555 as mosfet driver with or without pwm

[sadman]

see this nice video tutorial

https://www.youtube.com/watch?v=FKqkRDM0Al0

sadman

[PM3295]

Long ago, I was asked by a friend to design a high-power buck converter (48 V to 12 V @ 25 A) using the 555 as the controlling PWM element. The design below simulated with very good load transient response at 25 A. I never actually build this design, and I don't think he got around using it at the end.

It shows at least that you may be able to manipulate the 555 to do other interesting tasks besides its usual application functions.

[sadman]

HI PM3295

nice circuit idea shared, I have made switch mode adjustable voltage regulator with 555 timer using voltage control pin which also be used audio modulation for long distance audion transmeter.

sadman

[bobcat1]

Hi

555 can only drive/Sink  300mA so you need carefully choose the Mosfet you drive
Far more easy to use dedicated Mosfet driver who can drive more powerful Mosfet

All the Best

Bobi   

[PM3295]

You would never think that HP would use a 555 timer as part of any switching supply, but they did in the 5 V supply of the HP 3314A function generator.

Here is a link to the HP service manual if any one want to understand the operation.
https://www.keysight.com/us/en/assets/9018-05762/service-manuals/9018-05762.pdf?success=true

[PM3295]

I managed to simulate the circuit with some substitute transistors. To get it to work, I had to change the values marker in red.

[microstick]

Hi,
I have a question, what simulator have you used for simulation of this circuit. Looks very good to me. So, I would like to use the same in the future. Please provide just the name of it.
Thnk you

[PM3295]

https://penzar.com/topspice/topspice.htm

[PM3295]

On one of the HP repair forums, it was mentioned that, there are some errors in the circuit diagram shown in the service manual. Someone compared the actual circuit against the schematic and discovered the errors.

The newly revised parts marked in red, are shown to be the wrong types in the service manual. The PNP should be NPN, and NPN must be PNP. The part of the circuit with the new NPN only affects the start if the raw supply voltage is high enough (under voltage lock-out), and makes no real difference in the simulation results. The corrected PNP, on the other hand, makes the turn-off  time of the driver Q10 and chopper Q9 faster, and operation more efficient. The start up drive pulses are also much cleaner. I was struggling to explain the NPN used to shut off the driver, when I looked at and simulated the circuit the first time.

Using these modifications, the circuit simulated easily with the unmodified resistor values.

Results show the design to have an adequate phase margin.