How to Convert a 24V Supply to 12V Using Voltage Regulators or DC-DC Converters

Introduction

Converting a 24V DC supply to a 12V DC output is a common task in many applications, such as automotive electronics, battery management systems, and LED lighting. While using resistors as a simple voltage divider might seem like an easy solution, it can lead to significant power loss, instability, and heat generation. This article explores the best practices for achieving this conversion, focusing on the use of resistors as a last resort and highlighting the benefits of employing a buck converter.

Limitations of Using Resistors as a Voltage Divider

The simple voltage divider circuit, involving two resistors in series, can theoretically convert a 24V supply to 12V. However, using resistors in this manner is not recommended for several reasons:

Unstable Voltage: The output voltage will vary with the load, leading to inconsistent performance. Significant Power Loss: Resistor-based voltage dividers dissipate a significant amount of power, which translates into heat generation and efficiency loss. Heat Dissipation: The resistors need to handle a considerable amount of power, leading to thermal management issues.

Alternative Method: Using a Buck Converter

A more efficient and reliable approach to achieving a 12V output from a 24V supply is to use a DC-DC buck converter. Buck converters are designed specifically for this purpose and can maintain stable output voltage and high efficiency. Here’s a detailed explanation of how they work and why they are the preferred method:

Voltage Regulation: Buck converters regulate the output voltage precisely, ensuring stable performance regardless of the load. Efficiency: Modern buck converters operate with efficiencies ranging from 85% to 95%, making them much more power-efficient. Thermal Management: They dissipate significantly less heat, reducing the need for complex cooling solutions and enhancing overall system reliability.

Understanding the Buck Converter

A buck converter works by using an inductor to store energy when the switch is on, and then releasing that energy to the load through a diode when the switch is off. This process, known as the switching cycle, continuously adjusts the output voltage to achieve the desired value.

Calculating Resistor Values (For Reference)

For completeness, let’s go through the calculations for a resistor-based voltage divider solution. The formula for calculating the output voltage using a voltage divider is:

V_{out} V_{in} times frac{R_2}{R_1 R_2}

Given:

V_{in}: 24V V_{out}: 12V

Rearranging the formula to find the ratio of ( R_2 ) to ( R_1 R_2 ):

frac{R_2}{R_1 R_2} frac{12}{24} frac{1}{2}

This means:

R_2: should be half of the total resistance ( R_1 R_2 ). Let ( R_2 x ) and ( R_1 2x ). Total Resistance ( R_{total} R_1 R_2 2x x 3x ). Using Ohm’s Law, we find the required total resistance: R_{total} frac{V_{out}}{I} frac{12V}{2A} 6Omega Solving for resistor values: 3x 6Omega Rightarrow x 2Omega Thus: R_2 2Omega and R_1 4Omega.

Conclusion

While resistor-based voltage dividers have their place in certain applications, such as simple testing or educational demonstrations, they are not advisable for powering devices that require a stable and reliable 12V output. For such applications, a buck converter provides a more efficient, stable, and reliable solution. This method is particularly useful in power electronics, where efficiency and performance are critical.

By choosing a buck converter, you can enjoy:

High efficiency energy conversion Robust output voltage regulation Enhanced thermal management

These advantages make buck converters the preferred choice for many conversion tasks in power electronics and electrical engineering.