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83-493-001 Rev. K
20
5.7 LONG CHARGE TIME WITH POWER FACTOR CORRECTED (PFC) UNITS
It is advised that you consult the factory if this type of operation is required.
On supplies with active Power Factor Correction there is a limit to the length of the
charge time. With all capacitor charging supplies, the peak output power capability is
twice the joule per second rating. At pulse rates greater than approximately 20Hz, the
internal filter capacitors can average the power drawn from the power factor correcting
circuit. At lower pulse rates, the output stage will attempt to draw twice the rated average
power fro the PFC circuit. The internal current limit if the PFC circuit will be activated and
the supply will shut down. To avoid this type of fault condition, the output power can be
reduced by providing an inhibit pulse of fixed or variable duty cycle to keep the average
output within the PFC rating (See Figure 5.4).
Figure 5-4 Long Charge Time Operation