EcoSmart C5A19A60WESD04 LED bulb

The EcoSmart C5A19A60WESD04 LED bulb is rated at 8.5w and 800 lumens light output equivalent to a 60W incandescent bulb. There are 9 upward facing LEDs mounted on a PCB bonded to an aluminum heat sink disk. The heat sink/PCB assembly is crimped to an additional aluminum disk which is pressed into a cylindrical cone shaped aluminum heat sink within the A19 base.

A single sided printed circuit board inside the A19 base provides AC to DC conversion. On one side of the board larger through-hole components such as inductors and capacitors are located. On the other printed side the surface mounted components are located. The semiconductor content of this product includes a diode bridge, a switching diode, a high voltage MOSFET and an iWatt (now Dialog Semiconductor) iW3681 integrated circuit controller in an 8-pin package. The AC to DC conversion circuit connects to the LED assembly through a 2-pin connector.

The circuit is a non-isolated buck-boost converter that generates a DC voltage for driving the LEDs from the full wave rectified 120 volt AC input. The rectified AC is not directly filtered to an intermediate DC voltage because this would require a large capacitor. Instead, the full wave rectified AC voltage varying from 0 to approximately 170 volts peak is fed through a passive LC filter to block high frequencies and provided directly to the switching regulator consisting of an inductor, diode, a large electrolytic output capacitor, high voltage MOSFET and the controller IC. The high voltage MOSFET limits the voltage applied to the controller IC so that the switching transistor within the IC does not have to withstand the full peak line voltage. The gate of the MOSFET is biased a constant DC voltage through a zener diode circuit. The use of an external high voltage MOSFET allows the controller IC to be manufactured with a lower cost technology. Safety is provided by a 30 ohm fuse resistor at the AC input. There is no transient protection such as a varistor which is found in many similar products.

A polar coordinate graph shows the light intensity of the EcoSmart C5A19A60WESD04 at 4 different power levels adjusted with a triac dimmer. 0 degrees is the top of the bulb and 180 degrees is the base of the bulb where the light is completely blocked. Full power intensity shows a maximum of 4500 lux at and sharp drop off at +/-90 degrees. Integrating intensity over the entire surface gives a total light output of 630 lumens, short of the rated 800 lumens. However a 60W incandescent light bulb provided only 400 lumens under the same measurement conditions so there is probably a significant calibration error. Power consumption was measured at 9 watts, slightly exceeding the rated power consumption. Energy efficiency of the bulb can be calculated by converting lumens to watts on the basis of the photopic luminosity function (683 lumens/watt) which approximates the range of wavelengths visible to the human eye at normal intensities. The EcoSmart C5A19A60WESD04 efficiency in converting electrical power to optical power at visible wavelengths is calculated at 10.2% under full power. For comparison the 60W incandescent bulb is calculated at only 1.0% efficiency.