Reactive damping

[Teleno]

Damping a transmit coil on an inductor instead of a resistor.

On the left the usual damping (grey line, green lines), reactive damping on the right (blue line, purple lines).

This is conceptual only, no testing on the bench yet.

D5 allows recirculation of the current dumped by L1 on L3. D4 and D5 prevent this current from reaching back into L1. Two diodes are necessary because the threshold voltage has to be larger than D5's or else there's no blocking.

The decay is optimized by adjusting L3.

[Altra]

Interesting approach. Is it possible to upload your sim? Or a better image, I can't read the screen shot png clearly

Thanks

[Teleno]

Interesting approach. Is it possible to upload your sim? Or a better image, I can't read the screen shot png clearly

Thanks

Let's do some brainstorming and see if we can come up with a practical circuit.

[Altra]

Thanks! I'll study it

[Altra]

I played with the simulation and found something. The flyback appears quicker, but if you look close the reactive damper doesn't settle completely for a few uS. The resistive damping ends up being faster. I added a diode in series with D5 and the slope went slightly negative.

[Teleno]

I played with the simulation and found something. The flyback appears quicker, but if you look close the reactive damper doesn't settle completely for a few uS. The resistive damping ends up being faster. I added a diode in series with D5 and the slope went slightly negative.

[ATTACH]58009[/ATTACH]

If ypu add a diode in series with D5 then some current goes back to L1 via D3 and D4.

[moodz]

..interesting ...I got a reasonable result with this version of the circuit

[Teleno]

Reactive damping can be adjusted by injecting a bias current in the damping coil such that the energy transferred to the damping coil matches the energy of the Tx coil.

In this circuit there are three consecutive timing periods:

- t1: Charging the boost coil L2
- t2: Transmit period in LTx
- t3: Discharge period. in L3

In the tansition from t1 to t2, which is immediate, L2 discharges into LTx. The charging period t1 is such that the current injected in LTx at the beginning of t2 matches the steady state current of LTx (constant current).
t3 overlaps t2 in order to inject a small current in L3. At the end of t2 the energy of LTx is totally absorbed by L3 leaving only the current induced by the target.

A balanced receive coil LRx delivers the target signal to a preamplifier (missing in the schematic).

In this way a square transmit current signal can be generated with very good quality by properly adjusting the timing t1 and t2. This is advantageously done by a microcontroller that acquires the Rx signal and adjusts the timing to zero the Rx signal.