High Power PCB Design Guidelines
As a pretty important process of PCB manufacturing, PCB design is facing challenges and also necessary for engineers and manufacturers, especially when they are dealing with the high-power PCB. As the size of electronic devices is continuously and progressively reducing, design aspects such as power supply and thermal management must be taken into due consideration.
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In this article, we will tell you everything about the high-power PCB design, and if you are interested in the topic, welcome to check and read the content we prepare below for more professional knowledge.
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What are the features of high-power PCB?
In electronics, high-power PCBs usually conduct current that goes beyond a couple of Amps. An electrical motor driver, which could channel 30A of current within the circuit, is considered a high-power PCB. The same goes for an LED driver, which could be driving hundreds of LEDs configured in arrays.
There isn’t a strict definition of what qualifies as a high-power PCB. Power can be defined by P=IV, and a high power design could mean a circuit that consists of elements of high voltage or current. Instead of placing a strict definition on the parameters, it is easier to categorize high-power PCBs by things that may arise if proper high-power PCB design practices are not followed: thermal generation and electrical shocks.
What are the advantages of high-power PCB for environment?
In 2009, the IPC-2152 Standard for Determining Current-carrying Capacity in Printed Board Design was released. This standard for relating trace width, copper weight and current carrying capacity replaced the long-standing and still often used the IPC-2221A standard. Based upon the guidelines of these standards, attempts to develop a reliable means of determining these parameters for high current PCBs have been made culminating in a number of on-line trace-width calculators.
Most circuit boards process or transfer low power signals for digital, RF or power circuitry. For these applications, copper weights of 1oz or 2oz carrying currents in the mA to tens of amps range are typically sufficient. For some industries, such as military and aerospace, medical systems, automotive and industrial production, PCBs must have traces that are capable of carrying hundreds or thousands of amps. For these boards, trace widths must be much wider or copper weights must be higher.
The typical approach to high current demands is to widen relatively thin (≤ 2oz) copper traces, which requires additional space on the surface and layers. However, the use of heavy or extreme copper routing has distinct advantages over that approach, including the following:
· Greater trace current carry capacity
· Greater via current carrying capacity
· Accommodation of different circuit current levels on the same layer or PDN
· Does not require increased trace widths
· High reliability
· Good mechanical strength at connectors
· Utilization of high-temperature components without risk
What are the considerations of high-power PCB design?
Safety consideration
As with any circuit, the primary concern with a high current circuit is ensuring that it operates safely. There are a few potential issues that are unique with boards that drive such high powered loads. The main hazard is heat. No matter how well you design and lay out the board, more heat is produced than with a standard board. This must always be considered when the housing is made, and external vents/fans should be used.
Something that I do on ALL designs that drive more than a few amps, is to have a dedicated temperature sensor on the PCB quote. This is a great firmware based failsafe. With the ability to monitor the temperature, you should always be able to react to any situation of overheating. To reduce the amount of heat produced on the board itself, it is best to choose components with low resistance.
The next potential safety hazard is regarding short circuits. Since the board is designed to drive high power devices, when shorted, it will be able to source a considerable amount of current. It is crucial to consider this possibility in the design phase. The easiest way to deal with shorts is to have a fuse on ALL outputs that leave the board, and an input fuse. The fuses should always be rated for less current than the wires used can handle.
Thermal management
Thermal management techniques, or the lack of, can determine the fate of a high-power PCB design. A heatsink is preferable when you’re dealing with high-current components like a MOSFET.
However, the decreasing size of a PCB may limit the space for a heatsink. In such cases, you’ll need to make use of techniques like pouring solid copper around the heat pad of a MOSFET and creating an array of thermal vias to spread out the heat. You may also want to consider active thermal dissipation techniques such as installing a cooling fan or liquid cooling system for high-power components.
Component placement
Often, a high-power PCB consists of components that generate excessive heat. Power MOSFETs, regulators, and associated passive components can produce a huge amount of heat as a high current passes through.
As board size gets smaller, how and where you place components becomes more critical. In modern designs, where you place your components determines the effectiveness of heat dissipation. It is a good practice to place heat-generating components in a group and near the edge of the board. Avoid placing components like a power MOSFET near to temperature-sensitive components like amplifiers and converters.
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PCB Knowledge ⋅ 09/06/2021 09:50
