JPS6158196A - Automatic flasher - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic flasher for automatically turning on and off electricity to a load such as a lighting device according to ambient brightness.

<Prior art> In general, in this type of automatic flasher, in order to prevent an unstable state in which the load repeatedly turns on and off due to slight fluctuations in ambient illuminance, the switch is turned off when the ambient illuminance increases. It is necessary to provide a so-called hysteresis characteristic by creating a difference between the illuminance when turning off the lights and the illuminance when changing from turning off to turning on when the ambient illuminance decreases.

Conventional automatic flashers include popular models of thermal relay type using CdS and bimetal, and high-end models using CdS or phototransistors as light receiving elements.

FIG. 9 shows the circuit configuration of a thermal relay type automatic flasher. In this circuit, when the CdS is not exposed to light, the thermal relay contact TI remains closed, and when the CdS is exposed to light and the resistance value of the CdS decreases, the current flowing through the resistor R increases. Resistor R generates heat, and the thermal relay - contact TH opens due to the action of the bimetal. This automatic score 2:÷ utilizes the fact that the deformation of the bimetal has a hysteresis characteristic with respect to temperature.

In this thermal relay type automatic flasher, the lighting intensity is 20 to 80 (! Since they are large and have contacts, they have disadvantages such as a short switching life.

FIG. 10 shows a circuit configuration of an automatic flasher using CdS as a light receiving element.

When the illuminance of the CdS light receiving section is lower than the lighting illuminance, since CdS has a high resistance, the point ■ is at a low potential, and the point ■ is also at a low potential, so the transistor Tr21 is turned on.
Current flows for 2s. Then, the potential at the point ◎ rises, and the potential at the point ◎ also rises, so the transistor Tr22 is in an off state. At this time, the potential at point ■ is approximately 0■, and the transistor T r 23 is in an off state. Therefore, the current flows through the resistor R3o to the thyristor Th2. flows into the gate of , thyristor "rh2." turns on,
Triac T2 via diode bridge DB21
] turns on. The load is then turned on.

When the illuminance of the CdS light-receiving section is equal to or higher than the extinguishing illuminance, the resistance value of the CdS decreases, so the potential at point (2) increases, and the potential at point (2) also increases, so that the transistor Tr21 is in an off state. At this time, points ◎ and ◎ are resistances Rxb and R2
The potential is resistance-divided by T and Rss, and the potential at this point turns on the transistor Tr,2. When the transistor Tr22 is in the on state, a current flows through the resistor R2q, the potential at point ■ increases, and the transistor 'l''r
23 is turned on, the transistor Tr23 draws a current from the gate of the thyristor Th21 as a collector current along with the current flowing through the resistor R30, so the thyristor Th2+ is turned off. Thyristor'rh2
．． When the triac T21 is turned off, the triac T21 is also turned off, and the load is turned off.

Note that in this circuit, the operating illuminance is adjusted by the resistor R22. In addition, a capacitor Cμ is provided as a delay element in order to prevent malfunction due to instantaneous light.

The automatic flasher shown in Fig. 10 requires the above-mentioned complex circuit to provide hysteresis characteristics for turning on and off, and is also composed of a Zener diode ZD, a diode D, a capacitor CZ2, a resistor R2i, etc. The drawbacks were that it required a constant voltage circuit, had a large number of parts, and was expensive.

<Objective of the Invention> The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide an automatic flasher in which the circuit is converted into a WJ vehicle by utilizing the gate trigger characteristics of a thyristor.

<Configuration of the Invention> In the present invention, an automatic flasher that controls power supply to a load according to the surrounding illuminance includes a circuit that detects the surrounding illuminance;
It is equipped with a thyristor to which a current corresponding to the output signal of the above circuit is applied as a gate current, and a circuit that controls the power supply to the load by turning on and off the thyristor. The feature is that the difference between the current for turning on the gate for the first time from a non-conducting state is used as a hysteresis characteristic.

<Example> An embodiment of the present invention will be described below.

FIG. 1 shows the circuit configuration of the first embodiment. The power terminal 2 is connected to the input terminal 5 of the diode bridge DB, the load terminal 4 is connected to the input terminal 6 of the diode bridge DB, and the common terminal 3 is connected to the power terminal 2 via the surge killer ZNR.

A resistor R1 and a capacitor CI are connected in series between the output terminals 7 and 8 of the diode bridge DB, and the anode of a thyristor Th is connected to the terminal 7, and the cathode of this thyristor Th is connected to the 0111 child 8. Ru. Further, a resistor R2 and a resistor R3 are connected in series between terminals 7 and 8, the collector of a transistor Tr is connected to the connection point (3) between the resistors R2 and R3, and the emitter of this transistor Tr is connected to the terminal 8. Ru. In addition, the transistor Tr
A resistor R4 and a capacitor c2 are connected in parallel between the terminal 8 and the terminal 8, and the anode of the amorphous solar cell SB is connected to the terminal 8. and grounded.

Amorphous solar cell SB is used as a light receiving element.

As shown in FIG. 2, the thyristor Th has an anode A,
It is a semiconductor device having three terminals, a gate G and a cathode, and has a four-layer P N P N JM structure as shown in FIG. In this thyristor Th, the minimum gate current required to continue the off state, that is, the gate current when transitioning from the on state to the off state, and the minimum gate current required to transition from the off state to the on state. There is a difference. This is because the thyristor repeats on and off states until it is completely turned off, and in the on state, the junction capacitance Cj2 of the reverse bias junction J2 is charged with electric charge.

FIG. 4 shows an example of the output characteristics of the amorphous solar cell SB with respect to the A light source. This is a characteristic of an amorphous solar cell with a light-receiving area of 300 square meters, and a photovoltaic voltage sufficient to turn on a transistor can be obtained even with an illuminance of about 1 Qffx. Note that the output current Is is proportional to the effective light receiving area as well as the illuminance.

Hereinafter, the circuit shown in FIG. 1 +A? The operation of the automatic flasher 1, which consists of two components, will be explained below.

The area around the automatic ω blinker 1 is dark, and the amorphous solar cell S
When the illuminance of the light-receiving surface of B is sufficiently low, the photovoltaic current supplied from the amorphous solar cell SB to the base of the transistor Tr is small, and the collector current of the transistor Tr decreases, so full-wave rectification is performed by the diode bridge DB. The generated alternating current flows into the gate of the thyristor Th via the resistor R2.

When this gate current exceeds the minimum gate current required to turn on the thyristor Th, the thyristor Th is turned on and power is supplied to a load (not shown) connected to the load terminal 4.

On the other hand, when the surroundings of the automatic flasher 1 are bright and the illuminance on the light receiving surface of the amorphous solar cell SB is sufficiently high, the photovoltaic current supplied from the amorphous solar cell SB to the base of the transistor Tr increases, and the The collector current increases, drawing current from the gate of thyristor Th along with the current flowing from resistor R2. Then, when the gate current of the thyristor Th becomes less than the gate current required to turn off the thyristor Th, the thyristor Th is turned off and power supply to the load connected to the load terminal 4 is stopped.

In this way, the difference between the gate current when the thyristor Th turns on and the gate current when the thyristor Th turns off causes a difference in the illumination intensity when turning on the power supply to the load and the illuminance when turning off the power supply. can be added to provide hysteresis characteristics.

Next, the circuit shown in FIG. 1 described above will be quantitatively analyzed.

Now, the voltage at point ■ is VG-, and the voltage at point ■ is ■△-hi.

The gate-on current of thyristor Th is I g (ON)
.

The gate off current of thyristor Th is -1g (OF'F
).

Lg is the current flowing into the gate of thyristor Th.

It is assumed that the collector current of the transistor Tr is Ic', the current amplification factor of the l-run risk Tr is hPE, and the photovoltaic current of the amorphous solar cell SB is Is. Then, the forward voltage of the diode 11 of the diode bridge D'B is set to VD, the voltage between the gate and cathode of the thyristor Th is set to vG-, and the power supply voltage and frequency are set to AClooV.

If it is 60Hz, the maximum value between point 0 layer ■ is 100X
A voltage having a waveform shown in FIG. 5 is applied to FT-2VD-VG-. Then, the current □ scale 2 flowing through the resistor R2 to the point ■ has the waveform shown in FIG. therefore,
The current Lg flowing from the point ■ to the gate of the thyristor Th is, and the maximum value Lg (MAX) of the gate current 6g is: Since the photovoltaic current Is is proportional to the illuminance L (NX),
Is=,yL. However, le is a constant [μA/βX]. Therefore, it can be expressed as R3.

(i) When the load turns on from off: When the condition Lg(MAX)≧Ig(ON) is satisfied, the load turns on. Therefore, the illuminance L (ON) when the load is turned on is determined from formula (11) when the load changes from on to off during the period of Δt when the voltage between points ■ and ■ shown in Figure 5 is OV. The current of I g (OFF) is passed through the thyristor T.
When it is pulled out from the gate of h, thyristor Th is turned off. In this case, since the first term on the right side of equation (2) is 0, the load is turned off when the minimum value t g (MIN) of the gate current satisfies the condition Lg (old N)≦−1g (OFF). Therefore, the illuminance L (OFF) when the load is turned off can be given a hysteresis characteristic by the difference in illuminance shown by the above equations 0 and 0 from equation (2).Resistance R2゜R3 and I g (ON ),
The operating illuminance and hysteresis characteristics can be adjusted by controlling the gate conditions of the thyristor Th, such as I g (OFF).

In the circuit of FIG. 1, resistor R4 and capacitor C2 are:
This is a delay circuit to prevent malfunction with respect to instantaneous light, and the delay time is determined by the time constant T=R<XC2. In addition, the resistor R1 and capacitor C1 have a voltage increase rate d v /
This snubber circuit has a buffering effect to prevent malfunction and destruction of the thyristor Th due to the application of a forward voltage with a large dt, that is, a rapidly rising forward voltage.

FIG. 7 shows the circuit configuration of the second embodiment. Thyristor T
The circuit consisting of the gate trigger circuit, delay circuit, and amorphous solar cell SB of h is the same as the circuit of FIG. 1 described above. The difference is that a triac T is connected between the load terminal 4 and the power supply terminal 2, and the gate of this triac T is connected to the input terminal 5 of the diode bridge DB.

Further, a resistor R13 is connected between the gate of the triac T and the power supply terminal 2, and an input terminal 6 of the diode bridge DB is connected to the load terminal 4 via a resistor Rt2. Further, a resistor Rn and a capacitor C1l are connected in series between the load terminal 4 and the power supply terminal 2.

In this circuit, the gate trigger operation of the thyristor Th is similar to the circuit shown in FIG. 1 described above. In this circuit, the thyristor Th is used for switching the triac T, and by allowing a relatively large current to flow through the triac T, the operating illuminance and hysteresis characteristics are constant regardless of the capacity of the load.

The operation of the circuit shown in FIG. 7 will be quantitatively analyzed below.

(i) When the load turns on from OFF As in the first embodiment described above, the thyristor Th turns on when the following conditions are satisfied. When the thyristor Th turns on, current flows through the resistor R13, turning on the triac T. Then the load is turned on. When the load is in the on state, the triac T and the thyristor Th are in the operating state of repeating on and off, as shown in FIG.

(ii) When the load changes from on to off In FIG. 8, the load changes from on to off when triac T is off and thyristor Th cannot be turned on. Therefore, the load is turned off when the condition is satisfied.

■α in the formula is a positive value, and L (OFF) =
L(ON) +α, which indicates the width of hysteresis. The cause of this α is that the thyristor repeats on and off states until it is completely turned off.
This is because the junction capacitance Cjz of the reverse bias junction J2 is charged with electric charge in the on state (see FIG. 3). Therefore, the collector current 1c of the transistor Tr needs to be larger when the load is turned off than when the load is turned on. The value of α is determined by the gate conditions of the thyristor Th. And resistors R14 and R15゜I
The operating illuminance and hysteresis characteristics can be adjusted by controlling the gate conditions of the thyristor Th, such as g(ON) and junction capacitance.

In the circuit of Fig. 7, resistor R+e and capacitor CI2
is a delay circuit for preventing malfunction with respect to instantaneous light, and the delay time is determined by the time constant T=R113XC12. Moreover, the resistor R11 and the capacitor C11 are
This is a snubber circuit for preventing malfunction and destruction of the triac T due to the application of a voltage with a large voltage increase rate dv/dt. Surge killer ZNR absorbs surges when the load is turned on and off.

<Effects of the Invention> As explained above, in the present invention, the difference in gate current required for turn-on and turn-off of a thyristor is utilized to provide hysteresis characteristics when the load is turned on and off. This eliminates the need for a circuit for obtaining hysteresis characteristics, a constant voltage circuit, etc., greatly reducing the number of parts and making it possible to achieve lower costs and smaller size.

Also, depending on the adjustment of the circuit constants and the specifications of the thyristor, for example, the lighting illuminance of the load is 5 to 20 [nX].

The illuminance when the lights are turned off is 2.5 times or less than the illuminance when the lights are turned on.
There is little variation in temperature, and the current consumption is 3. (m
A) With the following, high performance can be achieved at the same time, such as an opening/closing life of 4,000 times or more.

Note that the automatic flasher according to the present invention can be applied to home electronics such as automatic blinds, automatic curtains, or automatic fans in addition to various lighting devices.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of the first embodiment of the present invention, FIG. 2 is a diagram showing the symbol of thyristor Th, and FIG. 3 is a diagram showing the symbol of thyristor Th.
Figure 4 shows the schematic configuration of the amorphous solar cell S.
Graph showing the output characteristics of B. Figure 5 is a waveform diagram of the voltage between points ■ and ■. Figure 6 is a waveform diagram of the current flowing to point ■. Figure 7 is a circuit of the second embodiment of the present invention. 8 are waveform diagrams of the power supply voltage and the voltage of the triac T, and FIGS. 9 and 10 are circuit diagrams showing conventional examples of automatic flashers. SB - Amorphous solar cell T r-) Run risk Th... - Thyristor DB - Diode bridge T - Triac

Claims (1)

[Claims] (1) In an automatic flasher that controls power supply to a load according to the ambient illuminance, a circuit that detects the ambient illuminance, a thyristor to which a current according to the output signal of the circuit is given as a gate current, and this thyristor It is equipped with a circuit that controls the power supply to the load depending on the conduction and non-conduction of the gate, and uses the difference between the gate-on current when the conduction state is repeated and the current that turns the gate on for the first time from the non-conduction state as a hysteresis characteristic. An automatic flasher characterized by: