Digital Switched Output Circuit with Inductor for Continuous Load Testing
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Solution Overview
Problem
Existing circuit arrangements for digital switching outputs in industrial automation require brief blanking to test semiconductor switches, which disrupts load operation and is not desirable, especially in safety-critical applications.
Innovation Solution
A circuit arrangement using an inductor and freewheeling element to sustain current flow during brief semiconductor switch interruptions, allowing for functional checks without load blanking, utilizing a control and test circuit to determine correct switch-off capability without interrupting the supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brief blanking is performed to test semiconductor switches, then the switching capability can be verified, but the load operation is disrupted
Solution Approach 1:
A test output is introduced as an intermediary element that allows indirect testing of the semiconductor switch. The test output is connected to the connection node between the semiconductor switch and the inductor, enabling voltage level measurement during switch-off events without directly interrupting the load current path. The inductor acts as a mediator that maintains current flow through the load even when the semiconductor switch is temporarily deactivated for testing purposes.
Solution Approach 2:
The circuit is segmented into separate testing and load operation paths. The testing function is isolated to the test output branch, while the load operation continues through the main circuit path containing the inductor. This segmentation allows independent operation of testing and load functions, enabling switch verification without affecting load continuity.
2Reliability
If two semiconductor switches are connected in series to increase reliability, then the shutdown reliability is improved, but the device complexity increases
Solution Approach 1:
The inductor serves multiple functions simultaneously: it limits current during normal operation, maintains current flow during semiconductor switch testing to prevent load blanking, and enables the test output to detect switch-off events. This multi-functionality reduces the need for additional dedicated components for each function, thereby managing complexity while achieving reliable testing capability.
3Measurement precision
If the semiconductor switch is briefly switched off for testing, then the switching capability can be determined, but energy losses and voltage dips occur
Solution Approach 1:
The inductor is pre-configured in the circuit to store magnetic energy during normal current flow. When the semiconductor switch is briefly switched off for testing, the inductor releases its stored energy to maintain current flow through the load, preventing energy losses and voltage dips that would otherwise occur during the test blanking event.
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
Enables the checking of semiconductor switches during operation without momentarily blanking the switching output, ensuring correct functioning and safety while maintaining load supply, with reduced energy losses and minimal voltage dips.
Implementation Method 1
an inductor (6) connected between the series connection of the two semiconductor switches (3, 4) and the switching output (2)
Implementation Method 2
a switching element (7) connected between a connection node of the series connection of the two semiconductor switches (3, 4) and the inductor (6) and the further output (2')
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a circuit arrangement for a digital switched output (2) for connecting a load that can be connected between the switched output (2) and another output (2'), said arrangement having at least one semiconductor switch (3, 4) arranged, with a clearance between contacts, between a supply voltage connection (1) and the switched output (2). The circuit arrangement is characterised in that the at least one semiconductor switch (3, 4) is connected to the switched output (2) via an inductance (6), wherein a connecting node between the at least one semiconductor switch (3, 4) and the inductance (6) is connected to the other output (2') via a free-wheeling element. The invention also relates to an output module for automated control comprising a circuit arrangement of this type and to a test method for a circuit arrangement of this type.