Haptic Module Power Buffering to Prevent Battery Brownout
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Solution Overview
Problem
Battery-powered electronic devices with small form factors face power output limitations due to limited battery capacity, leading to voltage drops and brownout conditions when driving low impedance haptic modules, which can cause damage or performance degradation.
Innovation Solution
A power management system with a current-limiting voltage regulator and a high-capacity output capacitor is used to stabilize the voltage supply, preventing drops and enabling peak power operation of haptic modules by buffering energy for instantaneous demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a battery-powered electronic device drives a low impedance haptic module at peak power, then haptic feedback performance is improved, but voltage drops occur causing brownout conditions and potential damage to other circuits
Solution Approach 1:
The power management system pre-charges the output capacitor to a voltage higher than the battery voltage before haptic module activation. This preliminary energy storage in the capacitor enables the system to immediately supply peak current to the haptic module without causing voltage drops that would affect other circuits, thus resolving the contradiction between peak power delivery and voltage stability.
2Volume of moving object
If a small form factor battery is used to meet device size constraints, then device compactness is improved, but power output capacity is reduced leading to voltage drops
Solution Approach 1:
The output capacitor acts as an intermediary energy storage device between the small capacity battery and the haptic module. It is pre-charged by the battery to a higher voltage and then discharges rapidly to supply peak power to the haptic module when needed. This intermediary approach enables a compact device with a small battery to still deliver high peak power without voltage drops.
3Duration of action of stationary object
If a current-limiting voltage regulator is used to protect the battery, then battery longevity is improved, but peak current delivery capability is reduced
Solution Approach 1:
The system pre-charges the output capacitor to a voltage higher than the battery voltage before haptic activation. When the haptic module needs peak power, the capacitor discharges through the current-limiting regulator, which sees a lower current demand because the capacitor's higher voltage compensates for the current limit. This allows the regulator to protect the battery while still enabling peak power delivery through the capacitor's rapid discharge capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system prevents brownout conditions, allowing haptic modules to operate at peak power without affecting other circuits, enhancing user experience by providing stable haptic feedback.
Implementation Method 1
An output capacitor separate from any output capacitors of the voltage regulator is provided such that the output capacitor couples the constant voltage supply rail to system ground. A capacity of the output capacitor is selected so as to prevent the constant voltage supply rail from dropping below a threshold voltage
Data Source
AI summary
A small form factor electronic device includes a power management system for preventing brownout conditions when driving a haptic element from a small size battery with high internal resistance. The power management system includes a high capacity output capacitor to supplement power output capacity of a current-limiting boost converter receiving as input a constant voltage from a battery.