Design Guide
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V 1.0
2018-06-06
XDPL8218 design guide
For high power factor flyback converter with constant voltage output
PCB layout guide
16
PCB layout guide
a)
Minimize the circumference of the following high-current/high-frequency loop with traces which are short
and wide (or with jumper wires which are short and thick).
Power switch loop formed by DC link filter capacitor C
DC,filter
, primary main winding
, flyback MOSFET
and CS resistor R
CS
.
Main output rectifier loop formed by secondary main winding, main output diode and main output
capacitor.
Auxiliary output rectifier loop formed by auxiliary winding, auxiliary output diode and auxiliary output
capacitor.
b)
Place each filter capacitor, V
CC
noise decoupling capacitor C
VCCdecouple
, ZCD pin filter capacitor C
ZCD
and FB pin
filter capacitor C
FB
near to its designated pin and the GND pin of the controller.
c)
Apply the following guide for star grounding.
Connect ground signal traces of C
VCCdecouple
, C
ZCD
, R
ZCD,2
, C
FB
, the controller GND pin and the optocoupler
emitter pin.
Connect V
CC
ground traces of the V
CC
capacitor C
VCC
and primary auxiliary winding.
Connect the C
HV
GND pin near to the ground pin of C
DC,filter
.
Connect the GND pin of each C
VCC
, C
VCCdecouple
, R
CS
and bridge rectifier separately to a single point near
C
DC,filter
.
d)
Ensure the high dv/dt traces from the MOSFET drain and GD pin are as far as possible from the FB pin and
its connected trace.
e)
Shield signal traces with ground traces or ground plane, which can help to reduce noise pick-up.
f)
Always ensure appropriate safety clearances between the HV and LV nets.
