How does the phone charger work?

PowerbyProxi was founded in 2007 by entrepreneur Fady Mishriki as a spin-out from the University of Auckland. PowerByProxi has showcased charging boxes and bowls into which multiple devices can be placed and charged at the same time.

The Aukland-based company got its start selling large-scale systems for the  construction, telecommunications, defense and agriculture industries. One such  product is a wireless control system for wind turbines.

PowerByProxi, a member of the WPC’s Steering Committee, has also miniaturized its technology and placed it into AA rechargeable batteries, eliminating the need to embed the technology directly into devices. The wireless technology takes up about 10% of the AA battery height.

Apple could use PowerByProxi’s technology to expand its use fo wireless charging beyond just smartphones, using it, for instance, to charge TV remote controls, computer peripherals, or any number of devices that require batteries.

While the most visible use of wireless charging technology has been in mobile device charging pads, the technology is also making inroads into everything from warehouse robots to tiny IoT devices that otherwise would need to be wired or powered by replaceable batteries.

Both Ossia and Energous have demonstrated wireless charging beyond 15 feet. Ossia’s charger can send about two watts up to several feet, but that drops off quickly as the distance increases. Even at 30 feet, however, the amount of power that can be transmitted is “meaningful,” according to Ossia CEO Mario Obeidat, alluding to trickle powering devices so as to maintain their charge.

The Ossia Cota wireless power system includes this large cylindrical transmitter as well as receivers. 

“Let’s say I’m in an office for eight to 10 hours a day and I’m receiving a half a watt or a watt of power; it’s charging my device all the time,” Obeidat said. “So if it takes five hours to fully charge that devise, that’s fine because you’re there all the time.”

“I’ve used both [Ossia and Energous]; the technology works,” Rob Rueckert, the managing director at Sorenson Capital, a private equity and venture capital firm, said in an earlier interview with Computerworld.

Rueckert believes charging at distance is a more compelling technology than charging pads or even boxes that still require a mobile devices to be relatively tightly connected to a charging source.

How wireless charging works.

Both Energous’ WattUp and Ossia’s Cota mobile device charging systems work much like a wireless router, sending radio frequency (RF) signals that can be received by enabled wearables and mobile phones. A small RF antenna in the form of PCB board, an ASIC and software make up the wireless power receivers.

Using a multi-antenna management chip about 4x4mm in size, the Cota power transmitter can be built into a variety of form factors, everything from ceiling tiles to  tables, desks, glass, televisions and automobile dashboards.

The transmitter automatically detects Cota-enabled devices and includes a temperature-sensing unit to prevent overheating.

“We call it real wireless power,” Obeidat said. “The difference between our technology and others in market, like Qi, is we can deliver meaningful power remotely. Others require you to place your device on the pad. So, effectively you have to give up the device to charge it.”

Obeidat also claims Cota charging can work through walls, just like a Wi-Fi router.

“Our technology is agnostic. You can envision having a transmitter in room where it powers a smartphone, a tablet or a smart watch, all at the same time,” Obeidat said.

Ossia has been piloting its technology on electronic labels for products on retail shelves. The labels can inform shoppers of product details or sales without requiring workers to place physical signs or change price stickers.

While some have scoffed at the idea of only transmitting a couple of watts of power over distance, investors have taken the idea seriously. For example, Pleasanton, Calif.-based Energous – an AirFuel member – raised about $25 million when it went public in 2014.

Energous’ WattUp charger uses the Bluetooth wireless communication spec. Like Ossia’s Cota technology, the amount of wattage WattUp can send is limited. As a result, Energous is focused on powering small mobile devices rather than laptops or batteries that require higher capacities.

Michael Leabman, founder and CTO of Energous, demonstrates how one of the company’s wireless charging routers can send power at midrange and far-range distances.

A single WattUp transmitter can charge up to 24 devices, all under software control that enables or disables charging, according to Energous. The maximum amount of power – 4 watts – can only be delivered to four devices simultaneously. As more “authorized” devices enter a room, the charge to each device drops.

One potential obstacle to adoption of wireless charging at distance is that neither Ossia’s nor Energous’ can charge Qi-enabled devices; the technology is proprietary.

Only the beginning

Green believes Qi and Powermat provide a great start, but stresses the technology  isn’t completely wireless. “Qi has started the conversation about wireless power. There is an important need to educate consumers about what is possible,” he said.

By starting with a Qi pad charging, users can begin to accept the premise of wireless power and will soon demand a much more flexible, robust solution: power at a distance with the flexibility to use your device while charging.

“One thing is clear: in 2017, we’re not going to see a device offering full-speed wireless charging across a room,” Green said. “There’s two ends of a scale instead, charging at the same speed as a wire but on a charging pad, or perhaps trickle charging very slowly but at a larger distance away.”

Mobile phones are very common these days and so mobile chargers too. Most of us use it in daily life. In fact they are used to charge the batteries inside the mobiles by providing them a low level DC voltage and current. There may be different types of chargers used to charge different mobile phones but the key functioning of those all are almost same.

Fig. 1: Image of a Mobile Charger

The above image shows a commonly used mobile charger.

PCB with Components

Fig. 2: PCB Circuitry of Mobile Charger

On opening the outer screws, we can see the PCB having majority of the components as shown in the image above.

Fig. 3: Four Diodes Imbibed in Mobile Charger PCB

Four diodes shown in the upper image are arranged to make a full wave rectifier circuit. The working of the rectifier is explained later in the article.

Other Components

Fig. 4: PCB Circuitry Components—Capacitors, Transistors, Diodes, and Resistors

The above image gives a clear look to the components that are used in the circuitry – capacitors, transistors, diodes and resistors.

Fig. 5: Pulse Transformer of Mobile Charger

A pulse transformer shown in the above image is a special purpose transformer.

Working

Fig. 6: LED of Mobile Charger

When charger is connected with the AC supply, the LED starts glowing to indicate the proper operation of the charger.

Working

Latest mobile chargers are kind of power supply units that use the Switched Mode Power Supply (SMPS) technology. To understand the working phenomenon of a mobile charger, we need to understand the concept of Power Supply Unit (PSU). PSU is a device that transfers electrical energy from one end to another by changing its fundamental characteristics according to the requirements. Example of a PSU is an application that converts AC mains voltage to regulated DC voltage. PSUs can be of two types depending on the mode of operation – Linier and Switching.

In these switching mode chargers, energy transfer is done by continuously switching electrical components (inductor, capacitor, etc) on and off. We can control the output voltage/current by varying the duty cycle, frequency or the corresponding phase. Using the SMPS technology makes the chargers smaller and lighter by elimination of low frequency transformers. It also presents a greater efficiency than the conventional methods which uses bulky transformers.

The AC supply first enters through the line filters in the charger. Line filters are the kind of electronic filters that are placed between an electronic device and an external line to alter/attenuate the electromagnetic interference effect. Now filtered signal are made to pass through the full wave bridge rectifier circuit. Rectifier converts the AC voltage to DC.

Pulse transformers are categorized into two categories – power and signal transformers. The one used here is a power transformer. It reduces the voltage level of the input power and gives a low voltage power that is exactly required to charge the battery.

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