Waves of effort to go green

As humans continue to depend on electronic products, more features are expected to be integrated in these devices as needs and lifestyles change. A classic example would be old models of mobile phones that can only do plain old telephony (POT) are now being replaced with multimedia handsets that can capture pictures and videos; record and play music; view e-mails and so forth. In the next few years, these intelligent handsets will integrate more functions.

Now, as portable devices become densely packed with functions, more power is needed to run these gadgets. Batteries are constantly being replaced with powerful versions to meet the ever increasing requirements. However, old batteries containing hazardous metals are not properly discarded. This places technical, environmental and financial problems, such as high energy cost and power wastage.

To address this issue, electronic designers must find ways to drive down power consumption without compromising performance and availability. These can be done through advancements in design, technology, integration of parts, and system architecture.DESIGN

From the design perspective, whether at silicon or circuit board level, the utilization of power can be minimized without sacrificing the expected or desired output quality (for whatever that may be) through power saving techniques and well crafted functions with various system operational modes. Let’s take the example of a cellphone. Power can be saved at various levels.

Design plays a large part in conserving power or utilizing power more effectively and efficiently. There are many IPs and circuits that are dedicated for saving power, particularly for portable applications. To keep the list short for illustrative purposes, here are a few methods and technologies that Freescale has developed.

• Dynamic voltage scaling (DVS) – scaling down the voltage when the system processor knows that the required power delivery or drive is low.

• Pulse skipping – for light loads, or under very low activity operations (close to standby), the power FETs that deliver the current/voltages to other circuit components can be skipped through some conduction cycles to reduce power wastage. Freescale has incorporated these power saving techniques in its portable products such as mobile phone chipsets, PMUs for MP3 players, i.MX multimedia platforms, and dc-dc converters, just to name a few. There are other basic power saving techniques that are being implemented, such as switching frequency control or modulation techniques (PFM) for various power levels, gating the clock, reducing nominal voltages for driving circuits, etc.

ARCHITECTURE

The architecture also plays a significant role in power saving. A good architecture would not just implement the necessary functions and features of a product, but would also look at cost minimization, efficiency, performances, and power savings. For instance, if the architecture of a product such as a mobile phone is designed with power savings in mind and is optimized in both hardware and software, the end result would make a huge difference to the efficient use of power.

In other words, saving power is incorporated for each feature or function that can be implemented in software or hardware, with consideration made to various aspects of power saving like what the core voltage should be or what the system frequency should be, etc. All this would greatly impact the power usage. Obviously this should be at no cost to the system’s performance and the cost of building the product.

SYSTEM

The system would create the biggest power savings of all—as it can dictate and control, through software and hardware means, which part should be running and at what power level versus which parts need to be shut down or standby based on the functions that are commanded by the user.

For mobile phones, a PMU (power management unit) receives inputs from the main processor chip to power the device as per instruction. Or, the processor may execute a function in its DSP by running fewer codes as it has the intelligence to know what modes the module or phone is in. There could also be some smart power saving methods or algorithm in which the software intelligence will work with the hardware dynamically to minimize power usage to the lowest level possible.

TECHNOLOGY

Technology plays an imminent part on how effective each device or component can utilize power for a given function or performance. For instance, the process used to fabricate the silicon would determine what voltage the IC would be running at, or how strong each element (transistors, logic gates, etc.) can operate with the least amount of power. For a transistor, we would be looking at the gain of the device. If we take a MOSFET as an example, then we would be concerned at what Vgs voltage will deliver what magnitude of Ids current.

Furthermore, we would also be concerned with leakage and parasitic that would consume and drain away precious power. For instance, the RDS(on) of a FET would dictate what the conduction loss would be when the transistor is conducting. The current that flows through this channel resistance will be converted to heat and is a loss of power to the output of that device. Freescale has pioneered its SMARTMOS process to achieve the best results. The process delivers high power and precision suited to critical portable products with low leakage and low RDS(on).

COMPONENTS/BUILDING BLOCKS

Components, either passive or active, carry losses when power is applied to them. Capacitors, for instance, would inherit series resistance (ESR) that would translate to heat losses; or that inductors would inherit some DC resistance (DCR) that would constitute losses to the circuit or system.

Faraday will tell you differently that these devices incur no losses ideally, but in practice nothing is ideal. Even non-resistive elements could inherit non-idealities that would constitute to losses. For instance, for a buck converter, the free wheeling diode would require a forward bias voltage across it for current to flow while the switching FET is in the off mode. This voltage drop across the diode would constitute to losses as it plays no part in the output delivery of power except to get the output current flowing. Likewise for LEDs, the forward bias voltage is needed to turn them on, and this can be as high as 4V for certain colored

LEDs.

Due to technology advancements, the undesirable features are getting smaller and smaller. ESR or DCR can be reduced as packaging and formation of capacitors and inductors become advanced with less parasitic. Diodes like Schottky diodes are now being produced with lower forward bias voltage, and thus more of the voltage can be used for the output. Similarly, LED bias voltage is also getting smaller.

BATTERIES

Perhaps one of the most devastating components that can do more harm to our environment than others are the batteries that power portable devices like digital cameras and mobile phones. By today’s consumption standard, we are throwing away billions of batteries every year. Once a battery has been used and its life is up, it is thrown away. The acids and toxic chemicals within will harm our natural habitat if not disposed properly.

In essence, this would be imposing direct harm to our environment, whereas what was said about power losses and parasitic is more of an indirect impact. Nonetheless, it is the increased functions demanded by us, the humans, and the lack of power utilization efficiency that is fuelling the waste of used batteries.

Currently we are seeing that battery manufacturers are producing more longerlasting batteries with evolving technologies. For instance, some 20 years back, most batteries were of NiMH type and not lithium, and the energy per unit volume of the cell is much lower than today’s. Now we are seeing that lithium or poly-lithium batteries are widely used for portable devices like DSCs or cellphones.

Already, people are introducing more superior and advanced cells that can last longer and with high power density. For instance, what is believed to be the next wave of battery technology for portable products is the Iron-Liion (FeLi) cells. These batteries can be charged very fast and are far more long lasting than the common lithium ones. They also are safer and offer higher capacity per unit of storage.

Another advancement in technology that is being actively pursued is fuel cell technology. Fuel cells are promising a greener future as they do not need to be recharged. They also provide useful electricity and heat as long as hydrogen fuel is supplied. In fact people are racing to produce fuel cells for portable applications like RFID (radio frequency identification), and trying to make them commercially available.

Government and professional bodies like the US Fuel Cell Council, or the industry association for the fuel cell industry, were formed to spearhead this development.

ENERGY-EFFICIENT DISPLAYS

Many large and small corporations, scientists and engineers are developing displays that consume less power. Displays are becoming more sophisticated—the goal is to achieve bigger, sharper, and more colorful displays with higher resolution. These display enhancements translate to more power consumption, thus the need for more powerful batteries.

To address this issue, new technologies such as bistable displays, also widely-known as e-paper displays (EPDs) or e-ink powerless displays, offer a solution for displaying image content without power. Portable products using this technology, such as e-books in Japan, are making headlines with new applications. This type of display only needs power when the image needs changing or refreshing; when it is not, it requires no power to retain the image being shown, and this can be forever. Furthermore, the display is also reflective, meaning it does not need a backlight (which is contrary to LCD displays) for viewing; only ambient light is needed. The low-power display is lightweight and suits applications that do not require frequent change of display content, such as e-books and electronic schedule billboard at airports and train stations.PACKAGING

Packaging has come a long way to drive down cost, performance, and miniaturization. However, it has only been in recent years that governments and countries mandate the use of permitted materials that are lead-free and RoHS compliant.

RoHS stands for the “Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment,” and is a directive that requires the elimination of lead, cadmium, mercury, hexavalent chromium, and certain flame retardants, biphenyls (PBB) and polybrominated diphenyl ethers (PBDE), from electrical and electronic products. It was enforced on July 1, 2006 by the European Union and Commission.

To support the RoHS Directive, Freescale has been providing material composition and compliance declaration data (based upon IPC 1752 form) through PDF files and Web-based means since March 2006.

New products will all be RoHS compliant while old ones are converted to RoHS.

Although batteries are not restricted by RoHS, there exists control and directives that explicitly highlight the need for improving and protecting the environment from the negative effects of the waste contained in batteries.

EXAMPLE

Freescale has developed its TPMS (tire pressure monitoring system) chip. TPMS is a safety monitoring mechanism that monitors the car tire’s pressure and temperature, and alerts the driver when the pressure falls outside the safety range.

The RoHS-compliant TPMS has intelligence incorporated into a single device, which means fewer components. Further, the TPMS features a life span of up to 10 years. These features were achieved at the packaging, design, system (software and hardware), and component levels, where Freescale is striving to minimize the use of scarce resources. The company continues to produce products that make mechanical, automotive and electrical systems more energy- and fuel-efficient, and improve the way we live our lives.

The billion piles of electronic waste and inefficient use of power are affecting our ecosystem and pose a great danger to our living environment. We need to battle this issue now and not leave it to tomorrow.

GREEN MEASURES

Governments and large corporations are taking greater measures to save our polluted environment and are taking the lead to push everyone in this direction. Freescale is no exception. It has committed strongly to improving the environment by incorporating environmentally preferred materials and design features into its products.

Furthermore, Freescale has been pushing its employees to design and produce more efficient, eco-friendly products that require less energy. In fact this has been an initiative led and challenged by top management with ongoing environmental product efforts driven through a global, cross-functional effort. This is evident not only in Freescale’s products, but also in global programs such as EPP (Environmentally Preferred Products), which is one of Freescale’s efforts to address customer and regulatory requirements for product content. Primary efforts include EU and Chinese RoHS directives and packing material directives.

It does not need reminding that our population is growing and our appetite for technological goods is surging even more rapidly than ever before. We need to be more responsive and play a more integral part in making our environment cleaner and eco-friendly, else our next generation will have little to look forward to. We need to be part of this united effort of going green.

Click here for the illustration:

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