Adaptive Pre-Driver Circuit for LDO Stability
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Solution Overview
Problem
Conventional low dropout regulators (LDOs) face instability in frequency response due to large parasitic capacitance and output current variations, especially under heavy loads, leading to inadequate voltage regulation.
Innovation Solution
An adaptive pre-driver circuit that generates a bias current varying with output current, adjusting output impedance and frequency response to maintain stability across varying loads, comprising an amplifier, adaptive pre-driver, driving circuit, and negative feedback circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the transistor circuit area is increased to provide large output current capability, then the driving capability is improved, but the parasitic capacitance increases causing frequency response instability
Solution Approach 1:
The patent applies dynamics by making the bias current of the pre-driver transistor variable rather than fixed. The bias current dynamically adjusts based on the output current demand, allowing the pre-driver to provide appropriate drive strength across different operating conditions without requiring a large fixed-size transistor that would introduce excessive parasitic capacitance.
Solution Approach 2:
The patent changes the parameter of bias current from a fixed value to a variable value that depends on the output current. This is achieved through a bias current generation circuit that produces a current proportional to the output current, thereby adjusting the pre-driver's output impedance and driving capability to match the actual load requirements.
Data Source
AI summary
Disclosed is a circuit for voltage regulation, the circuit including: an amplifier operable to generate an amplifier output signal according to a reference voltage and a negative feedback voltage; an adaptive pre-driver operable to generate a bias current according to the amplifier output signal or according to the amplifier output signal and a current-dependent signal that varies with the variation of an output current, in which the bias current varies with the variation of the output current; a driving circuit operable to generate an output voltage and the output current according to the amplifier output signal; and a negative feedback circuit operable to generate the negative feedback voltage according to the output voltage. Since the bias current varies with the variation of the output current, the output impedance of the adaptive pre-driver varies with the variation of the output current so that the stability of the circuit is improved.