DC/DC Converter Control Circuit with Variable Gain Conversion
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Solution Overview
Problem
In DC/DC converters, during light load conditions, the peak current flowing into the switching transistor increases, leading to excessive magnetic flux variation in the transformer, resulting in ringing sounds and increased energy storage per cycle, which in turn causes a ripple in the output voltage.
Innovation Solution
A control circuit with a variable gain and/or level-shift conversion circuit is implemented to manage the feedback and detection voltages, allowing the peak current to be reduced, thereby suppressing transformer ringing and output voltage ripple by adjusting the conversion circuit's state based on load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switching transistor operates during light load conditions with fixed gain conversion circuit, then the output voltage can be maintained, but the peak current increases excessively causing transformer ringing and output voltage ripple
Solution Approach 1:
The conversion circuit changes its conversion ratio dynamically based on load conditions. During light load conditions, the conversion ratio is reduced to lower the peak current and magnetic flux variation, thereby suppressing transformer ringing and output voltage ripple. During medium to heavy load conditions, the conversion ratio returns to normal to ensure sufficient power supply to the control circuit.
Solution Approach 2:
The invention changes the conversion ratio parameter of the conversion circuit according to different load conditions. By detecting the load condition and adjusting the conversion ratio accordingly, the system optimizes performance across different operating states, reducing harmful effects during light load while maintaining reliability during medium to heavy load.
2Object-generated harmful factors
If the peak current is reduced during light load conditions, then transformer ringing and output voltage ripple are suppressed, but the power supply to control circuit may become insufficient
Solution Approach 1:
The conversion ratio parameter is changed based on load conditions. During light load, the conversion ratio is reduced to suppress ringing and ripple. During medium to heavy load, the conversion ratio is increased to ensure sufficient power supply to the control circuit, thus resolving the power insufficiency issue.
Solution Approach 2:
The conversion circuit dynamically adjusts its conversion ratio to match the power requirements of the control circuit under different load conditions, ensuring that power supply adequacy is maintained when needed while allowing current reduction when beneficial for suppressing harmful effects.
3Device complexity
If a fixed conversion ratio is used in the conversion circuit, then the circuit design is simple, but it cannot adapt to varying load conditions optimally
Solution Approach 1:
The conversion circuit is designed with variable conversion ratio capability, allowing it to adapt to different load conditions. The circuit includes switching elements and control logic that enable dynamic adjustment of the conversion ratio based on detected load conditions, providing adaptability while maintaining reasonable design complexity.
Solution Approach 2:
The conversion ratio parameter is made variable rather than fixed. By implementing different conversion ratios for different load conditions, the circuit achieves better adaptability to varying loads while the overall design remains practical and implementable through standard electronic components.
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 approach effectively reduces the peak current and magnetic flux variation, suppressing transformer ringing and output voltage ripple, ensuring stable operation across varying load conditions.
Implementation Method 1
a photo coupler 214. The shunt regulator 212 generates a feedback signal S11 having a level regulated such that an error between the output voltage VOUT and a predetermined target value becomes zero, and supplies the generated feedback signal S11 to a light emitting diode of the photo coupler 214. A photo transistor of the photo coupler 214 converts a light signal S12 emitted from the light emitting diode into the feedback voltage VFB depending on the feedback signal S11.
Data Source
AI summary
A control circuit of a DC/DC converter having a transformer, a switching transistor, and a detector includes: a feedback terminal receiving a feedback voltage corresponding to an output voltage of the DC/DC converter; a current detection terminal receiving a detection voltage generated in the detection resistor; a conversion circuit configured to amplify, attenuate and/or level-shift at least one of the feedback voltage and the detection voltage, wherein a gain and/or a shift of the conversion circuit are variable; and a gain controller configured to control the gain and/or the shift of the conversion circuit.