LDO Dynamic R-C Network for Wide-Load Transient Recovery
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Solution Overview
Problem
Low dropout regulators (LDOs) face a challenge in achieving a good transient response while minimizing quiescent current and circuit area, as smaller load capacitors and lower quiescent current can lead to degraded transient performance.
Innovation Solution
The proposed solution involves a voltage regulator circuit with a dynamic R-C network and adaptive biasing, which includes transistors and amplifiers to sense load current and adjust impedance dynamically, allowing for increased drive current and improved transient response without increasing quiescent current or circuit area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a larger output capacitor is used to reduce transient output voltage drop, then transient response is improved, but circuit area and cost increase
Solution Approach 1:
The patent implements a dynamic R-C network that automatically adjusts its impedance characteristics based on operating conditions. During transient events, the network dynamically changes to provide lower impedance for faster response, while in steady-state it maintains higher impedance to minimize quiescent current. This dynamic adaptation eliminates the need for large fixed capacitors, achieving good transient response with smaller output capacitors.
Solution Approach 2:
The patent changes the impedance parameter of the R-C network dynamically through bias current control. By varying the bias current, the effective resistance and time constant of the R-C network are adjusted in real-time to optimize transient response. This parameter modulation allows the circuit to achieve fast transient recovery without requiring large capacitance values, thus reducing circuit area.
2Use of energy by moving object
If quiescent current is reduced to improve power efficiency, then power efficiency is improved, but transient response degrades
Solution Approach 1:
The patent employs periodic or event-driven current boosting through the dynamic R-C network. Instead of maintaining high quiescent current continuously, the circuit injects additional current dynamically during transient events detected by the control circuitry. This periodic/action-on-demand approach maintains low average quiescent current for power efficiency while providing high current availability when needed for transient response.
Solution Approach 2:
The patent uses feedback control to monitor output voltage and detect transient conditions. When a transient is detected, the feedback loop automatically activates the dynamic R-C network to compensate for the voltage drop. This feedback mechanism ensures that low quiescent current is maintained during normal operation while transient response is preserved through automatic correction when needed.
3Area of stationary object
If output capacitance is minimized to reduce circuit area, then circuit area is reduced, but transient response and stability are degraded
Solution Approach 1:
The patent introduces a dynamic R-C network as an intermediary element between the LDO output and ground. This intermediary network provides additional current sourcing capability during transients without requiring large output capacitors. The R-C network acts as a buffer that supplements the output capacitance, enabling small capacitors to achieve the same transient performance as large capacitors would provide alone.
Data Source
AI summary
Described embodiments include a voltage regulator circuit comprising an output voltage terminal configured to be coupled to a load that draws a load current, first and second amplifiers, and first, second, third, fourth and fifth transistors. The embodiment also includes a dynamic R-C network coupled between the third amplifier input and the seventh transistor current terminal, wherein the dynamic R-C network includes capacitors and MOS-based resistors, a third amplifier having a fourth amplifier input and a third amplifier output, wherein the fourth amplifier input is coupled to the output voltage terminal, and a capacitor that is coupled between the output voltage terminal and the fourth amplifier input.