Multi-phase Buck Converter with Extended Duty Cycle Bootstrap Circuit
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Solution Overview
Problem
Conventional non-isolated step-down DC-DC converters with high output current face limitations in duty ratio reduction, leading to inefficiencies and reduced performance when input voltage exceeds output voltage, particularly in buck circuits.
Innovation Solution
A multi-phase buck converter with an extended duty ratio and a bootstrap circuit is introduced, which includes switching power conversion units, bootstrap capacitors, and driving circuits to enhance duty ratio and reduce switching losses, while maintaining low cost and miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional buck circuit is used with high output current, then the current stress on switches is reduced by parallel configuration, but the switching duty ratio is reduced when input voltage is larger than output voltage, causing the circuit to operate away from optimal performance
Solution Approach 1:
The conventional single-phase buck circuit is segmented into multiple phases (first buck circuit and second buck circuit) operating in parallel. Each phase handles a portion of the total current, allowing the system to maintain high productivity while each individual switch operates at improved duty ratios. The parallel configuration distributes the current stress across multiple switches while the extended duty cycle capability of each phase optimizes switching performance.
2Loss of energy
If the switching duty ratio is reduced in conventional buck circuits, then the voltage transmission ratio is limited, but this causes increased switching loss and reduced efficiency
Solution Approach 1:
The circuit employs dynamic duty cycle extension through bootstrap circuits that actively manage the switching waveforms. The bootstrap capacitors dynamically adjust the gate drive voltages to extend the effective duty cycle beyond traditional limits, allowing the switches to operate with optimized on-times that reduce switching losses while adapting to varying input-output voltage conditions.
Solution Approach 2:
Bootstrap capacitors are introduced as intermediary energy storage elements between the power switches and the control system. These capacitors store and release energy during switching transitions, enabling extended duty cycles and reduced switching losses without requiring fundamental changes to the basic buck converter topology, thus managing the trade-off between efficiency improvement and circuit complexity.
3Ease of operation
If multiple bootstrap capacitors are added to extend duty cycle range, then the duty ratio is increased and switching loss is reduced, but the circuit complexity increases
Solution Approach 1:
The bootstrap capacitors serve multiple functions simultaneously: they extend the duty cycle range, provide gate drive energy storage, and enable efficient operation across varying voltage conditions. By making these components multi-functional, the circuit achieves extended duty ratio capability without proportionally increasing complexity, as the same elements perform multiple critical roles in the power conversion process.
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 increases duty ratio, reduces voltage jumps during switch operation, and improves efficiency by minimizing switching losses, thus enhancing the performance and applicability of the power conversion system.
Implementation Method 1
The X bootstrap circuits are electrically connected to the X power conversion circuits respectively. In each of the X bootstrap circuits and the corresponding power conversion circuit, the bootstrap circuit comprises N bootstrap capacitors and N bootstrap switches.
Data Source
AI summary
A power conversion system is provided. The power conversion system includes a power conversion circuit, a bootstrap circuit and at least N driving circuits, where N is an integer larger than 1. The power conversion circuit includes an input port, an output port, N switching power conversion units and N nodes. The switching power conversion unit includes a first switch and a second switch. The bootstrap circuit includes N bootstrap capacitors and N bootstrap switches. The N bootstrap switches are serially connected in sequence. Two ends of the bootstrap capacitor are connected to the corresponding node and the second terminal of the corresponding bootstrap switch respectively. The first terminal of the (N)th bootstrap switch receives a supply voltage. The driving circuit is connected to the corresponding bootstrap capacitor and outputs driving signals for controlling the switches according to the positive electrode voltage of the bootstrap capacitor.