Dynamic Miller Compensator for Charge Pump Bandwidth
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Solution Overview
Problem
High-speed switched capacitor DC-DC converter circuits face challenges in frequency response and stability due to the Miller effect, which restricts bandwidth and requires careful pole placement to maintain stability.
Innovation Solution
A pre-regulated charge pump circuit incorporating a Miller compensator with a zero-pole proportional to the square root of the output current, along with a variable impedance circuit and error amplifier, is used to enhance bandwidth and stability by dynamically adjusting impedance and feedback voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a Miller compensator is used in a high-speed switched capacitor DC-DC converter, then stability is improved, but bandwidth is restricted due to the Miller effect
Solution Approach 1:
The patent implements dynamic compensation by making the compensator's pole location variable rather than fixed. The pole frequency is dynamically adjusted based on the output current of the charge pump, allowing the system to adapt its stability characteristics across different operating conditions. This dynamic adjustment enables maintaining stability while achieving wider bandwidth compared to traditional fixed Miller compensators.
Solution Approach 2:
The patent changes the parameter of the compensator pole frequency from a fixed value to a variable value that depends on output current. By implementing a compensation network where the effective pole location shifts with operating conditions (specifically with output current), the system resolves the trade-off between stability and bandwidth. The variable impedance elements allow the compensator to present different effective impedances at different operating points.
2Device complexity
If the zero-pole is fixed in the Miller compensator, then circuit design is simplified, but frequency response performance deteriorates
Solution Approach 1:
The patent transitions from a static compensator design to a dynamic one where the zero-pole characteristics adapt to operating conditions. The compensator includes variable impedance elements that automatically adjust the effective pole and zero locations based on the charge pump's output current, improving frequency response without requiring complex manual tuning for different operating points.
Solution Approach 2:
The compensator automatically adjusts its characteristics based on the output current of the charge pump without requiring external intervention or complex control circuits. The variable impedance elements are directly coupled to the charge pump output, allowing the compensator to self-adjust its pole-zero locations according to the actual operating conditions, thereby optimizing frequency response across the full operating range.
Data Source
AI summary
An apparatus is provided. The apparatus comprises an error amplifier that amplifies the difference between a reference voltage and a feedback voltage, a first variable impedance circuit coupled to the error amplifier that receives a control voltage from the error amplifier, a charge pump coupled to the variable impedance that receives an input voltage from the variable impedance, and a Miller compensator coupled to the charge pump and to the first variable impedance circuit. The Miller compensator receives the output voltage and output current from the charge pump. It also outputs the feedback voltage, adjusts the control voltage, and has a zero-pole that is proportional to a power of the output current of the charge pump.