Wednesday, July 22, 2009

Operating Power Supplies in Series

Although some users are nervous about operating power supplies in series, it is common practice in the industry. The benefit is that voltages greater than 60V can be obtained using off-the-shelf products.

It is possible to connect several power supplies in series, but please read the precautionary notes below:
  • Connect back-biased diodes across the power supply terminals as shown below.
Rate these diodes at the same output current as the power supplies.

In the event both power supplies do not turn on at the same time, or if the load becomes a short circuit, then the diodes will protect the power supplies from any applied reverse voltage.

  • Do not exceed the output to ground/chassis voltage rating. Inside most power supplies are noise filter capacitors connected from the output to ground. It is possible to exceed the operating voltage of those capacitors, particularly when configuring several units in series.
  • Avoid using “fold-back style” current limited power supplies as these may lock up the power supply during initial switch on.

Tuesday, July 21, 2009

TDK-Lambda Packs 15W into 1 x 1 Inch DC-DC Converter

San Diego, CA – July 2009 – TDK-Lambda has added two new series to its already successful PX family of DC-DC converters. The fully-isolated PXA and PXB Series have a tiny 1 x 1 inch footprint and are designed for applications ranging from communications to factory automation equipment. They are available in open frame (PXA) and shielded metal case (PXB) versions.

The PXA Series offers single-output models with nominal inputs of 24V and 48VDC in 2:1 and wide 4:1 versions. The PXB Series offers both single and dual-output models with nominal inputs of 12VDC in a 2:1 version and inputs of 24V and 48VDC in 2:1 and wide 4:1 versions.

Available single-output voltages for the PXA and PXB series include 3.3V, 5V, 12V and 15VDC. In addition, the PXB series offers dual-output models that provide ± 5V, ± 12V and ± 15VDC outputs. Efficiency is up to 88%. Remote on/off and output adjustment (trim - single output models) features are standard, plus all models include overvoltage and overcurrent/short circuit protection. Operating temperature range is -40°C to +85°C.

The PXA is available in through-hole or SMD mounting formats and the PXB in a through-hole mounting format. All models are CE-Marked and are certified to UL/CSA/EN60950-1 safety standards as well as meeting the rigorous MIL-STD-810F thermal shock and vibration specifications.

The PXA and PXB series are available now and priced from $28.00 each in 500-unit quantities. For more information, please call TDK-Lambda directly at 1-800-LAMBDA-4 or visit the website at:

About TDK-Lambda:
TDK-Lambda has been a major provider of power solutions for over 60 years. The company designs and manufactures a wide range of AC-DC and DC-DC power products and EMI filters for Industrial, Medical, Telecom, Datacom and Test & Measurement applications. TDK-Lambda is a subsidiary of the TDK Corporation (TSE, LSE: TDK), a leading global electronics company ( For more information, please call TDK-Lambda at 619-575-4400 or 1-800-LAMBDA-4 (toll free), or visit our website at:

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