SIMO Buck Converter Control for Cross-Modulation Suppression
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Solution Overview
Problem
Single-inductor multiple-output (SIMO) DC-DC buck converters face issues with low transmission efficiency, significant cross modulation, large output ripple waves, small load range, and require complex controllers, limiting their application and efficiency.
Innovation Solution
A single-inductor multiple-output DC-DC buck converter design that includes i charge controllers, a phase-locked loop, a logic unit, a driving unit, and an input trunk duty ratio generation unit, which generates end flag signals and turn-on time signals to control output branch paths sequentially, utilizing a phase-locked loop and logic unit to optimize inductor current distribution and reduce cross modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ordered power-distributive control (OPDC) timing sequence is used to increase load range and reduce output ripple wave, then each load shares the inductor current, but the output voltages of other branch paths are affected when the load of a certain branch path changes, manifesting as voltage overshoot or voltage undershoot (cross modulation effect)
Solution Approach 1:
The patent divides the single inductor current into multiple independent controllable paths by introducing separate current sampling switches for each output branch. Each branch path is segmented with its own sampling capacitor and control mechanism, allowing independent regulation of current distribution while maintaining the shared inductor structure. This segmentation enables precise control over each branch's current share, reducing cross-modulation effects.
Solution Approach 2:
The patent implements current mode control with separate feedback loops for each output branch. Current sampling switches continuously monitor the inductor current contribution to each branch, and this feedback information is used by dedicated control circuits to adjust the switching timing and duty cycle of each branch. This feedback mechanism dynamically compensates for load changes and prevents voltage overshoot or undershoot in other branches.
2Adaptability or versatility
If a rechargeable battery is used as input source to provide sufficient inductor current when the last branch path is not connected to a load, then the application limitations are reduced, but the transmission efficiency decreases due to larger inductor current requirement
Solution Approach 1:
The patent employs dynamic control of the switching timing and duty cycle for each output branch based on real-time load detection. When a branch is disconnected or lightly loaded, the control system dynamically adjusts the inductor current distribution to minimize unnecessary current flow through that branch. This dynamic adaptation allows the system to maintain high efficiency across varying load conditions without requiring a rechargeable battery input source.
3Object-affected harmful factors
If charge control with independent control loop is implemented for each output branch path, then the cross modulation effect is reduced, but the controller complexity increases
Solution Approach 1:
The patent merges the control functions by using a unified current mode control architecture that manages all output branches through a common inductor current sampling point. Instead of completely independent control loops, the system combines the control mechanisms, sharing the current sensing infrastructure and using coordinated switching control. This merging approach reduces the number of separate sensing circuits while maintaining effective cross-modulation suppression through synchronized control of all branches.
Data Source
AI summary
This disclosure discloses a single-inductor multiple-output DC-DC buck converter, which includes a power conversion unit and i charge controllers, as well as a phase-locked loop, a logic unit, a driving unit, and an input trunk duty ratio generation unit. The charge controllers are connected to the driving unit through the logic unit. The logic unit is further connected to the phase-locked loop and the phase-locked loop is connected to the driving unit through the input trunk duty ratio generation unit. The driving unit is connected to the power conversion unit. The disclosure applies charge control to every output branch path, and adopts a phase-locked loop as the cycle control, which effectively suppresses the cross modulation effect of every branch path, and does not require the last branch path to have a sufficiently heavy load, which broadens the load range, while taking into account other performance requirements concurrently.