Circuit to Drive Ultrasonic Transducers

[vandymike]

Thank you all for your help.

I have a project to drive 6 Ultrasonic Transducers that are connected in parallel. Each transducer is rated at 50 Watts at 40 khz. The transducers should provide 300 Watts to a cleaning tank.

Can anyone help with a simple circuit to drive all 6 transducers? I have the 40khz signal circuit designed with a 555 timer and have used a JK flip flop to get a 50% duty cycle.

 

[Nigel Goodwin]

You need a LOT more details than that, for a start what impedance the transducers are?, but you're unlikely to find a 'simple' circuit, as a 300W ultrasonic power amplifiers isn't going to be trivial. Depending on the transducers, you may also need a large custom wound transformer to feed them?.

 

[vandymike]

Attached is the schematic of the drive circuit. I am using a bifilar wound transformer to drive the transducers. I just cannot get this circuit to work for more than 5 minutes as the driver IC EL7222 blows up. Not sure what the problem is so I thought there may be an easier way to drive these.

I have a 40khz signal from a 555 timer with a 50% duty cycle. I was wondering if I could have a cross conduction issue?

 

[Nigel Goodwin]

The circuit you posted doesn't use a flip/flop, but even if it did, that's not good enough - you need a short interval when BOTH outputs are turned OFF, this gives time for the first to turn off properly, before the next one turns on. I'm also dubious about just those two devices providing 300W output?.

 

[vandymike]

I did modify the design with a JK flip flop to ensure a 50% duty cycle. The EL7222 is driven by the Q outout. The 7222 is wired in complimentary mode so that each MOSFET is driven opposite each other.

I had wondered if it was possible that both FETS could be on at the same time.

Any ideas on how to drive these Mosfets?

 

[Nigel Goodwin]

I did modify the design with a JK flip flop to ensure a 50% duty cycle. The EL7222 is driven by the Q outout. The 7222 is wired in complimentary mode so that each MOSFET is driven opposite each other.

I had wondered if it was possible that both FETS could be on at the same time.

They will be, you can't just drive them from a simple square wave.

Any ideas on how to drive these Mosfets?

Essentially the circuit is a crude inverter, there are a number of designs around, some of which ensure that the outputs can't both be on at the same time.

Personally I'd replace the 555 with a PIC, and program it to drive your driver chip correctly - making sure there was no chance of both FET's been on together.

 

[vandymike]

Thanks for the advice. I have never used a PIC before. Any suggestions on one? How can I learn about these devices?

 

[Nigel Goodwin]

Check the 'sticky' in the Microcontroller forum, or read my signature.