- Programmable PMICs support easy integration of IoT devices.
- LED driver ICs simplify building intelligent lighting networks.
- Starter kits and software tools ease development of energy harvesting.
Industrial LED Drivers and PMICs Get Better Products to Market Faster
Power supplies enabled by power-management integrated circuits (PMICs) convert wall plug power into the electricity needed to drive electronic equipment. Power devices play a simple role, but often they are the key elements that determine the performance of electronic equipment. In the case of mobile devices, for example, the conversion efficiency greatly influences the amount of time the equipment can operate on a single charge. Even for stationary equipment, energy efficiency has an important effect on operating cost. As a result, it is not uncommon for energy efficiency to become a factor that determines the value of a piece of industrial equipment.
The improvements in energy efficiency alone are not enough to meet the current demand for reduced power consumption, however. It is thus becoming necessary to supplement electric devices with new control strategies, including suppressing power to devices that are not running. At the same time, there is a great push for minimizing the size and cost of industrial equipment. Furthermore, improvements in the processing capacity of equipment have led to the emergence of low-voltage devices driven by large currents. These factors combine to add to the complexity of power-circuit devices, even as users demand simplicity.
What does all of this mean? First and foremost it means that all devices that only supply electricity by converting input power will fade into obscurity. Today’s market demands products with intelligent power that deliver a value that has not existed in the past.
Three technologies that support this mission include (see figure 1):
- PMICs for industrial equipment and office automation/communications equipment
- Communications-type LED driver ICs for smart homes and smarter lighting
- Energy-harvesting PMICs
The field of industrial and OA/communications equipment is marked by complex and sophisticated power circuits. The primary solutions include FPGAs, ASICs, and ASSPs that can drive the type of high-current, low-voltage (less than 1.0 V) core circuits mentioned earlier. These types of designs are being implemented in large-scale integrated designs (LSIs). At the same time, the memory and peripheral components related to these types of LSIs operate at voltages such as 3.3 V or 5 V. As a result, development focuses on PMICS that are able to handle large voltages while remaining compact themselves.
In order to address this issue, Spansion is developing PMICs like the S6AP412A and MB39C031 that with one IC can provide electricity for components ranging from cores to memories and peripheral devices (see figure 2). Based on our multi-channel DC-DC converter technology, these multi-channel PMICs can supply three electrical systems operating at 1.0 V, 3.3 V, and 5.0 V, respectively. In addition, the PMICs incorporate many intelligent functions designed to enable any engineer to easily make high-precision, high-performance, compact, and highly integrated power circuits.
These devices include a programmable function for setting the sequence control, which in turn determines the start/stop of each channel using software. These PMICs feature an I2C interface that allows the embedded designer to alter the sequence by changing the register via MCU. In addition to sequences, the software allows the output voltage and the software start time to be programmed.
Because alterations also can be made when the PMICs are running, they can accommodate the type of low-electrical-consumption control systems installed in the latest devices. These systems use techniques like adaptive supply voltage (ASV), which involves adjusting the source voltage in accordance with the individual differences of devices, and dynamic voltage and frequency scaling (DVFS), which adjusts the power source voltage in accordance with the operating situation.
The alteration of the sequence and output voltage by such software can also be achieved through a digital power source, including a DSP. This approach requires skilled software programming technology, however. In addition to simplicity, Spansion programmable PMICs also allow designers to set the sequence at the hardware terminals, even with electric equipment that does not have an I2C interface (see figure 3). This characteristic makes the device easy to use and also enables a free control that combines software with hardware.
Other efforts underway include PMICs for industrial and OA/communication equipment. In particular, the MB39C50X series is designed to meet the capacity and power-supply requirements for FPGA/programmable SoCs, including the Zynq-7000 All Programmable SoC from Xilinx. The PMIC can supply up to 20 A of current with a voltage accuracy of ±1％ and load regulation of ±0.3％.
The devices also come equipped with an intelligent power-supply management function that enables optimization that power source block to improve system reliability while using the necessary and sufficient small components. This function is achieved by monitoring current, notifying the system with an alert signal before an excessive current flows, and conducting appropriate system protection actions.
Bright ideas for illumination
The solid-state lighting market is on the cusp of entering the prevailing period of value-added illumination that leverages functions particular to LEDs, as opposed to simply substituting for conventional technology such as fluorescent tubes. In particular, industrial applications like streetlights and building/factory illumination call for reduced power consumption coupled with increased user friendliness. Such added values may include sensor controlled light/color adjustment that is governed by the peripheral environment.
Such approaches require controls communication that ties lighting with illumination operation panels and/or sensors. The Digital Addressable Lighting Interface (DALI) and DMX512 standards that govern the technology have already been released. Upcoming designs promise to allow homeowners adjust the lighting in their environment with their smartphones (see figure 4). That being said, embedding communication functions such as DALI into illumination would require a new communication device such as a microcontroller, and would also involve communications protocols. That scenario would require lighting designers to have knowledge and expertise in software and communications. This, in turn, would create a high entry barrier to install control communication function in illumination designs.
In order to address this issue, Spansion has developed the S6AL211A31, an LED driver IC with embedded DALI communications protocol. Because the protocol is already implemented in the hard drive, the user does not need to dabble in programming. Instead, lighting designers are free to focus on the appearance and performance of their luminaires and systems.
The driver chip integrates peripherals like LDOs that used to be located off chip, and has a light modulation/light adjustment property of 0.1% (see figure 5). Similar devices compatible with Bluetooth or DMX 512 standards are under development.
For some applications, harvesting energy from external sources can save money and increase lifetime. Energy harvesting involves transforming the light, heat, vibration, or electromagnetic waves abundant in the surroundings into electricity. The technology could be used to power the wireless sensor terminals used heavily in machine-to-machine (M2M) or Internet of Things (IoT) systems instead of batteries that require changing at regular intervals. Another industrial application involves powering sensors placed in hazardous environments that cannot be accessed without halting the system.
Although energy harvesting will realize equipment that does not require maintenance, the technology needs to overcome significant issue of the generated electricity being both miniscule and unstable. In order to overcome these issues, various manufacturers have been engaging in research and development of highly efficient power generation elements. Concurrently, an investigation into technology for efficiently utilizing limited electricity from a power generation element is also underway.
There are two approaches to addressing the latter challenge. The first approach is to develop devices that will operate even with a small amount of electricity supplied from low-electric consuming microcontrollers or wireless modules. The second approach is to develop PMICs that efficiently provide electricity to loads such as microcontrollers and wireless modules while controlling the electricity from the power-generating elements.
Because the electricity that energy harvesting PMICs will be handling is small, they require advanced technology. Not only do they need a highly-efficient conversion technology that suppresses the electricity consumption of the PMIC itself to the bare minimum, they also require the ability to track any fluctuation to the unstable electricity input. Energy harvesting is thus perhaps the market in which the technological strength of PMICs used in a variety of ways is tested the most.
In June 2014, Spansion launched the MB39C811 and MB39C831, two energy harvesting PMICs. The MB39C811 is a step-down IC compatible with two inputs. It was developed and designed for a hybrid-composition system constructed with photoelectric components that generate electricity from sunlight and room light, and oscillation elements that generate electricity from vibration. By selecting the device that fits the conditions (e.g., photoelectric-based generating elements during the day and oscillation-based generating elements at night), it can realize an energy-harvesting terminal that operates more stably. Its self-current consumption when there are no loads has been reduced to 1.5 μA and 550nA (when input = 2.5 V UVLO).
MB39C831 is a step-up IC suitable for an energy harvesting system that uses single- or multiple-cell solar batteries or a thermoelectric generator. It has a startup voltage of just 0.35 V, after which it can supply 3.0 to 5.0 V from a minimum voltage of 0.3 V. The self-current consumption when there is no load is 32 μA (constant-voltage mode). With charging voltage/current protection for a lithium-ion battery embedded inside, it does not require the addition of a device even when supplying electricity to the battery. It also has a maximum power point tracking (MPPT) function that restrains the DC/DC converter output in accordance with the maximum power point for solar batteries also used for such systems as the household solar systems. This function optimizes the efficiency of power generation.
Although modifications have been made with MB39C811 and MB39C831 to deliver more stable electricity with lower self-current consumption when there are no loads, it will be difficult to design an electricity circuit for an energy harvesting system. A capacitor needs to be installed in the front or the rear stage of the PMIC in order to stabilize the electricity. The problem is determining the size of the capacitor. To assist in the design of a power circuit that includes such peripherals of the PMIC, Spansion is releasing an energy-harvesting power circuit design tool as a function of our online circuit-design tool, Easy DesignSim. This tool will enable user to construct the optimum power circuit in accordance with a power generating element and loads in a short period of time.
We also plan a starter kit for development and evaluation purposes that combines MB39C811, MB39C831, an energy harvesting element, and a Spansion-manufactured low-electric-consumption microcontroller from our FM3 family, as well as a starter kit combined with a wireless module (see figure 6).
In the example shown, the receiver is powered by USB bus power. Connecting with a PC, receiver can get data from the transmitter. For the transmitter, the power supply is a power-generation device. The transmitter can sense and transmit ambient temperature and illumination by each sensor. It also can add other sensors using the connector, as well as connect to other RF ICs.
Among the starter kits, there are those that operate as battery-free Bluetooth low-energy (BLE) beacon tags, preparing an environment in which the user can develop a wide variety of energy-harvesting systems (see figure 7).
The latest PMIC and LED driver products boast a wide variety of functions, making use easier for a greater number of embedded designer and lighting experts. This development coincides with the shift toward greater intelligence in power sources for industrial equipment. Our objective for the future is to meet those needs by actively applying the technology we have developed for the automobile market. We will be seeing new products released one after another that will usher in the era of intelligent power.
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