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24V to 13,8V @ 20A pwm step down dc-dc converter

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Dear sirs,

I need a compact high efficient step-down pwm voltage regulator to reduce from 24Vdc to 13,8Vdc with 25A if possible with controllers like TL494 or MC34063 or UC3842,43,44,45 and mosfet power transistors.

Regards,

Fernando - Call sign PU2PLL
 

Hi,

for high efficiency I recommend a "synchronous" step down regulator.
for compact I recommend high switching frequency.
To select a suitable controller I recommend to use the interactive selection guides at the IC manufacturers and distributors internet pages.
(There you can play around and find the best solution for you. If you ask 10 enigneers for their best suited design you will get 10 different designs..and maybe none that is suitable for you.)

I doubt any of the given devices can satisfy your needs.

For the given devices the manufacturers provide datasheets, application notes design notes some have online desgn tools where some are able to draw a complete schematic and give BOM.

Klaus
 

I go with Klaus. Design for low ripple. Synchronous switching will minimize switching losses and will ensure CCM. Switch at a high enough frequency for portable design.

However, if you have the controllers you mentioned already and you really want to use one from the list, then UC3843 should do and it is relatively inexpensive. It has max duty cycle in the 90's and can go as high as 500kHz. You could consider some frequency around 250KHz and 300kHz. But others components will be much bigger than you would have had for a much higher switching frequency.
 

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