JPH0150297B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a load control circuit, and in particular to a load control circuit that maintains its power energized state for a predetermined time after switching off a load such as a lighting lamp, and then automatically depowers it. Related to load control circuits.

The prior art will be explained with reference to FIG. Electric power from the commercial AC power supply 1 is given to the illumination lamp circuit 3 from a load control circuit 2 interposed between lines 16 and 23. By pressing the push button switch 4, a load current flows through the primary winding 6 of the alternator 5, whereby the output from the secondary winding 7 is rectified by the diode 8, and the output from the secondary winding 7 is rectified by the diode 8. Charge 9. The output voltage of capacitor 9 is applied to the gate of field effect transistor 10. As the capacitor 9 is charged and the voltage at the gate of the field effect transistor 10 is reduced, the field effect transistor 10 is cut off. This interruption of field effect transistor 10 causes resistor 1 to be removed from line 11.
2. Gate of thyristor 13 and thyristor 1
A gate current flows through line 14 through cathode 3 as shown by arrow 15. This causes thyristor 13 to fire. Therefore, during the half cycle of the power supply voltage when line 16 has positive polarity, the line 16 connects the diode 17, line 11, thyristor 13, line 14, diode 18, and triax of the full-wave rectifier circuit 21 composed of diodes 17 to 20. A current flows through the gate of 22 and line 23 to fire the triac 22, thereby energizing the lighting circuit 3. In the next half cycle when line 23 is positive, line 23, the gate of triax 22, diode 19, line 11,
Current flows through thyristor 13, line 14, diode 20 and line 16 to ignite triac 22, thereby energizing lamp circuit 3. Such operations are repeated every cycle. When the push button switch 4 is cut off by releasing the push button switch 4, the capacitor 9 is gradually discharged over time by the discharge resistor 24 connected in parallel to the capacitor 9.
When the output voltage of capacitor 9 reaches a certain level, field effect transistor 10 becomes conductive. Therefore, thyristor 13 and triax 22 are cut off. In this way, the illumination lamp circuit 3 is energized by making the push button switch 4 conductive, and after the push button switch 4 is turned off, the power is energized by a time constant that depends on the capacitance of the capacitor 9 and the resistance value of the resistor 24. The lamp circuit 3 is kept energized for a predetermined period of time, after which the lamp circuit 3 is de-energized.

When the lamp circuit 3 is de-energized, ie when the field effect transistor 10 is conducting, a current flows from the line 11 through the resistor 12 and the field effect transistor 10 into the line 14. In order to increase the gate current of the thyristor 13 to ensure its firing, and to fire the thyristor 13 during periods of relatively low voltage in each half cycle of the supply voltage, the resistance value of the resistor 12 is reduced. There must be. If the resistance value of the resistor 12 is selected to be small, the current when the field effect transistor 10 is cut off increases, resulting in an increase in wasteful power consumption.

The lighting circuit 3 includes a discharge lamp 25 and a glow discharge lamp 2.
6. Noise prevention capacitor 27 and chiyoke 2
Contains 8. When the discharge lamp 25 is turned off, the impedance of the illumination lamp circuit 3 depends on the noise prevention capacitor 27 and has a large value. If the resistance value of the resistor 12 in the load control circuit 2 is selected to be small, line 1 of the load control circuit 2
The impedance between 6 and 23 is small. Therefore, a relatively high voltage is applied to the illumination lamp circuit 3 when the illumination lamp circuit 3 is de-energized. Therefore, the glow discharge lamp 26 starts discharging, and the discharge lamp 25 is erroneously turned on. In order to prevent the discharge lamp 25 from being erroneously turned on in this manner, the resistance value of the resistor 12 must be increased. If the resistance value of resistor 12 is chosen high,
The thyristor 13 and therefore the triax 22 are
Conducting occurs at relatively high voltage times in each half cycle of the power supply voltage, thus resulting in noise. Therefore, in order to prevent the generation of this noise, it is necessary to connect the coil 29 and the capacitor 30. By providing the capacitor 30, the impedance of the load control circuit 2 is reduced, making it easier for the glow lamp 26 to light up.

An object of the present invention is to provide a load control device that can reduce wasteful power consumption when the load is de-energized, and can conduct at the beginning of each half cycle of the power supply voltage while the load is energized. That's true.

FIG. 2 is an electrical circuit diagram of one embodiment of the present invention, and parts corresponding to those of the prior art shown in FIG. 1 described above are given the same reference numerals. Power from the AC power source 1 is applied to the lamp circuit 3 via a load control circuit 32 according to the invention connected between lines 16 and 23. In the load control circuit 32, a capacitor 9 is connected to the gate of the field effect transistor 10. When the push button switch 4 is turned on, a load current flows through the primary coil 6 of the current transformer 5, so that the voltage generated in the secondary coil 7 is rectified by the diode 8 and the capacitor 9 is charged. By charging the capacitor 9, the voltage at the gate of the field effect transistor 10 decreases, thereby causing the field effect transistor 10 to shut off. A triac 22 is connected in parallel to a series circuit consisting of the push button switch 4 and the primary coil 6 of the current transformer 5. A thyristor 13 and a full-wave rectifier circuit 21 are connected between the lines 11 and 14. A first series circuit 35 includes a first resistor 33 having a high resistance value and a transistor 34 as a first switching element, and a first series circuit 35 includes a second resistor 36 having a low resistance value and a transistor 37 as a second switching element. Two series circuits 38 are connected in parallel. First series circuit 35
and the second series circuit 38,
Field effect transistor 10 between lines 11 and 14
connected in series. Between lines 11 and 14,
A transistor 39 and a resistor 40 are connected in series, and their connection point 41 is connected to the gate of the thyristor 13.

A level discrimination circuit 42 is connected between the drain of the field effect transistor 10 and the line 11. This level discrimination circuit 42 includes resistors 43 and 44.
and a Zener diode 45. resistance 44
A connection point between the zener diode 45 and the zener diode 45 is connected to the base of the transistor 34. The collector of transistor 34 is connected to the base of transistor 37. The breakdown voltage VD of the Zener diode 45 is selected to be, for example, 6V.

The lighting circuit 3 includes a discharge lamp 25 and a glow discharge lamp 2.
6, a noise prevention capacitor 27, and a chiyoke 28. The discharge starting voltage of the glow discharge lamp 26 is set at approximately 63V, for example, according to Japanese Industrial Standards.

A neon discharge lamp 46 and a resistor 47 are connected in series between the lines 16 and 23. This neon discharge lamp 46 is turned on to provide a display when the illumination lamp circuit 3 is deenergized because the triax 22 has been cut off.

Assume that the push button switch 4 remains cut off, the triax 22 is cut off, and therefore the discharge lamp 25 of the illumination lamp circuit 3 is turned off.
The voltage waveform between lines 11 and 14 is as shown in FIG. In each half cycle of the power supply voltage from time t1 to t5, the Zener diode is cut off during the periods t1 to t3 and t4 to t5 when the voltage between lines 11 and 14 is less than the breakdown voltage VD of Zener diode 45. During the period from time t3 to time t4, when the voltage between the lines 11 and 14 is higher than the breakdown voltage VD, conduction occurs. The switching mode of this Zener diode 45 is shown in FIG. 32. The transistor 34 is cut off when the Zener diode 45 is cut off, as shown in FIG.
The Zener diode 45 becomes conductive, thereby making it conductive. Transistor 37 is made conductive when transistor 34 is turned off, and cut off when transistor 34 is made conductive, as shown in FIG.
When the discharge lamp 25 is turned off, the field effect transistor 10 remains conductive, so the transistor 3
As shown in FIG. 3, 9 is cut off regardless of the change in the switching mode of the transistor 37.
Therefore, the thyristor 13 continues to shut off as shown in FIG. 36.

During the period from time t1 to time t3, transistor 3
7 is conducting, so lines 16, 23
The impedance of the load control circuit 32 between them depends on the resistance value of the resistor 6, and the resistance value is small as described above. The output voltage of the commercial AC power supply 1 is on the order of 100V, and compared to this, the breakdown voltage VD of the Zener diode is about 6V as mentioned above, so the voltage between the lines 11 and 14 at times t1 to t3 is low. Therefore, the current flowing through resistor 36, transistor 37 and field effect transistor 10 is small. Therefore, the power consumption from time t1 to t3 is small. During the period from time t1 to time t3, the power supply voltage is lower than the discharge start voltage of the glow discharge lamp 26, and therefore the discharge lamp 25 is kept off.

During the period from time t3 to time t4, the Zener diode 45
and transistor 34 becomes conductive. Therefore, current flows from line 11 to line 14 via resistor 33 having a high resistance value, transistor 34 and field effect transistor 10. This time t3~t4
During the period , the resistance value between the lines 11 and 14 and therefore the impedance of the load control circuit 32 between the lines 16 and 23 becomes large. Therefore, the current consumption is small and the glow discharge lamp 26 remains off.

During the period from time t3 to t4, resistors 33 and 43
Since the resistance value of is large, the voltage between lines 16 and 23 is high. Therefore, the neon bulb 46 lights up.
It can be seen that the discharge lamp 25 is turned off by the lighting of the neon bulb 46.

During the period from time t4 to t5, the same operation as that from time t1 to t3 is performed. Also during this period, the power supply voltage is low, so the power consumption by the resistor 36 is small, and the low power supply voltage keeps the glow discharge lamp 26 off.

In order to turn on the discharge lamp 25, press the push button switch 4.
Press and operate. Due to this conduction of the push button switch 4, the glow discharge lamp 26 is turned on, the discharge lamp 25 is turned on, and the load current flows to the primary winding 6 of the current transformer 5. This charges the capacitor 9. Charging of capacitor 9 causes field effect transistor 10 to shut off. The voltage between lines 11 and 14 in this state is shown in FIG. 41. The time when the voltage between lines 11 and 14 is less than the breakdown voltage of Zener diode 45
During the period t1 to t3, the Zener diode 45 remains cut off as shown in FIG. 42. Therefore, transistor 34 is cut off as shown in FIG. 4. Therefore, the transistor 37 becomes conductive as shown in FIG. 4 during the period up to time t2, which is earlier than time t3, and the transistor 39 accordingly
conducts as shown in FIG. Due to the conduction of the transistor 39, current flows from the line 11 to the transistor 39, the gate of the thyristor 13, and the cathode of the thyristor 13.
Thyristor 1 at time t2 when the voltage between 1 and 14 is smaller than the breakdown voltage VD.
3 is fired as shown in FIG. The thyristor 13 remains conductive during the period from time t3 to time t5. Due to the conduction of the thyristor 13, during the half period of the supply voltage when the line 16 is positive, the line 16 is connected to the diode 17 to the line 1.
1, thyristor 13, line 14, diode 1
8. Gate of triax 22 and line 23
A current flows through the circuit, and the triac 22 fires. In the next half cycle when line 23 becomes positive, current flows from line 23 to the gate of triac 22, diode 19, line 11, thyristor 13, diode 20 and line 16, and triac 22 fires. In this way, time t2~
During the period t5, the triac 22 becomes conductive and the discharge lamp 25 is lit. During the period from time t1 to time t2, the transistors 37 and 39 are conductive, and at this time the resistance value depending on the resistances 36 and 40 between the lines 11 and 14 is small. Therefore line 16,
The impedance of the load control circuit 32 between the load control circuits 23 and 23 is small. Therefore, the thyristor 13 and therefore the triax 22 can become conductive at a time t2 very close to the time t1. The power supply voltage at time t2 is low, so there is no risk of noise occurring due to conduction of thyristor 13 and triac 22.

By shutting off the pushbutton switch 4, the capacitor 9 is activated by the resistor 24 over time.
It is gradually discharged. During a predetermined time period dependent on a time constant determined by the capacitance of capacitor 9 and the resistance value of discharge resistor 24, the operations described in connection with FIG. 4 are carried out. After that time, the conduction of the field effect transistor 10 causes the transistor 39 to shut off, so that the thyristor 13 is no longer fired. Therefore, the triax 22 is not ignited, and the discharge lamp 25 remains off.

As another embodiment of the present invention, the level discrimination circuit 4
2 may be realized by other configurations. The lighting circuit 3 may be replaced with another load.

As described above, according to the present invention, when the field effect transistor is conductive and the load is deenergized, if the power supply voltage is less than a predetermined level, the second
Although the switching element conducts and current flows through the second resistor, the power supply voltage at this time is low, so the power consumption is small, and when the power supply voltage exceeds a predetermined level, the first switching element conducts and the resistance becomes high. Since the current flows through the first resistor having a constant value, the power consumption is also low. When the field effect transistor is cut off, the triac becomes conductive when the power supply voltage is at least a value smaller than the predetermined level, that is, when the power supply voltage is low. Therefore, the generation of noise can be suppressed.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram of the prior art, FIG. 2 is an electric circuit diagram of an embodiment of the present invention, and FIG. 3 is a discharge lamp 25.
FIG. 4 is a waveform diagram for explaining the operation when the discharge lamp 25 is off, and FIG. 4 is a waveform diagram for explaining the operation when the discharge lamp 25 is on. 1...Commercial AC power supply, 3...Lighting circuit, 5...
... Current transformer, 8 ... Diode, 9 ... Capacitor, 10 ... Field effect transistor, 13 ... Thyristor, 21 ... Full wave rectifier circuit, 22 ... Triax, 24, 33, 36, 40, 43, 4
4, 47...Resistor, 25...Discharge lamp, 26...Glow discharge lamp, 27...Noise prevention capacitor, 3
4, 37, 39...Transistor, 45...Zena diode, 46...Neon bulb.

Claims (1)

[Claims] 1 The capacitor connected to the gate of the field effect transistor is charged to a predetermined constant level according to the load current caused by conduction of the push button switch, and the field effect transistor is cut off. A thyristor is connected to the gate, and the thyristor is ignited to ignite the triax when the field effect transistor is cut off, and when the push button switch is cut off, the field effect transistor is made conductive by the discharge current of the capacitor, thereby cutting off the thyristor. In a load control circuit configured to cut off a triax at the same time, the first series circuit includes a first resistor having a high resistance value and a first switching element, and a second resistor having a low resistance value and a second switching element. A thyristor is connected in parallel with a second series circuit consisting of a field-effect transistor, and this parallel circuit is connected in series with a field-effect transistor. When the power supply voltage is less than the predetermined level according to the output from the level discrimination circuit, the first switching element is cut off and the second switching element is conductive, and when the power supply voltage is equal to or higher than the predetermined level, the first switching element is turned off. If the element is conductive and the second switching element is cut off, making the load control circuit high impedance, and the field effect transistor is cut off, the second switching element becomes conductive and the thyristor is turned off when the power supply voltage is below the predetermined level. A load control circuit characterized in that it energizes a load by igniting a triac and conducting a triac.