JPS62136122A - Self-exciting oscillator - Google Patents

Abstract

PURPOSE:To obtain a simple and inexpensive self-exciting oscillator by employing one FET, providing a start circuit between its power supply and a gate, an FET ON/OFF circuit to the feedback winding of an output transformer and a charging current branching circuit between the gate and a drain. CONSTITUTION:When a current is conducted from a DC voltage source 11 via a start resistor 31, a voltage lower by the voltage drop across the resistor than the source 11 is fed as a gate voltage VG, the FET 2 is in ON-state, and a voltage having a polarity shown in continuous lines appears in a feedback winding B and the voltage is fed to the gate via a resistor 53 and a capacitor 52 to turn on the FET 2 rapidly. Thus, the charging current is conducted in the direction of the arrow (continuous ON), the polarity of the voltage across the capacitor 52 is reversed, the gate voltage VG is lowered more than the threshold level to turn off the FET 2. When the FET 2 is turned off, the charging current is conducted through a flywheeling diode 51 in a direction of the arrow (broken lines OFF), the potential of the capacitor 52 at the cathode of the diode 51 is higher and the diode 51 is turned off. The charging voltage of the capacitor 52 is fed as the gate voltage VG to turn off the FET 2. The FET 2 repeats ON/OFF in this way.

Description

[Detailed Description of the Invention] [Summary] This is a self-excited oscillator that uses one FET (field effect transistor) and feedback transformer to simplify the configuration and reduce manufacturing costs.

[Industrial application field]

The present invention relates to a self-excited oscillator. Generally, a self-excited oscillator is a device that continuously generates vibrations at a frequency determined by its own circuit constants when supplied with a DC power source.

Of these, the present invention focuses on FETs that are often used as power sources.
This relates to a self-excited oscillator in which an impedance element is connected between the three points of the gate, source, and drain.

[Conventional technology]

A conventional oscillator using an FET is a passive type having the configuration shown in FIG. 3 and operating as shown in FIG.

That is, the gate voltage is controlled by turning on and off the bipolar transistor TR connected between the gate and source of the FET.

In FIG. 3, R1 is a starting resistance. As shown in FIG. 4, the gate voltage of the FET increases, turning on the PET. A voltage having the polarity shown in FIG. 3 is induced in the transformer T. The voltage on winding B of transformer T is fed back to the FET gate and the FET turns on quickly. At this time, C1 is
It is charged with the voltage of winding B through R3. The voltage on C1 rises, turning on TR and shorting the gate-source voltage of the FET. This turns off the FET.

A back electromotive force is generated in the transformer T, and windings B-E-C2, R2
The circuit keeps the FET off. On the other hand, C1 is charged by the circuit of winding B-CI-R3 in a direction that reverse biases TR. Further, C2 is charged in the direction in which the connection point with R1 becomes positive. Eventually, when the reverse power of T disappears (reset is completed), the voltage of C2 turns the FET on again.
turns on and the operation connects.

[Problem that the invention seeks to solve]

Conventionally, since it is a passive type, in addition to the FET, a transistor is required to provide input from the outside, and a resistor and a capacitor must be provided to determine the input frequency.

Therefore, there are problems in that the circuit configuration becomes complicated and expensive.

[Means for solving problems]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a self-excited oscillator that is simpler in structure and cheaper than the conventional one.

As shown in FIG. 1, this means consists of a single FET 2, with a starter circuit 3 connected between the voltage B1 and the gate, an FET on/off circuit 5 connected to the feedback winding B of the output transformer 6, and an FET on/off circuit 5 connected between the gate and drain. A charging current shunt circuit 4 is provided in each of the two.

[For production]

According to the present invention, when the FET 2 is turned on by the starting circuit 3, voltages with the polarities of ■ and e are generated in the feedback winding B, and the charging current flows through the circuit 4 in the direction of the solid arrow ON.
Charge the capacitor in the FET on/off circuit 5.

When the capacitor is charged, voltage v6 decreases and FET2
is turned off, a voltage with the polarity of ■e shown by the broken line appears in the feedback winding B, and a charging current flows in the direction of the arrow point F, charging the capacitor with the opposite polarity, and FET2 is turned on again with the same operation as above. .

Therefore, a simple and inexpensive self-excited oscillator can be obtained using 71 PEs.

〔Example〕

The invention will now be explained by way of example with reference to the accompanying drawings.

FIG. 2 is a diagram showing an embodiment of the present invention.

The self-excited oscillator shown in FIG. 2 includes a power source 1, an FET 2, a starting circuit 3, a charging current shunting circuit 4, an FET on/off circuit 5, an output transformer 6, a load 7, and a discharging resistor 8.

The power supply 1 is constituted by a DC voltage source 11 and supplies energy to the oscillator.

FET2 is a power effect transistor, and the current flowing between the drain and source is controlled by the gate voltage VG.

The starting circuit 3 includes a resistor 31 and starts the FET 2 .

The charging current shunting circuit 4 is composed of a diode 41 and a resistor 42, and shunts the charging current of the capacitor 52 of the on-off circuit 5 when the FET 2 is turned on.

The FET on/off circuit 5 includes a free-wheeling diode 51, a capacitor 52, and a resistor 53.
By changing the voltage polarity of the gate voltage V, the gate voltage V is controlled to turn on and off the FET2.

The output transformer 6 has a primary winding A, a feedback winding B, and a secondary winding C.
A part of the power stored in the primary winding A is outputted to the load 7 via the secondary winding C, and a negative part is fed back to the FET 2 via the feedback winding B.

The voltages appearing in the primary winding A and the feedback winding B are in phase with each other.

The discharging resistor 8 discharges the charge accumulated in the capacitance formed between the gate and source 2 of the FET 2, thereby increasing the turn-off speed of the FET 2.

The operation of the self-excited oscillator shown in FIG. 2 having the above configuration will be explained below.

First, when a current flows from the direct voltage source 11 through the starting resistor 31, a voltage lower by the voltage drop is applied as the gate voltage vG, and the FET 2 is turned on. As a result, a voltage with the polarity shown by the solid line appears in the feedback winding B, and the resistor 53
, this is applied to the gate of the FET via the capacitor 52.
2 turns on quickly.

Therefore, the charging current flows in the direction of the solid arrow ON, the polarity of the voltage of the capacitor 52 is reversed, the value of the gate voltage 6 becomes lower than the dark value, and the FET 2 is turned off.

When FET2 is turned off, a charging current flows through the freewheeling diode 51 in the direction of the broken arrow OFF, and the charging current flows through the capacitor 5.
The voltage of No. 2 is higher on the cathode side of the diode 51. As a result, the diode 51 is turned off and the charging current meter F stops flowing.

At this time, the charging voltage of the capacitor 52 is the gate voltage ■6
In addition, FET2 is turned on.

When FET 2 is turned on, charging current flows through circuit 4 in the direction of arrow ON, charging capacitor 52 to the opposite polarity.

Therefore, v6 decreases and FET2 turns off. In this way, the FE 72 repeats on-off operations and continuously generates vibrations at a frequency determined by the circuit constants.

[Effects of the Invention] According to the present invention, when the FET 2 is turned on by the startup circuit 3, voltages with the polarities of ■ and e are generated in the feedback winding B, and the charging current flows through the circuit 4 in the direction of the solid arrow ON. flowing,
A capacitor forming the FET on/off circuit 5 is charged.

When the capacitor is charged, the voltage vG decreases and FET2
is turned off, a voltage with the polarity θθ shown by the broken line appears in the feedback winding B, a charging current flows in the direction of the arrow OFF, charging the capacitor with the opposite polarity, and FET 2 is turned on again in the same manner as described above.

Therefore, a simple and inexpensive self-excited oscillator can be obtained using one FET.

[Brief explanation of drawings]

1...Power supply, 2...FET. 3... Starting circuit, 4... Charging current shunting circuit, 5
...FET on/off circuit, 6...Output transformer, 7...Load, 8...Discharge resistor, A...Primary winding, B...Feedback winding, C
...Secondary winding. Figure 3: Configuration diagram of conventional technology

Claims (1)

[Claims] Between the drain and source of the field effect transistor (2),
The power source (1) and the primary winding (A) of the output transformer (6) are connected in series, and the field effect transistor (2) is connected between the power source (1) and the gate of the field effect transistor (2). starting circuit (
3), and further includes a field effect transistor on/off circuit ( 5), and a charging current shunting circuit (4) is provided between the gate and drain of the field effect transistor (2) to shunt the charging current of the capacitor when the field effect transistor (2) is on; A self-excited oscillator featuring: