Single Inductor Buck-Boost Converter with Voltage-to-Time Control
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Solution Overview
Problem
Existing DC-DC converters require separate inductors for buck and boost voltage conversions, increasing circuit complexity and size, while also being inefficient in managing varying voltage requirements in portable systems.
Innovation Solution
A DC-DC converter design utilizing a single inductor and an H-bridge circuit with multiple switches, controlled by a circuit that cycles through phases to produce both buck and boost voltages, leveraging feedback loops and current sensing to manage the inductor current effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate inductors are used for buck and boost voltage conversions, then voltage conversion reliability is improved, but device complexity and size increase
Solution Approach 1:
The patent combines two separate DC-DC converter circuits (buck and boost) into a single integrated circuit that shares a common inductor. The H-bridge configuration allows the same inductor to serve both buck conversion (when switches S1 and S2 are closed) and boost conversion (when switches S3 and S4 are closed), thereby reducing component count and circuit complexity while maintaining the reliability of voltage conversion through dedicated switching control for each mode.
Solution Approach 2:
The common inductor in the H-bridge circuit performs multiple functions: it serves as the energy storage element for both buck voltage conversion and boost voltage conversion. The control circuit universally manages the switching of all four switches (S1-S4) to adapt the inductor's function based on whether buck or boost mode is required, making the inductor a universal component for both voltage conversion directions.
2Loss of energy
If separate inductors are used for buck and boost converters, then voltage conversion efficiency is improved, but the quantity of components increases
Solution Approach 1:
The patent merges the inductor components of separate buck and boost converters into a single shared inductor within an H-bridge configuration. This reduction in component count directly addresses the worsening feature while the dedicated switching paths for buck (S1-S2) and boost (S3-S4) modes preserve conversion efficiency by preventing cross-interference between the two conversion functions.
Solution Approach 2:
The control circuit implements periodic switching sequences that alternate between buck mode operation and boost mode operation. During buck operation, switches S1 and S2 are closed while S3 and S4 remain open; during boost operation, switches S3 and S4 are closed while S1 and S2 remain open. This periodic switching ensures that the common inductor is used efficiently for one function at a time, maintaining conversion efficiency while reducing overall component quantity.
3Device complexity
If a single inductor is used for both buck and boost conversions, then device complexity is reduced, but control difficulty increases
Solution Approach 1:
The patent merges buck and boost converter functions into a single H-bridge circuit with a common inductor, reducing device complexity. To manage the increased control difficulty, the control circuit uses a state-machine approach that systematically cycles through defined operational phases, ensuring proper sequencing of the four switches (S1-S4) and preventing invalid switching states that could damage the circuit or reduce efficiency.
Solution Approach 2:
The control circuit incorporates feedback mechanisms that monitor the operational state of the H-bridge and adjust switching sequences accordingly. This feedback allows the control circuit to detect whether the system is operating in buck mode or boost mode and to transition smoothly between modes by appropriately controlling the closure and opening of switches S1-S4, thereby managing control difficulty while maintaining simple circuit architecture.
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
This solution simplifies the circuitry, reduces component count, and efficiently generates both buck and boost voltages from a single inductor, addressing the complexity and inefficiency of existing systems by enabling flexible voltage management in portable devices.
Implementation Method 1
During the on state, the energy storage element begins to store energy. For example, when the energy storage element is an inductor, current increases and responsive thereto, the inductor produces an opposing voltage across its terminals. During the off state, the switch is open and the inductor becomes a current source.
Implementation Method 2
A first phase may include a buck charging current passing through the inductor, while a second phase (following the first phase) may include a boost charging current passing through the inductor. A third phase (following the second phase) may include a boost discharge current passing through the inductor, while a fourth phase (following the third phase) may include a buck discharge current passing through the inductor.
Data Source
AI summary
A control system with a voltage-to-time converter for combined buck-boost converter using a single inductor. The system includes a voltage-to-time converter circuit having first and second inputs coupled to receive first and second voltage signals, respectively. The voltage-to- time converter includes a comparator configured to compare the first voltage signal and the second voltage signal and to generate a comparator output signal at a first level if the first voltage is greater than the second voltage and at a second level if the second voltage is greater than the first voltage. The voltage-to-time converter further includes an output circuit configured to generate first and second output signals based on the comparator output signal. The output circuit is configured to provide a selected one of the first or second output signals at the first level for a duration dependent on a difference between respective voltages of the first and second voltage signals.