PI Expert 100V Maximum Output Limitation
Why is the PI Expert design tool specifically (clamped) at a maximum DC output voltage of 100 VDC?
I have a requirement [LINKSWITCH-CV application] for a simple bias supply for a low power tube amplifier of 250 VDC at 20 milliamp output (Standard US 120 VAC mains input).
Would not everything scale proportionally?
Is is because of (during the MOSFET switch OFF time): The sum of input voltage (VIN) and the reflected output voltage (Vo×Np/Ns) is imposed on the MOSFET = 160VDC + 250* the PRIMARY-to-SECONDARY turns ratio? The issue with that voltage approaching/exceeding the maximum drain to source voltage of the MOSFET switch?
I have a design for those INPUT and OUTPUT voltages that looks like it calls for a PRI-SEC turns ratio of 118:300 so the voltage above imposed on the MOSFET should only be 160+(250*.39) which is only 257V.
Thanks all...
Comments
A design created by PIExpert takes into account all tolerances/ranges of the input parameters. Did you create a design using PIExpert to finalize the turns ratio of 118:300? It seems like you have a single input voltage design. Correct? In most cases, given the turns ratio and input voltage range, the breakdown voltage of the MOSFET may be exceeded, which is the reason PIExpert limits the output voltage to less than 100VDC.
Thank you for your reply.. I though I had been forgotten...
No... I had initially used a competitor's MS Excel-based design tool to come up with the "magnetic component" of the design which does not change based on the primary switching components (except for the switching frequency). I understand what you are saying about all of the parameters: Input voltage, turns-ratio etc coming into play w. regard the the primary-side MOSFET's Drain-to-Source breakdown voltage, but the PIExpert software NEVER allows any desired output voltage greater that 100 VDC independent of any other input parameter to the software (Switching product, Input voltage range selection etc.). The design spec output voltage is "clamped" in the software at 100 VDC MAX output voltage, period. The desired output voltage is the second input parameter to the software after entering the input voltage type....Have you tried to replicate my issue? It would seem that any limitation would consider ALL of the parameters.. It appears to be a software issue to me. I can do the design by hand and it works just fine w. regard to not destroying the output MOSFET.... The key parameter with regard to exceeding the output switch's Drain-to-Source breakdown voltage is the output voltage reflected to the primary (plus the DC input voltage itself) which is in large part related to the turns ratio of the magnetics... I mentioned this in my original post. This is standard flyback design mathematics...Nice software for a low-voltage output though...... Any chances of fixing the software to be more aware of non-low voltage output designs? You guys have a great and innovative semiconductor product suite. My compliments to your team. Thanks.
Thank you very much for reaching out. The PIExpert tool is optimized for designs in the 5-100V Output range and will not allow the user to input output voltages more than 100VDC. Your feedback has been passed to the development team.
I get the same problem. I need a high voltage output at 185V 85mA for my tube valve pre-amplifier. It just 15.725W only. It looks like step-up power supply. Is it possible to allow user to set the maximum output voltage in preferences settings?
The PIExpert tool is optimized for designs in the 5-100 VDC output range. The user cannot set the maximum output voltage more than 100 VDC in preference settings.
Help appreciated