Pwm circuit - DIY - 80Ah test.

This is my homemade PWM circuit.
it can handle 80A con. at 55Vmax..
this is only a prototype and it is just a test motor. the pbc is made for 2 extra power Fet's and a fet driver more..
here is a example of my schematic, this is not the exact one just a draft: http://img189.imageshack.us/i/pwmstyring.png/
this test is at 24V.

Category:

Science & Technology

Tags:

• Diy
• PWM
• Pulse
• with
• modulation
• DC-motor
• DC-controller
• Power
• switching
• power
• electronic

[260830107]

i think a PWN circuit can be done with just a 555IC and 2 diodes

[sponkii]

@260830107

I know that, but it cant go from 0 to 100% and a single 555 can't run a big motor, or a a fet at high speed.

[BlackandChrome]

Circuit schematic would be great. The previous imageshack link you posted is dead. Looking for a 24v PWM controller of DC above 25A. This looks like the ticket if it is something I am suave enough to implement.

[sponkii]

@BlackandChrome

there should be a working link in the vid description now.

[hatwithfloppers]

Could you please send me the schematic? Thank you! :)

[sponkii]

@BlackandChrome

The power that is dissipated in the mos is Current^2 * ON-Resistance + switching loss (more complicated)

switching loss depends on gate charge, the load, current, switching frequency.

The C/W characteristics depends on casing if it is TO-220 or TO-247.. it is in the data-sheet, you add Rthj-case (can be even more parts) + heat sink C/W + Ambient temperature to calculate the Die temperature at a certain load.. i wouldn't recommend temps higher that 100celcius.

[BlackandChrome]

@sponkii

Well I'm actually only drawing 13A max but I suppose that would still explain why the mosfet exploded after about 15 seconds... I think I understand the dissipation equations, Rthj-case*Current=Power Dissipation, PD*Rthj-amb=temperature increase. Although what calculations are there regarding heatsinking?

I still cant get your link to work...

Thanks

[sponkii]

second reply:

time when you drain 22Amps through them. at 100celcius (die temperature) you can only draw 15A..

lets say you drain 19Amps, that roughly calculates to 28watts of raw heat without swiching losses som you might end up with 35watts of heat loss in the mosfet. that would result in a mosfet that is nearly 2200 celcius (noot good), if you use two you have half the heat dissipated in each mosfet, that is still WAY to much, i would recoment heatsink of 0.8 to 1.2 C/W..

[sponkii]

@BlackandChrome

Have you look at the new link?

- you can easily use a mosfet driver with a 555, the driver is just a sort of "buffer" that take a given value (usually 2.5V to VCC) at is inputs and then sends a voltage to its outputs, with the possibility of a high current, when the voltage is below 2.5V then it clamps the output to GND and then discharges the gate quickly..

As to the use of IRF540 the 22A is at 25celcius, which you wouldn't be be able to keep them below at any (continued)

[BlackandChrome]

@sponkii

I think I got it covered. Found a schematic for a 555 timer circuit that drives a Power MOSFET at 1khz PWM. put a 7212 voltage regulator in front of it to drop the 24v, and Stuck a IRF540 rated at 22A on the output to drive the motor. May put 2 of them in parallel and run without heatsinks. Although I am open for suggestions on a circuit using a mosfet driver.