evandude
New Member
here is my current design schematic.
**broken link removed**
For all practical purposes, all the stuff between V1 on the left, and the inductor and MOSFET on the right, comprise my MOSFET driver circuit and can be thought of as just a PWM pulse source.
First off, I'd like to say that i'm reasonably knowledgeable in electronics, but very new to power supply design, so bear with me.
The first problem I thought I'd ask about is the large currents I'm seeing. I am using Micro-Cap for simulation. at a PWM frequency of 2kHz at 10% duty, i am seeing about 27 amps through the inductor (average value) with a 5 amp load on the circuit. However, that is with an input voltage of 12v, and an output voltage of about 11v.
22 extra amps to boost less than 1/2 volt above the output voltage with no switching... (just a diode drop below 12v) that's pretty outrageous.
at a duty cycle of 20%, I am only boosting enough to overcome the diode drop (12v in, 12v out) and yet the inductor current averages over 30 amps.
I don't entirely trust Micro-Cap at simulating this type of circuit... So i want to know if this seems realistic, ie - if there is something really wrong with my design.
Mind you, I am only simulating for the first 5 mS since it takes ages to simulate much further. However over that period the output voltage stabilizes quite well as does the inductor current... so unless it's going to settle down to a current that is around 1/5 or 1/6 of its present value over some much longer period of time, then I need to figure out the problem.
Is it my design?
Is it because I'm only simulating for a short duration?
Would switchercad give me some drastic improvement in simulations?
thanks in advance.
**broken link removed**
For all practical purposes, all the stuff between V1 on the left, and the inductor and MOSFET on the right, comprise my MOSFET driver circuit and can be thought of as just a PWM pulse source.
First off, I'd like to say that i'm reasonably knowledgeable in electronics, but very new to power supply design, so bear with me.
The first problem I thought I'd ask about is the large currents I'm seeing. I am using Micro-Cap for simulation. at a PWM frequency of 2kHz at 10% duty, i am seeing about 27 amps through the inductor (average value) with a 5 amp load on the circuit. However, that is with an input voltage of 12v, and an output voltage of about 11v.
22 extra amps to boost less than 1/2 volt above the output voltage with no switching... (just a diode drop below 12v) that's pretty outrageous.
at a duty cycle of 20%, I am only boosting enough to overcome the diode drop (12v in, 12v out) and yet the inductor current averages over 30 amps.
I don't entirely trust Micro-Cap at simulating this type of circuit... So i want to know if this seems realistic, ie - if there is something really wrong with my design.
Mind you, I am only simulating for the first 5 mS since it takes ages to simulate much further. However over that period the output voltage stabilizes quite well as does the inductor current... so unless it's going to settle down to a current that is around 1/5 or 1/6 of its present value over some much longer period of time, then I need to figure out the problem.
Is it my design?
Is it because I'm only simulating for a short duration?
Would switchercad give me some drastic improvement in simulations?
thanks in advance.