Power Supply Control Device for Inrush Current Protection
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Solution Overview
Problem
Conventional power supply control apparatuses face challenges in protecting semiconductor switching elements from inrush currents, as setting a high threshold value for overcurrent self-protection can lead to premature shutdown, while a low threshold value may not prevent electric wire overheating, resulting in smoke development.
Innovation Solution
A power supply control apparatus that uses a filter circuit to convert current into voltage, with a voltage detection unit estimating wire temperature and an overcurrent protection circuit turning off the semiconductor switching element based on filtered voltage values, preventing shutdown during inrush currents and ensuring the electric wire is protected before smoke development.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high threshold value is set for the overcurrent self-protection circuit to prevent premature shutdown during inrush currents, then the semiconductor switching element can operate during inrush currents, but the electric wire may overheat and develop smoke
Solution Approach 1:
The protection function is segmented into two independent circuits: the overcurrent self-protection circuit with a high threshold value that allows inrush currents, and the electric wire protection circuit with a low threshold value that prevents wire overheating. Each circuit operates independently with its own threshold, resolving the contradiction by separating the protection objectives.
Solution Approach 2:
The current detection circuit serves as an intermediary that provides current information to both the overcurrent self-protection circuit and the electric wire protection circuit. This intermediary component enables both protection mechanisms to function simultaneously without interfering with each other, allowing the system to handle both inrush currents and wire temperature protection.
2Object-affected harmful factors
If a low threshold value is set for the overcurrent self-protection circuit to prevent electric wire overheating, then the electric wire is protected from smoke development, but the semiconductor switching element shuts down prematurely during inrush currents
Solution Approach 1:
The protection function is segmented into two independent circuits: the overcurrent self-protection circuit with a high threshold value that allows inrush currents, and the electric wire protection circuit with a low threshold value that prevents wire overheating. Each circuit operates independently with its own threshold, resolving the contradiction by separating the protection objectives.
Solution Approach 2:
The electric wire protection circuit applies a lower threshold value that is more restrictive than the overcurrent self-protection circuit. This partial action (using a lower threshold) is sufficient for wire protection but would be excessive for allowing inrush currents, hence the need for separate circuits with different threshold levels.
3Reliability
If the threshold value of the overcurrent self-protection circuit is set above the electric-wire smoke-developing characteristic curve, then the semiconductor switching element can operate during inrush currents, but the threshold value region exceeds the curve where the cut-off threshold cannot be set
Solution Approach 1:
The protection function is segmented into two independent circuits: the overcurrent self-protection circuit with a high threshold value that allows inrush currents, and the electric wire protection circuit with a low threshold value that prevents wire overheating. Each circuit operates independently with its own threshold, resolving the contradiction by separating the protection objectives.
Solution Approach 2:
The system uses two different threshold parameters: a high threshold value for the overcurrent self-protection circuit and a low threshold value for the electric wire protection circuit. By changing the threshold parameter values according to different protection needs, the system resolves the contradiction between allowing inrush currents and preventing wire overheating.
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 prevents semiconductor switching element shutdown during inrush currents and ensures the electric wire is protected before overheating, maintaining reliable operation and preventing smoke development.
Implementation Method 1
the filter circuit converts the current that is output from the current detection unit to a voltage and filters the converted voltage
Implementation Method 2
the filter circuit converts the current that is output from the current detection unit to a voltage and filters the converted voltage
Implementation Method 3
The voltage detection unit detects the voltage value of the voltage filtered by the filter circuit
Implementation Method 4
the temperature estimation unit estimates, based on the voltage value detected by the voltage detection unit, a temperature of the electric wire
Implementation Method 5
the overcurrent protection circuit turns off the semiconductor switching element based on the voltage value of the voltage filtered by the filter circuit
Data Source
Figure 1~2
Figure 3~4
AI summary
A power supply control apparatus includes: a semiconductor switching element (6) configured to be switched with PWM control; a PWM signal output unit (1) configured to output a PWM signal pertaining to the PWM control; a current circuit (5) configured to output a current related to a current flowing through the semiconductor switching element (6); a filter circuit (11 to 13) configured to convert the current that is output from the current circuit (5) to a voltage and to filter the converted voltage; an overcurrent protection circuit (4) configured to turn off the semiconductor switching element (6) based on a voltage value of the voltage filtered by the filter circuit (11); a voltage detection unit(2) configured to detect the voltage value of the voltage filtered by the filter circuit (11 to 13) at a timing near an end of a pulse of a PWM signal; a temperature estimation unit (1) configured to estimate, based on the voltage value detected by the voltage detection unit (2), a temperature of an electric wire through which a current flows that also flows through the semiconductor switching element (6); and an electric wire protection unit (1) configured to turn off the semiconductor switching element (6) based on the temperature estimated by the temperature estimation unit (1).