Voltage regulators

What is a voltage regulator?

Voltage regulators are useful for stabilizing the power supply in projects such as Arduino , especially when you are powering the Arduino from batteries. Buck converters, for example, can lower the supply voltage for sensors that require a lower voltage than the Arduino can supply. Boost converters are useful in situations where the available battery voltage is lower than needed, and ensure that the project continues to operate stably.

Linear voltage regulators

work by using a voltage divider to regulate the output. They are simple, cheap and easy to use, but they are not as efficient as other types of voltage regulators, as they tend to dissipate a lot of power as heat. Some popular linear voltage regulator ICs are the LM7805, LM7812 and LM317.

Switching voltage regulators

These are also called switching power supplies (SMPS), and operate by rapidly switching a transistor on and off to regulate the output. They are more efficient than linear voltage regulators, but are more complex and can generate electromagnetic interference (EMI). Some popular switching voltage regulator ICs include the LM2675, LM2575, and LM3478.

Buck and Boost converters

Buck Converter

A buck converter, also known as a step-down converter, is a type of DC-DC converter that steps down the input voltage to a lower output voltage. This is useful in applications where the supply voltage is higher than what is needed for the components. For example, if you have a battery that outputs 12 volts, but your device only needs 5 volts, a buck converter can efficiently step down that voltage.

Boost Converter

Unlike the buck converter, a boost converter steps up the DC input voltage to a higher DC output voltage. This is used when the available input voltage is lower than needed. A practical example would be using a boost converter to step up the 3.7 volts of a lithium-ion battery to the 5 volts needed to charge USB devices. Boost converters are important in portable electronics, where a higher voltage is needed than the battery can supply.

Buck-Boost Converter

A buck-boost converter integrates the capabilities of both buck and boost converters, allowing it to either step down the input voltage or step it up to a specific output voltage. This is especially useful when the input voltage fluctuates, as is the case with batteries. Take for example 4 AA batteries, which can have a voltage between 4V and 6.5V, while an Arduino needs exactly 5V to function properly. A buck-boost converter ensures that the Arduino always receives the correct voltage, regardless of the battery level.e

What should I be aware of when selecting a voltage regulator?

It is important to choose a voltage regulator that is appropriate for your specific application, and to carefully review the manufacturer's specifications to ensure that it will perform as expected under the specific conditions of your circuit.

There are a few things to be aware of when using voltage regulators, including:

1. Input voltage range: Make sure that the input voltage range of the voltage regulator is suitable for your application. The input voltage must be within the operating range specified by the manufacturer to ensure proper operation and to avoid damage to the voltage regulator.
2. Output voltage range: Check the output voltage range to ensure that it is suitable for your application.
3. Load current: Make sure that the load current (the amount of current flowing through the circuit) does not exceed the maximum rating for the voltage regulator. Exceeding the maximum load current can cause the voltage regulator to overheat and fail.
4. Temperature range: Be aware of the temperature range in which the voltage regulator can operate. Many voltage regulators have a specified operating temperature range, and operating outside of this range can lead to poor performance or failure.
5. Efficiency: Be aware that voltage regulators can have varying efficiencies, this means, how much energy is wasted as heat during the regulation process.
6. Noise: Some voltage regulators can introduce noise or ripple into the output voltage. This can be a problem for sensitive electronic devices. Usually swtching regulators generate more ripple as linear voltage regulators.
7. Protection features: Some voltage regulators have built-in protection features such as thermal protection, over-current protection and over-voltage protection.
8. Mounting: Make sure that the voltage regulator is properly mounted and cooled to avoid overheating. As switching regulators are more efficient, they usually have less trouble with overheating.

What is a low dropout voltage regulator?

A low dropout voltage regulator (LDO) is a type of voltage regulator that can provide a stable output voltage with a relatively small voltage difference (i.e., "dropout voltage") between the input and output. This makes them particularly useful in applications where the input voltage is close to the desired output voltage, or where a precise output voltage is needed.

LDOs are typically linear regulators, which means that they work by adjusting the current flowing through a pass transistor to control the output voltage. Because the pass transistor is operating in its linear region, the output voltage is directly proportional to the input voltage. The voltage difference between the input and output is a result of the voltage drop across the pass transistor and any other internal losses in the regulator.

LDOs typically have dropout voltage between around 100mV to 2V, which is why they are considered as low dropout, this allow them to provide a stable output voltage even when the input voltage is only slightly higher than the desired output voltage.