Photocoupler Output Circuit Dynamic Current Control
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Solution Overview
Problem
Photocouplers in intelligent power modules experience reduced lifespan and noise resistance due to decreased current conversion efficiency over time, leading to potential circuit malfunctions when attempting to increase the light emitting diode current to improve noise resistance.
Innovation Solution
An output signal receiving circuit with a pull-up resistor and complementary constant current circuits that reduce discharge current after a certain period, allowing for reduced current intake by the photocoupler without compromising noise resistance, thereby extending photocoupler lifespan and preventing malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the light emitting diode current is increased to improve noise resistance, then the noise resistance is improved, but the photocoupler lifespan is reduced due to decreased current conversion efficiency over time
Solution Approach 1:
The patent applies dynamic control by switching between two constant current circuits (first and second circuits) based on the operational state of the photocoupler. The control circuit selectively activates the first constant current circuit during initial operation and switches to the second constant current circuit after a predetermined period, thereby dynamically adjusting the current magnitude to optimize both noise resistance and lifespan throughout different operational phases.
Solution Approach 2:
The patent changes the current parameter over time by using two different constant current circuits with distinct current values. The first constant current circuit provides a higher current for improved noise resistance during initial operation, while the second constant current circuit provides a reduced current to extend photocoupler lifespan after the predetermined period elapses, thus adapting the electrical parameter to different operational stages.
2Reliability
If the light emitting diode current is increased to improve noise resistance, then the noise resistance is improved, but the circuit current consumption increases
Solution Approach 1:
The patent implements periodic action by dividing the operational timeline into two distinct periods: an initial period where the first constant current circuit operates at higher current to ensure noise resistance, and a subsequent period where the second constant current circuit operates at reduced current to minimize energy consumption. This temporal segmentation of current delivery optimizes the balance between reliability and energy efficiency.
Solution Approach 2:
The control circuit dynamically switches between two constant current circuits based on elapsed time, adjusting the current magnitude to match operational requirements. During the initial period, higher current is supplied for noise resistance; after the predetermined period, lower current is supplied to reduce power consumption, thereby dynamically optimizing the energy-reliability trade-off.
3Duration of action of stationary object
If the current conversion efficiency decreases over time, then the photocoupler lifespan is extended, but the noise resistance deteriorates leading to circuit malfunction
Solution Approach 1:
The patent takes preliminary action by providing enhanced current through the first constant current circuit during the initial operational period, before significant degradation in current conversion efficiency occurs. This preliminary high-current operation ensures adequate noise resistance is maintained during the photocoupler's most reliable phase, while subsequent reduced current operation preserves lifespan during later degradation phases.
Solution Approach 2:
The control circuit incorporates time-based feedback by monitoring the elapsed operational period and selectively switching between constant current circuits based on this temporal feedback. After a predetermined period elapses, the control circuit transitions from the first to the second constant current circuit, using the elapsed time as feedback to adjust current delivery and compensate for progressive photocoupler degradation.
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 increases photocoupler lifespan and prevents circuit malfunctions by reducing the current drawn from the photocoupler while maintaining noise resistance, even in depreciated states, and reduces overall circuit current consumption.
Implementation Method 1
a light emitting unit and a light receiving unit, wherein an output signal from the light emitting unit is transmitted to the light receiving unit in an isolated state
Implementation Method 2
a light emitting unit and a light receiving unit, wherein an output signal from the light emitting unit is transmitted to the light receiving unit in an isolated state
Data Source
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AI summary
A photocoupler output signal receiving circuit includes a first constant current circuit (switching elements MP1 and MP2 and current sources I1 and I2), connected between an input terminal 124 and the high potential side of a direct current power source, that discharges current, a second constant current circuit (a current source 13), connected between the input terminal 124 and the low potential side of the direct current power source, that takes in current, and switching elements NM1 to NM3 that operate the first and second constant current circuits in a complementary way, wherein the switching elements NM1 to NM3 are operated so that current is taken in by the second constant current circuit after a photocoupler 21 is turned on, and are operated so that current is discharged by the first constant current circuit after the photocoupler 21 is turned off, and a discharge current value in a current discharge period is reduced after a certain period elapses from the start of discharging. Because of this, an increase in photocoupler lifespan is achieved, with noise resistance secured, and without increasing light emitting diode current.