Digital Average Current-Mode VRM Control With Auto-Tuned Compensation
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Solution Overview
Problem
Existing digital controllers for Switch-Mode Power Supplies (SMPS) are not optimized for specific tasks required by Voltage Regulator Modules (VRMs, leading to inefficiencies in die area and power consumption, and analog controllers dominate due to their ability to achieve wide control bandwidth without significant penalty.
Innovation Solution
A fully digital Average Current-Mode (ACM) controller is developed using shared hardware for voltage and current loops, employing a window delay-line ADC and hybrid DPWM, with adaptive trimming and programmable dead-time, and auto-tuning of compensator coefficients to optimize performance and reduce die area and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a digital controller is used for VRM applications, then design flexibility and scalability are improved, but die area and power consumption increase due to lack of optimization for specific SMPS tasks
Solution Approach 1:
The digital controller is segmented into specialized functional blocks (PWM generator, current loop compensator, voltage loop compensator, ADC, duty cycle register) that are optimized for specific SMPS control tasks. This segmentation allows efficient resource utilization and reduces overall die area compared to a generalized digital controller.
Solution Approach 2:
The controller implements a unified digital architecture that handles both voltage loop and current loop control functions within the same device. The shared hardware resources (ADC, compensators, PWM generator) perform multiple functions, reducing the need for separate dedicated circuits and thereby reducing die area.
2Adaptability or versatility
If a digital controller is used for VRM applications, then design flexibility and scalability are improved, but power consumption increases due to lack of optimization for specific SMPS tasks
Solution Approach 1:
The controller is divided into specialized functional blocks that process only the specific tasks required for SMPS control (voltage regulation, current limiting, PWM generation). This avoids the power overhead of executing general-purpose instructions and reduces dynamic power consumption.
Solution Approach 2:
The controller includes auto-tuning functionality that automatically optimizes compensator coefficients based on system characteristics, eliminating the need for external calibration equipment and reducing the power required for manual tuning iterations.
3Speed
If an analog controller is used, then wide control bandwidth is achieved without significant penalty in die area, but design flexibility and scalability are reduced
Solution Approach 1:
The patent replaces analog control circuitry with a fully digital control architecture. The digital controller achieves wide control bandwidth through high-speed digital processing and optimized compensation algorithms, while maintaining the flexibility to reconfigure control parameters via software or registers.
Solution Approach 2:
The controller allows dynamic adjustment of control parameters (compensator coefficients, PWM frequency, duty cycle limits) through digital registers and auto-tuning functionality. This enables the digital controller to achieve analog-like bandwidth performance while maintaining programmable flexibility for different operating conditions.
Data Source
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AI summary
A digital controller for controlling an average-current-mode voltage regulator with an output connected to a load. The controller comprises a digital voltage-sampling window Analog-to-Digital Converter (ADC), based on Delay-Lines (DLs) and configured to obtain a sample of a voltage error signal being the difference between the reference voltage and the output voltage, and to convert the voltage error signal from analog to digital representation; a digital current-sampling window ADC, based on DLs and configured to obtain a sample of the output current and to convert the current output from analog to digital representation; a digital compensator for voltage regulation, receiving as input the digital voltage error signal, configured to generate a current reference signal based thereupon; a digital compensator for current regulation, receiving as input the current error signal and the current reference signal, configured to generate a duty-ratio command signal based thereupon; and a digital hybrid High Resolution (HR) Digital Pulse Width Modulator (HR-DPWM) receiving as input the duty-ratio command signal and generating a pulse-width-modulated signal that is fed to the gates of the converter's transistors, to thereby control the current and voltage supplied to the load.