Time-Based Digital LDO Regulator for Ripple and Transient Control
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Solution Overview
Problem
Conventional digital LDO regulators face accuracy issues with output voltage due to quantized switch adjustment, suffer from limit cycle oscillation, and have slow transient response speeds due to the use of comparators and quantized switch control.
Innovation Solution
A time-based digital LDO regulator with a switch array, feedback circuit, voltage-controlled oscillators, and a switch driver that dynamically adjusts switch turn-on and turn-off times based on frequency differences between reference and feedback voltages, allowing continuous adjustment of the number of enabled switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the number of turned-on switches is quantized for control, then the device complexity is reduced, but the output voltage accuracy decreases
Solution Approach 1:
The patent applies dynamics by transitioning from static quantized switch control to dynamic continuous control. The VCO generates continuous frequency signals that dynamically adjust the number of enabled switches based on the voltage error between reference and feedback voltages, eliminating quantization effects and improving output voltage accuracy while maintaining manageable device complexity through systematic control architecture.
2Device complexity
If the number of turned-on switches is adjusted one by one every rising edge of a clock, then the device complexity is reduced, but the transient response speed becomes slow
Solution Approach 1:
The patent employs periodic action through the VCO-generated clock signals with varying frequencies. Instead of adjusting switches one by one at a fixed clock rate, the system uses periodic VCO cycles whose frequency varies dynamically with voltage error magnitude, enabling multiple switch adjustments per VCO cycle and significantly accelerating transient response while keeping the control mechanism systematic and manageable.
Solution Approach 2:
The system dynamically adjusts the VCO frequency based on voltage error magnitude. When a large voltage error exists, the VCO operates at higher frequency, enabling faster switch adjustments and improving transient response. This dynamic frequency modulation allows the system to adapt its response speed to the severity of the voltage deviation without increasing structural complexity.
3Ease of operation
If a comparator is used to regulate the output voltage, then the ease of operation is improved, but a limit cycle oscillation phenomenon occurs causing output ripple increase
Solution Approach 1:
The patent replaces the traditional comparator-based mechanical switching control with an electronic VCO-based continuous control system. The VCO generates analog frequency signals that continuously modulate the switch array, eliminating the abrupt on/off switching behavior of comparators that causes limit cycle oscillations and output ripple, while maintaining ease of voltage regulation through the systematic control architecture.
Data Source
AI summary
A regulator includes a switch array, a feedback circuit, first and second voltage-controlled oscillators, and a switch driver. The switch array generates an output voltage based on a number of enabled switches from among a plurality of switches. The feedback circuit generates a feedback voltage which depends on a level of the output voltage. The first voltage-controlled oscillator generates a first signal having a first frequency which depends on a difference between a reference voltage and the feedback voltage. The second voltage-controlled oscillator generates a second signal having a second frequency which depends on a difference between the feedback voltage and the reference voltage. The switch driver determines a turn-on time point of each of the plurality of switches based on the first signal and determining a turn-off time point of each of the plurality of switches based on the second signal.