JPS6056063B2 - Intermittent signal generation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an improvement of an intermittent signal generation circuit using a semiconductor device, and in particular, controls a breakover voltage using a gate bias voltage, and maintains an on state between an anode and a cathode after a breakover. A conventional intermittent signal generating circuit of this type using a field effect switching element will be described with reference to FIGS. 1a and 1b.

Conventional circuits of this type basically use switching elements such as thyristors that require a gate trigger current as semiconductor devices to construct the circuits shown in FIGS. 1a and 1b. Figure 1a shows an example using a switching element 1a that turns on when the gate 4 becomes a low potential with respect to the anode 2, and the same figure shows an example that turns on when the gate 4 becomes a high potential with respect to the cathode 3. This is an example in which a switching element lb is used. First, FIG. 1a will be explained. Resistor 5 and resistor 6 connected in series to power supply 9
The potential of the gate 4 of the thyristor 1a is determined by dividing the voltage. A charging current flows from the power supply 9 to the capacitor 8 through the resistor 7. This charging current causes a voltage drop across the resistor 7, and since the resistance values of the resistor 5 and resistor 7 are set so that the potential is lower than the potential of the anode 2 of the thyristor 1a, no gate current flows and the switching Element 1a remains off. As the capacitor 8 is charged, the charging current flowing through the resistor 7 decreases, and the voltage drop across the resistor decreases. Therefore, when the potential of the anode 2 becomes higher than the potential of the gate 4 and a gate current flows, and this gate current becomes larger than the gate trigger current of the switching element 1a, the switching element 1a is turned on and the charge in the capacitor 8 is increased. discharge. This discharge current is 'switching element 1a
When the holding current becomes less than or equal to the holding current, the switching element 1a is turned off and charging of the capacitor 8 starts. In this way, one on/off cycle of the main current circuit between the capacitor 8, the anode 2 of the switching element 1a, the cathode 3 of the switching element 1a, and the capacitor 8 is achieved. By changing the division ratio of the resistors 5 and 6 to change the gate potential, the terminal voltage of the capacitor 8 when the switching element 1a is turned on can be changed. In this circuit, the gate current flows through resistor 6 and resistor 7.

Since the switching element 1a will not turn on unless the gate current is greater than the gate trigger current, the values of the resistors 6 and 7 must be set so that the gate current is greater than the gate trigger current. On the other hand, since the current flowing through the resistors 5 and 6 becomes a loss, the values of the resistors 5 and 6 are preferably larger. Further, in order to lengthen the repeated charging and discharging time of the capacitor 8, it is necessary to increase the charging time constant, and for this purpose, the value of the resistor 7 may be increased. As mentioned above, the gate current must be made larger than the gate trigger current, so the resistor 7 cannot be made infinitely large.

Since the gate trigger current tends to increase when the switching element 1a has a large capacity, the resistors 5, 6 and 7
This made it difficult to use as an intermittent signal generation circuit. FIG. 1b shows an example in which a switching element 1b which is turned on when a high potential is applied to the gate 4-power sort 3 is used. In this case as well, as in the case of FIG. 1a, the resistors 5, 6 and 7 are too large to be used as an intermittent signal generating circuit. In view of the above points, the present invention was made to solve such problems and eliminate such drawbacks.The purpose of this invention is to use a simple circuit configuration to reduce the value of the capacitive element even when increasing the time constant. It does not need to be large, and the loss is proportional to the capacity and can be kept low.
Another object of the present invention is to provide an intermittent signal generating circuit which can also use a large current field effect switching element and which can directly extract a large current between output terminals.

In order to achieve such an object, the present invention connects a series circuit of a capacitive element and first and second impedance elements to a power supply, and allows the breakover voltage to be controlled by the gate bias voltage. An anode electrode of a field effect switching element having a property of keeping the voltage in an on state is connected to a connection point between the positive electrode side of the power source and the capacitance element, and a cathode electrode is connected to a connection point between the capacitance element and the first impedance element. The gate electrode is connected to the connection point between the first impedance element and the second impedance element connected to the negative electrode side of the power supply.

An embodiment of the present invention will be described below with reference to FIG.

FIG. 2 shows a circuit according to one embodiment of the invention.

The circuit shown in FIG. 1 can be constructed by using a field effect switching element instead of the switching element 1a or 1b, but it can be constructed more easily as shown in FIG. 2 by making good use of the characteristics of the field effect switching element. The configuration of the circuit shown in FIG. 2 will be explained. In FIG. 2, a power supply 9, a capacitor 8, a resistor 71, and a resistor 72 are connected in series to form a closed circuit. An anode terminal 2 of a field effect switching element 1 constituted by, for example, a normally-on type electrostatic induction thyristor is connected to the connection point between the power supply 9 and the capacitor 8 . On the other hand, the cathode terminal 3 is connected to the connection point between the capacitor 8 and the resistor 71, and the gate terminal 4 is connected to the connection point between the resistor 71 and the resistor 72 to form the circuit shown in FIG. The capacitor 8 and the resistor 71 serve as a voltage application circuit for the field effect switching element 1, and the resistor 71 also serves as a gate bias circuit for this element.

In FIG. 2, the field-effect switching element 1 changes its fluke over voltage depending on the voltage between the gate 4 and the cathode 3, as shown in the anode voltage-current characteristic diagram in FIG. 3, and is turned on after breakover. This is an element with excellent switching characteristics. At this time, no gate current flows. Referring to FIG. 2, a charging current flows from the power supply 9 to the capacitor 8 through the resistor 71 and the resistor 72. At this time, a voltage drop occurs across the resistors 71 and 72 due to the charging current.
The voltage drop across the resistor 71 is used as the gate cathode voltage VCK of the field effect switching element 1, and the terminal voltage of the capacitor 8 is set as the anode/cathode voltage VCK. Assuming that the resistance values of the resistor 71 and the resistor 72 are R7l and R72, respectively, the capacitance of the capacitor 8 is C8, and the power supply voltage is V9.

FIG. 4 is a diagram of voltage and current waveforms at various parts of the field effect switching element 1 constituting the intermittent signal generation circuit shown in FIG.

The anode-cathode voltage (■AK) and gate-cathode voltage (Vc8) of the field effect switching element 1
) is set by the above formula, but as shown in Figure 4A and b, ■ If A increases, ■.

will decrease. Here, when ■AK of the switching element 1 reaches a breakover voltage controlled by ■GK, the field effect switching element 1 turns on and discharges the charge of the capacitor 8. When the charge in the capacitor 8 is discharged and the gate-cathode voltage CK due to the charging current to the capacitor 8 becomes sufficiently large, the field effect switching element 1 enters the blocking state. Repeat this. The output voltage is ■. 1, that is, by changing the resistance R7l,
It can be changed by changing the ratio of R72, and the repetition frequency can be changed by changing the time constant of capacitor 8, resistor 71, and resistor 72.

In order to take out the output, it is sufficient to insert a load between the terminal 10 and the anode terminal 2. Note that FIG. 4C shows the anode current waveform. As explained above, this invention does not require the gate trigger current to flow, so the resistors 71 and 72
Since there is no voltage drop due to the gate current of the resistors 71 and 7
2 can be made infinitely large.

Therefore, even when increasing the time constant, it is not necessary to increase the value of the capacitor 8, and the loss is proportional to the capacitance. Therefore, the loss is low. Since no gate current flows, it can be used even with a large capacity field effect switching element 1.
A large current can be drawn directly between 0 and 0.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional intermittent signal generation circuit, where a is N.
In the case where a gate switching element is used, b shows an example using a P gate switching element.

Claims (1)

[Claims] 1 A field effect switching element that connects a series circuit of a power supply capacitance element and first and second impedance elements, and has the characteristic of being able to control the breakover voltage with the gate bias voltage and keeping the anode and cathode in the on state after breakover. an anode electrode is connected to a connection point between the positive electrode side of the power source and the capacitive element, a cathode electrode is connected to a connection point between the capacitive element and the first impedance element, and a gate electrode is connected to the connection point between the capacitance element and the first impedance element. An intermittent signal generating circuit, characterized in that the intermittent signal generating circuit is connected to a connection point with a second impedance element connected to the negative electrode side of the power source.