Magnetic Pulser

[Roff]

How did you get 232mA?

Design ultimately should be for 7.2V. I was testing for 5V-12V but even at below 10V it didnt work. Current never went over the limit of 180mA but there might have been some spikes which weren't apparent in the initial current readings.

Where does 7.2V come in? I thought you said you were using a 5V regulator for VCC2. The amplifier is push-pull (bridged), so it will put ±VCC2 across the load. If you are switching the polarity every 23.8mS, the peak current will be 232mA if VCC2=5V. I found this by simulating, because it's quicker and less error-prone than hand calculations. After we settle the voltage issue, I'll post the simulation, if it's still valid.

Is your regulator supply (input) voltage always enough higher than your output voltage to satisfy the headroom requirements?

 

[Narajin]

Ok. I was referring to 7.2V as supply input voltage. I get where you are coming from with 5V as my regulator output.

What are you using for your simulation? Is that where they ideally use rms fomulas, etc..to arrive at 232 mA.

If so, then I might need to change the regulator.

7.2V comes from having 2 batteries in series. My first design had one 3.1V battery as source and it worked. I needed to use the regulator because the amplifier was rated at 5.5V Vdd max.

 

[Narajin]

I was just using a 1 ohm resistor to measure current as well as using a BK precision power supply as a battery substitute and in both cases the current stayed within limits. The one thing that I missed from your insight is the current transients.

 

[Roff]

OK, here's the simulation. It is in LTspice.