Limit inrush current in low-to medium-power applications

摘要

When switched-mode power supplies, including those for notebook computers, turn on, the bulk capacitor of the uncontrolled rectifier is completely discharged. This can result in a large charging current for a high instantaneous line voltage because the discharged capacitor temporarily short-cir-rncuits the power supply s diode bridge.rnWith a large bulk capacitor, the current spike can trigger the mains breaker or even destroy rectifier diodes. Capacitor and line ESRs (equivalent series resistances) and inductances help to reduce the initial spike. Even so, current peak can reach tens of amperes. Thernrectifier-diode selection must account for this nonrepetitive spike. An initial spike also affects the lifetime of the bulk capacitor. The circuit in Figure 1 lets you avoid the large initial spike.