Switched LDO Regulator Control for Fast Response and Low Ripple
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Solution Overview
Problem
Designing analog circuits in advanced process technologies is complicated due to high-speed transistors, which require efficient voltage regulation with minimal ripple and variable temperature response, and existing hysteretic control methods often result in overcharging and voltage ripple issues.
Innovation Solution
A digital switched low-dropout regulator with a slow control loop that adjusts the strength of power transistors based on pulse separation, using a strength controller with a pulse position detector and adjustment circuit to increment or decrement transistor strength, and a digital control device to manage load current changes, thereby controlling the charge transfer and minimizing voltage ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing hysteretic control methods are used, then voltage regulation is achieved, but overcharging and voltage ripple issues occur
Solution Approach 1:
The patent implements a feedback mechanism by monitoring the output voltage and comparing it against reference voltages (Vref_high and Vref_low). The controller adjusts the power transistor switching state based on this feedback, turning the transistor ON when voltage drops below Vref_low and OFF when it exceeds Vref_high, thereby eliminating overcharging and reducing voltage ripple while maintaining stable regulation
Solution Approach 2:
The patent employs dynamic switching control where the power transistor operates in a switched mode rather than continuous conduction. The transistor's on/off state dynamically adjusts based on real-time voltage conditions, enabling the system to adapt to load changes and minimize ripple by controlling charge transfer timing and magnitude
2Speed
If process technology scales to lower dimensions, then transistor speed increases, but analog circuit design complexity increases
Solution Approach 1:
The patent replaces complex analog control circuits with a digital control implementation. The controller uses digital logic to monitor voltage levels and generate switching signals, substituting analog voltage dividers, comparators, and continuous control circuits with a simpler digital state machine that achieves the same regulation function with reduced design complexity despite faster transistor speeds
3Power
If power transistor strength is increased, then current delivery capability improves, but voltage ripple increases
Solution Approach 1:
The patent uses periodic switching action to control power transfer. Instead of continuous conduction that causes ripple, the power transistor switches periodically between ON and OFF states, with the duty cycle adjusted based on load conditions. This periodic operation allows current delivery capability to be maintained while minimizing voltage ripple through controlled charge transfer intervals
Data Source
AI summary
High-resolution switched digital regulators are disclosed having fast cross corner and variable temperature response, with constrained ripple. The strength of the power transistors utilized by the regulator are adjusted to control the current delivered to the load. The regulators utilize a slow control loop in parallel with a primary fast switching loop. The slow loop uses the switching signal of the primary loop to estimate the load current and set the power transistor size accordingly.