Power Designer

Power Designer
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#125: Improve Power Converter Reliability Using Hiccup-Mode Current Limiting

Overview: Switch-mode power supplies employ various schemes to protect themselves, and ideally the load, in overload conditions. Depending on whether the power converter automatically recovers and reverts back to normal operation once the overload condition is removed, overload protection schemes can be broadly classified into two categories: non-recoverable protection schemes (fuses, circuit breakers, overload shutdowns) and self-recoverable protection schemes (cycle-by-cycle current limiting and hiccup mode). The choice of protection scheme depends on the cost, complexity, and applicable safety standards. Non-recoverable schemes, such as the use of fuses, are popular in front-end off-line power conversion, and self-recoverable protection schemes are used typically in back-end DC-DC converters. Oftentimes, both of these types of schemes are implemented together to provide additional redundancy. Non-recoverable schemes are outside the purview of this article. Among self-recoverable protection schemes, cycle-by-cycle current limiting delivers maximum load current into the short circuit, thereby creating a thermal management problem. This complicates component and heat sink selection and if the components are not oversized, it can reduce the reliability of the system. Hiccup-mode protection solves the thermal management dilemma, and therefore improves system reliability and simplifies component selection.

Power Designer
Published every other month, Power Designer's feature articles cover power design techniques.

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