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Lowest System Power Consumption
Innovative Architecture for Lowest System Power Consumption
Abstract
Innovative architecture for lowest system power consumption. Reducing the power consumption is in every designer mind. Today two trends are evident:
• LED lighting finds its way into the households replacing incandescent an fluorescent bulbs
• Smart control of the light, key words: home automation, motion detection, presence detection With introducing LEDs the power reduction made a quantum step andhave potential to get more efficient over the coming few years. Consider that light is needed just a fraction of the day the stand-by power accounts for a remarkable share of the total power needs. The following approach addresses this by looking into the system architecture. The combination of an ultra low power real time clock (RTC) communicating the system microcontroller can make the difference.
Landscape
The automation is finding its place not only in high-tech building, but penetrates now to offices and homes. Smart home, connected home are key words in this field, managed by central control unit with a smart user interface. In the basic versions dominantly on-off functions were controlled. Meanwhile distributed intelligence is optimal to control the parameter at the spot of use or occurrence. One of the key applications is the ambient light control in a room or in a section of the room. The criteria for light control are:
- Light needed: automatic control during active hours e.g. working hours
- Light wanted: user wants to turn on the light
- Light intensity: use only as much light as needed to be comfortable
- Ambient light: account for ambient light coming from outside, less LED light near the window, compared to back in the room These functions are for instance easily delegated to a small controller near or in the light fixture.
After looking in the physical placing, let’s look focus on the timing aspects. The different tasks of a lighting system to cover:
- We want to be able to turn on the light with no sensible delay
- In the off time or stand-by time the power consumption should be ideally zero
- Most of the time the power should essentially be (almost) switched off
To resolve the first point the microcontroller must be initiated to perform the task in reasonable time triggered from the light switch, entry senor or from the central home controller. For doing this we can allow to take time of some hundreds of milliseconds. Essential: it is not required to be able to activate within a fraction of a microsecond. The human eye cannot sense it much faster, respectively a small delay isn’t deranging.
Architecture
The activation rhythm is typically controlled by system microcontroller. It is selected to perform the task optimally. The request to reduce power consumption is followed, but it in most cases there is room to cut it down even further, but how and at what cost?
In principle stay in power down and just check periodically for actions to execute.
Figure 1 Basic Blocks
Estimate the on / off ratio of the system. In many cases the on time is magnitudes smaller than the off time. Therefore saving power during the off-time is key.
The use of an ultra low power RTCs enables to totally new system architecture. It allows to cut the system power consumption to a minimum. What are the main elements?
In most systems the microcontroller is using the on-chip RTC and runs in power down mode. It typically uses still 2…10μA (fig. 2). By transferring the ‘authority to the ultra low power RTC the microcontroller can be set to hibernation mode and just some 0.1μA are used to keep the RTC running. The wake-up pattern can be programmed optimally to suit the application.
Figure 2 Conventional Architecture
Estimate the on / off ratio of the system. In many cases the on time is magnitudes smaller than the off time. Therefore saving power during the off-time is key.
The use of an ultra low power RTCs enables to totally new system architecture. It allows to cut the system power consumption to a minimum. What are the main elements?
In most systems the microcontroller is using the on-chip RTC and runs in power down mode. It typically uses still 2…10μA (fig. 2). By transferring the ‘authority to the ultra low power RTC the microcontroller can be set to hibernation mode and just some 0.1μA are used to keep the RTC running. The wake-up pattern can be programmed optimally to suit the application.
To continue reading this white paper from NXP, please follow the link below:
http://lowpowerrtc.interfacechips.com/tpl/rtc/pdf/NXP_LowSystem_PowerConsumption.pdf
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