Switching Power Supply Adaptive Overcurrent Protection
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Solution Overview
Problem
Conventional switching power supply apparatuses that switch between multiple output voltages and include an overcurrent limiting function often select components based on the maximum output current, leading to inefficiencies and waste when the output voltage is low, as the overcurrent limit threshold and maximum switching frequency remain constant regardless of the output voltage.
Innovation Solution
A switching power supply apparatus that adjusts the overcurrent limit value and maximum switching frequency based on the output voltage, setting a higher value for high output voltages and a lower value for low output voltages, allowing for optimized component selection and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the overcurrent limit threshold and maximum switching frequency are kept constant regardless of output voltage, then the power supply can handle maximum power demands, but components are oversized and power consumption increases when output voltage is low
Solution Approach 1:
The patent applies dynamics by making the overcurrent limit threshold and maximum switching frequency variable rather than fixed. The control circuit dynamically adjusts these parameters based on the detected output voltage level, allowing the power supply to optimize its operation for each voltage condition. This resolves the contradiction by enabling the system to maintain reliable overcurrent protection at high voltages while reducing power consumption at low voltages through adaptive parameter adjustment.
Solution Approach 2:
The patent directly applies parameter changes by modifying the overcurrent limit threshold and switching frequency parameters according to the output voltage. When output voltage is low, the system reduces both the overcurrent limit threshold and maximum switching frequency, thereby matching component stress levels to actual operational requirements and reducing unnecessary power consumption while maintaining adequate protection.
2Reliability
If components are selected based on maximum output current, then the power supply can meet peak demands, but component size and cost increase for low voltage operation
Solution Approach 1:
The system dynamically adjusts the overcurrent limit threshold based on output voltage, allowing smaller components to be used for low voltage operation while maintaining the capability to handle peak power demands when voltage is high. This dynamic adaptation eliminates the need to oversized components for maximum current, reducing device complexity and cost for low voltage applications.
3Speed
If the maximum switching frequency is kept constant, then the power supply can respond quickly to load changes, but power consumption and electromagnetic interference increase at low output voltages
Solution Approach 1:
The patent applies dynamics by making the maximum switching frequency variable based on output voltage. At low output voltages, the system reduces the maximum switching frequency, thereby decreasing switching losses and electromagnetic interference. At high output voltages, the system allows higher switching frequencies to maintain fast response to load changes, thus resolving the contradiction between response speed and power consumption.
Solution Approach 2:
The system changes the switching frequency parameter according to output voltage conditions. By reducing the maximum switching frequency at low voltages, the patent directly addresses the increase in switching losses and EMI, while maintaining adequate response speed for the given voltage level.
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 enables more efficient operation by matching component selection with the actual output current requirements, reducing waste and improving power management across varying output voltage conditions.
Implementation Method 1
generates, by performing switching of a switching element connected to a DC voltage via a primary winding of a transformer, an output DC voltage on a secondary winding side of the transformer
Data Source
AI summary
An overcurrent protection control circuit detects a low set value of an output voltage from a drop in voltage at a VCC terminal below a reference voltage. The overcurrent protection control circuit switches an overcurrent limit value from a high reference voltage to a low reference voltage and switches a maximum limit value of a switching frequency from a high first maximum switching frequency to a low second maximum switching frequency. By doing so, an overcurrent limit value of a switching element and a maximum limit value of a switching frequency are set to low values and a rise in output current is suppressed.