Switching Power Supply Overload Protection Circuit
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Solution Overview
Problem
Existing switching power supply devices interrupt switching operations due to instantaneous drops in input voltage, leading to adverse effects on loads and delayed recovery, as they fail to distinguish between overload states and temporary voltage drops, resulting in inappropriate overload protection and increased costs.
Innovation Solution
Incorporating an input low-voltage detection circuit that generates a detection signal when the input voltage falls below a predetermined value, allowing the overload protection signal to be activated only when an overload state is detected, and deactivating it when the input voltage returns to normal, with a timer circuit to manage the overload protection duration and a latch circuit to handle self-reset and latch-type functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the overload protection circuit interrupts switching operation when input voltage drops below a predetermined value, then the device is protected from damage, but the switching operation is interrupted even during temporary voltage drops in light load states, causing adverse effects on the load
Solution Approach 1:
The overload protection circuit dynamically adjusts its protection threshold based on load conditions. In light load states, the circuit allows temporary voltage drops without interrupting switching operation, while in heavy load states, it maintains strict protection. This is achieved by making the protection threshold variable rather than fixed, allowing the circuit to adapt its behavior to current operating conditions and avoid unnecessary interruptions during transient voltage drops.
Solution Approach 2:
The invention changes the parameter of the protection threshold from a fixed predetermined value to a variable value that depends on load conditions. By monitoring load state and adjusting the voltage threshold accordingly, the circuit can distinguish between dangerous overload conditions requiring protection and temporary voltage drops that should not trigger interruption. This parameter change enables selective protection that avoids adverse effects on loads during transient events.
2Reliability
If the switching operation is interrupted during instantaneous voltage drops, then the device prevents damage, but the recovery time is extended and operational efficiency is reduced
Solution Approach 1:
The protection circuit implements dynamic threshold adjustment based on load conditions, allowing temporary voltage drops during light load states without triggering protection interruption. This dynamic behavior enables the circuit to distinguish between transient voltage drops that should be tolerated and genuine overload conditions requiring protection, thereby reducing unnecessary recovery time while maintaining device protection when truly needed.
Solution Approach 2:
The circuit performs preliminary assessment of the voltage drop condition by monitoring load state before triggering protection interruption. By evaluating whether the voltage drop occurs during light or heavy load conditions, the circuit can preemptively avoid unnecessary protection activation during temporary drops, preventing the harmful effect of extended recovery time while still protecting against genuine overloads.
3Device complexity
If the overload protection circuit operates without considering load state, then the protection mechanism is simple, but it cannot distinguish between overload states and temporary voltage drops, leading to inappropriate protection activation
Solution Approach 1:
The protection circuit incorporates dynamic load state monitoring to adjust its protection threshold in real-time. By continuously detecting load conditions and making the protection threshold variable, the circuit achieves accurate distinction between overload states and temporary voltage drops. This dynamic approach maintains reasonable complexity while significantly improving detection accuracy compared to fixed-threshold circuits.
Solution Approach 2:
The invention changes the protection threshold parameter from a fixed value to a variable value that depends on detected load state. This parameter transformation enables the circuit to adapt its sensitivity based on operating conditions, achieving high measurement precision in distinguishing between different voltage drop causes without requiring overly complex circuit architecture. The variable threshold approach balances complexity and accuracy effectively.
Data Source
AI summary
In a switching power supply device including an overload protection circuit, when a load state turns into an overload state due to a decrease in an input voltage, an overload protection signal is activated in response to activation of an overload detection signal, and the overload protection signal is deactivated when an input low voltage detection signal is in an inactive state.