JPS59114718A - 2-wired electronic switch - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

FIELD OF THE INVENTION The present invention relates to a two-wire electronic switch connected between a load connected to one end of a power source and the other end of the power source for switching the load.

(Background of the Invention) Conventionally, a two-wire switch having the configuration shown in FIG. 1 is known. In the figure, 1 is a two-wire electronic switch, for example, a two-wire photoelectric switch, and has two output terminals Li and L2.
, switching transistor 11, constant voltage diode 112
, control circuit 13, constant voltage circuit 14 and diode 15
etc.

2 is a load, and 3 is a DC power supply. The switching transistor 11 and the constant voltage diode 12 are connected in series,
It is connected between output terminals L1 and L2. The control circuit 13 controls the base of the switching transistor 11, and turns off the switching transistor 11 when a light emitting circuit having a light emitting diode and the light reflected by the reflector 4 from this light emitting circuit enter, thereby turning off the reflected light. A light receiving circuit that drives the switching transistor 11 when no light is incident is provided. The constant voltage circuit 14 has an output terminal L1. It is connected in parallel with L2 and supplies a voltage to the control circuit 13 when the switching transistor 11 is off.

Generally, it is preferable for a two-wire electronic switch to have low leakage current when off and low residual voltage when on. Therefore, if the current consumption of the control circuit 13 as a leakage current during off-time is minimized, the circuit voltage can be reduced as much as possible. Therefore, when the switching transistor 11 is on, the output terminal Ll.

The voltage between L2 must be made extremely lower than when it is off, and at this time power to the control circuit 13 cannot be supplied from the constant voltage circuit 14. In addition, as shown in FIG. 1, a constant voltage diode 12 is inserted in series with the switching transistor 11, and the voltage generated across the constant voltage diode 12 is supplied to the control circuit 13 via a diode 15.

However, -〇1 As for the power supply voltage of the control circuit 13, in the case of a photoelectric switch that uses a light emitting diode as a light source, the forward voltage of the light emitting diode is as high as V, = 1.5 to 2■, and the current flowing through the light emitting diode is high. Since a voltage of about the same level is required for stabilization of the voltage, a voltage of about 4V is ultimately required. As mentioned above, this voltage is applied to the constant voltage diode 12 connected in series with the switching transistor 11.
Since it is supplied from diode 15 through diode 1
If the voltage drop of 5 is 0.7V, the voltage of the constant voltage diode will be at least 4.7V. Therefore, if the voltage of the voltage regulator diode is 47cm and the current flowing through the load is 200mA, the current to the control circuit 13 is extremely small, for example, about 1mA, as described above, and can be ignored. The power consumed is: P20.2 (A) x 4.7 (V) = 0.94
(W) However, there are disadvantages in that a constant voltage diode (16) and a large-capacity element are required, and internal heat generation of the two-wire electronic switch becomes large. Moreover, the output end L1. L
2 The residual voltage between the voltage regulator diode 12 is also 4.7
There is an inconvenience that the sum of Vsai and the saturation voltage Vsai of the switching transistor 11 is quite large.

(Object of the invention) The object of the present invention is to solve the problems of the conventional type described above.
The object of the present invention is to reduce internal heat generation and residual voltage in a two-wire electronic switch.

(Configuration and Effects of the Invention) The present invention provides a two-wire electronic switch that includes a switching element and a control circuit for the switching element, is connected in series to a load and a power source, and controls the load on and off. This is based on the concept of boosting and supplying the voltage across a constant voltage element connected in series with the switching element as the control circuit power supply when turned on.

Therefore, according to the present invention, since the voltage across the constant voltage element is increased, the voltage across the constant voltage element can be reduced. Therefore, it is possible to reduce the power consumption of the constant voltage element, that is, the product of the voltage across both ends and the load current, thereby reducing the heat generation inside the electronic switch and also reducing the residual voltage of the electronic switch.

(Explanation of Examples) Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 2 shows a circuit configuration of a two-wire electronic switch according to an embodiment of the present invention. Note that parts common or corresponding to those of the conventional example are represented by the same reference numerals.

The two-wire electronic switch shown in the figure is different from the conventional example shown in Fig. 1.
A booster circuit 16 is added instead of the diode 15. In the two-wire electronic switch shown in FIG. 2, the voltage of the control circuit 13 is 4V, and the boost ratio of the booster circuit 16 is 4V/
If it is 1.5V, the voltage across the constant voltage element is 1.5
■ is sufficient, and the switch residual voltage is different from C in Figure 1,
4.7-1.5 = 3.2M decrease. Further, the heat generation of the constant voltage element is also reduced to P2'+ 1.5vx 200mA, which is about % compared to the conventional example, and the heat generation is also reduced by that amount. Furthermore, since the power consumption of the constant pressure element is reduced by the input power of the booster circuit, the efficiency of the booster circuit need not be a problem. For example, if the current consumption of the control circuit is 1. If mA, the power consumption is 1 mA x 4 V = 4 mW,
To reduce the efficiency of the booster circuit to 70 cm (f required human power is 4 m
W/0.7 = 5.7 mW, the input conversion current is
I 1-5.7 mW/ 1.5 V'= 3.8 m
It becomes A. The load current of 200 mA is based on this input current 3.
The current is divided into 8 mA and constant voltage element current. In this way, the loss of the constant voltage element is reduced by the amount of current shunted to the booster circuit 16, and this amount is consumed by the booster circuit 16 and control circuit 13, so the internal heat generation of the switch does not affect the efficiency of the booster circuit. Become. Further, the minimum load that can be opened and closed by this electronic switch is a load that can flow the required current of 3.8 mA to the booster circuit.

FIG. 3 is a circuit diagram showing the two-wire switch of FIG. 2 in more detail. In the figure, the control circuit 13 includes a light receiving circuit 132 including a light receiving element 131 such as a first transistor, and a light emitting circuit 134 including a light emitting element 133 such as a light emitting diode.
1, a resistor 142, and a constant voltage diode 143, all of which are known.

The booster circuit 16 includes transistors 161, 162° inductor 163, resistors 164, 165, 166° 167, and diodes 1-168.

Next, the operation of the two-wire electronic switch shown in FIG. 3 will be explained. The light receiving element 131 is turned on while the light from the light emitting diode F133 is reflected by the reflector 4 and is incident thereon, and the transistor 11 is turned off when the base voltage becomes zero.

On the other hand, when reflected light no longer enters due to movement, rotation, etc. of the reflector 4, the light receiving element 131 is turned off.

Therefore, the transistor 11 is turned on, the load 2 is turned on, and the voltage across the constant voltage diode 12, for example, 1.5
A constant voltage Vz of V is generated. This voltage V2 is the resistor 164
is applied to the base of transistor 161 through transistor 161, which turns on and drives inductor 1-63. Next, when the voltage of the resistor 165 reaches the pace-emitter ON voltage of the transistor 162 due to the current of the inductor 163, that is, the emitter voltage of the transistor 161, the collector current of the transistor 162 flows slightly, increasing the base current, that is, the collector current of the transistor 161. decreases slightly. By this, inductor 1
63 tends to decrease, the inductor 163
A back electromotive force is generated, the voltage at the connection point 169 between the inductor 163 and the resistor 161 increases, and the base current is supplied to the transistor 162 via the resistor 167. Then, due to the positive feedback of the increase in the base current or collector current of the transistor 162 - the decrease in the base current or collector current of the transistor 161 - the increase in the back electromotive force of the inductor 163 - the increase in the base current of the transistor 162 via the resistor 167, the transistor 162 increases. Turning on and turning off the transistor 161 occurs rapidly. In addition, the voltage at the connection point 169 becomes a sufficiently high voltage of 5 V or more due to the back electromotive force of the inductor 163, so by rectifying this voltage with the diode p16g and charging the smoothing capacitor 135, For example, a voltage higher than .5V can be supplied to the control circuit 13.

Next, the energy stored in the inductor 163 is transferred to the control circuit 1
When the electromotive force decreases and the base current supplied via the resistor 167 becomes unable to maintain the transistor 162 in the on state, a positive feedback operation opposite to that described above causes the transistor l 61
, 162 is turned on or off and returns to the initial state.

Oscillation continues by repeating the above operations, and the voltage across the 5V constant voltage diode 1212 is boosted to 4V.

Note that in the conventional example, the switching transistor 1
When transistor 1 is on, the power supply voltage of control circuit 13 is higher than the emitter voltage of switching transistor 11,
The forward voltage is lower by 1-15.

Therefore, the control circuit 13 controls the switching transistor 1
1 cannot be directly driven to maintain the on state,
A drive circuit consisting of transistors 171 and 172 shown in FIG. 1 is required. However, in the two-wire electronic switch of the present invention, by using a booster circuit, the control circuit voltage is higher than the emitter voltage of the switching transistor 11, so the switching transistor is 11 can be driven directly.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional two-wire electronic switch, Fig. 2 is a circuit diagram of a 2#II type electronic switch according to an embodiment of the present invention, and Fig. 3 is a circuit diagram of a two-wire electronic switch of Fig. 2. FIG. 3 is a more detailed circuit diagram of the switch. ■・・・・・・2-wire electronic switch, 2・・・・・・
・Load, 3...Power supply, 4...Reflector, 11...Switching transistor,
12... Constant voltage diode, 13...
...Control circuit, 14... Constant voltage circuit,
16... Boost circuit, Ll, L2...
Output end. Patent Applicant Tateishi Electric Co., Ltd. Agent Patent Attorney Tatsuo Ito Agent Patent Attorney Tetsuya Ito

Claims (1)

[Claims] 1. One of the two output ends is connected to one end of the power supply via a load, and the other of this output end. is connected to the other end of the power supply to turn on and off the load 2
The # type electronic switch includes a switching element and a constant voltage element connected in series between the two output terminals, a control circuit for controlling on/off of the switching element, and a control circuit for controlling the switching element to turn on and off the switching element. The device is characterized by comprising a power supply circuit that supplies voltage from an output end to the control circuit, and a booster circuit that boosts the voltage across the constant voltage element and supplies it to the drive circuit when the switching element becomes conductive. 2-wire electronic switch.