Isolated Converter Control Circuit Using Secondary Wake-Up Signals
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Solution Overview
Problem
Primary controlled switching power supplies face challenges in dynamically responding to changes in output load, leading to poor dynamic performance and limited ability to decrease power losses due to delayed detection of output voltage changes and restricted frequency reduction.
Innovation Solution
A control circuit for an isolated converter that includes a secondary-side controller generating wake-up signals based on different threshold voltages for various operating modes, coupled with a primary-side feedback circuit to control the main power switch, ensuring timely adjustments to maintain output voltage stability and improve dynamic response speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If primary controlled switching power supply detects output voltage by sampling auxiliary winding voltage in every switching cycle, then the structure is simplified and product cost is reduced, but the dynamic response performance deteriorates when output load switches from light-load to heavy-load state
Solution Approach 1:
The patent divides the control function into two independent parts: a primary-side controller that generates basic switching control signals, and a secondary-side controller that detects output voltage changes and generates wake-up signals. This segmentation allows each controller to specialize in its function, with the secondary-side controller providing timely detection of output voltage changes without complicating the primary-side control structure.
Solution Approach 2:
The patent introduces a wake-up signal as an intermediary mechanism between the secondary-side output voltage detection and the primary-side switching control. When the secondary-side controller detects output voltage changes, it generates a wake-up signal that triggers the primary-side controller to adjust switching frequency, thereby transmitting output voltage information to the primary side without requiring direct primary-side detection circuitry.
2Measurement precision
If primary controlled system samples output voltage in every switching cycle, then voltage detection is continuous, but the system frequency cannot be further decreased due to dynamic response characteristics, limiting power loss reduction
Solution Approach 1:
The patent implements periodic sampling of output voltage on the secondary side, where the secondary-side controller samples the output voltage at specific intervals rather than continuously. This periodic action maintains sufficient detection accuracy while allowing the system to operate at lower switching frequencies, thereby reducing power losses associated with high-frequency switching.
Solution Approach 2:
The patent establishes a feedback loop where the secondary-side controller detects output voltage changes and sends wake-up signals to the primary-side controller. This feedback mechanism ensures that the primary-side controller receives timely information about output voltage variations and adjusts switching frequency accordingly, maintaining voltage detection accuracy while enabling frequency reduction to minimize power losses.
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 solution enhances dynamic response speed and reduces power losses by allowing for smaller output voltage decreases during dynamic loading states and lower operating frequencies in standby modes, effectively addressing the limitations of primary controlled systems.
Implementation Method 1
a transformer having a primary winding and a secondary winding
Data Source
AI summary
Controlling an isolated converter can include: controlling a first voltage signal across the secondary winding according to a wake-up signal to reflect change of an output voltage of the isolated converter; obtaining a second voltage signal representing the first voltage signal at the primary side; controlling the main power switch according to a detection result of the second voltage signal; generating the wake-up signal according to the output voltage and a first threshold voltage when the isolated converter is in a dynamic loading state of a normal operating mode; generating the wake-up signal according to the output voltage and a second threshold voltage when the isolated converter is in a load steady state of a standby operating mode; and generating the wake-up signal according to the output voltage and a third threshold voltage when the isolated converter is in a dynamic loading state of the standby operating mode.