Multi-Function LED Lamps with Built-In Wireless Chargers
Tom Lombardo posted on July 30, 2019 |

Engineering.com has examined LED lighting from the standpoint of safety, light quality, energy efficiency, and sustainable design, so now let’s take a look at the features and underlying technology of some commercial LED-based lamps. Brightech manufactures LED lighting systems for homes and small offices. Several of its products feature added conveniences such as USB ports and wireless pads that charge cell phones, tablets and other battery-powered devices. We’ll examine just two of Brightech’s lamps (see Figures 1, 2, and 3), as the others share the same basic technology.

Figure 1. Two of Brightech’s lamps. (Image courtesy of Brightech.)
Figure 1. Two of Brightech’s lamps. (Image courtesy of Brightech.)


Features and Specifications

Two Brightech lamps that provide wireless charging pads and USB ports are the Grace Table Lamp and the Madison Nightstand Lamp. Both include LED bulbs that screw into an E26 base (the same socket as a standard incandescent light bulb) and provide 800 lumens of light—about the same as a 60W incandescent bulb. The LED bulbs, however, consume less than one-sixth of the power (9.5W) compared to their Edison-created counterparts. While incandescent bulbs, which convert most of the incoming electricity into heat rather than light, struggle to deliver efficacies of 13 lumens per watt (lm/w), Brightech’s LED lights come through at a cool and efficient 85 lm/w. 

These lamps both come with warm white bulbs (3000K color temperature), which provide a comfortable ambiance but are less than ideal for reading or task lighting. Since the bulbs fit into a standard socket, they can be replaced if the customer prefers a different color temperature or if the bulb burns out. The company says that the bulbs should last for 20,000 hours (about 20 years if used for 3 hours per day) and offers a five-year warranty on its products. 

Figure 2. More details on the Grace Table Lamp. (Image courtesy of Brightech.)
Figure 2. More details on the Grace Table Lamp. (Image courtesy of Brightech.)

LED Technology

The Brightech LightPro LED Bulbs in these lamps consist of surface-mount LEDs surrounded by an aluminum housing that’s engineered to enhance convective currents, which helps to dissipate the heat generated by the control circuitry. The LEDs emit white light; a phosphor coating tunes the color temperature to a warm 3000K. The company also offers cool white lamps that use blue LEDs with a different phosphor coating to provide a 6000K color temperature (better suited for office and task lighting), and a few lamps whose color temperatures can vary using tri-color LEDs.

Figure 3. More details on the Madison Nightstand. (Image courtesy of Brightech.)
Figure 3. More details on the Madison Nightstand. (Image courtesy of Brightech.)


Charging Technology and the Qi Specification

Each lamp comes with USB ports capable of delivering 5 Watts at 1 Amp (see Figure 4). That’s enough to charge a 3000 mAh battery in about three hours. The wireless charging pad delivers the same amount of power using the Qi wireless power transfer specification. Although wireless charging is slightly less efficient than charging through a cable, for low-power applications like phones and tablets, the power loss is insignificant.

Figure 4. Wireless charging with Brightech lamps. (Image courtesy of Brightech.)
Figure 4. Wireless charging with Brightech lamps. (Image courtesy of Brightech.)

Wireless charging involves two coils in close proximity that are magnetically coupled. Alternating current is sent to the transmitting coil, which generates a magnetic field that expands and contracts in proportion to the current (see Figure 5). As the magnetic field oscillates, the magnetic flux cuts across the wires in the receiving coil, inducing an alternating current in the coil. The current is then rectified, regulated, and sent to a charge controller, which ensures that the battery receives a constant current during the early stages and a constant voltage during the later stages of charging. The charge controller also prevents the battery from overcharging. 

Figure 5. Wireless charging using electromagnetic induction. (Image courtesy of the Wireless Power Consortium.)
Figure 5. Wireless charging using electromagnetic induction. (Image courtesy of the Wireless Power Consortium.)


As part of the Qi specification, when a device is placed on the charging pad, the transmitter senses the object by one of two methods: noticing a change in surface capacitance or detecting a shift in the transmitting circuit’s resonant frequency. Once the object is identified as a chargeable device, the transmitter (PTx) and receiver (PRx) communicate to determine the device battery’s state of charge and charging requirements. This ensures that the charger will deliver the appropriate charging levels for the correct period of time. 

For safety, the pad senses when a foreign object is placed near the coil during a charge cycle. If it detects that the foreign object is being heated by the magnetic field, the transmitter will terminate the power delivery. 

Sustainable Design

Saving energy is one aspect of sustainability, but reducing material waste is equally important. Although some of the products in Brightech’s catalog don’t include replaceable bulbs, the models featured in this article do—a definite plus from a sustainability standpoint. In addition, the base of each lamp is made of real wood rather than plastic. I’d like to see all of the company’s light fixtures made with bulbs and other components that are field replaceable. Hopefully, Brightech’s engineers will find a way to ensure that these products don’t end up in a landfill at the end of their lives.

The Future Is Bright

Like most new technologies, LED lighting suffered through a few difficult years while engineers struggled to keep the control circuitry cool and reliable. It also took a while to figure out how to design bulbs that emit color temperatures that are safe, aesthetically pleasing, and appropriate for specific applications. Early adopters saw some duds, but LED technology has finally matured enough to become the standard for nearly all lighting systems. Now let’s work on making them more sustainable.

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