Most people involved with electronic products, like power supply units, are aware of the general principles of product ‘reliability’ but few use this information to help them with crucial decision making. This could be for military power supply products, medical power supply products or telecomes supply products. Should we be undertaking periodic power supply maintenance? Should we be continuing with our power supply repair policy? Or should we be carrying out some sort of phased product replacement? A better understanding of product reliability and good working data can help make these decisions much easier.

The failure rate(λ) of a product plotted against time gives a graph commonly known as a ‘bath tub curve’, a simple example is shown below. The curve breaks down into three regions:
Region A – Infant Mortality. The new product shows random failures that can be down to below standard components and poor workmanship. This region is often minimised from the users perspective, by the manufacturer carrying out in-house ‘burn in’ tests. These usually consists of running the product under operating conditions, sometimes at elevated temperatures, so that the infant mortality failures occur at the manufactuers plant and are dealt with before the user sees the product.

Region B – Useful Life. During this time the product failure rate is pretty constant and with good products is very low.

Region C – End of Life. This is when the failure rate begins to accelerate rapidly from the previous constant level and is due to parts reaching their design life limits. With power supply units this is typically electrolytic capacitors drying out, mechanical items like fans and switches failing, as well as increasing failures in other electronic parts.

Gathering data on product failures helps to identify which part of the curve your product is operating in and will enable you to increase the useful life by carrying out some effective preventative maintenance. A quality power supply repair & design company like QES Ltd will provide this information to its customers on request and will work with them to develop appropriate preventative measures.

On every repair job carried out by QES the parts failing are recorded on computer records and these can be viewed by customer & product to provide a failure history that is specific to the customer and the product application. If, for example, the number of failures on a cooling fan start to show a significant increase it may be sensible for the user to include an item within their planned power supply maintenance program for the fan to be changed. Again a quality company like QES will help develop this type of program including sourcing and stocking the appropriate power supply parts to carry it out. This approach can ‘rescue’ a power supply product from the start of the End of Life region and return it to the Useful Life region of the bath tub curve, giving the user continuing low failure rates for very little cost.

The data gained from the information collected by QES can also help you decide when this extended life approach is not appropriate, or has run its course. When the data shows an increase in difficult to identify problems like dry joints caused by solder hardening, or failures in obsolete semi-conductors causing a reduction in the spares pool, then it is time to consider a product replacement program. Again QES are happy to work with you in identifying or producing a suitable replacement product that will meet the electrical and mechanical properties of the original. They have successfully produced fit, form and function replacements for many standard and custom power supplies used in many applications.

Looking at, and recording the reasons for product failures, is crucial to making the right decisions in order to keep the power supply product reliability high and the failure rates low. QES operate in a way that means they can offer a very effective service to customers in carrying out all phases of the data collection. They can then work with them to make the most appopriate decisions and carry out the necessary work on their behalf.

Start collecting product reliability data and improve perfmormance of your company today. Contact QES to find out how this can be done.

In the design cycle of electronics products it is very normal for the power supply to evolve beyond its initial specification in order that the product can fulfil its full potential. This frequently means that by the time the product design is fixed the original ‘standard’ power supply has turned into a requirement for a custom unit that will provide all of the electrical facilities needed and fit into the original space allocated.

Similarly in many cases the power supplies used within industrial and commercial electronics systems become obsolete whilst the systems themselves are still in widespread use. Unless the systems manufacturer or user bought lots of spares up front then this inevitably presents maintainers with a problem. What do we do about the obsolete power supplies? Finding a replacement at this stage of the systems life cycle will almost inevitably mean that a custom power supply is required.

In both of these cases the requirement for a custom power supply can be dealt with in two main ways, using the in house design capability or going to a specialist third party. The in house option may sound good but unless you have the right design capability it can have big cost and timescale impacts on your project. Going to a third party specialist, like QES, will most frequently be the better option. They have the experience and specialist skills to enable them to select the best custom method for your design and to then bring this to completion at a fixed cost within agreed timescales.

A custom power supply can be many things

- Simple changes to a standard product – like changing connectors or modifying covers in some way.

- Adding extra circuits to a standard product – additional monitoring, start up and shut down circuits and others.

- Creating a product of a special shape – possibly using a semi-standard product within new packaging.

- Creating a new unique product – possibly using standard building block modules or circuits from our existing range of custom products.

QES is experienced in using all of these techniques and more to give customers requiring custom designs what they need, at the right price on the right date.

The design process is exactly the same as that we would use for any of our power supply design work and is defined in our ISO9001 approved quality system. If your timescale permits a ‘first off’ sample will be provided to check that all of the mechanical and electrical aspects match the real system requirements and if there are any problems we work with you to resolve them before supplying further units.

Take the easy way to your custom power supply power supply, speak to QES.

Krish for power supply repairs uk QES Ltd

This design project was the result of a customer with a problem. A standard constant voltage output psu had been designed into equipment with the object of using additional electronics to provide a programmable constant current source. The additional electronics didn’t work well and produced too much heat.
We took the original AC input 24V DC output 150W unit and by adding a single small additional circuit board converted it to a programmable constant current output. 0 to 7V DC analogue programming voltage producing 0 to 7A of output current. This was possible because of our detailed knowledge of the method of operation and control used in the original design.
We wrote the product specification and agreed it with the customer, carried out full proving tests and supplied a development unit. The unit is CE marked.

A copy of our Outline Product Specification Sheet is available as a download from this page.

Some years ago we were asked if we were interested in designing a small fixed frequency sine wave generator operating from 26V DC and supplying about 10VA of power. The customer had previously approached many companies who were associated with this type of design but none were interested because of quantities required, very low power rating and low target pricing. We said yes, even though it wasn’t our normal field, and then set about the task on an innovative basis using circuit elements that we understood well. Our understanding of voltage regulators, power protection circuits, transformers and power amplifiers all helped us to produce a simple cost effective design that has now been in service for many years and has outstanding reliability.

A telecoms customer asked us to review a particular power supply it was using and suggest what might be done to improve its reliability record. The original product manufacturer still existed but was not interested in carrying out this work.

We reviewed the design, failure record and use logistics of the product and provided the customer a report of our findings including a number of recommendations for improving its reliability record.

These recommendations were diverse ranging from replacing certain electronic components with better devices to changing the method of shipment between his various sites. These recommendations were implemented and the reliability performance of the units improved dramatically.

Maybe you have a similar problem we can look at?

Various UK product distribution companies either commission or bring in product to the UK based on a specification agreed with their supplier. This specification is also used in the promotional literature for the product. When sample units arrive in the UK the distributor needs to know if they conform to the agreed specification and if they have limited or no engineering support this can be difficult. Which, as far as power supplies are concerned is where we come in. We will take the product and carry out full electrical and temperature testing against the specification and produce a report with our findings; this is independent and confidential.

We have now provided this service in respect of five separate power products.

You may have other reasons for requiring independent testing.

One of our customers, who is a large power supply manufacturer, discovered that a fault existed on one of its products supplied by an overseas factory. All existing inventory of the product within the UK required a modification to correct the fault. The customer provided us with the details and then liaising with them, the warehouse inventory was cycled though our workshop where the modification was carried out and the product tested and relabelled. This meant that the problem was solved without any disturbance to the customers UK operation and without the cost of shipping the product back to their overseas factory.

The original power supply was obsolete and the company supporting the user base, in specialised printing equipment, no longer had sufficient stock to provide effective support. They asked us to help.
We designed, developed and manufactured a replacement based on the original product specification, sample product and testing within the host equipment. Our very cost effective solution employs an off the shelf unit modified to provide the constant current output required and comply with the necessary electrical and mechanical interfaces.

An infrastructure company using various electronic sign systems containing obsolete Coutant Lambda ML150 power supplies contacted us about obtaining a fit, form and function replacement to augment their present stock holding. We designed and manufactured a replacement using our own mechanical design but matching the overall size, fixing positions and connection layout of the ML150. Into this mechanical shell we fitted a number of off the shelf and in house modules to complete the electrical design.

This product is now in full use with the customer alongside original units.

A copy of our outline Product Specification sheet is available as a download from this page.

A single sided pcb containing around 70 component parts on a surface area of approximately 30 x 60 mm. This piece was designed as a replacement for an existing circuit board. It employs the original circuit updated to accommodate new parts to replace obsolete and outdated parts.

The new board has been successfully used in support of product repairs for the last 7 years.

This unit was designed to a full customer specification for use within a system now deployed on the new UK type 45 Destroyers. The design & development included full qualification testing (EMC, Temperature, Shock & vibration), reliability analysis to MIL-HDBK-217 and CE Marking.
It is powered from a 3 phase 115V 60Hz input and produces 48V DC at 2.5kW It is constructed on a modular basis and provides an N+1 redundancy feature to enhance reliability.

Derivations of this unit would be well suited to high quality telecom or other distributed power system requiring a 48V DC supply.

military power supply design

military power supply repair