Dielectric Absorption Compensation in LDO Regulators
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Solution Overview
Problem
Low dropout voltage regulators face regulation errors due to dielectric absorption in output load capacitors, leading to inefficiencies and potential loss of voltage control, especially in battery-powered devices like smartphones and tablets where power efficiency is crucial.
Innovation Solution
A dielectric absorption current compensation circuit is introduced, which generates a profile current to counteract the recharging current of the load capacitor, either analog or digital, to maintain stable voltage levels by mirroring the dielectric absorption current, ensuring continuous time or discrete level compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a low dropout voltage regulator is used to minimize saturation of the output pass transistor, then area efficiency is improved, but dielectric absorption effects cause regulation errors and loss of voltage control
Solution Approach 1:
The patent applies preliminary anti-action by introducing a compensation circuit that generates a counter-current equal and opposite to the dielectric absorption current. This compensation current is injected into the output node in advance to counteract the harmful recharging effect of dielectric absorption, thereby preventing voltage regulation errors before they occur. The circuit monitors the output voltage and activates the compensation mechanism when dielectric absorption effects are detected.
2Use of energy by moving object
If the output voltage is dynamically adjusted to minimize power consumption, then power efficiency is improved, but dielectric absorption causes excessive voltage rise and loss of regulation
Solution Approach 1:
The patent implements feedback by continuously monitoring the output voltage of the low dropout regulator and using this information to control the compensation circuit. When the output voltage deviates from the target value due to dielectric absorption, the feedback mechanism adjusts the compensation current accordingly. This closed-loop control ensures that voltage regulation precision is maintained even when dynamically adjusting power efficiency settings.
3Ease of manufacture
If a discrete load capacitor is used in the low dropout regulator, then implementation is simplified, but dielectric absorption phenomena cause regulation errors
Solution Approach 1:
The patent introduces an intermediary compensation circuit between the load capacitor and the output node. This intermediary circuit generates a compensation current that mediates the harmful effects of dielectric absorption. By placing this compensation mechanism in the signal path, the system maintains the simplicity of using a discrete load capacitor while achieving improved voltage regulation accuracy through the mediating compensation current.
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
This solution effectively compensates for dielectric absorption, maintaining stable output voltage and preventing unregulated conditions, thus enhancing the power efficiency and longevity of battery-powered devices by minimizing energy loss and maintaining voltage control.
Implementation Method 1
Dielectric absorption, also called dielectric relaxation or capacitor soaking, is the tendency of a capacitor to recharge itself after being discharged.
Data Source
AI summary
A circuit and method provides compensation for disturbance of an output voltage caused by dielectric absorption of a load capacitor of a low dropout voltage regulator after a modification of the output voltage level of the low dropout voltage regulator. A dielectric absorption current compensation circuit generates a profile current that is applied to an output of the low dropout voltage regulator and in parallel with the load capacitor to compensate for the dielectric absorption current. The dielectric absorption current compensation circuit has a programmable profile current generator that generates the profile current. A switchable current mirror transfers a mirror profile compensation current to the load capacitor to compensate for the dielectric absorption current. In some embodiments, the profile current is a continuous profile dielectric absorption compensation current and in other embodiments, the profile current is a digital profile dielectric absorption compensation current.