JPS5829892B2 - semiconductor switch circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor switch composed of a thyristor (PNP) and a transistor (PNP).

FIG. 1 shows a conventional semiconductor switch circuit button and its driving circuit.

In the same figure, 5CR1 is a thyristor as a switching element, Dl is a diode, Ql is a transistor for driving the gate of thyristor 5CR1, SWl, SW
2 is a switch for controlling the transistor Q1.

EI is a power supply that represents the signal voltage equilaterally, and E2 is a power supply for one drive circuit.

Below, thyristor 5CR1 is in the off state, switch SW1
An explanation will be given of the operation when the thyristor 5CR1 is brought into conduction from the state in which SW2 is open and SW2 is closed.

When switch SW1 is closed and SW2 is opened, a current of E2/R1 flows between the emitter and base of transistor Q1.

The collector of transistor Q1 is diode DI and resistor R.
Since it is connected to the power supply E1 via GK1, G1 (E
A current of 2/R1) is applied.

Here, G1 is the current amplification factor of the common base of the transistor Q1.

G1 (E2/R1) becomes a gate drive current of the thyristor 5CR1, and the thyristor 5CR1 is turned on and becomes conductive.

However, when the polarity of the power source E1 is reversed and the signal voltage on the cathode side becomes positive, the gate current cannot flow, as can be seen from the fact that the diode D1 becomes reverse biased.

That is, in the semiconductor switch circuit having the circuit configuration shown in FIG. 1, when the voltage on the cathode side of the thyristor 5CR1 is higher than the base potential (earth in FIG. 1) of the driving transistor Q1, the thyristor 5CR1 is rendered conductive. I can't.

Here, the exchange generally uses 75 vrms as a ring signal.

When the semiconductor switch circuit having the configuration shown in FIG. 1 is used as a communication path switch, the voltage on the cathode side may become higher than the base potential of the transistor Q1 during driving, making it impossible to pass the calling signal.

Therefore, it was necessary to adopt an uneconomical method such as installing a paging signal sending circuit for each line.

The present invention was made to eliminate these drawbacks, and by using a PNP transistor as a control element, the thyristor can be driven even when the cathode potential becomes higher than the drive potential. It will be explained in detail according to the following.

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

In the same figure, G2 is the PNP junction transistor as the control element mentioned above, and the power supply E which represents the signal voltage
1 is also inserted on the anode side of the thyristor 5CR1 with positive polarity.

Regarding the size and drive circuit, the transistor Q3 and switches SW3 and SW4 have characteristics opposite to those of the corresponding elements shown in FIG. 1.

The operation will be explained below.

First, it is assumed that the thyristor 5CR1 is in an off state and biased by a signal voltage represented by the power source E1.

In this state, when switch SW3 is closed and SW4 is opened, the base current of transistor Q3 is
/R4 flows from the driving power source E2 side toward the emitter.

The collector of this transistor Q3 is connected to the power supply E1 via the emitter and base of the PNP transistor Q2.The collector current ■c3=β3IB3 reaches the base from the emitter of the transistor Q2 via the power supply E1 and the resistor RL. flow along the path.

Here, β3 is the common emitter current amplification factor of the transistor Q3.

On the other hand, this current is the 7 base current of transistor Q2.

At this time, the potential ■C3 at the collector of the transistor Q3 becomes vo3-E, -RL・■C3-VBo2, but the collector current ■ is smaller than the voltage of the power supply E1.

By selecting the parameter (3 from β3) so that the voltage drop ・■o3 due to
Since it can be made larger, transistor Q3 operates as a constant current.

Here, Vo2 is the base voltage VB2 of transistor Q2
, and the base of transistor Q2 can be biased to a constant voltage slightly below power supply E1.

On the other hand, the collector of transistor Q2 is connected to diode D1.
, are connected to the cathode of the thyristor 5CR1 via the resistor RCK1.

Here, if the cathode voltage is assumed to be ■, under the bias condition that ■B3>VK, even if VK>O, the transistor Q2
can cause a current to flow through the gate of the thyristor 5CR1 (the button in FIG. 2 is at ground potential, which fully satisfies the above conditions).

That is, power supply E1 - resistor RL - construction of transistor Q2 - collector thyristor 5 of transistor Q2
Gate current can be passed through the gate of CR1 (gate of CR1) through the route of G1.

Here, the voltage-current relationship in one drive state of the thyristor will be explained using a specific numerical example.

The current amplification factors β2 and β3 of transistors Q2 and G3 are set to β2-1. Let β3=0.5.

These values are values that can be easily achieved with semiconductor technology,
With appropriate design, transistor Q2. A feature of the present invention is that the thyristor 5CR1 can be driven with a constant gate drive current without saturating Q3.

Furthermore, as other numerical examples, El-E2=5v, RL-
2o.

Ω, R421.2 is Ω, and R325 is Ω.

Eo and ton are fixed signal voltages and resistances of each exchange circuit, while R2 and R3R4 are
With only the conditions on the drive circuit side of the switch circuit, El and R
It can be arbitrarily set independently of T.

In this example, all settings are set arbitrarily as an example for explanation.

When switch SW3 is closed and SW4 is opened, a current of ■B3=E2/R4ζ4mA flows through the base of transistor Q3, and ■B3・
A current of β3=2mA flows.

This current becomes the base current of transistor Q2, so
The collector of transistor Q2 has (■B3・β3) β2
=2mA current flows.

Therefore, the emitter current I of transistor Q2 is 4 mA, 2 mA flows to the collector of transistor Q3, and 2 mA flows to the collector of transistor Q3.
mA becomes the gate drive current of thyristor 5CRI.

Next, the potential relationship of each part will be explained.

In the above current relationship, the anode potential v of the thyristor 5CRI is VA=E, -RL-I,=4.2V, which is equal to the emitter potential of the transistor Q2.

: The base potential ■8□ of transistor Q2 and the collector potential Vc2 of transistor Q3 are equal, and from the above value Vc
3=VB2=V, -VBo2=4.2-0.7=3.5
V, and the transistor Q3 can operate as a constant current.

On the other hand, on the collector side of transistor Q2, V = 0.7V, V = 0.
Since it is connected to ground at 7V, transistor Q2
collector potential v.

2 is Vc2=1.4V (!:l, above) From the potential relation, the transistor Q2 can sufficiently operate as a current control.

In the explanation, the cathode of the thyristor 5CR1 is assumed to be at ground potential, but the collector and emitter voltages VcF, which are necessary for the transistor Q2 to operate as current control,
Let Vc,>IV, then in the above example, V.

2=4.2V, so v. 2=4.2V-1,5
V = 2.7V, and the cathode potential v of thyristor 5CR1 is = VC2 - VD - CK""1.3Vt
is allowed.

This is 4 when E=5V, and it is clear that when El>5V, it will operate even if the cathode potential is positive.

FIG. 3 is a circuit diagram showing another embodiment of the present invention.
A semiconductor switch circuit according to the conventional driving method shown in the figure,
By combining the thyristor shown in FIG. 2 according to the present invention, it is possible to drive the thyristor even if the cathode potential is higher or lower than the driving voltage. ,5CR
2) By connecting them in parallel with opposite polarities, signals can be transmitted in both directions.

In the figure, transistors Q1 and Q3 of the drive circuit and transistor Q2 as a control element correspond to those shown in FIGS. 1 and 2, respectively.

In the drive circuit, the emitter of transistor Q1 and Q3
The bases of transistor Q1 and the emitter of transistor Q3 are connected together to switch SW6, and the base of transistor Q1 and the emitter of transistor Q3 are connected together to switch SW5.

Here, this switch SW5 is a combination of switches SW1 and SW3 shown in FIG. 1 and FIG. , TTL, etc. are used.

Diodes D5 and D6 are thyristors 5CR1 and 5C
This prevents short-circuiting when the anodes of R2 are connected together to the emitter of transistor Q2, and the two can be electrically isolated.

Furthermore, the output of transistor Q2, which operates when the potential of the signal line is positive, is connected to diode D3. It is connected to the gates of thyristors 5CR1i- and 5CR2 through D4,
Similarly, the output of transistor Q1, which operates when negative, is connected to thyristors 5CR1 and 5CR through diodes DI and D2.
Connected to gate 2.

In addition, in FIG. 3, a bell circuit BEL is shown for operation explanation.
L, signal source v8, etc. are added.

When the semiconductor switch circuit is not driven, the switch S
Since W5 is off and SW6 is on, transistor Q
l, Q3 is also in the off state.

Here, when switch SW5 is turned on and SW6 is turned off, the current changes to R6Q3 as shown in Q1')"""""sws.
6-8-, the current flows through the transistors Q1 and Q3, but if the transistors Q1 and Q3 are configured with the same characteristics, for example, an IC on the same chip, the voltages between the base and emitter can be made the same, so the same current flows through the transistors Q1 and Q3. It can be passed on to Q3.

For example, if the current flowing through resistor R6 is 8 mA, then the current flowing through the emitter of transistor Q1 is 4 mA1.
A current of 4 mA can flow through the base of 3.

Thereafter, as explained using FIGS. 1 and 2, transistors Q2 and Q3 are
Alternatively, a gate drive current of 2 mA can be caused to flow by transistor Q1.

That is, when the potential of the signal line is positive, the diode DI
, D2 are reverse biased, and the collector current of transistor Q1 does not flow.

On the other hand, transistor Q2 is a switching element (S
CRISCR2) voltage across X and Y (hereinafter referred to as VX, ■Y
), one of the diodes D5 and D6 becomes conductive and the other becomes cut-off.

For example, in the case of vX〉■7〉0, the diode D6 is in the cutoff state and the diode D5 is conductive, and the collector current of the transistor Q2 as a control element driven by the transistor Q3 is the lower potential of the diodes D4 and D3. Thyristor 5CR through the other diode D3.
1 gate is driven.

At this time, the diode D4 is cut off, so the thyristor 5CR2 does not conduct.

That is, all gate currents controlled by transistors Q2 and Q3 flow to the gate of thyristor 5CR1.

When the potential of the communication line is negative, for example 0>vY>vXO, the diode D5. D6 is cut off, and the collector current of transistor Q1 flows through diode D2 to the gate of thyristor 5CR2.

At this time, the diode D1 is in a cutoff state, and the thyristor 5CR1 is not conductive.

FIG. 4 shows the relationship between the signal voltage (8) and the current flowing through the signal line in the circuit configuration of FIG. 3.

The telephone's bell circuit BELL is connected to the switch, but according to the equivalent circuit, the button can be changed with C and R.
A phase difference is generated between the signal voltage V and the signal current , which is determined by the circuit constant and the frequency of the signal voltage.

- Figure 4 shows the case where the phase of the current is advanced by θ.

As mentioned above, in FIG. 3, the transistor Q2 or Ql operates depending on the positive or negative voltage of the signal line, while the thyristor 5CR1 or 5C operates depending on the positive or negative current.
Diodes D1-D4 are turned on so that R2 operates.

This correspondence is shown in FIG. As can be seen from the above description, according to the circuit configuration of FIG. 3, the switch can be driven with any combination of voltage and current.

As explained above, the configuration of the semiconductor switch circuit according to the present invention has the following advantages.

(1) The switch can be driven without depending on the voltage of the signal line drive system.

(2) As explained in the configuration of FIG. 3, two types of drive circuits are combined into one and the switch can be driven by one TTL interface, so the configuration of the i+ leg system is simplified.

(3) Since the gate drive current of the switch can be designed to be the same regardless of the magnitude and polarity of the signal line voltage, the switching speed can be made the same.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an example of a conventional semiconductor switch circuit, Fig. 2 is a circuit diagram showing an embodiment of the present invention, and Figs. 3 and 4 are circuit diagrams and operation explanation diagrams of other embodiments. It is. 5CRI, 5CR2; Thyristor, Ql, Q3;
Transistor, Ql: PNP transistor as control element, D1-D6: diode, SW1-SW6: switch.

Claims (1)

[Claims] 1 Thyristors 5CR1 and 5CR2 connected in antiparallel as switching elements, and thyristors 5CRI and 5C
Two diodes D5 and D6 are connected in series between the anodes of R2 and have a common cathode, and operate when the potential of the signal line is positive, and their emitters are connected to the diodes D5 and D6.
6 and whose collectors are connected to the cathodes of thyristors 5CRI and 5 through diodes D3 and D4.
The transistor Q2 connected to the gate of CR2 operates when the potential of the signal line is negative, and its collector connects the thyristor 5CR1 to 5CR through the diodes DI and D2.
The emitter of the transistor Q1 is connected to the base of the transistor Q3, and the emitter of the transistor Q1 and the base of the transistor Q3 are connected to turn on the thyristors 5CR1 and 5CR2. When not turned on, the potential is lower than the base of the transistor Q1 and the emitter of the transistor Q3, and when turned on, the potential is higher than the paste of the transistor Q1 and the emitter of the transistor Q3. When the emitters of the thyristor 5CRISCR2 are not turned on, the potential is higher than the emitter button of the transistor Q1 and the base of the transistor Q3, and when the thyristor 5CRISCR2 is turned on, the potential is higher than that of the emitter button of the transistor Q1 and the base of the transistor Q3.
A semiconductor switch circuit characterized in that the emitter of transistor Q1 and the base of transistor Q3 are connected to a switch SW5 having a lower potential than the base of transistor JQ30, and the voltages between the base and emitter of transistor Q1 and transistor Q3 are made equal to have the same characteristics.