Buck Regulator Frequency Adjustment for Low Input Voltage Stability
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Solution Overview
Problem
Buck switching regulators face challenges in maintaining a stable output voltage when the input voltage falls, leading to inefficiencies and instability due to the limitations of duty cycle adjustments based solely on pulse width modulation.
Innovation Solution
The control method and circuit adjust the switching frequency of the pulse width modulation signal by converting input voltage to charging current, determining the duty cycle based on charging current and output voltage, and increasing the on time when the off time reaches a minimum, thereby preventing output voltage from falling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the duty cycle is increased to maintain output voltage when input voltage falls, then the output voltage stability is improved, but the off time of the pulse width modulation signal reaches a minimum value and cannot be reduced further, causing the buck switching regulator to fail in transmitting enough power
Solution Approach 1:
The patent changes the switching frequency parameter of the pulse width modulation signal when the input voltage falls to a specific level and the off time reaches its minimum value. By adjusting the switching frequency, the duty cycle can be changed without being constrained by the minimum off time, allowing the regulator to maintain both output voltage stability and sufficient power transmission capability.
2Loss of energy
If the pulse width modulation signal is turned on permanently to achieve 100% power conversion efficiency, then the power conversion efficiency is improved, but the control circuit cannot operate and buffering cannot be performed
Solution Approach 1:
The patent dynamically adjusts the switching frequency based on the input voltage level and off time conditions. This dynamic adjustment allows the system to optimize power conversion efficiency by increasing the on time while maintaining sufficient off time for control circuit operation and buffering, achieving a balance between efficiency and operational capability.
3Adaptability or versatility
If the input voltage falls to a lower voltage level, then the adaptive range for input voltage is improved, but the output voltage cannot remain stable and has to fall in accordance with the input voltage
Solution Approach 1:
The patent employs parameter changes by adjusting the switching frequency when specific conditions are met (input voltage falls to a specific level and off time reaches minimum value). This allows the duty cycle to be modified independently, enabling the buck switching regulator to maintain stable output voltage even when the input voltage falls to lower levels, thus expanding the adaptive range while preserving output stability.
Data Source
AI summary
A control method for preventing an output voltage of a buck switching regulator from falling when an input voltage of the buck switching regulator falls includes: converting the input voltage into a charging current; determining a duty cycle of the buck switching regulator according to the charging current and the output voltage; and adjusting a switching frequency of a pulse width modulation signal in the buck switching regulator when the input voltage falls to a specific voltage and an off time of the pulse width modulation signal reaches a minimum value, in order to change the duty cycle to prevent the output voltage from falling.