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An Overview of Power Supply Design - 2021 Updated

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Sat, Oct 10, 2020

Power supplies take the AC power from the wall socket as an input and convert it into DC power with the required voltage and current values. This process involves a significant amount of heat dissipation as well as magnetic radiation, which PCB manufacturers and designers consider when assembling a power supply PCB

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Foresee: Four Basic Types of Power Supply

Not all power supplies are the same. 

There are different kinds of power supplies, depending on their applications as well as internal working. 

Since the power supply PCB depends on the type of power supply it is being made for, let’s see what are the types of power supplies that we have and what are their characteristics.

There are four basic types of power supplies, which include:

1. Unregulated Linear Power Supply

2. Regulated Linear Power Supply

3. Ferro-resonant Power Supply

4. Switch Mode Power Supply

Unregulated Linear Power Supply

The components of an unregulated power supply include a transformer, a diode bridge rectifier, a capacitor, and an output resistor. 

This type of power supply produces a low output voltage in the form of a ripple, which is not desirable for electronic components.

An unregulated power supply, as the name suggests, produces an output voltage that does not have a fixed value. 

It produces a ripple voltage, which is not linear. 

Although you can smoothen the ripple waveform by adding a capacitor before the output terminal, it’s better to opt for a regulated power supply in that case.

Regulated Linear Power Supply

A regulated power supply produces an undisturbed DC output, which is free of ripples. 

The major difference in components, as compared to the unregulated power supply, is the addition of a voltage regulator.

The downside of using a regulated linear power supply is that the additional regulator will contribute to producing unnecessary heat, which the PCB designer needs to take care of. 

Otherwise, this type of power supply is a great option to use in electronic design because of its smooth output voltage and high reliability.

Ferro-resonant Power Supply

A Ferro resonant power supply, as the name suggests, uses a Ferro resonant transformer in place of the regular one. 

So, what is a Ferro resonant transformer? 

It is a special type of transformer that produces a regulated output. 

It focuses on online regulation and reduces harmonics.

A Ferro resonant power supply uses exactly the same components as an unregulated power supply, except the transformer. 

However, a few advantages accompany this power supply; it does not tolerate fluctuations in frequency, i.e. if the AC input frequency changes from 50Hz to 60Hz, the power supply won’t function as expected. 

Moreover, because of the addition of a Ferro resonant transformer, the overall weight of the power supply increases, which makes it heavy. 

It also produces a noise that some people might find disturbing.

Switch Mode Power Supply

The switch-mode power supply uses the most number of components, and it is the most complex power supply among the four main types. 

The components include a pair of diode bridge rectifiers, filtering capacitors, a transistor, a resistor, and a transformer.

The size of the transformer is comparatively small, which means that the overall size of the power supply is not huge. 

This type of power supply is used in special applications, and the transformer is usually custom-made.

Considerations for Power Supply PCB Design

Overall, all types of power supplies have the same function; to convert AC power into a smooth DC output to be supplied to electronic equipment. 

However, the internal working of each type of power supply is different; hence they need customized PCBs. 

The designer needs to calculate the power losses, the amount of heat dissipated, the maximum current flowing through the PCB, and the frequency of operation as well as its fluctuation, if there is any. 

All these points significantly contribute to the manufacturing process of a power supply PCB. Let’s see what are the basic considerations that need to be kept in mind for designing a fully-functional power supply PCB.

Thermal Management

Power supplies dissipate significant amounts of heat energy which need to be taken into account when designing a power supply PCB. 

Temperature one of the factors which affect the performance of electronic devices and components. 

Each component needs the right temperature to perform at its maximum capacity. 

If the temperature rises above the maximum threshold, then the electronic component will stop working or might even burn out, giving off an unappealing smell, and in extreme cases, might start a fire as well.

Hence, it is important for PCB designers and manufacturers to consider thermal management as an integral part of PCB designing and take the necessary steps to ensure that the components do not dissipate excessive heat. 

One way to cool down electronic components is to use a fan that runs on a PWM signal and blows cool air over the electronic component, reducing the overall temperature of the power supply.

Another way to manage thermal energy in power supplies is to design the PCB using multilayer boards. 

The copper layers between the multiple layers allow the heat to spread out evenly on the copper surface. 

This ensures that heat does not build up at a specific point, such as, around a capacitor or a resistor because the excessive buildup of heat would eventually damage the delicate electronic components.

Attaching heat sinks is one of the basic ways of reducing heat buildup In electronic circuits. 

The same practice can be applied in PCB designing, and each IC can have its own heat sink to prevent it from overheating.

Power Integrity

The second most important consideration for designing a good power supply PCB is power integrity. 

When current travels through the power supply components, it comes across multiple different components including ICs and transistors. 

The switching of transistors and other ICs sometimes introduces a phenomenon called "ground bounce", which means that the grounding potential of the IC is lower than the actual grounding potential of the PCB. 

This creates a difference in the ground voltages and negatively affects the amount of power received by each of the components present in the power supply.

The problem of power integrity can be solved by introducing bypassing and decoupling networks in the printed circuit board. 

These networks consist of capacitors, resistors, and inductors which work together to eliminate the ground bounce as well as unwanted frequency oscillations in the circuitry. 

The right value of capacitance, inductance, and resistance is what it takes to build these networks and allow the right amount of power to flow through the circuit components.

EMI Suppression

Electromagnetic Interference (EMI) is a source of disturbance that degrades the performance of electronic devices and circuitry. 

It is caused due to an electromagnetic device placed in the vicinity of electronic components or electronic devices. 

In power supplies, the source of EMI is the transformer; hence electromagnetic interference is inevitable when it comes to power supplies because you cannot convert an AC signal into a DC voltage, without the use of a transformer.

The output of a power supply must obviously be free from the effects of EMI, hence, a PCB designer needs to suppress EMI using filtration technique. 

Notice that the word “suppress” is being used here and not "eliminate". 

That is because you cannot completely get rid of EMI from a circuit. 

Instead, you can lower the value of electromagnetic interference such that it does not affect the performance of the power supply. 

You need to bring the value of EMI down a specified threshold value, above which the circuit suffers effects of EMI.

The EMI filter blocks the noise and directs it towards the ground, saving the circuitry from unwanted noise. 

The PCB designer needs to route the filter tracks correctly so that the energy from the filter components does not escape into the environment.

Grounding

Grounding is an essential part of electronic circuits, and it is equally important to take care of grounding in power supply PCBs. 

The ground is the return path for currents within a circuit. 

A power supply PCB has multiple current and voltage loops, and each of them requires a separate grounding system so that they do not interfere with each other.

Grounds can contain AC as well as Dc currents, hence a PCB designer must ensure that these grounds remain separated, so that the power supply functions at its best. 

Normally, three grounds join together at a point near the input, and designers need to make sure that these three grounds remain separated at all times.

As discussed in the previous section, grounding is necessary to suppress EMI. 

This is done by placing ground on either side of the traces within the PCB, and on both sides of the PCB itself. 

The high currents within the power supply circuitry end up in the grounded region, without disturbing the performance of the power supply.

Best PCBs For Power Supply

Now that we have seen the types of power supplies, it is time to understand the fact that each type of power supply requires a special type of PCB. 

thick-copper PCB

Note

PCB designers need to keep in mind the internal working of the power supply they are designing the circuit board for so that the PCB is able to handle the heat dissipated by the components as well as the variations in frequency.

The internal routing of PCBs varies with the type of power supply the circuit board is being made for. 

PCBONLINE knows exactly how to design the right PCB layout using CAD software. Our qualified team of circuit designers takes every minute detail into consideration when designing and manufacturing a PCB. Since each type of power supply requires a custom-made printed circuit board, our technicians study the working of the power supply before starting the routing and circuit design, so that we deliver the best power supply PCBs to you.

Power supply PCBs made and assembled by PCBONLINE are the best PCBs that can meet your needs. Some reasons why you choose PCBONLILNE are:

  • PCBONLINE has its own PCB factories and facility to produce power supply PCBs.
  • 100+ in-house R&D engineers and 500+ well-trained technicians are experienced in manufacturing and assembling power supply PCBs.
  • Apart from power supply PCB manufacturing and assembly, we also provide electronic components including power supply modules.
  • We can make not only heavy copper PCBs that are used for high-voltage power supply, but also PCBs that can be used for 5V, 12V, and 36V power supply.
  • All our PCBs, PCB assembly, and electronic components are compliant with ISO, RoHS, and IPC standards.

Along with advanced PCB solutions for mass production as well as retail selling for DIY projects, PCBONLINE also offers power supply modules for various needs such as small power supply modules for remote controllers (5 Volts), and larger ones for cars and other vehicles (12 Volts). With our state-of-the-art equipment and machinery, we can provide you with the best-customized power supply PCB at the best price.

Wrap It Up

Designing and assembling power supply PCBs might sound like a difficult task, but in reality, that’s not the case. It requires designers to pay attention to detail and make sure that there are no loopholes in the PCB design. If you are looking for a power supply PCB manufacturer and module provider, then PCBONLINE is the best choice you can make.