Single-Inductor Dual-Output Converter Control With Unified LQR Loop
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Solution Overview
Problem
Existing DC-DC switching converters with a single inductor and double output suffer from slow control due to the slower second control loop, leading to inefficiencies and increased complexity.
Innovation Solution
A control module that generates control signals to implement a sequence of switching periods with phase successions, including charge and discharge phases, using a linear-quadratic regulator to optimize control loop speed and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If two independent control loops are used to control charge and discharge phases, then the control can manage both energy transfer directions, but the overall control speed becomes slow due to the slower second control loop
Solution Approach 1:
The patent merges the two independent control loops into a single unified control loop that simultaneously manages both charge and discharge phases. The controller integrates the control of switching elements during charge phase and discharge phase into one coordinated system, eliminating the speed limitation imposed by the slower second control loop while maintaining the ability to control both energy transfer directions.
Solution Approach 2:
The control loop is segmented into distinct charge phase control and discharge phase control segments, each with optimized control strategies. The charge phase control operates with one set of parameters while the discharge phase control operates with another set, allowing each segment to operate at optimal speed without being constrained by the other.
2Speed
If the second control loop is made faster to match the first control loop, then control speed improves, but coupling between control loops causes instability
Solution Approach 1:
The control loop operates dynamically by adapting its behavior based on the current phase. During charge phase, the controller optimizes for fast response with one set of control parameters; during discharge phase, it switches to another set of parameters optimized for discharge control. This dynamic adaptation allows fast control without the instability that would result from permanently coupling both loops at high speed.
Solution Approach 2:
The control system employs periodic switching between charge phase control and discharge phase control modes. Each phase is controlled during its specific time window with phase-optimized parameters, creating a periodic control pattern that achieves high speed during each phase while maintaining overall system stability through the structured alternation.
3Speed
If a time base with higher frequency than switching frequency is used to increase control speed, then control performance improves, but circuit complexity and consumption increase
Solution Approach 1:
The control system uses the natural switching events and phase transitions of the DC-DC converter itself as timing references, rather than requiring an external high-frequency time base. The controller detects phase boundaries and synchronizes control actions with these natural transitions, achieving fast control response while avoiding the need for additional high-frequency timing circuitry that would increase complexity and power consumption.
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 achieves fast and stable control of the DC-DC switching converter, reducing area consumption and optimizing energy transfer without the need for high-frequency timing signals.
Implementation Method 1
an inductor L, a first output capacitor C1 and a second output capacitor C2. In use, the inductor L is subject to an input voltage Vin and the capacitors C1 and C2 are subject to two output voltages Vout1 and Vout2, respectively
Implementation Method 2
a first output capacitor C1 and a second output capacitor C2, which, in use, are subject to a first and a second output voltage, respectively
Data Source
AI summary
A DC-DC switching converter includes an electrical network with an inductor, switches and first and second capacitors subject to first and second voltages. A control module generates first and second control signals to control the switches with a sequence of switching periods implementing, for each switching period, a phase succession including: an inductor charge phase having a first duration as a function of the first control signal; a first inductor discharge phase towards the first capacitor having a second duration as a function of the second control signal; and a second inductor discharge phase towards the second capacitor. The control module couples to the electrical network to form a signal vector including signals indicative of the first and second voltages and the current. A gain stage generates the first and second control signals by multiplying the signal vector by a gain matrix for the control module forming a linear-quadratic regulator.