Switching Power Supply Overcurrent Detection via Current Gradient
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Solution Overview
Problem
Conventional switching power supply apparatuses face challenges in preventing output current from depending on input voltage during overcurrent conditions, leading to increased stress on components and requiring additional external parts and power consumption for input voltage measurement.
Innovation Solution
A switching power supply apparatus that measures the gradient of the electric current flowing through the switching device to correct the overcurrent detection point, eliminating the need for direct input voltage measurement and reducing the number of external parts and power loss by integrating circuit elements within the control circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If input voltage measurement circuit is added to correct overcurrent detection point, then overcurrent protection accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent applies self-service by using the existing current measurement circuit to simultaneously perform both current measurement and input voltage measurement functions. The control circuit processes the current measurement signal to extract both current magnitude and its gradient information, eliminating the need for separate input voltage measurement circuits while maintaining correction accuracy.
Solution Approach 2:
The patent makes the current measurement circuit multi-functional by using it to detect both the current magnitude and the input voltage level (through current gradient). This single circuit performs multiple functions: current sensing, voltage sensing, and providing correction signals, thereby reducing overall device complexity while improving overcurrent protection accuracy.
2Measurement precision
If input voltage measurement circuit is added to correct overcurrent detection point, then overcurrent protection accuracy is improved, but power consumption increases
Solution Approach 1:
The existing current measurement circuit serves dual purposes by also measuring input voltage through current gradient detection. This eliminates the need for additional power-hungry voltage measurement circuits, maintaining correction accuracy while minimizing power consumption.
Solution Approach 2:
The patent merges the current measurement and voltage measurement functions into a single circuit operation. The current measurement signal is processed to provide both current magnitude information and input voltage information, combining multiple measurement functions into one operational path to reduce overall power consumption.
3Measurement precision
If external parts are increased for input voltage measurement, then overcurrent protection accuracy is improved, but ease of manufacture deteriorates
Solution Approach 1:
The current measurement circuit performs self-service by simultaneously measuring both current and input voltage, eliminating the need for additional external voltage measurement parts. This maintains correction accuracy while simplifying manufacturing by reducing component count.
Solution Approach 2:
The patent extracts the voltage measurement capability from a separate external circuit and integrates it into the existing current measurement circuit through gradient detection. This removes the need for additional external voltage sensing components while maintaining the correction function.
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 allows for effective overcurrent protection independent of input voltage, reducing component stress and external parts, while minimizing power loss and terminal requirements.
Implementation Method 1
a current measurement signal corresponding to a voltage drop of the current measurement resistor is input into a comparator
Implementation Method 2
a primary winding W1 of a transformer T1, a switching device Q1, and an (electric) current measurement (or detection) resistor R are serially connected
Implementation Method 3
Switching of the switching device Q1 is controlled by a control circuit CNT
Implementation Method 4
the magnetic energy stored in the transformer T1 is discharged from a secondary winding W2 thereof, via a rectifying diode D21 and a smoothing capacitor C21 to a load 22 on the output side
Implementation Method 5
a smoothing capacitor C21 connected to the secondary winding of the transformer
Data Source
AI summary
A switching power supply apparatus has a switching device control circuit for performing overcurrent protection by controlling switching-on/off of a switching device, connected serially to a primary winding of a transformer, so as to make a voltage output from a rectifying and smoothing circuit, connected to a secondary winding of the transformer, have a specific value, and switching off the switching device when the electric current flowing through the switching device exceeds a value as an overcurrent detection point. This control circuit includes: a current variation measurement circuit for measuring a gradient of the electric current flowing through the switching device, based on a current measurement signal output from a circuit for measuring this electric current; and an overcurrent detection-point correction circuit for correcting the overcurrent detection point with respect to the electric current flowing through the switching device, based on a signal output from the current variation measurement circuit.