Switched Mode Power Supply Off-Time Control for Power Factor Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Switched mode power supplies face inefficiencies when AC input voltage and current are out of phase, leading to wasted power, as existing power factor correction methods do not effectively synchronize these components.
Innovation Solution
The implementation of a switched mode power supply that controls switching circuitry to turn on and off over multiple cycles, using a bias signal and turn-off circuitry to wait for specific time periods before turning off the switching circuitry, ensuring that AC voltage and current remain in phase, thereby maximizing power factor and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If power factor correction circuitry is added to shape AC input current to be in phase with AC input voltage, then power efficiency is improved, but device complexity increases
Solution Approach 1:
The patent combines the power factor correction function with the existing switching controller circuitry by adding turn-off circuitry that uses the bias signal to control the timing of switching transistor turn-off. This integration allows the same controller to perform both switching regulation and power factor correction, reducing overall device complexity while maintaining improved power efficiency.
Solution Approach 2:
The turn-off circuitry waits for a predetermined time period after the bias signal transitions high before turning off the switching transistor. This preliminary timing action ensures that the AC input current is shaped to be in phase with the AC input voltage, achieving power factor correction before the switching cycle completes, thereby improving power efficiency without requiring separate correction circuitry.
2Loss of energy
If switching circuitry is turned on and off over multiple cycles with controlled timing, then AC voltage and current remain in phase maximizing power factor, but control complexity increases
Solution Approach 1:
The turn-off circuitry monitors the bias signal generated by the switching controller and uses this feedback to determine when to turn off the switching transistor. By waiting for the predetermined time period after the bias signal transitions, the circuit automatically adjusts the switching timing to maintain AC voltage and current in phase, achieving power factor maximization through feedback-based control without requiring complex external control mechanisms.
Data Source
AI summary
A switched mode power supply may include circuitry configured to output a bias signal that turns off and on switching circuitry of the switched mode power supply. The circuitry may wait for a first time period determined by the bias signal, and output the bias signal to turn off the switching circuitry when the time period expires. In addition or alternatively, the circuitry may begin waiting for a second time period when the bias signal turns off the switching circuitry. The circuitry may turn on the switching circuitry either when energy in inductive storage circuitry is depleted or when the second time period expires.