JP6628364B2 - Integrated circuit device, fluorescent display tube, display device, power supply stop control method - Google Patents

Description

  The present invention relates to an integrated circuit device provided in a fluorescent display tube, a fluorescent display tube, a display device provided with the fluorescent display tube, and a power supply stop control method thereof, and more particularly to a fluorescent display tube provided in response to a power-off condition being satisfied. The present invention relates to a control technique for stopping a drive voltage generation operation of an anode and a grid.

As a display device for displaying various types of information, a fluorescent display tube (VFD: Vacuum Fluorescent Display) is widely known.
As is well known, in a fluorescent display tube, a filament (directly heated cathode) for emitting electrons and an anode in which a phosphor is formed on an anode electrode for controlling the movement of electrons are arranged in a sealed container. A voltage is applied to the filament to heat it, thereby emitting thermoelectrons. The thermoelectrons collide with the phosphor on the anode, and the anode is turned on. The anodes are arranged in a predetermined pattern, and by selectively applying a driving voltage (DC voltage) to the anodes to be lit, only the phosphors of the anodes are emitted by thermions emitted from the filament. Excitation light is emitted, and required information display is realized.

  Further, as a fluorescent display tube, there is a fluorescent display tube in which a grid for accelerating thermoelectrons emitted from a filament is arranged between the filament and an anode in a sealed container (for example, see Patent Document 1 below). In this case, when the required anode is turned on, a drive voltage is applied to both the anode and a grid provided for the anode.

  In a fluorescent display tube, a logic circuit for selectively applying a drive voltage to an anode to be turned on is provided in an anode drive circuit. The operating voltage (logic voltage) of the logic circuit is relatively low (for example, about 5 V), and the drive voltage of the anode and the grid is higher (for example, about 30 V) than the logic voltage.

  The logic voltage and the drive voltage of the anode and the grid are generated by a power supply circuit provided in a display device equipped with a fluorescent display tube, for example. Alternatively, when a relatively high voltage is required to drive the anode or grid, a booster circuit provided in the fluorescent display tube generates a drive voltage based on an input voltage from the power supply circuit.

  In addition, the following patent document 2 can be mentioned as a related prior art. Patent Document 2 discloses that a rectifying and smoothing circuit that generates a DC voltage V for controlling light emission in a fluorescent display tube includes a smoothing capacitor C.

JP 2007-65074 A JP 2010-72525 A

  Here, in the fluorescent display tube, when the power is turned on or the power is turned off, the above-described logic voltage and drive voltage are turned on and off in a predetermined order. Specifically, in the drive circuit of the anode, since the switching element operated by the logic voltage switches a relatively high driving voltage, the switching element is turned on when the logic voltage is off and the driving voltage is on. Unintended current (hereinafter referred to as “unnecessary current”) may flow. Such an unnecessary current may cause instantaneous erroneous lighting of the anode, and the flow of the unnecessary current is not desirable for improving circuit safety. Therefore, when the power is turned on, the logic voltage is turned on and the drive voltage is turned on, and when the power is turned off, the drive voltage is turned off and the logic voltage is turned off, thereby preventing only the drive voltage from being turned on. ing.

  However, a power supply circuit that generates a drive voltage, or a booster circuit in the case of using a boosted voltage as a drive voltage, includes a smoothing capacitor in an output stage. The drive voltage value does not immediately decrease due to the charge accumulated in the smoothing capacitor, and as a result, a situation may occur in which the drive voltage is turned on while the logic voltage is turned off. In particular, when a boosted drive voltage is used, the amount of charge stored in the smoothing capacitor also increases, so that the possibility of the unnecessary current flowing increases.

  The present invention has been made in view of the above circumstances, and has as its object to prevent unnecessary current from flowing to the anode drive circuit when power is cut off, to prevent false anode lighting, and to improve circuit safety. And

An integrated circuit device according to the present invention includes a filament that emits electrons, an anode in which a phosphor is formed on an anode electrode that controls the movement of the electrons, and an electrode disposed between the anode and the filament. A certain grid, the integrated circuit device in a fluorescent display tube including an anode and an integrated circuit device that controls the driving of the grid, wherein the integrated circuit device operates at a first voltage and is higher than the first voltage. An anode driving unit that applies two voltages as a driving voltage to the anode, a grid driving unit that applies the second voltage as a driving voltage to the grid, and a voltage generation operation of the first voltage and the second voltage. for stop control, the second voltage, when the stop control in the order of the first voltage is performed, the driving of the grid by the grid driving unit After the stop control of the second voltage, in which and a control unit to continue until before the stop control of the first voltage is performed.

Thus, after the stop control of the second voltage, the accumulated charge in the output capacitor for the second voltage is discharged through the grid. Further, it is possible to prevent the first voltage from being stopped before the driving of the grid is stopped.

In the above-described integrated circuit device according to the present invention, the control unit may stop driving the anode by the anode driving unit in response to determining that the stop control of the second voltage is performed. It is possible.

  As a result, it is possible to prevent the anode from lighting due to the discharge through the grid.

  In the above-described integrated circuit device according to the present invention, the control unit may be configured to stop driving the grid after a lapse of a predetermined time from the stop control of the second voltage.

  Thus, the discharge period through the grid is a fixed period.

  In the above-described integrated circuit device according to the present invention, the control unit may be configured to control the drive stop timing of the grid based on the detected value of the second voltage.

  Thus, even when the discharge characteristics via the grid change due to aging or the like, it is possible to prevent the discharge from being stopped until the second voltage value is sufficiently reduced.

In addition, the fluorescent display tube according to the present invention is provided with a filament that emits electrons, an anode in which a phosphor is formed on an anode electrode that controls the movement of the electrons, and disposed between the anode and the filament. A grid that is an electrode, an anode driving unit that operates with a first voltage and applies a second voltage higher than the first voltage as a driving voltage to the anode, and a driving voltage that applies the second voltage to the grid. A grid driving unit to be applied as the control for stopping the voltage generation operation of the first voltage and the second voltage, when the stop control is performed in the order of the second voltage and the first voltage, the grid drive after the stop control of the second voltage drive of the grid due to parts, one and a control unit to continue until before the stop control of the first voltage is performed That.

The display device according to the present invention further includes a filament that emits electrons, an anode in which a phosphor is formed on an anode electrode that controls the movement of the electrons, and an electrode that is disposed between the anode and the filament. A fluorescent display tube having at least a grid, an anode driving unit that operates at a first voltage and applies a second voltage higher than the first voltage as a driving voltage to the anode, and the second voltage And a grid drive unit for applying a drive voltage to the grid as a drive voltage, and for the stop control of the voltage generation operation of the first voltage and the second voltage, the stop control is performed in the order of the second voltage and the first voltage. with, before SL after the stop control of the second voltage drive of the grid by the grid driving unit, a control to continue until before the stop control of the first voltage is performed And, those with a.

In addition, the power supply stop control method according to the present invention includes a filament that emits electrons, an anode in which a phosphor is formed on an anode electrode that controls the movement of the electrons, and is disposed between the anode and the filament. A fluorescent display tube having at least a grid that is an electrode, an anode driving unit that operates at a first voltage and applies a second voltage higher than the first voltage as a driving voltage to the anode, A grid driving unit that applies a voltage as a drive voltage to the grid, and for the stop control of the voltage generation operation of the first voltage and the second voltage, the second voltage, the stop control in the order of the first voltage. and a control unit that performs, a power supply stop control method in the display device wherein the control unit, the driving of the grid by pre Symbol grid driving unit of the second voltage After serial stop control is intended to continue until before the stop control of the first voltage is performed.

  The same operation as the above-described integrated circuit device according to the present invention can be obtained by the fluorescent display tube, the display device, and the power supply stop control method according to the present invention.

  According to the present invention, it is possible to prevent unnecessary current from flowing to the anode drive circuit when the power is cut off, to prevent erroneous lighting of the anode, and to improve circuit safety.

1 is a diagram illustrating a circuit configuration of a display unit including a fluorescent display tube according to an embodiment. It is a figure for explaining the structure of a fluorescent display tube. FIG. 5 is an explanatory diagram of an on / off sequence of a logic voltage and a drive voltage when power is turned on / off. FIG. 3 is a diagram illustrating a configuration example of a drive circuit in an anode driver unit included in the fluorescent display tube according to the embodiment. FIG. 3 is a diagram illustrating an example of an internal configuration of a level shift circuit included in an anode driver unit. FIG. 3 is a diagram illustrating an example of an internal configuration of an output buffer included in an anode driver unit. 6 is a flowchart illustrating a procedure of power stop control as a control example I. FIG. 9 is a diagram for describing an effect of the power supply stop control according to the embodiment. FIG. 9 is a diagram showing a configuration example of a display unit for implementing power stop control as control example II. 9 is a flowchart illustrating a procedure of power stop control as a control example II. It is explanatory drawing about the modification concerning the structure of a fluorescent display tube. Similarly, it is explanatory drawing about the modification concerning the structure of a fluorescent display tube.

Hereinafter, embodiments of the present invention will be described.
The description will be made in the following order.
<1. Display Unit Configuration>
<2. Power supply stop control as embodiment>
[2-1. Control Example I]
[2-2. Control example II]
<3. Modification Example of Configuration of Fluorescent Display Tube>
<4. Summary of Embodiment>
<5. Other Modifications>

<1. Display Unit Configuration>

FIG. 1 is a diagram showing a circuit configuration of a display unit 100 including a fluorescent display tube 1 as an embodiment. In the following description, the fluorescent display tube may be described as "VFD" (Vacuum Fluorescent Display).

The display unit 100 includes a fluorescent display tube 1, a microcomputer (microcomputer) 101, a power supply circuit 102, a resistor Ro, capacitors Cc1 and Cc2, and a smoothing capacitor Ch.
The microcomputer 101 is configured as a microcomputer including, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and controls the display operation of the fluorescent display tube 1. The microcomputer 101 supplies an n-system (n is a natural number of 2 or more) digital signals to the fluorescent display tube 1 for controlling the display operation.

  The power supply circuit 102 generates an input voltage VIN to be supplied to an integrated circuit device 2 described later provided in the fluorescent display tube 1 and a logic voltage VDD based on an input voltage (not shown). In this example, VIN = about 12 V and VDD = about 5 V.

  The fluorescent display tube 1 includes an integrated circuit device 2 configured as an IC (Integrated Circuit) chip, a display unit 3 for displaying information by light emission, and a plurality of lead terminals T.

Here, the structure of the fluorescent display tube 1 will be described with reference to FIG. 2A is a schematic perspective view showing a part of the fluorescent display tube 1 in a see-through manner, and FIG. 2B is a schematic sectional view of the fluorescent display tube 1 taken along the line AA ′ in FIG. 2A.
The fluorescent display tube 1 includes a sealed container 1c composed of a display tube substrate 1a and a cover member 1b covering the surface of the display tube substrate 1a. In the sealed container 1c, a filament (directly heated cathode) Fi, an anode An and A display unit 3 having a grid Gr is formed. Here, the inside of the sealed container 1c is in a vacuum state.

  In the display unit 3, a plurality of filaments Fi that emit electrons are provided (black circles in FIG. 2B). The anode An is formed by forming a phosphor on an anode electrode for controlling electrons emitted from the filament Fi. The anodes An are formed on the display tube substrate 1a by, for example, pattern printing, and are arranged in a predetermined pattern according to information to be displayed. Hereinafter, a portion in which the plurality of anodes An are arranged in a predetermined pattern is referred to as an “anode pattern portion 3a”.

The fluorescent display tube 1 of the present example is capable of displaying information in a predetermined unit, such as one digit or one character in the case of information such as characters and numerals. In the example of FIG. 2, the display area for the predetermined unit is formed by seven segments of anodes An (seven independent anodes An) capable of displaying a single numeral or alphabet. Such a display area for a predetermined unit is hereinafter referred to as a “display block”. In the anode pattern section 3a, a plurality of such display blocks are arranged on the display tube substrate 1a. Specifically, in this example, the display blocks are arranged in a line on the display tube substrate 1a.
In the display block, the arrangement pattern of the anodes An for seven segments as shown in FIG. 2A is merely an example, and the arrangement pattern of the anodes An forming the display block is not limited to this pattern.

  The grid Gr is a mesh-like electrode for accelerating electrons emitted from the filament Fi to the anode An, and is formed for each display block.

  A plurality of lead terminals T are formed on the display tube substrate 1a. These lead terminals T are used to input various electric signals (digital signals, power supply voltage, etc.) required for driving the filament Fi, the anode An, and the grid Gr from outside the fluorescent display tube 1. T is included. A lead made of a conductor is connected to each lead terminal T, and an electrical connection to the outside of the fluorescent display tube 1 is made via the lead.

In the fluorescent display tube 1, the cover member 1b is made of, for example, glass, and at least a portion facing the display tube substrate 1a is transparent. That is, it is possible to externally view display information accompanying the lighting of the anode An through the transparent portion.
The surface of the fluorescent display tube 1 on which information is displayed (that is, the surface of the transparent portion opposite to the surface facing the anode An) is referred to as “surface S1”. The surface of the fluorescent display tube 1 opposite to the front surface S1 is referred to as “back surface S2”.

  In the fluorescent display tube 1, when displaying information on a desired display block among the display blocks in the anode pattern section 3a, a grid provided corresponding to the display block in a state where a driving voltage is applied to the filament Fi. A DC voltage is applied to Gr and a predetermined anode An in the display block. Thus, only the phosphor at the predetermined anode An in the display block is excited and emitted by the thermoelectrons emitted from the filament Fi, and the display of information is realized.

The description returns to FIG.
In the fluorescent display tube 1, a drive circuit for driving the anode An and the grid Gr of the display unit 3 shown in FIG. 2 is provided in the integrated circuit device 2.
Although not shown in FIG. 2, in the fluorescent display tube 1, the integrated circuit device 2 is mounted on the display tube substrate 1 a and is located together with the display unit 3 in a closed space. That is, the fluorescent display tube 1 is configured as a so-called CIG (Chip In Glass) -VFD.

  The integrated circuit device 2 includes a controller 2a, a booster 20, an anode driver 25, a grid driver 26, an anode terminal 27, and a grid terminal 28. The anode terminal unit 27 and the grid terminal unit 28 comprehensively represent a plurality of terminals necessary for the anode driver unit 25 and the grid driver unit 26 to drive each anode An and each grid Gr. .

The controller 2a includes an I / F decoder 21, an oscillator 22, a memory 23, and a timing control unit 24, and controls operations of the boosting unit 20, the anode driver unit 25, and the grid driver unit 26.
Note that the controller 2a of this example has a power supply control unit 29, which will be described later.

Here, in the fluorescent display tube 1, n digital signal lead terminals Tif (Tif1 to Tifn) for the I / F decoder 21 to input the above-mentioned n-system digital signals from the microcomputer 101, and the above-described resistors An oscillator lead terminal Tosc for connecting Ro to the oscillator 22 is formed. The resistor Ro is inserted between the ground and the oscillator lead terminal Tosc.
The fluorescent display tube 1 has an input voltage lead terminal Tvi for inputting the above-described input voltage VIN to the booster 20 and a logic voltage lead terminal Tvd for inputting the above-described logic voltage VDD to the integrated circuit device 2. And a ground lead terminal Tgnd as a ground terminal of the integrated circuit device 2 and a filament lead terminal Tf (Tf1, Tf2) for applying a drive voltage to the filament Fi in the display unit 3. Although not shown, the driving voltage of the filament Fi is generated by a corresponding power supply circuit provided in the display unit 100, for example. In this example, the driving voltage of the filament Fi is a DC voltage.

  Further, the fluorescent display tube 1 is provided with capacitor lead terminals Tc11, Tc12, Tc21, Tc22 for connecting the above-mentioned capacitors Cc1, Cc2 and the smoothing capacitor Ch to the booster 20, respectively, and an output voltage lead terminal Tch. ing. As shown, the capacitor Cc1 is inserted between the capacitor lead terminals Tc11 and Tc12, the capacitor Cc2 is inserted between the capacitor lead terminals Tc21 and Tc22, and the smoothing capacitor Ch is inserted between the output voltage lead terminal Tch and the ground. Have been.

  Here, the arrangement positions of the lead terminals T shown in FIG. 1 do not always reflect the actual arrangement positions.

In the integrated circuit device 2, the booster 20 in this example constitutes a charge pump type booster circuit together with the capacitors Cc1 and Cc2 and the smoothing capacitor Ch, and boosts the input voltage VIN input from the input voltage lead terminal Tvi. The obtained output voltage Vo is obtained as a voltage across the smoothing capacitor Ch. The booster 20 of this embodiment obtains an output voltage Vo having a voltage value that is approximately three times the input voltage VIN (approximately 36 V in this example) by using the capacitors Cc1 and Cc2 and the smoothing capacitor Ch. Although not shown, the booster 20 of this example has switches provided for each of the capacitors Cc1 and Cc2 and the smoothing capacitor Ch, and the on / off operation of the switches causes the following first phase to be performed. The second phase is configured to be alternately repeated. That is, the first phase is a phase in which the charge corresponding to approximately one time the input voltage VIN is accumulated in the capacitor Cc1, and the charge of the capacitor Cc2 is discharged to the smoothing capacitor Ch. The second phase is a phase in which the charge corresponding to the sum of the charge of the capacitor Cc1 and the input voltage VIN added to the capacitor Cc2 (that is, the charge of approximately twice the input voltage VIN) is accumulated.
Note that the configuration of the booster circuit can employ various configurations for performing a known boosting operation, and is not limited to a specific configuration.

  The output voltage Vo from the booster 20 is supplied to the anode driver 25 and the grid driver 26 as drive voltages for the anode An and the grid Gr, respectively.

  In the present embodiment, the booster 20, that is, the circuit part excluding the capacitors Cc 1 and Cc 2 and the smoothing capacitor Ch among the components of the charge pump type booster circuit is built in the fluorescent display tube 1 side because of the display. This is to reduce the circuit mounting burden on the manufacturer of the unit 100, that is, on the customer side who mounts the fluorescent display tube 1 on the display unit 100. In other words, on the customer side in this case, it is not necessary to mount the entire booster circuit on the substrate on which the fluorescent display tube 1 is mounted, and only the capacitors Cc1 and Cc2 and the smoothing capacitor Ch need be mounted.

The I / F decoder 21 has a logic circuit in which a shift register, a counter, an AND circuit, an OR circuit, and the like (not shown) are combined, and n systems input from the microcomputer 101 via digital signal lead terminals Tif1 to Tifn. Based on the digital signal and the oscillation signal output from the oscillator 22, display data is written to the memory 23 composed of, for example, a RAM, and the operation of the timing control unit 24 is controlled.
In this example, at least the chip select signal CS, the clock CLK, and the data signal DAT are supplied from the microcomputer 101 as n-system digital signals. The data signal DAT is, for example, serial data having 8 bits as one word, and includes display data indicating which anode An should be turned on, and control data for adjusting a timing signal output by the timing control unit 24. including. The I / F decoder 21 sequentially takes in each bit value of the data signal DAT in word units according to the chip select signal CS and the clock CLK. Based on the display data obtained from the data signal DAT by this capture, the I / F decoder 21 obtains a value representing lighting / non-lighting for each anode An (hereinafter, referred to as a “lighting control value”), and obtains a value for each anode An. The lighting control value is written to the corresponding address in the memory 23. Further, the I / F decoder 21 outputs control data to the timing control unit 24 based on the taken data signal DAT.

The timing control unit 24 controls the output timing of the lighting control value from the memory 23 to the anode driver unit 25 based on the oscillation signal output from the oscillator 22 and the control data from the I / F decoder 21, Output timing control of the drive voltage of the anode An and output timing control of the drive voltage of the grid Gr by the grid driver unit 26 are performed. The output of the lighting control value from the memory 23 to the anode driver unit 25 is performed for each anode An. In the figure, the lighting control value for each anode An is represented as “Ma1 to Man”.
Further, the timing control section 24 of the present example also controls the on / off timing of each switch in the boosting section 20 described above.

In this example, while sequentially applying a drive voltage to each grid Gr formed for each display block, a drive voltage is applied to the anode An in the display block in which the grid Gr is being driven, and during a predetermined one scan period, A scan display system in which each display block is sequentially turned on is adopted.
For this reason, the timing control unit 24 generates a timing signal as a “scan signal” representing the ON / OFF timing of each grid Gr based on the control data described above, and transmits the scan signal to the grid driver unit. 26. The grid driver 26 sequentially applies the output voltage Vo from the booster 20 as a drive voltage to each grid Gr via the grid terminal 28 according to the scan signal.
Further, the timing control unit 24 outputs a timing signal synchronized with the driving timing of the grid Gr to the memory 23 and the anode driver unit 25, and sequentially outputs the lighting control value for each anode An from the memory 23 to the anode driver unit 25. At the same time, it instructs the anode driver 25 to drive the anode An. Hereinafter, the signal indicating the drive timing of the anode An is referred to as a “drive timing signal Tm”.
Based on the lighting control values sequentially output from the memory 23 and the drive timing signal Tm from the timing control unit 24, the anode driver unit 25 outputs the output voltage Vo to the anode An to be illuminated, as described above. A drive voltage is applied via the switch 27. Thereby, information display according to the instruction from the microcomputer 101 is performed on the display unit 3.
In the figure, each signal line for individually applying a drive voltage to each anode An is represented as “Sa1 to San”.

<2. Power supply stop control as embodiment>
[2-1. Control Example I]

Here, the anode driver unit 25 has a logic circuit for outputting the output voltage Vo as a corresponding drive voltage of the anode An based on the lighting control value and the drive timing signal Tm. The logic circuit operates by the logic voltage VDD. Specifically, the logic circuit includes a switching element that operates by the logic voltage VDD, and the switching element switches a relatively high output voltage Vo (anode driving voltage).
For this reason, in the logic circuit, if the output voltage Vo is on while the logic voltage VDD is off, an unintended current (hereinafter referred to as “unnecessary current”) flows through the switching element.

  The generation of such unnecessary current should be prevented in terms of circuit safety and the like. Therefore, in the present embodiment, as shown in FIG. 3, when the power is turned on, the logic voltage VDD is turned on, and then the output voltage Vo is turned on. Is turned on, and when the power supply is cut off, the output voltage Vo is turned off, and then the logic voltage VDD is turned off.

This control is performed by the microcomputer 101 shown in FIG.
First, the microcomputer 101 notifies the fluorescent display tube 1 side of the timing of power-on or power-off of the display unit 100 based on, for example, an operation input by a user using a power notification signal Si. As shown in FIG. 1, the fluorescent display tube 1 is provided with a power notification terminal Ti, and the power notification signal Si is input from the microcomputer 101 to the power control unit 29 via the power notification terminal Ti. The significance of the power notification signal Si input to the power control unit 29 via the power notification terminal Ti will be clarified later.

The microcomputer 101 causes the power supply circuit 102 to sequentially start the operation of generating the logic voltage VDD and the operation of generating the input voltage VIN at the ON timing of the logic voltage VDD and the output voltage Vo as shown in FIG. Thus, when the power is turned on, the logic voltage VDD is turned on before the output voltage Vo.
Then, in response to the power-off operation, the microcomputer 101 sequentially performs the generation operation of the input voltage VIN and the generation operation of the logic voltage VDD by the power supply circuit 102 at the off timing of the output voltage Vo and the logic voltage VDD as shown in FIG. Stop. At this time, the microcomputer 101 performs control to stop the operation of generating the logic voltage VDD after a lapse of a predetermined time after performing control to stop the operation of generating the input voltage VIN.

However, even when the output voltage Vo is turned off earlier than the logic voltage VDD as described above when the power supply is cut off, the smoothing capacitor provided in the output stage of the circuit that generates the output voltage Vo (the smoothing capacitor Ch in this example). Due to the action of ()), the voltage value of the output voltage Vo does not immediately decrease. Therefore, there is a possibility that a period during which the potential of the output voltage Vo is not sufficiently reduced after the logic voltage VDD is turned off, as in a period X illustrated in FIG. That is, the output voltage Vo is turned on while the logic voltage VDD is turned off.
When the boosted output voltage Vo is used as in this example, the period X becomes longer because the amount of charge stored in the smoothing capacitor increases. That is, the above unnecessary current is more easily generated.

Here, the principle of generation of the unnecessary current and an example of the generation position will be described with reference to FIGS.
FIG. 4 shows an example of a drive circuit configuration in the anode driver unit 25. In FIG. 4, only the drive circuit for one anode An is extracted and shown. Here, the anode An to be driven by the drive circuit is “Anx”, and various signals (values) related to the drive of the anode Anx and “x” are added to the end of the code of the signal line.

  As illustrated, the drive circuit in the anode driver unit 25 includes a logic circuit 25a, a level shift circuit 25b, and an output buffer 25c. The logic circuit 25a and the level shift circuit 25b are supplied with a logic voltage VDD as an operation voltage, and the output buffer 25c is supplied with an output voltage Vo as an operation voltage.

  The logic circuit 25a is configured as, for example, an AND gate circuit, receives the lighting control value Max for the anode Anx from the memory 23, receives the drive timing signal Tm from the timing control unit 24, and outputs both signals as the output signal Lox. When the input is "1", a signal representing logic "1" is outputted, otherwise, a signal representing logic "0" is outputted.

The level shift circuit 25b has a function of inverting the output signal Lox by the logic circuit 25a and a function of shifting (converting) the voltage value of the output signal Lox (the voltage value at the time of the high level) to the voltage value of the output voltage Vo. Have.
As shown in FIG. 5, the level shift circuit 25b includes an inverting amplifier circuit 40 and a non-inverting amplifier circuit 41 that obtain a signal obtained by inverting and non-inverting the output signal Lox from the logic circuit 25a using the logic voltage VDD as an operating voltage. And a switching element Q2 composed of an Nch (channel) MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) whose gate is supplied with the output signal of the inverting amplifier circuit 40 and whose source is connected to the ground, and a non-inverting amplifier circuit 41. Is supplied to the gate, and the source is connected to the ground. These switching elements Q2 and Q4 are turned on complementarily (alternately) in accordance with the High level ("1") and the Low level ("0") of the output signal Lox. The level shift circuit 25b has a gate connected to the drain of the switching element Q4, a drain connected to the drain of the switching element Q2, a switching element Q1 of a Pch MOSFET connected to the drain of the switching element Q2, and a gate connected to the drain of the switching element Q2; The drain has a switching element Q3 of a Pch MOSFET connected to the drain of the switching element Q4, and the output voltage Vo is supplied as an operating voltage to the sources of the switching elements Q1 and Q3, respectively.
Thereby, as the output signal Lex of the level shift circuit 25b obtained at the connection point between the drains of the switching element Q3 and the switching element Q4, the output signal Vo has the inversion relationship with the output signal Lox and the voltage value at the time of the High level is the voltage of the output voltage Vo. A value shifted signal is obtained. That is, when the output signal Lox is at a high level, the switching element Q4 is turned on by applying an on-voltage to the switching element Q4, and the switching elements Q2 and Q3 are both turned off. A low-level signal is output as Lex. On the other hand, when the output signal Lox is at a low level, the switching element Q2 is turned on by applying an ON voltage to the switching element Q2, and the switching elements Q4 and Q1 are both turned off. As the signal Lex, a High-level signal having a voltage value equal to the output voltage Vo is output.

  The output buffer 25c includes, as shown in FIG. 6, a switching element Q5 of a P-channel MOSFET whose source is supplied with the output voltage Vo as an operating voltage, and an Nch whose drain is connected to the drain of the switching element Q5 and whose source is connected to the ground. And a push-pull circuit formed by a switching element Q6 of a MOSFET. The output signal Lex from the level shift circuit 25b is input to the gates of the switching elements Q5 and Q6, and these switching elements Q5 and Q6 are turned on complementarily according to the High level and Low level of the output signal Lex. As a result, at the output point of the push-pull circuit (the connection point between the drains of Q5 and Q6), when the output signal Lex is at the Low level, the output voltage Vo is at the High level due to the same value, and when the output signal Lex is at the High level. Obtains a signal of a low level, and the signal is supplied to the anode Anx via the signal line Sax.

In the state where the logic voltage VDD is turned off (falled) in the anode driver section 25 as described above, in the level shift circuit 25b shown in FIG. 5, the inversion which is the drive control signal of the switching elements Q2 and Q4 is performed. The voltage values of the output signals of the amplifier circuit 40 and the non-inverting amplifier circuit 41 become indefinite, respectively. If the output voltage Vo is not completely turned off in the state where the voltage values of the output signals of the inverting amplifier circuit 40 and the non-inverting amplifier circuit 41 are indefinite, all of the switching elements Q1 to Q4 are set to the half-on state. May be lost.
When the switching elements Q1 to Q4 are in the half-on state, the output signal Lex of the level shift circuit 25b, that is, the voltage value of the input signal to the output buffer 25c shown in FIG. There is a risk that both switching elements Q5 and Q6 of buffer 25c may be in a half-on state.

  As described above, in the level shift circuit 25b and the output buffer 25c, when the logic voltage VDD falls when the output voltage Vo is not completely turned off, the switching elements Q1 to Q4 and the switching elements Q5 and Q6 simultaneously There is a possibility that it will be turned on. If the output voltage Vo is not completely turned off while the switching elements Q1 to Q4 and the switching elements Q5 and Q6 are turned on at the same time, the through current flows in the directions indicated by arrows K in FIGS. Flows. This through current may cause the switching elements Q1 to Q6 to deteriorate or fail, and may also cause instantaneous erroneous lighting of the anode An.

  For this reason, in the present embodiment, the power supply stop control described below prevents the occurrence of the through current as the unnecessary current as described above, and prevents the deterioration and failure of the switching element in the anode driver unit 25. In addition, the safety of the circuit is improved, and the false lighting of the anode An due to the flow of the through current is prevented.

Hereinafter, a control example I of the power stop control performed by the power control unit 29 will be described with reference to a flowchart of FIG.
First, in step S101, the power supply control unit 29 waits for power-off. That is, it waits until the microcomputer 101 notifies the microcomputer 101 of the power shutdown by the power notification signal Si described above.

  In the following step S102, the power supply control unit 29 turns off the anode An. That is, the driving of all the anodes An is stopped. Specifically, the power supply control unit 29 of the present example controls so that a value “0” (that is, a lighting control value representing “non-lighting”) is written to each address in the memory 23 for each anode An.

  In response to turning off the anode in step S102, the power supply control unit 29 waits until a certain time has elapsed in step S103. Specifically, in this example, the process waits until one second elapses after the notification of step S101.

  After the elapse of the predetermined time, the power supply control unit 29 turns off the grid scan in step S104. That is, a control signal for stopping the scan of the grid Gr by the grid driver unit 26 is output to the timing control unit 24.

Here, as described above, the microcomputer 101 performs the stop control of the generation operation of the input voltage VIN in response to the power-off operation being performed, and at the same time, the power-off notification by the power-on notification signal Si. Go to section 29.
Then, the power supply control unit 29 performs the scan stop control of the grid after a lapse of a predetermined time after receiving the notification of the power shutdown by the power notification signal Si as described above. In other words, this corresponds to stopping the driving of the grid after a lapse of a predetermined time from the stop control of the output voltage Vo.

Further, as described above, the microcomputer 101 performs the stop control of the logic voltage VDD according to the elapse of a predetermined time after performing the stop control of the input voltage VIN. In other words, the stop control of the logic voltage VDD is performed in response to a lapse of a predetermined time from substantially the same timing as the power shutdown notification to the power control unit 29 by the power notification signal Si.
Here, in the present example, the above-mentioned “constant time” during which the microcomputer 101 waits until the control of stopping the logic voltage VDD is slightly longer than the “fixed time” during which the power supply control unit 29 waits in step S103. Therefore, the stop control of the logic voltage VDD is executed after the grid scan by the power supply control unit 29 is stopped. In other words, in other words, the power supply control unit 29 stops the scan of the grid before the stop control of the logic voltage VDD is performed.

As described above, in the power stop control according to the embodiment, the stop control of the voltage generation operation is performed in the order of the output voltage Vo and the logic voltage VDD in accordance with satisfaction of a predetermined power cutoff condition such as a power cutoff operation by a user. . Then, in such an off sequence, the power supply control unit 29
Even after the stop control of the output voltage Vo is performed, the driving of the grid is continued.
Thus, after the stop control of the output voltage Vo, the accumulated charge in the output capacitor (smoothing capacitor Ch) for the output voltage Vo is discharged via the grid Gr.
Therefore, the voltage value of the output voltage Vo can be quickly reduced after the stop control of the output voltage Vo, and an unnecessary current can be prevented from flowing through the drive circuit when the power supply of the fluorescent display tube 1 is cut off, so that erroneous anode lighting is prevented. Thus, prevention and improvement of circuit safety can be achieved.

In the present embodiment, after the stop control of the output voltage Vo, the driving of the grid Gr is stopped before the stop control of the logic voltage VDD is performed. This prevents the logic voltage VDD from being stopped before the driving of the grid Gr is stopped.
Therefore, the safety of the driving circuit in the grid driver unit 26 is improved.

In the power supply stop control of the embodiment, the driving of the grid Gr is stopped after a lapse of a predetermined time from the stop control of the output voltage Vo.
As a result, the discharge period via the grid Gr is a fixed period, and therefore, the circuit related to the drive stop control of the grid Gr can be realized by a simple configuration in which a certain fixed period is awaited.

Here, in the present example, the anode An is turned off in advance in step S102, that is, the anode An is turned off in advance in accordance with the establishment of the power-off condition. However, the discharge of the output voltage Vo via the grid Gr is prevented. Accordingly, it is possible to prevent the anode An from being erroneously turned on.
It is not desirable from the viewpoint of display quality that the anode An is erroneously turned on when the power is cut off. Therefore, the off control of the anode An leads to improvement in display quality.

  FIG. 8 is a diagram for explaining the effect of the power supply stop control of the embodiment. FIG. 8A shows a case where the power supply stop control of the embodiment is not performed (a sequence of turning off the logic voltage VDD after the output voltage Vo is turned off). FIG. 8B shows the change characteristics of the output voltage Vo when the power is turned off when the power stop control according to the embodiment is performed.

8A and 8B, the period from the stop control timing of the output voltage Vo indicated by “t1” in the figures to the time when the voltage value of the output voltage Vo falls below a predetermined threshold Th lower than the voltage value of the logic voltage VDD. Are represented as “S1” and “S2”, respectively.
According to the comparison between these periods S1 and S2, according to the power supply stop control of the embodiment, in lowering the voltage value of the output voltage Vo to a level sufficiently low to prevent the deterioration and failure of the switching element in the drive circuit, The required time can be greatly reduced.

[2-2. Control example II]

In the above control example I, an example is given in which the period of the discharge via the grid Gr is a fixed period. However, in the control example II, the drive stop timing of the grid Gr is controlled based on the detected value of the output voltage Vo. It is.

FIG. 9 is a diagram illustrating a configuration example of a display unit 100A for implementing power stop control as control example II.
In the following description, the same parts as those already described are denoted by the same reference numerals and step numbers, and description thereof will be omitted.

As shown in the figure, the display unit 100A includes a fluorescent display tube 1A instead of the fluorescent display tube 1, and a microcomputer 101A instead of the microcomputer 101.
The fluorescent display tube 1A includes an integrated circuit device 2A instead of the integrated circuit device 2, and is different from the fluorescent display tube 1 in that a power supply control terminal Tp and a detection unit 30 are added. The fluorescent display tube 1A includes a controller 2aA instead of the controller 2a, and the controller 2a includes a power control unit 29A instead of the power control unit 29.

  The power control terminal Tp is a terminal for the power control unit 29A to output a power control signal Sp to the microcomputer 101A side. The power supply control signal Sp is a signal for instructing the microcomputer 101A side at least to turn off the input voltage VIN.

  When the microcomputer 101A performs the stop control of the input voltage VIN in accordance with the satisfaction of the power supply cutoff condition, the microcomputer 101A does not perform the stop control of the logic voltage VDD in accordance with the elapse of a predetermined time as in the case of the microcomputer 101. The stop control of the logic voltage VDD is performed at the timing specified by the power supply control signal Sp from 29A.

  The detection unit 30 detects a voltage value of the output voltage Vo. The detection value of the output voltage Vo by the detection unit 30 is input to the power control unit 29A.

FIG. 10 is a flowchart illustrating a procedure of power stop control as control example II performed by the power control unit 29A.
As can be seen from a comparison with FIG. 7, the power supply control unit 29A in the control example II responds to turning off the anode An in step S102, and in step S201, determines the voltage value of the output voltage Vo (by the detection unit 30). Wait until the detected value falls below the threshold Th.
If the voltage value of the output voltage Vo is lower than the threshold Th, the power supply control unit 29A turns off the grid scan in step S104. Then, the power supply control unit 29A turns off the logic voltage VDD in step S202. That is, the microcomputer 101A is instructed by the power supply control signal Sp to perform stop control of the logic voltage VDD. Thus, the operation of generating the logic voltage VDD by the power supply circuit 102 is stopped.

As described above, the power supply control unit 29A in the control example II controls the drive stop timing of the grid Gr based on the detected value of the output voltage Vo.
Thus, even when the discharge characteristics via the grid Gr change due to, for example, aging, the discharge can be prevented from being stopped until the voltage value of the output voltage Vo is sufficiently reduced. Therefore, the effect of preventing unnecessary current from flowing to the drive circuit when the power is cut off can be enhanced, and the effect of preventing erroneous anode lighting and the circuit safety can be further improved.

<3. Modification Example of Configuration of Fluorescent Display Tube>

In the above description, an example has been given in which the control entity (the “control unit”) for performing power supply stop control according to the embodiment is provided in an IC having a drive circuit for the anode and the grid, but the control unit is provided inside the fluorescent display tube. , Can be provided outside the IC having the driving circuit therein.

  Alternatively, the control unit can be provided outside the fluorescent display tube. That is, the control unit may be provided at least in a display device having a fluorescent display tube.

For example, FIG. 11 shows a configuration example of a display unit 100B in which the controller 2a including the power supply control unit 29 is provided outside the fluorescent display tube. In this case, the fluorescent display tube 1B is provided with an integrated circuit device 2B having a configuration in which the booster 20 and the controller 2a are omitted from the integrated circuit device 2 shown in FIG. In this case, a power supply circuit 102A having a boosting function is provided instead of the power supply circuit 102, and the output voltage Vo is generated by the power supply circuit 102A.
Note that it is of course possible to adopt a configuration in which the fluorescent display tube 1B is provided with a boosting unit, such as the integrated circuit device 2B having the boosting unit 20.

  FIG. 12 shows a configuration example of a display unit 100C including a fluorescent display tube 1C of a type in which the anode driver unit 25 and the grid driver unit 26 are externally attached. In this case, the controller 2a is also provided outside the fluorescent display tube 1C.

Note that the control unit that performs the power stop control according to the embodiment may be the microcomputer 101. In that case, the power supply control unit 29 (or 29A) in the controller 2a is omitted.

<4. Summary of Embodiment>

As described above, the integrated circuit device (2 or 2A) of the embodiment includes a filament (Fi) that emits electrons, an anode (An) in which a phosphor is formed on an anode electrode that controls the movement of electrons, and An integrated circuit device in a fluorescent display tube comprising: a grid (Gr), which is an electrode disposed between an anode and a filament; and an integrated circuit device that controls driving of the anode and the grid, wherein the first voltage ( A second voltage (output voltage Vo) higher than the first voltage and applied to the anode as a driving voltage, and an anode driver (anode driver 25) that operates with the logic voltage VDD) and applies the second voltage to the grid. After the grid driving unit (grid driver unit 26) that applies the driving voltage and the stop control of the voltage generation operation of the second voltage are performed according to the satisfaction of the power-off condition Oite also includes control unit to continue driving of the grid by the grid driving unit and the (power control unit 29 or 29A), a.

Thus, after the stop control of the second voltage, the accumulated charge in the output capacitor for the second voltage is discharged through the grid.
Therefore, the second voltage value can be rapidly reduced after the stop control of the second voltage, preventing unnecessary current from flowing to the drive circuit when the power is shut off, preventing erroneous anode lighting and improving circuit safety. Can be achieved.

  Further, in the integrated circuit device according to the embodiment, the control unit stops the driving of the grid after the stop control of the second voltage and before the stop control of the voltage generation operation of the first voltage.

This prevents the first voltage from being stopped before the driving of the grid is stopped.
Therefore, the safety of the driving circuit in the grid driving unit can be improved.

  Further, in the integrated circuit device according to the embodiment, the control unit stops driving of the anode by the anode driving unit in accordance with satisfaction of the power supply cutoff condition.

As a result, it is possible to prevent the anode from lighting due to the discharge through the grid.
Therefore, erroneous lighting of the anode when the power is shut off can be firmly prevented, and the display quality can be improved.

  Furthermore, in the integrated circuit device according to the embodiment, the control unit (power supply control unit 29) stops driving the grid after a lapse of a fixed time from the stop control of the second voltage.

Thus, the discharge period through the grid is a fixed period.
Therefore, a circuit related to the grid drive stop control can be realized with a simple configuration.

  In the integrated circuit device according to the embodiment, the control unit (power supply control unit 29A) controls the grid drive stop timing based on the detected value of the second voltage.

Thus, even when the discharge characteristics via the grid change due to aging or the like, it is possible to prevent the discharge from being stopped until the second voltage value is sufficiently reduced.
Therefore, the effect of preventing unnecessary current from flowing to the drive circuit when the power is cut off can be enhanced, and the effect of preventing erroneous anode lighting and the circuit safety can be further improved.

  In addition, the fluorescent display tube (1 or 1A) of the embodiment is provided with a filament for emitting electrons, an anode having a phosphor formed on an anode electrode for controlling the movement of electrons, and an anode and a filament. An anode driving unit that operates with the first voltage, applies a second voltage higher than the first voltage to the anode as a driving voltage, and applies the second voltage as a driving voltage to the grid. And a control unit for continuing the driving of the grid by the grid driving unit even after the stop control of the voltage generation operation of the second voltage is performed in accordance with the establishment of the power cutoff condition.

  Further, the display device (display unit 100, 100A, 100B, or 100C) of the embodiment includes a filament that emits electrons, an anode in which a phosphor is formed on an anode electrode that controls the movement of electrons, and an anode. A fluorescent display tube (1, 1A, 1B, or 1C) having at least a grid that is an electrode disposed between the filament and a filament; and a second voltage that is operated by the first voltage and that is higher than the first voltage. An anode driver for applying a drive voltage to the anode, a grid driver for applying the second voltage as a drive voltage to the grid, and a voltage in the order of the second voltage and the first voltage in accordance with the establishment of the power-off condition A control unit (the power supply control unit 29 and the power supply control unit 29) that performs the stop control of the generation operation and continues the driving of the grid by the grid drive unit even after the stop control of the second voltage. Icons 101, or the power supply control unit 29A and the microcomputer 101A), and a.

With the fluorescent display tube and the display device of these embodiments, the same operation and effect as those of the integrated circuit device of the above-described embodiment can be obtained.

<5. Other Modifications>

The embodiments of the present invention have been described above, but the present invention is not limited to the specific examples described above.
For example, in the above description, an example in which the present invention is applied to the case where two charge pump capacitors are provided (that is, boosting of about three times is performed) has been described. The present invention can be suitably applied to the case described above.

  Further, the present invention can be suitably applied to VFDs other than the CIG-VFD.

  1, 1A, 1B, 1C Fluorescent display tube, An anode, Fi filament, Gr grid, 2, 2A, integrated circuit device, 2a, 2aA controller, 3 display unit, 20 booster unit, 25 anode driver unit, 25a logic circuit, 25b level shift circuit 25b, 25c output buffer, 26 grid driver section, 27 anode terminal section, 28 grid terminal section, 29, 29A power supply control section, 30 detection section, Q1-Q4, Q5, Q6 switching element, VDD logic voltage, Vo output voltage, Ma1-Man lighting control value, Tm drive timing signal, Sa1-San signal line, Si power notification signal, Sp power control signal, 100, 100A, 100B, 100C display unit, 101 microcomputer, 102, 102A power circuit , Ti power supply Knowledge terminal, Tp power control terminal

Claims (7)

A filament that emits electrons, an anode in which a phosphor is formed on an anode electrode that controls the movement of the electrons, a grid that is an electrode disposed between the anode and the filament, the anode and the grid An integrated circuit device that performs drive control of the integrated circuit device in a fluorescent display tube comprising:
An anode driving unit that operates with a first voltage and applies a second voltage higher than the first voltage to the anode as a driving voltage;
A grid driving unit that applies the second voltage to the grid as a driving voltage,
For the stop control of the voltage generation operation of the first voltage and the second voltage, when the stop control is performed in the order of the second voltage and the first voltage, the driving of the grid by the grid driving unit is A control unit that continues after the stop control of the second voltage until before the stop control of the first voltage is performed. The control unit includes:
The integrated circuit device according to claim 1, wherein the drive of the anode by the anode drive unit is stopped in response to determining that the stop control of the second voltage is performed . The control unit includes:
The integrated circuit device according to claim 1, wherein the driving of the grid is stopped after a lapse of a predetermined time from the stop control of the second voltage. The control unit includes:
The integrated circuit device according to claim 1, wherein the drive stop timing of the grid is controlled based on a detected value of the second voltage. A filament for emitting electrons,
An anode in which a phosphor is formed on an anode electrode for controlling the movement of the electrons,
A grid that is an electrode disposed between the anode and the filament;
An anode driving unit that operates with a first voltage and applies a second voltage higher than the first voltage to the anode as a driving voltage;
A grid driving unit that applies the second voltage to the grid as a driving voltage,
For the stop control of the voltage generation operation of the first voltage and the second voltage, when the stop control is performed in the order of the second voltage and the first voltage, the driving of the grid by the grid driving unit is A control unit configured to continue after the stop control of the second voltage and before the stop control of the first voltage is performed. A fluorescent display having at least a filament that emits electrons, an anode in which a phosphor is formed on an anode electrode that controls the movement of the electrons, and a grid that is an electrode disposed between the anode and the filament. Tubes and
An anode driving unit that operates with a first voltage and applies a second voltage higher than the first voltage to the anode as a driving voltage;
A grid driving unit that applies the second voltage to the grid as a driving voltage,
Regarding the stop control of the voltage generation operation of the first voltage and the second voltage, the stop control is performed in the order of the second voltage and the first voltage, and the driving of the grid by the grid driving unit is the second control. A control unit configured to continue after the stop control of the voltage and before the stop control of the first voltage is performed. A fluorescent display tube having at least a filament that emits electrons, an anode in which a phosphor is formed on an anode electrode that controls the movement of the electrons, and a grid that is an electrode disposed between the anode and the filament An anode driving unit that operates with a first voltage and applies a second voltage higher than the first voltage to the anode as a driving voltage, and a grid that applies the second voltage as a driving voltage to the grid A power supply in a display device, comprising: a driving unit; and a control unit that performs the stop control in the order of the second voltage and the first voltage with respect to stop control of the voltage generation operation of the first voltage and the second voltage. A stop control method,
A power stop control method in which the control unit continues driving the grid by the grid drive unit after the stop control of the second voltage until before the stop control of the first voltage is performed.

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