I want to build a switching Power Supply, without the use of IC's with everything already inside. I only want to use op amps and passive components. Below are my goals on what to achieve. I would like to make this PSU current limited, or at least shut off when the current goes too high. I basically took the concept of the linear voltage regulator and expanded on it, turning it into a 'proof of concept' switchmode supply. Input Voltage range: . . . .7-24 Volts Voltage: . . . . . . . . . . . . . . 5-24 Volts Max Current: . . . . . . . . . .10 Amps Price: . . . . . . . . . . . . . . . . $5 -- $10 Instead of feeding a voltage reference into an op amp, I modulated it with a few components. (A triangle wave generator, and a array of resistors to lower the amplitude and introduce a DC bias.) The DC bias is controlled by the current protection module, which is simply an op-amp that reads the voltage on a small resistor and multiplies it by 5. This finalized current controlled, DC reference biased triangle wave is fed into a comparator, which will then switch a rather large MOSFET on and off at about 200 Hz, with varying PWM, depending on how much 'droop' there is on the output. Here is a rundown of what the components will do: OK, I refined my plan to this general specs: Input Voltage range: . . . .7-24 Volts Voltage: . . . . . . . . . . . . . . 5-12 Volts Max Current: . . . . . . . . . .10 Amps Price: . . . . . . . . . . . . . . . . $5 -- $10 I basically took the concept of the linear voltage regulator and expanded on it, turning it into a 'proof of concept' switchmode supply. I don't want to use any prebuilt chips where you have a magic black box with inductors, capacitors and resistors connected to it. I want this to be entirely raw, basic, cheap parts. Maybe later, I will replace many of the op amps with a single programmable chip (like an Atmega328P) Instead of feeding a voltage reference into an op amp, I modulated it with a few components. (A triangle wave generator, and a array of resistors to lower the amplitude and introduce a DC bias.) The DC bias is controlled by the current protection module, which is simply an op-amp that reads the voltage on a small resistor and multiplies it by 5. This finalized current controlled, DC reference biased triangle wave is fed into a comparator, which will then switch a rather large MOSFET on and off at about 200 Hz, with varying PWM, depending on how much 'droop' there is on the output. Here is a rundown of what the components will do: Green field: This contains a voltage regulator which acts as both a 5V power source and a voltage reference. Not only will this module produce a 5V output, but also produce a triangle wave. Blue field: This module will be fed the triangle wave, decrease it's amplitude, and inject it with a bias voltage, controled by the current limiter (red field). Red field: This basic module simply measures current flowing through a 0.1 Ω resistor, and multiply that reading by a factor of 10, and inert it (the circuitry is probably wrong, and I am not sure how this will work, if it even will do what I want it to Will this work?) Yellow field: The final modulated triangle wave is then fed into the last comparator, which will switch a MOSFET on and off at a fixed frequency of 200Hz. The output of this last comparator is now PWM. As the output voltage sags, the pulse width will increase, and cause the final voltage to stabilize at either the peak value of the triangle wave (with little to no load), or near the bottom end of the wave (with a heavy load) ------------------------------------------------------------------------------------------------------------------------------------ My questions: I try to run this in LTspice simulator but some reason the output of the last comparator is a distorted triangle wave. I think this has to do with my filtering capacitor and MOSFET gate capacitance. Can anyone give suggestions about this design? I'm sure the current limiting function is not going to work as intended until I finalize it's design (I hope I don't need more than 4 op amps altogether, It would be nice to use a single chip I already have) Any suggestions? I might just omit this part entirely, as it is not necessary.