JPH0358119B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for driving a light emitting element attached to an electronic circuit.

BACKGROUND ART Conventionally, light emitting elements such as LEDs have been added to various electronic circuits for alarm display, data display, etc.

Conventionally, a method as shown in FIG. 1 has been used to drive this light emitting element. In FIG. 1, a high power supply voltage applied to a terminal 1 is divided by voltage dividing resistors 2 and 3, further made into a constant voltage by a drop-down transistor 4, and then dropped to a power supply terminal 6 of an electronic circuit 5. can be added. When the signal of the display signal output IC 7 in the circuit 5 becomes high (H) level, the light emitting element driving transistor 10 of the display circuit 9 is turned on through the current limiting resistor 8, and current flows to the light emitting element 11 through the current limiting resistor 12. 11 lights up.

As described above, since the current for driving the light emitting element uses the current supplied to the electronic circuit 5, the I _DD consumed by the entire circuit is reduced when the light emitting element is ON.
Current consumption I _D + current consumption I _L of display circuit 9 becomes I _D
increases by I _L , which is constant.

When the number of light emitting elements is large, the change in I _DD becomes large, which not only increases power consumption but also
The current flowing through the drop-down transistor 4 also increases, resulting in more heat generation, and the power supply voltage supplied to the drop-down transistor 6 fluctuates.

In order to solve these drawbacks, the present invention supplies a high voltage source for driving which flows when the light emitting element is turned on, and further utilizes this current for driving the electronic circuit.
This was an attempt to reduce overall power consumption.
The drawings will be explained in detail below.

FIG. 2 shows an embodiment of the present invention, in which 1 is a high power supply voltage supply terminal, 2 and 3 are voltage dividing resistors, 4 is a drop-down transistor, 5 is an electronic circuit, and 5 is a power supply terminal for the electronic circuit 5. , 7 outputs the display signal
IC, 11 is a light emitting element, 12 is a current limiting resistor, 1
3 is a FET switch that turns on and off the light emitting element, 1
4 is a display circuit.

The high power supply voltage applied to terminal 1 is connected to voltage dividing resistor 2,
3 and drop-down transistor 4 to a voltage suitable for electronic circuit 5 and applied to terminal 6 to drive 5.

Here, when the display signal is output from 7 and the FET switch 13 is turned on, current flows from the terminal 1 through the current limiting resistor 12 to the light emitting element 11, and the light emitting element lights up. By using this light emitting element driving current together with the current supplied from the drop-down transistor as a current for driving the electronic circuit 5, the power consumption of the entire circuit can be reduced.

That is, if the current supplied from the drop-down transistor 4 is I ₁ , the current consumed by the current circuit 5 is I ₂ , and the light emitting element drive current is I ₃ , then when the light emitting element is off, I ₂ = I ₁ (1) Light emission When the element is lit, I ₂ = I ₁ + I ₃ (2), and since I ₂ is almost equal in (1) and (2), (in the case of (2)
(I ₁ decreases) When the light emitting element is turned on, I ₁ is smaller than when it is turned off by about I ₃ .

Assuming that the current I ₄ flowing into the transistor 4 is almost equal to I ₁ and the current flowing through the voltage dividing resistor 2 is constant, the current I ₆ flowing from the terminal 1 is I ₆ = I ₅ + I ₄ ≒ I ₅ when the light emitting element is turned off. +I ₁ ≒ I ₅ + I ₂ When lit, I ₆ = I ₅ + I ₄ + I ₃ ≒ I ₅ + I ₁ + I ₃ = I ₅ + I ₂ , and does not increase even if the light emitting element is lit.

As explained above, the current for driving the light emitting elements is supplied from a high voltage power supply, and this is further used to drive the electronic circuits except for the display circuit, so the power consumption of the entire circuit can be reduced. .

This is particularly effective in circuits that use a large number of light emitting elements, because the current that can be used to drive the electronic circuit is large.

Furthermore, contrary to the conventional method, the current supplied from the drop-down transistor is reduced by the amount of drive current when driving the light emitting element, so the amount of electric power that is converted into heat by the drop-down transistor can also be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional driving method, and FIG. 2 is a diagram showing a method of the present invention. In the figure, 1 is a high power supply voltage supply terminal, 2 and 3 are voltage dividing resistors, 4 is a drop-down transistor, 5 is an electronic circuit, 6 is a power supply terminal for the electronic circuit 5, 7 is an IC that outputs a display signal, 11 is a light emitting element, 12 is a current limiting resistor, and 13 is for turning on and off the light emitting element.
FET switch 14 is a display circuit.

Claims (1)

[Claims] 1. In a method for driving a light-emitting element, in which the light-emitting element is controlled to be turned on and off by the output of an electronic circuit in which the voltage of a power source is divided by a voltage dividing circuit and supplied, the light-emitting element is connected to the input side of the electronic circuit. In,
A method for driving a light-emitting element, characterized in that the light-emitting element is connected in parallel to the voltage dividing circuit, and a current that flows when the light-emitting element is turned on is supplied from a power source.