PWM Controller Adjustable Minimum Duty Cycle
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Solution Overview
Problem
Conventional PWM control circuits face limitations such as insufficient power output at low power supply conditions and inefficient power utilization at high power supply conditions due to fixed or unadjustable minimum duty cycles, which fail to maintain optimal operational performance across varying voltage levels.
Innovation Solution
A PWM controller with an adjustable triangle wave signal that changes in response to power supply voltage, allowing the duty cycle to be increased under low voltage conditions and reduced under high voltage conditions, thereby maintaining efficient power utilization and ensuring sufficient power output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed minimum duty cycle is used in conventional PWM control circuits, then the circuit structure is simple, but the power output is insufficient at low power supply conditions and power utilization is inefficient at high power supply conditions
Solution Approach 1:
The patent applies the dynamics principle by making the minimum duty cycle adjustable rather than fixed. The triangle wave signal's upper and lower limit voltages are dynamically adjusted based on power supply voltage levels, allowing the PWM control circuit to adapt its minimum duty cycle to varying power supply conditions. This resolves the contradiction by enabling the circuit to change its characteristics in response to operating conditions without requiring a completely different circuit design for each scenario.
Solution Approach 2:
The patent implements parameter changes by modifying the upper and lower limit voltages of the triangle wave signal based on power supply voltage. When power supply voltage changes, the limit voltages are adjusted accordingly, which in turn adjusts the minimum duty cycle of the PWM output. This allows the circuit to maintain optimal performance across different power supply conditions while using a single circuit architecture, thus improving adaptability without proportionally increasing complexity.
2Power
If the minimum duty cycle is increased to ensure sufficient power output at low voltage conditions, then power output is improved, but power utilization efficiency decreases at high voltage conditions
Solution Approach 1:
The patent uses dynamics to make the minimum duty cycle variable rather than fixed. By dynamically adjusting the triangle wave limit voltages based on power supply voltage levels, the system automatically increases minimum duty cycle when power supply is low (ensuring sufficient power output) and decreases it when power supply is high (improving efficiency). This single dynamic mechanism resolves the contradiction between power output and efficiency across different operating conditions.
Solution Approach 2:
The patent implements feedback by monitoring the power supply voltage and using it to adjust the triangle wave limit voltages, which in turn adjusts the minimum duty cycle. This closed-loop approach ensures that the minimum duty cycle is automatically optimized based on actual power supply conditions, resolving the contradiction by ensuring sufficient power output when needed while maintaining efficiency when power supply is abundant.
3Adaptability or versatility
If the triangle wave signal is adjusted in response to power supply voltage changes, then duty cycle adaptability is improved, but the control circuit complexity increases
Solution Approach 1:
The patent applies universality by designing a single triangle wave generation circuit that performs multiple functions: generating the triangle wave signal and simultaneously providing adaptability to power supply voltage changes. By integrating the voltage-dependent adjustment directly into the triangle wave generation process, the circuit achieves duty cycle adaptability without requiring separate control circuits for each function, thus improving adaptability while limiting the increase in overall complexity.
Data Source
AI summary
A pulse width modulated (PWM) controller includes a triangle wave generation circuit generating a triangle wave signal to oscillate between an upper limit voltage and a lower limit voltage. The upper limit voltage and the lower limit voltage are adjustable in response to changes in the power supply voltage. A pulse generation circuit is coupled to the triangle wave generation circuit and a minimum duty cycle setting voltage, and is configured to generate a PWM pulse signal with a minimum duty cycle determined by the relative magnitude of the triangle wave signal and the minimum duty cycle reference voltage. In an embodiment, the minimum duty cycle is increased when the power supply voltage is lower than a predetermined reference voltage.