Hysteretic Pulse Modulation for Multi-Level Converter Charge Balance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Three-level and higher order switching converters face challenges in maintaining charge balance and voltage stability for flying capacitors, leading to voltage misbalances and poor transient response, which inhibits the realization of high efficiency switching power supply applications.
Innovation Solution
The control circuitry generates pulse width modulated signals with adjustable duty cycles to control the output signal, adjusting switch states within switching cycles to discharge or charge the capacitor, and employs hysteretic comparators to regulate flying capacitor voltage independently of the output control loop, ensuring charge balance without disturbing the output regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If one phase is modulated to regulate the flying capacitor voltage, then the flying capacitor voltage stability is improved, but the output regulation loop speed decreases and transient response becomes poor
Solution Approach 1:
The patent divides the control function into two independent parts: one phase (e.g., phase A) is dedicated to regulating the flying capacitor voltage through hysteretic control, while the other phase (e.g., phase B) handles output voltage regulation. This segmentation allows each loop to operate independently at its optimal speed without interfering with the other, resolving the contradiction between flying capacitor stability and output regulation speed.
Solution Approach 2:
The patent introduces an intermediary control mechanism where the hysteretic comparator directly controls the switching states of specific transistors (e.g., Q1 and Q2) to regulate the flying capacitor voltage, while a separate PWM controller handles output regulation. This intermediary approach allows independent control of flying capacitor voltage without disturbing the output control loop, maintaining both stability and response speed.
2Stability of the object's composition
If valley-mode control is used to regulate the flying capacitor voltage, then the flying capacitor voltage stability is improved, but it does not work for voltage conversion ratios approaching unity
Solution Approach 1:
The patent employs hysteretic control with adjustable hysteresis bandwidth parameters that can be dynamically modified based on the voltage conversion ratio. This allows the control system to maintain stable flying capacitor voltage regulation across the entire operating range, including extreme cases where the voltage conversion ratio approaches unity, unlike fixed valley-mode control which fails in these conditions.
Solution Approach 2:
The hysteretic control mechanism dynamically adjusts the switching states based on real-time flying capacitor voltage measurements and hysteresis band thresholds. This dynamic adaptation enables the system to maintain stability across varying voltage conversion ratios, providing versatility that static valley-mode control cannot achieve.
3Power
If three-level and higher order switching converters are used, then power density increases and switching loss decreases, but charge balance and voltage stability of flying capacitors become difficult to maintain
Solution Approach 1:
The patent implements feedback control through hysteretic comparators that continuously monitor the flying capacitor voltage and provide real-time feedback to adjust the switching states. This feedback mechanism automatically corrects any voltage deviations, maintaining charge balance and voltage stability while enabling the system to operate at high power density with reduced switching losses.
Solution Approach 2:
The hysteretic control mechanism provides self-regulating behavior where the flying capacitor voltage automatically returns to the desired range through the inherent hysteresis action, without requiring complex external intervention. This self-service capability maintains voltage stability while allowing the converter to operate at optimal power density.
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 approach effectively maintains flying capacitor voltage stability and balance, enhancing the efficiency and power density of multi-level power conversion systems while minimizing the impact on output voltage and inductor current loops.
Implementation Method 1
Hysteretic pulse modulation for charge balance of multi-level power converters
Data Source
AI summary
In described examples of methods and control circuitry to control a multi-level power conversion system, the control circuitry generates PWM signals having a duty cycle to control an output signal. The duty cycle is adjustable in different switching cycles. States of the system's switches are adjustable in one or more intervals within the switching cycles. In response to a voltage across a capacitor of the system being outside a non-zero voltage range, the control circuitry adjusts states of the switches in two intervals to discharge or charge the capacitor in a given switching cycle.