JPH0650030Y2 - Display tube Display type electronic device - Google Patents

Description

[Detailed Description of the Invention] <Industrial field of application> The present invention is a display tube for an electronic desk calculator or the like, which displays data by key input etc. on a fluorescent display tube and holds the memory in the off mode. The present invention relates to a display-type electronic device.

<Prior Art> Most of the electronic desk calculators on the market in recent years use a liquid crystal display element because of low power consumption as a display unit, but this liquid crystal display element has a drawback that it is very difficult to see. The fluorescent display tube is still used in the electronic desk calculator for business use, which is focused on the visibility of the display rather than the low power consumption. By the way, since this fluorescent display tube is for dynamically driving by emitting a desired digit or the like in a time division manner, the display drive circuit converts a DC input voltage into a rectangular wave pulse by a DC-DC converter. It is designed to be converted. Therefore, many circuit parts are required to have the same auto power-off function and memory holding function as those of the liquid crystal display device, and thus these functions are not provided.

For this reason, for example, a tax calculator task generally called TAX has been hindering the task of frequently interrupting the key input operation for a relatively long time. Computers with a memory function are beginning to appear in electronic desk calculators.

Such a conventional display tube display type electronic desk calculator with a memory function has a configuration as shown in FIG. That is, this electronic desk calculator operates by the DC power source which is alternatively input from the adapter A or the battery B of the electronic device, and the ON mode and the ON mode set by the ON key 2 and the OFF key 5, respectively. The predetermined operation is performed in the off mode. In off mode,
The potential V _DD (+ 5V) and V _CC appearing across the Zener diode Z1 via the noise eliminating capacitor C1 and the resistor R1 in the memory holding circuit 3 by the input DC voltage, respectively.
(0V) goes through diode D1 and capacitor C2 to LS
It is supplied to the central processing unit 1 made of I as a warm-up driving power source for the central processing unit 1, and the central processing unit 1 enters a standby state and holds the input contents up to that point.

Here, when the central processing unit 1 reads in the key input by operating the ON key 2, the mode switching signal of the mode control terminal M of the central processing unit 1 becomes high level (V _DD
This high level signal is applied to the base through the capacitor C3 and the resistors R2 and R3 in the mode switching circuit 4, and the transistor Q1 is turned on. The switching transistor Q2, which has been in the OFF state when the divided voltage of the DC input voltage is applied to the base by the resistors R4 and R5, is also turned on, and the DC-DC converter that is supplied with power through the transistor Q2 is driven. This converter 6 includes a switching transistor Q3, a converter transformer T, rectifying diodes D2 and D3, zener diodes Z2 and Z3, resistors R6 to R8, a DC cut capacitor C4 and an electrolytic capacitor C5, which is a well-known self-excited low voltage control. The circuit configuration is based on the system, and the display voltage V _NG (−2
5 V) and a drive voltage V _DD (+5 V) for the central processing unit are supplied to the fluorescent display tube 7 and the central processing unit 1, respectively. Therefore, the fluorescent display tube 7 is turned on, displays "0.", and is in the on mode.

Here, when the central processing unit 1 reads in the key input by operating the off key 5, the mode switching signal of the mode control terminal M of the central processing unit 1 becomes low level (V _CC
OV), the transistors Q1 and Q2 are both turned off, the operation of the converter 6 is stopped, and the off mode is set. At this time, the central processing unit 1 is supplied with power from the memory holding circuit 3 and enters the standby state similar to the above, and holds the input contents up to that point.

<Problems to be solved by the invention> By the way, in this kind of electronic desktop computer, it takes time to read the key input by the ON key 2 in comparison with data input keys such as ten keys and various function keys. Therefore, the mode switching signal of the central processing unit 1 is switched from the low level to the high level after t seconds have elapsed since the key was pressed by operating the ON key 2. Therefore, the DC-DC converter 6 is not driven until t seconds have elapsed since the ON key 2 was operated or the power was turned on, so that the central processing unit 1 is supplied with power through the memory holding circuit 3. Here, from the moment the ON key 2 is operated or the power is turned on, several mA is applied to the central processing unit 1 through the resistor R1, the diode D1 and the capacitor C2 of the memory holding circuit 3.
Current flows through the Zener diode Z1, and the current at the point E in FIG. Therefore, as shown in FIG.
The rising voltage value V ₀ of the _DD voltage does not become so high, and this voltage decreases as shown in the figure with the subsequent discharge of the capacitor C2, becomes V _t when t seconds have elapsed, and switches to a high level at that time. a substantially lower potential than the required 5V even mode switching signal voltage that is almost V _t.

By the way, between the base of the transistor Q1 and the mode control terminal M in the mode switching circuit 4, for the purpose of surely turning off the transistor Q1 regardless of leakage of the printed wiring board when the mode switching signal becomes low level. Since the resistor R2 is inserted and connected, the transistor Q1 cannot be turned on unless a base bias voltage higher by that amount is applied. However, this transistor
The mode switching signal for base-biasing Q1 is lowered as described above, and therefore the level required to turn on the transistor Q1 cannot always be held. Therefore, the mode switching circuit 4 is not switched to the ON mode, so that the DC-DC converter 6 cannot be driven, and as a result, the fluorescent display tube 7 is not driven, which causes an inconvenience of no display.

The present invention has been made in view of such conventional problems, and it is a technical problem to provide a display tube display type electronic device capable of reliably driving a DC-DC converter by a mode switching circuit. It is what

<Means for Solving the Problems> According to the present invention, as a technical means for achieving the above-mentioned objects, a display tube display type electronic device is configured as follows.
That is, a central processing unit that outputs a mode switching signal that switches the operating state of the fluorescent display tube that constitutes the display unit between an on mode and an off mode by a mode setting key, and a direct current input voltage is converted to a constant voltage for the fluorescent display tube. A DC-DC converter that supplies a display power source and a driving power source to the central processing unit, and is connected to an input stage of the DC-DC converter, and the DC-DC is operated by a mode switching signal of the central processing unit.
A mode switching circuit that disconnects and supplies the DC input voltage to the converter and an input stage of the mode switching circuit, and generates a drive voltage that puts the central processing unit in a standby state based on the DC input voltage in the off mode. And a memory holding circuit for supplying to the central processing unit, wherein the memory holding circuit serves as a constant voltage means when a switching operation from an off mode to an on mode is performed by the mode setting key or when the power is turned on. Regardless, a resistor for supplying a drive voltage to the central processing unit based on a DC input voltage and a bypass capacitor are connected to the constant voltage means.

<Operation> When the power is turned on or when the ON mode setting operation is performed with the mode setting key in the OFF mode,
The DC input voltage is supplied as a driving voltage to the central processing unit through the resistor and the bypass capacitor regardless of the presence of the constant voltage means such as the Zener diode of the memory holding circuit. Therefore, even if the rising of the driving voltage becomes significantly larger than that of the conventional device and then decreases with the discharge of the capacitor, etc., the voltage of the mode switching signal that becomes the high level for the ON mode setting after the predetermined time. Even if a resistor for surely turning off the switching transistor of the mode switching circuit is connected to the base of the switching transistor of the mode switching circuit, the value can be reliably maintained at the voltage level necessary for turning on the transistor.

When the off mode is set by the mode setting key, the mode switching circuit performs a switching operation so as to cut off the power supply to the DC-DC converter by the mode switching signal, and the middle processing unit has a fixed memory holding circuit. The power required for the standby operation is supplied through the voltage means and holds the input data by the key operation.

<Embodiment> Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an electric circuit of a display tube driving part which is a main part of one embodiment of the present invention. In FIG. 1, the same or equivalent parts as in FIG. To do.
The difference from FIG. 5 lies in that the memory holding circuit 8 is
It is only a configuration in which a resistor R9 and a bypass capacitor C6 are connected in series between the positive side DC input side and the cathode of the Zener diode Z1.

Therefore, when the power is turned on, or when the ON key 2 is operated in the OFF mode by the operation of the OFF key 5 or the later-described auto power off, the DC input voltage becomes
The voltage is supplied to the central processing unit 1 as a driving voltage through the resistor R9 and the bypass capacitor C6 regardless of the presence of the Zener diode Z1 of the memory holding circuit 8. Therefore, although the potential at the point E decreases, as shown in FIG. 4, the rising voltage value V ₀ of the driving voltage V _DD is significantly higher than that of the conventional device as is clear from the comparison with FIG. The voltage value V _T after the elapse of t seconds is required to turn on the switching transistor Q1 of the mode switching circuit 4 even if the voltage value V _T after the lapse of t seconds has become large and then decreases due to discharge of the capacitor C2 and the like. It can hold more than the level.

By connecting the bypass capacitor C6 to the memory holding circuit 8, the capacitors C2 and C6 at this moment are in an uncharged state at the moment when the adapter A or the battery B is connected and the power is turned on. An excessive current that exceeds the current capacity of D1 instantly tries to flow, but this is blocked by resistor R9 connected in series with bypass capacitor C6. Further, when the input commercial power supply to the adapter A fluctuates to about + 15%, the rising voltage value of the V _DD potential to the central processing unit 1 is increased by connecting the bypass capacitor C6. It tries to exceed the rated voltage range of, but this is also suppressed by the resistor R9.

Next, the software of the central processing unit 1 will be described based on the flowchart of FIG. First, the power is turned on and the operation is started by being automatically cleared (step S1), and the M register in which the memory contents are stored is cleared (step S2). Then, after the lapse of time t from the time when the power is turned on, the mode switching signal of the central processing unit 1 becomes high level (step S3), the converter 6 becomes in the operating state, and thereafter the on mode is set (step S4), and the calculation result The contents of the X register for storing and displaying are cleared (step S5). Further, the contents of the APO counter used as a timer for detecting the auto power off time are cleared (step S
6).

Then, the contents of the cleared X register, that is, "0."
Is displayed (step S7) while waiting for key input (step
Continue on S8). If there is no key input, the APO counter is incremented by "1" (step S11), then it is determined whether or not this APO counter is incremented (step S12), and steps are taken until the count is incremented. Cycle through the loop of S7, step S11, step S12,
The APO counter counts up by "1" every cycle of this display loop. Then, when the APO counter counts up and it is determined to be YES in step S12, the process proceeds to step 13 to perform the operation described later.

If a key signal is input before the APO counter counts up, it is determined whether or not it is the off key 5 (step S9), and if it is not the off key 5, it is input. The calculation is performed on the key signal, and the calculation result is stored in the X register (step S1.
0) and then jump to step S6 to clear the APO counter and display the contents of the X register for the input key signal (step S7). After that, the loop from step S6 to step S10 is executed for each key input. The calculation is repeated for each input key signal, the calculation result is stored in the X register, and in the memory calculation mode, the calculation result is also stored in the M register (step S10).

Further, when the off key 5 is input or the APO counter counts up, the specific mode switching signal becomes low level (step S13), and the DC
-After the driving of the DC converter 6 is stopped, the off mode is entered and the standby state is entered (step S14). In this standby state, key input waiting is continued until the ON key 2 is input (step S15) and (step S16). If there is a key input from the ON key 2, the process jumps to step S3 and the same operation is performed thereafter. Here, the stored contents of the M register are retained in either the off mode or the on mode in which the standby state is set.

FIG. 3 shows the overall block configuration of the central processing unit 1.
Is based on the signal input from the key matrix 9, the power-on ACL means 10, and the power supply unit 13 including the adapter A or the battery B shown in FIG.
11 Controls the entire device such as the printer 12.

<Effects of the Invention> As described above, according to the display tube display type electronic device of the present invention, even when a resistor or the like for surely turning off the switching element of the mode switching circuit is provided, it is turned on or turned on. Instantly raise the input power supply voltage from the memory holding circuit to the central processing unit at the time of key input of the operation key to reliably switch the mode switching circuit and activate the DC-DC converter to put the fluorescent display in the display state. You can

[Brief description of drawings]

1 is an electric circuit diagram of an embodiment of the present invention, FIG. 2 is a flow chart of software of the central processing unit of FIG. 1, FIG. 3 is a block diagram showing the overall configuration, and FIG. 4 is FIG. 5 is a waveform diagram of the V _DD voltage of FIG. 5, FIG. 5 is an electric circuit diagram of a conventional device, and FIG. 6 is a waveform diagram of the V _DD voltage of FIG. 1 ... Central processing unit 2 ... ON key (mode setting key) 4 ... Mode switching circuit 5 ... OFF key (mode setting key) 6 ... DC-DC converter 7 ... Fluorescent display tube 8 ...... Memory holding circuit Z1 ...... Zener diode (constant voltage means) R9 ...... Resistance C6 ...... Bypass capacitor

Claims (1)

[Scope of utility model registration request] 1. A central processing unit for outputting a mode switching signal for switching an operating state of a fluorescent display tube constituting a display section between an on mode and an off mode by a mode setting key, and a direct current input voltage which is made constant. DC for supplying a display voltage to the fluorescent display tube and a driving power supply to the central processing unit
-DC converter and the input stage of this DC-DC converter, the DC by the mode switching signal of the central processing unit
A mode switching circuit that disconnects and supplies the DC input voltage to the DC converter, and a drive voltage that is connected to the input stage of the mode switching circuit and that puts the central processing unit in a standby state based on the DC input voltage in the off mode. A memory holding circuit for generating and supplying the central processing unit with a constant voltage when the memory holding circuit is switched from the off mode to the on mode by the mode setting key or when the power is turned on. Regardless of the means, a display tube display type electronic device characterized in that a resistor for supplying a drive voltage to the central processing unit based on a DC input voltage and a bypass capacitor are inserted and connected to the constant voltage means.