JPS6017029Y2 - Light emitting diode drive device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a so-called two-color light emitting diode driving device using two light emitting diodes with different forward voltages.
The object of this invention is to switch and light up the two light emitting diodes with a simple configuration.

2. Description of the Related Art Generally, tape recorders and the like are known to display recording status, playback status, etc. using two light emitting diodes with different forward voltages.

However, all of these types require a switch with one circuit and two contacts, as shown in FIG. 1, and are not very desirable.

That is, in FIG. 1, when the power switch 11 is turned on, the N-gate thyristor 2 is turned on by the action of the capacitor 6 at that moment, and the voltage from the power supply 12 is applied to the diode 1,
The signal is applied to the base of the transistor 8 via the thyristor 2 and the resistor 3, and acts to turn on the transistor 8.

In this state, if the 1-circuit, 2-contact selector switch 10 is now connected to the recording side terminal R, the bias oscillation circuit 9 is activated, the transistor 8 is activated, and the resistor 1 is turned on.
A current flows through the first light emitting diode 16 through the first light emitting diode 16, and the first light emitting diode 16 lights up.

If the changeover switch 10 with 1 circuit and 2 contacts is turned on to the reproduction side terminal P, the transistor 8 is turned on in the same way, and current flows to the second light emitting diode 17 via the resistor 13. Light.

In addition, in the light emitting diode drive circuit shown in FIG. 1, when the voltage of the power source 1.2 falls below a certain set voltage, the thyristor 2 is turned off, the transistor 8 is turned off, and none of the light emitting diodes 16 and 17 light up. .

That is, the thyristor 2, the transistor 8, etc. operate as a drive circuit for checking the power supply voltage.

In this way, the recording status and playback status can also be indicated by lighting different LEDs in the LED drive circuit shown in Figure 1, but in this case, a changeover switch with two contacts per circuit is always required. It was not possible to use a simple switch with one circuit and one contact.

This proposal eliminates the above-mentioned drawbacks of the conventional technology.1
The circuit is configured to easily and accurately switch on and off the light emitting diodes using a switch at one contact point of the circuit.

Hereinafter, the light emitting diode switching device of the present invention will be described with reference to drawings of embodiments.

FIG. 2 is an electrical wiring diagram of one embodiment of the light emitting diode drive device of the present invention, in which 11 is a power switch;
2 is a power source, 15 is a two-color light emitting diode, 16 is one light emitting diode constituting the two color light emitting diode 15, which has a small forward current and emits red light, for example, and 17 is a diode that constitutes the two color light emitting diode 15. The other light-emitting diode is a diode that emits light in green, for example, when a forward current is applied; 18 is a switch with one circuit and one contact; 19, 25 are diodes; 22, 27, 31, 33 are transistors; 20, 21, 23; , 28, 29, 30.
32 is a resistance.

In the above embodiment, when the power switch 11 is turned on, a predetermined bias is applied to the base of the transistor 27 via the resistor 21, the transistor 27 enters a predetermined operating state, and the preset 2VB is applied to the base of the transistor 33.
A bias of E (where VBE is the pace-emitter voltage of the transistor) is applied.

Therefore, in this state, the transistor 33 turns on and the light emitting diode 17 lights up.

By the way, in this case, transistors 22, 24, 26 and resistors 19, 25, 20, 21, 23 constitute a constant current circuit, and transistors 31 and 33 also constitute a constant current circuit, so that the current flows to transistor 33. The current, that is, the current flowing through the light emitting diode 17 is VBE/R3
It will be a constant value determined by ゜.

In this case, since the voltage-current characteristics of the light emitting diode 17 are as shown in FIG.
The voltage across the terminal 7 is Vpl.

Next, if the switch 18 with one circuit and one contact is turned on, the light emitting diodes 16 and 17 will be connected in parallel, and the Tl current flowing through the transistor 33 will be shunted to both transistors 16 and 17. .

Then, the voltage across the light-emitting diodes 16 and 17 decreases to VF2 in FIG. 3, and almost no current flows through the light-emitting diode 17 and only through the light-emitting diode 16.

Therefore, in this case, the light emitting diode 16 lights up,
The light emitting diode 17 is turned off.

In this way, according to the embodiment described above, it is possible to easily and accurately switch and light up two light emitting diodes using a switch having one circuit and one contact.

In addition, in FIG. 2, the circuit consisting of transistors 19, 25, transistors 22, 24, 26, 27, etc.
When the voltage of 16 and 17 falls below a preset value, the base bias of transistor 33 is extremely reduced, turning off transistor 33 and switching off both light emitting diodes 16 and 17.
It has the effect of turning off the light.

That is, the above circuit is provided to provide a function of checking the power supply voltage.

As is clear from the examples above, according to the light emitting diode drive device of the present invention, two light emitting diodes can be switched and lit accurately and reliably using a switch with one circuit and one contact, and the overall circuit configuration is simple. This is extremely advantageous in practice.

[Brief explanation of the drawing]

Fig. 1 is an electrical wiring diagram of a conventional light emitting diode driving device, Fig. 2 is an electrical wiring diagram of an embodiment of the light emitting diode driving device of the present invention, and Fig. 3 is a voltage and current diagram of a light emitting diode used in the device. This is a characteristic diagram. 11...Power switch, 12...Power supply, 15...Two-color light emitting diode, 16,17.
...Light emitting diode, 18...1 circuit 1
Contact, 31.33...Transistor that constitutes a constant current source.

Claims (1)

[Scope of utility model registration request] One electrode of each of two light emitting diodes having different forward voltages is connected to each other and connected to a constant current source, and a switch is connected between the other electrode of each of the two light emitting diodes. A light emitting diode drive device consisting of a terminal connected to a power source.