Switched-Mode Power Supply Overvoltage Protection Circuit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing switched-mode power supplies face complexity in implementing effective overvoltage protection across both light-load and constant-load conditions due to the need for additional load detection circuits and photocouplers, which complicates the structure and limits reliable operation.
Innovation Solution
A switched-mode power supply design incorporating a transformer with a primary winding, secondary winding, and auxiliary winding, along with a switching controller, overvoltage protection circuit, and load increase circuit, which adjusts the drive voltage to control switching operations and increases the load on the secondary side when necessary, enabling overvoltage protection without requiring complex structures or load detection circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switched-mode power supply uses a fixed overvoltage detection level, then the structure is simple, but overvoltage protection cannot be achieved under light-load conditions due to coupling rate variations
Solution Approach 1:
The patent changes the overvoltage detection level parameter dynamically based on load conditions. When light load is detected, the detection level is adjusted to a higher value to account for the reduced coupling rate between windings, enabling accurate overvoltage protection across different operating conditions without adding complex hardware
Solution Approach 2:
The existing overvoltage detection circuit is made multi-functional by adding a load detection function and adaptive detection level adjustment. The same detection circuit serves both overload protection and light-load identification purposes, eliminating the need for separate dedicated circuits
2Reliability
If the switched-mode power supply adds load detection circuit and photocoupler to detect light load and change overvoltage detection level, then overvoltage protection under light load is achieved, but the structure becomes complicated
Solution Approach 1:
The patent makes the existing overvoltage detection circuit multi-functional by integrating load detection capability into it. The detection circuit monitors both the auxiliary winding voltage for overvoltage conditions and detects light-load conditions through the same voltage sensing mechanism, eliminating the need for separate load detection hardware
Solution Approach 2:
The patent merges the load detection function and overvoltage detection function into a single integrated circuit operation. By combining these functions in one circuit, the patent avoids adding separate photocouplers and dedicated load detection circuits, thus achieving protective functionality without increasing structural complexity
3Use of energy by moving object
If the switched-mode power supply operates under light-load conditions, then energy consumption is reduced, but the coupling rate between windings decreases causing inaccurate overvoltage detection
Solution Approach 1:
The patent adjusts the overvoltage detection level parameter based on the detected load condition. Under light-load conditions where coupling rate is reduced, the detection level is increased to compensate for the lower induced voltage in the auxiliary winding, maintaining accurate overvoltage detection across all load conditions while preserving energy 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 design allows for reliable overvoltage protection on the secondary side under both light-load and constant-load conditions by dynamically adjusting the load and drive voltage, ensuring efficient operation without the need for additional load detection circuits or photocouplers, thus simplifying the power supply structure.
Implementation Method 1
an alternating current (AC) voltage induced to the auxiliary winding
Implementation Method 2
The voltage generator circuit is configured to rectify and smooth an alternating current (AC) voltage induced to the auxiliary winding
Implementation Method 3
The transformer includes a primary winding on the primary side, a secondary winding on the secondary side
Implementation Method 4
The switching element is connected to the primary winding of the transformer. The switching controller is configured to control switching operation of the switching element
Data Source
AI summary
A switched-mode power supply includes a transformer, a switching element, a switching controller, a voltage generator circuit, an overvoltage protection circuit, and a load increase circuit. The overvoltage protection circuit is configured to, when a first DC voltage outputted from the voltage generator circuit is below a predetermined voltage, apply a first drive voltage to an input terminal of the switching controller, and to, when the first DC voltage exceeds the predetermined voltage, apply a second drive voltage, which is different from the first drive voltage, to the input terminal, whereby the switching controller stops controlling switching operation. The load increase circuit is configured to, when the output voltage exceeds a threshold voltage, flow a current from the secondary side, thereby increasing a load applied to the secondary side. The threshold voltage is less than a rated voltage of the transformer and greater than the target voltage.