JPH066514Y2 - Light emitting diode drive circuit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a drive circuit for a pair of light emitting diodes.

2. Description of the Related Art In order to operate a two-color light emitting diode with high brightness, 2
Due to the life of the color light emitting diode, it is usually used in static lighting.

FIG. 4 shows a conventional driving circuit for a two-color light emitting diode. The two-color light emitting diode L5 is a light emitting diode L5.
5 ₁ of the cathode side and the light-emitting diode L5 ₂ an anode side structure and the common terminal, the anode side of the two-color light-emitting diode L5 is connected to the positive power source V ₂ through PNP transistor Tr6, 2-color light emitting diode L5 cathode Is a negative power supply V through the NPN transistor Tr7.
Connected to ₃ .

The control circuits 2 and 3 arbitrarily control conduction / interruption of the transistors Tr6 and Tr7.

When driving the two-color light-emitting diodes L5, if the blocking transistor Tr7 to conduct the transistor Tr6, the light-emitting diode L5 ₁ is lit, the transistor Tr
If conduct Blocked transistor Tr7 6, light-emitting diode L5 ₂ is turned.

Problems to be Solved by the Invention Thus, in order to drive the two-color light emitting diode L5, the integrated circuits 2 and 3 for controlling the transistors Tr6 and Tr7 and the power supply for driving the integrated circuits 2 and 3 are used. 2 are required, that is, the positive power source V ₂ and the negative power source V ₃ are required as the current supply power source.

Therefore, when a plurality of the two-color light-emitting diodes L5 are combined to form a display device or the like, and are individually driven to be driven, one driving circuit requires two integrated circuits and four power sources, which complicates the structure. It became expensive as well.

An object of the present invention is to provide a driving circuit of a light emitting diode whose structure is remarkably simplified.

Means for Solving the Problems The present invention provides a pair of light emitting diodes having a cathode side of one light emitting diode and an anode side of the other light emitting diode as a common terminal, and each light emitting diode of the pair of light emitting diodes. And a push-pull circuit constituted by connecting a transistor of the first conductivity type and a transistor of the second conductivity type in parallel to each other.

Operation According to the present invention, by forming a push-pull circuit for controlling lighting of the two-color light emitting diode, one power supply for current supply is sufficient. In other words, conventionally, two power supplies, a positive power supply and a negative power supply, were required as power supplies for current supply, but a drive circuit for a two-color light emitting diode can be configured with a single power supply.

Embodiment FIG. 1 is an electric circuit diagram showing an embodiment of the present invention.
Two-color light emitting diode L1 which is a pair of light emitting diodes
Is connected to a power supply V ₁ through a PNP (first conductivity type) transistor Tr1 on the anode side and an NPN (second conductivity type) transistor Tr2 on the cathode side. The integrated circuit 1 is connected to the base of the transistor Tr2, and the connector of the transistor Tr2 is connected to the base of the transistor Tr1. NPN transistor Tr3 in parallel with the light emitting diodes L1 _1, PNP transistor Tr4 is connected in parallel to the light-emitting diodes L1 _2, to operate the transistors Tr3 and Tr4 are alternately, NPN transistor Tr5 is connected . The transistors Tr3 to Tr5 form a push-pull circuit.

Next, the operation principle will be described. When the high level output signal B from the integrated circuit 1 is input to the base of the NPN transistor Tr2, the transistor Tr2 becomes conductive. At this time, the collector of the transistor Tr2 becomes low level, the base of the PNP transistor Tr1 also becomes low level, and the transistor Tr1 also becomes conductive. Here, when the control signal A is input to the base of the NPN transistor Tr5, the transistor Tr5 becomes conductive and the collector becomes low level. Therefore, the base of the NPN transistor Tr3 and the base of the PNP transistor Tr4 both become low level, the transistor Tr3 is cut off, and the transistor Tr4 becomes conductive, so that the light emitting diode L1 ₁
Lights up.

Further, when the control signal A is not input to the base of the transistor Tr5, the transistor Tr5 is turned off,
The collector goes high. Therefore, the base of the transistor Tr3 and the base of the transistor Tr4 both become high level, the transistor Tr3 becomes conductive, and the transistor Tr4 becomes cut off. Therefore, the light emitting diode L
1 ₂ is turned on.

FIG. 2 is a timing chart when the two-color light emitting diode is turned on. When the control signal A to transistor Tr5 is inputted, the output signal from the transistor Tr2 is input, when the light-emitting diode L1 ₁ lights, control signal A is not input, the output from the integrated circuit 1 When the signal B is input, the light emitting diode L1 ₂ is turned.

Therefore, if a driving circuit as shown in FIG. 1 is used, one integrated circuit (integrated circuit 1) and two power sources (power source V ₁
And a power supply for the integrated circuit 1), a two-color light emitting diode L1
Lighting can be controlled. When the power source V ₁ and the integrated circuit power source can be used at the same voltage, the power source V ₁
Also, the power source for the integrated circuit can be shared and one power source can be omitted. In this case, only one power source is required.

In general, a light emitting diode device configured by arranging a plurality of two-color light emitting diodes is configured by arranging a large number of unit units such as 8 × 8 or 16 × 16 for displaying characters and figures. Since the number of two-color light emitting diodes used in such a display device ranges from several hundreds to several thousands, the effect of simplifying the driving circuit is extremely large.

Further, as shown in FIG. 3, four two-color light emitting diodes L
Even when 1, L2, L3, and L4 are connected in parallel, the same electric circuit can be applied by increasing the number of output terminals of the integrated circuit 1.

As described above, according to the present invention, a transistor is connected in parallel to each light emitting diode of a pair of light emitting diodes, and each transistor is operated alternately, so that a pair of light emitting diodes can be operated with a single power source. Can be turned on. This allows the structure to be miniaturized.

[Brief description of drawings]

FIG. 1 is a drive circuit diagram showing an embodiment of the present invention, FIG. 2 is a timing chart when a two-color light emitting diode is turned on, and FIG.
FIG. 4 is a drive circuit diagram showing an application example of the present invention, and FIG. 4 is a drive circuit diagram of a conventional two-color light emitting diode. L1 ... Two-color light emitting diode, L1 ₁ , L1 ₂ ... Light emitting diode, Tr1, Tr2, Tr3, Tr4, Tr5
...... Transistor, V ₁ …… Power supply

Claims (1)

[Scope of utility model registration request] 1. A pair of light emitting diodes having a cathode side of one of the light emitting diodes and an anode side of the other light emitting diode as a common terminal, and a first conductive member connected in parallel to each of the light emitting diodes of the pair of light emitting diodes. Drive circuit of a light emitting diode, comprising a push-pull circuit formed by connecting a transistor of the second type and a transistor of the second conductivity type.