Ultrasonic Transducer Control Circuit for Flyback Voltage Clamping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Ultrasonic transducer systems face damage from high switch-off voltages due to the flyback effect in transformer inductances, which affects the sensitivity and detection range during mode transitions, as existing solutions inadequately manage energy dissipation and voltage limiting.
Innovation Solution
A control circuit with a semiconductor switch and a protective circuit using a Zener diode, which limits the switch-off voltage to at least twice the operating voltage, coupled non-capacitively to the primary winding, effectively preventing voltage increase and optimizing energy dissipation for improved detection performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a transformer is used to step up the operating voltage for piezoelectric ultrasonic transducer excitation, then the required high AC voltage (100-200V) can be provided, but high cutoff voltage occurs on the primary side due to the flyback effect from stored inductance energy
Solution Approach 1:
The patent converts the harmful flyback voltage into a beneficial protective function by using a Zener diode to clamp the voltage at a controlled level (at least twice the operating voltage). The energy that would otherwise damage components is now utilized to quickly discharge the transformer's magnetic energy, reducing the decay process duration and improving detection sensitivity in the near field.
2Object-affected harmful factors
If diodes are used to divert and dissipate the energy from primary-side inductance, then the high cutoff voltage can be limited, but power loss in the form of heat increases
Solution Approach 1:
The patent changes the voltage parameter by setting the Zener diode's breakdown voltage to at least twice the operating voltage. This specific parameter selection allows the circuit to tolerate higher voltage spikes without damage while efficiently dissipating energy, optimizing the balance between protection and energy loss.
3Reliability
If energy stored on the primary side is not quickly dissipated when switching from transmit to receive mode, then component protection is maintained, but detection capability and sensitivity for near-field objects are reduced
Solution Approach 1:
The patent prepares the protective circuit in advance by configuring the Zener diode to activate at a specific voltage threshold. When switching from transmit to receive mode, this pre-configured protection circuit immediately clamps any flyback voltage and accelerates energy dissipation, ensuring both component protection and rapid restoration of detection sensitivity without requiring additional response time.
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 efficiently dissipates energy stored in the transformer, reducing the decay process duration and enhancing the detection of ultrasonic signals by minimizing interference from residual voltages, thus improving the system's sensitivity and detection range.
Implementation Method 1
a protective circuit electrically coupled to the switched terminal and having a Zener diode that limits a cut-off voltage at the switched terminal to a limiting voltage that corresponds to at least twice the operating voltage
Implementation Method 2
The voltage level of such a control voltage is usually provided by voltage transformation using a transformer in the output stage. During transmission, a periodic pulsed operating voltage is applied to the primary side of the transformer, which is then stepped up to the desired drive voltage
Implementation Method 3
Ultrasonic transducers are used for object detection and typically feature a piezo actuator that requires a high AC voltage of approximately 100 to 200 V for excitation
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a control circuit (2) for a piezoelectric ultrasonic transducer (4) in an ultrasonic transducer system (1), comprising: - a transformer (21) with at least one primary-side winding (22, 22', 22"); - a switching unit with a semiconductor switch (24', 24"), which is connected to the at least one primary-side winding (22, 22', 22") via a switched terminal (A', A"), - a control unit (5) configured to alternately apply or disconnect an operating voltage (UB) to the at least one primary-side winding (22, 22', 22"), - a protection circuit (25) electrically coupled to the switched terminal (A', A") and comprising a Zener diode (ZD1) which limits the magnitude of a switch-off voltage at the switched terminal (A', A") to a limiting voltage (UG) that is at least twice the operating voltage.