Low-Power Circuit Refresh for Faster Wake-Up Transitions
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Solution Overview
Problem
Electronic devices experience significant delays when transitioning from low power mode to operational mode due to the time required to recharge parasitic capacitances, which is often inefficient with limited current availability.
Innovation Solution
A refresh controller periodically reconnects the target circuit to a voltage source for a brief duration to recharge capacitances during the suspended mode, using a Very Low Frequency Oscillator (VLFO) to time refresh operations and a counter to manage the duration, minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the electronic device is placed in low power mode by disconnecting circuitry from power source, then power consumption is reduced, but the time required to recharge parasitic capacitances introduces significant delay when converting back to operational mode
Solution Approach 1:
The refresh controller performs preliminary action by periodically reconnecting the target circuit to the voltage source during low power mode to recharge parasitic capacitances before the circuit is needed. This advance recharging reduces the delay when transitioning back to operational mode, as the capacitances are already partially or fully charged rather than requiring full recharging from discharged state.
Solution Approach 2:
The refresh controller implements periodic action by repeatedly connecting and disconnecting the target circuit to the voltage source at scheduled intervals during low power mode. This periodic refreshing maintains the parasitic capacitances at an acceptable charge level without requiring continuous power connection, thus reducing power consumption while ensuring rapid transition capability when operational mode is needed.
2Speed
If current is increased to speed up recharging of parasitic capacitances, then transition time to operational mode is reduced, but power consumption increases
Solution Approach 1:
Instead of using high current continuously, the refresh controller uses periodic action to reconnect the circuit at scheduled intervals. This allows the capacitances to be recharged in multiple smaller increments over time rather than requiring a single high-current pulse, thus achieving the necessary charge level with lower average power consumption while still enabling fast transition when needed.
Solution Approach 2:
The refresh controller performs preliminary recharging action during low power mode, so when operational mode is needed, the capacitances are already partially charged. This preliminary action reduces the remaining recharging time and current requirement, achieving fast transition without the need for high power consumption during the transition itself.
Data Source
AI summary
A target circuit of an electronic device is placed in a suspended mode by disconnecting the target circuit from one or more voltage sources. A refresh controller periodically initiates a refresh operation during the suspended mode by temporarily reconnecting the target circuit to the one or more voltage sources for a duration sufficient to recharge capacitances of the target circuit. The refresh controller terminates the refresh operation by disconnecting the target circuit from the one or more voltage sources, thereby continuing the suspended mode of the electronic device. The refresh controller can employ a Very Low Frequency Oscillator (VLFO) to time the frequency of refresh operations. The VLFO manages the refresh initialization timing based on the voltage across a capacitor that is selectively charged or discharged so as to implement the refresh operation. The refresh controller further can employ a counter to time the duration of the refresh operation.