LED plate analysis – D44-22P-01

The D44-22P-01 is a Chinese LED plate rated at 15W and operates directly from 230VAC with an integrated driver.

It was purchased to explore the configuration of LEDs with integrated driver, and this driver looks deceptively simple.

The chips are JZ1009AE, a LED current driver. The 22 2835 LEDs are 9V LEDs for a string voltage of 200V.

Above is a schematic from the chip datasheet, the two chip configuration is for load sharing. This board is essentially that, but they save one capacitor. There is a total absence of effective RFI mitigation.

The plate was powered on 230VAC (nominal) in free cool air (12°) and whilst initially reading 15W, within a minute is was down to 10W whilst temperature of the plate reached 107°.

The extreme temperature is not surprising, this plate has about 12% of the surface area of the common 15W annular LED plate,  and also contains the LED driver.

Above the power meter reading after one minute.

Thermographs

Above is a thermograph after a minute operation. The LEDs are on and the image is affected by the LED switching. This is too hot to safely fit to most light fittings, especially unvented ones.

Two minutes after switching off, the LED plate is 76°.

Current measurement

Above is screen capture of current measurement on the AC line at switch on. The probe factor is 1mV/10mA, so the current is about zero until the driver switches on and current is regulated to about 100mA for almost 6ms in each half cycle, so Iav=100*6/10=60mA and with a string voltage of 200V, about 12W input.

Above is the current after 10s operation, the current in each half cycle starts at 100mA as in the cold capture above, but rapidly falls so reducing the average current. This explains the collapse under sustained operation discussed earlier.

Above is a plot of instantaneous regulator voltage and current over a 90° of the AC cycle. A quick calc supplied AC of 254Vrms (the maximum for our nominally 230Vrms supply) shows that peak instantaneous regulator dissipation is 16W, but average dissipation over the quarter cycle is 6.5W whilst average LED power is 12.6W.

What a green fraud!

Conclusions

Cheap Chinese junk.