Voltage Regulators

Your battery outputs 14.8-25.2V (4S-6S), but most electronics on your quad need 5V or 9-12V. Voltage regulators (also called BECs) step the voltage down to usable levels.

What is a BEC?

BEC stands for Battery Eliminator Circuit — originally named because it “eliminated” the need for a separate battery to power the receiver in RC aircraft. Today, BEC and “voltage regulator” are used interchangeably in FPV.

Types of Regulators

Linear Regulator

Drops voltage by converting excess energy to heat. Simple but inefficient — the bigger the voltage difference, the more heat generated.

Pros: Clean output (low noise), simple, cheap Cons: Inefficient (wastes energy as heat), can overheat at high current draw or voltage drop Used for: Low-current applications, some analog camera power

Switching Regulator (Buck Converter)

Uses a switching circuit to efficiently convert voltage. Much less heat waste.

Pros: Efficient (85-95%), stays cool, handles high current Cons: Can introduce electrical noise (ripple), slightly more complex Used for: Most FPV applications — FC power, VTX, LEDs

Most modern FCs and ESCs use switching regulators.

Common Voltage Rails

Voltage	What It Powers	Current Needed
5V	Flight controller, receiver, GPS, LEDs, digital VTX systems	1-3A
9V	Analog FPV cameras, some VTXs	0.5-1A
10V/12V	Some VTXs, legacy cameras	0.5-1.5A
3.3V	Some sensors, internal FC components	Usually regulated on-board the FC

Where Regulators Live

On the Flight Controller

Most FCs have built-in 5V and sometimes 9V/10V regulators. The 5V rail powers:

• The FC’s own processor
• Receiver
• GPS module
• LED strips
• Other 5V peripherals

Check your FC’s documentation for the maximum current output on each rail. Exceeding it can cause brownouts or damage.

On the 4-in-1 ESC

Many 4-in-1 ESCs include a 5V BEC that feeds up to the FC through the stack connector. This supplements or replaces the FC’s own regulator.

External BEC

Sometimes you need a separate BEC:

• VTX power: High-power VTXs (1W+) can draw enough current to strain the FC’s BEC
• Servos: If using servos (camera tilt, fixed-wing control surfaces), a dedicated BEC prevents servo noise from affecting the FC
• LED strips: Large LED arrays may need their own 5V source

External BECs are small, cheap modules ($3-8) that wire directly to battery voltage and output regulated power.

Noise and Filtering

Switching regulators create electrical noise (ripple). This can appear as:

• Lines in analog FPV video: Horizontal rolling lines
• OSD flickering: On sensitive setups
• GPS interference: Noisy power can affect GPS lock time

Noise Mitigation

1. LC filter: A small inductor + capacitor circuit between the power source and sensitive components (especially analog cameras). Many FCs have these built in.
2. Capacitors: Adding a capacitor near the VTX or camera input smooths voltage ripple
3. Separate power path: Run camera/VTX power from a different BEC than the FC
4. Twisted wires: Twist positive and negative wires together to reduce radiated noise
5. Ferrite rings: Clipping a ferrite ring around power wires can suppress high-frequency noise

Brownouts

A brownout occurs when the voltage drops below what a component needs to operate. Common causes:

• Aggressive throttle punch: Battery voltage sags, BEC can’t maintain output
• Too many peripherals: Exceeding the BEC’s current capacity
• Weak battery: Old or low-quality batteries sag more under load

Symptoms: FC reboots mid-flight (often a flip/crash), OSD disappears momentarily, GPS drops out.

Solutions:

• Use a higher-rated BEC
• Add a large capacitor on the battery input
• Reduce peripheral current draw (fewer LEDs, lower VTX power during launch)
• Use quality batteries with low internal resistance