Bleed Resistors – Maintaining a Charge
Bleed resistors are placed in parallel with a power supply’s load and are used to discharge the smoothing capacitors in linear AC-DC converters and also the reservoir capacitors utilized by DC-DC converters. These capacitors can retain charge long after a supply is turned off, presenting a shock hazard to users accessing the supply. Clearly the bleed resistor’s value should be calculated to be high enough not to consume significant power when the supply is operating normally but low enough to discharge the unit relatively quickly when the supply is switched off.
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