LED drive RMS value measurement and analysis

- Oct 12, 2018-

LED drive RMS value measurement and analysis


It is well known that the quality of LED lighting products depends on two aspects: one is the LED chip chip light source; the other is the LED driver power supply. At present, there are mainly a few well-known companies such as PHILIP, OSRAM and CREE, which are capable of providing high-quality qualified LED chips. In general, LED chips rarely have major quality problems, and now the poor quality LED lighting products on the market are very large. Part of it is on the drive power. In view of the importance of LED driver power, this article mainly discusses some common technical descriptions in LED driver power supply measurement and measurement.

For LED drive measurement, there are several necessary test items such as crest factor, effective power, reactive power, apparent power, power factor, voltage/current (RMS rms, average), and THD harmonic parameters. In the actual measurement process, many people find that the test data they get on the test equipment and the data obtained by their own power meter or multimeter are quite different. The controversy is reflected in the voltage/current RMS value. Power, power factor, RMS rms, and average. Many customers have reported that they have used their own voltage meter or multimeter to test the voltage/power supply (RMS value) and the parameters obtained on the drive power test equipment. Here are all the data displayed on the drive tester. It is the true effective value of RMS. Generally speaking, the average current is also the average value of RMS. The average current is only available when the test is started and is the average current of RMS during startup. The data on the software is consistent with the instrument data.

At the same time, testing the drive power according to international standards is to test the true RMS value; the test average is meaningless. The voltage, current and power displayed on the tester are driven, but the voltage multiplied by the current is not the power; the value obtained by directly multiplying the voltage by the current is the apparent power, and the driving tester measures the active power. If you only test the average, then the test equipment has no meaning, you can test the value with a simple multimeter.

According to the IEC standard, the voltage true rms (Urms), the current true rms (Irms), the active power (P), and the power factor (PF) are calculated as follows:


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In the actual test process, when judging whether the LED constant current drive output current is using RMS real value or average value to measure the driving power quality, there are two different sounds on the market: some are judged by RMS value, but some also The average value is evaluated. This is mainly because the LED constant current drive output current ripple is large, and the characteristics of each drive power supply are different. At this time, the RMS value and the average value of the output current will vary greatly, but from the actual situation. If it is judged by the test standard requirements, it is the only criterion to judge whether the driving power supply is good or not, and whether it depends on the true RMS value of the RMS. If we only judge from the RMS mean that it seems a bit sloppy and does not represent the actual situation, we can refer to the average but never as a measure.