JPH0822263A - Led lighting circuit - Google Patents

Abstract

PURPOSE:To provide an LED lighting circuit capable of optionally controlling an output current value without external parts and outside input signals by providing a mirror circuit optionaily multiplying an output current of a voltage/ current conversion circuit and supplying it to an external LED. CONSTITUTION:This circuit is provided with an f-V conversion circuit 3 converting a frequency of an input Iin to a voltage, a V-I conversion cirduit 4 making the output voltage Vf of the f-V conversion circuit 3 a reference voltage, current converting it and outputting a reference current If and a constant current mirror circuit 5 optionally multiplying the reference current If from the V-I conversion circuit 4. Then, the voltage outputted from the f-V conversion circuit 3 becomes the reference current, and the output current optionaliy multiplying the reference current is obtained, and the LED 7 is driven by the output current. Thus, the output value is set freely by supplying an input with an optional frequency without the external parts and outside control signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an L used for driving an LED dot matrix display or the like for lighting an LED.
The present invention relates to an ED lighting circuit.

[0002]

2. Description of the Related Art Heretofore, as an LED lighting circuit of this type, there have been those shown in FIGS. 4, 5 and 6, for example. The configuration and operation will be described below.

FIG. 4 is a diagram showing a conventional LED lighting circuit. FIG. 4 (a) is a configuration diagram thereof, and FIG. 4 (b) is a graph showing a relationship between an external resistance and an output current.

This LED lighting circuit 100 has an input terminal 1
01, an output terminal 102, and an external terminal 103, and an input terminal 101 includes a constant current mirror circuit 104 and a constant current source 1.
The output terminal 102 is connected via 05.

The constant current mirror circuit 104 includes a reference current IF
Is a circuit that outputs a current that is an arbitrary multiple of. On the input side of the constant current mirror circuit 104, a constant voltage circuit 106 for generating a reference voltage VF for obtaining the reference current IF, and between the output side of the constant voltage circuit 106 and the external terminal 103 are provided. The provided constant current source 107 is connected, and an external resistor 108 for current conversion is connected between the external terminal 103 and the ground. The output terminal 102 is the LED 10
A potential power source PS is connected via 9.

For example, data IIN for turning on the LED 109 at the "H" level and turning off the LED 109 at the "L" level is input to the input terminal 101. When the predetermined reference current IF is set when the data IIN is at the "H" level, the output current IOUT that is an arbitrary multiple thereof is output to the output terminal 102. This turns on the LED 109.

According to the LED lighting circuit 100, the value of the output current IOUT can be controlled as shown in FIG. 4B by replacing the external resistor 108 with another value.

However, the LED lighting circuit 100 described above is
The LED 109 is driven at a constant output current value, and the LED 109 is controlled by arbitrarily controlling the output current value.
Can't drive.

Therefore, an LED lighting circuit as shown in FIGS. 5 and 6 is known as an LED lighting circuit capable of arbitrarily controlling the output current value.

FIG. 5 is a diagram showing another conventional LED lighting circuit. FIG. 5 (a) is its configuration diagram, and FIG. 5 (b) is a graph showing the relationship between external resistance and output current. .

The LED lighting circuit 110 is designed to obtain an arbitrary output current value IOUT (effective value) by PWM (pulse width modulation) control, and is different from the LED lighting circuit 100 described above in the input terminal. Input from 101
At the same time that the control circuit 112 that receives the PWM control signal CPWM from the input terminal 111 is provided, and the input side of the constant current mirror circuit 104 is connected to this output side.

According to this LED lighting circuit 110, as shown in FIG.
As shown in (b), the output current value IOUT (effective value) can be arbitrarily changed by the PWM control signal CPWM.

FIG. 6 is a block diagram of another conventional LED lighting circuit.

This LED lighting circuit 120 is the above-mentioned LED.
The difference from the lighting circuit 100 is that between the external terminal 103 and the ground, a plurality of external resistors 108a and a plurality of changeover switches 108b for switching the connection of each external resistor 108a.
Is provided.

According to the LED lighting circuit 120, the plurality of external resistors 108a are connected to the respective changeover switches 108.
The output current value IOUT can be arbitrarily changed by switching with b.

[0016]

However, the above-mentioned conventional LED lighting circuit capable of arbitrarily controlling the output current value has the following problems.

(1) When obtaining an arbitrary output current value (effective value) by PWM control, a control circuit 112 is provided as shown in FIG. 5, and the effective value of the output current is changed arbitrarily by the PWM control signal CPWM. Therefore, the circuit configuration is complicated and the number of parts is increased. (2) When a plurality of external resistors 108a are switched by the changeover switch 108b as shown in FIG. 6, a huge number of external resistors 108a and a changeover switch 108b are necessary for finely controlling the output current value. And
However, it is impossible to externally attach such a huge number of external resistors 108a and changeover switch 108b to the LED lighting circuit, and even if these are externally attached as much as possible, the output current value control is limited. Will occur.
In addition, a control signal for controlling each switch 108b is newly required, and similarly to the above, the circuit configuration becomes complicated and the number of parts increases.

The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to arbitrarily control the output current value without using external parts or external input signals. It is to provide an LED lighting circuit capable of performing. Another object is to provide an LED lighting circuit capable of highly accurate gradation display with a simple configuration.

[0019]

In order to achieve the above object, a feature of the first invention is that a frequency / voltage conversion circuit for converting an input frequency into a voltage and an output voltage of the frequency / voltage conversion circuit are provided. Voltage that converts this into current as reference voltage /
It is provided with a current conversion circuit and a mirror circuit which arbitrarily multiplies the output current of the voltage / current conversion circuit and supplies it to an external LED.

In order to achieve the above object, a feature of the second invention is that an LED dot matrisk indicator in which LEDs are arranged in a dot matrisk pattern as a lighting element is provided, and the LED is selected based on display data. LE that lights up automatically
In the D lighting circuit, a frequency / voltage conversion circuit for converting the frequency of the display data into a voltage, a voltage / current conversion circuit for converting the output voltage of the frequency / voltage conversion circuit into a reference voltage, and the voltage / voltage conversion circuit. And a mirror circuit for multiplying the output current of the current conversion circuit and supplying it to the LED.

[0021]

According to the first aspect of the invention as described above, the frequency / voltage conversion circuit converts the input frequency into a voltage, outputs a voltage according to the input arbitrary frequency, and outputs the voltage / current. The conversion circuit uses the output voltage of the frequency / voltage conversion circuit as a reference voltage and converts it into a current. Further, the mirror circuit arbitrarily multiplies the output current of the voltage / current conversion circuit as a reference current. That is, the voltage output from the frequency / voltage conversion circuit serves as a reference current, and an output current that is an arbitrary multiple thereof is obtained, and the LED is driven by this output current. As a result, the output current value can be freely set by supplying an input having an arbitrary frequency without requiring external parts or external control signals.

According to the second invention having the above-mentioned configuration, L
In the ED dot matrisk display, the LED lighting circuit can drive the LED by freely changing its output current value.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an LED lighting circuit according to the present invention.

The LED lighting circuit 10 has an input terminal 1 for an input Iin and an output terminal 2 for an output current Iout, and the frequency of the input Iin is converted to a voltage between the input and output terminals 1 and 2. A frequency / voltage conversion circuit (f-V conversion circuit) 3 for conversion, a reference resistor 4a and a constant current source 4b are used, and the output voltage Vf of the f-V conversion circuit 3 is used as a reference voltage. A voltage / current conversion circuit (V-I conversion circuit) 4 for outputting a constant current mirror circuit 5 that arbitrarily multiplies the reference current If from the V-I conversion circuit 4.
Constant current source 6 provided on the output side of the constant current mirror circuit 5
And are connected. The output terminal 2 is an external LE
It is connected to the potential power source PD via D7.

Next, the operation of the LED lighting circuit 10 of this embodiment will be described with reference to the waveform charts of FIGS. 2 (a), 2 (b) and 2 (c).

The input terminal 1 has an L level at the "H" level, for example.
Input the data to turn on ED7 and turn off at "L" level I
Entered as in. This input Iin has an arbitrary frequency f and an arbitrary time width t1 and t2 at the "H" level.
1, f2 (cycles T1, T2) respectively, and when this input Iin is input to the input terminal 1, this input Iin is frequency / voltage converted by the fV conversion circuit 3 and is output as its output. The output voltage Vf shown in FIG. 2A is output.

Here, in the case of the present example, the frequency is smaller in the time width t2 than in the time width t1, and the output voltage Vf changes stepwise in response to this, and the time width t2 becomes lower. ing.

This output voltage Vf is inputted as a reference voltage of the VI conversion circuit 4 and converted into a reference current If as shown in FIG. 2 (b). The reference current If from the VI conversion circuit 4 is supplied to the constant current mirror circuit 5, multiplied by a predetermined number, and output to the output terminal 2 as the output current Iout (FIG. 2C).

Thus, by arbitrarily changing the time widths t1 and t2 or the frequencies f1 and f2, the LED 7 is turned on in response to the change.

As described above, in this embodiment, the f-V conversion circuit 3 for converting the frequency of the input Iin into a voltage and the output voltage Vf of the f-V conversion circuit 3 are used as the reference voltage, and the current is converted into the reference current. Since the V-I conversion circuit 4 that outputs If and the constant current mirror circuit 5 that arbitrarily multiplies the reference current If from the V-I conversion circuit 4 are provided, the output is arbitrarily controlled only by the input pair output. be able to.

Therefore, unlike the LED lighting circuit 110 shown in FIG. 5A, it is not necessary to provide the control circuit 112 and it is not necessary to take in the PWM control signal for controlling the control circuit 112. Therefore, the circuit configuration can be simplified and the number of parts can be reduced.

That is, in the present embodiment, only one circuit has been described for one bit, but this type of LED lighting circuit is generally used as a plurality of bits, and therefore the PWM control signal is One input is required for each circuit. In the present embodiment, the PWM control signal does not have to be provided, so that the number of signal lines can be significantly reduced.

Similarly, the LED lighting circuit 12 shown in FIG.
External resistor 108a and changeover switch 10 as shown in FIG.
It is not necessary to provide 8b.

FIG. 3 is a diagram showing a schematic configuration of a main part of an LED dot matrix display showing an application example of the LED lighting circuit.

In this LED dot matrix display, one red / green / blue LED 7 is arranged in a matrix as one dot, and the LEDs are based on the display data.
7 is selectively turned on to perform full-color display.

The display section has n data lines s1, s2, s3 arranged in a matrix as shown in FIG.
~ Sn and n scan lines p1, p2, p3 to p
n, and the LED 7 is connected to each intersection. Although not shown, it is assumed that three sets of matrices having the same configuration as that shown in FIG. 3 are arranged corresponding to the LEDs for red, green, and blue.

LEs are attached to the scan lines p1 to pn.
A scan circuit 11 for sequentially scanning D7 is connected,
Further, the data lines s1 to sn are provided with the above-mentioned LEDs.
The lighting circuit 10 is connected. Here, the LED lighting circuit 10 drives each LED 7 in synchronization with the scan timing of the scan circuit 11. Further, although not shown, the LED dot matrix display is provided with a control unit for controlling the operations of the LED lighting circuit 10 and the scan circuit 11.

As described above, in the LED lighting circuit of the present invention, the output current value and the time width of the LED lighting circuit can be freely changed.
7 can be driven, which is more effective in a full-color display LED dot matrix display or the like which requires a highly accurate gradation function as in this application example.

[0040]

As described in detail above, according to the first invention, a frequency / voltage conversion circuit for converting an input frequency into a voltage and an output voltage of the frequency / voltage conversion circuit as a reference voltage are used. Since a voltage / current conversion circuit for converting the current into a current and a mirror circuit for arbitrarily multiplying the output current of the voltage / current conversion circuit and supplying the same to an external LED are provided, external parts and external control signals are not required. The output current value can be arbitrarily controlled only by input vs. output. As a result, the circuit configuration can be simplified, the number of parts can be significantly reduced, and the number of bits can be increased easily.

According to the second invention, in the LED lighting circuit of the LED dot matrisk display, the frequency / voltage conversion circuit for converting the frequency of the display data into a voltage and the output voltage of the frequency / voltage conversion circuit are used as references. Since a voltage / current conversion circuit for converting this into a current as a voltage and a mirror circuit for arbitrarily multiplying the output current of the voltage / current conversion circuit and supplying the same to the LED are provided, the same effect as that of the first aspect of the invention is provided. Further, in the case of performing full-color display, for example, it is possible to perform accurate gradation display with a simple circuit configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an LED lighting circuit according to the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the LED lighting circuit of the embodiment.

FIG. 3 is an LED showing an application example of the LED lighting circuit of the present invention.
It is a figure which shows schematic structure of the principal part of a dot matrix display.

FIG. 4 is a diagram showing a conventional LED lighting circuit.

FIG. 5 is a diagram showing another conventional LED lighting circuit.

FIG. 6 is a configuration diagram of another conventional LED lighting circuit.

[Explanation of symbols]

 3 f-V conversion circuit 4 V-I conversion circuit 5 constant current mirror circuit 7 LED 10 LED lighting circuit PD potential power supply Iin input Iout output current Vf output voltage

Claims (2)

[Claims] 1. A frequency for converting an input frequency into a voltage /
A voltage conversion circuit, a voltage / current conversion circuit that current-converts the output voltage of the frequency / voltage conversion circuit as a reference voltage, and an output current of the voltage / current conversion circuit is arbitrarily multiplied and supplied to an external LED. An LED lighting circuit comprising a mirror circuit. 2. An LED lighting circuit, which is provided in an LED dot matrisk display in which LEDs are arranged in a dot matrisk pattern as lighting elements, and which selectively lights the LEDs based on display data, wherein the frequency of the display data is To a voltage, a voltage / current conversion circuit that converts the output voltage of the frequency / voltage conversion circuit into a reference voltage into a current, and an output current of the voltage / current conversion circuit that is arbitrarily multiplied. L above
An LED lighting circuit, comprising: a mirror circuit for supplying to an ED.