China takes the initiative with new safety legislation

Author : Alistair Winning

24 July 2012

Alistair Winning
Alistair Winning

From 1st December this year, GB 4943.1-2011 will come into force in China.

The new standard ensures equipment is suitable for use in altitudes up to 5000m instead of the current global standard of 2000m. Non conforming equipment must be clearly labelled as such.

This is not the first standard that China has introduced. But what is different this time is that the new legislation is stricter than existing global legislation and it also applies to all mains power supplies manufactured in China; not just to those for sale to the Chinese domestic market.

The main reasons for the extension to the altitude the regulation covers is to compensate for reduced air densities at higher altitudes, which leads to lower air breakdown voltages and an increased temperature rise. The new legislation defines the creepages and clearances required in designs with an increase to the primary-to-secondary clearance by a factor of 1.48.

Getting information on the new legislation could be quite difficult and from the discussions that I found online, there is some debate as to whether optocoupler clearances are included in the legislation. It they are it would probably require new designs to use pin-through-hole components rather than the surface mount components now used to meet the new clearance figures.

To meet GB 4943.1-2011, Power Integrations has extended its LinkSwitch range with the HP series. The new LinkSwitch devices deliver up to 90 W output power with accurate primary-side regulation (PSR). The devices also feature an automatic multi-mode control architecture that allows four different switching frequencies depending on the load.

Power Integrations has managed to sidestep the optocoupler debate by omitting the device from the design altogether. This also has the benefit of making the design cheaper and less complex. Instead of the optocoupler and supporting components, the company has designed a circuit that uses properties of the main power transformer and output diode along with innovative control algorithms to determine the power to be delivered from the primary to the secondary side.

The LinkSwitch-HP ICs are capable of no-load power consumption of less than 30mW at 230 V AC and are more than 50% efficient at 0.1 W input power, meeting all global energy efficiency regulations such as ErP (EuP), ENERGY STAR EPS V2.0 and EC Ecodesign Directive Tier 2 for external power supplies. LinkSwitch-HP ICs also feature a comprehensive protection suite.

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