High-Side Power Switch Control Circuit for RS Latch Noise Immunity
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Solution Overview
Problem
Conventional high-side power switch control circuits suffer from common mode noise at the SET and RESET nodes, which can incorrectly steer RS latches, potentially damaging power switches or integrated circuits due to equal resistor sizes and switching device magnitudes, leading to latch on/off faults.
Innovation Solution
A regulation circuit dynamically adjusts the sensitivity of the level shifting circuit by changing the equivalent resistance between high-voltage switches and the high-side voltage supply based on detected signal transitions, reducing sensitivity during state changes to mitigate noise-induced errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If equal resistor sizes and switching device magnitudes are used in the level shifting circuit, then the circuit is symmetric and easy to manufacture, but common mode noise at the SET and RESET nodes can incorrectly steer the RS latch
Solution Approach 1:
The patent applies asymmetry by making the first resistor (connected to SET node) different from the second resistor (connected to RESET node). Specifically, the first resistor has a larger resistance value than the second resistor, creating an asymmetric configuration that deliberately unbalances the common mode noise rejection between the SET and RESET paths. This asymmetric design ensures that one path is more noise-immune than the other, preventing incorrect latch steering despite the presence of common mode noise.
2Speed
If the level shifting circuit has high sensitivity to input signals, then the circuit responds quickly to state changes, but it becomes susceptible to noise-induced unwanted state changes
Solution Approach 1:
The patent applies local quality by creating different noise immunity characteristics for the SET and RESET paths through asymmetric resistor values. The path with the larger resistor value has better common mode noise rejection, while the path with the smaller resistor value remains more sensitive. This localized differentiation in quality allows the circuit to maintain overall responsiveness while protecting the more critical path from noise-induced errors.
3Reliability
If the resistors in the level shifting circuit have different sizes, then noise susceptibility is reduced, but the circuit becomes more complex to manufacture
Solution Approach 1:
The patent implements asymmetry through different resistor values to achieve noise immunity. While this does increase manufacturing complexity compared to symmetric designs, the complexity increase is minimal (only one resistor value needs to differ) and is justified by the significant improvement in reliability and prevention of latch faults.
Data Source
AI summary
A circuit for controlling a high-side power switch includes a level shifting circuit configured to receive an input signal for selectively configuring a logic command circuit to be in a set state, for providing a first output signal to the high-side power switch, and in a reset state, for providing a second output signal, different from the first output signal, to the high-side power switch. The circuit also includes a regulation circuit configured to detect an indicative signal indicative of the output signal provided to the high-side power switch and to change sensitivity of the level shifting circuit to the input signal, based on the indicative signal that is detected.