As we mentioned in the previous EDGE issue in the story, "Achieving Better System Energy Efficiency with Versatile Power-Control Function Modules", Renesas is promoting the use of function-module application solutions to support the more effective development of electronic systems. Each module incorporates a high-performance Renesas MCU together with appropriate power and analog devices. Different modules combine hardware, software, and system knowhow, all directed toward the solution of particular design issues. Customers can use these modules to shorten system development time, reduce the number of parts, and help their system engineers build higher performance and greater functionality into new products.
Today we hear from Professor Sadaharu Tamoto, from the Power Electronics Technology Research Lab, about Power Electronics technology trends and the advantages of Renesas’ function module solutions.
Implementing power electronics applications with function modules
Power electronics addresses the entire life cycle of electricity within a system: generation, transmission, conversion, and storage. Its areas of concern also extend to the configuration and use of these systems.
PE comprises numerous technologies: circuit technology, manufacturing technology, usage methods, and more. Today, it appears that PE's most important goal is to find and implement measures for reducing energy consumption. PE engineers are concerned with promoting efficiency in all of the four stages previously mentioned: generation, transmission, conversion, and storage. As a result of their work, we are seeing steady progress in technologies that produce power savings.
PE development: current issues and achievements
To achieve significant power savings, today’s PE systems must deliver precision control and efficient operation. That’s why MCU-driven digital control is taking the place of conventional analog control implementations.
However, many of today’s experienced PE design engineers are still coming from an analog technology background. Therefore they are often unfamiliar with MCU-based designs. To build effective digital systems, circuit designers must understand how MCUs and related devices are used, and how they interact. Software designers, too, are faced with the need to learn about unfamiliar and complicated circuitry.
For these reasons, many engineers working on PE projects have reported significant difficulty in making the transition from analog techniques to digital technology. Typically, they also find that they must devote considerable time and expense to the process of selecting combinations of microcontrollers (MCUs) and other devices that can deliver optimal combinations of functionality, capability and cost-performance.
It is also worth noting here that good PE systems must be capable of carrying out voluminous and complicated mathematical computations. Such designs require high-performance MCUs and sophisticated control software, the efficient application of which necessitates experience and specialized knowledge that many analog designers do not yet have.
The function-module approach can greatly facilitate PE development
Renesas has deep experience in the design and manufacture of power devices such as IGBTs and MOSFETs, as well as analog-digital ICs, photocouplers, driver ICs, and a wide range of low-end to high-end MCUs. We are now applying our technology expertise to design and deliver to customers function modules that provide fundamental AC-DC, DC-DC, and DC-AC solutions for PE systems.
Using our function-module approach, we are ready to suggest, and manufacture, comprehensive solutions incorporating optimal configurations of MCUs, power devices, and ICs. Further, we can provide support for the entire process, from initial design through to system deployment. By doing so, we are helping to accelerate the PE system development trend toward digital control, while also providing valuable assistance to PE circuit and software designers who need to master MCUs and MCU software.
Renesas function modules are highly effective PE system solutions. Each consists of an MCU and related devices configured to implement a specific function. This modular approach frees PE designers from a long and extensive device selection process. Importantly, it eliminates the considerable amount of time and money that otherwise would be wasted in selecting MCUs and devices. Moreover, it allows the system development team to concentrate on circuit and software design tasks that increase product value.
To facilitate system development, Renesas offers a full range of technical support resources, such as sample MCU programs and detailed device usage information. Also, we are happy to hold seminars to explain our wide lineup of devices and to provide instruction on proven methods for designing high-level PE circuits and MCU control programs.
To sum up: Renesas function modules are excellent solutions for the development of high-level PE systems. We offer them with solid support that simplifies and accelerates the successful adoption of energy-saving precision digital control technology.
Using function modules for PE applications
General-purpose PE systems are comprised of several function modules that have a common internal layout. Each module inputs an analog signal and outputs a pulse-width modulated (PWM) signal. Its control circuitry consists of a microcontroller (MCU) and program code (typically software stored internally as firmware), and its power circuitry consists of drive circuits and a power-control device.
Figure 1: Layout of a general-purpose function module designed for PE use. This basic layout can be used for other purposes, as well.
The input to a function module can accept a wide variety of analog signals: voltage, current, temperature, RPM, etc. The module’s PWM output is a series of pulses having the same amplitude but different durations. This output drives the power device, which might be an IGBT (insulated-gate bipolar transistor), a power MOSFET, or some other type of component. The control circuitry is a software implementation of control algorithms, so the module's specifications and operation can be changed simply by changing that software.
Let’s now look at how four different types of PE systems can be built around Renesas function modules.
Highlighting typical examples of systems that use function modules
◆Residential solar power conditioner, for the optimal use of solar energy
To better understand how function modules can be used in PE systems, it is instructive to examine some typical applications. For example, Figure 2, below, shows a residential solar-power conditioning system. This system comprises a DC/DC step-up module, an inverter module, and control circuitry implemented in the MCU. The solar panels convert energy from the sun into DC power, and the inverter converts this DC power to AC power and then sends it out to the commercial power grid.
The output from the solar panels varies as sunlight conditions change, and also as voltage demand from the load-side changes. An approach called maximum power point tracking (MPPT) is used to obtain maximum output from the solar cells. The process is controlled by the MCU through its control of the DC/DC step-up module.
Figure 2: Residential solar-power conditioner that maintains the maximum output from solar panels.
Renasas thoroughly understands the requirements of this type of application and can provide the DC/DC step-up modules, inverter modules, and control circuitry needed to build systems like the one shown in Figure 2.
◆Quiet, low-powered motor inverter for air conditioners
Another prime example of the way that function modules can be used in PE applications is a motor-control system for a residential air conditioner (see Figure 3). This system consists of a power factor corrector (PFC) module, 3-phase inverter module, and control circuitry implemented in the MCU. The PFC module converts the incoming commercial AC power to DC power, while at the same time removing harmonics (electrical noise). The 3-phase inverter (with phases 120 degrees apart) converts the DC power into the 3-phase AC power that smoothly drives the motor to a desired speed. A sensor monitors motor speed (RPM), and the MCU controls the process to maintain optimal operation of the air conditioner.
Figure 3: Motor inverter for a residential air conditioner. Smooth control of the motor reduces power consumption and noise.
For HVAC applications like the one illustrated in Figure 3, Renasas can supply the PFC modules, 3-phase inverter modules, and control circuitry needed to build reliable PE systems.
◆Efficient uninterruptable power supply (UPS)
A small UPS system is a good PE application to examine because society uses a huge number of these products to protect computer systems in businesses and homes. The purpose of a UPS is to provide backup power in the event that the transmission of commercial AC power is interrupted. Maximum backup duration varies according to the capabilities built into of the UPS and the load connected to it. Protection generally ensures continued computer operation for durations between 3 minutes and 3 hours, during which time processing can continue and/or the computer can be safely shut down.
The UPS system shown below in Figure 4 consists of a power factor corrector (PFC) module, a DC/DC step-up module, an inverter module, and control circuitry implemented in the MCU. The PFC module converts the incoming commercial AC power to DC power, while at the same time removing harmonics (electrical noise). That DC power is then stored in an internal battery.
When commercial power is applied to the UPS, the DC/DC step-up module takes the DC output from the PFC module and converts it to the DC output voltage needed to keep the UPS’ storage battery fully charged. If an AC power outage occurs, the DC/DC step-up module instantly changes its operation to pull energy from the storage battery and convert that energy to the higher DC voltage that drives the inverter. The inverter then produces the AC power that matches the commercially supplied power required by the external load.
Renesas can provide all of the modules shown in Figure 4, as well as the requisite control circuitry.
Figure 4: A small UPS. If commercial power supply is interrupted, the UPS takes DC power from its internal storage battery, converts it to AC power that matches the commercial supply, and outputs the result. All of these modules and the corresponding control circuitry are available from Renasas.
◆Charging station for the coming age of electric vehicles
Sales of electric cars and trucks (EVs) are on the rise, as is the need for charging stations used for replenishing the energy the vehicles use when driven. Thus, an EV charging station is an important example of a PE system. Its purpose, of course, is to rapidly fill the energy stored in the EV's battery to its full capacity, and to do so in a precisely controlled, safe way that maximizes the battery’s longevity. Although EV charging stations are relatively new to the market, demand for them is expected to increase dramatically both in Japan and internationally as the new infrastructure necessary for supporting electric vehicles is built.
Figure 5 illustrates a typical EV charging system. It consists of a 3-phase PFC module, an insulated DC/DC converter module, and control circuitry implemented in the MCU. Because rapid charging requires considerable power, these systems typically get their input power from a 3-phase 200-VAC source, rather than directly from the commercial source (110 VAC in Japan, for instance). The 3-phase PFC module, which is similar to the PFC module in the previously described UPS application, converts 3-phase AC into DC. The insulated DC/DC converter module isolates the input from the output and generates the large current required for quickly charging the EV’s batteries.
Here again, Renasas can deliver all of these components: the 3-phase PFC module, the insulated DC/DC converter module, and the control circuitry.
Figure 5: Charging station for EVs. This PE system converts incoming AC power (3 phase, 200 VAC) to DC power, and generates the high current required for fast charging. Renasas stands ready to supply all of these components so customers can respond quickly to market opportunities for implementing the EV support infrastructure.
The EDGE staff thanks Professor Tamoto for showing us examples of how function modules can be deployed in real systems that present significant market opportunities today. Next time we will highlight some of the Renesas MCUs and power and analog devices that can be used to build these modules