Load Switch Integration Circuit for Reverse Stress Detection
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Solution Overview
Problem
Existing load switches with fixed reverse current blocking functions face challenges in setting optimal voltage and delay offsets, leading to potential power device breakdown or false alarms due to constant reverse voltage and transient events.
Innovation Solution
A load switch with a voltage-current conversion circuit and capacitor to integrate the voltage difference between output and input voltages, allowing for dynamic trigger decisions based on average voltage differences and adjustable delay offsets, while using hysteresis to prevent oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed intentional positive offset is applied to comparator input terminals to meet inductive load requirements, then the output voltage can slightly exceed the input voltage, but the power device may be left unprotected if the offset is too high or false alarms may be triggered if the offset is too low
Solution Approach 1:
The patent applies dynamics by making the voltage offset dynamic rather than fixed. The offset is generated by integrating the voltage difference between output and input voltages over time, allowing the offset to automatically adjust based on the actual voltage difference and transient duration. This resolves the contradiction by enabling the system to provide appropriate protection during real reverse current events while avoiding false alarms during normal transient operations.
Solution Approach 2:
The patent changes the parameter of voltage offset from a fixed value to a time-varying parameter that evolves based on the integration of voltage differences. This parameter change allows the system to adapt the offset level according to the duration and magnitude of voltage transients, thereby achieving reliable reverse current blocking without false alarms or insufficient protection.
2Reliability
If a fixed delay is included in the comparator to handle short transient events, then immediate triggering is delayed to avoid false alarms, but the reverse current blocking function is delayed too long causing danger if the delay is too big, or false alarms are triggered if the delay is too small
Solution Approach 1:
The patent replaces the fixed delay with a dynamic delay mechanism based on capacitive integration. The integration time constant (determined by the RC circuit) provides a natural delay that is proportional to the voltage difference magnitude and duration. This dynamic delay allows the system to respond quickly to genuine reverse current events while naturally filtering out short transient events, resolving the time loss contradiction.
Solution Approach 2:
The patent implements feedback through the integration process where the output voltage difference is continuously fed back to the comparator input through the integrating capacitor. This feedback mechanism creates a delayed response that is automatically adjusted based on the magnitude and duration of the voltage difference, providing optimal trigger timing without fixed delay limitations.
3Stability of the object's composition
If hysteresis is implemented at the comparator input terminals to avoid oscillation, then oscillation is prevented, but the intentional positive offset is increased reducing protection sensitivity
Solution Approach 1:
The patent introduces an integrating capacitor as an intermediary between the voltage difference signal and the comparator input. This intermediary component performs the hysteresis function through its charging/discharging characteristics, preventing comparator oscillation while maintaining sensitivity. The capacitor acts as a buffer that smooths rapid voltage changes without significantly increasing the effective offset, thus resolving the contradiction between stability and sensitivity.
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 enables the load switch to respond quickly to reverse stress, reducing power device damage and false positives by integrating current differences and adjusting trigger delays, thus optimizing reverse current blocking without relying on fixed offsets.
Implementation Method 1
a first terminal of the capacitor is connected to the current difference output terminal, for integrating the current difference to obtain an average voltage difference characterizing the voltage difference between the output voltage and the input voltage during an integration period for the capacitor
Implementation Method 2
To avoid oscillation, hysteresis is implemented at the input terminals of the comparator
Data Source
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AI summary
This invention provides a load switch and a power system. The load switch includes a power input terminal, a power output terminal, a voltage-current conversion circuit, a capacitor and a comparator. The power input terminal is configured to receive an input voltage. The power output terminal is configured to provide an output voltage. The voltage-current conversion circuit comprises a first input terminal, a second input terminal and a current difference output terminal. The first input terminal and the second input terminal are connected to the power output terminal and the power input terminal, respectively, and configured to receive the output voltage and the input voltage, respectively. A current difference characterizing a voltage difference between the output voltage and the input voltage is output at the current difference output terminal. A first terminal of the capacitor is further connected to the current difference output terminal, for integrating the current difference to obtain an average voltage difference characterizing the voltage difference between the output voltage and the input voltage during an integration period for the capacitor, and a second terminal of the capacitor is connected to a ground line. The first terminal of the capacitor is further connected to a first input terminal of the comparator to determine whether to send a signal for preventing current from flowing from the power output terminal to the power input terminal according to a value at the output terminal of the comparator.