For any battery-powered IoT applications, power consumption and battery life optimization are key design requirements.
Battery life must be taken into consideration right at the beginning of the development phase. If not, unexpected circumstances may occur. In fact, battery life is crucial for devices used in the health sector, such as pacemakers, where any failure might cost a life.
“Most companies do not define their use-case and therefore fail to meet market needs. They usually focus on adding extra features for their device and they don’t take battery life into account. Meanwhile, they miss to focus on the primary goal of the device.”Wilfried Dron, CEO/Founder of Wisebatt.
Before anything else, the use case of your device must be defined precisely.
Here are some of the most effective ways to optimize the battery life of connected devices.
1. Use an LDO regulator
Our first tip is to place a regulator between the system (sensor, MCU, radio) and the battery. This is used to ensure correct behavior, but diminishing the voltage of the component might also provide longer battery life.
In electronics, a regulator is a component used to maintain a steady voltage. The efficiency of the linear regulator depends on the difference between the input and output voltage. It relies also on the current drawn. The more the difference between input and output voltage, the greater the heat dissipated. To overcome this problem of heat dissipation, LDOs can be used by lowering the voltage drop.
To understand how to use an LDO, consider the following architectures consisting of a battery and a regulator.
The formula to calculate power dissipation is Pdiss= (Vin – Vout) * I.
To calculate the power used by the linear regulator, we need to know these three parameters.
- Vin – input of the regulator
- Vout – output of the regulator
- I – current drawn from the circuit
Let’s say we have a system powered on 3.3V and drawing 140 mA. In order to optimize battery life, we can split the power rails into two as shown in the diagram. Then we can connect the second rail directly to the output of the first rail. By doing so, we can achieve equal dissipation of heat and a more balanced aging of the components.
2. Use a buck regulator
There are three types of switching converters available for stepping up and stepping down DC voltages : the boost converter, the buck converter and the buck-boost regulator.
A Buck is used to stepping down a given input voltage. It is a switching regulator which converts a higher voltage input to lower voltage output.
Using a Buck regulator is a great way to step down voltage However, it can make a high frequency noise.
Buck boost regulators work when the supply voltage is greater or lower than the output voltage.
3. Use a load switch
Another technique for battery optimization is to consider switching off loads when they are not used. In our example we will use two load switches:
- One of the switches is placed between the power rail of the radio and the microcontroller.
- The other one is placed between the power rail of the sensor and the microcontroller.
These two switches are controlled by the microcontroller.
Most load switches have four pins:
- Input voltage
- Output voltage
- Logic level enable
When the load switch is enabled through its ON pin, current flows from the input (source) voltage pin to the output (load) voltage pin. The switch is turned on/off by applying a simple logic level signal.
4. Power down unused peripherals
Turn off the unused peripherals of your microcontroller, pulse-width modulator, ADC converter, and other components. The latter should preferably initialized each time they require an action . Such a measure can minimize power outage and leakage. Therefore, every small saving can lead to a substantial increase of the battery life.
5. Get a bigger battery
With these four techniques, you can achieve a good optimization of your battery life. In case you can’t enhance it enough, you can simply get a bigger battery. We advise you to rely on this only when you have no other option.
Any electronic device should be designed in a way that allows it to save power as much as possible. Engineers must carefully look for the battery drain in every mode of operation of the device. It becomes vital to optimize the battery life of the device to have an increased power saving performance.
Using these basic tips can help improve your hardware design with a low-power consumption and a longer battery life.