1. Electrical equipment & supplies
  2. Power conditioning
  3. MURATA POWER SOLUTIONS
  4. MVAC 400-12AFD
  5. 2 Pages

Murata Power Solutions MVAC 400-12AFD, 250-12AFD, 400-24AFD, 250-24AFD, 400-48AFD, 250-48AFD Power Supply Application Note

Murata Power Solutions MVAC 400-12AFD, 250-12AFD, 400-24AFD, 250-24AFD, 400-48AFD, 250-48AFD Power Supply Application Note
Add to My manuals

MVAC 400-12AFD, MVAC 250-12AFD, MVAC 400-24AFD, MVAC 250-24AFD, MVAC 400-48AFD, MVAC 250-48AFD are power supplies that can be used in parallel. For the full-power main output, using FETs for low voltage drop. For the lower current fan (V2) and auxiliary (V3) outputs, ORing is most easily implemented with diodes rated to handle the reverse voltage, the power required by reverse voltage and diode leakage current at maximum temperature, and the forward current.

advertisement

Assistant Bot

Need help? Our chatbot has already read the manual and is ready to assist you. Feel free to ask any questions about the device, but providing details will make the conversation more productive.

MVAC Series Power Supplies - Application Note | Manualzz

External ORing FET Reference Circuit

MVAC Series

DESCRIPTION

ORing isolation is not required to achieve sharing of current between paralleled power supplies, but may be desired for redundancy in case of a power supply fault. The reference design in the schematic below shows how it may be implemented for the full-power main output, using FETs for low voltage drop. For the lower current fan (V2) and auxiliary (V3) outputs, ORing is most easily implemented with diodes rated to handle the reverse voltage, the power required by reverse voltage and diode leakage current at maximum temperature, and the forward current.

Paralleled fan (V2) outputs must be limited to 12W total, paralleled Aux (V3) outputs must be limited to 10W total. If the Aux (V3) outputs are to be connected in parallel, ORing devices must be used to guarantee start-up of both units.

Customers are invited to contact a Murata Electronics FAE with any questions.

SCHEMATIC

+Remote Sense

J3 pin 5

J2 pins 1-6

+DC out

Q1

+12V bus

Q2

MVAC #1

J2 pins 7-12

J3 pin 6

-Remote Sense

Q3

C3 as needed

Dotted lines:

Optional remote sense connections.

Remote sense lines are attached at the desired regulation point.

IN

Gate

U1

OUT

LTC4357

GND

Vdd

R1

100R

C1

0.1µF

DC out return

J3 pin 5

+Remote Sense

+DC out

J2 pins 1-6

MVAC #2

J2 pins 7-12

J3 pin 6

-Remote Sense

Q4

Q5

Q6

IN

Gate

U2

OUT

LTC4357

GND

Vdd

R2

100R

C2

0.1µF

www.murata-ps.com/support

ACAN-42.A01 Page 1 of 2

External ORing FET Reference Circuit

MVAC Series

BILL OF MATERIALS

ORing Circuit Suggested Parts List:

U1,2

Q1-6

R1,2

C1,2

C3

MVAC400-12AFD or

MVAC250-12AFD

LTC4357

RJK0329DPB-01

100 Ohms

0.1uF, 25V

As Required

MVAC400-24AFD or

MVAC250-24AFD

LTC4357

HAT2139H

100 Ohms

0.1uF, 50V

As Required

MVAC400-48AFD or

MVAC250-48AFD

LTC4357

HAT2201R

100 Ohms

0.1uF, 100V

As Required

Vendor

Linear Technology

Renesas

Murata

Notes:

For 12V applications, logic level power MOSFETs must be used. Fewer parallel FETs can be used depending on airflow, allowable operating temperature, and actual worst case loading conditions. For additional design information, simulation tools, and application notes, please go to: www.linear.com/product/LTC4357

Murata Power Solutions, Inc.

11 Cabot Boulevard, Mansfield, MA 02048-1151 U.S.A.

ISO 9001 and 14001 REGISTERED

www.murata-ps.com/support

This product is subject to the following operating requirements and the Life and Safety Critical Application Sales Policy :

Refer to: http://www.murata-ps.com/requirements/

Murata Power Solutions, Inc. makes no representation that the use of its products in the circuits described herein, or the use of other technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein do not imply the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifications are subject to change without notice. © 2012 Murata Power Solutions, Inc.

ACAN-42.A01 Page 2 of 2

advertisement

Key Features

  • ORing isolation
  • Redundancy in case of a power supply fault
  • Low voltage drop
  • Paralleled power supplies
  • Limited total output power
  • Start-up of both units
  • Remote sense
  • FETs for low voltage drop
  • Diodes rated to handle the reverse voltage
  • Maximum temperature

Frequently Answers and Questions

What is ORing isolation?
ORing isolation is a technique used to ensure that multiple power supplies can be connected in parallel and operate reliably even if one of the supplies fails. It is achieved by using diodes or FETs to effectively “OR” the outputs of the power supplies together, so that the load is always powered by at least one supply.
Why is ORing isolation needed for paralleled power supplies?
ORing isolation is not strictly required to achieve current sharing between paralleled power supplies, but it provides redundancy in case of a power supply fault. Without ORing, if one power supply fails, the load will lose power. With ORing, the other supplies will continue to provide power to the load, ensuring uninterrupted operation.
What are the limitations of ORing with diodes?
Diodes have a forward voltage drop, which can affect the efficiency of the system, especially at lower voltages. They also have leakage current, which can be significant at higher temperatures. Diodes are generally only suitable for ORing lower power outputs, such as fans and auxiliary circuits.
What are the advantages of using FETs for ORing?
FETs have a much lower voltage drop than diodes, making them more efficient for high-power outputs. They also have very low leakage currents. However, FETs are more complex to implement and require additional circuitry, such as gate drivers.
How do I choose the right FETs for ORing?
The choice of FETs depends on the power level, voltage, and current requirements of the application. Logic level power MOSFETs are recommended for 12V applications. For higher voltages, higher voltage MOSFETs must be used. The number of parallel FETs needed depends on the airflow, allowable operating temperature, and worst-case loading conditions.
Download PDF

advertisement