Constant On-Time Isolated Converter Transient Response
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Solution Overview
Problem
Conventional isolated converters with zero/pole compensation circuits face delays in load voltage stabilization due to the processor's location on the primary side and difficulty in controlling in continuous current mode with synchronous rectifiers, leading to inefficient regulation of output voltage and current.
Innovation Solution
The implementation of a constant on-time (COT) isolated converter with a processor on the secondary side that directly detects output voltage and current, using a coupling element to transmit control signals to the primary side, eliminating the need for compensation circuits and allowing independent regulation of output voltage and current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the processor is located on the primary side with zero/pole compensation circuit, then the system can regulate output voltage, but the load voltage stabilization is delayed due to signal transmission delay through photo-coupler
Solution Approach 1:
The patent uses a coupling element (transformer or optocoupler) to transmit the control signal from the secondary side processor to the primary side electronic switch. This intermediary mechanism enables direct control of the primary side switching based on secondary side voltage detection, eliminating the need for complex zero/pole compensation circuits and reducing stabilization delay.
2Stability of the object's composition
If TL431 and VM compensation circuit are used, then the loop gain and bandwidth can be compensated to reduce ripple signal, but the system complexity increases and stabilization speed decreases
Solution Approach 1:
The patent extracts and removes the complex zero/pole compensation circuit (TL431 and VM compensation) from the system. Instead, it uses a simplified approach where the processor directly detects the output voltage and generates control signals based on the detected voltage and a reference voltage, achieving voltage stabilization without the need for complex compensation components.
3Loss of energy
If synchronous rectifier is used in secondary side, then the conversion efficiency is improved, but it becomes difficult to control in continuous current mode
Solution Approach 1:
The patent implements a feedback mechanism where the processor on the secondary side directly detects the output voltage and generates control signals that are transmitted to the primary side electronic switch. This feedback loop enables precise control of the electronic switch in continuous current mode, ensuring stable operation while maintaining the benefits of synchronous rectification for high conversion efficiency.
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 enables fast load transient response and efficient regulation of output voltage and current without the complexity of gain margin and phase margin adjustments, while avoiding the use of encoders and decoders, ensuring quick stabilization and reduced component costs.
Implementation Method 1
a coupling element to transmit control signals to the primary side
Data Source
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.