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Inrush Current Limiter

IP.com Disclosure Number: IPCOM000114822D
Publication Date: 2005-Mar-29
Document File: 2 page(s) / 52K

Publishing Venue

The IP.com Prior Art Database

Related People

John Pigott: AUTHOR

Abstract

A hotswap controller is used to limit the inrush current from a power supply to the filter capacitor in the load, when the printed circuit board containing the load is plugged in. This protects the contacts on the card connectors, and delays startup of the load until the power supply is stable. Generally, the hotswap switch is in series with the complete supply to the load. This new configuration places the hotswap switch in series only with the input filter capacitor of the load, providing improvements in efficiency by reducing power dissipation.

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Inrush Current Limiter

John Pigott

Abstract

A hotswap controller is used to limit the inrush current from a power supply to the filter capacitor in the load, when the printed circuit board containing the load is plugged in. This protects the contacts on the card connectors, and delays startup of the load until the power supply is stable. Generally, the hotswap switch is in series with the complete supply to the load. This new configuration places the hotswap switch in series only with the input filter capacitor of the load, providing improvements in efficiency by reducing power dissipation.

A hotswap circuit consists of a hotswap controller and a power switch. In the usual configuration, the hotswap controller is used to switch power to a load in a controlled manner. This control usually limits the inrush current allowed, thereby protecting the systems from damage caused by large transient currents in the connectors as contact is initially made. Most loads have a large input capacitor, and the initial charging of this capacitor could require a large transient current.

In existing configurations, the hotswap switch is placed in series with the complete load, which includes both the load’s input filter capacitor, and the remaining load circuitry. Thus, both the DC and the AC components of the load current flow through the hotswap, unnecessarily increasing the power dissipation.


Fig. 1. Existing Configuration - All load current flows through hotswap switch

By configuring the...