Processor Fast Voltage and Frequency Throttling for Low Battery
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Solution Overview
Problem
The maximum current output from a battery limits the high-frequency operation of processors, leading to delayed transitions into low power modes, which negatively impact user experience and require large decoupling capacitors, increasing system cost.
Innovation Solution
A mechanism for fast dynamic capacitance, frequency, and voltage throttling is implemented through a dedicated pin that triggers a direct transition to low power mode, bypassing conventional processes, allowing processors to maintain operation with reduced performance parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional power mode transition process is used, then system stability is maintained, but transition time to low power mode becomes too long (300 μS or more)
Solution Approach 1:
The system performs preliminary detection of battery power levels and pre-configures throttling parameters before a power crisis occurs. The power management agent continuously monitors battery status and pre-calculates appropriate frequency and voltage thresholds, so that when power drops below the threshold, the processor can immediately enter low power mode without waiting for conventional transition procedures.
Solution Approach 2:
The patent implements a fast response mechanism that skips the conventional multi-stage power mode transition process. When the power management agent detects that battery power has dropped below the threshold, it directly triggers the processor to jump to the appropriate low power mode without executing the standard sequential transition steps, thereby reducing transition time from 300 μS to approximately 10 μS.
2Reliability
If large decoupling capacitors are used to maintain voltage during power transitions, then voltage stability is improved, but bill-of-material cost increases
Solution Approach 1:
By implementing fast dynamic capacitance, frequency, and voltage throttling that reduces transition time to approximately 10 μS, the system minimizes the duration during which decoupling capacitors must maintain voltage. This allows the use of smaller decoupling capacitors since they need to sustain voltage for a much shorter period, thereby reducing bill-of-material cost while maintaining adequate voltage stability.
Solution Approach 2:
The system dynamically adjusts frequency and voltage parameters in real-time based on battery power levels. When power drops below the threshold, the processor immediately transitions to lower frequency and voltage states, changing operational parameters to match available power. This dynamic adaptation reduces the energy storage requirement during transitions, allowing smaller decoupling capacitors.
3Productivity
If processor operates at maximum frequency, then performance is maximized, but battery power consumption increases beyond available capacity
Solution Approach 1:
The power management agent continuously monitors battery power levels and dynamically adjusts processor operating parameters including frequency and voltage. When battery power is sufficient, the processor operates at maximum frequency for optimal performance. When power drops below the threshold, the system automatically reduces frequency and voltage to match available power capacity, ensuring continuous operation without exceeding battery limits.
Solution Approach 2:
The system implements a feedback mechanism where the power management agent continuously monitors battery power levels and adjusts processor frequency and voltage accordingly. This closed-loop control ensures that processor power consumption never exceeds battery capacity, automatically scaling performance up or down based on real-time power availability while maintaining optimal operation within constraints.
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
A dedicated pin of a processor or system-on-chip (SoC) is used to indicate whether power level (e.g., charge, voltage, and/or current) of a battery falls below a threshold. The threshold can be predetermined or programmable. The battery is used to provide power to the processor and/or SoC. Upon determining that the power level of the battery falls below the threshold, the processor by-passes the conventional process of entering low performance or power mode, and directly throttles voltage and/or operating frequency of the processor. This allows the processor to continue to operate at low battery power. The fast transition (e.g., approximately 10 µS) from an active state to a low performance or power mode, in accordance with a logic level of the voltage on the dedicated pin, reduces decoupling capacitor design requirements, and makes it possible for the processor to adapt higher package power control settings (e.g., PL4).