IR2117 problem

[renzen]

I have problem with IR2117. The circuit is buck converter using TL494. I'm using soft start 1u capacitor with 10k and 1k resistor connect to DTC. The frequency is 100khz
I tested the circuit on breadboard with IRF4905 P mosfet, works perfectly. Then using IRFZ44n N mosfet with 2n7000 and npn+pnp(bootstrap), also works perfectly.
But when I use IR2117, the output is not correct. The output is only half of the 2 previous methods.
I connect the TL494 with IR2117 like this:

I tested with 1N4148 and 1N5822, 0.1u and 1u, the result is still the same. Help pls....


Thank you.

 

[renzen]

*Update

I've been searching in web, and it's look like many have trouble with IR2117.
Anyone can give me an alternative for IR2117? Or I better stick with discrete bootstrap?
I've read somewhere that it's better and more stable to use high side mosfet driver than discrete bootstrap? Is it true?

 

[alec_t]

I don't see any decoupling cap on the chip supply pin, nor a load on the output?
What load did you have connected when testing? Without a load being switched the bootstrap won't work.

 

[renzen]

I use computer PSU as the power source. From the power source to the circuit, I use 1000uf capacitor. So I don't add capacitor on the IR2117 supply pin. Do I have to add one? I use resistor as a load when testing.
Sorry I don't enclose the whole circuit. The circuit is a basic TL494 buck converter with parallel configuration(pin13 to ground).

 

[ronsimpson]

The two most common errors I have seen with this type of gate drive is:
1) there must be a load on the MOSFET. The source must be pulled to near ground for at least 10% of the time.
2) you can not go to 100% on time. (not your problem)

 

[renzen]

Problem solved

After check and recheck, then put capacitor near the IR2117 supply pin like in the datasheet, it works perfectly. I learned something here.... capacitor is very important
Thank you all for the help.