How to calculate Ct and Rt for IRS 2453D

[gary350]

How to calculate Ct & Rt in the first circuit drawing? I looked at several date sheets for IRS2453D none of them tell how to find Ct and Rt for resonance frequency. I don't know where else to look?

The second circuit drawing shows values for Ct = 1nf & Rt = 201 ohms but it does not say what KHz it is?

If current limiting coil is 4uh XL = 2 pi FL = 1.6334

With 15v / 1.6334 = 9.185a

This is a good starting point then once the circuit is working with correct heats sinks, I can make adjustments.

Circuit shows 16 ohm load but NO capacitor. I am not building a pancake load coil.

I am building a circuit with IRFP 460 Mosfets.

 

[Diver300]

The data sheet at:- https://www.infineon.com/dgdl/irs2453d.pdf has a graph on page 6 that shows the frequencies.

It's 20 kOhm and 1 nF in the second diagram. That gives around 35 kHz from the graph.

 

[gary350]

The data sheet at:- https://www.infineon.com/dgdl/irs2453d.pdf has a graph on page 6 that shows the frequencies.

It's 20 kOhm and 1 nF in the second diagram. That gives around 35 kHz from the graph.

Thanks that graph is what I needed.

 

[gary350]

WHY is math wrong on this circuit???

Circuit drawing is correct. Meter showed choke 1.24mh all day now that i take a picture meter reads 1.35mh. LOL.

I am testing new power supply with old circuit, I picked the wrong mosfets for the new circuit. I am trying to get the correct value choke before I use it on the new circuit. I can make choke correct by trial & error but I would rather do math to get it correct. New mosfets can handle 37 amps.

 

[ChrisP58]

WHY is math wrong on this circuit???

Circuit drawing is correct. Meter showed choke 1.24mh all day now that i take a picture meter reads 1.35mh. LOL.

View attachment 133920

Is the circuit you show actually oscillating?

If not then the real impedance is just the DC resistance. So the current will be limited by the total DC loop resistance.

Also the ammeter you show is a DC model.

 

[gary350]

Is the circuit you show actually oscillating?

If not then the real impedance is just the DC resistance. So the current will be limited by the total DC loop resistance.

Also the ammeter you show is a DC model.

YES the circuit is oscillating at 80KHz with NO load. Idle current is 2.5a. If I put a 1/2"solid steel rod in the work coil current goes up to 15 amps the frequency drops to 41KHz..

Amp meter is connected in series with DC power supply and the oscillator circuit.

Choke was not connected to the circuit when tests showed it to be 1.24mh.

 

[gary350]

How much over voltage can a 7815 voltage regulator take? The IRS2453 is 15vdc.

My power transformer has taps for 15, 20, 25, 30. 35 vdc Mosfets are 100v 94a.

I might need to have a dedicated 10.6 vac transformer & 15 vdc PS just for the IRS2453