Time Sequence Protection Circuit for Soft Start and Fast Shutoff
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Solution Overview
Problem
Conventional control circuits for electronic devices fail to provide effective protection against damage from inrush currents and abnormal conditions due to slow turning-off of power converters, which can lead to PSU damage.
Innovation Solution
A time sequence protection circuit comprising resistors, diodes, and capacitors that control the turning-on and turning-off of electronic devices based on a time sequence signal, ensuring stable and secure operations by adjusting delay times and resisting interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a control circuit for slow turning-on of the power converter is provided to avoid incorrect early turning-on, then the power converter is protected from damage at start-up, but the turning-off operation becomes slow and cannot provide effective protection in abnormal conditions
Solution Approach 1:
The circuit dynamically adjusts the RC time constant based on the state of the enable signal. When the enable signal transitions from high to low, the discharge path through the third diode provides a low-impedance path that dramatically reduces the effective time constant, enabling fast turning-off. When the enable signal is low to high, the normal RC charging path provides controlled delay for soft turning-on. This dynamic adjustment of circuit parameters resolves the contradiction between slow turning-on protection and fast turning-off capability.
Solution Approach 2:
The circuit segments the charging and discharging paths of the RC network into separate controllable paths. The first diode controls the charging path through the first resistor, while the third diode provides a separate fast discharge path. This segmentation allows independent optimization of the turning-on delay (through R1-C1 time constant) and turning-off speed (through the low-impedance discharge path), resolving the contradiction between these two opposing requirements.
2Device complexity
If a fixed RC time constant is used for turning-on delay, then simple circuit design is achieved, but the circuit cannot adapt to different operating conditions and provides limited protection flexibility
Solution Approach 1:
The circuit transforms a static RC time constant into a dynamic, state-dependent time constant. The effective time constant is determined by the circuit state (enable signal level) and can switch between two distinct values: a longer time constant for normal turning-on delay, and a much shorter effective time constant for fast turning-off. This dynamic behavior provides adaptability to different operating conditions while maintaining relatively simple circuit implementation using only diodes and resistors.
Solution Approach 2:
The circuit changes the electrical parameters (resistance and capacitance values) based on the operating state. Through the action of the diodes, the resistance in the RC path changes from R1 during charging to a much lower value during discharging. This parameter change allows the same physical components to provide different time constants for different operational phases, achieving adaptability without requiring multiple separate circuits.
3Ease of operation
If conventional control circuits are used, then basic turning-on control is achieved, but the circuits fail to provide effective protection against damage from inrush currents and abnormal conditions
Solution Approach 1:
The circuit implements preliminary anti-action by providing a pre-configured fast discharge path that is activated when abnormal conditions are detected (enable signal transition to low). The third diode and associated resistors create a discharge path that will immediately counteract any harmful inrush current or abnormal condition by rapidly pulling the RC node to ground potential. This preliminary preparation of the protection path ensures that when needed, the circuit can immediately counteract harmful effects without requiring complex detection or 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
Enables flexible setting of turning-on delay times, fast turning-off, and resistance to signal interference, thereby protecting electronic devices from damage and ensuring reliable operation.
Implementation Method 1
charging the capacitor by a first current path from the positive input pin through the first resistor and the first diode to the capacitor
Implementation Method 2
a first diode having an anode terminal coupled to the first resistor at a first node and a cathode terminal coupled to a second node
Data Source
AI summary
According to embodiments of the present disclosure. there is provided a time sequence protection circuit. The time sequence protection circuit comprises a first resistor coupled to a positive input pin; a first diode having an anode terminal coupled to the first resistor at a first node and a cathode terminal coupled to a second node: a capacitor coupled between the second node and a negative input pin; a second diode having an anode terminal coupled to the first node and a cathode terminal coupled to an output pin; a third diode having an anode terminal coupled to the output pin and a cathode terminal coupled to the positive input pin; and at least one of: a fourth diode having an anode terminal coupled to the second node and a cathode terminal coupled to the positive input pin, and a second resistor coupled between the second node and the negative input pin. Such arrangement enables slow turning-on and fast turning-off of the controlled circuit and can also resist interference.