High Frequency Power Converters
Computers and telecom equipment are steadily becoming more complex, providing ever higher levels of performance. Simultaneously, the selling price for this equipment is being driven ever lower by market competition. Integral to all of this equipment is a power conversion system which converts the incoming unregulated power from the utility, or other source, to the multiple regulated voltages required by the equipment. In present designs the power subsystem constitutes a significant part of the equipment cost and volume.
The development of a unique power converter(s) for each new system is a substantial cost item in the equipment development. Frequently the equipment will have a variety of configurations with differing power requirements. To save development cost only a single design is often used to cover a range of loads. The result is that many users have to pay for capability not needed in their particular configuration.
One means to reduce power subsystem over capacity and cost is to use a distributed power system where the power processing functions are distributed within the system and more power processing capacity is added as required when more capability is installed. A typical distributed system will have a central power processor which converts the raw input power into a regulated DC bus. The central power processor is relatively simple but it does provide for line isolation and the safety requirements for the system. The central processor may be modular to allow for power scaling as the loads change. Each board or group of boards within the equipment has a small power processor which converts the DC bus to the voltages required by that particular section of the equipment. In general these board level converters are quite simple and efficient. Frequently no DC isolation is required at the board level which further simplifies the converters.
The use of multiple small power converters allows a custom system to be designed using high volume, low cost, standardized modules. In a complex system there can be substantial cost savings. Board space is always at a premium and the localized power converters take up space. In general height is severely constrained and the power converter has a low profile geometry which tends to increase the board area required. In order to minimize the area required, the switching frequency (fs) of the converter is pushed as high as possible. The latest generation of systems [1] use converters with fs in the low MHz.
In addition to minimizing board area there are other requirements placed on these converters. [2] The components must be small enough for automated insertion and be low cost. All of this has to be achieved without seriously reducing conversion efficiency. Poor efficiency would increase the size and cost of the input converter and create thermal problems within the unit.
Overall these “simple” converters represent a significant design challenge.
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Application note & Design Guide |
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Please see the document for details |
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English Chinese Chinese and English Japanese |
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Apr 1, 1994 |
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Rev.1.00 |
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AN9208 |
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687 KB |
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