Flyback Converter Dummy Load Circuit for Internal Voltage Regulation
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Solution Overview
Problem
Flyback power converter circuits face operational failures when the internal voltage drops below a threshold, particularly in light load or no-load conditions, due to the primary side control circuit generating switching signals based on output voltage rather than internal voltage, leading to inadequate regulation of the output voltage.
Innovation Solution
Incorporating a dummy load circuit that generates a dummy load current when the output voltage falls below a predetermined threshold to ensure the internal voltage remains above the threshold, and adjusts to zero current when the output voltage exceeds the threshold, thereby maintaining normal operation of the primary side control circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the target level of the output voltage is lowered or the load circuit is in a light load condition, then the power consumption is reduced, but the internal voltage drops below the threshold causing control circuit failure
Solution Approach 1:
The patent introduces a dummy load circuit as an intermediary element between the output voltage and the internal voltage regulation mechanism. This dummy load circuit actively draws current when the load is light or absent, serving as a mediator to maintain the internal voltage at acceptable levels and prevent control circuit failure, thereby resolving the contradiction between energy saving and reliability
Solution Approach 2:
The patent dynamically changes the operating parameters of the system by adjusting the duty ratio of the switching signal based on detected internal voltage levels. When the internal voltage approaches the threshold, the system increases the duty ratio to maintain reliable operation, thus adapting parameters to resolve the contradiction between low power consumption and control circuit reliability
2Adaptability or versatility
If the duty ratio of the switching signal is reduced to match lower output voltage targets, then the output voltage regulation is adjusted, but the internal voltage becomes insufficient for normal operation
Solution Approach 1:
The patent implements a feedback mechanism where the primary side control circuit detects the internal voltage level and adjusts the duty ratio of the switching signal accordingly. This feedback loop ensures that when the output voltage target is lowered, the system responds by increasing the duty ratio to maintain sufficient internal voltage, thus preserving control circuit reliability while allowing output voltage adaptability
Solution Approach 2:
The patent makes the switching signal dynamic by continuously adjusting its duty ratio based on real-time internal voltage conditions. This dynamic adaptation allows the system to maintain reliable operation across varying output voltage targets, resolving the contradiction between adaptability and reliability
3Productivity
If the ON-period of the PWM signal is shortened to regulate output voltage at target level under light load, then the output voltage is maintained, but the internal voltage drops below threshold during OFF-period
Solution Approach 1:
The patent utilizes periodic action through the dummy load circuit that operates during the OFF-period of the PWM signal to draw current and maintain internal voltage. This periodic intervention ensures that even when the ON-period is shortened for efficient output regulation, the internal voltage remains sufficient for control circuit functionality
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
The dummy load circuit effectively maintains the internal voltage above the threshold, preventing operational failures and minimizing power loss by adaptively adjusting the dummy load current, ensuring reliable operation and efficient power management in varying load conditions.
Implementation Method 1
a transformer including a primary winding, a secondary winding and an auxiliary winding, which are coupled to one another via electromagnetic induction
Data Source
AI summary
A flyback power converter circuit includes: a transformer; a primary side switch, for controlling a primary winding to convert an input voltage to an output voltage and an internal voltage; a primary side control circuit, which is powered by the internal voltage; the primary side control circuit generates a switching signal according to a feedback signal, to operate the primary side switch; a secondary side control circuit, which generates the feedback signal according the output voltage; and a dummy load circuit, which is coupled to the output voltage, wherein when the output voltage drops to or is lower than a predetermined threshold, the dummy load circuit generates a dummy load current, to determine the feedback signal, so that the internal voltage is not undesirably low. When the output voltage exceeds the predetermined threshold, the dummy load circuit adjusts the dummy load current to zero current.