0-50V 0-10A Variable SMPS

[fethiyeli]

Why drop 24V to 5V for 5V fan.

• Select a 24Vdc fan.
• Delete 5V linear Reg as it will waste almost 4x power as the fan.
• https://www.bing.com/images/search?q=24VDC+Cooling+Fans&FORM=IRBPRS&=0
• Use Nch-FET with Thermistor bias on hot spot.set to 50'C over 5'C range. with low side regulation.
• 2 fans are more reliable than 1.
• Use PC-film plenum to control air flow over hot spots for low RPM but max linear surface speed over hotspot.

I have updated the schematic.

 

[D.A.(Tony)Stewart]

Still wiser to regulate fan with a thermistor and low overhead air flow plenum.

Often, the Core is hotspot, ... epoxy thermistor to core then with twisted pair to board header, etc or hardwire for rugged applications.

 

[fethiyeli]

Still wiser to regulate fan with a thermistor and low overhead air flow plenum.

I have designed fan control circuit such that fan speed is proportional to current. What is the benefit of adding a thermistor ?

 

[fethiyeli]

Still wiser to regulate fan with a thermistor and low overhead air flow plenum.

Often, the Core is hotspot, ... epoxy thermistor to core then with twisted pair to board header, etc or hardwire for rugged applications.

Now i got it. Other problem is how to feed NCP163 and other PWM IC and opamps. I have used TOP246YN but i dont want to use it in deed. I have always heard that this TOP ICs are so vulnerable. Do you have any suggestion to feed PFC, PWM ICs and opamps ? You have stated to use 2 fans. 2 fans in parallel or in series ?

 

[fethiyeli]

I would use a micrel integrated chip boost converter (or sepic etc) to provide the startup voltage to your chip.....then it can disable itself, or you just leave it in there. I think its MICXXXX or MIC33XX or something....good and few components, as the fet is in the control chip,
that is your voltage is not quite right, as u described, so use the micrel to get it to what you want.

We are able to find MC34063 here. Can u suggest it to use for supplying NCP1653 ? I will set the output voltage as 16V for NCP1653 so no problem will appear i guess. But still i need isolated supplies for UC3844, opamps and fan.