Server Fan PWM and TACH Control During Shutdown Cooling
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Solution Overview
Problem
Conventional fan control systems in servers only operate during startup, failing to dissipate heat generated by devices like network cards when the server is shut down, which reduces reliability and security.
Innovation Solution
A system and method for controlling a fan that includes a processor, driver, power supply module, and instruction output module, allowing the fan to operate in multiple modes, including during server shutdown, by supplying power and controlling PWM and TACH pins to manage rotation speed based on mode instructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fan is controlled only during server startup in conventional mode, then the processor and driver are powered efficiently, but heat generated by operating devices like network cards during shutdown cannot be dissipated
Solution Approach 1:
The fan control system transitions from a static single-mode control to a dynamic multi-mode control system. The level control module dynamically switches between startup mode and shutdown mode based on server state, enabling the fan to adapt its operation to different thermal requirements. This dynamic control allows the fan to rotate during shutdown when needed while maintaining efficient operation during startup.
Solution Approach 2:
The system changes the operational parameters of the fan control circuit by applying different voltage levels to the PWM and TACH pins based on server state. During shutdown mode, the level control module outputs specific voltage levels to enable fan rotation even when the processor is powered off, effectively changing the electrical parameters to achieve the desired thermal management outcome.
2Use of energy by moving object
If the processor and driver are powered off during server shutdown, then energy consumption is reduced, but the fan cannot operate to dissipate heat from operating devices
Solution Approach 1:
The power supply system is segmented into separate controllable domains. The level control module independently controls power delivery to the processor/driver versus the fan motor. During shutdown, the processor and driver can be powered off to save energy, while the fan receives separate power control signals that enable it to continue operating for heat dissipation purposes.
Solution Approach 2:
The level control module acts as an intermediary between the server shutdown state and the fan operation. It receives shutdown instructions and translates them into appropriate voltage levels for the PWM and TACH pins, enabling the fan to operate independently from the processor power state. This intermediary function allows decoupling of fan operation from processor power consumption.
Data Source
AI summary
A system for controlling a fan is provided, which includes a processor, a driver, a power supply module, an instruction output module and a level control module. The power supply module is configured to supply power to the level control module when the server is started up and when the server is shut down. The instruction output module is configured to output a mode control instruction. The level control module is configured to output a first level to the PWM pin and output a second level to the TACH pin based on the mode control instruction and then control the power supply module to supply power to the processor and the driver. The processor is configured to determine a mode of the fan based on the first level and the second level and control a rotation speed of the fan based on the mode of the fan.