Capacitive Discharge Push-Pull Converter for EMAT Pulsing
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Solution Overview
Problem
Existing EMAT coil pulsing technologies face limitations in size, complexity, and efficiency, particularly in reducing undesired ringing and achieving high-voltage, high-current full cycles, which restricts the strength and range of ultrasonic signals.
Innovation Solution
A capacitive discharge push-pull converter circuit is used to pulse differential EMAT coils, employing two capacitors and low-voltage drivers to manage current flow through MOSFETs, allowing for full-cycle operation without costly high-power switching devices and complex control circuits, effectively eliminating ringing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If standard capacitive discharge topology is used, then device size and complexity are reduced, but the ability to produce full-cycle high-voltage and high-current is limited
Solution Approach 1:
The circuit is divided into two separate half-bridge circuits, each handling one half-cycle of the AC output. This segmentation allows each capacitor to be charged independently by the DC voltage source and discharged through the EMAT coil in alternating half-cycles, enabling full-cycle operation without requiring a complex center-tapped transformer or full H-bridge configuration.
Solution Approach 2:
Two half-bridge circuits are merged to form a complete push-pull converter that delivers full-cycle AC power to the EMAT coil. The combining of two simpler half-bridge circuits achieves the functionality of more complex topologies while maintaining reduced component count and circuit simplicity.
2Power
If H-Bridge or Push-Pull topology with transformer is used, then high-voltage and high-current full cycles are achieved, but device size, weight, and complexity increase
Solution Approach 1:
The transformer component is extracted and removed from the circuit. Instead of using a transformer to step up voltage and provide isolation, the invention directly uses capacitors charged to the required DC voltage level, eliminating the transformer and its associated complexity, weight, and size.
Solution Approach 2:
The magnetic coupling mechanism of a transformer is replaced with direct electrical coupling through capacitors and switching devices. The voltage transformation and power delivery function previously achieved through electromagnetic induction in a transformer is now accomplished through direct capacitor discharge circuits.
3Power
If H-Bridge or Push-Pull topology with transformer is used, then high-voltage and high-current full cycles are achieved, but device weight and size increase
Solution Approach 1:
The heavy transformer component is extracted and removed from the system. The replacement capacitor-based half-bridge circuits use solid-state components with significantly lower weight while delivering the same high-voltage and high-current power output to the EMAT coil.
4Volume of moving object
If standard capacitive discharge topology is used, then device size is reduced, but the ability to produce full-cycle high-voltage and high-current is limited
Solution Approach 1:
The power delivery function is segmented into two independent half-bridge circuits that operate in alternating half-cycles. This allows the use of smaller individual capacitors and switching devices compared to a single full-bridge configuration, reducing overall device volume while achieving full-cycle power delivery.
Solution Approach 2:
Two compact half-bridge circuits are merged to achieve full-cycle AC power output. The combined circuit delivers high-voltage and high-current full cycles to the EMAT coil while maintaining a compact form factor smaller than traditional transformer-based solutions.
5Ease of operation
If any standard topology is used, then basic pulsing function is achieved, but undesired ringing is not reduced
Solution Approach 1:
The natural ringing characteristic of the EMAT coil, which is typically harmful and creates blind zones, is converted into a beneficial effect. By carefully controlling the capacitor discharge timing and duration to match the coil's resonant frequency, the ringing is sustained and amplified rather than suppressed, enhancing the ultrasonic signal strength and eliminating blind zones in the inspection.
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 enables a compact, efficient EMAT pulser that produces high-voltage, high-current full cycles, reducing ringing and enhancing ultrasonic signal quality, with superior performance at frequencies over 10 MHz, outperforming traditional topologies.
Implementation Method 1
a first transistor discharges the first capacitor so that a current passes through a first half of the differential electrical coil
Implementation Method 2
a second transistor discharges the second capacitor so that a current passes through a second half of the differential electrical coil
Implementation Method 3
This ac voltage is then converted to an ultrasonic wave by the interaction of the EMAT coil with a magnetic field
Data Source
AI summary
A high-voltage pulser circuit for Electromagnetic Acoustic Transducer (EMAT) coils using a Capacitive Discharge push-pull converter. The present invention relates in particular to the operation of the converter into an Electromagnetic Acoustic Transducer (EMAT) differential coil. The present invention reduces ringing of the coil current resulting in a smaller blind zone and a well-defined broadband ultrasonic wave from the coil. The pulser can be used to generate one or more cycles and work in either pulse-echo (same transmitter and receiver) or pitch-catch (different transmitter and receiver).