Why is electrical power conversion so difficult?

Modern electronic integrated circuits, such as micro processors and memory chips, cannot work using the high voltage alternating current supplied from the mains wall socket. These devices need stable low voltage direct current to operate. Every item of electronic equipment needs a power converter to function.

A power converter (or so called power supply) takes the relatively high voltage alternating electrical current that comes from the mains socket and converts it into stable low voltage direct current that is required by all electronic devices. It also undertakes a number of other functions such as providing the critical safety barrier between the end user of any equipment and potentially lethal mains supply.

The design and integration of these essential power conversion devices into the end equipment they power involves many challenges and trade offs. The result is a highly fragmented set of requirements from the customers who themselves are constantly attempting to differentiate their equipment from their competitors.

 

Cost, Reliability and Size trade offs

The first set of trade offs is the classic cost, reliability and size triangle. It is quite possible to optimise any two of these parameters but doing so invariably comprises the third parameter. Making a highly reliable compact power converter is possible with leading edge components and complex electric circuits; but such a device will certainly not be the lowest cost.

Customers have different attitudes to the importance of these three parameters according their end application. Critical medical device manufacturers will clearly prioritise reliability before anything else and then size; cost is of lesser importance. Non-critical consumer products will prioritise cost and then size.

XP Power focus on powering critical systems in the Industrial, Healthcare and Technology sectors so its product portfolio is focused on ultra-high efficiency products which have very high reliability and are as compact as possible.

 

Design trade offs

A power converter has many parameters that have to be considered in the design process. These include:

  • Efficiency
  • Electrical noise (both conducted and radiated)
  • Size
  • Leakage current
  • Start up time
  • Output current and input current
  • Output voltage and input voltage
  • Susceptibility to input spikes, dips and surges
  • Degree of control of the output voltage

Optimising one of these parameters invariably involves compromising another so there are many trade offs to be considered.

The power converter is typically integrated into the customer's design. Integrating the power converter into the environment of the end application requires attention to safety standards, thermal management of the power converter, noise and waste heat from the converter affecting the end equipment and the noise and waste heat from the installation affecting the power converter itself. Attention must also be paid to international standards concerning conducted and radiated noise and susceptibility to radiated and conducted noise, dips and surges for the entire equipment.

For this reason there is often considerable engineering involvement in assisting a customer to successfully integrate the power converter into their system. This frequently results in modifications to the power converter to allow it to power the customer's system. This is part of the value proposition XP Power provides to its customers during the development of their products.