SIMO DC-DC Converter Dynamic Mode Switching
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Solution Overview
Problem
Typical Single-Inductor-Multiple-Output (SIMO) converters operate only in discontinuous conduction mode, limiting their ability to utilize inductor saturation current and resulting in inefficient power delivery due to large inductor current ripple, which restricts their maximum load current capability.
Innovation Solution
A controller for SIMO DC-DC converters that dynamically selects between Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM) based on load conditions, using a current-mode control scheme to manage inductor current waveforms and switch configurations, allowing for efficient time-sharing of the inductor to support higher current levels and improve efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If SIMO converters operate only in discontinuous conduction mode (DCM), then the control is simplified, but the inductor saturation current rating cannot be fully utilized and maximum load current capability is limited
Solution Approach 1:
The converter dynamically switches between DCM and CCM based on load conditions. The controller monitors the inductor current and automatically transitions between conduction modes to optimize performance across different operating ranges, allowing the system to adapt its behavior rather than being fixed in one mode
Solution Approach 2:
The converter changes its operating parameters by transitioning between DCM and CCM. In DCM, the inductor current reaches zero during each cycle, while in CCM, the current remains continuous. This parameter change allows full utilization of the inductor saturation current rating and improves maximum load current capability
2Device complexity
If SIMO converters operate in discontinuous conduction mode (DCM), then the control is simpler, but efficiency is reduced due to large inductor current ripple
Solution Approach 1:
The system dynamically adjusts its operating mode based on load conditions. Under heavy load conditions, it transitions to CCM where the inductor current ripple is smaller, thereby improving efficiency. Under light load conditions, it operates in DCM with simpler control
Solution Approach 2:
The converter changes its current waveform characteristics by switching between DCM and CCM. In CCM, the continuous current mode reduces the amplitude of current ripple compared to DCM, thereby reducing resistive losses and improving overall power efficiency
3Productivity
If the maximum load current capability is increased by increasing peak current, then the load capability improves, but the pulse-width must be decreased to maintain constant output voltage ripple
Solution Approach 1:
The controller dynamically adjusts the pulse-width based on the operating mode and load conditions. In CCM, different pulse-width modulation strategies are applied compared to DCM, allowing the system to maintain constant output voltage ripple while supporting higher load currents without fixed constraints
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
The solution enables SIMO converters to operate efficiently across varying load conditions, maximizing inductor energy storage capability and supporting higher current levels while maintaining stable output voltages, thus overcoming the inefficiencies of traditional DCM SIMO converters.
Implementation Method 1
Single-Inductor-Multiple-Output (SIMO) converters use one inductor to regulate multiple output voltages by time sharing the inductor
Implementation Method 2
The controller has a first and second output adapted to control electronic switches coupled to a first and second output filter
Data Source
AI summary
A controller for a SIMO DC-DC converter operable in CCM and DCM receives a signal representative of an inductor current, and signals representative of a first and a second DC-DC converter output. The controller has a first and second output adapted to control electronic switches coupled to a first and second output filter, and a third and fourth output adapted to control current in an inductor. The controller controls the outputs based upon the inputs by determining a desired PWL inductor current and current waveform, and determines pulsewidths of the outputs, to match the inductor current to the desired PWL. A timer controls pulsewidths of the outputs and the controller dynamically selects DCM or CCM to maintain the first and second DC-DC converter outputs at predetermined levels. In embodiments, the desired PWL inductor current is one or both of a desired valley current and a desired peak current.