Adaptive ESR Low Dropout Regulator for Wide Load Stability
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Solution Overview
Problem
Conventional low dropout regulators (LDOs) face instability over a larger range of load currents due to fixed equivalent series resistance (ESR) or pseudo-ESR, leading to poor load regulation and phase margin issues.
Innovation Solution
Incorporating a resistive device with a negative threshold transistor that adjusts resistance based on load current, acting as an adaptive pseudo-ESR to maintain stability across varying load currents without additional quiescent current or load transient degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a fixed ESR or pseudo-ESR is used in the LDO, then the stability is improved at a specific load current, but the phase margin deteriorates when load current varies significantly
Solution Approach 1:
The patent applies the Dynamics principle by implementing a resistive device whose resistance value dynamically changes with load current. The resistive device includes a transistor operating in different regions (linear region at high load currents, saturation region at low load currents) to provide different resistance values, thereby maintaining stability across a wide load current range rather than being fixed at a single value
Solution Approach 2:
The patent applies the Parameter changes principle by changing the resistance parameter of the resistive device based on load current conditions. The resistance value is adjusted dynamically - higher resistance at low load currents and lower resistance at high load currents - to optimize the zero location in the transfer function and maintain adequate phase margin across varying operating conditions
2Stability of the object's composition
If a poly resistor is used to provide pseudo-ESR for stability, then the phase margin is improved, but the DC accuracy deteriorates due to IR drop
Solution Approach 1:
The patent applies the Local quality principle by creating different electrical characteristics at different locations/conditions in the circuit. The resistive device provides high resistance (for stability) only when needed for phase margin at low load currents, while presenting low resistance (to minimize IR drop) at high load currents. This localized adaptation of resistance quality resolves the conflict between stability and DC accuracy
3Stability of the object's composition
If a larger ESR is used, then the stability is improved, but the load transient response deteriorates with larger voltage drops
Solution Approach 1:
The patent applies the Dynamics principle by making the resistance value adaptive to load conditions. During load transients, the resistive device automatically adjusts its resistance to provide appropriate damping - higher resistance to stabilize the response and lower resistance to minimize voltage drops and improve transient speed. This dynamic adjustment optimizes both stability and transient performance
Data Source
AI summary
A low dropout regulator for providing an output voltage, the low dropout regulator comprising a resistive device configured to contribute to the stability of the low dropout regulator during operation and to have a resistance that is dependent on a load current.