H-Bridge Chopped Current Measurement Using Segmented Transformers
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Solution Overview
Problem
Existing chopped current measurement devices face challenges in accurately measuring bidirectional currents and ensuring sufficient demagnetization time, which is often dependent on the duty cycle and may not be long enough to effectively demagnetize transformers.
Innovation Solution
A device with an H-bridge structure comprising two transformers, each with a primary and secondary circuit, and demagnetization circuits, utilizing switches and measurement resistors connected in a specific configuration to allow current flow during magnetization and prevent flow during demagnetization, ensuring constant demagnetization time independent of the duty cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single transformer is used in a chopped current measurement device, then the device structure is simple, but the demagnetization time becomes dependent on the duty cycle and may not be sufficient for effective demagnetization
Solution Approach 1:
The measurement device is segmented into two symmetrical branches, each containing its own transformer (T1 and T2). This segmentation allows each transformer to be independently demagnetized during the freewheeling period of its respective branch, ensuring sufficient demagnetization time regardless of the overall duty cycle of the H-bridge converter.
Solution Approach 2:
Two transformer measurement circuits are merged into a single H-bridge measurement system. The symmetrical structure combines the advantages of both transformers while sharing common control and measurement resources, achieving both sufficient demagnetization time and measurement of bidirectional currents.
2Reliability
If the demagnetization circuit is connected in parallel with the measurement circuit, then the demagnetization can occur during freewheeling periods, but the measurement accuracy is affected by demagnetization current interference
Solution Approach 1:
Switches (MOSFETs or diodes) are introduced as intermediary elements to control the connection between the demagnetization circuit and the measurement circuit. These switches act as mediators that isolate the measurement circuit from demagnetization current while allowing demagnetization to proceed in the transformer secondary winding, thus preventing measurement interference.
Solution Approach 2:
The demagnetization process is implemented periodically during the freewheeling periods when the H-bridge switches are off. This periodic action synchronizes demagnetization with the natural operating cycles of the converter, ensuring that demagnetization occurs at appropriate intervals without continuous interference with the measurement circuit.
3Measurement precision
If switches are used to control current flow in the measurement circuit, then current measurement can be enabled during magnetization and disabled during demagnetization, but the switch response time may affect measurement timing
Solution Approach 1:
The measurement circuit switches are controlled by the same gate signals that control the H-bridge power switches. This self-service approach ensures that the measurement switches turn on and off simultaneously with the power switches, eliminating timing mismatches and ensuring accurate current measurement during the appropriate phases of operation.
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 allows for accurate measurement of bidirectional chopped currents while ensuring consistent and sufficient demagnetization of transformers, improving measurement precision and reliability.
Implementation Method 1
The transformer comprises a primary circuit in which the chopped current flows, and a secondary circuit in which flows an output current proportional to the chopped current
Implementation Method 2
demagnetization takes place by for example causing the magnetizing current to flow through a demagnetization circuit so that the energy accumulated in the magnetizing inductance can thus be released
Data Source
Figure 1~2
Figure 3~8
Figure 4
AI summary
The invention relates to a device (1) for measuring a chopped current (i.e.) suitable for circulating in a circuit (3) having an H-bridge structure comprising a first branch (B1) and a second branch (B2), characterized in that it comprises: - two transformers (10B1; 10B2) respectively connected to a branch (B1, B2) of the H-bridge, the transformers (10B1; 10B2) respectively comprising a primary circuit (12) configured for the circulation of a chopped current (iMos1; iMos3), and a secondary circuit (14), - two circuits (20B1; 20B2) for demagnetizing the two transformers (10B1; 10B2), - two measurement circuits (22B1; 22B2) respectively connected to the terminals (16, 18) of the secondary circuit (14) of an associated transformer (10B1; 10B2), the measurement circuits (22B1; 22B2) comprising respectively at least one unit which includes a first switch (Ki1_HS; Ki2_HS) and a second switch (Ki1_LS;Ki2_LS) connected in reverse, the two switches (Ki1_HS; Ki1_LS; Ki2_HS, Ki2_LS) being respectively implemented by a transistor and being capable of being controlled so as: - to allow the flow of the current (imes1; imes2) induced by the chopped current (iMos1; iMos3), in the measuring circuit (22B1; 22B2) when the primary circuit (12) of an associated transformer (10B1; 10B2) is closed and - to prevent the flow of the demagnetizing current in the measuring circuit (22B1; 22B2) when the primary circuit (12) of an associated transformer (10B1; 10B2) is open; and in that the measuring circuits (22B1;22B2) respectively comprise a measuring resistance (Rmes') connected by one terminal to ground, the measuring resistance (Rmes') of the first measuring circuit (22B1) being connected by one of its terminals to the source of the first transistor (Ki1_HS) and to the source of the second transistor (Ki1_LS) of the first measuring circuit (22B1) by the other of its terminals, and the measuring resistance (Rmes') of the second measuring circuit (22B2) being connected to the source of the first transistor (Ki2_HS) by one of its terminals and to the source of the second transistor (Ki2_LS) of the second measuring circuit (22B2) by the other of its terminals.;