Small diameter electrolytic capacitors in power supplies

There has been a great deal of emphasis recently on power supply electrolytic capacitor life. No more apparent than with the launch of several new products, like TDK-Lambda’s ZMS100 series to the market, where life-time is stated as a major competitive differentiator. Many customers recognise e-cap life-time as a key reliability factor and will ask for capacitor temperatures and calculated lifetimes before they even test a sample.

Many engineers, both customers and power supply designers alike, focus on the larger sized capacitors. In particularly, the “bulk” capacitor that provides the hold-up energy and the output capacitors that reduce the output ripple and improve transient load response. Unfortunately, the smaller capacitors that are associated with the housekeeping circuit and start up circuitry are often overlooked and considered relatively unimportant.

Looking at one of the major capacitor manufacturer’s datasheets for a long-life capacitor, it can be seen that for a 10mm diameter capacitor, the life is stated at 10,000 hours. The life for a 6.3mm diameter capacitor at 105oC though is only 6,000 hours. If run at 24 hours a day, 365 days a year, that equates to only 250 days. At that point the datasheet says the capacitance can be 25% less. After a couple of years that will be significantly reduced further, but unless the power supply suffers a loss of input power, it might go un-noticed.

Electrolytic capacitors are also notoriously sensitive to temperature. A change in ambient temperature from 40 to 0oC can reduce the capacitance value by up to 10% and double the impedance.

A recent incident in the home of one of our technical marketing team members revealed the effect of this combination. His central heating system was being upgraded and the 7-year old gas boiler had been turned off for 2 days. When the boiler was switched on, it failed to start. The heating technician was baffled and an additional cost of £200-300 was mentioned, along with a two day delay. As it had been snowing, our team member was reluctant to wait for spare parts and asked to see the boiler. Examining the power supply, he applied heat to the small diameter electrolytic capacitors and 20 seconds later the boiler started up.
When questioned how he knew what the fault was by the suitably impressed technician, he answered “poor power supply design; aged electrolytic capacitors and freezing temperatures!”

During the initial development stage of the ZMS100 series of 100W open frame power supplies, TDK-Lambda received similar customer feedback of large scale field failures with a competitor product. The Engineering team designed the start-up circuitry using a longer-life ceramic capacitor in place of commonly used electrolytic. Ceramic capacitors do not contain liquid electrolyte which over time will dry out and cause a loss of capacitance and an increase in ESR. This known failure mechanism can lead to failures and power supply start-up problems.


CIGS Photovoltaic Test Chamber

CIGS (Copper Indium Gallium Selenide) solar cells are suitable for thin film or flexible application, and require additional testing for exposure to continuous light. Several power levels of the Genesys™ programmable supplies supplies have been designed in by a manufacturer of test chambers, ranging from 3,000W all the way up to 15,000W. All Genesys™ products share the same features and programming interfaces, which along with technical support and a strong customer relationship, secured the opportunity.


75W triple output AC-DC power supplies – CUT75 series

TDK Corporation introduces the TDK-Lambda CUT75 series of 75W PCB type, triple output AC-DC power supplies – 64% smaller, lighter weight and more efficient than the earlier generation JWT75 series. With an efficiency of up to 85%, the CUT75 series reinforces TDK-Lambda‘s competitive advantage in the medical and general industrial equipment markets.

Operating from a universal input of 85 to 265Vac, the CUT75 is offered as two different standard models. The CUT75-522 model offers 5V and ±12V with independent converter, ensuring good regulation and no minimum load. By connecting the +12V and -12V output in series, this model can be used as a 5V, 24V dual output power supply. Similarly, the CUT75-5FF model offers +5V and ±15V and can be used as a dual 5V, 30V unit.

Convection cooled, the CUT75 series features a wide operating temperature range of -20 to +70°C. Standard features include over current protection and over voltage protection. Options include CUT75 models with cover (/A), baseplate (/B) and terminal block (/T).

The CUT75 series from TDK-Lambda meets the conducted and radiated EMC requirements of EN55011/EN55022-B, FCC-B and VCCI-B, as well as IEC61000-4-2, -3, -4, -5, -6, -8, -11 immunity and safety approvals to EN/UL/CSA60950-1. It is also approved for medical applications by IEC60601-1 3rd Edition (2xMOOP) and designed to meet ANSI/AAMI ES60601-1. Delivered with TDK-Lambda’s 3-year warranty, the CUT75 series carries the CE mark, according to the RoHS and LV (low voltage) Directives.

For more information about the CUT75 series, please call TDK-Lambda directly on +44 (0)1271 856600 or visit the TDK-Lambda website at:


Clinical Chemistry System

Large clinical chemistry systems are used to enhance laboratory productivity by accurately analysing tens of thousands of samples daily, with a requirement for minimal machine maintenance. TDK- Lambda’s quality and strong local technical support were the reasons for the selection of the TDK-Lambda SWS1000L 1000W medically certified power supply for this application.


How is service life maximised on ZMS100 power supplies?

Electrolytic capacitors used in power supplies are a key wear-out item affecting service life. In this video TDK-Lambda demonstrates how the design of the ZMS100 series differentiates it from competing products.


To read more about the full range of Medical power supplies, click here to head to the product page:


Broadcasting Subsystems

Equipment for broadcasting often requires low acoustic noise. The low speed fan in the HWS600 series of 600W power supplies is quiet, unlike many noisy, high speed fan cooled power supplies. The designers configured their subsystem such that the HWS could operate in both single and parallel operation.


2500W Bi-directional DC-DC Converter For Energy Storage and Recycling

TDK Corporation announces the introduction of TDK-Lambda’s EZA2500-32048 bi-directional converter suitable for energy storage systems with rechargeable batteries. This 2500W digitally controlled, compact 1U power supply can automatically change conversion direction from high voltage dc sources, powered by solar or wind, to 48Vdc batteries and vice versa.

In addition to small to medium sized energy storage, applications also include lithium-ion battery testing as well as the utilisation of regenerated energy from robots, cranes, autonomous ground vehicles and lifts. For example, the EZA2500 can replace the large power resistors currently used for lift braking and instead use that previously dissipated energy to charge batteries. That storage can then be used to either provide peak power for high torque demands or as battery back-up for power cuts.

The EZA2500 operates from, or supplies, either a 36 to 60V or 300 to 380V dc voltage with maximum currents of +/-52A or +/-7.8A respectively. The output voltage and current can be programmed and monitored using the RS-485 communications port. For larger systems, multiple units can be operated in parallel by setting the unit to “droop mode” current share via the RS-485 interface. A variety of alarm signals are also accessible, as well as remote on/off and under/over voltage functions. The EZA2500 will operate at full load in an ambient temperature of -10 to +40oC.

Internally, the twin DC-DC converter design enables continuous transitional switching between charge and discharge states to maintain the stability of the bus voltage. Operating efficiencies of up to 94% are achieved with the use of full digital control. The converters are isolated – 3kVac from the high voltage (grid) to low voltage (battery) input/outputs, 2kVac from grid to ground and 500Vac from battery to ground.

The dimensions for the EZA2500 are 43.6mm (1U) high, 423mm wide and 400mm deep. Certifications include UL/CSA 60950-1, EN 60950-1 and carries the CE mark for the LVD and RoHS2. The EZA2500 is backed by a five-year warranty.


How does improved efficiency facilitate integration of PFE-SA power modules?

A reduction in a power supply’s dissipated power can have significant benefits to the required airflow, audible noise, operating temperature and heatsink size explains TDK-Lambda in this video, comparing the new PFE-SA AC-DC power module with the previous generation model.

PFE-SA Series

To read more about the full range of Harsh Environment power supplies, click here to head to the product page:


Broadband Amplifier

Manufacturers of broadband amplifiers need compact power supplies to keep their equipment small to avoid occupying valuable space either on the bench or in a rack. The high power density of TDK-Lambda’s HFE1600-48 was the primary reason for being chosen to power a new series of amplifiers – the HFE units measuring just 1U high and 300mm in length.


RX/TX Communications Equipment

Equipment used in transmitting and receiving data is often required to run without fan cooling to prolong field life, particularly in remote installations. TDK-Lambda’s PFE300SA-28 300W AC-DC power module was found to be well suited for a supplier of RX/TX equipment as it can be either cold-plate mounted or fitted with a heatsink, operating with baseplate temperatures of up to 100oC.