JP6080710B2 - display - Google Patents

Description

  The present invention relates to a display device used in a large-sized video display device, and more particularly to a display device that can dynamically change the number of scans.

  As a conventional display, a plurality of drive control lines for individually energizing a plurality of light emitting elements at predetermined intervals, and a pulse voltage supply line for supplying a plurality of light emitting elements to a pulse voltage that changes to an on or off state And driving the plurality of drive control lines with a predetermined time delay during the period when the pulse voltage supply line transitions to the ON state, thereby operating all of the plurality of light emitting elements at different timings, thereby There is one that suppresses the concentration of noise and suppresses noise accompanying an increase in current (see Patent Document 1).

  In addition, as a similar display, an LED light emitting unit in which a plurality of light emitting elements (LEDs) are arranged in parallel, and an LED drive control unit for sequentially energizing each LED with a predetermined pulse width at a predetermined interval are provided, and LED driving For each LED connected in parallel, there is a controller that reduces the generation of noise associated with energization of a large current by sequentially driving one period of pulse energization by shifting by a predetermined period (see Patent Document 2). ).

JP 2011-221262 A JP 2008-91311 A

In Patent Documents 1 and 2, when the light emitting element is driven in a time-sharing manner, the timing at which the light emitting element is operated by providing a delay time is different, whereby the timing at which the peak current is generated is dispersed, and the power supply voltage is It describes suppression of noise that occurs due to problems that rapidly decrease and current increases.
However, by shifting the operation timings of all the light emitting elements, the light emission time per light emitting element due to the pulse width driving is reduced, and a solution for reducing the light emission luminance is not shown.

  The present invention has been made to solve the above-described problems. By changing the number of light-emitting elements that are turned on between high brightness setting and low brightness setting, high brightness is achieved and low brightness is achieved. It is an object of the present invention to provide a display device that achieves low noise and low power consumption.

The display according to the present invention includes a power supply unit capable of individually changing a power supply voltage, a power supply switching circuit capable of turning on / off power supply from the power supply unit at an arbitrary timing, and receiving power supply from the power supply unit via the power supply switching circuit. a plurality of light emitting elements, and therefore the light emitting element is turned on and driven, is connected between one of the drive circuit and a plurality of light emitting elements among the plurality of driver circuits, a plurality of driving circuits connected respectively to the light emitting element, 1 One of the backflow prevention circuit for preventing the current flowing through the plurality of light-emitting element side from the drive circuit side, and a control unit for controlling the driving circuit and the power supply unit and the power supply switching circuit, a power supply unit, the backflow prevention circuit is connected to a high luminance mode The power supply voltage supplied to the light emitting element driven by the drive circuit is set higher than the power supply voltage supplied to the light emitting element driven by the other drive circuit, and the backflow prevention circuit is activated at low luminance. The power supply voltage supplied to the light emitting element but is driven by the connected driver circuit, as well as lower than the power supply voltage supplied to the light emitting device driven by other driving circuit, the driving circuit, a high luminance when the plurality of light emitting elements The light-emitting elements are driven to be driven at the same time, and the light-emitting elements are driven to be driven in a time-sharing manner when the luminance is low.

  According to the present invention, wasteful power consumption due to noise due to simultaneous switching and a large drop voltage can be suppressed during low luminance setting, and the emission luminance can be increased. Further, by dynamically changing the power supply voltage, it is possible to obtain a power supply voltage that does not require addition of a drop voltage that becomes reactive power that does not contribute to light emission, leading to low power consumption.

It is a block diagram which shows the outline | summary of an example of the video display apparatus with which the indicator of this invention is applied. It is a figure which shows the lighting unit used for the indicator of this invention. It is a figure which shows the example of a scan of the lighting unit used for the indicator of this invention. It is a figure which shows the structure of the indicator in Embodiment 1 of this invention. It is a state figure at the time of drive control of the light emitting element of the display which concerns on Embodiment 1 of this invention. It is a figure which shows the relationship of the power supply voltage of the power supply part used for the display in Embodiment 1 of this invention. It is a control schematic diagram which shows the relationship between the brightness | luminance of a display and scan duty which concern on Embodiment 1 of this invention. It is a figure which shows the structure of the indicator in Embodiment 2 of this invention. It is a figure which shows the structure of the indicator in Embodiment 3 of this invention.

Embodiment 1 FIG.
Hereinafter, the display in Embodiment 1 of this invention is demonstrated based on FIGS.
FIG. 1 is a block diagram showing an outline of an example of a video display device to which the display of the present invention is applied, FIG. 2 is a diagram showing a lighting unit of the video display device, and FIG. 3 is a diagram showing a scanning example of the lighting unit. .
First, an outline of a video display device to which the display of the present invention is applied will be described with reference to FIGS.

  In FIG. 1, a large video display device is configured by combining a plurality of lighting units 1 </ b> A to 1 </ b> F (the suffixes A to F are omitted in general terms) vertically and horizontally. Each of the lighting units 1A to 1F is supplied with power from power supply units 2A to 2C (generally omitted suffixes A to F), and controls lighting based on signals from the video signal reception and lighting control units 3A to 3C. Power control is performed. The video signal is supplied from the video signal source 4 to the video signal reception and lighting control units 3A to 3C.

  Each lighting unit 1 includes a plurality of light emitting elements 11 such as LEDs arranged in a matrix as shown in FIG. 2, a power supply unit, and a drive circuit (not shown in FIG. 2). These configurations will be described in detail with reference to FIG. The lighting unit 1 is composed of 16 to 32 light emitting elements 11 per line, and FIG. 2 shows one composed of 16 light emitting elements 11 per line.

The light emitting element 11 of the lighting unit 1 is driven and controlled by time-division line switching scan (dynamic) lighting. FIG. 3 shows control of 1/4 duty scan (Duty Scan) with four lines as one set. An example of a schematic diagram is shown.
In FIG. 3, black circles are driven light emitting elements (lighted), white circles are non-driven light emitting elements (non-lighted), and the scan [0] drive state, scan [1] drive state, and scan [2] from the left. , And the scan [3].

In the scan [0] driving state, the light emitting elements 11 of the first, fifth, ninth and thirteenth lines from the top are driven to be lit, and in the scanning [1] driving state, the second, sixth, The light emitting elements 11 of the 10th and 14th lines are lit and driven, and the light emitting elements 11 of the 3rd, 7th, 11th and 15th lines from the top are lit and driven in the scan [2] driving state. In the driving state [3], the light emitting elements 11 in the fourth, eighth, twelfth and sixteenth lines from the top are driven to light.
When the line to be turned on is switched at high speed (approximately 1 to 10 ms or less) and displayed as scan [0] → scan [1] → scan [2] → scan [3] → scan [0]. As visual recognition, it is recognized that all the light emitting elements are controlled to be turned on simultaneously.

As described above, the light-emitting elements 11 are turned on in a time-sharing manner for each line when the luminance is low. When the luminance is high, the light-emitting elements 11 of all four lines are turned on simultaneously. The state in which all four lines are turned on simultaneously and the state in which each line is turned on in a time-sharing manner can be changed as a “display capable of dynamically changing the number of scans”.
The reason for dynamically changing the number of scans is to suppress waste and switching noise during simultaneous lighting of four lines (controlling the lighting time short) in a low luminance state.
Also, the scan duty is changed according to the luminance. The relationship between luminance and scan duty will be described with reference to FIG.

  FIG. 4 is a diagram showing the configuration of the display (lighting unit) in the first embodiment of the present invention. The light emitting elements 11A to 11D (may be referred to as LED-A to LED-D) and the power source of FIG. The power supply unit 12 that can individually change the voltage supplied from the supply unit 2 via the cable as a power supply voltage (V-A, V-B, V-C, V-D), and power supply from the power supply unit 12 A plurality of power supply switching circuits 13A to 13D (which may be referred to as FET-A to FET-D) that can be turned on / off at an arbitrary timing, and a plurality of light-emitting elements 11A to 11D that are connected to each light-emitting element to drive the light-emitting elements. Drive circuits 14A to 14D (may be referred to as Dr-A to Dr-D), and one of the plurality of drive circuits 14A and the negative electrodes of the plurality of light emitting elements 11B to 11D. Diodes 15B-15 And a control unit 16 that controls the power supply unit 12, the power supply switching circuits 13A to 13D, and the drive circuits 14A to 14D.

  Although the power supply switching circuits 13A to 13D are illustrated by simple switches, they are actually configured by switching elements such as field effect transistors (FETs). In the diodes 15B to 15D of the backflow prevention circuit, the terminal side connected to the light emitting elements 11B to 11D is a positive electrode, and the terminal side connected to the drive circuit 14A is a negative electrode. In addition, the light emitting elements 11A to 11D are equivalent to four light emitting elements (one line of four lines) indicated by a dashed line ellipse in FIG.

FIG. 5 shows a state diagram at the time of driving control of the light emitting element of the display shown in FIG. 4, FIG. 5A shows an operation at high luminance, and FIG. 5B shows an operation at low luminance.
At the time of high brightness setting in FIG. 5A, the power supply switching circuits 13A to 13D (FET-A to FET-D) are turned on all at once, so that the drive circuits 14A to 14D ( When Dr-A to Dr-D) are driven at the same time, the light emitting elements 11A to 11D (LED-A to LED-D) are also turned on at the same time (the black coating points indicate ON (lighting operation)).

  At this time, the amount of current flowing from the power supply unit 2 to the power supply unit 12 changes in an increasing direction as shown in FIG. Therefore, the drop voltage in the cable between the power supply unit 2 and the power supply unit 12 increases, and the input voltage of the power supply unit 12 greatly decreases as shown in FIG. For this reason, when the luminance is high, it is necessary to cope with the magnitude of the drop voltage by slightly increasing the supply voltage of the power supply unit 2. As a result, the output terminal voltages of the drive circuits 14A to 14D (Dr-A to Dr-D) are maintained at appropriate output terminal voltages as shown in (d).

At this time, when the power supply voltages V-B, V-C, and V-D are equal to or higher than the power supply voltage V-A, the drive circuit 14A (Dr-A) passes through the diodes 15B to 15D of the backflow prevention circuit. Since the light emitting elements 11B to 11D (LED-B to LED-D) are pulled in, the power supply voltages VB, VC, and VD are set lower than the power supply voltage V-A. Thereby, when the drive circuit 14A (Dr-A) is activated, the light emitting elements 11B to 11D (LED-B to LED-D) are not driven by the drive circuit 14A (Dr-A).
Also, diodes 15B to 15D of backflow prevention circuits are provided so that the light emitting element 11A is not driven by the drive circuits 14B to 14D (Dr-B, Dr-C, Dr-D) with the power supply voltage V-A. .
That is, only the light emitting element LED-A is lit when the driving circuit 14A (Dr-A) is operated, and only the light emitting element LED-B is lit when the driving circuit 14B (Dr-B) is operated. To. The magnitude of the power supply voltage will be described in detail with reference to FIG.

  On the other hand, at the time of low luminance setting in FIG. 5B, the power supply switching circuits 13A to 13D (FET-A to FET-D) are sequentially turned on individually and only the drive circuit 14A (Dr-A) is turned on. Therefore, as shown in (a), when one power supply switching circuit FET-A to FET-D is turned on, one drive circuit 14A (Dr-A) is connected to the light emitting elements 11A to 11D (LED-A) connected thereto. ... (LED-D) are lit sequentially (lighted in time division).

  At this time, the amount of current flowing from the power supply unit 2 to the power supply unit 12 is as small as 1/4 as compared with the case of high luminance (collective driving) as shown in FIG. The drop voltage in this cable becomes as small as 1/4 due to the decrease in current. For this reason, the input voltage of the power supply unit 12 decreases and increases as shown in (b). If the supply voltage of the power supply unit 2 is the same as that at the time of high luminance, the drive circuit 14A (Dr-A) As shown in (d), the output terminal voltage becomes an output terminal voltage that is increased by a reduction of the drop voltage, which is an excessive voltage with respect to an appropriate output terminal voltage. This excess voltage × drive current = power becomes reactive power that does not directly contribute to light emission, and must be consumed by the drive circuit 14A.

  Therefore, at the time of low luminance setting, the reactive power can be eliminated by lowering the supply voltage of the power supply unit 2 by the drop amount of the cable between the power supply unit 2 and the power supply unit 12, and the power supply voltage V-B , V-C, and V-D drive the output terminal of the drive circuit 14A (Dr-A) by making the voltage higher than the power supply voltage V-A by the voltage drop of the diodes 15B to 15D which are backflow prevention circuits. The hour voltage can be made equal to that at the time of high luminance, and excessive (waste) voltage can be suppressed.

  When the drive circuit 14A drives each light-emitting element 11 in a time-sharing manner, it is necessary to increase the voltage of the power supply voltage by the voltage drop of the diodes 15B to 15D that are backflow prevention circuits. The direction is offset by the value of decreasing the power supply voltage by the amount of drop in the cable by the time-division driving of the light emitting element 11 in FIG. Therefore, the power supply voltage does not have to add the voltage drop of the diodes 15B to 15D, leading to low power consumption. The magnitude of the power supply voltage will be described in detail with reference to FIG.

  In FIG. 5, LED-A is a light emitting element 11A corresponding to the first line, LED-B is a light emitting element 11B corresponding to the second line, LED-C is a light emitting element 11C corresponding to the third line, LED Since -D is the light emitting element 11D corresponding to the fourth line, in one cycle of the vertical synchronizing signal, the four light emitting elements 11 are simultaneously turned on when the luminance is high, and each light emitting element 11 is time-divided when the luminance is low. It is lit and driven.

6A and 6B are diagrams showing the relationship of the power supply voltage, which is the output of the power supply unit 12. FIG. 6A shows the case in the high luminance mode, and FIG. 6B shows the case in the low luminance mode.
In the case of high brightness in FIG. 6A, the power supply voltage VA has a voltage difference of VA with respect to the reference voltage (0V), and the power supply voltages V-B, V-C, V- D has a voltage difference of V−B, V−C, and V−D with respect to the reference voltage (−XV), but the power supply voltages V−B, V−C, and V−D are the reference voltage ( 0V) and a value smaller than the power supply voltage VA.

  On the other hand, in the case of low luminance in FIG. 6B, the reference voltages of the power supply voltages V-B, V-C, and V-D are the same as the reference voltage (0 V) of the power supply voltage V-A, and the power supply voltage V -A has a voltage difference of VA with respect to the reference voltage (0V), and the power supply voltages V-B, V-C, and V-D are V-B and V-C with respect to the reference voltage (0V). , V-D, but the power supply voltages V-B, V-C, V-D are set to a value larger than the power supply voltage V-A, and the value is the power supply by the voltage drop of the diode. The voltage is set higher than the voltage VA.

As described above, by dynamically changing the operation timing of the drive circuit 14 of the light emitting element 11 between the high luminance setting and the low luminance setting, noise and unnecessary power consumption due to switching can be suppressed at the time of low luminance setting. High brightness can be obtained.
Further, suppression of a large drop voltage can be realized by adjusting the driving voltage of the light emitting element 11 at the same time as changing the operation timing of the driving circuit 14.

By dynamically changing the power supply voltage of the drive circuit 14 of the light-emitting element 11 for each drive circuit group, the diodes 15B to 15D, which are current backflow prevention circuits, are always reverse-biased, and the drive circuit 14A operates when the drive circuit 14A operates. The control is prevented from affecting the light emitting element 11B to be controlled by the circuit 14B. By doing so, the voltage that does not add the drop voltage that becomes reactive power that does not contribute to light emission can be obtained, leading to low power consumption.
Note that when high brightness is set, the drop voltage and noise cannot be suppressed. However, since most of the commonly used brightness area is an intermediate area, it is effective in actual operation.

Next, referring to FIG. 7, the relationship between luminance and scan duty will be described. In order to simplify the description, in FIG. 7, the operation is performed with the luminance level 8 and the gradation level 4 (0, 1, 2, 3) by the drive control in the 1/4 duty mode.
FIG. 7A is a schematic control diagram of the state at the time of high luminance, FIG. 7B is at the time of low luminance, and FIG. In FIG. 7, black portions indicate the state in which the light emitting element 11 is lit, and the numbers 1, 2 and 3 there are merely units of length.

  First, at the time of high luminance (brightness level 8/8) in FIG. 7A, the light emitting element 11 is not turned on at the gradation level 0 from the top as in the scan [0]. At the gradation level 2, the light emitting element 11 is turned on in a 2/3 cycle as in scan [1]. At the gradation level 3, the light emitting element 11 is turned on in a 3/3 cycle as in scan [2]. At the gradation level 1, the light emitting element 11 is lit at 1/3 period as in scan [3].

  Next, at the time of low luminance (brightness level 2/8) in FIG. 7B, the light emitting element 11 is not turned on at the gradation level 0 in order from the top as in the scan [0]. At gradation level 1, the light emitting element 11 is turned on at a cycle of 1/4 * 1/3 after a quarter cycle from the scan [0] as in the scan [1]. At the gradation level 3, the light emitting element 11 is turned on at a period of 1/4 * 3/3 after a quarter period from the scan [1] as in the scan [2]. At the gradation level 2, like the scan [3], the light emitting element 11 is turned on at a 1/4 * 2/3 cycle after a quarter cycle from the scan [2].

  Next, at the time of low luminance (luminance level 2/8) of the conventional method in FIG. 7C, scanning is performed at gradation level 0 in order from the top in the same time zone of 1/4 cycle of the repetition cycle [0. ], The light emitting element 11 is not turned on. At gradation level 1, the light emitting element 11 is lit at a cycle of 1/4 * 1/3 as in scan [1]. At the gradation level 3, the light emitting element 11 is lit at a period of 1/4 * 3/3 as in scan [2]. At gradation level 2, the light emitting element 11 is lit at a period of 1/4 * 2/3 as in scan [3].

Thus, at the time of low luminance, each light emitting element 11 is driven to be lit in a time division manner in the present invention, whereas in the conventional method, each light emitting element 11 is driven to be turned on simultaneously.
Therefore, in the present invention, it is possible to suppress unnecessary power consumption due to noise due to simultaneous switching and a large drop voltage at the time of setting low luminance, and it is possible to increase light emission luminance when high luminance is required. In the conventional method, select whether to achieve high brightness by allowing noise and large drop voltage due to simultaneous switching, or to be able to display at high brightness instead of suppressing noise and large drop voltage due to simultaneous switching. There was a need to do.

Embodiment 2. FIG.
Next, the display (lighting unit) in Embodiment 2 of this invention is demonstrated based on FIG.
FIG. 8 is a diagram showing the configuration of the display in the second embodiment, and the path is actively disconnected instead of the diodes 15B to 15D provided as the backflow prevention circuit shown in FIG. 4 of the first embodiment. This is a backflow prevention circuit of openable and closable connection circuits 17B to 17D (Sw-B, Sw-C, Sw-D). As the connection circuits 17B to 17D, semiconductor switching elements are used, and the switches can be turned on and off by signals from the control unit 16.
Other configurations are the same as those of the first embodiment, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

Also in FIG. 8, when the high luminance is set, the power supply switching circuits 13A to 13D (FET-A, FET-B, FET-C, FET-D) are turned on all at once, so that the connection circuits 17B to 17D are connected. In the (ON) state, the drive circuit 14A (Dr-A) is in a state of drawing the light emitting element 11B (LED-B).
Therefore, all of the connection circuits 17B to 17D (Sw-B, Sw-C, Sw-D) are disconnected (off), so that the light emitting elements 11B to 11D are activated when the drive circuit 14A (Dr-A) is activated. (LED-B, LED-C, LED-D) is not driven.

  At the time of low luminance setting, the power supply switching circuits 13A to 13D (FET-A, FET-B, FET-C, FET-D) are individually turned on, so that the drive circuit 14A (Dr-A) is light-emitting element 11B. In order to sequentially drive ˜11D (LED-B, LED-C, LED-D), the connection circuits 17B to 17D are connected (ON).

Also in the second embodiment, similarly to the first embodiment, the operation timing of the drive circuit 14 of the light emitting element 11 is dynamically changed between the high luminance setting and the low luminance setting, so that the low luminance setting is performed. Noise and unnecessary power consumption can be suppressed, and high luminance can be obtained.
Further, suppression of a large drop voltage can be realized by adjusting the driving voltage of the light emitting element 11 at the same time as changing the operation timing of the driving circuit 14.
Further, by dynamically changing the power supply voltage, it is possible to obtain a power supply voltage that does not require addition of a drop voltage that becomes reactive power that does not contribute to light emission, leading to low power consumption.

  In the invention of the second embodiment, connection circuits 17B to 17D as backflow prevention circuits are inserted between one drive circuit 14A (Dr-A) and light emitting elements 11B to 11D (LED-B to LED-D). However, as compared with the backflow prevention circuits 15B to 15D using diodes, there is an effect of reducing reactive power due to the forward drop voltage of the diodes.

Embodiment 3 FIG.
Next, the display (lighting unit) in Embodiment 3 of this invention is demonstrated based on FIG.
FIG. 9 is a diagram showing the configuration of the display in the third embodiment, and connection circuits 17B to 17D (Sw-B, Sw-C, Sw-D) as the backflow prevention circuit shown in FIG. 8 of the second embodiment. And a plurality of driving circuits 14A to 14D (Dr-A, Dr-B, Dr-C, Dr-D) are used as a driving unit 18 built in one IC.
Other configurations are the same as those of the first embodiment, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

Also in FIG. 9, as in FIG. 8, the power supply switching circuits 13 </ b> A to 13 </ b> D (FET-A, FET-B, FET-C, FET-D) are turned on at a time when the high luminance is set. When all of the circuits 17B to 17D (Sw-B, Sw-C, Sw-D) are disconnected (off), and the drive circuit 14A (Dr-A) is activated, the light emitting elements 11B to 11D (LEDs) -B, LED-C, LED-D) are not driven.
At the time of low luminance setting, the power supply switching circuits 13A to 13D (FET-A, FET-B, FET-C, FET-D) are individually turned on, so that the drive circuit 14A (Dr-A) is light-emitting element 11B. In order to drive ˜11D (LED-B, LED-C, LED-D), the connection circuits 17B to 17D are in a connected (ON) state.

In the invention of the third embodiment, connection circuits 17B to 17D for switching the drive circuit 14 of the light emitting element 11 are provided in the IC together with the plurality of drive circuits 14 to form one drive unit 18, and the operation timing of the drive circuit 14 is increased. By dynamically changing between the luminance setting and the low luminance setting, noise and wasteful power consumption can be suppressed and high luminance can be obtained at the time of low luminance setting.
In addition, by providing the connection circuit 17 for switching the drive current of the light emitting element 11 inside the IC of the drive unit 18, it is possible to suppress the mounting of components on the board and to easily optimize the drive circuit 14. Thus, it becomes possible to further reduce power consumption.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

11A to 11D (LED-A to LED-D): light emitting element, 12: power supply unit,
13A to 13D (FET-A to FET-D): power supply switching circuit,
14A to 14D (Dr-A to Dr-D): drive circuit,
15B to 15D: diode (backflow prevention circuit), 16: control unit,
17B to 17D (Sw-B, Sw-C, Sw-D): connection circuit (backflow prevention circuit),
18: Drive unit.

Claims (4)

A power supply unit that can individually change the power supply voltage, a power supply switching circuit that can turn on / off power supply from the power supply unit at an arbitrary timing, a plurality of light emitting elements that receive power supply from the power supply unit via the power supply switching circuit, and the light emission A plurality of driving circuits connected to each light emitting element to drive the element, and one driving circuit among the plurality of driving circuits is connected between the plurality of light emitting elements, and the one driving circuit side A backflow prevention circuit that blocks current flowing from the plurality of light emitting elements to the plurality of light emitting elements, a control unit that controls the power supply unit, the power supply switching circuit, and the drive circuit, and the power supply unit includes the backflow prevention circuit when the luminance is high. The power supply voltage supplied to the light-emitting element driven by the connected drive circuit is set higher than the power supply voltage supplied to the light-emitting element driven by the other drive circuit to reduce the brightness. The at the power supply voltage supplied to the light emitting element backflow prevention circuit is driven by the connected driver circuit, as well as lower than the power supply voltage supplied to the light emitting device driven by other driving circuit, the driving circuit includes a high intensity A display in which the plurality of light emitting elements are driven to be turned on at the same time, and each light emitting element is driven to be turned on in a time division manner at a low luminance.   2. The display according to claim 1, wherein the backflow prevention circuit is configured by a diode having a positive electrode on a terminal side connected to the light emitting element and a negative electrode on a terminal side connected to the driving circuit.   The display device according to claim 1, wherein the backflow prevention circuit includes a connection circuit that can be opened and closed.   The display according to claim 3, wherein the driving circuit and the backflow prevention circuit are configured as a driving unit built in one IC.