[SOLVED] IRS2453D H-Bridge Driver problem

Hi all,

I'm trying to invert 230V dc i have from a DC-DC converter to a modified sine wave, im using IRS2453D to drive the bridge, I need the output to be at 50Hz, so according to the equation they have in the datasheet page 13 I calculated the RT, with CT being 10 nF, the problem im having is that theres no pulsing at the output of the chip, I only get a spike when it turn it on and no PWM, Ive tried different values for RT and CT to match those on the graph provided in the datasheet but with the same result,

Ive attached the schematic and the spike, and the link to the datasheet

Please I need help with this

thanks!!

this looks like something is driving that shutdown pin high.
btw, you essentially can't use the shutdown pin because to reset the driver you have to cycle the power to the irs2453, so the shutdown has to be used as a last ditch effort to turn off the device. i think when it shuts down the outputs of the 4 drivers are low. when you pull the CT pin below 1/6th of VCC the low side switches both turn on and the high sides turn off. the problem is there's no dead time when this happens. so its not practical to use this functionality as a shutdown pin either.

also, i would do away with an RC cap for 50 Hz, use a transistor to level shift a 50 hz square wave produced from something reliable and feed it into the CT pin.

also, your resistors of 120 ohms practically dictate that you should get a pulse longer than 1 us out of the H bridge i'd think.
also, you only have 13 volts on your scope, so you obviously are not getting the high side fets to turn on.
i think in practice you need at least 1uF for the boot strap capacitors to hold up the some odd microamps of discharge/leakage current for operation at 50 Hz.
I was able to run one of these chips at just a few hz with 10uF btw, but the board was clean and dry.

thanks man! connecting SD to ground solved the problem!