Heads up: it seems China has introduced a new safety standard for power supplies, and it will apply to not only those for use in the country, but all those manufactured there too.
Chinese Safety Standard GB 4943.1-2011, which according to industry sources is similar to UL 60950-2007, mandates strict rules for creepage and clearance. From December 1, 2012 the primary-to-secondary clearance must increase by a factor of 1.48, or otherwise carry a warning label designed to show that the equipment is not for use above 2000m in altitude.
According to Power Integrations’ Mike Matthews, the new standard will mean increased distance between high side and low side to reduce the risk of electric shock at high altitudes, specifically those between 2000 and 5000m above sea level. Electrical arcing happens more easily at the low air pressures found at elevated altitudes.
The standard puts stringent requirements on the optocouplers often used for feedback between high side and low side, meaning they have to be replaced with bigger and more expensive models. Typical consumer devices use small surface mount optocouplers on the back of the board, which the new standard will eliminate since safety distances are small. Matthews said a through-hole optocoupler would have to be used on the front of the board to get the full 9mm distance required, making the power supply a lot bigger. Or, you could switch to a supply that uses primary side regulation and thus doesn’t need an optocoupler (like one that uses Power Integrations’ LinkSwitch-HP, for example).
“This new Chinese standard has put a new twist on whether optocoupler feedback is feasible at all,” Matthews said. “Our Asian customers are telling us they are not going to go the warning label route – it makes it look like the power supply is not up to the job – they will redesign where necessary and requalify.”
The Chinese haven’t exactly been the driving force behind safety standards up to this point, but these new rules may herald a change in this department. With such a high proportion of power supplies manufactured in the country, what they say goes, so this new standard will undoubtedly affect a huge segment of the industry.