Cross-Coupled Level Shift Circuit for Fast Common-Mode Noise Rejection
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Solution Overview
Problem
High-voltage half-bridge driver chips in LiDAR systems generate common-mode noise due to large dV/dt, leading to signal interference, signal locking, and abnormal load charging/discharging, which existing filtering methods with capacitors and resistors introduce delays and reduce signal transmission speed.
Innovation Solution
A level shift circuit with a cross-coupling module and conversion module using current mirrors with a positive feedback structure, where the first current is N times the second current, effectively filtering common-mode noise without large capacitors or resistors, ensuring stable output signals and fast signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a filtering module with capacitors and resistors is added to the high-voltage level shifting circuit, then common-mode noise can be filtered out, but signal transmission speed is reduced due to introduced delays
Solution Approach 1:
The patent extracts the harmful common-mode noise from the signal by using a differential structure that separates the noise component from the useful signal. The differential level shift circuit compares two signals and extracts only the differential component, effectively removing common-mode noise without requiring traditional RC filtering that would slow down the signal.
Solution Approach 2:
The patent replaces the mechanical/electrical filtering system (capacitors and resistors) with a differential circuit structure. Instead of using passive components to filter noise, the invention uses active differential signaling and cancellation to achieve noise rejection, thereby maintaining high signal transmission speed while eliminating common-mode noise.
2Object-affected harmful factors
If resistance or capacitance is increased to filter out greater common-mode noise, then noise filtering capability is improved, but transmission delay increases and signal speed decreases
Solution Approach 1:
The patent employs a differential feedback structure where the circuit continuously monitors and compares signals, using the feedback mechanism to cancel out common-mode noise. This active feedback approach provides superior noise filtering without the need for large RC values that would introduce delays.
Solution Approach 2:
The patent uses asymmetric current mirror structures and differential signaling where the two signal paths are designed to be mirror images of each other. This symmetry in design creates asymmetry in noise rejection, allowing the circuit to cancel common-mode noise while maintaining fast signal transmission.
3Object-affected harmful factors
If traditional filtering modules are used in the high-voltage level shift circuit, then common-mode noise is reduced, but the circuit structure becomes more complex
Solution Approach 1:
The patent merges the noise filtering function with the level shifting function into a single differential circuit structure. Instead of adding a separate filtering module to the level shift circuit, the invention integrates both functions, where the differential structure simultaneously performs level shifting and common-mode noise rejection, thereby reducing overall circuit complexity.
Solution Approach 2:
The differential level shift circuit structure serves multiple functions: it performs voltage level shifting, rejects common-mode noise, and provides signal amplification. This multi-functional design eliminates the need for separate filtering components, simplifying the overall circuit structure while achieving superior noise performance.
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 proposed solution achieves high common-mode transient noise suppression with low transmission delay, reducing static power consumption and simplifying the circuit structure while maintaining signal reliability and speed.
Implementation Method 1
the cross-coupling module includes a first current mirror and a second current mirror
Data Source
AI summary
The embodiment of the present application discloses a level shift circuit and a high-voltage half-bridge driver chip. The level shift circuit includes a first and a second high-voltage switch tube, a cross-coupling module and a conversion module; a controlled end of the first high-voltage switch tube; a controlled end of the second high-voltage switch tube; the cross-coupling module includes a first current mirror and a second current mirror; the first and second nodes of the conversion module are respectively connected to the first and second current mirrors through the first and second nodes, to output an output signal.