If you’ve ever experienced an ESC catching fire when disarming your drone or during a crash, you’re likely dealing with voltage spikes. Understanding and mitigating these spikes can save your equipment and enhance your drone’s reliability. Capacitors and TVS diodes are commonly used for this purpose. This blog post focuses on explaining how TVS diodes work and their effectiveness.
Table of Contents
What Causes ESC Voltage Spikes?
Voltage spikes typically occur during rapid changes in motor RPM, especially when actively braking. These voltage spikes can be significantly higher than the battery voltage, exceeding voltage rating of ESC components and causing damage.
Capacitors vs. TVS Diodes
Capacitors act as voltage buffers—they absorb and smooth out voltage fluctuations. However, capacitors have limitations: once fully charged, their ability to absorb further spikes diminishes. Learn more about capacitors in FPV drone in this guide: https://oscarliang.com/capacitors-mini-quad/
TVS (Transient Voltage Suppression) diodes, on the other hand, act solely as spike suppressors. They have no charging limitation, effectively capping voltage spikes above a specific threshold. Nevertheless, TVS diodes are typically less effective at smoothing out voltage fluctuations compared to capacitors. They do little to reduce electrical noise, a crucial reason capacitors remain the preferred solution.
In my experience TVS diodes are also less effective than capacitors in dealing with voltage spikes in normal operation, therefore capacitors are the preferred option. However, you can also use both solutions simultaneously. In such cases, TVS diodes provide secondary protection, particularly valuable if a capacitor fails.
But is a TVS diode actually useful? Jye Smith (one of the ExpressLRS developers) conducted tests indicating minimal benefit from TVS diodes, highlighting that their added weight might outweigh their protective advantage. You can read more about this here: https://intofpv.com/t-tvs-protection-diodes-debunked.
Where to Buy TVS Diodes
Cylinder TVS Diodes: For instance, a 22V diode like P6KE22A is suitable for 4S batteries.
PCB-based TVS Diodes:
- 2S: SMBJ8A
- 3S: SMBJ12A
- 4S: SMBJ20A
- 6S: SMBJ28A
Or get one with capacitor integrated on a single board: https://s.click.aliexpress.com/e/_om1iCqe
How to Connect TVS Diode in an FPV Drone
For PCB TVS diodes, connect + to + and – to – (just like how you would install the capacitor).
For cylinder diodes, follow the connection diagram below:
Conclusion: Recommendations and Best Practices
- Always use a capacitor: Ensure your ESC includes at least a 470µF capacitor with legs cut short for best performance.
- TVS diodes are optional: If capacitor is present, TVS diodes are not necessary. But they are beneficial for providing secondary protection and can prevent catastrophic ESC failure if a capacitor is absent or compromised.
By following these guidelines and incorporating appropriate voltage spike mitigation measures, you can significantly reduce the likelihood of ESC damage and enhance overall drone reliability.
7 comments
pic has a error. one shows polarity wrong way around.
No, the pic is correct. If you reverse polarity you are going to create a short between positive and negative.
Hi Oscar, huge fan. Are TVS diodes useful for reverse polarity protection? Building 1s drone with 1 x 18650.
No it’s not.
TVS diodes are absolutely necessary for some FCs and to protect other sensitive equipment, I lost two matek h743v3 due to voltage spikes when connecting high C rate batteries thinking they were unnecessary. thankfully my cameras werent fried.
Hello, what diode fór ide with 6s?
Hi, do you think if adding two or more TVS diodes will change something? I mean if FC have already TVS protection then will it make sense to add for example FETtec Spike Absorber for better performence?