Adaptive Phase-Lead Compensation Circuit for LDO Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In low-dropout linear regulator (LDO) design, especially with high power supply ripple rejection (PSRR) and low noise product, existing adaptive phase-lead compensation methods fail to effectively enhance phase margin due to variable load conditions and limitations in using the Miller Effect.
Innovation Solution
An adaptive phase-lead compensation circuit that utilizes a voltage-controlled resistor (VCR) and a Miller capacitor, allowing adjustable resistance to be connected to any nodes in the circuit, enabling load-adaptive zero tracking and the use of the Miller Effect for improved compensation without requiring special fabrication processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed capacitor in series with a resistor is used for phase-lead compensation, then the circuit structure is simple, but the phase margin is not enhanced much under variable load conditions
Solution Approach 1:
The patent applies the Dynamics principle by replacing the fixed resistor with a voltage-controlled resistor (VCR) whose resistance value dynamically adjusts based on the load current. The VCR is controlled by a control voltage that varies with load conditions, enabling the compensation circuit to adapt its characteristics in real-time. This dynamic adjustment allows the circuit to maintain adequate phase margin across a wide range of load currents, from light to heavy loads, resolving the contradiction between structural simplicity and phase margin reliability under variable loading.
2Adaptability or versatility
If a transistor is used to sense load current and provide adaptive resistance, then the compensation adapts to load conditions, but the Miller Effect cannot be utilized
Solution Approach 1:
The patent applies the Intermediary principle by introducing a voltage-controlled resistor (VCR) as an intermediary element between the load current sensing mechanism and the Miller capacitor. The VCR acts as a mediator that translates load current variations into corresponding resistance changes, which in turn modulate the effectiveness of the Miller Effect. This intermediary approach enables both load adaptability and Miller Effect utilization, as the VCR allows the Miller capacitor to dynamically influence the compensation based on actual load conditions without requiring direct transistor-based adaptive resistance that would block Miller Effect application.
3Adaptability or versatility
If adaptive phase-lead compensation is implemented with variable load current, then the compensation must track load conditions, but existing methods fail under no load or light load conditions
Solution Approach 1:
The patent applies the Parameter changes principle by dynamically varying the resistance parameter of the compensation circuit based on load current magnitude. The voltage-controlled resistor changes its resistance value as a function of the control voltage, which is derived from the load current. Under heavy load conditions, the resistance decreases to provide appropriate phase lead; under light or no load conditions, the resistance increases to maintain compensation effectiveness. This parameter modulation enables the compensation circuit to track load conditions while maintaining reliability across the entire operating range.
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 provides enhanced phase margin, load-adaptive zero tracking, and improved efficiency by allowing the Miller Effect to be used across a wide range of load currents, addressing the limitations of existing methods.
Implementation Method 1
a capacitor provides the Miller Effect and the resistor provides a fixed zero in the frequency domain
Data Source
AI summary
An adaptive phase-lead compensation (zero) circuit is disclosed that can be added to a circuit (e.g., a CMOS-based LDO) to ease the compensation and increase the phase margin of the circuit. By using the disclosed adaptive phase-lead compensation circuit, an adjustable resistance can be connected to any nodes in the compensated circuit rather than just to the voltage source (VDD) or ground (GND), allowing the Miller Effect to be used via a Miller capacitor.