Current Detection Circuit for Power Conversion Accuracy
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Solution Overview
Problem
Current detection circuits in power conversion devices face inaccuracies when dealing with switching currents that have components in opposite directions, leading to insufficient detection accuracy due to impedance issues and differences in gate capacity between switches.
Innovation Solution
A current detection circuit that switches the connection state of reset elements on the secondary side of a current transformer to decrease impedance, compensating for detection accuracy by adjusting the resistance state based on the direction of the switching current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current detection diode is connected in series with a current detection resistor on the secondary side of a current transformer, then the current detection circuit can detect switching current, but when the current flows in the opposite direction, negative voltage is applied to the control IC and detection accuracy becomes insufficient
Solution Approach 1:
The patent applies dynamics by making the reset impedance adjustable based on current direction. The control unit dynamically changes the connection state of reset elements (switching between first and second reset resistors) depending on whether the switching current flows in the predetermined direction or opposite direction. This dynamic adjustment allows the circuit to adapt its impedance characteristics to the current direction, preventing negative voltage application to the control IC while maintaining accurate detection.
Solution Approach 2:
The patent changes the impedance parameter of the reset circuit based on current direction. When current flows in the opposite direction, the control unit switches to a different reset resistor configuration that provides appropriate impedance matching, thereby preventing negative voltage application and maintaining detection accuracy. This parameter change approach allows the circuit to optimize its electrical characteristics for different current flow conditions.
2Reliability
If a series circuit of a diode and a switch is used to prevent excessive excitation of the current transformer, then the current transformer is protected from excessive excitation, but a diode with specific characteristics is indispensable and simultaneous driving of switches becomes difficult due to gate capacity differences
Solution Approach 1:
The patent applies universality by using reset elements that serve multiple functions: they provide a reset path for the current transformer to prevent excessive excitation, and they enable adjustable impedance for accurate current detection in both current directions. The reset circuit configuration can be dynamically changed to adapt to different operating conditions, making the same circuit structure versatile for multiple protection and detection functions without requiring separate dedicated components for each function.
3Measurement precision
If the impedance of magnetic reset on the secondary side of the current transformer is decreased by switching the connection state of reset elements, then detection accuracy is compensated for opposite direction current, but the circuit requires switching control of reset elements
Solution Approach 1:
The patent applies feedback by using the control unit to monitor the switching current direction and automatically adjust the reset circuit impedance accordingly. The control unit receives information about the current direction and provides feedback control to the switch elements, automatically switching between different reset resistor configurations. This feedback mechanism eliminates the need for manual intervention and ensures the circuit automatically maintains optimal detection accuracy regardless of current direction.
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 effectively compensates for detection accuracy issues even when switching currents have components in opposite directions, maintaining linearity of current detection and preventing negative voltage application to control ICs, thereby stabilizing peak current mode control.
Implementation Method 1
detecting a value of a component in a predetermined direction of a switching current using a current transformer
Data Source
AI summary
A current detection circuit capable of compensating for detection accuracy of a switching current through switching of a connection state of a resistor even when the switching current has a component in a direction opposite to a predetermined direction is provided. A current detection circuit for detecting a value of a component in a predetermined direction of a switching current using a current transformer, wherein, when the switching current flowing in a primary side of the current transformer has a component in a direction opposite to the predetermined direction, a connection state of reset elements on a secondary side of the current transformer is switched such that an impedance of a magnetic reset on the secondary side of the current transformer is decreased.