Method for driving a fluorescent display tube and design method for driving a fluorescent display tube

Abstract

In a fluorescent display tube module equipped with a driver converter and a filament converter, the peak value of the inrush current can be reduced, and a method for driving the fluorescent display tube that does not affect the customer's inrush current is provided. [Solution] The driving method is for a fluorescent display tube module comprising a fluorescent display tube having a filament and an anode on which a phosphor is formed, and a driving circuit attached to the fluorescent display tube, wherein the fluorescent display tube is driven by the driving circuit, and the driving circuit is provided with a driver converter that generates a driver voltage from an input voltage and a filament converter that generates a filament voltage from an input voltage, and these are electrically connected in parallel to a pair of input terminals to which an input voltage is applied, and when the fluorescent display tube module is started up, the driving method starts up the driver converter and then starts up the filament converter after a predetermined time delay.

Description

Technical Field

[0001] The present invention relates to a method for driving a fluorescent display tube, and more particularly to a method for driving a fluorescent display tube that reduces the inrush current when the power supply of a fluorescent display tube module is started. The present invention also relates to a design method for designing such a driving method.

Background Art

[0002] As a display device, a vacuum fluorescent display (VFD) is widely known. In a vacuum fluorescent display tube, a filament (cathode) that emits electrons and an anode on which a phosphor is formed on an anode electrode that controls the movement of electrons are arranged inside a vacuum envelope. In a vacuum fluorescent display tube, thermoelectrons are emitted by applying a voltage to the filament and heating it, and the anode is lit by colliding the thermoelectrons with the phosphor on the anode. The anodes are arranged in a predetermined pattern, and by applying a driver voltage to a target anode, only the phosphor of that anode can be made to emit light, and a desired pattern can be displayed.

[0003] As a vacuum fluorescent display tube, a three - electrode structure vacuum fluorescent display tube having a grid electrode for controlling the action of electrons between the filament and the anode is common.

[0004] In addition, a vacuum fluorescent display tube is distributed as a modularized vacuum fluorescent display tube module including an attached drive circuit. The vacuum fluorescent display tube module is mounted on a device that mounts the vacuum fluorescent display tube as a display device, and the input terminal of the drive circuit of the vacuum fluorescent display tube module is electrically connected to the power supply of the device. Then, by receiving the input voltage from the power supply and supplying power to the drive circuit of the vacuum fluorescent display tube module, the display function is exhibited.

[0005] In fluorescent display tube modules, it has been pointed out that an inrush current flows when the power supply is started. An inrush current is a phenomenon in which a current larger than the steady-state current flows temporarily when the power supply is started. In the drive circuit, an excessive load is placed on each circuit component when an inrush current flows, so various proposals to reduce the inrush current have been considered (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2000-172230 [Overview of the project] [Problems that the invention aims to solve]

[0007] Incidentally, among the various circuit configurations known for the drive circuits of fluorescent display tubes, there are cases where the drive circuit is equipped with a driver converter that generates a driver voltage (including at least the anode voltage) from the input voltage, and a filament converter that generates the filament voltage. In such a fluorescent display tube module, when the power supply of the module is started up, the driver converter and the filament converter start up simultaneously, and there is a concern that the inrush currents of each converter will be superimposed, causing a large inrush current to flow through the drive circuit.

[0008] Furthermore, there are occasions when the fluorescent display tube module is replaced at the customer's site (such as the manufacturer of the equipment that incorporates the fluorescent display tube module as a display device). In such cases, the fluorescent display tube module supplied to the customer may have circuit components changed due to discontinuation or other reasons, which may result in a larger inrush current compared to the fluorescent display tube module before replacement. Fluorescent display tubes are display devices that are incorporated into customers' equipment, and the power supply to the equipment at the customer's site is determined by the customer's circumstances. Therefore, if the inrush current is larger than that of the conventional fluorescent display tube when it is replaced, the customer's existing power supply may not have enough current, and the equipment incorporating the fluorescent display tube may not be able to start up. One possible solution is for the customer to install a new power supply to accommodate the issue, but this would impose a burden on the customer and is therefore difficult to implement. Another possibility is to reduce the inrush current by adopting new mechanisms or circuit configurations in the fluorescent display tube module, but this could lead to increased costs. Under these limited conditions, the development and manufacturing of fluorescent display tube modules is required to suppress the inrush current.

[0009] This invention has been made in view of these circumstances, and aims to provide a method for driving a fluorescent display tube that can reduce the peak value of inrush current in a fluorescent display tube module equipped with a driver converter and a filament converter, and that does not affect the customer with inrush current, for example. Furthermore, it aims to provide a design method that is convenient for designers in designing such a driving method. [Means for solving the problem]

[0010] The present invention relates to a method for driving a fluorescent display tube, comprising a fluorescent display tube module having a filament and an anode on which a phosphor is formed, and a drive circuit attached to the fluorescent display tube, wherein the fluorescent display tube is driven by the drive circuit, and the drive circuit is provided with a driver converter that generates a driver voltage from an input voltage and a filament converter that generates a filament voltage from an input voltage, and these are electrically connected in parallel to a pair of input terminals to which an input voltage is applied, and the driving method is characterized in that, when starting the fluorescent display tube module, the driver converter is started first, and then the filament converter is started after a predetermined time delay.

[0011] The above-mentioned fluorescent display tube module includes a control unit that transmits a start signal to the driver converter and the filament converter, respectively, and is characterized in that, after the start signal is transmitted to the driver converter by the control unit, a start signal is transmitted to the filament converter after a predetermined time delay.

[0012] The above-mentioned predetermined time is characterized by being 5 msec or more and 30 msec or less.

[0013] The predetermined time is characterized by being set to a time range in which the sum of the current value of the current flowing based on the driver voltage of the driver converter and the current value of the current flowing based on the filament voltage of the filament converter is less than or equal to a predetermined current limit value.

[0014] The present invention relates to a method for designing a drive system for a fluorescent display tube, and is characterized by using means to restrict the startup order so that the filament converter is started after the driver converter is started, and by setting a delay time to design the startup timing of the filament converter relative to the startup timing of the driver converter. [Effects of the Invention]

[0015] In the drive circuit of a fluorescent display tube module to which the drive method of the present invention is applied, a driver converter that generates a driver voltage from the input voltage and a filament converter that generates a filament voltage from the input voltage are electrically connected in parallel to a pair of input terminals to which the input voltage is applied. When the fluorescent display tube module is started up, the inrush currents of each converter may be superimposed. Looking at the characteristics of the inrush currents of each converter, the inrush current of the driver converter tends to subside in a very short time after startup (for example, within 10 msec), while the filament converter tends to have a longer period of inrush current compared to the driver converter.

[0016] In view of this, the driving method of the present invention, when starting up a fluorescent display tube module, starts up the driver converter and then starts up the filament converter after a predetermined time delay, thereby distributing the inrush current of each converter and reducing the peak value of the inrush current of the entire module. This prevents malfunctions that may occur, for example, when replacing a fluorescent display tube module at a customer's site, even if the inrush current of each converter increases due to a change in circuit components. It should be noted that the converter targeted for control in the above-mentioned Patent Document 1 is the driver converter, and fluorescent display tube modules having a filament converter along with the driver converter have not been considered.

[0017] The above-mentioned fluorescent display tube module includes a control unit that transmits a start signal to a driver converter and a filament converter. After the control unit transmits a start signal to the driver converter, it transmits a start signal to the filament converter at a predetermined timing. Therefore, the above-mentioned driving method can be easily implemented by configuring the control unit.

[0018] If the filament converter's startup timing is delayed, the fluorescent display tube's illumination will also be delayed after the fluorescent display tube module is powered on, which may cause operators to perceive a malfunction or feel uneasy. In this regard, if the predetermined time is between 5 msec and 30 msec, it is possible to effectively stagger the startup timing while eliminating such uneasiness. Furthermore, by setting the predetermined time to a range where the sum of the current value flowing based on the driver voltage of the driver converter and the current value flowing based on the filament voltage of the filament converter is less than or equal to a predetermined current limit, the delay time can be minimized as much as possible.

[0019] The design method of the driving method for the fluorescent display tube of the present invention is a method using means for restricting the startup sequence so that the converter for the filament is started after the converter for the driver is started. By setting the delay time, the startup timing of the converter for the filament with respect to the startup timing of the converter for the driver is designed. Therefore, even if the designer is, for example, a beginner or a person with low proficiency, the startup sequence of each converter can be set correctly without mistakes, and the startup timing of the converter for the filament can be easily designed. As a result, it becomes a highly convenient design method for the designer in designing a drive circuit in which the peak value of the inrush current is reduced.

Brief Description of the Drawings

[0020] [Figure 1] It is a schematic cross-sectional view of an example of a fluorescent display tube to which the driving method of the present invention is applied. [Figure 2] It is a circuit block diagram of an example of a drive circuit in a fluorescent display tube module. [Figure 3] It is an image diagram showing the behavior of the inrush current when the converter for the driver and the converter for the filament are started simultaneously. [Figure 4] It is an image diagram showing the behavior of the inrush current according to the driving method of the present invention. [Figure 5] It is a flowchart showing the procedure of one form of the driving method of the present invention.

Embodiments of the Invention

[0021] An example of a fluorescent display tube to which the fluorescent display tube driving method of the present invention applies will be described with reference to Figure 1. Figure 1 shows a schematic cross-sectional view of a fluorescent display tube. As shown in Figure 1, the fluorescent display tube 1 is formed by sealing and joining a front plate 3 and a substrate 2 at a sealing portion (not shown) via a spacer member 4 to form a vacuum container. The front plate 3 is made of a translucent cover glass plate or the like, the substrate 2 is made of an insulating material such as glass or ceramics, and the spacer member 4 is made of a frame-shaped glass material or the like. The front plate 3 and the substrate 2 are glass-sealed to each other at the sealing portion via the spacer member 4, thereby forming an airtight, elongated flat box-shaped vacuum container, and a vacuum space surrounded by these components is formed inside it.

[0022] The fluorescent display tube 1 has an anode 5 on which phosphor 5b is formed on the surface of a plurality of anode electrodes 5a provided on a substrate 2 inside the vacuum container, and a filament 6 suspended above the phosphor 5b. The fluorescent display tube 1 is a three-electrode fluorescent display tube and further includes a grid electrode 7 having a mesh structure disposed between the phosphor 5b and the filament 6. In Figure 1, 8 is wiring formed on the substrate 2, and 9 is an insulating layer.

[0023] In the fluorescent display tube 1, multiple filaments 6 (four in Figure 1) are provided, each parallel to the others (for example, along the longitudinal direction of the substrate 2) and positioned at a predetermined height above the grid electrode 7 and separated from the display surface of the substrate 2. Specifically, the filaments 6 are attached with a predetermined tension between a filament support (fixed end) and a filament anchor (movable end).

[0024] The filament 6 is, for example, a tungsten core wire with a diameter of several μm to about 30 μm, on which oxide films of barium, strontium, and calcium are formed. The filament 6 is electrically connected to filament terminals at both ends, and the filament terminals are electrically connected to a filament converter 14 (see Figure 2). By applying a predetermined filament voltage to the filament terminals at both ends, the cathode temperature becomes about 600°C to 650°C, and thermionic electrons are emitted.

[0025] The anode 5 is formed by depositing a phosphor 5b onto an anode electrode 5a that controls electrons emitted from the filament 6. The anode 5 is formed on the substrate 2, for example by pattern printing, and arranged in a desired pattern to be displayed. For example, a display area (display block) of a predetermined unit, corresponding to a single digit or a single character, is formed by multiple segments of anode 5. For example, multiple such display blocks are arranged on the substrate 2.

[0026] The grid electrode 7 is a mesh-like electrode formed from a thin sheet of stainless steel or similar material using photoetching or other methods. For example, by applying a positive voltage to the grid electrode 7, it accelerates and diffuses electrons emitted from the filament 6 towards the anode 5, or by applying a negative voltage to the grid electrode 7, it blocks (cuts off) the electrons heading towards the anode 5, thereby erasing the display.

[0027] Figure 2 shows a circuit block diagram of an example of a drive circuit for a fluorescent display tube module 11. As shown in Figure 2, the fluorescent display tube module 11 comprises a fluorescent display tube 1 and a drive circuit attached to the fluorescent display tube 1. The drive circuit has a pair of input terminals P to which an external power supply 21 is applied. in It is equipped with a circuit in which each part is electrically connected via connecting wires.

[0028] The external power supply 21 is a power supply provided in a device that incorporates the fluorescent display tube 1 as a display device, and for example, a DC power supply of approximately 5V or approximately 12V is used. The drive circuit is provided with a control unit 12, a driver converter 13, and a filament converter 14. For example, the control unit 12, the driver converter 13, and the filament converter 14 are connected to a pair of input terminals P in It is electrically connected in parallel to it.

[0029] The control unit 12 is mainly composed of a microcomputer consisting of a well-known CPU, ROM, RAM, etc. The control unit 12 uses the input voltage Vi as its operating power supply, transmits and receives various signals, and controls the display operation of the fluorescent display tube 1.

[0030] The driver converter 13 is a converter that drives the anode and grid electrodes. Typically, the same voltage is used for the grid and anode, and below, the grid voltage and anode voltage together will be referred to as the "driver voltage". Specifically, the driver converter 13 generates a driver voltage Vd from the input voltage Vi and drives the anode and grid electrodes with this driver voltage Vd. For example, the luminescence brightness of the anode can be adjusted by changing the ON duty cycle of the drive signal to the anode.

[0031] In the case where the fluorescent display tube 1 does not have a grid electrode, the anode voltage is used as the driver voltage.

[0032] The driver converter 13 is, for example, a DC / DC (direct current / direct current) converter, which converts the DC input voltage Vi from the external power supply 21 to a predetermined DC driver voltage Vd (for example, about 50V). The circuit configuration of the driver converter 13 can be a well-known circuit configuration. For example, a step-up circuit or a charge pump circuit can be used as the boost circuit.

[0033] The step-up circuit includes an inductor, a switch, a diode, and a capacitor, and is configured as a chopper-type boost switching regulator. As the switch, n-channel or p-channel MOSFETs, bipolar transistors, etc., can be used. The charge pump circuit also includes a capacitor and a diode. The number of charge pump stages is not particularly limited; for example, a multi-stage configuration of two or three stages is possible.

[0034] The driver converter 13 includes, for example, a driver IC (not shown). The driver IC receives a startup signal transmitted from the control unit 12 and generates a driver voltage Vd. Preferably, the driver converter 13 also has a feedback function to ensure that the output voltage becomes a predetermined voltage. In this case, the detected value of the output voltage is input to the driver IC.

[0035] The connection configuration between the driver converter 13 and the fluorescent display tube 1 is not particularly limited and varies depending on the driving method of the fluorescent display tube 1, for example. Driving methods for the fluorescent display tube 1 include dynamic driving (multiplex driving) and static driving.

[0036] In dynamic driving, grid electrodes are drawn separately for each display block, while anodes are drawn by connecting the corresponding segments of each display block in common. In this case, time-division display is achieved by applying a display block selection pulse to the grid electrodes, which are independently divided for each display block. In static driving, grid electrodes are drawn electrically as a single unit, while anodes are drawn individually for each segment. In this case, a positive voltage is always applied to the grid electrodes, and any display is achieved by selecting and turning the anodes ON / OFF. For example, in static driving, since the anode's light emission duty cycle is 100%, it can be driven at a relatively low voltage (12-15V).

[0037] The filament converter 14 is a converter that drives the filament. Specifically, the filament converter 14 generates a filament voltage Vf from the input voltage Vi and applies the filament voltage Vf to the filament.

[0038] The filament converter 14 is, for example, a DC / DC (direct current / direct current) converter, which converts the DC input voltage Vi from the external power supply 21 to a predetermined DC filament voltage Vf (for example, about 5V). The circuit configuration of the filament converter 14 (for example, a boost circuit) can be a well-known circuit configuration. In addition, for the sake of module simplification, it is preferable that the filament converter 14 does not have a filament IC. The filament converter 14 may also be a DC / AC (direct current / alternating current) converter that converts the DC input voltage Vi from the external power supply 21 to an AC filament voltage Vf.

[0039] The connection configuration between the filament converter 14 and the fluorescent display tube 1 is not particularly limited. For example, they may be connected to apply voltage to all filaments simultaneously, or they may be connected to apply voltage to individual filaments. In the former connection configuration, multiple filament terminals at the end are connected in series. In the latter connection configuration, each of the multiple filaments is connected to apply a pulsed (square wave) filament voltage Vf at different timings.

[0040] Here, the fluorescent display tube module 11 is generally used by being incorporated into a device that uses the fluorescent display tube module as a display device. When malfunctions occur due to long-term use, it is replaced with a new fluorescent display tube module. In such cases, the specifications of the device and the voltage of the external power supply 21 are not changed, and only the fluorescent display tube module is replaced. Therefore, a high degree of compatibility is required for the fluorescent display tube module 11. On the other hand, it is not easy to obtain the same parts permanently for each circuit component that makes up the fluorescent display tube module 11, and there may be cases where the same parts cannot be obtained due to discontinuation or other reasons. In such cases, it will be replaced with a different part that has equivalent performance, but depending on the replaced part, the electrical characteristics may change, and there may be concerns about inrush current.

[0041] Immediately after powering on electrical equipment, an inrush current exceeding the steady-state current value may flow. For example, when a fluorescent display tube module with the configuration shown in Figure 2 is connected to an external power supply, the inrush currents generated in the driver converter 13 and the filament converter 14 (Figures 3(a) and (b)) are superimposed, resulting in an excessive inrush current for the entire drive circuit. In Figure 3(c), the total current of each converter is shown by a solid line. For example, even if there was no problem with inrush current with the fluorescent display tube module before replacement (previous product), replacing it with a new fluorescent display tube module with replaced circuit components can increase the inrush current of each component, potentially exceeding the current limit of the external power supply. Exceeding the current limit can cause malfunctions such as the fluorescent display tube 1 failing to start.

[0042] Therefore, in this invention, when starting up the fluorescent display tube module, the timing of starting up the driver converter and the timing of starting up the filament converter are staggered to distribute the timing of the inrush current generation of each converter. Furthermore, the order in which each converter is started is also specified, taking into account the characteristics of the inrush current of each converter.

[0043] As shown in Figure 3(a), the inrush current of the driver converter subsides within a very short time during startup (e.g., within 10 msec). The peak of this inrush current is sharp, and after rising, it quickly returns to the steady-state current value. The inrush current subsides once the charging of the capacitor connected to the driver converter is complete, and this process is completed in a short time. Therefore, it is easy to distinguish the boundary between the inrush current and the steady state.

[0044] On the other hand, in a filament converter, the inrush current flows for a relatively long period, and after rising, it gradually decreases and returns to a steady-state current value. The filament is a resistor, and its resistance changes with temperature. In other words, immediately after voltage is applied, the temperature is low and the resistance is small, so an inrush current flows, and as the temperature rises and the resistance stabilizes, the current also stabilizes, but the time it takes to stabilize is longer than the time it takes to charge the capacitor in a driver converter. Thus, because the filament temperature gradually rises and then stabilizes, the inrush current gradually decreases after rising and returns to a steady-state current value, and as a result, it is difficult to distinguish the boundary between the inrush current and the steady state.

[0045] In the driving method of the present invention, taking into account the difference in inrush current in each converter, the driver converter is started first, and then the filament converter is started after a predetermined time delay. Specifically, as shown in Figure 4(a), the timing Tf for starting the filament converter (approximately the same as the timing for receiving the start signal) is set after the timing Td for starting the driver converter (approximately the same as the timing for receiving the start signal). In the example in Figure 4(a), the inrush current of the filament converter is set to occur after the inrush current of the driver converter has disappeared, and by eliminating the superposition of the respective inrush currents, the peak value of the inrush current in the entire driving circuit is suppressed. As a result, the peak value of the inrush current is kept below the current limit value.

[0046] On the other hand, one way to stagger the startup timing of each converter is to do so in the reverse order of Figure 4(a). However, as shown in Figure 4(b), if the startup timing is reversed (by placing Td after Tf), the inrush current of the filament converter will last for a relatively long time, making it difficult to set the startup timing of the driver converter. In this case, it is also difficult to distinguish the boundary between the inrush current and the steady state for the filament converter, which starts up first. For example, if the person setting the startup timing is inexperienced, they may mistakenly think that the end point of the inrush current of the filament converter has occurred and set the startup timing of the driver converter to an earlier timing. In that case, even if the startup timing of each converter is staggered, it is conceivable that the peak value of the inrush current cannot be suppressed.

[0047] Therefore, in the above driving method, the driver converter's startup timing is set to start first, as the inrush current flows for a very short time and it is easy to distinguish from the steady state, while the filament converter's startup timing is intentionally delayed. Furthermore, the design method for the driving system described later allows even inexperienced individuals to easily design the startup timing of each converter without making mistakes.

[0048] In the configuration shown in Figure 2, the drive method of the present invention is realized by the control of the start signal by the control unit 12. Specifically, the transmission timing of the start signal 2 for the filament converter 14, transmitted from the control unit 12, is delayed by a predetermined time from the transmission timing of the start signal 1 for the driver converter 13. As a result, after the inrush current based on the driver voltage Vd at the start of the driver converter 13 occurs, the inrush current based on the filament voltage Vf at the start of the filament converter 14 occurs after a predetermined time delay, thereby reducing or avoiding the superposition of inrush currents.

[0049] The procedure for controlling the startup of each converter by the control unit 12 is shown in the flowchart of Figure 5. The process from start to finish in Figure 5 is repeatedly executed at predetermined time intervals (for example, every 1 msec) after the control unit starts operating based on the input voltage.

[0050] First, in step S11, it is determined whether the start signal 1 for activating the driver converter is "OFF". If the start signal 1 is "OFF" (step S11: Yes), the start signal 1 is turned "ON" (step S12). In other words, the start signal 1 is sent to the driver converter, and the driver converter is activated. An inrush current is generated in the driver converter as a result of this activation.

[0051] After turning on the start signal 1, the count start trigger is turned on to set the count to 0 (steps S13-S14). Then, it is determined whether the count start trigger is "ON" and if it is (step S15: Yes), the count is advanced. In this step S16, the count is increased by 1.

[0052] Then, if the activation signal 1 is "ON" (step S17: Yes) and the count start trigger is "ON" (step S18: Yes), step S19 determines whether the count has reached a predetermined count. This predetermined count corresponds to the signal delay time (delay time), and in step S19 it is set to the threshold m.

[0053] The threshold value m is a value that is set in advance, taking into consideration the characteristics of the inrush current of the driver converter, the characteristics of the inrush current of the filament converter, and the power limit value of the external power supply. The threshold value m is set in the range of 5 msec to 30 msec, for example, and more specifically, it is set to about 10 msec. The threshold value m may be set to ensure sufficient time for the inrush current of the driver converter to dissipate, as shown in Figure 4(a). Alternatively, even if the inrush current of the driver converter has not dissipated, if the current remains within the current limit value even when the inrush current of the filament converter is added in such a state, the threshold value m may be set to a time when the inrush currents of the driver converter and the filament converter partially overlap.

[0054] If the count in step S19 has not reached a predetermined count (threshold m), the process terminates. The count continues to advance until the count determination in step S19 becomes Yes. In other words, the process of step S11 being No, step S15 being Yes, step S16 (count up), step S17 being Yes, step S18 being Yes, and step S19 being No is repeated.

[0055] When the count exceeds the threshold m (step S19: Yes), the start signal 2, which activates the filament converter, is turned "ON". In other words, the start signal 2 is turned "ON" only when the condition count ≥ m is met from the starting timing of the start signal 1. This sends the start signal 2 to the filament converter and activates it. Since an inrush current is generated in the filament converter when it is activated, the timing of the generation of the inrush current can be shifted by the threshold m.

[0056] Then, the count start trigger is turned "OFF," ending the series of startup processes performed by the control unit.

[0057] As shown in Figure 5, the startup process starts with the timing when startup signal 1 changes from "OFF" to "ON," and after a delay (time elapsed) of threshold m, startup signal 2 turns "ON." The person setting the startup timing only needs to specify the delay time defined by threshold m (for example, timer operation time × m), and will be able to control the generation of the driver voltage and filament voltage in the order of startup signal 1 and startup signal 2.

[0058] In the above-described drive method, controlling the startup timing of each converter with the program of the control unit 12 (microcontroller) offers several advantages, such as eliminating the need for additional costs, allowing for flexible setting of the startup timing, and ensuring reliable avoidance of inrush current superposition due to less variation in timing. Note that delaying the startup timing of the filament converter is not limited to a software configuration; it can also be implemented through a hardware configuration. For example, a configuration that delays the startup signal 2 by combining logic circuits is possible, or a configuration that shifts the operation timing of the converter by slowing down the rise time (slew rate) of the startup signal 2 can be employed.

[0059] Furthermore, the design method for the fluorescent display tube drive system of the present invention is a method for designing a drive system using the drive system of the present invention. Specifically, it is a method of designing by programming the operation of the control unit, and a program input device is used in this method. In this design method, it is preferable to use means that restrict the startup order so that the filament converter starts up after the driver converter starts up. Such means include, for example, means that display an error if the startup order is incorrect, or means that have a function in which the startup order is predetermined. By using such means, even a person with little experience can design without making a mistake in the startup order.

[0060] Furthermore, in the above design method, it is preferable to design the start timing of the filament converter in relation to the start timing of the driver converter by setting a delay time. For example, it is preferable that the delay time is set along with the start sequence simply by inputting the delay time using an input device or the like.

[0061] Alternatively, methods may be used to calculate the optimal delay time by inputting the current limit value of the external power supply and the characteristics of the inrush current of each converter (such as the occurrence time and current value).

[0062] The embodiments of the fluorescent display tube driving method of the present invention are not limited to those described in the figures. Furthermore, the configurations of the target fluorescent display tube and driving circuit are not limited to those described in the figures.

[0063] For example, in the above example, the driver voltage and filament voltage of the fluorescent display tube are supplied by a single power supply system (external power supply) in the drive circuit of the fluorescent display tube, but it is also possible to configure separate power supply systems (e.g., AC power supply) for generating the driver voltage and the filament voltage.

[0064] Furthermore, although the driving method of the present invention was applied to a fluorescent display tube with a triode structure having a grid electrode as described above, it can also be applied to a fluorescent display tube with a diode structure in which the grid electrode is omitted. [Industrial applicability]

[0065] The fluorescent display tube driving method of the present invention, in a configuration comprising a driver converter and a filament converter, can reduce the peak value of the inrush current. For example, when incorporating a fluorescent display tube module into a device in which circuit components have been replaced from previous components, even in situations where the inrush current increases due to the change in circuit components, the peak value of the inrush current can be suppressed, making it suitable for situations such as replacing the fluorescent display tube module. Furthermore, the design method of the present invention is a convenient method for designers in designing the above-mentioned driving system, and can be used regardless of the designer's skill level, making it widely applicable. [Explanation of symbols]

[0066] 1. Fluorescent display tube (VFD) 2 circuit boards 3 Front plate 4 Spacer members 5 Anodes 5a Anode electrode 5b Phosphor 6 filaments 7 Grid electrodes 8 Wiring 9. Insulating layer 11. Fluorescent Display Tube (VFD) Module 12 Control Unit 13 Driver Converters 14 Filament Converter P in Input terminals

Claims

1. A fluorescent display tube module comprising a fluorescent display tube having a filament and an anode on which a phosphor is formed, and a drive circuit attached to the fluorescent display tube, wherein the fluorescent display tube is driven by the drive circuit, The drive circuit includes a driver converter that generates a driver voltage from the input voltage and a filament converter that generates a filament voltage from the input voltage, and these are electrically connected in parallel to a pair of input terminals to which the input voltage is applied. The above-mentioned driving method is characterized in that, when starting the fluorescent display tube module, the driver converter is started, and then the filament converter is started after a predetermined time delay.

2. The fluorescent display tube module includes a control unit that transmits a start signal to the driver converter and the filament converter, respectively, and the control unit transmits a start signal to the driver converter, followed by a predetermined delay in transmitting a start signal to the filament converter, characterized in that the fluorescent display tube driving method according to claim 1.

3. The method for driving a fluorescent display tube according to claim 1 or 2, characterized in that the predetermined time is 5 msec or more and 30 msec or less.

4. The method for driving a fluorescent display tube according to claim 1 or 2, characterized in that the predetermined time is set to a time range in which the sum of the current value of the current flowing based on the driver voltage of the driver converter and the current value of the current flowing based on the filament voltage of the filament converter is less than or equal to a predetermined current limit value.

5. A method for designing a driving system for a fluorescent display tube according to the driving method of claim 1 or claim 2, A method for designing a drive system for a fluorescent display tube, characterized by using means to restrict the startup order so that the filament converter is started after the driver converter is started, and designing the startup timing of the filament converter in relation to the startup timing of the driver converter by setting a delay time.

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