JP5554145B2 - LED video display device - Google Patents

Description

  The present invention relates to an LED image display device using an LED (light emitting diode) as a light source, and more particularly to an LED lighting drive system for suppressing abnormal noise (harsh sound) generated in a power supply unit.

FIG. 5 is an image diagram of an LED display unit constituting the screen of the LED video display device.
As shown in the figure, the LED display unit 50 is composed of LEDs 51a, 51b, 51c,.
Screen LED display device, a large number of LED 51a, 51b, the LED display unit 50 51c · · are mounted in a matrix as a substrate unit, be configured by arranging a plurality of LED display units 50 of this general This substrate unit is called an LED display unit.

FIG. 6 is a diagram for explaining a drive circuit 60 of a conventional LED display unit 50.
In many cases, power is supplied to the LED for each LED display unit 50, and the drive circuit 60 of the LED display unit 50 is configured as shown in FIG.
6, 10 is a constant voltage power supply unit that supplies power to the LEDs 51a, 51b, 51c,... Mounted on the plurality of LED display units 50, and 20 is the LEDs 51a, 51b, 51c,. .. Is a switch circuit composed of switches 21a, 21b, 21c,... Connected in series with each other, and 30 indicates that each switch 21a, 21b, 21c,. This is a switch control unit that performs / OFF control.

Reference numeral 60 denotes a drive circuit for the LED display unit 50. The drive circuit 60 for the LED display unit includes the switch circuit 20 and the switch control unit 30 as shown in FIG.
Conventionally, in accordance with an ON / OFF control signal (PWM signal) from the switch control unit 30, the current value flowing from the constant voltage power supply unit 10 to each LED 51 a, 51 b, 51 c. The brightness adjustment (light emission control) of each LED 51a, 51b, 51c... Of the display unit 50 is realized.

When PWM control is performed in the LED video display device, the current value from the constant voltage power supply unit that flows in the LED display unit 50 depends on the ratio (duty ratio) of the LED lighting ( on ) period and the non-lighting ( off ) period. It fluctuates greatly.
FIG. 7 is a diagram illustrating a configuration example of the constant voltage power supply unit 10 that supplies power to the LED display unit 50.
As shown in FIG. 7, the secondary output unit of the forward type constant voltage power supply unit 10 generally includes a smoothing output electrolytic capacitor 101, diodes 102 and 103, a smoothing coil 104, and a transformer 105.

Reference numeral 106 denotes a switching element, and reference numeral 107 denotes an IC that controls the switching operation of the switching element 106.
The IC 107 performs on / off control of the switching element 106 so that the output of the constant voltage power supply unit 10 becomes a predetermined constant value.
Due to the fluctuation of the current value due to the PWM control on the LED display unit 50 side, the smoothing coil 104 on the secondary side of the constant voltage power supply unit 10 shown in FIG. 7 vibrates at a frequency in the human audible region. Abnormal noise).

  Therefore, for this problem, for example, in the light emitting element driving device described in Patent Document 1 (Japanese Patent Laid-Open No. 2006-114324), the current flowing through the light emitting element connected to the power source is turned on / off at a timing according to the PWM signal. A light-emitting element driving apparatus that employs a PWM control system that turns off and adjusts the light-emitting luminance of the light-emitting element according to the on / off ratio, and the frequency of the PWM signal is set to be equal to or higher than the upper limit of the human audible band Has been proposed.

JP 2006-114324 A

As described above, in the constant voltage power supply unit in the conventional LED video display device, the smooth coil vibrates at the frequency of the human audible region due to the fluctuation of the LED driving current value by the PWM control, and generates a sound that is harsh to the human. There was a problem to do.
Further, it is difficult to discriminate the harsh sound from the constant voltage power supply unit by the LED display unit alone, and there is a problem that “it may be recognized after being assembled as a screen”.
The present invention has been made to solve such a problem, and an LED video display capable of suppressing annoying sound of a constant voltage power supply unit generated by PWM control of a drive current of each LED of an LED display unit. An object is to provide an apparatus.

The LED image display device according to the present invention is an LED image display device in which an LED screen is formed by arranging a plurality of LED display units each having a plurality of LEDs mounted in a matrix, and is mounted on the plurality of LED display units. A constant voltage power supply unit that supplies power to each LED, and a plurality of LED display unit drive circuits that output a PWM signal based on a PWM command for performing light emission control of each LED; A screen controller for controlling a current value flowing in the LED, and a current detection unit for detecting a current value flowing in the drive circuit of the LED display unit ;
The driving circuit of the LED display unit, the is composed of the LED and a switch circuit composed of a switch connected in series to the switch control unit to switch on / off control of the switch circuit by the PWM signal, The switch control unit controls a light emission of each LED by changing a duty ratio of a pulse for lighting each LED based on the PWM signal from the screen controller, and the current detection unit displays the LED display When it is detected that the peak time interval of the current flowing through the drive circuit of the unit corresponds to a preset frequency and exceeds the preset peak current value, the frequency of the pulse for lighting the LED is changed. The peak time interval of the current value flowing through the LED display unit is adjusted.

  According to the present invention, since the peak time interval of the current value flowing through the LED display unit can be adjusted using PWM control, it is possible to easily generate an unpleasant sound without taking measures by replacing parts such as changing the material of the coil or adding a capacitor. Occurrence can be suppressed.

It is a conceptual diagram which shows the whole structure of the LED video display apparatus by Embodiment 1. 3 is an explanatory diagram of PWM control of the LED video display device according to Embodiment 1. FIG. FIG. 6 is a diagram showing a drive circuit for an LED display unit in a second embodiment. It is a figure which shows the structure of the constant voltage power supply part in Embodiment 3. FIG. It is an image figure of a LED display unit. It is a figure for demonstrating the drive circuit of the conventional LED display unit. It is a figure for demonstrating the constant voltage power supply part of an LED display unit.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In each figure, the same reference sign represents the same or equivalent.
Embodiment 1 FIG.
FIG. 1 is a diagram conceptually showing an LED video display device using a PWM control system according to Embodiment 1 of the present invention.
The LED video display device according to the first embodiment includes an LED screen 100 including a plurality of LED display units 50 and a screen controller 200 that performs light emission control of each LED of the plurality of LED display units 50.
Moreover, the constant voltage power supply part 10 which supplies a power supply to each LED51a, 51b, 51c .. mounted in the some LED display unit 50 is provided.

Further, each of the plurality of LED display units 50 constituting the LED screen 100 includes switches 21a, 21b, 21c,... Connected in series to the LEDs 51a, 51b, 51c,. The LED display unit drive circuit 60 includes a switch circuit 20 and a switch control unit 30 that performs on / off control of the switches 21a, 21b, 21c,.

In FIG. 1, reference numeral 200 denotes a screen controller. The screen controller 200 includes a PWM command unit 201, and each of the drive circuits 60 of the plurality of LED display units 50 constituting the LED screen 100. It is possible to issue a PWM control command.
That is, the switch control unit 30 outputs a PWM signal based on a command from the PWM command unit 201, and turns on / off the switches 21a, 21b, 21c,... Of the drive circuit 60 of the LED display unit.
1 shows a case where one constant voltage power supply unit 10 is provided for one LED display unit 50, all of the plurality of LED display units 50 from one constant voltage power supply unit 10 are shown. A power source may be supplied.

Next, a specific operation example of the LED video display device according to the present embodiment will be described.
FIG. 2 is an explanatory diagram of PWM control of the LED video display device according to the present embodiment.
As shown in FIG. 2, for example, when the image update cycle is 50 Hz, it is possible to set a lighting pulse of up to 20 msec in one lighting section. The brightness is adjusted by the time width of the lighting pulse.
In the simplest control, a method of setting one lighting pulse in one lighting section can be considered. In this control, it is assumed that a screen viewer feels an harsh sound from the power source.
In such a case, the PWM command unit 201 of the screen controller 200 shown in FIG. 1 sends a command signal to divide the lighting section to the drive circuit 60 of each LED display unit, thereby reducing the lighting pulse time width. Can be small.

FIG. 2A shows a case where one lighting pulse of 10 msec is set in one lighting section of 20 msec, and FIG. 2B shows a case where two lighting pulses of 5 msec are set in one lighting section of 20 msec. FIG. 2C shows a case where five lighting pulses of 2 msec are set in one lighting section of 20 msec.
As shown in FIG. 2B, the lighting section is divided into two sections and lighted in units of 5 msec, or as shown in FIG. 2C, the lighted sections are divided into five sections and lighted in units of 2 msec. The peak time interval of the current value flowing through the LED display unit 50 can be made smaller than before, and can be changed to a frequency higher than the band in which a person feels harsh.
On the contrary, when the number of divisions in the lighting section is increased and the lighting is performed, when an jarring sound from the constant voltage power supply unit 10 is felt, by reducing the number of divisions in the lighting section, a band that a person feels harsh is obtained. It is also possible to change to a lower frequency.

As described above, the LED image display device according to the present embodiment is an LED image display device in which the LED screen 100 is formed by arranging a plurality of LED display units 50 each having a plurality of LEDs mounted in a matrix. The LED 51a, 51b, 51c,... Mounted on the plurality of LED display units 50 are supplied with power to the constant voltage power supply unit 10, and the plurality of LED display units 50 are connected to the drive circuit 60 with the LEDs. A screen controller 200 that outputs a PWM signal based on a PWM command for performing light emission control of the LED and controls a value of a current flowing through each LED;
The drive circuit 60 of the LED display unit 50 includes the switch circuit 20 composed of switches 21a, 21b, 21c,... Connected in series to the LEDs 51a, 51b, 51c,. is an LED in the switch control unit 30 for on / off control, the switch control section 30, the change the Deyute ratio of a pulse for turning on the respective LED based on the PWM signal from the screen controller 200 each It controls the light emission of LED, when said audible frequency band of human from the constant-voltage power supply unit 10 feels harsh occurs, by changing the time of the pulse for lighting the LED, the LED display unit 50 adjusting the peak time interval of the current value flowing in.
Therefore, according to this embodiment, since the peak time interval of the current value flowing through the LED display unit can be adjusted using PWM control, it is possible to easily suppress the generation of harsh sounds.

Embodiment 2. FIG.
FIG. 3 is a diagram showing a configuration of a drive circuit of the LED display unit 50 used in the LED video display device according to the second embodiment.
As shown in FIG. 3, the LED display unit drive circuit 61 used in the present embodiment is an LED display unit drive circuit configured as shown in FIG. 6, and further includes a current detection unit 70. .
The current detection unit 70 detects a current value flowing from the constant voltage power supply unit 10 to the drive circuit 61 of the LED display unit.
Specifically, the LED display unit drive circuit 61 includes an LED display unit 50 in which a large number of LEDs 51a, 51b, 51c,..., Which are light emitting units, are mounted in a matrix, and switches 21a, 21b, 21c. The switch circuit 20, the switch control unit 31, and the current detection unit 70 are provided.

In the present embodiment, the current detection unit 70 is preset with a frequency and a peak current value that a person feels harsh.
Then, when the peak time interval of the current flowing through the LED display unit 50 corresponds to a preset frequency and exceeds the preset peak current value, the pulse detection time from the current detection unit 70 to the switch control unit 31 is obtained. A signal for changing the width is transmitted, and the switch control unit 31 changes the on / off time interval of each switch.
It is assumed that the current detection by the current detection unit 70 is performed at a certain period.
By adopting such a circuit configuration, it is possible to avoid the annoying noise generated from the smoothing coil 104 of the constant voltage power supply 10 without intervention of human hands based on the current detection value of the LED display unit 50. Become.

As described above, the LED video display device according to the present embodiment includes the current detection unit that detects the current value flowing through the drive circuit 60 of the LED display unit 50, and the current detection unit 70 drives the LED display unit 50 . Changed the pulse time width for turning on the LED from the current detection unit to the switch control unit when the peak time interval of the current flowing in the circuit corresponds to a preset frequency and exceeds the set peak current value The switch control unit 31 adjusts the peak time interval of the current value flowing through the LED display unit .
Therefore, according to the present embodiment, it is possible to automatically suppress the annoying noise generated from the smoothing coil 104 of the constant voltage power supply unit 10.

Embodiment 3 FIG.
FIG. 4 is a diagram illustrating a configuration of the constant voltage power supply unit 11 used in the LED video display device according to the third embodiment.
As shown in FIG. 4, the constant voltage power supply unit 11 used in the present embodiment is one in which an abnormal sound detection device 80 is incorporated in a conventional circuit configuration.
Specifically, as shown in FIG. 4, the secondary output unit of the constant voltage power supply unit 11 includes a smoothing output electrolytic capacitor 101, diodes 102 and 103, a smoothing coil 104, a transformer 105, and an abnormal sound detection device 80. Have
The abnormal sound detection device 80 is disposed in the vicinity of the smoothing coil 104 so as to easily detect an annoying sound (that is, an abnormal sound) generated from the smoothing coil 104.

Due to the fluctuation of the current value by PWM control on the LED display unit 50 side, the smoothing coil 104 on the secondary side of the constant voltage power supply unit 11 shown in FIG. Abnormal noise).
Note that the abnormal noise is detected based on the frequency level, the frequency fluctuation, the size of the abnormal noise, and the like.
In the present embodiment, when the abnormal noise detection device 80 detects an annoying noise (abnormal noise) generated from the smoothing coil 104 of the constant voltage power supply unit 11, the lighting pulse duration for the switch control unit 30 (see FIG. 1 ). The switch control unit 30 changes the on / off time interval of each switch.

In the present embodiment, by adopting such a circuit configuration, when the abnormal sound detection device detects an abnormal sound (harmful sound) generated from the smoothing coil of the constant voltage power supply unit, each switch is turned on by the switch control unit. Since the / off time interval is automatically changed, it is possible to avoid annoying noise generated from the smoothing coil of the constant voltage power supply without the intervention of a human hand.

As described above, the constant voltage power supply 10 of the LED video display device according to the present embodiment includes the abnormal sound detection device 80 that detects the generated abnormal noise, and when the abnormal noise detection device 80 detects the abnormal noise. , transmits a signal to change the pulse time width of lighting the LED from abnormal sound detection equipment 80 to the switch control unit 31, the switch control unit 31 adjusts the peak time interval of the current value flowing through the LED display unit 50 . Therefore, it is possible to automatically suppress the annoying noise generated from the smoothing coil of the constant voltage power source.

  INDUSTRIAL APPLICABILITY The present invention is useful for realizing an LED video display device that can suppress annoying sound generated in a constant voltage power supply unit during LED lighting drive by PWM control.

DESCRIPTION OF SYMBOLS 10 Constant voltage power supply part 20 Switch circuit 21a, 21b, 21c ... Switch 30, 31 Switch control part 50 LED display unit 51a, 51b, 51c ... LED
60, 61 LED display unit drive circuit 70 Current detection unit 80 Abnormal sound detection device 100 Screen 200 Screen controller 201 PWM command unit 101 Smoothing output electrolytic capacitor 102, 103 Diode 104 Smoothing output electrolytic capacitor 105 Transformer

Claims (2)

An LED video display device in which a plurality of LED display units each having a plurality of LEDs mounted in a matrix are arranged to form an LED screen,
A constant voltage power supply unit that supplies power to each LED mounted on the plurality of LED display units, and a drive circuit for the plurality of LED display units based on a PWM command for performing light emission control of each LED. A screen controller that outputs a PWM signal and controls a current value flowing through each LED; and a current detection unit that detects a current value flowing through a drive circuit of the LED display unit ;
The driving circuit of the LED display unit, the is composed of the LED and a switch circuit composed of a switch connected in series to the switch control unit to switch on / off control of the switching circuit by the PWM signal,
The switch control unit controls a light emission of each LED by changing a duty ratio of a pulse for lighting each LED based on the PWM signal from the screen controller, and the current detection unit displays the LED display When it is detected that the peak time interval of the current flowing through the drive circuit of the unit corresponds to a preset frequency and exceeds the preset peak current value, the frequency of the pulse for lighting the LED is changed. An LED image display device, wherein a peak time interval of a current value flowing through the LED display unit is adjusted. An LED video display device in which a plurality of LED display units each having a plurality of LEDs mounted in a matrix are arranged to form an LED screen,
A constant voltage power supply unit for supplying power to each LED mounted on the plurality of LED display units and detecting an abnormal noise generated therein , and a drive circuit for the plurality of LED display units And a screen controller that outputs a PWM signal based on a PWM command for performing light emission control of each LED, and controls a value of a current flowing through each LED,
The drive circuit of the LED display unit is configured by a switch circuit configured by a switch connected in series to each LED, and a switch control unit that controls on / off of the switch of the switch circuit by the PWM signal,
The switch control unit controls the light emission of each LED by changing the duty ratio of a pulse for lighting each LED based on the PWM signal from the screen controller, and the noise detecting device generates an abnormal sound. When detected, an LED video display device that adjusts a peak time interval of a current value flowing through the LED display unit by changing a frequency of a pulse for lighting the LED.

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