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luka 21st September 2006 06:28 PM

oo and how do you charge cap, that is in high side of IR?
With costant voltage and his reference connected to drain of mosfets?

luka 21st September 2006 06:32 PM

You should make dead time with tl494 not some where in the circuit with R-C

Danko 21st September 2006 06:33 PM

That capacitor charges through D1 and /inrush current limiting/ R28.
The cap is connected to the source of the high-side mosfets.

luka 21st September 2006 06:40 PM

oops my mistake, I ment source.

Ok I see how you got it.
I will have to check at home how I have done this.
While I think now I think I have made it too complicadet

Danko 21st September 2006 06:41 PM

I need the PWM signal, coming from the TL494, and the inverse of the signal. TL494 cannot make the inverse of the signal, that I need.
I can invert the PWM with a single transistor, like a BCxxx, or with a TTL/CMOS inverter, or I can connect the TL494's transistor's in the way, you can see on the schematic.

When I use TL494 in push-pull mode ( OUTC tied to VREF ) then both the outputs will have the same duty cycle. For example 30% 30%, but I need to drive the high-side MOSFET with 30% Duty-cycle, and 70% duty-cycle, the lower MOSFET.

luka 21st September 2006 06:46 PM

aha that's whay I use only Hi mosfet:rolleyes:

Danko 21st September 2006 06:47 PM

Yes, that's simpler. That is lower efficiency, less complication, less fun :-)

luka 21st September 2006 06:50 PM

That is lower efficiency, less complication, less fun, but since this is not for me and I don't have 5 years to make it, it will have to do :)

Danko 22nd September 2006 06:56 PM

I was experimenting a little bit in my simulator.
I created a schematic, wich makes about 750nanosec dead-time.
Is that too much? Or too short?

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T1 transistor is the TL494's output transistor. I applied 50% duty-cycle square-wave to the transistor.
On the schematic there is CD4069, becouse the simulator haven't got CD4049 in it's library. I'm going to use CD4049.

What do you think of this? Will it work in the real world? :-)

luka 23rd September 2006 04:58 PM

I think that time is quite good, maybe make it variable.

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