Power Saving Techniques in Embedded Systems

Embedded systems are becoming more prevalent in our daily lives, and their power consumption plays a crucial role in their performance and lifespan. Whether it’s a portable device or an industrial sensor, embedded systems generate heat and consume power during operation. In today’s energy-conscious world, it is essential to optimize power consumption in these systems to conserve energy and extend their lifespan. Embedded systems are prime targets for power efficiency, as they may require long battery life, specific form factor requirements or rely on power from a grid or generator. In this blog post, we will discuss various power-saving techniques that can be used to optimize power consumption in embedded systems.

Some key concepts related to power management and power efficiency in embedded systems:

1. Low Power Mode

Low power modes in embedded systems refer to different operational states where the system is able to reduce its power consumption in order to conserve energy. These modes are used to reduce power consumption when the system is not performing any critical tasks or when it is in an idle state.

Here are a few examples of low power modes that can be used in embedded systems:

1. Sleep mode: In this mode, the core of the system is shut down and only a few peripherals are active. This mode is used when the system is not performing any critical tasks and is waiting for an event to occur.
2. Standby mode: In this mode, the core and most peripherals are shut down, this mode is used when the system is not performing any critical tasks and is waiting for an event to occur and the system needs a longer period of time in an idle state.
3. Deep Sleep mode: This mode is a more aggressive version of the sleep mode where the system enters a very low power state, this mode is used when the system is not performing any critical tasks and is waiting for an event to occur, and the system needs a longer period of time in an idle state than standby mode.
4. Hibernation mode: This mode is similar to the deep sleep mode, but it also saves the state of the system, this mode is used when the system needs to be off for a long period of time, and the system needs to restore the state when it comes back.

It’s worth noting that each low power mode has its own advantages and disadvantages, depending on the application, the system’s power consumption, and the time it takes to wake up from that mode.

2. Clock Gating

Clock gating is a power management technique that is used to reduce power consumption in embedded systems, particularly microcontroller-based systems. The basic idea is to turn off the clock signal to certain parts of the system that are not currently in use, in order to conserve power. This can be done by shutting down the clock signal to specific peripherals or memory regions, or by gating off the clock signal to the entire core of the microcontroller.

When a clock signal is not needed for a certain function, it can be shut off. This is called clock gating. This technique can be applied to individual peripherals, to memory regions, or even to the entire core of the microcontroller. By shutting off the clock signal to these parts of the system, power consumption can be reduced.

Clock gating can be implemented in different ways:

1. Software control: Clock gating can be implemented using software control, where the clock signal to specific peripherals or memory regions is controlled by register writes or software libraries. This approach allows for flexibility and ease of implementation, but it can also add overhead to the system.
2. Hardware control: Clock gating can be implemented using dedicated clock gating logic built into the microcontroller, this can be done by using multiplexers, AND gates or OR gates. This approach typically has lower overhead compared to software control and it’s more efficient, but it may be more difficult to implement and can limit the flexibility of the system.
3. Power domains: Clock gating can be implemented by dividing the system into different power domains, each with its own clock tree and independent power-on/off control. This allows for fine-grained control over the clock signal to different parts of the system.

3. Dynamic Voltage & Frequency Scaling (DVFS)

Dynamic voltage and frequency scaling (DVFS) is a technique that adjusts the voltage and frequency of the system based on the workload, in order to reduce power consumption. The basic idea is to operate the system at the lowest voltage and frequency that can support the current workload. By reducing the voltage and frequency, less power is consumed, which results in less heat being generated and longer battery life.

DVFS can be implemented in different ways depending on the embedded system:

1. Software control: DVFS can be implemented using software control, where the voltage and frequency are adjusted by register writes or software libraries. This approach allows for flexibility and ease of implementation, but it can also add overhead to the system.
2. Hardware control: DVFS can be implemented using dedicated voltage and frequency scaling logic built into the microcontroller. This approach typically has lower overhead compared to software control and it’s more efficient, but it may be more difficult to implement and can limit the flexibility of the system.
3. Power domains: DVFS can be implemented by dividing the system into different power domains, each with its own voltage and frequency control. This allows for fine-grained control over the voltage and frequency of different parts of the system.

4. Power Efficient Firmware

Power-efficient firmware refers to software techniques that are used to reduce power consumption in embedded systems. These techniques can be used in conjunction with hardware-based power management techniques, such as low power modes and clock gating, to further optimize power consumption. Here are a few examples of power-efficient firmware techniques that can be used in embedded systems:

1. Memory access: Minimizing the number of memory accesses can help to reduce power consumption, as memory accesses are one of the most power-intensive operations in an embedded system. This can be achieved by using efficient data structures, minimizing the use of global variables, and reducing the number of pointer operations.
2. Algorithms: Using efficient algorithms can also help to reduce power consumption. For example, using a sorting algorithm that has a lower time complexity can reduce the number of operations required, and thus reduce power consumption.
3. Interrupts: Interrupts can consume a lot of power, especially if they are triggered frequently. Power-efficient firmware can minimize the number of interrupts by using software polling or by using a low-power interrupt controller.
4. Floating-point operations: Floating-point operations can consume a lot of power, especially on systems that do not have a floating-point unit. Power-efficient firmware can minimize the use of floating-point operations by using fixed-point arithmetic or by using a low-power floating-point unit.
5. Power-aware scheduler: Power-aware scheduler can be used to optimize the power consumption by scheduling the task in a way that consumes less power. For example, by scheduling the task that consumes more power in the time when the system has more power available.
6. Power-aware libraries: There are libraries available that are designed to be power-efficient, such as low-power communication libraries, low-power math libraries, and low-power sensor libraries.

5. Power Management IC (PMIC)

Power management IC (PMIC) is a type of integrated circuit that is used to control the power supply and monitor the power consumption of an embedded system. These ICs can be used to optimize power consumption and extend battery life by controlling the voltage and current supplied to different parts of the system.

PMICs can be used in a variety of embedded systems, including microcontroller-based systems, digital signal processors (DSPs), and application-specific integrated circuits (ASICs). They can be used to control the power supply to different parts of the system, such as the microcontroller, memory, and peripherals.

PMICs can be used to implement different power management techniques, such as:

1. Voltage regulation: PMICs can be used to regulate the voltage supplied to different parts of the system, such as the microcontroller and memory. This can be done by using voltage regulators or by using DC-DC converters.
2. Current monitoring: PMICs can be used to monitor the current consumed by different parts of the system, such as the microcontroller and peripherals. This can be used to optimize power consumption by shutting down parts of the system that are not currently in use.
3. Power sequencing: PMICs can be used to control the power-on and power-off sequences of different parts of the system, such as the microcontroller, memory, and peripherals. This can be used to optimize power consumption by shutting down parts of the system that are not currently in use.
4. Battery management: PMICs can be used to manage the battery, such as monitoring the battery’s state of charge, using voltage and current sensors, and implementing charging and discharge algorithms.
5. Thermal management: PMICs can be used to manage the thermal of the system, by monitoring the temperature and adjusting the power consumption accordingly.

PMICs can be used to implement these techniques in a more efficient and cost-effective way than implementing them in software or hardware. They can also be used to offload power management tasks from the microcontroller, which can free up resources and reduce power consumption.

6. Power Saving using Protocols

Power saving protocols are communication protocols that are designed to minimize power consumption in embedded systems that use wireless communication. These protocols can be used to optimize power consumption by reducing the number of transmissions, reducing the data rate, and by using low-power communication modes. Here are a few examples of power-saving protocols that can be used in embedded systems:

1. Zigbee: Zigbee is a low-power wireless communication protocol that is designed for use in embedded systems. It uses a star topology and supports multiple low-power modes, including a sleep mode that can be used to conserve power when the system is not transmitting.
2. Bluetooth Low Energy (BLE): BLE is a low-power version of the Bluetooth protocol that is designed for use in embedded systems. It uses a star topology and supports multiple low-power modes, including a sleep mode that can be used to conserve power when the system is not transmitting.
3. 6LoWPAN: 6LoWPAN is a low-power wireless communication protocol that is designed for use in embedded systems. It uses a mesh topology and supports multiple low-power modes, including a sleep mode that can be used to conserve power when the system is not transmitting.
4. Z-Wave: Z-Wave is a low-power wireless communication protocol that is designed for use in embedded systems. It uses a mesh topology and supports multiple low-power modes, including a sleep mode that can be used to conserve power when the system is not transmitting.
5. LoRaWAN: LoRaWAN is a low-power wireless communication protocol that is designed for use in embedded systems. It uses a star topology and supports multiple low-power modes, including a sleep mode that can be used to conserve power when the system is not transmitting.

7. Power Saving using peripherals

Some embedded systems have power-saving features built into their peripherals, such as UARTs, timers, and ADCs. By using these features, power consumption can be reduced.

9. Battery Management

Battery management is a technique used in embedded systems to optimize power consumption and extend battery life. Here are a few examples of battery management techniques that can be used in embedded systems:

1. Charge/discharge control: By monitoring the state of charge of the battery, the system can be configured to charge or discharge the battery at optimal times in order to extend the battery life.
2. Charge/discharge rate control: By controlling the charge and discharge rate of the battery, the system can be configured to charge or discharge the battery at a rate that is optimal for the battery’s health and life.
3. Battery monitoring: By monitoring the voltage, current, and temperature of the battery, the system can be configured to take appropriate actions to protect the battery, such as shutting down the system or reducing the load on the battery.