Variable Power Supply Output Voltage by Micro Processor Unit Upgrade Card
Original Publication Date: 1995-May-01
Included in the Prior Art Database: 2005-Mar-30
Narita, I: AUTHOR [+2]
Disclosed is a power supply which can change its output voltage associated with the installed Micro Processor Unit (MPU) card.
Variable Power Supply Output Voltage by Micro Processor
a power supply which can change its output voltage
associated with the installed Micro Processor Unit (MPU) card.
upgrade is very popular. When MPU card
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
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...