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Selection Method of External Bulk Capacitor for VBUS
C9 & C10 capacitor values are determined by
intermediate bus voltage ripple, ripple current, and
hold-up time. Select a capacitor value such that VBUS
voltage ripple does not exceed 15Vp-p.
Note: When the ambient temperature is ≤ -20 ºC, the
ripple voltage of C9 & C10 will increase due to ESR
characteristics. Therefore, verify above characteristics
by actual evaluation in the circuit.
For output hold-up time, refer to separate document
"PFH500
Series
appropriate capacitor. It is recommended that actual
verification testing is performed.
For allowable capacitor ripple current value, refer to
Fig. 5-2. Use of a capacitor with higher ripple current
rating is highly recommended.
The bulk capacitor value affects the module's output
hold-up time, dynamic line transient response, and
dynamic load transient response characteristics.
5.8
C11 (470pF); C12 (470pF)
Connect Y class ceramic or film capacitors as EMI noise countermeasure to reduce high frequency noise.
Capacitors with high voltage rating are typically required since high test voltages are often applied across these capacitors
(between the output terminals and the module metal case) during Hipot testing. The metal case is connected to earth
ground or equipment frame ground (application dependent). Connect C11 as close to Vo(+) terminal as possible, and C12
as close to Vo(-) terminal as possible.
5.9
C13 (0.1µF, 50V~100V Ceramic Capacitor)
Add this output ceramic capacitor approximately 50 mm away from the PFH Series module output terminals to help reduce
high frequency output noise.
5.10 C14 (40µF, 50V ~ 100V or (4) 10µF Ceramic capacitors in parallel)
Add this output ceramic capacitor approximately 50 mm away from the PFH Series module output terminals to help reduce
the high frequency output ripple noise, and to improve the load transient response.
REV 2.8 (March 30, 2020)
Evaluation
Data",
and
Verification testing should be performed over the entire
operating temperature range.
2000
1600
1200
use
800
400
0
0
100
Fig. 5-2 Allowable Ripple Current Value
TDK-Lambda
PFH500-SERIES
INSTRUCTION MANUAL
115VAC
230VAC
200
300
400
Output Power (W)
500
12
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