In nearly every circuit design, incorporating at least one voltage regulation stage is essential. There are two primary types of power supply designs: linear and switching. Linear regulators are simple to implement but suffer from inefficiency, particularly when there is a large voltage difference between the input and output. Additionally, as the output current increases, efficiency decreases, and heat dissipation becomes more significant.
Switching regulators, on the other hand, are highly efficient but may introduce noise to the output if not properly designed or filtered.
While there are various switching regulator options available, the TPS54331, introduced by Texas Instruments, offers an excellent solution. According to its datasheet: “The TPS54331 is a 28-V, 3-A non-synchronous buck converter that integrates a low RDS(on) high-side MOSFET. To improve efficiency at light loads, a pulse-skipping Eco-mode feature is automatically activated. Additionally, its 1-μA shutdown supply current makes it ideal for battery-powered applications. The current mode control with internal slope compensation simplifies external compensation calculations, reduces component count, and allows the use of ceramic output capacitors.”
The regulator can provide output voltages as low as 0.8V. It also operates at a high switching frequency of 570 kHz, which enhances its performance. Figure 1 below shows the efficiency chart in relation to output current and input voltage.
Figure 1: Efficiency Chart at 3.3V Output
The chart clearly indicates that the highest efficiency (nearly 95%) is achieved when the input voltage is around 5V and the output current is between 100mA and 1A. In most digital circuits, the input voltage is typically 12V, where the efficiency is approximately 88% with a 1A current.
The TPS54331 datasheet provides a table for setting the output voltage by adjusting two resistors. However, in this article, I have modified the design to allow for a variable output. By using a multiturn potentiometer, the output voltage can be adjusted. Figure 2 illustrates the schematic diagram, where turning the VR1 potentiometer will change the output voltage.
Figure 2: Schematic Diagram of the Switching Voltage Converter
The schematic was created using Altium Designer; however, you are free to use your preferred CAD software for redesigning it. Just follow the schematic and adapt it as needed.
When selecting input and output capacitors, ensure they are rated for the appropriate voltages. In this design, the input is set to 12V, so the output will not exceed this value. I recommend using high-quality XR5 capacitors for the output (C2, C3, and C4). Additionally, keep component leads as short as possible. If possible, use SMD components and place them close to the IC. This design uses a two-layer PCB, with one layer dedicated entirely to ground.
If you want your design to comply with EMC (Electromagnetic Compatibility) regulations, ensure that the ground of the regulator circuit and your main circuit connect at only one point. The switching currents of the power supply should not share the same ground path as the rest of the circuit.
If you’re using a single PCB for the entire circuit, be sure to place the power section away from sensitive analog components to minimize noise interference.
If you have any questions about PCB design or PCBA, please feel free to contact me at info@wellcircuits.com.
