JPS6126270A - Light emitting device - Google Patents

Abstract

PURPOSE:To contrive to reduce the consumed power by a method wherein an inductance is connected in parallel with a light emitting element, so that current may flow through the light emitting element immediately after a switching element changes from ON to OFF. CONSTITUTION:The inductance L is connected is parallel with the LED between a DC power source VCC and the switching element Tr. Therefore, when a rectangular signal Vin is impressed on the base of the element Tr, a current I1 flows through the inductance L only for a given time, and a current I2 flows through the LED after the element Tr turns off. Such a construction can make the consumed power much smaller than by the device provided with a resistor instead of an inductance between the power source and the LED.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a light emitting device with reduced power consumption that is driven only for a predetermined period of time by a rectangular wave signal.

Problems to be solved by the conventional technology and invention Optical encoders are widely used to detect the rotation speed and rotation angle of servo motors, etc. A rotating rotating slit plate, a light emitting device provided on one side of the rotating slit plate, a fixed slit facing the light emitting device and provided on the other side of the rotating slit plate, and receiving an optical signal of the light emitting device obtained from the fixed slit. It is equipped with two light receiving devices, one for the human phase and one for the B phase.

In such encoders, the light emitting device is normally driven continuously, but recently, the applicant has developed a device that reduces power consumption by driving the light emitting device only for a predetermined period of time using a square wave signal. (Reference: Japanese Patent Application 1987-
No. 73872).

FIG. 3 shows a conventional light emitting device. In FIG. 3, a resistor R1, a light emitting diode LED, and a transistor Tr are connected in series between a DC power supply vec and a ground line. The transistor Tr is turned on by the rectangular wave signal (2) generated by the rectangular wave generating circuit GTR. Tsuma-taku, 4th
As shown in FIG. 4(5), when the rectangular wave signal vin changes, the rectangular wave current I shown in FIG. 4(B) also flows through the light emitting diode LED, causing the light emitting diode LED to light up.

However, in the conventional type described above, the power consumption is still insufficiently reduced due to the presence of the resistor R.
When a battery is used as a power source for a light emitting device, there is a problem in that the battery consumes a lot of energy.

Means for Solving the Invention In view of the above-mentioned problems, an object of the present invention is to provide a light emitting device with even lower power consumption;
1st. a second power terminal means, an inductance connected to the first power terminal means;
a switching element connected between the power supply terminal means of the
connected in parallel to the inductance; A light emitting element having a conduction direction opposite to the voltage application direction of the second power supply terminal means, and a rectangular wave signal generating means for generating a rectangular wave signal to the switching element to turn on the switching element. achieved by the device.

Operation According to the above configuration, current flows through the inductance when the switching element is on, and current flows through the light emitting element immediately after the switching element changes from on to off.

Example Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a light emitting device according to the present invention. In FIG. 1, in place of the resistor R in FIG. 3, an inductance L is connected in parallel to a light emitting diode LED. Therefore, as shown in the second part, the square wave signal ■,
is applied to the pace of the transistor Tr, the current 1. is applied for a time T' as shown in FIG. flows through the inductance L. After the transistor Tr is turned off, a current of 1. will flow.

The light emitting device shown in FIG. 3 and the light emitting device shown in FIG. 1 will be compared and explained. Electrical work using the device shown in Figure 1! (or 1.) If the peak value of ...
... Matches when (1). At this time,
The area of the shaded portion in FIG. 4(B) matches the area of the shaded portion in FIG. 2). On the other hand, in the apparatus shown in FIG. 1, TdXV,=I. XL -...- (2) However, ■ is the forward voltage of the light emitting diode LEDO, and furthermore, the current value ■. is given by. Therefore, (
1), (2), (3) Expressions are tonal. For example, vcc = 5V + V, = IV
Therefore, referring to FIG. 2(B), the power consumption cover per pulse of the transistor Tr in FIG. 1 is -! −
r□xx = Incense T X I.

Furthermore, the power consumption is significantly lower than that of the device shown in FIG. 3. As described above, the light emitting device shown in FIG. 1 has the effect of significantly reducing power consumption.

Figure 5 shows an optical encoder to which the light emitting device of Figure 1 is applied! FIG. In FIG. 5, reference numeral 1 denotes the output shaft of a motor or a rotating shaft that rotates in synchronization with the output shaft of the motor, and at its tip, a plurality of slits 2a are arranged at a constant pitch as shown in FIG. A pickpocket board 2 is provided.

Further, a substrate 3 is provided on one side of the rotary pickpocket plate 2, and a light emitting device 4 according to the present invention is provided on the substrate 3.

On the other side of the rotary pickpocket plate 2, a fixed pickpocket plate 5 as shown in FIG. 7 is provided. This fixed slit plate 5
Two types of slit groups 5A and 5B are formed, and the phase difference between these slit groups 5A and 5B is 90° depending on the slit pitch of the rotating slit plate 2. The optical signals obtained via the merit groups 5A and 5B are received by two light emitting devices, such as photodiodes 6.7. These two types of optical signals are called phase phase signals and phase B signals, and their phases are shifted by 90 degrees. Furthermore, a circuit section 8 and a battery 9, which will be described later, are provided on the substrate 4.

FIG. 8 is a detailed block circuit diagram of the circuit section 8 of FIG. In FIG. 8, the clock generation circuit 801 is
It corresponds to the rectangular wave generating circuit GTR shown in the figure, and generates the rectangular wave signal S shown in FIG. 9(,). This rectangular wave signal S is supplied to the base of the transistor Tr of the light emitting device 4. 8
02.803 is an amplifier circuit that amplifies the signal of the photodiode 6.7; 804 is a monostable multivibrator that generates a pulse signal S2 in response to the falling edge of the rectangular wave signal S;
05 indicates the operation timing of the light emitting device 4 and the photodiode 6
, 7. This is a delay circuit that delays the Noyals signal S2 by the difference from the operation timing of . Output 4 of delay circuit 804
The pulse signal S3 acts as a clock signal for the D flips 74, 806, 807, 808, and 809 as latch circuits, and also acts as a clock signal for the up/down counter 813.

For example, if a human phase signal and a B-phase signal are obtained when using a continuous light source as shown in FIG.
．． The outputs SA and SB of 803 are shown in FIG. 9(d).

It changes as shown in (f). Therefore, the pulse signal S3 is used to drive the D flip-flops 806 and 807.

The respective outputs SAI and SBI are shown in Figure 9(g).

The signal becomes a rectangular wave signal as shown in (i). Tsume D, A phase signal.

This means that a B-phase signal has been formed. Subsequently, the outputs SAI of D flip-flops 806 and 807 are output.

SBI is latched by the D flip-flops 7'808 and 809 of the next stage by the pulse signal S3. t), Figure 9 (
h), as shown in (j), D-Furi, Pflo, f8
08.809 output SA2, SB2 is the output S of the previous stage
It is delayed by one clock pulse with respect to AI and SBI.

D flip-flop mentioned above, 7"806,808°807.
809 output SAI, SA2, SBI, S
B2 is each terminal A of the decoder 810. (=2°') l
A, (=2').

A2 (=22), A, (=23) are supplied.

This decoder 810 has terminal A. , A4. A2. Convert the 2 communication signals received at A into decimal numbers O to 15 2
This is a decimal/decimal conversion circuit. Therefore, the signal 8A1,
When SA2, 881°SB2 changes as shown in FIG. 9(X) to (j), the value of the decoder 810 changes to FIG.
), it changes like a river: "1#→'3"→"7#→"15"→

As a result, the output SU of the OR circuit 811 connected to the outputs 1.7 and 8°14 of the decoder 810 becomes a rectangular wave signal as shown in FIG. The output SD of the OR circuit 812 connected to 4, 11, and 13 is held at a low level as shown in FIG. , signal SD is up/
Since it acts as a down signal for the down counter 813, the up/down counter 813 counts up the negative signal S3 and counts up +1, +2, +3, +4, . . . .

In FIG. 9, it is assumed that the rotary pickpocket and the top plate 2 rotate in the normal direction, for example. Therefore, when the rotating slit plate 2 rotates in the opposite direction, the D flip-flops 806 to
809, the checked signals are SBI, SB2. SAI,
The values of the decoder 810 change in the order of SA2, and as a result, the value of the decoder 810 is '41 → '12# → '13# → '15# → '11' →
``3#→...changes as follows.On the other hand, in this case,
The signal 8U is held at a low level, and the signal SD is a square wave signal.As a result, the up/down counter 813 counts the pulse signal S, -1, -2, -3, -4,
...and a countdown. In this way, the forward and reverse rotation of the multi-rotation slit plate 2 is determined by the frizzoflo f806 to 809, the DE=y-da 8101, and the OR circuit 811.
The rotation speed and angle are up/down counter 81.
It is stored in 2.

The encoder shown in Fig. 8 is applied when the rotary slit plate 2 rotates at a constant speed, but when the rotation speed of the rotary slit plate 2 changes, the clock is changed according to the rotation speed. The configuration may be such that the signal speed of the generating circuit 801 is changed.

As described in detail, according to the light emitting device of the present invention, power consumption can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a light emitting device according to the present invention, FIG. 2 is a timing diagram explaining the circuit operation of FIG. 1,
FIG. 3 is a circuit diagram showing a conventional light emitting device, FIG. 4 is a timing diagram explaining the circuit operation of FIG. 3, and FIG. 5 is an overall diagram of an optical encoder to which the light emitting device according to the present invention is applied. A schematic diagram, Figure 6 is a front view of the rotating slit plate in Figure 5, and Figure 7 is a front view of the rotating slit plate in Figure 5.
5 is a front view of the fixed slit shown in FIG. 5, FIG. 8 is a circuit diagram of the circuit section shown in FIG. 5, and FIG. 9 is a timing chart explaining the operation of the circuit shown in FIG. 8. L: Inductance Tr: Switching element LED: Light emitting strip GTR: Square wave signal generation means

Claims (1)

[Claims] 1, first and second power terminal means, an inductance connected to the first power terminal means, a switching element connected between the inductance and the second power terminal means, and a switching element connected in parallel to the inductance. The first and second
A light emitting device comprising: a light emitting element having a conduction direction opposite to the voltage application direction of the power terminal means; and a rectangular wave signal generating means for generating a rectangular wave signal to the switching element to turn on the switching element.