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Chinese safety spec may be de facto global standard

25 июля 2012

A new Chinese safety standard set to go into effect Dec. 1 could essentially become a de facto global standard for power supplies, since the vast majority of all power supplies are now manufactured there.

The standard, GB 4943.1-2011, mandates the use of warning labels on power supplies that do not meet strict creepage and clearance rules. Similar to another standard created by product safety certification organization Underwriters Laboratories Inc., UL 60950-2007, the Chinese standard requires designers to increase the primary-to-secondary clearance by a factor of 1.48 for power supplies used in equipment at altitudes exceeding 2,000 meters (6,562 feet) or add a warning label stating that it should not be used above that altitude.

Electronics vendors are loathe to add warning labels to products for a number of reasons. For starters, anyone who lives or travels to high altitudes would be less likely to buy a product that is not intended for use above 6,562 feet. Also, placing a warning label on the product would take up valuable space that companies typically prefer to use for their own marketing. And any warning label is likely to decrease consumer confidence in the safety of the product at some level.  

"Nobody wants to put a sticker on their box that says, 'Don't use above 2,000 meters,' " said Doug Bailey, vice president of marketing at Power Integrations Inc. Power Integrations introduced Tuesday (July 24) a new family of energy-efficient, off-line switcher ICs that can help designers of lower-power charges for mobile phones and other products comply with the new Chinese standard.

At high altitudes, where the air is thinner and typically less humid, there is a higher danger of sparking across the standard spark gap used to protect against voltage surges. China contains several populated regions at altitudes over 2,000 meters.  

"The Chinese have put in place what is for all practical purposes a stricter standard than the rest of the world," Bailey said. According to Bailey, few people in the West appear to be aware of the new standard or its ramifications. Since virtually all power supplies are built in China, they will have to comply with the standard or apply the warning sticker, he said.

Bailey said designers can redesign their power supplies to meet the Chinese standard by adding a larger gap, but that would also require adding a more powerful and more expensive opto-coupler. "If you are going to do a redesign, the simple thing is to buy a bigger opto," Bailey said. "But a better way, in our opinion, is to buy our chip."

Power Integrations' LinkSwitch-HP ICs use control algorithms and the properties of the main power transformer and output diode—rather than optocouplers and related feedback circuitry—to determine the amount of power to deliver from the primary to the isolated secondary side. According to Bailey, this method reduces component count, saving space and cost while also enhancing reliability.

Power Integrations' primary-side regulation (PSR) was popularized more than a decade ago for higher power applications. According to the company, the LinkSwitch-HP devices also feature a multi-mode control architecture that radically advances the state of the art for PSR, making it a viable approach for power-supply applications from 9 W to 90 W.

LinkSwitch-HP devices automatically select their control mode according to prevailing line and load conditions to optimize conversion efficiency and response to transient load demands, while minimizing output ripple and audible noise, according to the company. Continuous-conduction-mode (CCM) operation results in reduced RMS currents, leading to higher efficiency and less heat dissipation, while 132 kHz, full-load operating frequency enables the use of smaller magnetics and LC post-filter components, the company said.

LinkSwitch-HP ICs are also capable of no-load power consumption of less than 30 mW at 230 VAC and are more than 50 percent efficient at 0.1 W input power, meeting all global energy efficiency regulations for external power supplies, according to the company.

Sampling now, the LinkSwitch-HP devices are offered in two different package options: eSIP-7C and eDIP-12B, starting at 42 cents each in 10,000-piece quantities (LNK6763V), according to Power Integrations. Two supporting evaluation demo boards are available upon request, the company said.

By Dylan McGrath

Источник: EETimes.com

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