Hi, I'm trying to build a 12 Vin to 200 Vout @ 50mA SMPS.
At first, I used Switcher Pro, and it said I should use the TPS40210, it was the only option showed:
The schematic is the following, I already builded it, but I can't get it working with the calculated components by Switcher Pro, I had to reduce the Soft start capacitor, and the Inductor, this way I get 200v but not 50mA output.
So I tried with webench tool, and it says that TPS40210 isn't suitable for my application: "Design cannot be created with this device. Please press OK and select a different device from the list Or click below to show why parts were not found."
If I look for the reason, it says that I'm exceeding the duty cycle limit.
SwitcherPro says the duty cycle with my parameters would be 94.6% max.
I made a simulation in tina-ti, with the values calculated by switcher Pro, and it works.
The diode and mosfet aren't the ones which dictated Switcher Pro, but I have changed it's parameters to match with the indicated components.
In my physical circuit, with the values suggested by switcher pro, the first thing I noticed was that the frequency was wrong, with 549k and 100pF I should have a 300khz, but instead I have the half, I measured this just connecting Vin, Gnd and the RC network, I measured the same with everything connected.
Should I multiply my Rc resistor in order to force the 300khz? If I just connected power supply and Rc circuit, what could I have made wrong? :(
Second thing, mi Soft start pin vs my Vout looks this way:
I can see that my controller is resetting itself, in the last picture I used a 10uF SS capacitor, same result with a 2.2uF but different period of time.
And finaly if I measure the voltaje at the sense resistor, not at the sense pin, I see this:
So my SMPS is always resetting itself, but I used the values suggested by the software, I have any load apart of the output capacitor.
Is the Webench tool correct when it says that TPS isn't suitable for my application?
Why I can't even get the frequency working?
I'd appreciate any help that you can bring me.
My best regards