Power Converter PWM Control for Input Voltage Stability
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Solution Overview
Problem
Conventional power converters fail to maintain expected output voltages when input voltages decrease, leading to inefficiencies in voltage conversion due to fixed PWM signal periods and on/off times that cannot be dynamically adjusted.
Innovation Solution
A power converter with an input voltage detecting unit and a PWM unit that adjusts the on-time and period of the switch conducting signal based on the input voltage relative to a default voltage, increasing on-time and period when the input voltage drops below the default to ensure stable output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the PWM signal period is kept fixed, then the control structure is simple, but the output voltage cannot be maintained when input voltage decreases
Solution Approach 1:
The patent applies dynamics by making the PWM signal period variable instead of fixed. The control unit dynamically adjusts the period based on the input voltage level: when input voltage decreases, the period is extended to allow sufficient on-time for voltage conversion. This resolves the contradiction by sacrificing structural simplicity (fixed period) to achieve output voltage stability under varying input conditions.
2Reliability
If the on-time is increased to maintain output voltage, then the output voltage stability is improved, but the PWM signal period becomes excessively long
Solution Approach 1:
The patent uses dynamic adjustment of both on-time and period based on input voltage conditions. When input voltage is high, the on-time is kept short and period is normal. When input voltage decreases, the on-time is extended proportionally and the period is adjusted accordingly to maintain the appropriate duty cycle relationship. This ensures output voltage stability without unnecessarily extending the PWM period beyond what is required for proper voltage conversion.
3Reliability
If the off-time is decreased to increase on-time, then the output voltage is maintained, but the off-time reaches a minimum limit and cannot be further decreased
Solution Approach 1:
The patent dynamically adjusts both on-time and off-time based on input voltage levels. When input voltage is sufficient, normal on-time and off-time values are used. When input voltage decreases below a threshold, the controller extends the on-time and proportionally adjusts the off-time and period to maintain the required energy transfer. This prevents the off-time from being unnecessarily minimized while ensuring adequate charging time for the output capacitor.
Data Source
AI summary
A power converter and an operating method therefore are disclosed. The power converter includes an output stage, an input voltage detecting unit, and a pulse width modulation (PWM) unit. The output stage is coupled between an input terminal and a ground terminal. The input voltage detecting unit is used to detect an input voltage. The PWM unit is coupled to the output stage and the input voltage detecting unit and used to provide a PWM signal to the output stage. The PWM unit adjusts an on-time of a switch conducting signal of the PWM signal according to the input voltage and a default voltage. When the input voltage is lower than the default voltage, the PWM unit increases the on-time of the switch conducting signal and a period of the PWM signal.