TDK-Lambda LC1202, Instruction Manual

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83494001 Rev H Page 17 of 27
5 APPLICATIONS
5.1 DETERMINING CAPACITOR CHARGE TIME
The LC1202 Series is rated at 13500 J/sec peak and 12000 J/sec average charge rate.
Although the measure of Joules/sec equates to Watts, it is more convenient when work-
ing with energy storage capacitors. The peak charge rate determines the capacitor
charge time. The average charge rate determines the total power delivered from the
power supply. It is possible to charge a capacitor at a rate of 13500 J/sec, but to dis-
charge it at a low rep rate amounting to only 100 J/sec.
VOLTAGE
TIME
Tc Tp
5.2 VOLTAGE REVERSAL (SEE ONLINE APP NOTE 517 FOR MORE DETAILS)
When the capacitor or PFN is discharged, a high peak current may flow out of the power
supply as a result of voltage reversal. This occurs in a system which is under damped in
order to clear the high voltage switch after each pulse. The average value of this peak
current added to the normal output current may exceed the rating of the HV diodes in
the power supply. This current can be measured with a current transformer as shown.
A series terminating resistor (or series inductor or clamp diode) must be added as
shown if the average value of the peak current exceeds 10% of the normal output cur-
rent.
Average Charge Rate =
1
2
C V
2
T
p
Peak Charge Rage =
1
2
C V
2
T
c