Regulated Power Supply PCB Design Tips For Beginners

June 25, 2019 Cadence PCB Solutions

Road leading up through green hills to horizon

 

I wasn’t really a car person to start with. I didn’t realize how bumpy my ride has been until a friend I was fetching commented on it. After an overdue visit to the mechanics, it turned out that the absorbers are wearing off, partly due to my careless driving style.

Changing the absorbers put a dent to my wallet but on the plus side, now I’m surprised how smooth a car can be on the road. In a PCB, you’ll be in for a bumpy ride if you’re not taking care of the regulated power supply design. Electronics components may start complaining and refuse to function as they are supposed to.

What is a Regulated Power Supply

Without voltage, any electronics will not function. A power supply is a vital component that supplies the voltage and allows current to flow through. This activates components like IC (integrated chips), MCU (microcontrollers), and allows passive components to behave accordingly.

A power supply can be regulated or unregulated. An unregulated power supply is not guaranteed to maintain a specific voltage level during operation. This means that if you’re using a 5V unregulated power supply, there could be a fluctuation on the voltage and components powered may be affected.

On the other hand, a regulated power supply ensures that the output to the load is stable and at a level that it is rated to function. A regulated power supply is crucial in ensuring the proper functioning of electronics components. It enables components to be powered with a consistent voltage value, with the condition that the load current is within the power supply’s limit.

Linear vs Switching Regulated Power Supply

In most PCB designs, you’ll be required to include a regulated power supply module on the product. In fact, the power supply is the top priority of any designers before they started planning on other parts of the circuit. That’s because, without a reliable regulated power supply, the product will be unstable.

When it comes to a regulated power supply, designers are often torn between linear and switching regulated power supply. Both will produce the stable voltage required by the components. The linear regulated power supply is cheaper, but is inefficient and dissipates more heat.

 

A voltage regulator showing output, ground, and input

A linear voltage regulator is simple and economical, but inefficient.

 

Meanwhile, the switching regulated power supply is more expensive and requires more passive components to be connected. However, it is more efficient and doesn’t heat up easily.

The decision on opting for a linear or switching regulated power supply depends on a few factors. While the linear power supply is attractively economical, its inefficiency makes it a poor choice for circuits that demand higher power. However, simple circuits with minimal components can benefit from the linear regulated power supply design.

Useful Regulated Power Supply PCB Design Tips

In PCB design, a regulated power supply often involves a voltage regulator. While the voltage regulator could function even if some of the best practices are not adhered to, but it may not perform as well when pushed to the limit.

Here are some tips that I’ve used in every regulated power supply design on a range of different PCB designs.

1. Power Budget Calculation

Before you choose a voltage regulator for the design, you’ll want to run through every active and passive component to calculate the maximum power they will consume. This is crucial as it will ultimately affect the decision of voltage regulator selection. In other words, you wouldn’t want to end up with some pants that doesn’t fit.

 

Swathes of components on a blue circuit board

The power consumption of components affect the choice of voltage regulator.

 

2. Choosing The Right Voltage Regulator

Once you’ve ascertained the peak current consumption by the circuit, you’ll want to choose a voltage regulator that is able to support that. However, the voltage regulator is always to allow some margin so that any changes in the circuit will not affect the chosen voltage regulator. For example, if the load is estimated to consume 1.5A, having a 2A voltage regulator allows some safety barrier.

3. Bypass Capacitors

Bypass capacitors help to stabilize the output of the voltage regulator. You’ll need one when using a linear voltage regulator and even more so when using a switching regulator. That’s because switching regulator alternates between on and off state to transfer the voltage at the input to the output. Often, this can introduce ripple to the output.

4. Low Impedance

To increase the efficiency of the regulated power supply design, you’ll want to ensure the voltage regulator and its associated components are connected with low impedance trace. This means having the components close to the voltage regulator and using vias to minimize impedance between layers.

5. Heat Dissipation

When driving a substantial load, even switching voltage regulator will heat up. The temperature rise can be calculated from the temperature coefficient in the datasheet. In your design, you’ll want to mitigate heat dissipation. This can be in the form of a physical heat sink or turn your PCB into one. Using thermal vias can reduce the heat from building up in areas close to the voltage regulator.

Keep in mind, if you are considering only DC to DC conversion, then grounding as a plane is fine. But if you want to discuss AC to DC conversion, then grounding should be given high importance. There must be good separation between analog and digital ground, and jumpers must be provided in pcb design to connect grounds when required.

An advanced PCB design software helps in getting the regulated power supply design right. For instance, the Cadence's SI and PI toolsets are strong at identifying potential thermal hotspots in the design.

If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.

 

About the Author

Cadence PCB solutions is a complete front to back design tool to enable fast and efficient product creation. Cadence enables users accurately shorten design cycles to hand off to manufacturing through modern, IPC-2581 industry standard.

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