JFW24S3.3-4000 Datasheet, PDF (4/16 Pages) Wall Industries,Inc. – DC/DC Converter

TECHNICAL DATASHEET
JFW24S3.3-4000
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 JFW Series.
Hiccup-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 restart 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.
Output Over Voltage Protection
The output over-voltage protection consists of a Zener diode that monitors the output voltage on the feedback
loop. If the voltage on the output terminals exceeds the over-voltage protection threshold, then the Zener diode
will send a current signal to the control IC to limiting 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 C-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 220µF/100V&33µF/100V. The capacitor must as close as possible to the input terminals of the
power module for lower impedance.
Short Circuit Protection
Continuous, hiccup and auto-recovery mode.
During short circuit, converter still shut down. The average current during this condition will be very low and the
device can be safety in this condition.
Thermal Consideration
The power module operates in a variety of thermal environments. However, sufficient cooling should be
provided to help ensure reliable operation of the unit. Heat is removed by conduction, convention, and radiation
to the surrounding environment. Proper cooling can be verified by measuring the point as the figure below. The
temperature at this location should not exceed 120°C. When operating, adequate cooling must be provided to
maintain the test point temperature at or below 120°C. Although the maximum point temperature of the power
modules is 120°C, you can limit this temperature to a lower value for extremely high reliability.
Figure 3
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Temperature Measure Point
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