Is there a DC/DC controller with built-in boost circuitry for mosfet driving?

[LinuxHata]

Hello.
I'm making a flyback power supply, which delivers 50mA @ 200V from 5VDC supply.
Currently I'm using DC/DC boost circuit to generate 12V from 5V, which is used to drive UC3843, which in turn, drives a beefy mosfet, which is directly hooked to 5V rail and everything works fine. However, I'd like to reduce count of parts, and skip DC/DC booster somehow. I tried to use a lower voltage PWM controller, like MCP1632. It works fine, but it's output is designed for driving logicl level mosfets, and it can't really handle my IXTQ82N25P mosfets.

So the question is, maybe there is an low voltage (5VDC) PWM controller, which has built-in boost circuitry, so can drive big mosfets directly?

[ogden]

I wonder why you use monster IXTQ82N25P for 10W power supply?  Select MOSFET which is compatible with mentioned MCP1632 and consider it done.

[LinuxHata]

I'm using it for two reasons

1. Low RDSon
2. Because I have a lot of them and paid around 50 cents for ea. (2nd hand ones from scrap electronics) Any LL mosfet with comparable RDSon will cost at least 10 times more.

[Infraviolet]

Is the on resistance crucial in your application? The IX...'s 38mOhm resistance only loses you 1.9mV at 50mA, would losing a bit mroe to a higher resistance matter when you've got 200V of output?

[LinuxHata]

You're calculating losses wrong. Much more current goes thru that transistor, not 50mA. Roughly saying, about 15W power at input is consumed, this is around 3A thru transistor.

And I've not asked about "how to replace" transistor. I asked very specific question.

[ogden]

I'm using it for two reasons

1. Low RDSon
2. Because I have a lot of them and paid around 50 cents for ea. (2nd hand ones from scrap electronics) Any LL mosfet with comparable RDSon will cost at least 10 times more.

1. Low RDSon for 2A?
2. No matter how cheap you got your mosfets - if they are more than 10x oversized and needs way more powerful driver, you better don't use them.

[ifrythings]

Have a look at the UCC2803/5 they turn on at 4.1v and have a 1amp drive, you probably still need a logic level mosfet though.