JP4635522B2 - Multi-channel current output driver circuit, semiconductor device having the same circuit, and light emitting diode driving device - Google Patents

Description

  The present invention relates to a multichannel current output type driver circuit, a semiconductor device having the circuit, and a light emitting diode driving device.

  In recent years, various electronic devices have used a plurality of light emitting diodes for notification and warning, and a light emitting diode driving device for lighting the plurality of light emitting diodes has a current flowing in the light emitting diodes as a plurality of loads. A multi-channel current output type driver circuit configured to supply the above is used (for example, see Patent Document 1).

  As this multi-channel current output type driver circuit, a circuit having a configuration schematically shown in FIG. 3 is used.

  That is, the multi-channel current output type driver circuit 101 includes a plurality of current output circuits 102, one control circuit 103 that controls the current output from each current output circuit 102 to a predetermined value, and a selection signal. One current output circuit 102 selected from a plurality of current output circuits 102 based on S101 and a selection circuit 104 for connecting the control circuit 103 are provided, and each current output circuit 102 has a load 105 as a load 105. The light emitting diode was connected.

The multi-channel current output type driver circuit 101 outputs a current from the current output circuit 102 selected by the selection circuit 104 and supplies the current to the load 105.
JP-A-11-115241

  However, since the conventional multi-channel current output type driver circuit 101 is configured to control the current output from a plurality of current output circuits 102 using a single control circuit 103, Immediately after switching the current output circuit 102 based on the selection signal S101, there is a possibility that transient noise may occur in the output current.

  That is, in the conventional multi-channel current output type driver circuit 101, the control circuit 103 continuously operates before and after switching the current output circuit 102 based on the selection signal S101, and the current output selected before switching If the output current is greatly different between the circuit 102 and the current output circuit 102 selected after switching, the control signal for controlling each current output circuit 102 by the control circuit 103 will change greatly in response to this, The change in the transient control signal directly affects the current output circuit 102, and immediately after switching the current output circuit 102, the current output from the current output circuit 102 also changes transiently. May be superimposed as noise on the output current.

Accordingly, in the present invention according to claim 1, a plurality of current output circuits, a control circuit for controlling the current output from each current output circuit to be a predetermined value, and the plurality of current output circuits. And a selection circuit for selecting one of the current output circuits and connecting to the control circuit, and a multi-channel current output type configured to output current from the current output circuit selected by the selection circuit In the driver circuit, each current output circuit has a plurality of constant current circuits for supplying different constant currents, and any one or a plurality of constant current circuits are selected based on a selection signal selected by the selection circuit. so as to output a current to the light emitting diode by operating simultaneously, a constant current circuit having the same configuration of the current output circuit, outputs a smaller current than the current output circuit Puricha Provided with a circuit to each current output circuit to drive the precharge circuit provided at the current output circuit before outputting the current from said current output circuit selected by the selection circuit, and outputs the current from the current output circuit In some cases, it was decided to stop driving the precharge circuit .

  According to a second aspect of the present invention, in the first aspect of the present invention, a transistor as a constant current source is provided in the current output circuit, and the gate voltage of the transistor is controlled by the control circuit. Decided to configure.

According to the third aspect of the present invention, a plurality of current output circuits, a control circuit for controlling the current output from each current output circuit to be a predetermined value, and the plurality of current output circuits. And a selection circuit for selecting one of the current output circuits and connecting to the control circuit, and a multi-channel current output type configured to output current from the current output circuit selected by the selection circuit In a semiconductor device having a driver circuit, each current output circuit has a plurality of constant current circuits for supplying different constant currents, and one or a plurality of constant current circuits are selected based on a selection signal selected by the selection circuit. so as to output a current to the light emitting diode by operating the constant current circuit at the same time, the multi-channel current output type driver circuit, identical to the constant current circuit of each current output circuit And a precharge circuit that outputs a smaller current than each current output circuit is provided in each current output circuit, and before the current is output from the current output circuit selected by the selection circuit, The precharge circuit provided is driven, and when the current is output from the current output circuit, the drive of the precharge circuit is stopped .

  In the present invention according to claim 4, in the present invention according to claim 3, a transistor as a constant current source is provided in the current output circuit, and a gate voltage of the transistor is controlled by the control circuit. Decided to configure.

In the present invention according to claim 5, a plurality of light emitting diodes, a current output circuit connected to each light emitting diode, and a single control for controlling the current output from each current output circuit to a predetermined value. A circuit and a selection circuit that selects one of the plurality of current output circuits and connects to the control circuit, and outputs a current from the current output circuit selected by the selection circuit In the light-emitting diode driving device configured to light the light-emitting diode, each current output circuit has a plurality of constant current circuits for supplying different constant currents, and the selection signal selected by the selection circuit based to output a current to the light emitting diode by operating either one or more of the constant current circuit simultaneously, and the constant current circuit of each current output circuit A precharge circuit that outputs a smaller current than each current output circuit is provided in each current output circuit, and the current output circuit before outputting current from the current output circuit selected by the selection circuit; The precharge circuit provided in the circuit is driven, and when the current is output from the current output circuit, the precharge circuit is stopped .

  Further, in the present invention according to claim 6, in the present invention according to claim 5, a transistor as a constant current source is provided in the current output circuit, and the gate voltage of the transistor is controlled by the control circuit. Decided to configure.

  And in this invention, there exists an effect described below.

  That is, in the present invention, a precharge circuit that has the same configuration as the current output circuit and outputs a smaller current than the current output circuit is provided in the current output circuit, and before the current is output from the current output circuit selected by the selection circuit. Since the precharge circuit provided in the current output circuit is driven, the noise superimposed on the current output from the current output circuit immediately after switching the current output circuit by the selection circuit is reduced. be able to.

  In the present invention, a transistor as a constant current source is provided in the current output circuit, and the gate voltage of the transistor is controlled by the control circuit. Therefore, the circuit configuration of the current output circuit and the control circuit is simplified. Can be

  The light-emitting diode driving device according to the present invention is a device for lighting a plurality of light-emitting diodes mounted on various electronic devices for notification and warning, and the light-emitting diode driving device includes a plurality of light-emitting diodes. A semiconductor device in which a multi-channel current output type driver circuit configured to supply current to a diode is formed on a semiconductor substrate is used.

  The multi-channel current output type driver circuit includes a plurality of current output circuits, a control circuit that controls a current output from each current output circuit to a predetermined value, and a plurality of current output circuits. The current output circuit is connected to the control circuit, and a current is output from the current output circuit selected by the selection circuit.

  Moreover, in the multi-channel current output type driver circuit according to the present invention, each current output circuit is provided with a precharge circuit that has the same configuration as each current output circuit and outputs a smaller current than each current output circuit.

  Specifically, each current output circuit is provided with a transistor as a constant current source, and the precharge circuit is also provided with a transistor as a current source, and the gate voltage of these transistors is controlled by a control circuit. Yes. This simplifies the circuit configuration of the current output circuit and the control circuit, thereby preventing an increase in circuit scale and manufacturing cost.

  The multi-channel current output type driver circuit according to the present invention is configured to drive the precharge circuit provided in the current output circuit before outputting the current from the current output circuit selected by the selection circuit. .

  That is, in the multi-channel current output type driver circuit according to the present invention, when one current output circuit is selected by the selection circuit, the precharge circuit is first driven, and the control circuit is previously operated by driving the precharge circuit. After that, the driving of the precharge circuit is stopped, the selected current output circuit is driven, and the current is output from this current output circuit. In other words, in the conventional multi-channel current output type driver circuit, the current is output from another current output circuit immediately after the current is output from one current output circuit when the channel is switched. In the multi-channel current output type driver circuit according to the invention, the precharge circuit is operated once immediately after the current is output from the current output circuit when the channel is switched, and then the current is output from another current output circuit. I am doing so.

  As described above, since the precharge circuit is driven before operating the current output circuit selected by the selection circuit, when the current output circuit selected by the selection circuit subsequently operates, the precharge circuit is precharged by the control circuit. The circuit is controlled. In addition, since the precharge circuit has the same configuration as the current output circuit, almost the same control signal is output from the control circuit before and after the current output circuit operates. As a result, unlike the conventional multi-channel current output type driver circuit, there is almost no transitional change in the control signal, and accordingly, the current output circuit outputs the signal immediately after operating the current output circuit. As a result, the noise that is superimposed on the output current of the current output circuit can be extremely reduced.

  In addition, since the precharge circuit is configured to output a smaller current than the current output circuit, the increase in power consumption due to the provision of the precharge circuit and the influence of errors on the output current are suppressed. Can do.

  A specific configuration of the multi-channel current output type driver circuit according to the present invention will be described below with reference to the drawings.

  As schematically shown in FIG. 1, the multi-channel current output type driver circuit 1 has a plurality of current output circuits 2 and one unit that controls the current output from each current output circuit 2 to a predetermined value. And a selection circuit 4 for connecting the current output circuit 2 selected from the plurality of current output circuits 2 and the control circuit 3 based on a selection signal S1 supplied from the outside. A load 5 such as a light emitting diode is connected to each current output circuit 2.

  In the multi-channel current output type driver circuit 1, a precharge circuit 6 is provided in each current output circuit 2.

  Here, the selection circuit 4 is composed of a multiplexer that operates based on a selection signal S1 from the outside, and a switch group (SA (k) that connects each current output circuit 2, precharge circuit 6, and control circuit 3 to each other. ), SB (k), SC (k), SP1 (k), SP2 (k), k represents the channel number of the selected current output circuit 2.) The switching signal S2 which is the decoding result of the selection signal S1 Is switched intermittently.

  As shown in FIG. 2, each current output circuit 2 has constant current circuits 2a to 2n for supplying different constant currents, and one or a plurality of them are selected based on a selection signal S1 supplied from the outside. The constant current circuits 2a to 2n are simultaneously operated.

Each of the constant current circuits 2a to 2n has the drains of the transistors T1 to Tn connected to the load 5, and the resistors R1 to Rn are connected between the sources of the transistors T1 to Tn and the power supply terminal VSS. A predetermined current is applied to the load 5 by applying a predetermined voltage to the gates of T1 to Tn using the control circuit 3. Here, ^assuming that the current passed through the constant current circuit 2a is I, a current of 2 · I is passed through the constant current circuit 2b, and a current of 2 ^n-1 · I is passed through the constant current circuit 2n. Thus, the same current as that converted from digital to analog is supplied by the selection signal S1 from the outside.

  Each of the constant current circuits 2a to 2n has a gate terminal 7 connected to the gates of the transistors T1 to Tn via switches SWA1 to SWAn that are intermittently controlled by a selection signal S1, and the gate terminal 7 and the ground terminal GND. The capacitor C is connected between the gates of the transistors T1 to Tn and the switches SWB1 to SWBn controlled by the selection signal S1 between the gates of the transistors T1 to Tn and the drains of the transistors T1 to Tn. Are connected to switches SWC1 to SWCn that are intermittently controlled by a selection signal S1.

  The precharge circuit 6 provided in each current output circuit 2 has the same configuration as the constant current circuits 2a to 2n of each current output circuit 2, and outputs less current than the constant current circuits 2a to 2n of the current output circuit 2. It is configured to do. That is, the precharge circuit 6 connects the drain of the transistor Tp to the load 5 via the switch SBp (k) that is intermittently controlled by the switching signal S2, and the resistor Rp is connected between the source of the transistor Tp and the power supply terminal VSS. , And a capacitor Cp is connected between the gate of the transistor Tp and the ground terminal GND, and a predetermined voltage is applied to the load 5 by applying a predetermined voltage to the gate of the transistor Tp using the control circuit 3. Current is applied. Here, the resistance value of the resistor Rp provided in the precharge circuit 6 is made sufficiently larger (for example, 100 times) than the resistance values of the resistors R1 to Rn provided in the constant current circuits 2a to 2n. Is made sufficiently smaller (for example, 1/100 times) than the current passed through the constant current circuits 2a to 2n. As a result, since the precharge circuit 6 can be configured to output a smaller current than the current output circuit 2, the increase in power consumption due to the provision of the precharge circuit 6 and the influence of errors on the output current are suppressed. can do.

  Each current output circuit 2 includes a reference terminal 8 and a detection terminal 9, and a reference resistor Rref is connected between the reference terminal 8 and the power supply terminal VSS. The detection terminal 9 and the resistors R1 to Rn (transistors A switch SC (k) that is intermittently controlled by a switching signal S2 is connected between the detection terminal 9 and the resistor Rp (the drain of the transistor Tp) via the switches SWC1 to SWCn. Is connected to a switch SP1 (k) that is intermittently controlled by a switching signal S2.

  As shown in FIG. 2, the control circuit 3 connects the reference terminal 8 of the current output circuit 2 to the non-inverting input terminal of the comparison amplifier 10 via a switch SA (k) that is intermittently controlled by the switching signal S2. The detection terminal 9 of the current output circuit 2 is connected to the inverting input terminal of the comparison amplifier 10, and further, the output terminal of the comparison amplifier 10 is connected to the gate terminal 7 via a switch SB (k) that is intermittently controlled by the switching signal S2. In addition, the output terminal of the comparison amplifier 10 is connected to the gate of the transistor Tp of the precharge circuit 6.

  Then, the control circuit 3 operates the comparison amplifier 10 via the switches SA (k), SB (k) (SP2 (k)), SC (k) (SP1 (k)) connected by the switching signal S2. The comparison amplifier 10 compares the potential of the reference terminal 8 with the potential of the detection terminal 9, and sends a control signal S3 corresponding to the potential difference to the gates of the transistors T1 to Tn of the current output circuit 2 or the transistor Tp of the charge circuit 6. The gate is energized.

  Next, the operation of the multi-channel current output type driver circuit 1 having the above configuration will be described. In the following description, the load 5 is energized by the current output circuit 2 of the second channel of the multi-channel current output type driver circuit 1 and then the load 5 is energized by the current output circuit 2 of the fifth channel. Will be described in detail.

  First, the multi-channel current output type driver circuit 1 generates a switching signal S2 by a selection circuit 4 based on a selection signal S1 supplied from the outside, and switches the second channel switch SA (2) with this switching signal S2. Switch SP2 (2), switch SP1 (2), and switch SBp (2) are connected, and switch SB (2) and switch SC (2) are disconnected. All other switches are in a disconnected state.

  As a result, the multi-channel current output type driver circuit 1 energizes the load 5 from the precharge circuit 6 provided in the current output circuit 2 of the second channel.

  The multi-channel current output type driver circuit 1 connects only the switches SWA1, SWB1, and SWC1 of the first constant current circuit 2a of the current output circuit 2 of the second channel, for example, based on the selection signal S1 supplied from the outside. State.

  Next, the multi-channel current output type driver circuit 1 generates a switching signal S2 by the selection circuit 4 after a predetermined time has elapsed, and switches SA (2) and SB (2) of the second channel by this switching signal S2. The switch SC (2) is set in a connected state, and the switch SP1 (2), the switch SP2 (2), and the switch SBp (2) are set in a disconnected state.

  As a result, the multi-channel current output type driver circuit 1 energizes the load 5 from the first constant current circuit 2a of the current output circuit 2 of the second channel.

  As described above, when operating the current output circuit 2 of the second channel, the multi-channel current output type driver circuit 1 drives the precharge circuit 6 provided in the current output circuit 2 in advance, and this precharge circuit 6, a relatively small current is supplied to the load 5, and then the current output circuit 2 is driven to supply a relatively large current to the load 5.

  Next, when the current output circuit 2 of the fifth channel is selected by the selection signal S1 supplied from the outside, the multi-channel current output type driver circuit 1 selects the selection circuit 4 based on the selection signal S1 supplied from the outside. The switch signal S2 is generated by the switch signal S2, and the switch SA (5), the switch SP2 (5), the switch SP1 (5) and the switch SBp (5) of the fifth channel are connected by the switch signal S2 and the switch SB (5) and switch SC (5) are disconnected. All other switches are in a disconnected state.

  As a result, the multi-channel current output type driver circuit 1 energizes the load 5 from the precharge circuit 6 provided in the current output circuit 2 of the fifth channel.

  The multi-channel current output type driver circuit 1 connects only the switches SWA2, SWB2, SWC2 of the second constant current circuit 2b of the current output circuit 2 of the fifth channel, for example, based on the selection signal S1 supplied from the outside. State.

  Next, the multi-channel current output type driver circuit 1 generates a switching signal S2 by a selection circuit 4 after a predetermined time has elapsed, and switches SA (5) and SB (5) of the fifth channel by this switching signal S2. The switch SC (5) is set in a connected state, and the switch SP1 (5), the switch SP2 (5), and the switch SBp (5) are set in a disconnected state.

  As a result, the multi-channel current output type driver circuit 1 energizes the load 5 from the second constant current circuit 2b of the current output circuit 2 of the fifth channel.

  As described above, the multi-channel current output type driver circuit 1 also drives the precharge circuit 6 provided in the current output circuit 2 in advance when the current output circuit 2 of the fifth channel is operated. A relatively small current is supplied to the load 5 using the circuit 6, and then the current output circuit 2 is driven to supply a relatively large current to the load 5.

  As described above, the multi-channel current output type driver circuit 1 having the above configuration drives the precharge circuit 6 first when the selection circuit 4 selects one current output circuit 2, and this precharge circuit 6, the control circuit 3 is operated in advance, and then the precharge circuit 6 is stopped, the selected current output circuit 2 is driven, and current is output from the current output circuit 2. ing.

  As described above, since the precharge circuit 6 is driven before the current output circuit 2 selected by the selection circuit 4 is operated, when the current output circuit 2 selected by the selection circuit 4 is operated thereafter. The precharge circuit 6 is controlled by the control circuit 3.

  Moreover, in the multi-channel current output type driver circuit 1 having the above configuration, the precharge circuit 6 has the same configuration as that of the current output circuit 2, so that the control circuit 3 substantially before and after the current output circuit 2 operates. A similar control signal S3 is output, and there is almost no transitional change in the control signal S3. Accordingly, the current output circuit 2 outputs the signal immediately after the current output circuit 2 is operated. As a result, the noise that is superimposed on the output current of the current output circuit 2 can be extremely reduced.

That is, when the precharge circuit 6 is not provided, the gate of the transistor T _k−1 of the (k−1) th channel current output circuit 2 is still immediately after the kth channel current output circuit 2 is operated. Since the voltage is output, the transient signal change ΔId flowing in the transistor T _k of the k-channel current output circuit 2 has the control signal S3 changed from the saturation region to the non-saturation region of the transistor T _k . Then,
ΔId = β (Vg _(k-1) −Vt) ² −β {2 (Vg _(k-1) −Vt) Vds _(k) −Vds _(k) ² } Equation (1)
It becomes. Here, Vg is a gate voltage, Vt is the threshold voltage, Vds is the drain-source voltage, beta is a constant determined by the manufacturing process of the transistor T _k.

Since this ΔId is a current change per 1 LSB, the current change ΔIout per channel (mLSB) is
ΔIout = Σ ⁿ _{L = 1} 2 ^L−1・ Dk (L) ・ ΔId ・ ・ ・ Equation (2)
It becomes. So that the current flowing through the value to the transistor T _k as a peak value gradually changes.

  Due to this transient current change, the amount of voltage drop generated in the load 5 changes, and noise is generated in the output voltage.

For example, when a light emitting diode is used as the load 5, the peak value ΔVout of the generated noise is
ΔVout = kT / q · ln (ΔIout / Is) + ΔIout · r _d Equation (3)
It becomes. Here, r _d is the internal resistance of the light emitting diode.

On the other hand, when the precharge circuit 6 is provided, the current Ip flowing through the precharge circuit 6 is
Ip ＝ Iref ・ Rref / Rp (4)
It can be expressed.

Here, regarding the transistor Tp, the gate voltage Vg _(p) in the non-saturated state is
_{Vg (p) = 1 / (} 2 · Vds) · (Ip / mg (p) · 1 / K (p) + Vds 2) + Vt (p) ··· (5)
The gate voltage Vg _(p) in the saturation state is
Vg _(p) = (Ip / mg _(p) · 1 / K _(p) ) ^1/2 + Vt _(p) (6)
It becomes.

In the above equation, the resistor Rp is set to 1/100 of Rref, the size mg _(p) of the transistor Tp is set to 1/100 of the other transistors T1 to Tn, and the current Ip is set to LSB / 100 In this case, if the current at 1 LSB is I,
Vg _(p) = 1 / (2 · Vds) · (I / K _(p) + Vds ² ) + Vt _(p) (7)
And in saturation,
Vg _(p) = (I / K _(p) ) ^1/2 + Vt _(p) (8)
It becomes.

Further, the gate voltage Vg _(n) of the transistors T1 to Tn in the current output circuit 2 is not saturated.
Vg _(n) = 1 / (2 · Vds) · (I / K _(n) + Vds ² ) + Vt _(n) (9)
And in saturation,
Vg _(n) = (I / K _(n) ) ^1/2 + Vt _(n) (Equation 10)

  Here, when the equations (7) and (9), and the equations (8) and (10) are compared, the difference between them is the values of K and Vt, only the values specific to the transistors, and the precharge circuit 6 This is only a difference in value due to relative variation between the transistor Tp of the transistor T1 and the transistors T1 to Tn of the current output circuit 2.

  Therefore, after the precharge circuit 6 is operated, even if the current output circuit 2 operates in a non-saturated state or a saturated state, the control signal S3 is transmitted to the transistors T1 to Tn of the current output circuit 2 regardless of the state. The required gate voltage can be made almost the same voltage, and as a result, the transient change of the control signal S3 can be reduced, and the noise peak value expressed by the above equations (2) and (3) can be reduced. The value can be reduced to a value close to zero.

  Note that even if the current flowing through the precharge circuit 6 is set to 1/100 LSB, there is a possibility that the output current is still 0, so when the output current in the current output circuit 2 becomes 0, It is also possible to control the output current to be kept at 0 without operating the precharge circuit 6.

1 is a block diagram schematically showing a multi-channel current output driver circuit according to the present invention. The circuit diagram. The block diagram which showed typically the conventional multichannel current output type driver circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multichannel current output type driver circuit 2 Current output circuit 3 Control circuit 4 Selection circuit 5 Load 6 Precharge circuit 7 Gate terminal 8 Reference terminal 9 Detection terminal T Transistor R Resistance S Switch C Capacitor

Claims (6)

Selecting a plurality of current output circuits, one control circuit for controlling the current output from each current output circuit to a predetermined value, and one current output circuit among the plurality of current output circuits A multi-channel current output driver circuit configured to output a current from the current output circuit selected by the selection circuit.
Each current output circuit has a plurality of constant current circuits for supplying different constant currents, and any one or a plurality of constant current circuits are operated simultaneously based on a selection signal selected by the selection circuit. To output current to each light emitting diode,
Each current output circuit has the same configuration as the constant current circuit, and a precharge circuit that outputs a smaller current than each current output circuit is provided in each current output circuit, and a current is supplied from the current output circuit selected by the selection circuit. The multi-channel current output is configured such that the precharge circuit provided in the current output circuit is driven before outputting the current, and the drive of the precharge circuit is stopped when the current is output from the current output circuit. Type driver circuit.   2. The multi-channel current output type driver circuit according to claim 1, wherein a transistor as a constant current source is provided in the current output circuit, and a gate voltage of the transistor is controlled by the control circuit. Selecting a plurality of current output circuits, one control circuit for controlling the current output from each current output circuit to a predetermined value, and one current output circuit among the plurality of current output circuits And a selection circuit connected to the control circuit, and a semiconductor device having a multi-channel current output type driver circuit configured to output current from the current output circuit selected by the selection circuit.
Each current output circuit has a plurality of constant current circuits for supplying different constant currents, and any one or a plurality of constant current circuits are operated simultaneously based on a selection signal selected by the selection circuit. To output current to each light emitting diode,
The multi-channel current output type driver circuit has the same configuration as the constant current circuit of each current output circuit, and a precharge circuit that outputs a smaller current than each current output circuit is provided in each current output circuit, and the selection The precharge circuit provided in the current output circuit is driven before the current is output from the current output circuit selected in the circuit, and the drive of the precharge circuit is stopped when the current is output from the current output circuit . A semiconductor device.   4. The semiconductor device according to claim 3, wherein a transistor as a constant current source is provided in the current output circuit, and a gate voltage of the transistor is controlled by the control circuit. A plurality of light emitting diodes, a current output circuit connected to each light emitting diode, a control circuit for controlling the current output from each current output circuit to a predetermined value, and the plurality of current output circuits. A selection circuit that selects one of the current output circuits and connects to the control circuit, and is configured to turn on the light emitting diode by outputting a current from the current output circuit selected by the selection circuit. In the light emitting diode driving device,
Each current output circuit has a plurality of constant current circuits for supplying different constant currents, and any one or a plurality of constant current circuits are operated simultaneously based on a selection signal selected by the selection circuit. To output current to each light emitting diode,
Each current output circuit has the same configuration as the constant current circuit, and a precharge circuit that outputs a smaller current than each current output circuit is provided in each current output circuit, and a current is supplied from the current output circuit selected by the selection circuit. A light-emitting diode driving device configured to drive a precharge circuit provided in a current output circuit before outputting the current and to stop driving the precharge circuit when current is output from the current output circuit .   6. The light emitting diode driving device according to claim 5, wherein a transistor as a constant current source is provided in the current output circuit, and a gate voltage of the transistor is controlled by the control circuit.

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