JP2003009382A - Drive circuit of semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit for driving a light-emitting diode, a semiconductor laser, an electronic apparatus, a control apparatus, and the like, in which unwanted noise is not generated, even if power is turned on/off. SOLUTION: When at least one semiconductor light-emitting element 18 is driven by a DC voltage formed from an AC step-down power supply, the drive circuit 10 connects a current limit element 12 and a temperature-sensitive switch 16 thermally coupled with the current limit element 12, in series with the semiconductor light-emitting element 18. The current limit element 12 detects increase in an unwanted current flowing through the semiconductor light-emitting element 18 and the temperature-sensitive switch 16 interrupts the current flowing through the semiconductor light-emitting element 18. It is also detected by a semiconductor light-emitting element 21 for displaying failure connected with the temperature-sensitive switch 16, constituted of a temperature fuse with a switch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit for a light emitting diode, a semiconductor light emitting device such as a semiconductor laser, an electronic device, a control device or the like which does not use a switching power supply, a power transformer or the like which generates noise. .

[0002]

2. Description of the Related Art A power supply transformer or a switching power supply is used to drive a load, for example, a semiconductor light emitting element such as a light emitting diode or a semiconductor laser, or an electronic device or a control device by using a commercial power supply (AC100V). Then, the voltage is lowered to a necessary voltage suitable for the load.

However, when the power supply transformer is used, if the commercial power supply is turned off during its operation, magnetic flux energy is released to generate a pulsed high voltage,
It becomes a noise source. Further, the switching power supply performs high-frequency pulse duty control or pulse width control to generate a desired voltage. However, since the high-frequency pulse is used, high-frequency electromagnetic waves and electrostatic energy are emitted. However, it may adversely affect the precision instruments and electronic devices placed in the vicinity such as malfunction.

In particular, when a large number of switching power supplies are operated in parallel through the commercial power supply, other devices are adversely affected, and in the worst case, the power factor of the commercial power supply is lowered and the power of the transformer in the cubicle is reduced. It also causes fever.

FIG. 4 shows a conventional drive circuit 40 for driving at least one light emitting diode (LED).

That is, the drive circuit 40 is a commercial power supply AC.
A noise filter 41 connected to 100 V, a switching power supply 42 connected to the noise filter 41,
Current limiting resistor 43 connected to the switching power supply 42
And a plurality of LEDs 44 connected in series to the current limiting resistor 43 and serving as a load.

Since the switching power supply 42 is also used in the drive circuit 40 as described above, as described above, electromagnetic waves and electrostatic energy in a high band are emitted,
This may adversely affect the precision equipment and electronic equipment arranged in the vicinity such as malfunction.

[0008]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a light emitting diode, a semiconductor laser, an electronic device, a control device or the like which does not generate undesired noise even when the power is turned on / off. It is to provide a driving circuit for driving.

Another object of the present invention is to provide a drive circuit having a function of detecting a failure of a semiconductor light emitting element such as a light emitting diode or a semiconductor laser which does not generate undesired noise by using only passive elements. To do.

[0010]

A drive circuit according to the present invention forms a direct current voltage from a stepped down alternating current power supply, and drives a load by the direct current voltage, the current limiting element and the current limiting element are thermally coupled. The temperature sensitive switch is connected in series with the load, and an undesired increase in current flowing through the load is sensed by the current limiting element, and the load current is cut off by the temperature sensitive switch.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The drive circuit according to the present invention forms a direct current voltage from a stepped down alternating current power supply, and drives at least one semiconductor light emitting device by the direct current voltage, the current limiting device and the current limiting device. A temperature-sensitive switch thermally coupled to the semiconductor light-emitting element is connected in series, and an undesired increase in current flowing through the semiconductor light-emitting element is detected by the current limiting element, and the temperature-sensitive switch flows through the semiconductor light-emitting element. It is configured to cut off an electric current and sense it by a semiconductor light emitting element for failure display connected to the temperature sensitive switch. As the temperature sensitive switch, a temperature fuse with a switch is used.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a noiseless driving circuit 10 having a plurality of light emitting diodes (LEDs) connected in series as a load according to an embodiment of the present invention.

The drive circuit 10 includes a rectifier circuit 11 connected to an AC power supply whose voltage is reduced to 5 to 100 V, and a current limiting element 12 such as a fixed resistor connected to the rectifier circuit 11.
A smoothing capacitor 13 connected to the current limiting element 12, a first fixed contact and a second fixed contact and a third fixed contact which are thermally coupled to the current limiting element 12 and are connected in series and have a movable contact piece. A temperature fuse with switch 16 including a switch unit 14 having a switch and a temperature fuse unit 15, an LED drive unit 17 connected to the temperature fuse with switch 16 and formed of a constant current circuit or a constant voltage circuit, and the drive unit 17 Connected to a plurality of LEDs 18 connected in series
A load part 19 and a third part of the switch part 14.
And a resistor 20 for current limitation connected to the fixed contact and a diode or LED 21 connected to the resistor 20.

Next, the operation of the drive circuit 10 will be described. The AC voltage dropped to a desired voltage is rectified by the rectifier circuit 11 and a direct current is passed through the smoothing capacitor 13 connected to the current limiting element 12. Converted to voltage. This DC voltage is applied to the LED 18 of the load unit 19 through the movable contact and temperature fuse unit 15 connected between the first and second fixed contacts of the switch unit 14 and the drive unit 17. It

When one or more of the LEDs 18 malfunctions, that is, becomes short-circuited, the current flowing through the current limiting element 12 increases, and the temperature fuse with a switch thermally coupled thereto, that is, The temperature fuse unit 15 of the switch 16 linked to the fuse reaches the set temperature and is opened (broken), so that the movable contact piece is instantly switched from the second fixed contact to the third fixed contact. Therefore,
Confirming that the current flowing through the load portion 19 is cut off and protected, and that the current flows through the resistor 20 to the diode 21 for failure notification and lights up, and that the current flowing through the load portion 19 is cut off. You can

FIG. 2 shows a modification of the drive circuit 10 shown in FIG. That is, in FIG. 1, the interruption of the load current is confirmed by turning on the LED 21 connected to the resistor 20, but as the LED 21, one of the LEDs 18 of the load section 19 is used at the end side. There is. In this case, it is also possible to use a plurality on the terminal side.

FIG. 3 shows the temperature fuse 16 with the switch.
2 shows a state in which is thermally coupled to the current limiting element 12. That is, when the thermal fuse with switch 16 is closely attached to the current limiting element 12, the thermal fuse 16 and the switch are bonded by using a compound 31 having good thermal conductivity such as a silicone compound, and a space is provided between the two depending on conditions. When provided, they are connected using a spacer or the like.

In the above embodiment, the temperature fuse with the switch is used as the temperature sensitive switch thermally coupled to the current limiting element, but a thermal switch, a circuit protector or the like can be used instead of the temperature fuse with the switch.

Further, a plurality of LEDs connected in series used as a load can be used as an electric decoration for a Christmas tree or the like, and a detection LED is turned on when the LED fails, thereby providing a safer lighting device. Can also be provided.

Further, as the current limiting element, a resistor,
It is also possible to use a constant current diode or a constant current circuit using a semiconductor element.

[0021]

The drive circuit according to the present invention is formed by only the rectifier, the smoothing capacitor, and the passive elements such as the current limiting element,
Since no power transformer or switching power supply is used, no undesired noise is generated. Further, when a plurality of LEDs connected in series are used as the load, the detection LED is turned on when the LED fails, and a safer lighting device is obtained.

[Brief description of drawings]

FIG. 1 illustrates a driving circuit having a plurality of light emitting diodes (LEDs) connected in series as a load according to an exemplary embodiment of the present invention.

FIG. 2 is a diagram showing a modification of the drive circuit in FIG.

FIG. 3 is a perspective view showing a state in which a thermal fuse with a switch is thermally coupled to a current limiting element according to an embodiment of the present invention.

FIG. 4 is a diagram showing a conventional drive circuit for driving a light emitting diode (LED).

[Explanation of symbols]

10 ... Drive circuit, 11 ... Rectifier circuit, 12 ... Current limiting element, 13 ... Smoothing capacitor, 14 ... Switch part, 15 ...
Thermal fuse part, 16 ... Thermal fuse with switch, 17
... LED drive section, 18 ... LED, 19 ... Load section, 20 ...
Resistor, 21 ... LED, 31 ... Compound

Claims (5)

[Claims] 1. A drive circuit for forming a DC voltage from a stepped-down AC power supply and driving a load by the DC voltage, wherein a current limiting element and a temperature-sensitive switch thermally coupled to the current limiting element are connected to the load. A drive circuit connected in series, wherein an undesired increase in current flowing through the load is sensed by the current limiting element and the load current is shut off by the temperature sensitive switch. 2. The drive circuit according to claim 1, wherein a failure notification circuit is connected to the temperature sensitive switch. 3. The drive circuit according to claim 1, wherein the load is a semiconductor light emitting element or a semiconductor laser. 4. A drive circuit for forming a direct current voltage from a stepped down alternating current power supply and driving at least one semiconductor light emitting device by the direct current voltage, wherein a current limiting element and a temperature-sensitive switch thermally coupled to the current limiting element. Is connected in series with the semiconductor light emitting element, and an undesired increase in current flowing through the semiconductor light emitting element is sensed by the current limiting element, and the current flowing through the semiconductor light emitting element is cut off by the temperature sensitive switch. A drive circuit characterized in that the interruption of the current is notified by an optical semiconductor element for failure notification connected to a temperature switch. 5. The drive circuit according to claim 4, wherein the temperature sensitive switch is a switch interlocking with a fuse.