Understanding the real benefits of flexibility and configurability in power systems design

For electronics product designs with a large (>100W) power requirement, the method for choosing a power supply type appears straightforward.



The design team has three basic options:



- A standard part with fixed specifications. Standard parts are available in a limited range of specifications supporting the inputs and outputs which are most commonly specified in circuit designs.



- A full custom design to the user’s exact specification for power, number of outputs, form factor, environmental protection and any other required parameter.



- Configurable or programmable power supplies. A configurable power supply unit can support a wide range of power specifications, and a varying number of power outputs, through the selection of

appropriate modules housed in a common base unit. A programmable power supply gives the user the flexibility to fine-tune the input and output specifications of any given module.



Conventional thinking about power supply specification applies a hierarchy to the decision flow. At the top of the hierarchy is the standard part. It is commonly assumed that, if a design can use a standard part, it should do. A standard part, so the traditional thinking goes, provides the optimal combination of cost, size and efficiency for any standard input/output combination.



This is because the standard part is optimized for exactly one input/output specification; and because it is produced in high volumes for multiple customers, so benefits from economies of scale.



If standard parts do not provide the combination of outputs that a power design requires, however, next in the conventional hierarchy is the full custom part: this provides the design team with exactly the specifications it requires, in a design optimized for performance, low materials cost, efficiency or other parameters as dictated by the customer.



But a full custom solution is not appropriate for some product development programs. Most commonly, this is because the lifetime value of the program is not large enough to justify incurring a custom solution’s non-recurring engineering costs (NREs), or because it will take too long to get to market with a custom design.



Traditionally, then, the decision flow only reaches configurable power supplies at the end, once it is clear that neither a standard part nor a custom power supply unit is appropriate. In other words, a configurable power supply is in effect treated as the designer’s last resort.



This paper argues that, in fact, configurable power supplies should be the first option that most program managers and power supply designers should consider.



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