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Power Supply For Power Supply

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MOSFET KILLER

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I was recently experimenting with halfbridge inverter circuits and was annoyed that I had to build a seperate power supply for the high side drivers. I have decided to end this problem once and for all, I will build a switched mode power supply to handle it. I was looking at SMPS designs and I have settled on a TL494 (I already have one) for the oscillator and a halfbridge converter to drive the transformer. How can I power the TL494 and other driver circuitry without using a transformer? This circuit will be line operated. I need to step down the 160V DC for the inverter to 12V DC for the driver circuitry. I have seen transformerless power supply schematics but they have very little current output, is there a way to boost the current output.
 
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Use a transformer. An off-line power supply uses a number of transformers anyway, so you're really not getting away from it. They are just usually a bit smaller due to the higher frequencies. Safe off-line supplies are not simple nor easy. I would stay away from trying to build one.
 
I have already built an off-line power supply and it works perfectly, I am now stuck with the task of making it smaller, I was previously using my bench supply. I think that I have a small 18V transformer to power my TL494 and MOSFET drivers. Thanks for your help.
 
So why are you not just using gate drive IC's with the built in high side charge pump systems?
 

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  • IR2110 - IR2113 HAL&.pdf
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  • IR2118 HIGH SIDE D&.pdf
    155.7 KB · Views: 252
The IR2110 is the gate driver IC that I just bought online a few days ago, I need to power my TL494 PWM IC to generate the pulses for the gate driver IC.
 
Do you have a schematic of what it is your working on? It would help clarify things.
 
I am in the process of drawing a good schematic in Eagle. I have a bit of homework so I will work on it again later, I will post it when It is done.
 
now I'm confused because if you bought high side drivers, what do you need the TL494 for? High side drivers allow you to switch on NPNs (or N channel FETs) on the source side (high side) by supplying the higher than collector/source (when a FET is turned on, the Drain is essentially at the source level) voltage needed to turn them on... so you can power them with the same voltage that you are switching????

Unless you are looking for a smaller method of generating your DC and want to use a switcher? See AN8209D from onsemi.com.
you don't mention the power you are looking for? 12VDC at what current?

Linear Tech (lineartech.com) lets you input requirements and it tells you what chips you can use and also has a switcher cad program you can download and draw up a switcher circuit and see what happens with different values. You can't get away from the magnetics, but they are a lot smaller. I'm doing an 80W design right now and the transformer is less than an inch tall (1.5 x 1.5 footprint) and light (compared to power transformers) because it's switching at 100KHz, not 60/50Hz.
 
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