Zero-Cross Comparator Feedback to Minimize Phase Delay
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Solution Overview
Problem
Conventional zero-cross circuits in electrical systems suffer from phase lag or delay due to hysteresis, which can cause issues in parallel AC systems, such as those in aircraft, where frequency sensing needs to be in phase.
Innovation Solution
A zero-cross circuit with a feedback loop that includes a capacitor in series with a resistor, acting as a 'speed-up' capacitor, is used to reduce phase delay by applying positive feedback to the signal, thereby minimizing hysteresis-induced lag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional zero-cross circuits are used, then the circuit can detect waveform transitions, but phase lag occurs due to hysteresis
Solution Approach 1:
The patent applies feedback by connecting the output of the comparator back to its non-inverting input through a feedback network consisting of a resistor and capacitor. This feedback mechanism allows the circuit to anticipate the zero-crossing point by sensing the output state and adjusting the comparison threshold dynamically, thereby reducing the phase delay caused by conventional hysteresis while maintaining stable operation.
Solution Approach 2:
The patent changes the operational parameters of the comparator by introducing a speed-up capacitor that modifies the effective threshold voltage dynamically. The capacitor charges and discharges based on the output state, temporarily shifting the comparison level to predict upcoming zero-crossings. This parameter change enables the circuit to compensate for its own response time and reduce phase lag.
2Stability of the object's composition
If hysteresis is applied to stabilize the comparator output, then switching stability improves, but phase delay increases
Solution Approach 1:
The patent implements preliminary action by using the feedback capacitor to anticipate the zero-crossing event before it actually occurs. The capacitor charges in advance during the positive half-cycle and discharges to trigger the output transition just before the actual zero-crossing point. This preliminary action allows the circuit to maintain stability through controlled hysteresis while compensating for the delay by acting in advance of the actual crossing event.
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
This solution achieves nearly zero-phase delay, reducing errors and heat generation, enhancing the reliability and efficiency of AC system synchronization and power transfer operations.
Implementation Method 1
a feedback loop that includes a capacitor in series with a resistor, wherein the capacitor reduces a phase delay for the circuit
Implementation Method 2
a comparator having an inverting input operable to receive a reference signal; a non-inverting input operable to receive an alternating current (AC) signal
Data Source
AI summary
Provided are embodiments for a system including a zero-cross circuit. The system includes a first channel and a second channel Each channel includes a generator, a generator relay, and a bus tie relay. In addition, the system includes a zero-cross circuit, wherein the zero-cross circuit synchronizes the operation of the first and second channel, and at least one controller configured to control the operation of the first channel and the second channel based on an input from the zero-cross circuit. Also provided is a method for operating the zero-cross circuit with low phase delay. The method includes receiving an inverting input, receiving a non-inverting input, and comparing the inverting input and the non-inverting input. The method also includes receiving feedback from an output of the comparator; and outputting a waveform based on the comparison of the inverting input and the non-inverting input and the feedback.