Flyback Power Supply Controller Voltage Derivative Sensing
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Solution Overview
Problem
Flyback switching mode power supplies in capacitive discharge ignition systems are costly due to the need for extra components to sense currents and voltages for discontinuous conduction mode operation, and they are sensitive to cost variations, as they typically operate with uncharged capacitive loads similar to short circuits, diverging from traditional SMPS control methods.
Innovation Solution
A controller for flyback switching mode power supplies that senses the output voltage and its derivative to determine when to turn on the switch, eliminating the need for additional voltage-to-current converters and allowing for cycle-by-cycle voltage control, thereby reducing costs and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional current sensing methods are used to control discontinuous conduction mode, then reliable mode operation is achieved, but device complexity and cost increase due to extra components
Solution Approach 1:
The patent extracts the voltage sensing function from the traditional current sensing approach. By sensing only the output voltage across the capacitor and eliminating the need for current sensors and voltage-to-current converters, the solution reduces device complexity while maintaining reliable discontinuous conduction mode operation through voltage derivative detection
Solution Approach 2:
The voltage sensing circuit serves multiple functions: it detects the output voltage level, determines the voltage derivative (rate of change), and controls the switching timing. This multi-functional approach replaces the need for separate current sensing and control circuits, reducing overall system complexity
2Device complexity
If voltage control method is implemented, then device complexity is reduced, but measurement precision requirements increase
Solution Approach 1:
The patent applies preliminary action by detecting the voltage derivative (rate of change) before the voltage reaches its peak. This allows the controller to anticipate the charging completion point and turn off the switch at the optimal moment, achieving precise control without requiring high-precision direct voltage measurement at the peak point
3Loss of energy
If discontinuous conduction mode is maintained, then energy transfer efficiency is improved, but heat dissipation increases due to frequent switching
Solution Approach 1:
The patent implements periodic action through cycle-by-cycle voltage control, where the switch is turned on and off in discrete cycles based on voltage derivative detection. This periodic switching maintains discontinuous conduction mode for efficient energy transfer while the brief on-times minimize continuous power dissipation, reducing overall heat generation
Solution Approach 2:
The controller dynamically adjusts the switching timing based on real-time voltage derivative detection. By adapting the switch on/off moments to the actual charging rate, the system optimizes energy transfer efficiency in each cycle while minimizing excessive current flow and associated heat dissipation
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 solution reduces implementation costs and heat dissipation by using voltage control to manage energy transfer from the transformer to the capacitor, optimizing power throughput and efficiency in capacitive discharge ignition systems.
Implementation Method 1
Energy accumulated in the transformer at the primary winding during an on state of the switch, it is released by the transformer at the secondary winding during an off state of the switch. The reversal of the voltage induced across the secondary winding, which is a consequence of a sudden collapse of a magnetic flux in the transformer
Implementation Method 2
a current may flow from the secondary winding to the capacitor, thereby discharging the transformer at the secondary winding and charging the capacitor
Data Source
AI summary
A controller used to control a flyback switching mode power supply. The flyback switching mode power supply is constructed to charge a capacitor, and includes a rectifying device, a series arrangement of a switch and a primary winding of a transformer for receiving an input voltage, and a secondary winding of the transformer for charging the capacitor via the rectifying device to an output voltage. The controller is configured to sense the output voltage and to turn on the switch when the change of the output voltage over time becomes smaller than a predetermined threshold. By using the controller to sense and use the output voltage across the capacitor to turn on the switch, a controlled flyback switching mode power supply that makes use of voltage control is realized.