Philips 9290011840 LED bulb

The Philips 9290011840 LED bulb is rated at 9.5w and 800 lumens light output equivalent to a 60W incandescent bulb. There are 26 LEDs mounted on a flexible PCB wrapped around a pentagonal aluminum heat sink to provide light in all directions except towards the base. 20 large LEDs arranged in 2 strings of 10 deliver the full power light output. At low levels of dimming control the large LEDs turn off and 6 small LEDs turn on to provide the "warm glow" feature with a lower colour temperature to mimic the behavior of an incandescent bulb. The pentagonal heat sink is pressed into an additional aluminum heat sink within the A19 base.

A single sided printed circuit board within the pentagonal heat sink and the A19 base provides AC to DC conversion. On one side of the board larger through-hole components such as transformer, inductor and capacitors are located. On the other printed side the surface mounted components are located. The semiconductor content of this product consists entirely of discrete components such as diodes, a diode bridge, bipolar transistors, and a silicon controlled rectifier. There are no integrated circuits. The AC to DC conversion circuit connects to the flexible LED assembly through a 3-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 NPN switch transistor, transformer, diode, and large electrolytic output capacitor. The switching regulator switches at a much higher frequency than the 60Hz input, and adjusts the switch duty cycle based on the input voltage to maintain output current through most of the 60Hz period. The transformer secondary is not used for isolation, but controls the base emitter-voltage of the main switch transistor via a 3-transistor clamp circuit. The DC output section includes an transient over-voltage protection circuit employing an SCR and zener diode. This is provided in addition to the 270v varistor and 33 ohm fuse resistor at the AC input. Finally, a 3-transistor circuit detects when the output voltage drops below a certain level as dimming control is applied to turn on the smaller LED string for "warm glow" operation.

The Philips circuit features a higher component count than similar 60W replacement LED bulbs. Part of this is due to the increased complexity of the "warm glow" feature. However, a larger number of LEDs and additional transient protection circuitry should result in higher reliability and longer life.

A polar coordinate graph shows the light intensity of the Philips 9290011840 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 4000 lux at +/-90 degrees and a local minimum of 2200 lux at 0 degrees. This pattern is due to the 3-dimensional LED mounting arrangement and resembles that of an incandescent bulb. At lower power levels the light intensity drops off significantly. This is due to the "warm-glow" feature switch-over to the smaller LED string and wasted power in the 18 ohm series resistors. Integrating full power intensity over the entire surface gives a total light output of 600 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 10.2 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 Philips 9290011840 efficiency in converting electrical power to optical power at visible wavelengths is calculated at 8.6% under full power. For comparison the 60W incandescent bulb is calculated at only 1.0% efficiency.