![]() However, each PT topology has an optimal vibration mode that allows optimal energy transfer. PTs can operate in many possible vibrational modes, each with a different frequency. Radial mode transformers have been offered at power levels of more than 100 W and are expected to exceed 200 W through further development 6. This helps radial mode PTs to achieve high power density. The coupling factor that most closely corresponds to the radial mode vibration is kp. Radial mode transformers are suitable for use in up and down converters and have been used in a wide range of applications from fluorescent lamp ballasts 4 to laptop power supplies 5. Various arrangements for the radial mode device have been proposed, of which the radial mode transformer is probably the best-known 3. Radial mode devices are disc or ring-shaped and operate at a frequency close to the radial resonance. Thickness vibration mode PTs were developed by NEC of Japan in the 1990s. In the Rosen-type transformer, the input part is in the longitudinal direction and the output is in the thickness direction, and this type of PT is usually used as a voltage step-up transformer 2. PTs are classified into three main types: Rosen, thickness vibration mode, and radial vibration mode. After that, a lot of research was done on different PTs, including geometry, modeling, and efficiency improvement. The desirable ratio of input and output voltages can be obtained with proper design. The input piezoelectric disc is excited at the resonance frequency, and the output voltage is obtained from the output element. These transformers usually consist of two piezoelectric elements as input and output ports. ![]() ![]() PTs transmit the voltage via mechanical vibration and increase or decrease it. Piezoelectric elements have been used to make voltage transformers (PT) since a few decades ago. For the chosen piezoelectric disc, the lowest gain increases the frequency from 61.9 to 118 kHz, and the highest gain increases the frequency from 3.7 to 51 kHz. Simulation and experiments show that the mechanism works as predicted, and their results are in good agreement. Therefore, the proper size of piezoelectric discs should be used to get the necessary gain. However, the input and output frequencies are limited to the piezoelectric element’s out-of-plane and radial modes. By applying different input frequencies, different output frequencies can be obtained. When the input disc is forced to vibrate in the out-of-plane mode, the output disc vibrates in its radial mode. There is a common electrode between these two elements and two electrodes input and output on the other sides. PFC uses two piezoelectric discs as input and output elements which are pushed together. This article introduces a new piezoelectric frequency converter (PFC), using an idea similar to piezoelectric transformers (PT). “Electric circuits” or “coupled motors and generators” are usually used for frequency conversion. You might also be successful with other n-channel JFET transistor types, but not all off them work with the current and bias from your microphone input supply.Converting the frequency is needed in many fields of advanced technology. a resistor in the range of 20kOhm to 100kOhm.10-25mm piezo disc (bigger ones are more sensitive).You can solder an audio cable to the disc and a 3.5mm audio jack (mono or stereo) on the other end.Ī typical (headset-) microphone input circuit has a resistor and a capacitor included that complete the circuit to be a proper (and simple) JFET amplifier (Fig.3). The transistor should be as close as possible to the disc to effectively protect your signal against environmental noise. Our simple and effective circuit consists just of a JFET transistor and a resistor (Fig.2). ![]() To enhance the signal quality a pre-amplifier that boosts the current from the piezo disc is needed and thus gives you more bass response. Also, the low current and capacitance of the disc forms a natural high pass filter with your microphone input amplifier. Piezo discs have a very low-current output signal and are thus very susceptible to noise from the environment (e.g.
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