zero current switching ic

[anotherbrick]

hello dear forum

I need a zero current switching IC for driving half bridge inverter
which is powering an ultrasonic welding horn
frequency is 15 to 35 Khz depending on horn type
power is up to 2.5 KW
this IC must oscillate freely near resonance frequency until catching ZC signals
after then it must pass to ZCS mode

can you advice me such a ZCS IC ?

thank you

 

[betwixt]

It sounds like you need a PLL and a current pick-up to lock it rather than a "ZCS IC".

Brian.

 

[Easy peasy]

time to do a literature search / google ...

 

[anotherbrick]

hello thank - I need ZCS IC

ultrasonic horn does not behave linear for work with 4046 PLL

I need to turn on IGBTs at ZC - it is the resonance point, very steep

please name a ZCS IC if you know

 

[d123]

Hi,

Is a (latching) comparator as the zero crossing detector plus suitable gate drive, plus maybe a flip-flop to toggle between oscillator and ZCS mode a naïve suggestion or wrong as you need to keep it to a one part solution?

 

[Easy peasy]

yes current Tx to see the current and a PLL - 4046 as per your above - just need a design engineer to design it ...

 

[betwixt]

Expanding on that: detecting zero crossing voltage is easy but you are looking for zero crossing current. Given the type of load you probably have, the current and voltage will be out of phase so you can't use voltage detection unless you know the phase difference and it is constant in which case you can compensate for it. To detect a current there are two methods - one is to interrupt it and add a detector in series, the other is to use a current transformer. The transformer method is not invasive, it clamps around the wire to monitor the current through it.

I think you will never find a zero crossing current detector IC. Your best option is to use a current transformer and use it's output to lock the oscillator against a stable reference frequency. There are many devices that can do that but none that I know of that can directly drive an IGBT, you will have to do it in stages.

Brian.

 

[BradtheRad]

A lone sense resistor detects voltage and current exactly in phase.

This simulation has a series LC creating a resonant frequency.
The op amp detects zero crossings across a low-ohm resistor. (The sense resistor can be in a strategic location in the loop.)
In turn the op amp drives a half-bridge at the resonant frequency.

 

[anotherbrick]

my design is complete up to the sceme below
I need to connect IR 2113 to zero cross detector appropriately and add dead time too

thanks for any advice

 

[Easy peasy]

it's more important to do the zero cross at the 1/2 bridge than at the horn - they are phase shifted ...

 

[BradtheRad]

There's a question whether your ultrasonic horn has its own resonant frequency. If so then isn't it your aim to detect that frequency? Your schematic looks as though other frequencies occur due to LC resonance behavior.

I could be wrong. My simulation derives its oscillating frequency from the LC network and that's the reason I put it in my simulation. However in the case of a piezo transducer load, it may have its own resonant frequency.