JPH0129963Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a bimorph drive circuit used as an operation source for piezoelectric relays and the like.

In recent years, with the aim of reducing power consumption and reducing heat generation,
For the purpose of reducing noise, a relay using a bimorph as the operating source of the contact has been proposed.

However, when driving a bimorph with a DC power source, in order to increase the amount of displacement and displacement force of the bimorph, it is necessary to increase the applied voltage.
When driven with a low voltage circuit of about 12V, both the amount of displacement and the displacement force cannot be large, and it is difficult to drive a bimorph with such a low voltage circuit. On the other hand, if it is a high voltage circuit, the structure will be complicated and large, which is not preferable.

This invention was made in view of the above drawbacks,
The purpose is to provide a bimorph drive circuit that can increase the amount of displacement and displacement force of the bimorph even if the input signal is a low voltage.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings, which are examples of the present invention.

In FIG. 1, 1 and 1' are input terminals to which a low DC voltage is applied. 2 is an oscillation circuit that performs constant oscillation based on an input signal. 3 is a booster circuit that boosts the oscillation signal from the oscillation circuit 2, and its output is obtained in the form of a sine wave. A rectifier circuit 4 rectifies the sine wave from the booster circuit 3 and outputs it to the output terminal 6 as a voltage higher than the input voltage. Reference numeral 5 denotes a switching discharge circuit, which is connected to the input terminal 1 and the rectifier circuit 4. 6 and 6' are output terminals connected to the bimorph.

As shown in FIGS. 2 and 3, the booster circuit 3 is constituted by a well-known piezoelectric transformer, one side of the piezoelectric substrate 31 is polarized in the thickness direction, and the other side is polarized in the longitudinal direction. Electrodes 32, 33 are attached to the latter, and electrodes 32, 34 are attached to the latter. Rectifier circuit 4
is composed of two diodes 41 and 42, the anode of the diode 41 is grounded, and the cathode is connected to the electrode 34. Another diode 42 has an anode connected to the electrode 34 and a cathode connected to the output terminal 6. In addition, the switching discharge circuit 5 is a depletion type FET5.
1 and a resistor 52, the source of the FET 51 is grounded, and the gate is connected to the input terminal 1 through a resistor 8.
The drain is connected to the cathode of the diode 42 via a resistor 52.

In the above configuration, when a low voltage DC signal is input to the input terminals 1 and 1', the oscillation circuit 2 operates and outputs an oscillation signal. This oscillation signal is boosted by a booster circuit 3 and output as a sine wave, and then passed through a rectifier circuit 4 where it is rectified into high voltage direct current.
This voltage will be applied to the bimorph 7. With this, the bimorph 7 obtains a large displacement amount and displacement force. Then, while this voltage is applied, the bimorph 7 maintains its displaced state. When the input to the input terminals 1 and 1' is cut off, the oscillation circuit 2 stops and the output of the booster circuit 3 becomes zero. At this time, the charges charged in the bimorph 7 are discharged via the switching discharge circuit 5, and the bimorph 7 is restored.

In other words, the input signals to input terminals 1 and 1' are turned on and off.
Bimorph 7 repeats displacement and return when turned off.

According to experiments by the present inventors, when the substrate 31 of the piezoelectric transformer is 30 mm long, 7 mm wide, and 2 mm thick, and the electrode 33 is 18 mm long, the input voltage is 5 V (current It was possible to obtain an output voltage of 400V at 100μA).

As is clear from the above description, the present invention includes an oscillation circuit that oscillates based on an input signal, a booster circuit that boosts the oscillation signal from this oscillation circuit, and a rectifier circuit that rectifies the output signal from this booster circuit. Since the device includes a switching discharge circuit that discharges the charge charged in the bimorph when the input signal is turned off, a high voltage output signal can be obtained in response to a low voltage input signal with a simple configuration. Therefore, the bimorph can be driven with a large displacement amount and a large displacement force using this large voltage.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the drive circuit according to the present invention.
FIG. 2 is a circuit diagram thereof, and FIG. 3 is a perspective view of the piezoelectric transformer. 1, 1'...Input terminal, 2...Oscillation circuit, 3...
...boost circuit, 4... rectifier circuit, 5... switching discharge circuit, 6, 6'... output terminal, 7... bimorph.

Claims (1)

[Scope of utility model registration request] An oscillation circuit that oscillates based on an input signal, a booster circuit that boosts the oscillation signal from the oscillation circuit, and a rectifier circuit that rectifies the output signal from the booster circuit.
A bimorph drive circuit comprising a switching discharge circuit that discharges charges charged in the bimorph when an input signal is turned off.