Why Constant Voltage Sources Prevail Over Constant Current Sources in Electronic Circuits

Although constant current sources are widely used, particularly in applications like powering LED lights, the vast majority of electronic circuits prefer to use constant voltage sources. This article explores the reasons behind this preference, focusing on applications such as battery chargers, LED drivers, and measuring instruments. We will delve into the advantages and practical applications of constant voltage sources, explaining why they are more commonly utilized in electronic circuit design.

Advantages of Constant Voltage Sources

Why Use Constant Voltages?

Although the initial premise was about using constant current sources, it is essential to consider the numerous benefits of utilizing constant voltage sources in electronic circuits. Here are some compelling reasons:

1. Efficiency and Power Consumption

One of the main advantages of a constant voltage source is efficiency. In an open circuit scenario, where no load is connected to the constant voltage source, the voltage remains constant without any corresponding power consumption. This makes it an ideal choice for applications where minimal power waste is crucial. In contrast, a constant current source would still consume power to maintain the current, even when there is no load, leading to unnecessary energy loss. This is particularly important in battery management systems where every watt of saved energy is significant.

2. Simplified Series and Parallel Connections

When connecting components in a series configuration, it is more practical to use a constant voltage source. This allows for independent control of individual components, which is essential in many complex circuits. For example, in a series circuit powered by a constant current source, failing to address each load individually can lead to issues. On the other hand, parallel connections with a constant voltage source are simpler and less prone to failure. This is because a failure in one component does not impact the others, making it easier to identify and replace faulty components.

3. Cost and Practicality

Another significant advantage of constant voltage sources is their cost-effectiveness and practicality. In parallel connections, the loads can be designed to handle the same maximum voltage from the source. This means that the wire size is directly related to the current load of the individual component, making it cheaper and lighter to fabricate. In series connections with a constant current source, all components must carry the same maximum current from the source, leading to a higher wire gauge and consequently heavier and more expensive components. This makes parallel configurations with constant voltage sources more practical and cost-effective.

Applications of Constant Voltage Sources

Battery Chargers

Modern Lithium polymer (Lipo) batteries require controlled initial charging phases, often involving constant current to ensure proper charging. However, for both Lipo and lead acid batteries, constant voltage sources are used during the later stages of charging. This is because a constant voltage source provides better efficiency and safety, preventing overcharging and ensuring optimal battery health.

LED Drives

LED lighting systems are a prime example of the importance of constant current sources. However, many applications also rely on constant voltage sources. LED drivers are designed to operate at a specific voltage, and constant current LEDs have internal or external current regulators. In simpler applications, such as maintaining uniform brightness, a constant voltage source with appropriately chosen resistors can serve as a basic, albeit less efficient, alternative.

Measuring Instruments

Many measuring instruments, such as multimeters and test equipment, use constant voltage sources to ensure consistent readings. The use of a constant voltage source helps in providing reliable and accurate measurements across various types of loads, making it a preferred choice for precision instruments.

In conclusion

While constant current sources have their applications, particularly in special cases like LED lighting, the widespread adoption of constant voltage sources in electronic circuits is driven by their efficiency, simplification of circuit design, and cost-effectiveness. From battery chargers to LED drivers and measuring instruments, constant voltage sources offer a balanced approach to power management in electronic systems.