PFS704 POWERINT [Power Integrations, Inc.], PFS704 Datasheet - Page 18

• Manufacturer Part Number: PFS704
• Description: High Power PFC Controller with Integrated High-Voltage MOSFET
• Manufacturer: POWERINT [Power Integrations, Inc.]

To minimize effect of trace impedance affecting regulation,
output feedback should be taken directly from the output
capacitor positive terminal. The upper end of the line-sense
resistors should be connected to the high frequency filter
capacitor connected at the output of the bridge rectifier.
As with any power supply design, all HiperPFS designs should
be verified on the bench to make sure that component
specifications are not exceeded under worst-case conditions.
The following minimum set of tests is strongly recommended:
1. Maximum drain voltage – verify that peak V
Rev. D 12/11
Quick Design Checklist
18
exceed 530 V at lowest input voltage and maximum overload
output power. Maximum overload output power occurs
when the output is overloaded to a level just above the
highest rated load or before the power supply output voltage
starts falling out of regulation. Additional external snubbers
should be used if this voltage is exceeded. In most designs,
addition of a ceramic capacitor in the range of 33 pF and
100 pF connected across the PFC output diode will reduce
the maximum drain-source voltage to a level below the BV
rating. When measuring drain-source voltage of the MOSFET,
a high voltage probe should be used. When the probe tip is
removed, a silver ring in the vicinity of the probe tip can be
seen. This ring is at ground potential and the best ground
connection point for making noise free measurements.
Wrapping stiff wire around the ground ring and then
connecting that ground wire into the circuit with the shortest
possible wire length, and connecting the probe tip to the
point being measured, ensures error free measurement.
PFS704-729EG
DS
does not
DSS
2. Maximum drain current – at maximum ambient temperature,
3. Thermal check – at maximum output power, minimum input
4. Input PF should improve with load, if performance is found to
minimum input voltage and maximum output load, verify
drain current waveforms at start-up for any signs of inductor
saturation and excessive leading edge current spikes.
HiperPFS has a leading edge blanking time of 220 ns to
prevent premature termination of the ON-cycle. Verify that
the leading edge current spike is below the allowed current
limit for the drain current waveform at the end of the 220 ns
blanking period. If a wire loop is inserted in series with the
drain, it forms a small stray inductance in series with the
drain. This stray inductance will add to the leading edge
voltage spike on the drain source waveform. The drain-
source voltage waveform should therefore never be measured
with this loop. An alternate measurement that can provide
drain current level and information regarding slope of the
inductor current can be obtained by monitoring the inductor
current instead. A wire loop can be added in series with the
PFC inductor connection that connects the inductor to the
input rectifier for the purpose of measurement.
voltage and maximum ambient temperature; verify that
temperature specifications are not exceeded for the HiperPFS,
PFC inductor, output diodes and output capacitors. Enough
thermal margin should be allowed for the part-to-part
variation of the R
sheet. A maximum package temperature of 100 °C is
recommended to allow for these variations.
progressively deteriorate with loading then that is a sign of
possible noise pickup by the VOLTAGE MONITOR pin circuit
or the feedback divider network and the compensation
circuit.
DS(ON)
of HiperPFS, as specified in the data
www.powerint.com