A buck converter, also called a step-down converter, takes a higher DC voltage and reduces it to a lower, stable output. A boost converter does the reverse. Both are types of switching voltage regulators and are widely used in electronics projects, vehicles, industrial equipment, and anywhere a DC voltage needs to be converted efficiently. Our stocked range of DC voltage converters can be found here.
What is a Voltage Regulator?
A voltage regulator holds its output voltage steady regardless of changes to the input voltage or the current being drawn by the load. Without one, the voltage reaching your circuit or device would fluctuate as conditions change, which can cause instability or damage sensitive components.
Linear Regulators vs Switching Regulators
Voltage regulators fall into two categories: linear and switching. Understanding the difference matters because it explains why switching converters are used for almost all DC-to-DC conversion today, and where linear regulators still make sense.
Linear Regulators
A linear regulator works by dropping the excess voltage across an internal transistor and dissipating it as heat. The L7805 is the classic example: feed it anything from about 7V to 35V and it outputs a steady 5V. The circuit is simple, the output is very clean, and there is almost no electrical noise on the output rail, which is why linear regulators are still used in noise-sensitive applications like audio circuits and precision analogue references.
The major downside is efficiency. A 7805 running from 12V at 1A is dumping 7W as heat while delivering 5W to the load. Efficiency is simply Vout divided by Vin, so that same 7805 is at most 41.7% efficient from a 12V supply. The larger the gap between input and output, the worse it gets. At any meaningful current draw, a linear regulator becomes a heat problem rather than a power solution.
A linear regulator can only step voltage down, and only by turning the difference into heat. If your input is close to your output voltage and the current draw is low, a linear regulator is a perfectly reasonable choice. If there is a large voltage gap or significant current involved, a switching regulator is the right tool.
Switching Regulators
A switching regulator works by rapidly switching a transistor on and off thousands of times per second, storing energy in an inductor and capacitor on each cycle and releasing it at a controlled output voltage. Because the transistor is either fully on or fully off at any moment, very little energy is lost as heat. Typical efficiency runs between 85 and 95% across a wide range of operating conditions.
The trade-off is a small amount of high-frequency electrical noise introduced onto the output. For most applications this is insignificant, but it makes switching regulators unsuitable for sensitive audio stages where that noise can bleed into the signal. For everything else, and particularly for any application involving meaningful current or a large input-to-output voltage difference, a switching regulator is the correct choice. Buck and boost converters are both types of switching regulators, and they are what all of the converter modules below are built around.
Linear vs Switching at a glance: a linear regulator is simple, quiet, and inefficient. A switching regulator is efficient, slightly noisier, and can step voltage both up and down depending on the topology. For converting between DC voltages at any useful current, switching regulators are the standard choice.
What is a Buck Converter (Step-Down)?
A buck converter, including the models that we stock, steps a higher DC voltage down to a lower DC voltage. The output voltage is set by the duty cycle of the switching transistor, which is the fraction of time the switch is on. A higher duty cycle means a higher output voltage relative to the input.
LM2596-based step-down converters are a common starting point and can be found in the step-down converter range, with options for fixed and adjustable output voltages.
Common Uses for Step-Down Converters
- Powering a Raspberry Pi or Arduino from a 12V vehicle electrical system
- Dropping a 24V truck system down to 12V for standard accessories
- Setting a bench supply to a specific voltage for prototyping without a lab power supply
- Running 5V USB devices directly from a 12V battery or solar system
- Supplying a fixed regulated voltage to a sensor or microcontroller from an unregulated source
What is the LM2596?
The LM2596 is a popular switching regulator IC capable of delivering up to 3A continuous output current. It is available in fixed output versions (3.3V, 5V, 12V) and an adjustable version where the output is set by a trimmer potentiometer on the board.
The adjustable version is the most flexible and is widely used in prototyping and vehicle wiring. A common variant includes an LED voltage display, letting you read the output voltage directly on the module without a multimeter. One thing to be aware of with adjustable modules is trimpot drift over time, particularly in high-vibration environments. For permanent installs where the output must stay at an exact voltage, a fixed-output module or regular re-checking is advisable.
Buck Converter vs Voltage Regulator: What is the Difference?
A buck converter is a type of voltage regulator. The confusion usually comes from seeing both terms used to describe similar-looking modules. A voltage regulator is the broader category, it refers to any device that holds an output voltage stable regardless of changes to the input or load. A linear regulator like the L7805 is a voltage regulator. A buck converter is also a voltage regulator, but one that uses a switching circuit to step the voltage down efficiently rather than burning off the excess as heat.
So the short answer is: all buck converters are voltage regulators, but not all voltage regulators are buck converters. When someone refers to a "DC-DC voltage regulator module", they almost always mean a switching converter; either a buck, boost, or buck-boost, rather than a linear regulator.
At a glance: voltage regulator is the category, buck converter is a specific type within it. A buck converter steps voltage down using switching. A linear regulator also steps voltage down but does it by dissipating the difference as heat, making it far less efficient when the input-to-output gap is large.
What is a Boost Converter (Step-Up)?
A boost converter, such as the units we house, does the opposite of a buck converter: it takes a lower input voltage and raises it to a higher output voltage. The key constraint is that a boost converter can only step up, never down. If your input voltage rises above the set output, the output will follow the input rather than regulate correctly.
An important point that catches people out: because power in equals power out (minus losses), a boost converter drawing more voltage from the output than is going in will draw proportionally more current from the input. Powering a 12V, 1A load from a 5V source through a boost converter will draw over 2A from the 5V supply. The input wiring and source must be rated for this higher current.
Common Uses for Step-Up Converters
- Powering a 12V LED strip from a 5V USB power bank
- Boosting a single-cell LiPo (3.7V) up to 5V for a microcontroller or USB output
- Supplying 24V to servo drives or industrial equipment from a 12V vehicle system
- Running 12V car accessories from a small lithium battery pack
What is the XL6009?
The XL6009 is a boost converter IC commonly used in step-up modules. It operates at a higher switching frequency than older designs like the MC34063, which allows for smaller inductor and capacitor values and a more compact board. It handles input voltages from around 3V to 32V and output voltages up to 35V, with a recommended continuous current output of around 3A depending on input-output ratio and thermal conditions.
Buck-Boost Converters
A buck-boost converter can step voltage both up and down, maintaining a stable output even when the input crosses above or below the target. The main use case is battery-powered applications where the cell voltage starts above the required output and drops below it as it discharges. For example, a 2S LiPo pack might start at 8.4V and discharge to 6V, needing a stable 7.4V output throughout. A standard buck or boost converter cannot handle this on its own. Buck-boost modules are less common and generally less efficient than dedicated buck or boost designs, so they are worth using only when the input-output overlap is a real requirement.
Fixed Output vs Variable Output
Adjustable modules use a trimmer potentiometer to set the output voltage anywhere within the converter's range. They are useful for prototyping, testing, and situations where the target voltage is not known in advance. Many adjustable modules come with an LED display showing the output voltage in real time.
Fixed output modules are set at the factory to a specific voltage (commonly 5V, 12V, or 24V) and cannot be adjusted. For permanent installations where the voltage will never change, a fixed module removes the risk of the trimmer being accidentally adjusted and is a more reliable long-term choice.
Module Housings
Bare PCB Modules
Open PCB modules are the most common form. They are compact, inexpensive, and straightforward to wire into a project. Heat dissipation relies on airflow around the board and the thermal rating of the onboard components. For high-current or continuous-duty applications, monitoring temperature is important as the small PCB has limited thermal mass.
Aluminium Enclosed Modules
Enclosed modules use a die-cast aluminium housing with cooling fins. The case acts as a heatsink, significantly improving thermal performance, and the sealed design makes them a better fit for vehicle installs, outdoor enclosures, and industrial applications where vibration, moisture, and continuous load are concerns. The case can also be chassis-mounted with thermal compound for further heat transfer.
Inside the aluminium housing, the PCB is fully encapsulated in a polyurethane potting compound. The compound fills all voids around the components, protecting them from moisture ingress, vibration, and contamination. It is what allows these modules to achieve an IP67 rating, meaning they can withstand temporary submersion in up to one metre of water.
The enclosed converters in our range use a four-wire lead configuration: a red wire for input positive, two black wires sharing a common negative, and a yellow wire for output positive. This makes wiring straightforward and the colour coding unambiguous in installations where labelling is difficult.
| Feature | Bare PCB | Aluminium Enclosed |
|---|---|---|
| Cooling | Passive airflow | Finned heatsink case |
| Connections | Solder pads or screw terminals | Four-wire leads (red, black, black, yellow) |
| Mounting | Standoffs or adhesive | Chassis-mount with bolts |
| Protection | None | IP67, polyurethane potted PCB |
| Best for | Prototyping, enclosed builds | Vehicles, industrial, outdoor |
Efficiency
Switching converters of this type typically run at 85 to 95% efficiency, meaning 85 to 95% of the input power reaches the load. The rest is lost as heat in the switching components, inductor, and output diode.
Efficiency is not constant across all loads. Most converters reach peak efficiency somewhere in the middle of their rated current range and drop off at very light loads and at maximum load. This matters for battery-powered applications where running at low efficiency at light load drains the battery faster than necessary. If a converter will spend most of its time well below its rated current, check the datasheet efficiency curve at that actual load point.
Heat and Thermal Management
- Touch the module briefly after running at load for a few minutes. Warm is fine, hot enough to be uncomfortable is a warning sign.
- Ensure airflow over the board if it is inside an enclosure. A small gap or ventilation hole makes a noticeable difference.
- For aluminium-cased modules, chassis mounting with a thin layer of thermal compound significantly improves heat transfer.
- Heat shortens the lifespan of electrolytic capacitors. A module running too hot will fail sooner and its output may become noisier as the capacitors degrade.
- If the module is running hot at moderate loads, check that the input voltage is within the recommended range. A very high input-output differential increases switching losses.
How Much Current Can a Converter Handle?
The current rating on a converter module is the absolute maximum under ideal conditions, usually meaning a low ambient temperature, good airflow, and a small difference between input and output voltage. In practice, plan to run the converter at no more than 70 to 80% of its rated current on a continuous basis.
| Rated Current | Recommended Continuous |
|---|---|
| 1A | 700 to 800 mA |
| 2A | 1.4 to 1.6A |
| 3A | 2.1 to 2.4A |
| 5A | 3.5 to 4A |
| 10A | 7 to 8A |
When in doubt, add up the actual current draw of everything connected to the output, then choose a module rated for at least 25 to 30% more than that figure.
12V, 5V, and 24V Converters for Vehicles and Industrial Use
Powering 5V Devices from a 12V System
A 12V to 5V step-down converter is one of the most common applications. Vehicle electrics, solar charge controllers, and 12V battery systems all need a way to power USB devices, Raspberry Pis, Arduinos, and other 5V electronics. A switching converter does this efficiently, as opposed to a linear regulator which would waste nearly 60% of the input power as heat at this voltage ratio. Check that the input voltage range of the module comfortably covers your system voltage under load and when charging, as a 12V vehicle system can sit anywhere from around 11V (low battery) to 14.4V (alternator charging).
Running 12V Accessories from a 24V Vehicle
Trucks, heavy equipment, and some marine systems run 24V electrical systems. Running standard 12V accessories from these directly without a converter risks damaging them. A 24V to 12V step-down converter handles this cleanly. Check the rated current against the total draw of all connected accessories, and for permanent installs, an aluminium-enclosed module mounted to the chassis is a more appropriate choice than an open PCB module.
Supplying 24V from a 12V Source
Stepping 12V up to 24V for servo drives, solenoids, or industrial equipment is a common requirement in automation builds and custom machinery. Remember that the input current will be roughly double the output current (plus losses), so the 12V supply and its wiring need to be rated accordingly. A 24V, 2A output from a 12V source will draw around 4 to 4.5A from the input.
Our full range of step-up and step-down converters can be browsed here.
How to Choose the Right Converter
- Is the output voltage higher or lower than the input? Lower means a buck (step-down) converter, higher means a boost (step-up) converter. If the input can be either side of the output, a buck-boost is needed.
- What is the continuous current draw? Add up everything connected to the output. Choose a module rated for at least 25 to 30% more than this figure.
- Is the output voltage fixed or adjustable? If you know the exact voltage and it will not change, a fixed module is more reliable for permanent installs. If you need flexibility or are still prototyping, adjustable is more practical.
- What is the environment? Harsh conditions, vibration, and continuous duty call for an aluminium-enclosed module. Bench use or enclosed electronics housings are fine with a bare PCB module.
- What is the input voltage range? Make sure your input voltage under all conditions (minimum and maximum) falls within the module's rated input range.
Wiring and Installation Tips
- Use wire sized for the current, not just the voltage. Undersized wire is a fire risk and causes voltage drop.
- Fuse the input as close to the source as possible. If the module or wiring fails, a fuse prevents a larger problem.
- Double-check polarity before connecting. Most modules have no reverse-polarity protection.
- For adjustable modules, set and verify the output voltage before connecting any load.
- Keep the converter's output wiring away from analogue signal wires where possible. Switching noise can couple into sensitive signals.
- For vehicle installs, secure the module so it cannot vibrate against metal surfaces and cause a short.
Frequently Asked Questions
What is the difference between a buck and boost converter?
A buck converter steps voltage down, a boost converter steps it up. Both are switching regulators that use an inductor and capacitor to transfer energy efficiently. The terms "step-down" and "step-up" mean exactly the same thing as "buck" and "boost" respectively.
Can I use a buck converter in a car?
Yes. Check that the module's input voltage range covers the full range of your vehicle's electrical system (typically 10.5V to 14.4V for a 12V system, or 21V to 29V for a 24V system). For permanent installs, an aluminium-enclosed module handles heat and vibration better than an open PCB module.
What size converter do I need for a Raspberry Pi?
A Raspberry Pi 4 or 5 draws up to around 3A at 5V under load. A 3A-rated step-down converter is the minimum, but a 5A-rated module gives enough headroom to also power peripherals connected to the Pi. Set the output to 5.1V rather than exactly 5V to account for any small voltage drop in the wiring.
Is a buck converter the same as a step-down converter?
Yes, they are the same thing. "Buck" is the technical term for the circuit topology, and "step-down" describes what it does. Both terms refer to the same type of device. You will also see them called DC-DC step-down converters, which means exactly the same thing.
Can I run two converters in parallel for more current?
No. Two converters of the same type connected in parallel will not share the load evenly because their output voltages will never be identical. One converter ends up carrying most of the load and runs into thermal trouble while the other barely contributes. If more current is needed, use a single higher-rated module.
Why is my converter getting hot?
The most common reasons are running the load too close to the converter's maximum rating, insufficient airflow, or a very high input-to-output voltage differential. Check the actual current draw against the module's rating, ensure there is airflow over the board or heatsink, and confirm the input voltage is within the recommended range.