China's Minister of Information and Industry (MII) announced last Dec the "Technical Requirements and Test Method of Charger and Interface for Mobile Telecommunication Terminal Equipment" (YD/ T 1591-2006). Starting from the 14 of June 2007, all new mobile phones requesting for network access approval in China, will have to adopt the new battery charger interface standard described in the regulation. This is the government's effort to reduce the number of power adapters that become redundant due to the upgrade of equipment and thereby reduce the impact of the abandoned electronic parts on the environment and the waste of natural resources.
China is no longer just the largest mobile phone production country in the world; it is also a large consumer of new phones through new subscription and renewal. According to MII, China consumed about 100,000,000 units of handset in renewal each year and it is growing. Some initial saving may be transferred to the consumer, as they will not need to pay for a power adapter with each new handset purchased. Expecting the old, customized battery charger will be gradually replaced with new universal ones. This may even bring in new business opportunities for adapter makers.
As the battery charger is no longer equipped with special connector with different power characteristics customized to each mobile phone manufacturer. Instead, charger will be equipped with a standard USB Type A plug and the output power is regulated to ensure that it can be used across all new handsets. Battery charger that is compliant to the new regulation should request for the certification from China Telecommunication Technology Laboratory (CTTL) of MII. As of 31 May 2007, CTTL has already certified 15 mobile phone charger models from 14 companies, which consist of mostly Chinese phone suppliers. For non-Chinese phone suppliers with an international market, their chargers are standardized for different phone models selling in different countries, it may take them some more time to change it.
Electrical characteristics of USB charger interface
The new regulation requires all handsets to provide a USB interface for battery charging and data transmission purpose. It is however flexible for the phone vendor to decide on the interface on the handset itself. If it is not compliant to the USB type A connector standard, an adapter cable with USB connectivity will have to be provided. With this USB interface in place, not only handsets could be recharged by universal chargers; mobile phone can also be recharged by other USB hosts such as notebook PC. A great news for business travelers in China, as they can slightly lighten their baggage loading.
The output voltage characteristic is defined by the new regulation. The nominal output voltage of the charger should be 5 V with a +/-5% tolerance; that means, the input voltage to the mobile phone connector should remain between 4.75 V to 5.25 V. Moreover, a handset should limit its maximum input current to 1.8 A. The Lithium-ion or Lithium-polymer battery pack rating remains around 900 mAh today, thus requiring a charge current of less than 1A. However, to set a higher input current limit to 1.8A leaves room for development. As the charge current is expected to increase in the foreseeable future, as new battery pack with higher capacity will be needed to support the power consuming multimedia functions in new 3G handsets.
As mentioned before, a USB host can be connected to the USB interface on handset either for battery charging or data transmission purpose. How can the handset distinguish a USB port from a power adapter and be able to select the right input current limit? The regulation requires that the power adapter to have both D+ and D- line be shorted together inside the charger. When the data lines are not shorted, the handset will recognize that the source is a USB port and thus will limit the input current to maximum 500mA in order to conform to the USB standard.