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Maxim > Design Support > Technical Documents > Application Notes > Automotive > APP 2400
Keywords: MAX5052, pwm controller, synchronous rectification, forward converter, high efficiency, power
supply, power supplies, forward converter, input reverse voltage protection, pulse width modulation,
controllers
APPLICATION NOTE 2400
A Compact 36-72V DC Input, 3.3V/10A Output
Power Supply
Sep 29, 2003
Abstract: A compact power supply that provides a regulated 3.3V at currents up to 10A using the
MAX5052A PWM controller is described here. This power supply operates from -36V to -72V and uses
synchronous rectification to achieve efficiencies greater than 88% at 10A. It uses a single transistor
forward converter with a reset winding and has a maximum duty cycle of 50%. It has input reverse
voltage protection, and will regulate to zero load. The isolation voltage is 1500V and it has over-voltage
and over-current protection. It can be turned on and off by the remote on/off pin and it has a thermal
shutdown feature which protects the supply from excessive temperatures. The unit has hiccup current
limit to limit the RMS current during an output short.
General Description
The output of this power supply is an isolated 3.3V/10A output, produced from an input is 36-72V DC.
Airflow is required at higher ambient temperatures to get the full rated power.
The topology used is a single transistor forward, with a reset winding on the transformer to reset the
core. The maximum duty cycle is less than 50%. The design uses the MAX5052A PWM controller.
Specifications for power supply
Input -36V to -72V DC
Output 3.3V
Full load current 10A
Minimum load 0A
Load and Line Regulation ±1%
Isolation voltage 1500 VDC
Over-voltage protection
Over-current protection
Remote on/off (active high)
Thermal shutdown
Input reverse voltage protection
Efficiency >85% at full load
Some of the features of the power supply are discussed below
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