IEC 62684:2011 pdf free download – Interoperability specifications of common external power supply (EPS) for usewith data-enabled mobile telephones
6.1General
The requirements in Clause 5 have been developed to try to ensure that common EPsperform correctly with any data enabled mobile phone to which they may be connected.Mostof the requirements can be verified using existing and well understood measurementtechniques which do not need defining in this International Standard.
The common mode voltage and ripple voltage at the DC output can be affected by the load onthe output of the EPS.For these parameters, the following test procedures shall be used.
6.2Common mode voltage of the Dc output
a) The EPS shall be connected to an AC power source wherein one or the other of the AC mains is a neutral conductor, bonded to earth either at the upstream service transformer,or locally in the laboratory environment.
Rationale
1) In most installations, it is required that one or the other of the AC mains is bonded to earth at the upstream service transformer，and is termed the “neutral” or”return”conductor; and
2) common-mode noise is manifested to the greatest extent when one or the other of AC mains is bonded as such.
NOTE Many synthesized AC power supplies produce isolated AC outputs with no connection to earth.Common-mode noise measurements are reduced is such situations,since the EPS common-mode noisesource has no real ground reference. Therefore，isolated AC outputs should have one or the other of theoutput lines bonded to local ground or neutral. Similar considerations exist when using variableautotransformers to produce the required AC line voltage.
While the amplitude and frequency of common-mode noise produced by a given EPS willdynamically change over the operational modes and battery charging cycle, it is necessaryto create a common test load which will give repeatable measurements.The resistiveportion of the load will cause a certain frequency and amplitude of common-mode noisefrom a given EPS,while the uSB cable and simulated mobile terminal contribute adistributed shunt capacitance to earth，which in normal use，serves to attenuate thecommon mode noise, as in a capacitive AC voltage divider. Without this latter provision,any common mode noise test is generally too restrictive,and is not realistic. d) The common-mode noise waveform shall be measured at the GND terminal of the UsB Micro-B plug.The sampling probe shall have an input impedance of 10 M in parallel with8pF. Rationale Common-mode noise is that electrical signal present at the output negative conductor withrespect to earth.The probe impedance, as well as shunt capacitance to the test bench,does artificially load,and therefore attenuate, the measured common-mode noise.
6.3 Ripple voltage at the Dc output
a) The USB Micro-B plug of the EPS shall be connected to a load representative of a mobile phone with the following characteristics:
– uSB Micro-B receptacle connection;
– a capacitance of (1±0,1) uF between the Vbus and GND terminals of the uSB Micro-B receptacle. This capacitance shall have a typical ESR of 0,01 Q at 1 MHz and0,6Q at 10 kHz;
– a variable or switchable resistance between the Vbus and GND terminals of the USBMicro-B receptacle. lt shall be possible to select a resistance of 10 kQ to simulate a noload condition and other resistances suitable to draw 25 %，50 %，75 % and 100 % ofthe rated current of the EPS.
b) Place EUT into an environmental chamber. c) Connect and oscilloscope to the Vbus and GND terminals. Set the oscilloscope to 20 mV/div, 1 s.div and 20 MHz bandwidth. d)Allow the temperature of the EPS to stabilize for at least 10 min. e) Turn on the AC power to the EPS and allow