DC power is lost. The system may or may not shut when the EPOW line is triggered by low AC voltage. This depends on factors such as how low the AC voltage dips, how long the AC voltage is below normal, and the DC load at the time of the AC voltage drop. This is because the power subsystem monitors the DC voltages to determine when to shut down the system. If any of the DC voltages drop below their specified levels, the power subsystem will shut down. Here is the sequence of events that would take place if AC power is lost long enough for the system to shut down: 1. AC power drops below the normal voltage range. 2. The power subsystem triggers the EPOW line. All DC voltages are still within specification.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

  Using the Power Supply's EPOW Signal To Capture And Log Non-Disruptive Power Line Disturbances

The power subsystem of a Netfinity server is typically equipped with an EPOW (emergency power off warning) signal line. The purpose of this line is to warn the system that AC power has dropped below its normal voltage range. This allows the system to shut down in an orderly fashion and not risk data integrity or unpredictable behavior if DC power is lost. The system may or may not shut when the EPOW line is triggered by low AC voltage. This depends on factors such as how low the AC voltage dips, how long the AC voltage is below normal, and the DC load at the time of the AC voltage drop. This is because the power subsystem monitors the DC voltages to determine when to shut down the system. If any of the DC voltages drop below their specified levels, the power subsystem will shut down.

Here is the sequence of events that would take place if AC power is lost long enough for the system to shut down:

1. AC power drops below the normal voltage range.
2. The power subsystem triggers the EPOW line. All DC voltages are still within specification.
3. DC voltages drop below specification. The power supply shuts down all voltages except the voltage to the service processor (5 volts continuous), which may be able to log the power loss event.
4. All DC voltages are lost, including 5 volts continuous.
5. Power is restored and the system reboots. The service processor logs the power on event.

The AC power may recover before any DC voltages are lost. In this case, the sequence is as follows:

1. AC power drops below the normal operating system range.
2. The power subsystem triggers the EPOW line. All DC voltages are still within specification.
3. AC power goes back within its normal operating range before any DC voltages drop below their specified levels. The EPOW sig...