Electric double layer capacitor (EDLC) with balance IC
1. the development of the field of power electronics
In recent years, automotive, industrial equipment and renewable energy fields as the Center, the more attention to power electronics. Especially in the automotive field, limited by automobile exhaust emission regulations, “raising gas mileage performance” has been positioned as an important issue, and automakers are striving to carry out the research on new technologies. In order to develop more fuel-efficient vehicles, not just trying to introduce a new generation of power components to improve power conversion efficiency, also through the combination of electrical storage device with in-depth research, and strive to achieve low power consumption and high efficiency of the system as a whole.
In addition, with the Japan market led, on automobile fuel efficiency requirements are very demanding, and promoting the process of the development of more environmentally friendly vehicles. (Figure 1)
(Figure 1) States the fuel specification changes
※ Sources: of the company according to the 2013 fushiqimei general research automotive electronics components and assemblies General Survey (released on December 4, 2012)
2. new application technique of electrical storage device
With electric cars and hybrids as a representative, in the field of vehicle adopt big capacity storage devices has become increasingly popular. Is not only the past of lead batteries, lithium-ion batteries and electronic direction the whole bulk capacitor is, technology is more and more active.
Electrical storage device according to its type, in nature have different advantages and disadvantages of general differences used to be able to play its respective characteristics of use. For example, electrical storage device mentioned, first thought should be to lithium-ion batteries. Lithium-ion batteries in smart phones, Tablet PCs and laptops are widely used in computer-related products. Due to its energy density (storage capacity per unit area) performance in hybrid and electric cars, also are widely used as the main battery. (Figure 2)
(2) classification of electrical storage device
Then the recent attention in the application of the electric double-layer capacitors (hereinafter referred to as EDLC:Electric Double Layer Capacitor). EDLC performance in terms of energy density than lithium-ion batteries, but in power density (in time was able to handle the amount of power) has very good characteristics. EDLC charge/discharge efficiency, instantly providing bulk electric power. Previously, mainly installed in mobile, and small electronic devices, as in the power battery falls for CPU power supply standby power use. Over the years, around a few f EDLC products occupy the mainstream market, but recent trend of large capacity significantly, hundreds of even thousands of f f product type market share has increased gradually. (Figures 3, 4)
(3) large-capacity capacitor over market size and forecast
※ Sources: (strain) on 2013, large-capacity capacitor, Yano Economic Research Institute market survey results (July 3, 2013)
(4) electric double-layer capacitors (EDLC)
Source: Japan your indemnity Corporation
Bulk capacitor is mainly used as transient low standby power supply, renewable energy related device standby power supply when the power supply is unstable, as well as industrial equipment such as cranes and construction machinery, such as use of renewable energy installations. Its purpose might not be around common areas, but in recent years, focusing on its power density and the charging and discharging characteristics superior to those of other advantages of Electrical storage devices, has begun to applications in the automotive sector. The structural mechanism is, in part of the regenerative braking system, the energy generated by braking is filled in a short time the good charging efficiency in EDLC, and powers the car electronic system to supplement previously borne by engine power lead and battery power.
In addition, EDLC also has performance degradation caused by repeated charging and discharging less retardant low smoke features does not contain heavy metals, composition materials, compared to other storage devices with long service life, safety, environmental protection and other advantages.
Now also have begun to take advantage of these features to further their secondary batteries such as lithium-ion battery has to combine the advantages of new applications and possibilities of research.
3.EDLC balance circuits required
EDLC voltage of each battery is approximately 2.5V. For example, when used as a backup power supply 12V power supply line, to 5 or 6 AA batteries in series connection to 12V power supply. At this point, you need to make the cell voltage balancing and therefore need to control circuit balance. Because if the battery voltage is not balanced, then applied a battery voltage will be higher, leading to deterioration of battery. Because of EDLC itself has a long life characteristics and, therefore, makes battery voltage balance is to give full play to the performance characteristics of the method.
4.EDLC balance IC “BD14000EFV-C”
ROHM developed specifically for EDLC’s balance IC “BD14000EFV-C”. This product has the advantages of EDLC balance function, also have a monitoring function. Using the product, EDLC system that can build safe and excellent reliability.
Below details the main features of the product.
① the balance function integration in 1 chip to ensure high reliability and dramatically reduce the number of components
The development of BD14000EFV-C, only 1 IC control 4~6 cells of EDLC. Products using simple triage mode, shunt current value can be set through an external resistor. Through the IC itself is controlled by the on/off built-in MOS switches, enabling the cell voltage balancing. That is, only by the IC is a very simple structure easy balance feature. (Figure 5)
(Figure 5) BD14000EFV-C block diagram
For example, when such balance circuit that includes using discrete components, each cell requires complex balancing circuit, that the huge number of components. When you set the over-voltage detection circuit for improving security, also needs the appropriate components, bringing increased mounting area, management of the components increases, costs and other burdens. In addition, due to the excessive number of components used, makes a difference in ensuring the reliability of each product also becomes very difficult task.
This product will not only carry in one set of components and design for IC products, can achieve better performance and also allows the battery voltage specifications for different products of many cell-balancing circuit to achieve standardization, which contributes greatly to reducing the number of management components. (Figure 6)
(Figure 6) single-chip integration, make design easier
② convenient extensibility
According to different voltage of EDLC components, applications, charging and discharging frequency and temperature environments, will balance the voltage set to the optimum value. BD14000EFV-C by VSET0~2 3 terminal set to Low or High, you can set the balance between the 2.4V~3.1V voltage, so it can support a variety of EDLC.
Detect voltage accuracy at normal temperature (Ta=25 degrees) to ensure ± 1.0% (MAX),-under the 40~105℃ operating temperature range to ensure ± 2.0% (MAX).
Not only that, multiple BD14000EFV-C can also be connected in series to support high voltage applications (backup power supply, engineering machinery, etc). (Figure 7)
(Figure 7) supports a variety of EDLC
③ overvoltage monitoring can be divided into two tranches of the security design
Can be divided into two tranches dual monitoring voltage of EDLC battery overvoltage conditions.
VO_OVLO1 1th test Terminal voltage and output FLAG to the microcontroller. When the 2nd gear overvoltage detected value, then the VO_OVLO2 FLAG output. Therefore, no matter which cell produces signs of deterioration, are recognized by the system, and shows the battery replacement tips.
On the voltage value, 1th balance voltage can be selected from either +0.15V or +0.25V mode, 2nd gear balance voltage can be selected from either +0.3V or +0.5V mode. OVLOSEL Terminal switch for High or Low can be set up.
④ built-in battery test feature to monitor the balance
BD14000EFV-C built-in has called “battery test function” monitoring function. Internal shunt switches are working properly for all channels, output FLAG to the VO_OK Terminal. This may confirm EDLC module is fully achieved balance status.
Without this balance circuit, you need to check the processes identified in section-by-section battery balancing function for all channels are operational. Using this feature, you can identify VO_OK of output, battery balancing function is operating correctly, has reduced time and cost advantages. ROHM is currently patent pending.
⑤ without delay, to reduce unnecessary electricity consumption
In balance with the detection circuit, comparator with hysteresis-free. (Figure 8)
(Figure 8), there is no current consumption comparison of hysteresis functions
When using hysteresis comparator, discharge voltage is lower than the test voltage, when released, even if the battery voltage is lower than the detection voltage, because the balance switch is in the ON state, which leads to unnecessary diversion of current consumption. When using hysteresis comparator, test voltage and release voltage are the same, when released, once the battery voltage is below detection voltage balance switch is OFF and does not produce unnecessary diversion of current consumption. Thus, by using a comparator with hysteresis-free to achieve an efficient balance.
⑥ vehicle-quality
AEC-Q100 BD14000EFV-C specifications meet international quality standards. In-vehicle-related applications can also be rest assured that use.
5. Summary
To sum up, BD14000EFV-C to integrate requirements of EDLC balance circuit in 1 chip, excellent for ease and reliability of EDLC systems. Not only that, but also helps reduce the burden of design, shortening the development cycle. ROHM will use analog design technology accumulated over the years, promoting universal application of more environmentally friendly electricity-storage device.