TECHNICAL DATASHEET
LANC485.1W12
DESIGN CONSIDERATIONS:
Output Over Current Protection
When excessive output currents occur in the system, circuit protection is required on all power supplies.
Normally, overload current is maintained at approximately 150% of rated current for the LANCW12 single
output series.
Fold back-mode is a method of operation in a power supply whose purpose is to protect the power supply from
being damaged during an over-current fault condition. It also enables the power supply to operate normally when
the fault is removed.
One of the problems resulting from over current is that excessive heat may be generated in power devices;
especially MOSFET and Schottky diodes and the temperature of those devices may exceed their specified limits.
A protection mechanism has to be used to prevent those power devices from being damaged.
The operation of fold back is as follows. When the current sense circuit sees an over-current event, the output
voltage of the module will be decreased for low power dissipation and decrease the heat of the module.
Figure 2
Output Over Voltage Protection
The output over-voltage protection consists of an output Zener diode that monitors the voltage on the output
terminals. If the voltage on the output terminals exceeds the over-voltage protection threshold, then the Zener
diode clamps the output voltage.
Input Source Impedance
The power module should be connected to a low impedance input source. Highly inductive source impedance
can affect the stability of the power module. Input external L-C filter is recommended to minimize input
reflected ripple current. The inductor is simulated source impedance of 12µH and capacitor is Nippon chemi-con
KZE series 47µF/100V. The capacitor must as close as possible to the input terminals of the power module for
lower impedance.
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