Browse Prior Art Database

Variable Power Supply Output Voltage by Micro Processor Unit Upgrade Card

IP.com Disclosure Number: IPCOM000115562D
Original Publication Date: 1995-May-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Narita, I: AUTHOR [+2]

Abstract

Disclosed is a power supply which can change its output voltage associated with the installed Micro Processor Unit (MPU) card.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 91% of the total text.

Variable Power Supply Output Voltage by Micro Processor Unit Upgrade
Card

      Disclosed is a power supply which can change its output voltage
associated with the installed Micro Processor Unit (MPU) card.

      Lately, MPU upgrade is very popular.  When MPU card is
upgraded, sometimes the required voltage for the MPU also changes.
In the past, the power supply card also have to be changed along with
the upgraded MPU card.  By virtue of this invention, the power supply
card can be used as is because it changes its output voltage for MPU.

      Fig. 1 shows the circuit of the invention.  There is a ID pin
in the MPU card and there is a switch (SW1) which is controlled by
the ID pin.  In the figure, the divided voltage by the resistance R1
and R2 is inputted into the regulator IC as the feedback signal of
the MPU VCC.  The feedback signal is compared with the Vref in the
regulator IC, and then the MPU VCC voltage is controlled.  Assume the
resistor and Vref value as follows:
  R1=32.8K, R2=20K, R3=51.25K, Vref=1.25V

If SW1 is OFF, MPU VCC is controlled to be 3.3V.  And if SW2 is ON,
MPU VCC is controlled to be 2.5V.  So, when the MPU requires 3.3V for
its VCC, ID pin should be open.  And when the MPU requires 2.5V for
its VCC, ID pin should be grounded.  In the above described instance
(Fig. 1), the power supply can supply just on two voltage level (3.3V
and 2.5V) alternatively.  However, by increasing the number of the ID
pins and the switches with...