JPH066628Y2 - Switching circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Application Field >> The present invention relates to a switching circuit that turns on and off a circuit in a subsequent stage according to the magnitude of an input voltage, as is typically known as a Schmitt circuit.

The circuit for "prior art" traditional this kind is a Schmitt circuit shown in FIG. 2 as described above is a typical example, when the input voltage V _in and the operation thereof will be described briefly is lower than the set voltage , The first transistor Q ₁₁ is non-conducting and the second transistor Q ₁₂ is conducting, and the first transistor Q ₁₁ is connected by the resistors R ₁₂ and R ₁₃ which divide the power supply voltage V _cc . It is biased with _one partial voltage ratio voltage V ₁ . Here, when an input voltage exceeding the voltage division ratio is applied to the base, the first transistor Q ₁₁ becomes conductive, whereby the base of the second transistor Q ₁₂ via the resistor R ₁₄ drops toward the ground side potential. the transistor _{Q 12} of the whore is nonconductive.

Due to this non-conduction, the resistor R ₁₂ is separated from the bias of the first transistor Q ₁₁ , so that the transistor Q ₁₁ has resistors R ₁₁ and R _{13 of the} power supply voltage Acc.
Second dividing ratio voltage V ₂ becomes, until said input voltage is the second voltage division ratio voltage V ₂ less transistor Q and
₁₁ is for maintaining a conductive state. Here, the first voltage division ratio voltage V ₁ > the second voltage division ratio voltage V ₂ is set to obtain hysteresis.

<Problems to be solved by the invention> However, the Schmidt circuit that has been used conventionally is
For example, the resistor R ₁₃ connected to the emitters of the transistors Q ₁₁ and Q ₁₂ is shared by the _first voltage division ratio voltage V ₁ and the second voltage division ratio voltage V ₂ , so that one of If a high voltage is set, the other one will inevitably become high, and it will be difficult to provide hysteresis, and it will be difficult to accurately set each of the above-mentioned voltages V ₁ and V ₂ due to the influence of the resistor R _{14 and the} like. Met.

<< Means for Solving Problems >> The present invention is, as a concrete means for solving the above-mentioned conventional problems, a first setting for determining an input voltage and starting an operation of a circuit connected to a subsequent stage. In a switching circuit having a voltage and a second setting voltage lower than the first setting voltage for stopping the operation, the first setting voltage is a first constant voltage diode, the second setting voltage is Second constant voltage diodes are respectively set, the first constant voltage diode is connected in series to the collector of the first transistor using the input voltage as a power source, and the second constant voltage diode supplies the input voltage as a power source. Is connected to the base of the first transistor, the cathode of the thyristor is connected to the collector of the first transistor, and the gate of the thyristor is connected to the first transistor. Through the constant voltage diode to the input voltage, the anode is connected to the power supply of the switching circuit and the base of the second transistor, and the collector of the second transistor is connected to the power supply of the switching circuit. By providing a switching circuit characterized in that it configures an output terminal, and controls a circuit in a subsequent stage by an output from the output terminal by turning on and off the second transistor, a first setting voltage and The second set voltage can be set individually and freely to solve the above-mentioned conventional problems.

<< Embodiment >> Next, the present invention will be described in detail based on an embodiment shown in the drawings.

FIG. 1 shows a switching circuit according to the present invention, in which the collector of the first transistor Q ₁ has a first set voltage V ₁ , that is, a Zener diode or the like having a voltage set to start the operation of a circuit connected in the subsequent stage. the first through the Zener diode ZD ₁ is connected to the input voltage V _in, and at the same time the base of the transistor Q ₁ is set voltage for stopping the operation of the second set voltage V _2, i.e. the circuit of the subsequent stage It is also connected to the input voltage V _in via the second constant voltage diode ZD ₂ . Further, the cathode K of the thyristor SCR is connected to the collector of the first transistor Q ₁ , the gate G of the thyristor SCR is connected to the input voltage V _in via the first constant voltage diode ZD ₁ , and the anode A is It is connected to the power supply _Vcc of this switching circuit. At this time, a resistor R ₁ is inserted between the gate G and the cathode K to obtain a voltage required for firing the thyristor SCR. Further, the anode A of the thyristor SCR is connected by a suitable circuit to a second transistor Q ₂ which is non-conductive when the thyristor SCR is conductive, and controls the subsequent stage by this output.

By doing so, in the switching circuit of the present invention, as the input voltage V _in rises, the second constant voltage diode ZD ₂ connected to the base of the first transistor Q ₁ is set to the second set voltage V ₂ . It becomes conductive, but at this time, a higher first set voltage V ₁ is set and the first constant voltage diode Z connected to the collector of the transistor Q ₁ is set.
Since D ₁ is still non-conducting, the transistor Q ₁ is not supplied with power and therefore does not operate and has no effect on subsequent stages.

Then, when the input voltage V _in exceeds the first set voltage V ₁ , the first constant voltage diode ZD ₁ is made conductive and the transistor Q ₁ is made conductive at the same time as the thyristor SCR.
Also ignites and conducts, which causes the second transistor Q
₂ to obtain the output for operating the circuit in the subsequent stage.

Next, the state where the input voltage V _in decreases will be described. First, when the input voltage V _in falls below the first set voltage V ₁ , the first constant voltage diode ZD ₁ stops conducting. However, the thyristor SCR still remains conductive and the first transistor Q ₁
Power supply to the input voltage V _in
Becomes a second set voltage V ₂ or less, the base voltage of the first transistor Q ₁ becomes a constant voltage diode ZD ₂
The transistor Q ₁ is turned off, and the thyristor SCR is turned off at the same time. Due to the transition of the thyristor SCR to the non-conductive state, the second transistor Q ₂ becomes conductive again, and the stop signal to the circuit in the subsequent stage is issued.

As is clear from the above description, the hysteresis set in the switching circuit of the present invention is set only by the voltages of the first and second constant voltage diodes ZD ₁ and ZD ₂ and other elements. Will not be affected by.

<< Effect of Device >> As described above, according to the present invention, the transistor and the thyristor are connected in series, and the base of the transistor is driven by the second constant voltage diode having the second set voltage, so that Since the gate is driven by the first constant voltage diode having the first set voltage, the switching circuit has the control right to the thyristor when turned on and the control right to the transistor when turned off, In addition, it is possible to obtain a free hysteresis and an accurate operating voltage easily so that they do not have a mutual relation, and thus it has an excellent effect in improving the performance of this kind of switching circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a switching circuit according to the present invention, and FIG. 2 is a circuit diagram showing a conventional example. Q ₁ ...... First transistor Q ₂ ...... Second transistor SCR ...... Thyristor ZD ₁ ...... First constant voltage diode ZD ₂ ...... Second constant voltage diode

Claims (1)

[Scope of utility model registration request] 1. A switching having a first set voltage for judging an input voltage and starting operation of a circuit connected to a subsequent stage, and a second set voltage lower than the first set voltage for stopping the operation. In the circuit, the first set voltage is a first constant voltage diode, the second set voltage is set by a second constant voltage diode, respectively, the first constant voltage diode is the input voltage as a power source. The collector of the first transistor is connected in series, the second constant voltage diode is connected to the base of the first transistor using the input voltage as a power source, and the collector of the first transistor is connected to a thyristor. Is connected to the cathode of the thyristor, the gate of the thyristor is connected to the input voltage through the first constant voltage diode, and the anode is the power supply of the switching circuit. To the bases of the second transistor is connected is connected, the collector of the second transistor constitutes the power connected to the output terminal of the switching circuit, on the second transistor,
A switching circuit, wherein a circuit in a subsequent stage is controlled by an output from the output terminal when turned off.