Pre-Regulator Design Protects High-Voltage Power Supplies From Phase Faults (Part Two)
by Jean-Paul Louvel, ON Semiconductor, Toulouse, France, How2Power Today, May 15 2015
Focus:
Power supplies for applications such as e-meters and high-power appliances designed to run from a three-phase supply must be able to withstand incorrect connection between phases that can cause very high voltages to appear at the input. One solution is the novel pre-regulator circuit introduced in part one of this article. Here in part two, the operation of the pre-regulator and its advantages are described in greater detail. The discussion covers the interconnection of the pre-regulator to a flyback SMPS, circuit protection features, bulk capacitance requirements, and the circuit’s impact on the efficiency of the overall power supply design. In addition, a detailed analysis of the pre-regulator’s cost benefits is presented with the cost of an SMPS employing the pre-regulator compared against an SMPS using a cascode-based solution. This analysis considers output power requirements, hold-up time requirements, and capacitor ratings for temperature and lifetime. Finally, the limitations of this pre-regulator approach are noted.
What you’ll learn:
- How to design fault tolerant switched-mode power supplies for e-meters and high-power appliances through the use of a 200-V pre-regulator circuit
- How to analyze the cost benefits of a novel pre-regulator circuit for protection of switched-mode power supplies for e-meters and high-power appliances
Notes:
Much of the material presented here and in part one was previously given in ON Semi’s application note AND9172. However, the detailed cost comparison is new and some concepts may be explained more clearly in this two-part article.
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