650 V SiC FETs Cut Power System Loses

UnitedSiC has announced the UJ3C series of 650 V SiC FETs as drop-in replacements for silicon Superjunction MOSFETs. Available in standard TO-220, TO-247 and D2PAK-3L packages, they operate with standard Si-MOSFET gate drive, eliminating the need to re-design drive circuits, while offering low RDS(ON) and low gate charge to reduce system losses. Used for power factor correction and DC-DC conversion in both hard-switched and ZVS-switched systems, applications include electric vehicle (EV) chargers, power supplies, motor drives and renewable energy inverters.

The maximum drain current (ID) ratings for these SiC transistors ranges from 31 A to 85 A. Low RDS(ON), specified at 27 mohms, is best in class for TO-220 devices. Furthermore, a built-in low Qrr body diode eliminates the need for an anti-parallel diode. With their combination of low RDS(ON), high current rating and excellent thermal performance, the UJ3C series can be used in hard-switched converters and zero-voltage switching applications such as LLC and phase-shifted full bridge converters. The devices also enable switching frequencies of up to 500 kHz, allowing designers to reduce the size and cost of other system components, including bulky inductors, capacitors and thermal management parts.

UnitedSiC’s “Simple Silicon Substitution” technology comprises a patent-pending metal gate SiC JFET co-packaged with a custom designed, ESD protected, low voltage silicon MOSFET.  Advanced proprietary die-attach and packaging techniques minimize losses and ensure effective thermal management. As a result, designers using silicon transistors in legacy designs can easily upgrade their existing system’s power performance using UnitedSiC’s plug-and-play devices.

UJ3C065080T3S series SiC FETs are available now with prices starting at $7.69 each in 1000+ quantities.

UnitedSiC | www.unitedsic.com

LED Lighting Controller for Automotive

Texas Instruments has introduced the first 3-channel high-side linear automotive light-emitting diode (LED) controller without internal MOSFETs that gives designers greater flexibility for their lighting designs. The TPS92830-Q1’s novel architecture enables higher power and better thermal dissipation than conventional LED controllers, and are particularly beneficial for automotive LED lighting applications that require high performance and reliability.

TPS92830-Q1Conventional LED drivers integrate the MOSFET, which limits designers’ ability to customize features. With that type of driver, designers often must make significant design modifications to achieve the desired system performance. The TPS92830-Q1 LED controller’s flexible on-board features give designers the freedom to select the best MOSFET for their system requirements. With this new approach, designers can more quickly and efficiently optimize their lighting power designs for automotive system requirements and desired dimming features.

The on-chip pulse-width modulation (PWM) generator or PWM input enables flexible dimming. Designers can use either the analog control or PWM to manage an output current of more than 150 mA per channel, to power automotive rear combination lamps and daytime running lights.

By pairing the LED controller with an external MOSFET, the designer can achieve the required high power output while distributing the power across the controller and MOSFET to avoid system overheating. By retaining linear architecture, the TPS92830-Q1 provides improved electromagnetic interference (EMI) and electromagnetic compatibility (EMC) performance.

Advanced protection and built-in open and short detection features help designers meet original equipment manufacturer (OEM) system reliability requirements. The output current derating feature protects the external MOSFET under high voltage conditions to ensure system reliability.

Support tools include the TPS92830-Q1 3-Channel High-Current Linear LED Controller evaluation module. Engineers can jump-start automotive lighting systems designs using the TPS92830-Q1 with the EMC Compliant Automotive Daytime Running Light and Position Light Reference Design with LED Thermal Protection. The TPS92830-Q1 is now available through the TI store and authorized distributors. Offered in a thin small outline package (TSOP), it is priced at US$1.96 in 1,000-unit quantities.

Texas Instruments | www.ti.com

MOSFET is Drop-In Replacement for DPAK Footprint

Infineon Technologies is expanding its recently launched CoolMOS P7 superjunction power MOSFET family with a SOT-223 package. The device has been developed as a one-to-one drop-in replacement for DPAK. It is fully compatible with a typical DPAK footprint. The combination of the new CoolMOS P7 platform with the SOT-223 package is Infineon SOT223-CoolMOS-P7a perfect fit for applications such as chargers for smartphones, laptop adapters, TV power supplies and lighting.

The new power MOSFET CoolMOS P7 is designed to address needs of the low power SMPS market. It uses a price competitive superjunction technology, which results in a reduced overall Bill of Materials (BOM) on the user side. The thermal behavior of the CoolMOS P7 in this package was assessed across several applications. When the SOT-223 was placed on a DPAK footprint, the temperature increased by a maximum of 2°C to 3 °C compared to a standard DPAK. And for copper areas of 20 mm² or more, the thermal performance was equal to DPAK. The CoolMOS P7 in SOT-223 is available in 600 V, 700 V and 800 V devices.

Infineon Technologies | www.infineon.com

700-V CoolMOS P7 Family for Flyback-Based, Low-Power SMPS Applications

Infineon Technologies recently launched the 700-V CoolMOS P7 family for quasi-resonant flyback topologies. Offering performance advantages over superjunction technologies, the MOSFETs are well suited for mobile device chargers and notebook adapters. They also support fast switching and high power density designs for TV adapters, lighting, and moreInfineon CoolMOS_P7

Features and benefits include:

  • Finely graduated RDS(on) x Eoss; lower Qg, Eon and Eoff
  • High switching frequency capable
  • Integrated Zener diode
  • Large variety of packages
  • Low losses
  • Additional 50 V of blocking voltage compared to C6 technology
  • Meets EMI requirements
  • High ESB ruggedness
  • Lower case temperatures

The 700 V CoolMOS P7 family is available with the most relevant RDS(on) package combinations including 360 mΩ up to 1400 mΩ in IPAK SL, DPAK, and TO-220FP.

Source: Infineon Technologies

New Radiation-Hardened MOSFETs for Space Applications

IR HiRel (an Infineon Technologies company) recently launched its first radiation-hardened MOSFETs based on the proprietary N-channel R9 technology platform. Offering size, weight, and power improvements over previous technologies, the 100-V, 35-A MOSFETs are ideally suited to mission-critical applications requiring an operating life up to and beyond 15 years. Target applications include space-grade DC-DC converters, intermediate bus converters, motor controllers, and high-speed switching designs.Infineon - RAD-hard-MOSFET

The IRHNJ9A7130’s and IRHNJ9A3130’s features, benefits, and specs:

  • Characterized for total ionizing dose (TID) immunity to radiation of 100 krads and 300 krads, respectively.
  • An R DS(on) of 25 mΩ (typical) is 33% lower than the previous device generation.
  • Provide increased power density and reduced power losses in switching applications
  • Improved Single Event Effect (SEE) immunity and have been characterized for useful performance with Linear Energy Transfer (LET) up to 90 MeV/(mg/cm²); at least 10 percent higher than previous generations.
  • Both of the new devices are packaged in a hermetically sealed, lightweight, surface-mount ceramic package (SMD-0.5) measuring just 10.28 mm × 7.64 mm × 3.12 mm.
  • Available in bare die form.

Source: Infineon Technologies

SuperFET III Family of 650-V N-channel MOSFETs

Fairchild Semiconductor recently introduced the SuperFET III family of 650-V N-channel MOSFETs, which are well suited for telecom equipment, electric vehicle (EV) chargers, solar products, and more. The SuperFET III MOSFET family combines reliability, low EMI, high efficiency, and superior thermal performance. Furthermore, its various package options give you greater flexibility when dealing with space-constrained designs.

The SuperFET III has the lowest Rdson in any easy drive version of a Super Junction MOSFET. It is has 3× better single pulse Avalanche Energy (EAS) performance than its closest competitor. Such advantages make it useful for industrial applications such as solar inverters and EV chargers.

The SuperFET III MOSFET family is now available in multiple package and parametric options.

Source: Fairchild Semiconductor

800-V CoolMOS P7 Series for Low-Power SMPS Applications

Infineon Technologies recently introduced its 800-V CoolMOS P7 series. Based on the superjunction technology, the product family is well suited for low-power SMPS applications, such a s LED lighting, audio, industrial, and auxiliary power.Infineon_CoolMOS

The 800 V CoolMOS P7’s offers up to 0.6% efficiency gain. In addition, an integrated Zener diode reduces ESD-related production yield losses. The easy to drive and design-in MOSFET features an industry leading V (GS)th of 3 V and the smallest V GS(th) variation of only ±0.5 V.

The 800-V CoolMOS P7 MOSFET family will be available in twelve R DS(on) classes and in six packages. You can order products with R DS(on) of 280 mΩ, 450, 1,400, and 4,500 mΩ.

Source: Infineon Technologies

Precision MOSFETS Automatically Balance Supercaps in Industrial Apps

Advanced Linear Devices (ALD) has launched a family of Supercapacitor Auto Balancing (SAB) Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) intended for industrial applications to regulate and balance leakage currents while minimizing energy used for balancing supercapacitor cells stacked in series stack of two or more. The MOSFETs are well-suited for a variety of industrial-grade energy storage applications that require an operating temperature between –40° to 85°C. ALD - ALD8100xx


Each device in the industrial SAB MOSFET ALD8100xxx/ALD9100xxx family contains 26 different products, each of which can balance supercapacitors up to four cells in a single IC package. Starting with two cells, the devices can balance an unlimited number of supercapacitor cells stacked in a series. In addition, each device in the SAB MOSFET family dissipates near zero leakage current to eliminate extra power dissipation.


Available in both quad and dual packages, the industrial SAB MOSFETs are made with ALD’s precision EPAD technology. The ALD8100xx/ALD9100xx SAB MOSFET family is available in industry standard 16-L or 8-L SOIC packages. One thousand-piece pricing starts at $1.76 each.

Source: Advanced Linear Devices

Fast 600-V Gate Driver Reduces System-Solution Size for MOSFETs and IGBTs

Texas Instruments recently introduced the UCC27714 half-bridge gate driver for discrete power MOSFETs and IGBTs that operate up to 600 V. With 4-A source and 4-A sink current capability, the UCC27714 reduces component footprint by 50%. In addition, it provides 90-ns propagation delay, 40% lower than existing silicon solutions, tight control of the propagation delay with a maximum of 125 ns across –40°C to 125°C and tight channel-to-channel delay matching of 20 ns across –40°C to 125°C.  The device eliminates the need for bulky gate drive transformers, saving significant board space in high-frequency switch-mode power electronics.TI-gatedriver

Key features and benefits include:

  • Smaller footprint creates highest power-density solutions
  • Advanced noise toleration
  • MOSFETs have the ability to drive over a wide power range
  • Operates across wide temperatures

The UCC27714 is now available. The high-speed 600-V, high-side low-side gate driver costs $1.75 in 1,000-unit quantities.

Source: Texas Instruments

New Power MOSFETs Compact, Durable Electrical Appliances

Infineon Technologies recently extended its StrongIRFET Power MOSFET family. The Logic Level StrongIRFETs can be driven directly from a microcontroller, thus saving space and cutting costs. Additionally, the MOSFETs are highly rugged and thus help lengthen the service life of the electronic devices, such as DIY power tools (e.g., cordless drills) that have to be handy and durable.  Infineon Logic_Level_StrongIRFET

The StrongIRFET family enables high energy efficiency in electric appliances. With the logic level extension, Infineon meets the market’s demand for StrongIRFETs that do not require a stand-alone driver. In the logic level variant the necessary gate-source voltage is reduced to 4.5 V. Thus, you can directly connect the MOSFET with the microcontroller in many applications.

The characteristic performance features include: low on-state resistance (0.52 mΩ typical and 0.97 mΩ maximum) for reduced conduction losses, high current carrying capability for increased power capability, and rugged silicon all make for high system reliability.

Source: Infineon Technologies

HITFET+ Family of Protected Low-Side Switches

Infineon Technologies recently announced the HITFET+ family of protected low-side switches. The HITFET+ family (High Integrated Temperature protected MOSFET) offers a handy feature-set with its diagnosis function, digital status feedback and short-circuit robustness, and controlled slew rate adjustment for easily balancing switching losses and EMC compliance. The HITFET+ family will comprise at least 16 members varying in R DS(on) (10 to 800 MΩ), feature set (i.e., with and without status feedback), and package size (D-PAK with 5 or 3 pins, DSO with 8 pins). HITFET+ products of one package size are completely scalable. You don’t need to change either software or PCB layout to drive various loads. The BTF3050TE is already available in high-volume.Infineon HITFETplus

HITFET+ products are suitable as protected drivers in industrial applications, including solar power modules, printers, and vending machines.

As for use in automotive systems, the HITFET+ products can drive solenoids for valve control with PWM up to 20 kHz. They are also a good fit for automotive light-dimming applications. In addition, the HITFET+ family can be useful in a variety other automotive applications, such as the following:

  • mid-size and small-size electric motor drives for door locks or a parking brake
  • injection valves for alternative fuel (LPG, CNG)
  • flaps driving in HVAC
  • rear wheel steering applications

The BTF3050TE is now available in a lead-free TO-252 package (D-PAK 5-pin) in high volume. Additional HITFET+ products are scheduled to be released toward the end of 2015.

Source: Infineon Technologies

OptiMOS Product Family Exceeds 95% Efficiency

Infineon Technologies recently launched the OptiMOS 5 25- and 30-V product family, the next generation of Power MOSFETs in standard discrete packages, a new class of power stages named Power Block, and in an integrated power stage, DrMOS 5×5. Together with Infineon’s driver and digital controller products the company delivers full system solutions for applications such as server, client, datacom or telecom.Infineon-OptiMOS

The newly introduced OptiMOS family offers benchmark solutions with efficiency improvements of around 1% across the whole load range compared to its previous generation, exceeding 95% peak efficiency in a typical server voltage regulator design. This improved performance is based for example on the reduction of switching losses (Q switch) by 50% compared to the previous OptiMOS technology. Thus, implementing the new OptiMOS 25 V would lead to energy savings of 26.3 kWh per year for a single 130-W server CPU working 365 days.

The launch of the OptiMOS product family is accompanied by the introduction of a new packaging technology offering a further reduction in PCB area consumption. It is used in the Power Block product family and in the integrated powerstage DrMOS 5×5 and offers a source down low-side MOSFET for improved thermal performance, with a reduction by 50% of the thermal resistance in comparison to standard package solution, such as SuperSO8.

Infineon`s Power Block is a leadless SMD package comprising the low-side and high-side MOSFET of a synchronous DC/DC converter into a 5.0 × 6.0 mm 2 package outline. With Power Block, customers can shrink their designs up to 85 percent by replacing two separate discrete packages, such as SuperSO8 or SO-8. Both, the small package outline and the interconnection of the two MOSFETs within the package minimize the loop inductance for best system performance.

OptiMOS 5 25V is also used in an integrated power stage, combining DrMOS 5×5, driver and two MOSFETs, for a total area consumption on the PCB equal to 25mm². The integrated driver plus MOSFETs solution results in a shorter design time and is easy to design-in. Additionally, the dovetailed power stage includes a high accurate temperature sense of +/-5°C (compared to +/-10°C of an external one) which enables higher system reliability and performance.

Samples of the new OptiMOS 25- and 30-V devices in SuperSO8, S3O8 and Power Block packages, with on-state resistances from 0.9 mΩ to 3.3 mΩ are available. Additional products with monolithic integrated Schottky-like diode and products in 30 V will be available from Q2 2015 onwards. DrMOS 5×5 will be released in Q2 2015. Samples are available.

Source: Infineon

New Power MOSFET Drivers Feature Thermally Efficient, Small Packages

Microchip Technology recently announced the first power MOSFET drivers in a new product family—the MCP14A005X and MCP14A015X. The drivers feature a new driver architecture for high-speed operation.MicrochipMCP14

The new devices’ small packaging (SOT-23 and 2 mm × 2 mm DFN packages) enables higher power densities and smaller solutions, while the design targets fast transitions and short delay times that allow for responsive circuit operation. In addition, the MOSFET drivers include low input threshold voltages that are compatible with low-voltage microcontrollers (MCUs) and controllers, while still maintaining strong noise immunity and hysteresis.


The MCP14A005X and MCP14A015X MOSFET drivers low input threshold is compatible with various Microchip PIC microcontrollers and dsPIC Digital Signal Controllers (DSCs), even when operating at lower voltages. This enables you to design applications with MCUs operating as low as 2 V, using the MOSFET driver to boost the output signals to 18 V, reducing power loss in the controller and minimizing conduction loss in the power MOSFET. The threshold levels balance the need for noise immunity with the ability to function with a wider variety of controller products, including Microchip’s devices. These drivers are designed for use in power supply, lighting, automotive, and consumer electronics markets, including embedded power conversion, brushed DC motor, unipolar stepper motor and solenoid/relay/valve control applications, among others.


The MCP14A005X and MCP14A015X are available now for sampling and volume production in  SOT-23 and 2 × 2 mm DFN packages. Prices range from $0.50 to $0.61 each in 10,000-unit quantities.

Source: Microchip Technology 

NexFET N-Channel Power MOSFETs Achieve Industry’s Lowest Resistance

Texas Instruments recently introduced 11 new N-channel power MOSFETs to its NexFET product line, including the 25-V CSD16570Q5B and 30-V CSD17570Q5B for hot swap and ORing applications with the industry’s lowest on-resistance (Rdson) in a QFN package. In addition, TI’s new 12-V FemtoFET CSD13383F4 for low-voltage battery-powered applications achieves the lowest resistance at 84% below competitive devices in a tiny 0.6 mm × 1 mm package. TI CSD16570Q5B

The CSD16570Q5B and CSD17570Q5B NexFET MOSFETs deliver higher power conversion efficiencies at higher currents, while ensuring safe operation in computer server and telecom applications. For instance, the 25-V CSD16570Q5B supports a maximum of 0.59 mΩ of Rdson, while the 30-V CSD17570Q5B achieves a maximum of 0.69 mΩ of Rdson.

TI’s new CSD17573Q5B and CSD17577Q5A can be paired with the LM27403 for DC/DC controller applications to form a complete synchronous buck converter solution. The CSD16570Q5B and CSD17570Q5B NexFET power MOSFETs can be paired with a TI hot swap controller such as the TPS24720.

The currently available products range in price from $0.10 for the FemtoFET CSD13383F4 to $1.08 for the CSD17670Q5B and CSD17570Q5B in 1,000-unit quantities.

Source: Texas Instruments

The Sun Chaser Energy-Harvesting System

When Sjoerd Brandsma entered the 2012 Renesas Green Energy Challenge, he wanted to create a fun project that would take advantage of his experience at a company that heavily uses GPS.

Brandsma, who lives in Kerkwijk, The Netherlands, has worked as a software engineer and is currently an R&D manager at CycloMedia, which produces 360° street-level panoramic images with geographic information system (GIS) accuracy.

Ultimately, Brandsma’s Sun Chaser project won third prize in the Renesas Green Energy Challenge. The Sun Chaser is an energy-harvesting system that automatically orients a solar panel to face the sun.

Photo 1: The Sun Chaser’s stepper motor controls the solar panel‘s “tilting.”

Photo 1: The Sun Chaser’s stepper motor controls the solar panel‘s “tilting.”

“The Sun Chaser perfectly follows the sun’s path and keeps the battery fully charged when there’s enough sunlight,” Brandsma says in his article about the project, which appears in Circuit Cellar’s June issue. ”It can power a small electronics system as long as there’s enough sunlight and no rain, which would damage the system due to lack of protection. This project also demonstrates that it’s possible to build an interesting green-energy system with a tight budget and a limited knowledge of  electronics.”

A registered GPS calculates the orientation of the Sun Chaser’s solar panel, which is mounted on a rotating disc. “You can use an external compass, the internal accelerometer, a DC motor, and a stepper motor to determine the solar panel’s exact position,” Brandsma says. “The Sun Chaser uses Renesas Electronics’s RDKRL78G13 evaluation board running the Micriµm µC/OS-III real-time kernel.”

The following article excerpt describes the GPS reference station and evaluation board in greater detail. The issue with Brandsma’s full article is available online for membership download or single-issue purchase.

Whenever you want to know where you are, you can use a GPS receiver that provides your position. A single GPS receiver can provide about 10 to 15 m (i.e., 33’ to 50’) position accuracy. While this is sufficient for many people, some applications require positioning with significantly higher accuracy. In fact, GPS can readily produce positions that are accurate to 1 m (3’), 0.5 m (18”), or even 1 to 2 cm (less than 1“). A technique called “differential GPS” can be used to achieve higher accuracy.

The differential technique requires one GPS receiver to be located at a known position (often called a control or reference point) and a second “rover” receiver at the location to be measured. The information from the two GPS receivers (rover and control) is combined to determine the rover’s position. That’s where a GPS reference station comes in. It functions as the control point and serves potentially unlimited users and applications. Leica Geosystems has published an excellent introductory guide about GPS reference stations (Refer to the Resources at the end of this article.)

The GPS reference station should always be located at a position with a broad sight. In some situations it can be difficult to provide a decent power supply to the system. When regular power isn’t available, a solar panel can power the GPS reference station.

My Sun Chaser GPS reference station uses a 10-W solar panel connected to a 12-V battery to provide enough power. To increase the energy harvesting, the solar panel is mounted on a rotating disc that can be controlled by a DC motor to point in the desired direction. A stepper motor controls the solar panel’s “tilting.” Photo 1 highlights the main components.

The RDKRL78G13 is an evaluation and demonstration tool for Renesas Electronics’s RL78 low-power microcontrollers. A set of human-machine interfaces (HMIs) is tightly integrated with the RL78’s features. I used several of these interfaces to control other devices, read sensors, or store data.

Most of the system’s hardware is related to placing the solar panel in the correct position. Figure 1 shows the top-level components used to store the GPS information and position the solar panel.

Figure 1: The Sun Chaser’s components include a Renesas Electronics RDKRL78G13 evaluation board, a GPS receiver, a stepper motor, and an SD card.

Figure 1: The Sun Chaser’s components include a Renesas Electronics RDKRL78G13 evaluation board, a GPS receiver, a stepper motor, and an SD card.

The RDKRL78G13 evaluation board has an on-board temperature and light sensor. Both sensor values are stored on the SD card. The on-board light sensor is used to determine if rotating/tilting makes sense (at night it’s better to sleep). For this project, the temperature values are stored just for fun so I could make some graphs or do some weather analysis.

A micro-SD memory card slot on the RDKRL78G13 evaluation board provides file system data storage. I used it to store all incoming data and log messages using the FAT16/FAT32 file system.

The on-board Renesas Electronics RQK0609CQDQS MOSFET controls the DC motor that rotates the evaluation board. The DC motor can be controlled by applying a PWM signal generated from one of the RL78’s timers. The MOSFET is controlled by the RL78’s TO05 port and powered from the 12-V battery. A PWM signal is generated on TO05 by using Timer4 as a master and Timer5 as a slave. It’s only necessary to rotate clockwise, so additional hardware to rotate the platform counterclockwise is not required.

A digital compass is needed to determine the evaluation board’s rotated position or heading (see Figure 2). The Honeywell HMC5883L is a widely used and low-cost compass. This I2C-based compass has three-axis magnetoresistive sensors and a 12-bit ADC on board. It can read out values at a 160-Hz rate, which is more than enough for this project.

Figure 2: A Honeywell HMC5883L digital compass verifies the evaluation board’s rotated position or heading.

Figure 2: A Honeywell HMC5883L digital compass verifies the evaluation board’s rotated position or heading.

The compass uses the RL78’s IICA0 port through the Total Phase Beagle debug header, which is mounted on the RDKRL78G13 evaluation board. The Beagle analyzer provides easy access to this I2C port, which increases the flexibility to change things during prototyping.

The HMC5883L compass turned out to be a very sensitive device. Even the slightest change in the hardware setup seemed to influence the results when rotating. This meant some sort of calibration was needed to ensure the output was consistent every time the system started. [Brandsman’s full article descibes how how the HMC5883L can be calibrated. It’s important to know that every time the system starts, it makes a full turn to calibrate the compass.

A GPS module must be connected to the system to provide the system’s current location. I wanted the GPS module to be inexpensive, 3.3-V based, and have an easy and accessible interface (e.g., UART).

Figure 3 shows a schematic of a Skylab M&C Technology SKM53 GPS module, which is based on the MediaTek 3329 GPS receiver module. This module supports NMEA messages and the MTK NMEA Packet Protocol interface to control things such as power saving, output message frequency, and differential global positioning system (DGPS).

Unfortunately, the 3329 receiver can’t output “raw” GPS data (e.g., pseudorange, integrated carrier phase, Doppler shift, and satellite ephemeris), which would significantly improve the GPS reference station’s capabilities. Due to budget and time limitations (it takes some more software development effort to handle this raw data), I didn’t use a receiver that could output raw GPS data.

Figure 3:A Skylab M&C Technology SKM53 GPS receiver obtains the system’s current location.

Figure 3:A Skylab M&C Technology SKM53 GPS receiver obtains the system’s current location.

The SKM53 GPS receiver is connected to the RL78’s UART2. All data from the GPS receiver is stored on the SD card. As soon as a valid GPS position is received, the system calculates the sun’s position and moves the platform into the most ideal position.

A compact stepper motor is needed to tilt the platform in very small steps. The platform had to be tilted from fully vertical to fully horizontal in approximately 6 h when the sun was exactly following the equator, so speed wasn’t really an issue. I wanted to do very fine tilting, so I also needed a set of gears to slow down the platform tilting.

I used an inexpensive, easy-to-use, generic 5-V 28BYJ-48 stepper motor (see Figure 4). According to the specifications, the 28BYJ-48 stepper motor has a 1/64 gear reduction ratio and 64 steps per rotation (5.625°/step) of its internal motor shaft.

An important consideration here is that you don’t want to retain power on the stepper motor to keep it in position. This particular stepper motor has some internal gears that prevent the platform from flipping back when the stepper motor is not powered.

The stepper motor can be controlled by the well-known ULN2003 high-voltage high-current Darlington transistor array. The ULN2003 is connected to P71-P74. Each of the ULN2003’s four outputs is connected to one of the stepper motor’s coils. When two neighbor coils are set high (e.g., P72 and P73), the stepper motor will step in that direction.

When it comes to solar panels, you can build your own panel out of individual solar cells or buy a fully assembled one with known specifications. I used a no-name 10-W solar panel. The size (337 mm long × 205 mm wide × 18 mm high) was acceptable and it delivered more than enough energy. I used a charge controller to protect the battery from overcharging and to prevent it from supplying power to the solar panel at night.

Like solar panels, many charge controllers and battery protectors can be used in such a system. I chose the lazy approach: Just take one off the shelf. The CMP12/24 charge controller is specially designed for small solar systems. It has a stabilized 12-V output, which is taken from the connected battery. It can handle up to 12 A of charging or load current and, according to the specifications, it consumes about 20 mA of quiescent current. There is some room for improvement, but it worked for my project.

I had some 7805 voltage regulators lying around, which I figured could do the job and supply just enough power when the system was starting up. However, when it comes to power saving, the 7805 is not the way to go. It’s a linear regulator that works by taking the difference between the input and output voltages and burning it up as wasted heat.

What I needed was a switching regulator or a buck converter. I used a National Semiconductor (now Texas Instruments) LM2596. Note: The LM2596 is made by several companies and is available in inexpensive, high-quality modules (most cost a little more than $1 per converter). These ready-to-use modules already have the necessary capacitors, diodes, and so forth on board, so it’s really a matter of plug and play.

I used a lead acid RT1219 12-V 1.9-AH battery for power storage. You can use any 12-V battery with sufficient capacity.

Editor’s Note: Check out other projects from the 2012 Renesas RL78 Green Energy Challenge.