Effects of a parallel resistor on electrical characteristics of a piezoelectric transformer in open-circuit transient state

Abstract

This paper investigates electrical transient characteristics of a Rosen-type piezoelectric transformer (PT), including maximum voltages, time constants, energy losses and average powers, and their improvements immediately after turning OFF. A parallel resistor connected to both input terminals of the PT is needed to improve the transient characteristics. An equivalent circuit for the PT is first given. Then, an open-circuit voltage, involving a direct current (DC) component and an alternating current (AC) component, and its related energy losses are derived from the equivalent circuit with initial conditions. Moreover, an AC power control system, including a DC-to-AC resonant inverter, a control switch and electronic instruments, is constructed to determine the electrical characteristics of the OFF transient state. Furthermore, the effects of the parallel resistor on the transient characteristics at different parallel resistances are measured. The advantages of adding the parallel resistor also are discussed. From the measured results, the DC time constant is greatly decreased from 9 to 0.04 ms by a 10 kΩ parallel resistance under open output.

A Novel Transfer Function Based Ring-Down Suppression System for PMUTs

“…At present, many efforts have been made to reduce the ring-down time or blind area of ultrasonic transducers, such as full-bridge acoustic emission [ 4 ], parallel resistors [ 12 , 13 ], Golay complementary pairs [ 14 ], amplitude detection [ 15 ], etc. The above methods are usually verified using bulk piezoelectric transducers, not PMUTs with much smaller bandwidth and higher Q .…”

“…When the excitation signal is removed, the full-bridge acoustic emission technique quickly consumes the residual energy. Chang et al [ 12 , 13 ] suggested a parallel resistor to reduce DC time constant and DC response time of the transient response, induced immediately after an AC voltage connected to a bolt-clamped Langevin transducer (BLT). The above methods [ 4 , 12 , 13 ] are effective by increasing the complexity of the peripheral circuit.…”

“…Chang et al [ 12 , 13 ] suggested a parallel resistor to reduce DC time constant and DC response time of the transient response, induced immediately after an AC voltage connected to a bolt-clamped Langevin transducer (BLT). The above methods [ 4 , 12 , 13 ] are effective by increasing the complexity of the peripheral circuit. Hernández et al [ 14 ] presented an encoding technique based on Golay complementary pairs, where the dimension of the blind zone is reduced to negligible distances using specially designed features from the binary sequences.…”

“…It is worth noting that the existing suppression systems are sitive to system parameters. At present, many efforts have been made to reduce the ring-down time or blind area of ultrasonic transducers, such as full-bridge acoustic emission [4], parallel resistors [12,13], Golay complementary pairs [14], amplitude detection [15], etc. The above methods are usually verified using bulk piezoelectric transducers, not PMUTs with much smaller bandwidth and higher Q. Yao et al [4] proposed a full bridge acoustic emission technique based on bootstrap gate driver (BGD) and metal-oxide-semiconductor field-effect transistor (MOS-FET).…”

Second order bandstop and bandpass filters using transformers

“…Hence for high power density AC/AC or DC/DC converters, the piezoelectric transformer has become a viable alternative to the magnetic transformer because of higher operating voltages albeit performing a built in bandpass filtering function. Unfortunately, its optimum operating frequency is often hampered by a strong dependence on temperature and voltages applied [20,21].…”