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Of all the different boards a designer can create, a high voltage PCB design can be complicated and requires strict attention to safety. If not laid out correctly these boards can be safety hazards or can fail to function on first power up, leaving a designer with wasted time and effort. In the best case, the board will function reliably for a long period of time thanks to correct layout practices.
High-voltage PCB design can be as complex as any high-speed digital design. Boards for high-voltage systems can be space constrained and they carry important safety requirements. They also need to be highly reliable to ensure they will have a long life when run at high voltage and current. With so many design demands on high voltage PCBs, layout engineers need a complete set of design tools to help them satisfy all design constraints.
Considerations in High-Voltage PCB Designs
High-voltage circuit boards are normally used in power systems, such as in power generation, conversion, or distribution. These tasks may involve a range of voltages, and the PCB for this equipment must accommodate a range of power levels simultaneously. Here are a few of the points that need to be determined before starting any high voltage PCB layout:
- Maximum voltage level: The maximum voltage level in the board will determine the relevant safety standards that need to be obeyed and the distance between conductors in the PCB layout.
- AC vs. DC power: DC power systems are more dangerous than high voltage AC systems. However, high-power AC systems may still need isolation to protect the user from dangerous currents.
- Power topology: The topology of a power system also determines safety, as well as the components that are used to build circuits for the system. Different topologies will have their own design and layout rules to ensure stable power and prevent noise from reaching downstream circuits.
- Operating temperature: The operating temperature will be a major determinant of reliability and will depend on the power dissipated in conductors and components in the system. For resistive components and the PDN in your PCB, some power drop is unavoidable and will lead to a temperature increase in the system.
The electronics industry has addressed these aspects of high voltage design and many more by creating industry standards. These standards are intended to ensure the reliability and safety of high voltage power products.
Industry Standards on High-Voltage PCB Design
Some of the important industry standards on high voltage circuit boards are the IPC 2221, IPC 2152, and IEC 60950-1 (now merged with IEC 60065-1 into the new IEC 62368-1 standard). When you have the best set of PCB design tools, the requirements in these important design standards can be encoded in your PCB project as design rules. This helps you design to the level of reliability and safety required in high voltage PCB designs.
- The IPC 2221 standard and IEC/UL standards state the required spacing between different conductors in a high-speed PCB as a function of the potential difference between them. An IPC 2221 calculator can help you automatically satisfy this standard.
- Two particular elements that need to be spaced properly in a high voltage PCB are traces and pads. Keeping these elements carefully separated prevents ESD at high voltage.
- Advanced high voltage circuit boards can be designed on a range of possible materials. Some unique materials include metal-core PCBs and ceramics.
To read this entire article, which appeared in the January 2022 issue of Design007 Magazine, click here.