JP6942425B2 - Lighting device - Google Patents

Description

The present invention relates to a lighting device including a photoelectric automatic flasher.

There are known street lights that turn on automatically when it gets dark and turn off automatically when it gets bright. The lighting device used for such a street light uses a sensor such as a photodiode to detect the brightness of the external environment. The luminaire must not wiggle on and off when the surroundings are getting darker in the evening (or when the surroundings are getting brighter at dawn). In order to avoid these problems, a lighting device for street lights may use a CPU or an arithmetic circuit having a hysteresis characteristic.

For example, Patent Document 1 describes a lighting device that uses a CPU to stabilize automatic blinking control. The lighting device described in Patent Document 1 lights intermittently in a pulse at a frequency of 50 Hz or higher, determines the ambient illuminance in this intermittent section, and prevents self-blinking from affecting the sensor.

Further, for example, Patent Document 2 describes an electronic automatic flasher that smoothes the output voltage of a sensor, determines the smoothed voltage, and holds the state determined by the RS latch circuit. It should be noted that this electronic automatic flasher has a hysteresis characteristic to invert the determined state. That is, the automatic blinking control is stabilized by combining smoothing, hysteresis, and latch.

Japanese Unexamined Patent Publication No. 2003-163089 (Fig. 1) Japanese Unexamined Patent Publication No. 2013-171702 (Fig. 1)

Circuits with low power consumption and simple configuration may be driven using a Zener diode as a constant voltage source. The breakdown voltage of the Zener diode, which is the reference for the constant voltage, usually changes depending on the current and temperature, but if the breakdown voltage specification is set to 6.2V to 6.8V, it will be less affected by the current and temperature. Sometimes. That is, if a Zener diode having a breakdown voltage specification of 6.2V to 6.8V is used, a stable circuit can be configured with a simple configuration.

However, if the driving voltage of the electronic automatic flasher is 6.2V to 6.8V, the operating voltage does not match the CPU driven by a specific voltage such as 3.3V or 5.0V. That is, if a CPU is used to stabilize the automatic blinking control, it is necessary to prepare two power supplies, one for the sensor circuit and the other for the CPU. In particular, it is wasteful to use a CPU for a simple product (lighting device) that does not require a multifunctional CPU and prepare two power supplies.

Problems related to voltage also occur when using arithmetic circuits. The arithmetic circuit is usually made into an IC, and in order to enhance versatility, the working voltage is often set stepwise, such as for 5V and 15V. At this time, when driving the electronic automatic flasher at 6.2V to 6.8V, the arithmetic circuit cannot be used for low voltage (for example, 5V specification), so a higher-level one (for example, 15V specification) must be used. It disappears. Since the internal element size of the upper IC is large, it becomes redundant and causes unnecessary cost increase. Further, the arithmetic circuit often requires measures to prevent oscillation.

Therefore, the lighting device of the present invention was made in view of these problems, can be easily configured with only discrete parts, has more stable characteristics, and has good consistency with other circuits. It is an object of the present invention to provide a lighting device equipped with an automatic flasher.

In order to solve the above object, the lighting device of the present invention is a lighting device including a photoelectric automatic flasher, and the photoelectric automatic flasher includes a first Zener diode and a capacitor, and both ends of the first Zener diode. A power supply circuit that uses an inter-voltage as an output voltage, a sensor circuit that includes a series circuit with a photodiode and a resistor, a time-constant circuit that includes a resistor and a capacitor and smoothes the voltage obtained from the sensor circuit, and a FET and a resistor. A buffer circuit including a configured source follower, which is provided after the time constant circuit, and a first transistor and a second transistor, the base of the first transistor is connected to the source of the FET, and the second transistor A Schmidt trigger circuit whose base is connected to the collector of the first transistor and switches the output voltage according to the voltage of the source, a second Zener diode and a third transistor are included, and the cathode and the anode of the second Zener diode are respectively. It is characterized by including an output terminal of the Schmidt trigger circuit and an output circuit connected to the base of the third transistor.

The photoelectric automatic flasher included in the lighting device of the present invention supplies electric power to a sensor circuit, a buffer circuit, and a Schmitt trigger circuit by a voltage across the first Zener diode. In the sensor circuit, a current corresponding to the brightness of the external environment flows through the photodiode, and a voltage based on this current is output. The time constant circuit smoothes the output voltage of the sensor circuit so that the subsequent circuit operates stably even if the current flowing through the photodiode changes drastically in a short time. The buffer circuit is inserted so that the output voltage of the time constant circuit is not affected by the circuit in the subsequent stage. The Schmitt trigger circuit determines whether it is in a dark state or a bright state based on the output voltage of the time constant circuit, and outputs a signal. The smoothing function (high cut filter function) of the time constant circuit and the hysteresis characteristic of the Schmitt trigger circuit double stabilize the subsequent circuit (circuit controlled by the photoelectric flasher). The output circuit removes the bias voltage carried on the output signal of the Schmitt trigger circuit by the second Zener diode.

As described above, in the lighting device of the present invention, the photoelectric automatic flasher can be easily configured with only discrete parts. Further, in the lighting device of the present invention, the characteristics of the photoelectric automatic flasher are stabilized, and the consistency between the photoelectric automatic flasher and other circuits is improved.

It is a circuit diagram of the lighting apparatus shown as the embodiment of this invention. It is a circuit diagram of the photoelectric automatic flasher included in the lighting apparatus shown in FIG. FIG. 2 is a waveform diagram for explaining the operation of the photoelectric automatic flasher shown in FIG. 2, in which (a) is an input signal to a Schmitt trigger, (b) is an output signal from a Schmitt trigger, and (c) is a photoelectric automatic flasher. Indicates the output signal from the flasher.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 1 to 3. In the description of the drawings, the same or equivalent elements are designated by the same reference numerals, and duplicate description will be omitted.
() Indicates the matters specifying the invention shown in the claims.

FIG. 1 is a circuit diagram of a lighting device 10 shown as an embodiment of the present invention. In FIG. 1, a commercial AC power supply 11 is added for explanation. The lighting device 10 includes a fuse 12, a full-wave rectifier 13, a light emitting unit 14, a current limiting circuit 18, and a photoelectric automatic flasher 20.

The fuse 12 is a safety circuit inserted between the commercial AC power supply 11 and the full-wave rectifier 13 serving as the main power supply circuit. The full-wave rectifier 13 is a bridge circuit composed of diodes 13a, 13b, 13c, and 13d. The cathodes of the diodes 13a and 13c and the anodes of the diodes 13b and 13d are input terminals, the anodes of the diodes 13a and 13c are ground terminals, and the diode 13b. , 13d cathode serves as an output terminal for outputting a full-wave rectified waveform.

The light emitting unit 14 includes a diode 14a, an LED row 15 connected to the cathode of the diode 14a, a capacitor 16, and a resistor 17. The LED row 15 is a circuit in which a plurality of LEDs 15a are connected in series. When the voltage of the full-wave rectifier waveform output by the full-wave rectifier 13 is higher than the threshold voltage of the LED row 15, the full-wave rectifier 13 is emitted, and the full-wave rectifier 13 passes through the diode 14a, the LED row 15, and the current limiting circuit 18. The returning current flows. When the voltage of the full-wave rectified waveform output by the full-wave rectifier 13 is lower than the threshold voltage of the LED row 15, the diode 14a cuts off, emits the capacitor 16, and the current returning to the capacitor 16 flows through the LED row 15. The threshold voltage of the LED row 15 is the product of the forward drop voltage of the LED 15a and the number of series stages of the LED row 15. The capacitor 16 is charged when the voltage of the full-wave rectified waveform is higher than the threshold voltage of the LED row 15. The resistor 17 is a discharge resistor of the capacitor 16.

The current limiting circuit 18 is a so-called constant current circuit, and includes an LED current input terminal 18a and a control signal input terminal 18b. The current limiting circuit 18 switches between a state in which it operates as a constant current circuit and a state in which no current flows, depending on the signal input to the control signal input terminal 18b. The photoelectric automatic flasher 20 includes a power supply current input terminal 20a and a control signal output terminal 20b. A current limiting resistor 19a is inserted between the power supply current input terminal 20a and the output terminal of the full-wave rectifier 13. A pull-up resistor 19b is inserted between the control signal output terminal 20b and the power supply current input terminal 20a.

FIG. 2 is a circuit diagram of a photoelectric automatic flasher 20 included in the lighting device 10. As shown in FIG. 2, the photoelectric automatic flasher 20 includes a power supply circuit 21, a sensor circuit 22, a time constant circuit 23, a buffer circuit 24, a Schmitt trigger circuit 25, and an output circuit 26.

In the power supply circuit 21, the cathode of the Zener diode 21a (first Zener diode) is the power supply current input terminal 20a. A current is intermittently supplied from the full-wave rectifier 13 (see FIG. 1) to the power supply current input terminal 20a via the resistor 19a (see FIG. 1). Based on this current, the parallel circuit consisting of the Zener diode 21a and the capacitor 21b has a breakdown voltage of the Zener diode 21a (voltage between both ends of the Zener diode 21a) of 6.8 V, and is a sensor circuit 22, a buffer circuit 24, and a Schmidt trigger circuit. Power 25.

The sensor circuit 22 is a series circuit including a photodiode 22a and a resistor 22b. A current flows through the photodiode 22a according to the brightness of the external environment, and a voltage is generated between both ends of the resistor 22b based on this current.

The time constant circuit 23 includes a resistor 23a and a capacitor 23b, and smoothes the voltage obtained from the sensor circuit 22 (the voltage at the upper end of the resistor 22b). That is, the time constant circuit 23 prevents repeated lighting and extinguishing (flickering) even if the current flowing through the photodiode 22a changes so as to repeat in a short time.

The buffer circuit 24 constitutes a source follower with a FET 24a and a resistor 24b. Since the output terminal of the time constant circuit 23 (the upper end of the capacitor 23b) has almost no current supply capacity, a buffer circuit 24 (source follower) is provided between the output terminal of the time constant circuit 23 and the input terminal of the Schmidt trigger circuit 25. It is inserted to increase the current supply capacity.

The Schmitt trigger circuit 25 includes two transistors 25c (first transistor), 25d (second transistor), and resistors 25a, 25b, and 25e. The base of the transistor 25c is connected to the source of the FET 24a included in the buffer circuit 24, and the base of the transistor 25d is connected to the collector of the transistor 25c. In the Schmitt trigger circuit 25, the output voltage (collector voltage of the transistor 25d) is switched according to the voltage of the source of the FET 24a. Since the Schmitt trigger circuit 25 has hysteresis, the voltage for detecting a bright state is higher than the voltage for detecting a dark state.

The output circuit 26 includes a Zener diode 26a (second Zener diode) and a transistor 26b (third transistor). The cathode of the Zener diode 26a is connected to the collector of the transistor 25d, which is the output terminal of the Schmitt trigger circuit 25. The anode of the Zener diode 26a is connected to the base of the transistor 26b. The collector of the transistor 26b is the control signal output terminal 20b of the photoelectric automatic flasher 20 (open collector). A bias voltage is carried on the output signal of the Schmitt trigger circuit 25 due to the influence of the resistor 25e. Therefore, if the voltage of the output signal of the Schmidt trigger circuit 25 is higher than the sum of the breakdown voltage of the Zener diode 26a and the base-emitter voltage (0.6V) of the transistor 26b, the output circuit 26 causes the base current to flow through the transistor 26b. In this way, the influence of the bias voltage is removed. That is, the output circuit 26 constitutes a comparator or a waveform shaper only by the Zener diode 26a and the transistor 26b.

The operation of the photoelectric automatic flasher 20 will be described in more detail with reference to FIG. In FIG. 3, (a) is a waveform diagram of an input signal 31 applied to an input terminal of a Schmitt trigger circuit 25 in order to explain the overall operating characteristics of the photoelectric automatic flasher 20, and (b) is an input signal 31. The waveform diagram of the output signal 32 output from the Schmitt trigger circuit 25 according to the above, (c) is the waveform diagram of the output signal 33 output from the photoelectric automatic flasher 20. The vertical axis of FIGS. 3A to 3C is the voltage (V), and the horizontal axis is the time (t).

The input signal 31 shown in FIG. 3A imitates the voltage output of the sensor circuit 22. First, a voltage linearly increasing from 0V to a voltage VD (6.8V) is applied to the input terminal of the Schmitt trigger circuit 25, and then a voltage linearly decreasing from the voltage VD to 0V is applied. The voltage that rises linearly from 0V to voltage VD corresponds to the situation that changes from dark to bright, and the voltage that falls linearly from voltage VD to 0V corresponds to the situation that changes from bright to dark. do. Note that FIG. 3A shows two cycles of this voltage change.

As shown in FIG. 3B, the output signal 32 of the Schmitt trigger circuit 25 (collector voltage of the transistor 25d shown in FIG. 2) becomes a high level (voltage V3) when the input signal 31 exceeds the voltage V1 and becomes an input signal. When 31 falls below the voltage V2, it becomes a low level (voltage V4). At this time, the voltage V4 becomes the bias voltage. The output signal 32 exhibits a hysteresis characteristic with respect to the input signal 31. That is, the voltage V1 for detecting a bright state is higher than the voltage V2 for detecting a dark state.

As shown in FIG. 3C, the output signal 33 of the photoelectric automatic flasher 20 (collector voltage of the transistor 26b shown in FIG. 2) is low label (0V) when the output signal 32 of the Schmitt trigger circuit 25 is at a high level. ), And when the output signal 32 is low level, it becomes high level (VD). As shown in FIG. 1, since the control signal output terminal 20b is connected to the power supply current input terminal 20a via the resistor 19b, the high level is set to the voltage (6.8V) of the power supply current input terminal 20a. Become equal. When the high level voltage of the output signal 33 is to be 5V for a CPU, for example, the other end of the resistor 19b connected to the collector of the transistor 26b may be connected to the power supply wiring of the 5V system. Further, as described above, the sum of the breakdown voltage of the second Zener diode 26a and the base-emitter voltage (0.6V) of the transistor 26b is set between the voltage V3 and the voltage V4 (the Zener diode having an appropriate breakdown voltage is set. By selecting), the output signal 32 including the bias voltage can be converted into the output signal 33 indicated by two values of 0V or voltage VD.

As described above, in the lighting device 10, the photoelectric automatic flasher 20 can be easily configured only by discrete parts. Further, the photoelectric automatic flasher 20 can obtain stable characteristics as a result of double suppressing flicker by the time constant circuit 23 and the Schmitt trigger circuit 25. At this time, the output circuit 26 having a simple configuration including the Zener diode 26a has the output signal 32 in a situation where the Schmitt trigger circuit 25 simply configured with only discrete parts has to include a bias voltage in the output signal 32. Is corrugated into an output signal 33 without a bias voltage to improve consistency with other circuits.

10 ... Lighting device,
11 ... Commercial AC power supply,
12 ... Hughes,
13 ... Full-wave rectifier,
13a to 13d, 14a ... Diode,
14 ... Light emitting part,
15 ... LED row,
15a ... LED,
16, 21b, 23b ... Capacitor,
17, 19a, 19b, 22b, 23a, 24b, 25a, 25b, 25e ... Resistors,
18 ... Current limiting circuit,
18a ... LED current input terminal,
18b ... Control signal input terminal,
20 ... Photoelectric flasher,
20a ... Power supply current input terminal,
20b ... Control signal output terminal,
21 ... Power supply circuit,
21a, 26a ... Zener diodes (first and second Zener diodes),
22 ... Sensor circuit,
22a ... photodiode,
23 ... Time constant circuit,
24 ... Buffer circuit,
24a ... FET,
25 ... Schmitt trigger circuit,
25c, 25d, 26b ... Transistors (first, second, third transistors),
26 ... Output circuit,
31 ... Input signal,
32, 33 ... Output signal.

Claims (1)

In a lighting device equipped with a photoelectric automatic flasher
The photoelectric automatic flasher is
A power supply circuit that includes a first Zener diode and a capacitor and uses the voltage across the first Zener diode as the output voltage.
A sensor circuit including a photodiode and a series circuit with a resistor,
A time constant circuit that includes a resistor and a capacitor and smoothes the voltage obtained from the sensor circuit.
A buffer circuit that includes a source follower composed of FETs and resistors and is provided after the time constant circuit, and
It includes a first transistor and a second transistor, the base of the first transistor is connected to the source of the FET, the base of the second transistor is connected to the collector of the first transistor, and the output is made according to the voltage of the source. A Schmidt trigger circuit that switches the voltage and
It is characterized in that it includes a second Zener diode and a third transistor, and the cathode and anode of the second Zener diode are provided with an output terminal of the Schmitt trigger circuit and an output circuit connected to the base of the third transistor, respectively. Lighting device.

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