Power Supply Control Apparatus Inrush Current Management
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Solution Overview
Problem
Existing power supply control apparatuses struggle to prevent abnormal wire temperature increases due to inrush currents, as they either allow excessive currents or fail to manage inrush currents effectively, leading to potential overheating and safety hazards.
Innovation Solution
A power supply control apparatus with a switch control portion that includes a resistance circuit with a first resistor and a series circuit of a second resistor and a capacitor, which adjusts the current threshold based on the voltage across the resistance circuit, allowing inrush currents initially while reducing the threshold after the inrush period to prevent overheating, and incorporates a temperature calculating portion to turn off the switch when the wire temperature exceeds a predetermined value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the current threshold is set to exceed the inrush current value to allow the load to operate, then the load can work properly, but the wire temperature may increase abnormally after inrush current has flown
Solution Approach 1:
The patent applies dynamics by making the current threshold variable rather than fixed. The control circuit dynamically adjusts the current threshold based on the voltage across the capacitor: initially allowing a higher threshold to accommodate inrush current, then reducing it to prevent overheating. This is achieved through the circuit configuration where the capacitor voltage evolves over time, automatically modulating the threshold current level without external intervention.
Solution Approach 2:
The patent changes the parameter of current threshold over time. By utilizing the time-dependent voltage across the capacitor in the threshold determination circuit, the effective current threshold transitions from a higher initial value (allowing inrush current) to a lower steady-state value (preventing overheating). This parameter change resolves the contradiction between allowing load operation and preventing wire temperature increase.
2Temperature
If the current threshold is set to the inrush current value or smaller to prevent wire overheating, then wire temperature is controlled, but the switch turns OFF immediately after turning ON and the load does not work
Solution Approach 1:
The patent applies preliminary action by preparing the threshold determination circuit in advance. The capacitor is initially uncharged, creating a high initial voltage across it that sets a high current threshold. This preliminary high threshold state allows the inrush current to pass through without triggering the protection mechanism, enabling the load to start operation smoothly before the threshold is reduced.
Solution Approach 2:
The dynamic adjustment of the current threshold based on capacitor voltage evolution allows the system to transition from a permissive initial state to a restrictive steady-state. This dynamic behavior resolves the contradiction by temporarily allowing high current for startup, then automatically reducing the threshold to prevent overheating during normal operation.
3Device complexity
If a fixed current threshold is used to control power supply, then the control is simple, but it cannot distinguish between inrush current and abnormal overcurrent
Solution Approach 1:
The patent introduces an intermediary element - the capacitor - that mediates between the current threshold determination and the protection decision. The capacitor's voltage, which evolves over time, serves as an intermediary parameter that automatically distinguishes between inrush current (when capacitor voltage is high) and abnormal overcurrent (when capacitor voltage is low). This intermediary approach maintains relatively simple circuitry while significantly improving protection reliability.
Solution Approach 2:
The circuit implements feedback through the capacitor voltage that reflects the operational state. The voltage across the capacitor provides feedback information about whether the system is in the startup phase or normal operation phase, automatically adjusting the current threshold accordingly. This feedback mechanism enables the circuit to distinguish between different current types without complex control logic.
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 apparatus effectively allows inrush currents immediately after switching on while ensuring the current threshold is sufficient to prevent wire overheating, and reliably turns off the switch when the wire temperature becomes hazardous, thereby preventing abnormal temperature increases and associated safety risks.
Implementation Method 1
a series circuit of a second resistor and a capacitor that are connected in parallel to the first resistor
Implementation Method 2
a large current temporarily flows through the wire when the control circuit turns ON the switch from the OFF state
Data Source
AI summary
A control circuit turns ON or OFF a switch that is provided at a midpoint of a wire. Thus, power supply via the wire is controlled. A current output circuit outputs a current that corresponds to a current flowing through the wire to a resistance circuit. In the resistance circuit, a series circuit of a resistor (R2) and a capacitor (C1) is connected in parallel to a resistor (R1). The control circuit) turns OFF the switch if the end-to-end voltage value of a voltage across both ends of the resistance circuit is larger than or equal to a reference voltage value.