JPS62246292A - Lighting apparatus - 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] [Technical field to which the invention pertains] The present invention relates to an improvement in a lighting device that uses a high-frequency inverter circuit to light up a lighting load such as a halogen light bulb, and in particular, the present invention relates to an improvement in a lighting device that uses a high-frequency inverter circuit to light up a lighting load such as a halogen light bulb. This is to prevent the lifespan from being shortened.

[Prior art and its problems]

Conventionally, for example, when trying to light a halogen bulb with a rated lighting voltage of 12V using a commercial AC power supply, W4! ls
The lights were turned on by lowering the commercial power supply voltage using a so-called iron-coupled transformer. However,
Iron/coupled transformers have the disadvantage of being large in size and weight, making them inconvenient to handle, so recently a high-frequency inverter has been used to convert the commercial power supply to high frequency, and then the high-frequency transformer is used to step down the voltage to around 12V. , so-called electronic transformers have come into use. An example of a typical lighting device using the electronic transformer according to FIG. 4 is shown. In the figure, l is an AC power source, 2 is a full-wave rectifier that rectifies the AC power source, 3 is a sine-wave inverter that converts the output of the full-wave rectifier into a sine-wave high-frequency voltage, 4 is a drive circuit for the sine-wave inverter, and 5 is a sine-wave inverter drive circuit. is a light load, such as a halogen light bulb, connected to the output transformer of a sine wave inverter. The operation of such a lighting device is widely known and partially overlaps with the operation of the device of the present invention, which will be described later, so a description thereof will be omitted here.

By the way, in such a lighting device, when an electric lamp equipped with an incandescent filament such as a halogen lamp is used as the electric lamp load 5, the following problem occurs. That is, when the AC power supply 1 is turned on and a voltage is suddenly applied to the lamp load 5, a sudden rush current is generated through the lamp load because the impedance of the incandescent filament when it is cold is extremely small compared to that when the lamp is lit. However, if the light load frequently blinks, the life of the light load will be significantly shortened.

Furthermore, when the power is turned on, the inductance component of the sine wave inverter generates a high voltage back electromotive force, which may destroy the inverter's transistors, etc.
It is necessary to provide a surge absorption circuit, which makes the device complicated and expensive.

[Purpose of the invention]

In order to solve the above-mentioned problems, the present invention suppresses rush current by gradually increasing the on-off ratio every half cycle from power-on. By adopting the so-called soft start method, the life of the lighting load can be shortened,
This is intended to prevent equipment from becoming more complex and costly.

[Structure and operation of the invention]

FIG. 1 shows an example of a lighting device according to the present invention.

In the figure, l is an AC power supply, 2 is a full-wave rectifier, 3 is a sine wave inverter, 4 is a drive circuit, and 5 is a lighting load, which are connected as shown in the diagram to form a lighting device similar to that shown in Figure 4. It consists of In such a lighting device, the present invention connects a semiconductor switching element 6 such as a transistor in parallel with the drive circuit 4, and controls the on/off and time of this semiconductor switching element 6 by a control circuit 7, and turns on the power. The sine wave inverter is configured to gradually increase the oscillation time of the sine wave inverter for each half cycle of the AC power supply voltage for a certain period of time starting from the time. The control circuit 7 basically includes a charging/discharging capacitor 8 connected to a DC power source,
The thyristor 9 and its trigger element 10 are turned on and off according to the charging and discharging of the capacitor 8, and the semiconductor switching element 6 is turned on and off according to the on and off of the thyristor 9.
A circuit component that sends an off control signal, such as transistor 1
), a diode 12, etc.

Next, the operation of this device will be explained.

First, the circuit operation without considering the operation of the control circuit 7 will be explained as follows. When the AC power supply l is turned on, the AC power supply voltage is rectified by the full-wave rectifier 2 into a DC voltage containing a frequency component having a frequency twice the AC power supply frequency. When this DC voltage is supplied to the inverter 3, for example, if the transistor 16 is turned on first, a voltage is generated in the feedback winding 18 that increases the base current of the transistor 16. However, the transistor 16 remains on.

On the other hand, since no current flows through the base of the transistor 17, it is in an off state. The voltage generated in each winding of the oscillation transformer 19 oscillates due to the leakage inductance of the oscillation transformer 19 and the oscillation capacitor 20. Therefore, after a certain period of time, the polarity of the feedback winding 18 is reversed.
This time, current flows to the base of transistor 17, turning on transistor 17 and turning off transistor 16.

In this way, oscillation begins. At the same time as the oscillation starts, the voltage generated in another feedback winding 21 is rectified by a rectifier circuit composed of a diode 22 and a capacitor 23, and a DC voltage is generated in the capacitor 23. This DC voltage supplies a drive current through resistors 24.14 and 15 to the base of transistor 16.17. This drive current is supplied to completely saturate the transistor that is on, and when this current is cut off, the oscillation of the inverter immediately stops. The control circuit 7 has a function of supplying or cutting off the drive current in synchronization with the AC power cycle, and when the thyristor 9 is off, current flows through the resistor 25 and the diode 12 to the base of the transistor 1). Therefore, the transistor it is turned on, and since no current from the resistor 26 flows through the base of the transistor 6, the transistor 6 is turned off, and the drive current is supplied and the inverter oscillates.

On the other hand, when the thyristor 9 is on, the base current of the transistor 1) is cut off, the transistor 1) is turned off, the base current flows to the transistor 6 through the resistor 26, and the transistor 6 is turned on, so that the drive current is cut off and the oscillation of the inverter stops.

Here, the operation of the lighting device including the operation of the control circuit 7 will be explained as follows.

First, when the AC power supply 1 is turned on, the sine wave inverter 3 starts oscillating, but during a half cycle of the power supply frequency, the capacitor 8 is charged through the resistor 27, capacitor 28, and diode 29, and the charging voltage is applied to the trigger element lO.
When the breakover voltage is exceeded, a signal is applied to the gate of thyristor 9 and thyristor 9 is turned on, so that transistor 6 is turned on and the oscillation of the sine wave inverter in this half cycle is stopped. When moving to the next half cycle, the thyristor 9 is turned off again, so the sine wave inverter 3 starts oscillating. Here capacitor 28
has been charged with a current equivalent to that in the previous half cycle, so from the moment the rectified output voltage exceeds the charging voltage, the resistor 2
Current flows through capacitor 7 and capacitor 8 is charged. In this half cycle, the phase angle exceeding the breakover voltage of the trigger element lO is delayed by the amount that the capacitor 28 was charged in the previous half cycle, so the time during which the sine wave inverter 3 is oscillating is longer than in the previous half cycle. Become. By repeating this operation, the capacitor 28 gradually approaches the peak value of the rectified DC voltage, and the oscillation time of the sine wave inverter 3 correspondingly increases. When the voltage of the capacitor 28 becomes equal to the peak value of the rectified power supply voltage, current no longer flows into the gate circuit of the thyristor 9, and from then on, the thyristor 9 remains off, and the sine wave inverter 3 also oscillates. will continue. FIG. 3 shows voltage waveforms and on/off states of various parts in the circuit of FIG. 1 which operates as described above.

In FIG. 2, the control circuit 7 is replaced with another embodiment. In the control circuit 7 of this device, a pulse transformer 30 is used in the gate circuit of the thyristor 9, and the electric charge of the capacitor 8 for making the trigger element 10 conductive is discharged through the primary side of the pulse transformer 30. The voltage generated on the secondary side of the circuit turns on the thyristor 9, which causes current to flow to the base of the transistor 6 through the resistor 25, thyristor 9, and resistor 26, so the circuit operates in the same way as the circuit shown in Figure 1. It is.

〔Effect of the invention〕

As explained above, the present invention turns on and off the operation control signal of a sine wave inverter in synchronization with the commercial power supply frequency, and gradually changes the on-off ratio of this on-off ratio every half cycle from the time the power is turned on. By increasing the number of LEDs, the rush current at power-on is reduced, so even if the lamp load is blinked quite frequently, the life of the lamp will not be shortened.

In addition, since the so-called soft start method as described above is adopted, the oscillation of the sine wave inverter immediately after power-on starts gradually from immediately after the power supply voltage crosses zero, which prevents the generation of back electromotive force due to inductance components. Since it is not necessary to provide a surge absorption circuit, it is possible to prevent the device from becoming complicated and costly.

[Brief explanation of drawings]

1 and 2 are circuit diagrams of a lighting device according to the present invention, and FIG. 3 shows voltage waveforms and ON/OFF signals at various parts in the circuit of FIG.
FA diagram showing the off state, FIG. 4 is a circuit diagram of a conventional lighting device. In Figures 1 and 2, 1... AC power supply, 2...
- Full wave rectifier, 3... Sine wave inverter, 4... Drive circuit, 5... Light load, 6... Semi-oligomatic switching element, 7... Control circuit.

Claims (2)

[Claims] (1) an alternating current power source, a full wave rectifier that rectifies the alternating current power source, a sine wave inverter that converts the output of the full wave rectifier into a sine wave high frequency voltage, a drive circuit for the sine wave inverter, and the sine wave In a lighting device consisting of a lighting load connected to the output end of an inverter, a semiconductor switching element is connected in parallel with the drive circuit of the sine wave inverter, and a control circuit controls the on/off and time of the semiconductor switching element. A lighting device characterized in that it is configured to gradually increase the oscillation time of the sine wave inverter for each half cycle of the AC power supply voltage for a certain period of time after the AC power supply is turned on. (2) The sine wave inverter is a two-transistor constant current inverter.
The lighting device described in section 1).