Power supply simulating problem

[meysaminter]

I am designing 300W power supply with 300V output. my design based on tl494 . I used it in Boost topology . I want to have 300V output . so I calculated the parameters . but when I simulated it in LTspice . the output voltage was aboat 190V !!! I changed many parameters but the output did't changed anymore. SO I don't now what to do!!! plz check my circuit and tell my what is wronge with it .

 

[bountyhunter]

Won't open on my computer.....

what is load current on the 300V output?

What is the input voltage?

 

[meysaminter]

input voltage is 50V and maximum ampere is 1A.

 

[crutschow]

I don't know what a .rar file is. Please attach as an LTspice.asc file

 

[bountyhunter]

input voltage is 50V and maximum ampere is 1A.

300Watt boost converter is no trivial design. It's not the topology I would choose. It will take a huge inductor and the switches will probably be handling 10A peak currents or more.

 

[ericgibbs]

I don't know what a .rar file is. Please attach as an LTspice.asc file

Morning Carl,
I use this free download for all compressed files, including 'rar'.
**broken link removed**

hi meysaminter,
Unpacked your files, why did you rar the lib part of the files inside the first rar,? makes it a pain to unravel.

Also I would suggest that you post your files with includes that dont make it necessary to load the files into the LTS sub folders.

I prefer to run all 'unknown' files from my desk top.

I did get your asc file running, but its very slow also I get errors reported regarding the modules.

Who did the circuit design.?

Added text:
A couple of minor errors on the circuit.

V1= Rser 0.0.1
Vcc and Vsupply Labels on the same wire

Why are you using a High/Low side driver IC,? , you have a low side driven MOSFET connected to the high side driver.??
E

 

[alec_t]

@Eric
I extracted all the files into a common folder and modified the .lib command to point to that. The sim ran partly; until it encountered the dreaded 'time step too small' error which you may remember I mentioned in another thread .
However, stripping off the left half of the circuit and just driving the FET with ~30kHz 50% duty cycle square-wave got things working.

@meysaminter
5mH is way too high for the PWM frequency you're using. The inductor current doesn't have enough time to rise to a decent level. Try 100uH or less and you'll find you get a much greater output voltage.

 

[WTP Pepper]

input voltage is 50V and maximum ampere is 1A.

Well you are not going to design a 300W PSU with this input. I would plan of ~10A input at 50volts to come close to your spec.

50v & 1A is 50W in ideal conditions. I suspect the startup conditions of what you are designing just can't deliver the current.

 

[crutschow]

................................
@meysaminter
5mH is way too high for the PWM frequency you're using. The inductor current doesn't have enough time to rise to a decent level. Try 100uH or less and you'll find you get a much greater output voltage.

A 5mH inductor will work at a high PWM frequency. It just takes a while based on the output LC time constant (a long while when you are simulating it) to reach the final value. The advantage of a larger inductor is a smaller ripple current and output ripple voltage. But, of course, good engineering practice is to use an inductor no larger than necessary for the load and ripple current you need.

 

[alec_t]

A 5mH inductor will work at a high PWM frequency

I stand corrected. Thanks. I guess what seemed to be a horizontal voltage trace in the sim must have been an exceedingly shallow ramp?

 

[crutschow]

Morning Carl,
I use this free download for all compressed files, including 'rar'.
**broken link removed**

................................

Thanks for the info.

But for the small .asc files that LTspice generates there's no reason to compress them and make us go through the exercise of de-compressing them (unless, of course the op is using a dial-up internet connection ).

 

[crutschow]

I stand corrected. Thanks. I guess what seemed to be a horizontal voltage trace in the sim must have been an exceedingly shallow ramp?

That's likely so. The voltage will ramp up as determined by the resonant frequency of the LC output filter. It takes about 1/8th of a resonant cycle for the output voltage to reach the input voltage applied to the inductor. What are the L and C values?

 

[alec_t]

What are the L and C values?

5mH, 10uF. Here's the OP's sim (simplified to use a 50:50 m/s ratio ~30kHz voltage to drive the FET).
BTW, the OP's original asc file called additional model/library files, so they were all zipped together. Perhaps rar, not zip, is the preferred compressed format for Linux machines?

 

[WTP Pepper]

Not to rain of your parade but which part of 50v @1A is not equal to 300v @ 300W do you not understand?

 

[alec_t]

I think the '1A' refers to the required output current. Input current wasn't specified IIRC.

 

[crutschow]

The output voltage varies with the clock duty-cycle, of course. A duty-cycle of 80% will give you about 300V out.