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LED power supply reliability test method

Several forms of descriptors affect the output voltage of the input voltage 

⑴ regulator factor 

     ① absolute regulator coefficient K 

Said load is constant, regulated DC power supply output voltage variation than Uo input △ △ U grid voltage variation, namely K = △ Uo / △ Ui. 

② relatively regulator factor S 

Said load is constant, the relative change in the amount of regulator output DC voltage Uo △ Uo / Uo and the relative change of the input line voltage Ui of △ Ui / Ui ratio, ie S = △ Uo / Uo / △ Ui / Ui. 

⑵ grid regulation 

Represents the input line voltage on the rating change + / -10%, the relative amount of change in voltage of the power supply output voltage is sometimes expressed in absolute. 

⑶ voltage stability 

Load current to maintain any value within the rated range, the range of input voltage variations caused by the specified output voltage relative change △ Uo / Uo (percentile), called the regulator voltage stability. 

2, several indicators on the form of the output voltage of the load 

⑴ load regulation (also known as the current regulation) 

At rated grid voltage, load current varies from zero to maximum, the maximum relative change in output voltage, commonly expressed as a percentage, sometimes expressed in absolute amount of change. 

⑵ output resistance (also called the equivalent resistance or resistance) 

At rated grid voltage due to load current changes caused by the output voltage change △ IL △ Uo, the output resistance Ro = | △ Uo / △ IL | Ω. 

3, several indicators in the form of ripple voltage 

⑴ maximum ripple voltage 

At rated output voltage and load current, the output voltage ripple (including noise) of the absolute size, usually expressed in peak or RMS. 

⑵ ripple factor Y (%) 

At rated load current, RMS output DC voltage Uo Urms ratio of output ripple voltage, ie Y = Umrs / Uo x100%. 

⑶ ripple voltage rejection ratio 

The provisions of the ripple frequency (eg 50HZ), the input voltage ripple voltage Ui ~ and output voltage ripple voltage Uo ~ ratio, namely: the ripple voltage rejection ratio = Ui ~ / Uo ~. 

4, the electrical safety requirements 

⑴ power structure of the safety requirements 

① space requirements 

UL, CSA, VDE safety norms emphasized in between live parts and live parts and non-conductive parts of the surface, the space distance requirements. UL, CSA requirements: Inter-voltage 250VAC or greater between the high voltage conductor, as well as between the high voltage conductor and non-conductive parts (not included here between conductors), regardless of the surface or in the space between, there should be a distance of 0.1 inches ; VDE requires creep 3mm or 2mm clearance gap between the AC line; IEC requirements: have clearance gap between the AC line and clearance of 3mm gap between the AC line and the ground conductor of 4mm. Furthermore, VDE, IEC is required between the output and input power, the spatial separation of at least 8mm. 

② dielectric experimental test method 

Fight hypertension: input and output, input and ground, between the AC input levels. 

③ leakage current measurement 

Leakage current is the current flowing through the input side of the ground, mainly in switching power supply noise filter leakage current through the bypass capacitors. UL, CSA does not require exposed metal part shall be charged with the earth phase, the leakage current is measured by the portion of the earth with an indirect resistance 1.5kΩ, the leakage current should not be allowed to use more than 5 cents mA.VDE 1.5kΩ resistor and capacitor connected with 150nPF and 1.06 times the rated operating voltage is applied, the data processing device, the leakage current should not exceed 3.5mA, usually around 1mA. 

④ insulation resistance test 

VDE requirements: proper voltage between input and output circuit resistance 7MΩ low, and in between can come into contact with the metal part and the input resistance should be added or 500V DC voltage 2MΩ continued 1min. 

⑤ printed circuit board 

Require the use of UL 94V-2 certified material or better material. 

⑵ structural safety requirements for power transformers 

① transformer insulation 

Winding transformer used should be enameled copper wire, other metal parts should be coated with porcelain, lacquer and other insulation materials. 

② transformer dielectric strength 

In the experiment, the insulating layer breakdown and arcing phenomena should not occur. 

③ transformer insulation resistance 

Transformer winding insulation resistance between at least 10MΩ, 500 volt DC voltage is applied between the windings and core, skeleton, shield, sustained 1min, should not appear breakdown, flashover. 

④ transformer humidity resistance 

Transformer must be placed in a humid environment immediately after the insulation resistance and dielectric strength test, and meet the requirements. Humid environment in general: relative humidity of 92% (2% tolerance), the temperature stabilized at 20 ℃ to 30 ℃, 1% error tolerance, the need for at least 48h, including immediately after the above experiments. Before this time the test itself above the temperature of the transformer into the humid environment should not be higher than 4 ℃. 

⑤ VDE requirements on the temperature characteristics of the transformer. 

⑥ UL, CSA requirements on the temperature characteristics of the transformer. 

5, electromagnetic compatibility test 

Electromagnetic compatibility is the ability of a device or system in a common electromagnetic environment to work properly and does not constitute electromagnetic interference can not afford anything in that environment. 

There are two routes of transmission of electromagnetic wave interference, according to evaluate various ways. One is a long wavelength band to power line communication, a way to interfere with the emission region, generally below 30MHz. The frequency of such a longer wavelength within the length of the attached power supply line of the electronic device has a wavelength less, the amount of radiation is very little space, whereby the occurrence of the LED control voltage supply line, and thus can fully assess the size of the disturbance, this noise is called conduction noise. 

When the frequency of 30MHz or more, also becomes shorter wavelength. Then if only occur in source voltage power line noise evaluation, it does not match with the actual interference. Therefore, using a method of evaluation of the noise level of the interference wave by direct measurement of the space to the called noise radiated noise. Method of measurement methods and radiated noise are measured by the electric field intensity of the interference wave propagation space for direct measurement methods leaked to the power supply line. 

Electromagnetic compatibility tests include the following test content: 

① magnetic field sensitivity 

(Immunity) equipment, subsystems or systems exposed to electromagnetic radiation unwanted responsiveness. The sensitivity level, the higher the sensitivity, immunity worse. Including fixed frequency, peak magnetic field testing. 

② Electrostatic Discharge Sensitivity 

Objects have different electrostatic potentials near or in direct contact with each other due to charge transfer. Charging 300PF capacitor to-15000V, through 500Ω resistor discharges. Be super bad, but put to normal after. After testing, data transfer, storage can not be lost. 

③ LED Power Supply Transient Sensitivity 

Including spikes sensitivity (0.5μs, 10μs 2 times), the voltage transient sensitivity (10% -30%, 30S recovery), the frequency of transient sensitivity (5% -10%, 30S recovery). 

④ radiation sensitivity 

Cause the device to measure radiation interference field downgrade. (14kHz-1GHz, the electric field strength of 1V / M). 

⑤ Conducted Susceptibility 

When the device that causes undesirable response or cause performance degradation when the interference power, control or signal line signal or voltage measurement. (30Hz-50kHz/3V, 50kHz -400MHz/1V). 

⑥ non-working state magnetic interference 

Box 4.6m, the magnetic flux density is less than 0.525μT; 0.9m, 0.525μT. 

⑦ operating magnetic field interference 

Upper, lower, left and right AC flux density is less than 0.5mT. 

⑧ conducted interference disturbances propagating along the conductor. 10kHz-30MHz, 60 (48) dBμV. 

⑨ radiation interference: electromagnetic wave propagating through space in the form of electromagnetic interference. 10kHz-1000MHz, 30 shielded room 60 (54) μV / m.



Post time: Aug-06-2016

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