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# Current Sharing Between Parallel Power Supplies Using Temperature Information.

IP.com Disclosure Number: IPCOM000014306D
Original Publication Date: 2000-Dec-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 3 page(s) / 57K

IBM

## Abstract

R1 R1 VOUT Current Share wire

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 63% of the total text.

Page 1 of 3

Current Sharing Between Parallel Power Supplies Using Temperature Information.

R1

R1

VOUT

Current Share wire

VCC

VCC

R3 R6

4

VCC

4

VCC

VCC

4

7

4

R4

2

3

2

3

-

+

D1

D1

R7

R6

R7

4

7

U5

U5

2

3

2

3

6

6

-

+

-

6

R4

6

2

U1

U1

U2

U2

6

6

77 + 3VCC

7

7 + 37VCC

7

VCC

4

U4

2

27VREF

3

2

U3

3

2

-

+

6

6

1

1

+

-

6

6

3

2

3

R8

R5

R8

Error Signal to control Output Voltage

Power Supply 1

Current Share wire

VCC

4

R3

-

+

-

+

-

2

742VREF

-

+

+

-

U4

U3

Error Signal to control Output Voltage

Power Supply 2

Figure 1. A current share method between two power supplies. The prior art of current shaing between two power supplies in parallel is shown in figure
1. Here R1 is the precise current sense resistor. Suppose VOUT from power supply 1 is higher than power supply 2. The current provided by power supply 1 will develop a voltage across R1. This voltage will be amplified by error amplifier U1 and applied to U2 and U3. U2 acts as a buffer whose output node acts as a current share node. As the output of the power supply 2 is assumed to be low, the output of U1 applied to the input of U3 is lower than the voltage applied to U3 of PS2, the output of U3 will go high and force a current through Q. This will create an additional offset voltage that will be sufficient to increase the voltage to a level that both the power supplies in parallel will start sharing the load current.

This method requires a precise value of current sensing resistor R1, a low offset operational amplifier and a feedback controlled amplifier U3.

1

Page 2 of 3

D2

Heat Sink

Temperature Share Wire

7 + 3VCC

Temp Sensor

VCC

R6

R5

Q1

VCC

4

2

3

D1

-

+

6

4

7

R7

U5

2

-

U2

6

VCC

Power Supply 1

4

U4

2

27VREF

-

+

6

1

3

2

U3

+

-

6

3

7

R8

Error Signal to control Output Voltage

VOUT

D2

Heat Sink

Temperature Share Wire

VCC

Temp Sensor

VCC

4

7

4

2

3

-

+

D1

R6

R7

6

2

-

U2

6

+ 37VCC

7

VCC

R5

R8

U5

742VREF

6 - 3261Power Supply 2

3

2

+

-

Q1

+

U4

U3

Error Signal to control Output Voltage

Figure 2 shows the circuit diagram wh...