JPS6149855B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic switchgear having a time constant, and an object of the present invention is to provide an electronic switchgear that is simple and inexpensive and allows a wide selection of time constants by using generally commercially available electronic components. purpose.

In order to achieve the above object, the present invention uses a transistor as a switch element, and controls the transistor by using a field effect transistor (hereinafter referred to as "field effect transistor").
The feature is that it uses a FET (FET).

Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 is a circuit diagram of an electronic switchgear using PNP transistors and N-channel FETs. In the figure, 1 is an AC power supply, 2 is a full-wave rectifier, and 3 is a transistor, the emitter of which is connected to a positive input terminal P1 via a current limiting resistor 4.

A voltage divider 5 is connected in parallel with the transistor 3, and is composed of two resistors 6 and 7. 8 is a junction type and insulation type N-channel FET, and transistor 3
It is inserted and connected to the base of the voltage divider 5 and the voltage dividing point of the voltage divider 5.
Reference numeral 9 denotes an electrolytic capacitor connected in parallel with the resistor 7 on the negative side of the voltage dividing point of the voltage divider 5. This electrolytic capacitor 9 is inserted between the source and gate of FET 8, and when the voltage at both poles of electrolytic capacitor 9 is low, FET 8 is turned on. 10 is a resistor inserted between the collector of the transistor 3 and the negative input terminal P2, and through this resistor 10,
The gate of FET8 is connected to the negative input terminal _P2 . 11 is a load that is turned on and off by this device P.

Next, its effect will be explained.

When this device P is connected to a circuit that uses as a power source a full-wave rectifier of alternating current using the full-wave rectifier 2, a forward potential is applied to the transistor 3 and FET 8, and the electrolytic capacitor is initially charged. , and the values of resistors 6 and 7 are set considerably higher than the values of resistor 4 and the internal resistance of FET 8, so most of the current flows through resistor 4, the emitter and base of transistor 3, the drain of FET 8, and Electrolytic capacitor 9, resistor 10 via source
A current rapidly flows through the circuit passing through the resistor 6, and the electrolytic capacitor 9 starts to be charged.On the other hand, the electrolytic capacitor 9 is also charged by the circuit current passing through the resistor 6.

When device P is connected in this way, current flows rapidly into the base circuit of transistor 3 via the drain and source of FET 8, so transistor 3
immediately becomes conductive, and current is also supplied to the load 11.

The transient characteristics of this device P are resistances 4, 6, 7, 10
It is approximately determined by the internal resistance of FET 8 and the values of electrolytic capacitor 9.

Over time, following this transient characteristic
A current flows between the drain and source of FET8, charging the electrolytic capacitor 9 progresses, and the negative potential between the gate and source of FET8 gradually increases.
Eventually, the potential across the electrolytic capacitor 9 increases to FET 8.
When approaching the pinch-off voltage of FET 8, the current flowing between the drain and source of FET 8 becomes much smaller than the initial current value, and the base current decreases, so the current between the emitter and collector of transistor 3 becomes much larger than the initial conduction state. It has a resistance value. Therefore, the voltage across voltage divider 5 increases,
The current through resistor 6 increases rapidly. This increased current further accelerates the charging of the electrolytic capacitor 9, instantaneously exceeding the pinch-off voltage of the FET 8, and completely turning off the drain and source. Therefore, transistor 3 is also completely turned off, and no current flows to load 11 either.

After that, approximately the resistors 6 and 7 of the voltage divider 5, and the resistor 10
Due to the voltage division ratio, the terminal voltage of the electrolytic capacitor 9 is maintained at a constant voltage, and the voltage between the gate and source and between the gate and drain of the FET 8 is also maintained at a constant voltage, so that the transistor 3 maintains a completely off state.

Next, Figure 2 shows the case where an NPN type transistor is used and a P channel type FET is used. In the figure, 1 is an AC power supply, 2 is a full-wave rectifier, 3 is a transistor, and its collector is a current-limiting resistor 4.
The emitter is connected to the positive input terminal P1 through the terminal P1, and the emitter thereof is connected to the negative input terminal P2.

A voltage divider 5 is connected in parallel with the transistor 3, and is composed of two resistors 6 and 7. Reference numeral 8 denotes a junction type and insulation type P-channel FET, which is inserted and connected to the base of the transistor 3 and the voltage dividing point of the voltage divider 5. 9 is a resistor 7 on the positive side of the voltage dividing point of the voltage divider 5.
This is an electrolytic capacitor connected in parallel with. This electrolytic capacitor 9 is inserted between the source and gate of the FET 8. 10 is a resistor connected in series between the collector of the transistor 3 and the positive input terminal P1, and 11 is a load that is turned on and off by this device P.

Next, its effect will be explained.

When this device P is connected to a circuit that uses full-wave rectified alternating current by the full-wave rectifier 2 as a power source, a forward potential is applied to the transistor 3 and FET 8, and in the initial state, the electrolytic capacitor 9 is in an uncharged state, and the values of resistors 6 and 7 are set considerably higher than the internal resistance of FET 8, so most of the current flows through resistor 10, electrolytic capacitor 9, the source and drain of FET 8, and transistor 3. A current rapidly flows through the circuit passing through the base and emitter of the electrolytic capacitor 9, and at the same time, a part of the charging current also flows to the other resistor 6.

When device P is connected in this way, current rapidly flows to the base circuit of transistor 3 via the source and drain of FET 8, so transistor 3
immediately becomes conductive, and current is also supplied to the load 11.

The transient characteristics of this device P are resistors 6, 7, 10,
It is approximately determined by the internal resistance of FET 8 and the values of electrolytic capacitor 9.

Over time, following this transient characteristic
A current flows between the source and drain of FET8, charging the electrolytic capacitor 9 progresses, and the positive potential between the gate and source of FET8 gradually increases.
When the potential across the electrolytic capacitor 9 approaches the pinch-off voltage of the FET 8, the current flowing between the source and drain of the FET 8 becomes much smaller than the initial current value, and the base current decreases.
The resistance value between the collector and emitter of the transistor 3 becomes much larger than that in the initial conduction state. Therefore, the voltage across the voltage divider 5 rises, and the current flowing through the resistor 6 increases rapidly. Due to this increased current, the charging of the electrolytic capacitor 9 is further accelerated, and the pinch-off voltage of the FET 8 is instantly exceeded, and the connection between the source and the drain is completely turned off. Therefore, transistor 3 is also completely turned off, and no current flows to load 11 either.

After that, approximately the resistors 6 and 7 of the voltage divider 5, and the resistor 10
Due to the voltage division ratio, the terminal voltage of the electrolytic capacitor is kept at a constant voltage, and the voltage between the gate and source and between the gate and drain of the FET 8 is also kept at a constant voltage, and the transistor 3 also maintains a completely off state.

In both of the above embodiments, if the source and drain of the FET 8 are structurally equivalent, the source and drain of the FET 8 may be reversed in the circuit. Further, the current limiting resistor 4 may not be provided.

As explained above, in this invention, a transistor, which is a switch element of an electronic switchgear, is
Since the ON/OFF of this FET is controlled by a resistor and an electrolytic capacitor, all the components of the electronic switchgear can be replaced with commercially available products. Furthermore, the time constant can be accurately set to a desired value from a wide range by appropriately combining resistors and electrolytic capacitors, which are available in large quantities with various values. This makes it possible to easily and accurately manufacture various types of electronic switchgears with significantly different time constants using the same basic circuit.

Furthermore, the FET instantly changes the transistor
Since it can be controlled ON/OFF, it has good performance as a switchgear.

Therefore, as an application example, when this electronic switchgear is used in a cathode preheating circuit of a fluorescent discharge lamp,
Since sufficient preheating current can be obtained for the desired time at startup, there is no unnecessary damage to the cathode when starting the fluorescent discharge lamp, and since no cathode preheating current flows during lighting, it saves resources and energy. The role it plays is also enormous.

In addition, countless other wide-ranging applications can be considered, and the utility value of this invention is extremely significant.

[Brief explanation of the drawing]

The drawings show an embodiment of the invention, and FIG. 1 is a circuit diagram of an electronic switching device, and FIG. 2 is a diagram corresponding to FIG. 1 showing another embodiment. P1...Positive input terminal, P2...Negative input terminal, 3
...Transistor, 5...Voltage divider, 8...Field effect transistor, 9...Electrolytic capacitor, 10...Resistor.

Claims (1)

[Claims] 1. A transistor is used as a switch element to connect between positive and negative input terminals, a voltage divider is connected in parallel to the transistor, and a field effect transistor is connected with the voltage dividing point of the voltage divider as the base of the transistor. The resistance value of the voltage divider is set larger than the internal resistance value of the field effect transistor, and the gate of the field effect transistor is connected to one input terminal via a resistor, and this resistor is closer to the input terminal than the transistor. An electrolytic capacitor is inserted between the source and drain of the field effect transistor connected to the voltage dividing point of the voltage divider and the gate, so that the field effect transistor turns on when the voltage across the electrolytic capacitor is low. An electronic switchgear characterized by comprising: 2. The electronic switching device according to claim 1, in which a PNP transistor is used as the transistor, an N-channel field effect transistor is used as the field effect transistor, and the gate of the field effect transistor is connected to the negative input terminal. 3. The electronic switchgear according to claim 1, in which an NPN transistor is used as the transistor, a P-channel field effect transistor is used as the field effect transistor, and the gate of the field effect transistor is connected to the positive input terminal.