Switch-Tube Conducted EMI Circuit Using Inductor-RC Voltage Division
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing systems for suppressing conducted Electromagnetic Interference (EMI) in electronic devices with switch elements, such as bidirectional thyristors, require additional components like filter plates to pass EMI tests, increasing costs and complexity.
Innovation Solution
A conducted EMI suppression circuit comprising an inductor and an RC circuit connected in series with the switch element, which divides the voltage applied during EMI tests, eliminating the need for filter plates and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If an RC absorption circuit is arranged at each end of the switch element to provide a bypass for reverse recovery current, then the reverse recovery current is suppressed, but the insertion loss remains low at both low and high frequencies due to capacitive impedance and stray inductance, requiring additional filter plates
Solution Approach 1:
The patent combines the absorption circuit function with the EMI filter function into a single integrated circuit. The inductor L1 in series with the parallel combination of capacitor C1 and resistor R1 serves both to absorb reverse recovery current and to filter conducted EMI across the frequency spectrum, eliminating the need for separate filter plates
Solution Approach 2:
The suppression circuit is designed to perform multiple functions simultaneously: it provides reverse recovery current bypass, suppresses voltage spikes, and filters conducted EMI across both low and high frequencies. This multi-functional design replaces what would otherwise require multiple separate components including filter plates
2Object-generated harmful factors
If filter plates are configured at power ports to pass conducted EMI tests, then EMI suppression is achieved, but the cost of passing the conducted EMI test increases
Solution Approach 1:
The patent extracts the EMI filtering function from the separate filter plate component and integrates it into the suppression circuit connected to the switch element. By taking out the filtering function and combining it with the absorption circuit, the design eliminates the need for expensive filter plates while maintaining EMI suppression effectiveness
Solution Approach 2:
The patent uses inexpensive, readily available components (standard inductor, capacitor, and resistor values) to build the suppression circuit that replaces costly filter plates. The circuit achieves professional-grade EMI suppression using common electronic components that are cheaper and easier to source
3Ease of operation
If a bidirectional thyristor is connected to inductive load and reverse voltage is applied, then carrier accumulation effect is generated with minority carriers stored on PN junction sides, but reverse blocking ability cannot be restored and large reverse recovery current flows through the device
Solution Approach 1:
The suppression circuit is connected in parallel with the bidirectional thyristor before the reverse recovery issue occurs. When reverse voltage is applied and minority carriers begin to be drawn out, the circuit is already in place to immediately provide an alternative current path, preventing the recovery current from flowing through the thyristor and preserving its reverse blocking ability
Solution Approach 2:
The suppression circuit acts as an intermediary element between the bidirectional thyristor and the inductive load. It mediates the reverse recovery current by providing a parallel path that bypasses the thyristor, allowing the thyristor to maintain its reverse blocking capability while still managing the energy from the inductive load
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 system effectively suppresses conducted EMI, improving test pass rates and extending the service life of switch elements by reducing reverse impulse voltages and insertion losses.
Implementation Method 1
the conducted EMI suppression circuit includes both the inductor and the RC circuit, while performing the EMI test, voltage applied to the LISN is divided
Implementation Method 2
an inductor and an RC circuit connected in series with the switch element
Implementation Method 3
When a frequency of conducted EMI is low, a capacitive impedance of the RC absorption circuit is high
Implementation Method 4
an RC absorption circuit may be arranged, serving as the above-mentioned absorption circuit
Data Source
Figure 1~3
Figure 4~6
Figure 7~8
AI summary
A conductive EMI suppression system (10) for a switch tube, and a household appliance. The system (10) comprises a conductive EMI suppression circuit, an inductive load (1, 71, 81) and at least one switch tube (2, 72, 82), wherein the conductive EMI suppression circuit comprises an inductor (3, 73 , 83, 123) and an RC circuit (4, 74, 84, 124); the inductor (3, 73, 83, 123) is connected to each switch tube (2, 72, 82) in series; the inductive load (1, 71, 81) is connected to each switch tube (2, 72, 82); the inductor (3, 73, 83, 123) is connected to the RC circuit (4, 74, 84, 124) in parallel after being connected to each switch tube (2, 72, 82) in series; and the conductive EMI suppression circuit is used for suppressing conductive EMI caused when each switch tube (2, 72, 82) is turned off. By means of the conductive EMI suppression system (10) for a switch tube, and the household appliance, during a conductive EMI test, the voltage of an LISN is divided without the use of a filter board, thereby reducing the cost of passing the conductive EMI test.