Get Ahead of the Thermal Curve With Current Measurement

Thermal and power management are fundamental concerns for system control. In the relationship of the two, it is said that temperature is a lagging indicator, whereas current is a leading indicator. 

For example, in servers, if the system is not aware of the increase in current or power, the system will be late in turning on the fans to keep the heat at a more reasonable level. If a system solely relies on temperature measurement to control the fans, the system is already playing catch up with controlling system heat.

In this post, you will learn how incorporating current sensors into the system can help manage heat better and save power as compared to solely using temperature sensors and heat sinks to execute thermal management.

So, what if we could predict when the temperature on the load in a server will change?

• Can that reduce power in a server?
• How much power can be saved?

In 2018, we created a system to determine the answer to those questions.

How thermal management used to work in 2018 is represented below in the block diagram Figure 1. There was a PWM fan controller cooling a system and getting temperature information as a result. If the system temperature increased, the controller increased the fan speed according to it or might try to get ahead of it. Back then, the fans could consume 200W in a server.

Figure 1: Fan Control System in 2018

Enter the proposal for a better way, with Microchip instituting an additional feedback loop on the air-cooled load by adding a power/current sensor. The power/current sensor was measuring consumed current associated with the load and the temperature sensor continued assist with the control loop (Figure 2). While the block diagram below is simplified, implementations were created for the EMC1704 which has an integrated power sensor and four temperature sensors and alternatively for the PAC1921 and the EMC1413, which are single current sensors and triple temperature sensors respectively.

Figure 2: Fan Control System with Additional Power Monitor Feedback

So how much power was saved? From logged data, it was verified that a minimum of 19% reduction in fan power consumption was saved using predictive energy control with a current sensor. For this server customer, Microchip showed a saving of $158 reduction in operational costs for a single server over its life span.

Benefits to Using a Power/Current Sensor With Temperature Sensors for Thermal/Power Management

Predicting Temperature Increases Through Power/Current Monitroring to Improve Response

As shown in the server example, a system can improve its thermal response by using a power/current monitor. To help predict increases in temperature, we offer several families of power/current monitors. The PAC170x family combines temperature and current monitoring, featuring one current sensor and up to four temperature sensors. Additionally, the PAC1710 and PAC1720 families provide single or dual current sensor options, respectively. By using these devices to measure current, voltage and power across a sense resistor in series with the load, users can accurately monitor the energy flowing through the system at that node. An increase in measured power may indicate a potential rise in load temperature.

Optimally Managed Systems Use Less Energy

Many customers choose to use power and current sensors to characterize and prototype their system’s power consumption. However, in today’s rapidly evolving Artificial Intelligence (AI) landscape, it is difficult to predict exactly how a system will be used, as AI software and drivers are continuously being developed and updated. While it may be straightforward to determine the maximum energy consumption of a fully loaded system, forecasting optimized power consumption scenarios is much more challenging. This is where in-system power and current sensors become invaluable. By actively measuring system configurations, these sensors enable real-time evaluation and adjustment of power consumption, ensuring the system operates as efficiently as possible. For the most advanced solutions, we recently released the precision PAC195x family of devices that performs 16-bit power measurements for up to four voltage rails.

Get Extended Use From a Single Charge in Battery Applications

An ancillary benefit for battery systems is being able to use a system longer before the next charge. This has positive implications for the production floor. An example of this would be warehouse automation. In the automated storage and rereival systems, the robots need charging. As a result, up-time (the time for active use) becomes important to the cost and efficiency of the system.

Maintenance and Replacement Cycle

Reducing unnecessary use of equipment, such as server fans, offers significant benefits. Minimizing excessive or unnecessary fan cycling can extend the lifespan of these components, resulting in less frequent replacements and reduced maintenance time. In the end, the entire system’s reliability is improved.

Remote Monitoring, Diagnostics, Warranty Service

Lastly, there is value in the possibility to remotely monitor or delay unnecessary warranty service. Telematics, that is remote monitoring of power and thermal anomalies, saves money through preventing service calls.

In Summary

Incorporating current measurement into thermal management systems offers significant advantages over relying solely on temperature sensors. By enabling earlier detection of rising power consumption, current sensors help optimize cooling responses, reduce energy usage and extend equipment lifespan. Whether in server environments, battery-powered applications, or automated systems, this proactive approach leads to greater operational efficiency, cost savings and improved system reliability.

Want More?

For more information on using power/current sensors please contact the author and production line manager Mitch Polonsky at mitch.polonsky@microchip.com or go to our product landing page for power/current monitoring.