Constant On-Time Isolated Converter Feedback Delay
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Solution Overview
Problem
Conventional isolated converters face challenges in quickly stabilizing load voltage due to delays in feedback signal transmission from the secondary side to the primary side, and they struggle to operate efficiently in continuous current mode with synchronous rectifiers, requiring complex compensation circuits and encoding/decoding technologies.
Innovation Solution
A constant on-time isolated converter design that allows direct detection and transmission of output voltage and current from the secondary side to the primary side, eliminating the need for compensation circuits and encoding/decoding, and utilizing a processor with a coupling element to control the electronic switch based on feedback signals, enabling fast regulation of output voltage and current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional isolated converters use voltage divider design with photo-coupler for feedback, then the system can transmit control signals between primary and secondary sides, but the load voltage cannot be stabilized quickly due to delay in signal transmission
Solution Approach 1:
The patent extracts the controller from the primary side and relocates it to the secondary side, where it can directly detect the load voltage without transmission delay. This extraction of the control function to the secondary side eliminates the feedback delay inherent in conventional designs that use photo-couplers for signal transmission between sides.
Solution Approach 2:
The patent implements direct voltage detection on the secondary side where the controller measures the actual load voltage and immediately adjusts the switching duty cycle accordingly. This direct feedback mechanism eliminates the delay caused by conventional feedback transmission through photo-couplers and voltage dividers, enabling rapid load voltage stabilization.
2Reliability
If conventional converters use TL431 and VM compensation circuit, then the loop gain and bandwidth can be compensated to reduce ripple signal, but the device complexity increases and the voltage still cannot be stabilized quickly
Solution Approach 1:
The patent removes the complex TL431 and VM compensation circuitry from the design. By relocating the controller to the secondary side and implementing direct voltage detection, the system achieves rapid stabilization without requiring these complicated compensation mechanisms, thereby reducing device complexity while maintaining or improving voltage stability.
Solution Approach 2:
The controller on the secondary side directly detects and regulates the load voltage without needing external compensation circuits. The system becomes self-regulating, where the controller automatically adjusts based on real-time voltage measurements, eliminating the need for complex compensation networks that would otherwise be required to achieve similar stability.
3Loss of energy
If synchronous rectifier is used in the secondary side, then the conversion efficiency can be improved, but it becomes difficult to control in continuous current mode (CCM)
Solution Approach 1:
The patent implements direct voltage detection and feedback control on the secondary side, where the controller continuously monitors the load voltage and adjusts the synchronous rectifier switching in real-time. This direct feedback mechanism enables precise control of the synchronous rectifier in continuous current mode, overcoming the control difficulties while maintaining high conversion efficiency.
Solution Approach 2:
The controller dynamically adjusts the switching duty cycle of the synchronous rectifier based on real-time load voltage measurements. This dynamic control approach enables the system to operate efficiently in continuous current mode by continuously optimizing the rectifier switching timing and duration, overcoming the static control limitations of conventional designs.
4Ease of operation
If controller is located on the primary side, then the electronic switch can be controlled, but the controller cannot detect the load voltage directly resulting in slower response
Solution Approach 1:
The patent extracts the controller from the primary side and places it on the secondary side, where it can directly access and measure the load voltage. This relocation eliminates the need for indirect voltage detection through photo-couplers and voltage dividers, enabling the controller to detect load voltage immediately and respond without transmission delay.
Solution Approach 2:
The patent eliminates the photo-coupler intermediary that previously separated the controller from direct voltage measurement. By placing the controller on the secondary side, the system removes the isolation barrier that caused detection delay, allowing direct voltage sensing while still maintaining system isolation through alternative means.
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 allows for rapid load transient response and independent regulation of output voltage and current on the secondary side without the need for complex compensation or encoding/decoding, improving efficiency and stability.
Implementation Method 1
a transformer is used to convert the high voltage AC power to low voltage DC power
Implementation Method 2
After coupling the AC power with rectifiers, a transformer is used to convert the high voltage AC power to low voltage DC power
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
The present invention discloses a constant on-time isolated converter comprising a transformer with a primary side and a secondary side. The primary side is connected to an electronic switch and secondary-side is connected to a load and a processor. The processor is connected to a driver on primary side through at least one coupling element and to the electronic switch. The processor receives an output voltage or an output current across the load generating a control signal accordingly. The driver receives the control signal through the coupling element and accordingly changes the ON/OFF state of the electronic switch, regulating the output voltage and the output current via the transformer, where the duration of the ON/OFF state of the electronic switch is determined between the moment control signal changes from negative to positive and the moment it changes from positive to negative to achieve a high-speed load transient response.