SSTC: Solid state Tesla coil
Solid state Tesla coil
Solid state Tesla coil
An SSTC tunes only the secondary. A bridge drives a few untuned primary turns directly. Nothing in it stores a bang, so the arc is fed for exactly as long as the gate signal lasts, and the drive is the design. Run it continuously and heat is the limit. Chop it with an interrupter at a few hundred hertz and the same hardware throws a longer, brighter arc at a fraction of the duty. Modulate the interrupter with audio and the arc becomes a loudspeaker. The first questions are what the feedback is tracking, how much of the cycle the bridge conducts, and where the heat goes.
tap any part
duty 3.60 %
Pick a part of the diagram to read what it does.
DC bus
The bridge
- start herepower stagein DRSSTC
DRSSTC IGBT vs MOSFET vs SiC: what each switch costs
The choice of switch sets both the frequency you can run and how long the bridge lasts. Three families of parts, and the trade-offs each one brings.
- power stagein DRSSTC
DRSSTC half bridge or full bridge: layout, paralleling, what kills it
Bridges rarely die from peak temperature. Repeated temperature swings fatigue the bond wires over thousands of cycles, well inside the datasheet limits.
- power stage
SSTC dead time and freewheeling diodes: how much is too much
Adding dead time to be safe can make things worse: a longer pause means more diode current, a worse turn-off and a harder hit at the next turn-on.
Gate drive transformer
- start herehow it works
SSTC gate drive transformer design: how to wind a GDT
The top switches in a bridge have their emitters on a node that swings by hundreds of volts. Logic cannot be wired to that directly, so the gate signal crosses a transformer.
- gate drive
SSTC gate waveform troubleshooting: symptom, cause, cure
Three different gate faults look alike on a scope, and each needs a different fix. Change the gate resistor without knowing which one you have and you can make it worse.
- gate drive
SSTC gate resistor value: why the gate loop is an RLC
The gate resistor and the gate transformer have to be chosen together. Lower the resistor without reducing the leakage inductance and you get ringing, not faster switching.
Driver
- start herecontrol
SSTC driver circuit: feedback, phase lead and protection
The phase lead network gives a constant angle, but the switches need a constant time. That mismatch limits the technique, and a QCW, whose frequency moves through the ramp, runs into it.
- start herehow it worksin DRSSTC
DRSSTC driver guide: what the driver board does
The driver board does four jobs. Without it the power stage is just parts, and the frequency it has to follow is not one you can set once and leave.
- control
SSTC that will not start: how feedback takes over at start-up
A current-feedback driver cannot start from the signal it is meant to produce. Getting from that blind start to closed-loop running has its own settings and failures, and they look just like weak feedback.
Interrupter and modulator
- start herecontrolin DRSSTC
Tesla coil interrupter for a DRSSTC: BPS, ontime and duty cycle
The bang rate in hertz is the pitch of the note you hear. There is no best rate, but two of the interrupter's settings can kill the transistors.
- start hereregimes
CW or pulsed SSTC: the criterion that decides the top load
Arguments over whether a coil is CW go in circles because people look at the circuit. Whether it counts as continuous depends on the time scale you look at.
Current transformers
- start heresensing
SSTC current transformers: why feedback and protection need two
Using one current transformer for both feedback and overcurrent protection saturates its core, and the protection gets weaker just when it is needed.
- start herehow it worksin DRSSTC
DRSSTC current transformer: what it is and what it senses
A ferrite ring around one of the primary conductors. It is how the driver measures what the tank is doing, and it is the only sensor the machine has.
- feedback
SSTC feedback: from the primary, the secondary or an antenna
The resonance can be sensed in three places, and the choice usually comes with whatever schematic you copied. Each has its own failure, and one mechanism explains all three.
Tank capacitor
Primary
- start herehow it worksin DRSSTC
Tesla coil primary coil: what it is for in a DRSSTC
The primary is a few turns of heavy copper with no direct connection to the secondary. What it does and why it is built that way.
- start herehow it works
SSTC primary coil design: why it is a different part
Much of the usual advice about primaries is for DRSSTCs and does not apply to an SSTC. Here the primary is not tuned at all; it is a transformer winding, and the aim is a good one.
- resonator
SSTC soft vs hard switching, and why an SSTC couples tight
Whether an SSTC switches softly depends on k squared times Q. With a loose primary at k = 0.15 it never gets there, and switching loss ends up nearly five times the conduction loss.
Secondary
- start herewinding
SSTC secondary coil design: how to wind and measure it
The secondary is a resonator, not just a long transformer winding. Most secondary problems come from winding it as if the turn count were what mattered.
- failure
SSTC racing sparks and flashover mid-winding: the second mode
A failure that looks like too much coupling but is something else. It also explains why a two inch secondary works in a DRSSTC and burns out in a plain SSTC.