JP2004163526A - Multi-output driver and fluorescent display tube module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize the output of an IC when the source voltage of a semiconductor circuit having a multiple-power-source system is off. <P>SOLUTION: A control voltage detecting circuit 1 is composed of an output power source system and its output is inputted to an output fixing circuit 3 connected to the output of a level holding circuit 2. This circuit can fix the output of the IC even when no control electric power is supplied and output electric power is left. Specially, a multi-output driver circuit which drives a display body such as a liquid crystal display, a plasma display, and a fluorescent display tube can fix the output of the IC, so that abnormal light emission of display and abnormal display can securely be eliminated. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to an output stabilization circuit for a semiconductor integrated circuit having a multiple power supply system when a power supply voltage is turned off, and more particularly to a multiple output driver circuit for driving a display such as a liquid crystal display, a plasma display, and a fluorescent display tube.
[0002]
[Prior art]
Conventional semiconductor integrated circuits (hereinafter, ICs) having multiple power supplies are:
(1) When the power supply is turned on, the power supply of the control system is supplied, and then the power supply voltage of the output system is supplied. Was giving.
[0003]
(2) A circuit in which a circuit for detecting a control system power supply voltage is provided inside an IC, and a circuit for fixing an output system circuit when the control system power supply voltage is lower than a certain voltage is provided.
[0004]
(3) There is a circuit configuration in which an output system is not always turned on unless a control system voltage is applied.
[0005]
[Problems to be solved by the invention]
However, in the case of the above configuration (1), switches for a control system and an output system are required as external circuits. In addition, a detector for voltage monitoring, a sequential circuit, a high-power transistor, and the like are required.
[0006]
In the configuration shown in FIG. 2, a circuit for monitoring the power supply voltage of the control system is formed by the control power supply system, and its output is used as the input of the level shifter of the output system. In the case of the type level shift, if the voltage of the control system is high enough to operate the power supply monitoring circuit, it operates sufficiently and the output can be fixed. Below the threshold voltage), the input transistors 21 and 22 of the level shifter are both off, and the output of the level shifter should keep the previous state. , The output may change. This is inconsistent due to differences in IC manufacturing time and the like, and sorting is difficult. The effect of this phenomenon is that, for example, a power supply of 5 V is supplied, then a second power supply of 50 V is generated through a booster circuit, and a display such as a fluorescent display tube is displayed at that voltage. When the power is turned on, the voltage of the output system gradually rises after 5 V is applied. However, when the power is turned off, 5 V immediately disappears, and the voltage of the output system gradually decreases because the charge stored in the smoothing capacitor remains. Will fall. If the output changes at this point, high light emission occurs at a specific bit. That is, an abnormal display is displayed when the power is turned off.
FIG. 3 shows the configuration as in the above (3). Reference numeral 27 denotes a potential lower than the power supply voltage of 6, which turns on 23 transistors. This is a transistor load type level shift circuit. When a high level of the control system voltage is given to the transistor 42, the output 8 is turned on (the P-channel transistor 31 is turned on). The output never turns on. However, in this type of level shift circuit, a dripping current flows between the high-voltage power supplies when the output is turned on. If this type of level shift is used for a multi-output driver, if the dripping current is 20 μA per bit and the output system voltage is 60 V, 20 μA * 60 V * 20 = 240 mW at 20 bits, so the IC package power dissipation Is set to 250 mW, it is difficult to increase the output further.
[0007]
[Means for Solving the Problems]
Means taken by the present invention in order to solve the above problems include a control circuit of a first power supply system, a level hold circuit of a second power supply system which receives an output of the control circuit as an input, In a semiconductor integrated circuit including an output circuit of a second power supply system having an input of an output of a hold circuit, a circuit configured of a second power supply system and detecting a first power supply voltage; and And a circuit for fixing the output of the level hold circuit by the signal of (1). Further, in the above semiconductor device, a circuit configured by a first power supply system and detecting a first power supply voltage, and a circuit fixing an input of a level hold circuit by a signal of the detection circuit are provided. .
[0008]
Next, a shift register configured of a control power supply system for converting serial data into parallel data, a latch circuit for latching the parallel data, a level shift circuit configured of an output power supply system and receiving the latch data, and the level shifter In a multi-output driver configured with an output circuit having an input of an output of a circuit, a circuit configured with an output power supply system for detecting a control system power supply voltage is provided, and an output of the level shift circuit is fixed by a signal of the detection circuit. A circuit is provided. The multi-output driver further includes a circuit configured with a control power supply system for detecting a control power supply voltage, and a circuit for fixing an input of a level shift circuit by a signal of the detection circuit.
[0009]
Next, a display data control is performed by a control power supply system, the control power supply is boosted to generate a display drive voltage, and the above-described multi-output driver is used in a fluorescent display tube module capable of performing display.
[0010]
[Action]
An output power supply system constitutes a circuit for detecting a drop in the control system power supply voltage, and the output of the level hold circuit is fixed at the output, whereby the output of the IC can be stabilized when the power supply is turned off.
[0011]
In order to obtain further output stability from the IC, a circuit for detecting a decrease in the control system power supply voltage is constituted by the control power supply system, and the input side of the level hold circuit is fixed at the output.
[0012]
An output power supply system constitutes a circuit for detecting a drop in the control system power supply voltage, and the output of the shift register circuit is fixed at the output, whereby the output of the multi-output driver can be stabilized when the power supply is turned off.
[0013]
In order to obtain further output stability from the multiple output driver, a circuit for detecting a decrease in the control system power supply voltage is constituted by a control power supply system, and the input side of the level hold circuit is fixed by the output.
[0014]
Among the display elements, the fluorescent display tube requires push-pull drive for both the grid and the anode, and because of its high brightness, if the control power supply is lost and the output power supply remains, the driver output is complete. If it is turned on instead of being turned off, abnormal light emission will occur with a specific character.However, if the above multi-output driver is used, the output can be completely turned off even in the above state, so that abnormal light emission does not occur. .
[0015]
【Example】
Next, embodiments of the present invention will be described with reference to the accompanying drawings.
[0016]
(Example 1)
FIG. 1 shows an embodiment of the present invention, which is an example of a multi-power-supply system IC having five control system power supplies and six output system power supplies. Reference numeral 1 denotes a circuit for detecting a power supply voltage of a control system, which is constituted by an output power supply system. Reference numeral 2 denotes a level hold circuit which is controlled by a control system signal. Reference numeral 3 denotes a circuit for directly fixing the output of the level hold circuit by using the output of 1 as an input. 4 is a control circuit. FIG. 4 shows an example of a detailed circuit. 41 is a resistor, 40 is an N-channel transistor (hereinafter, Nch-Tr), and a gate is supplied with a control system potential. The transistors 36 to 39 are buffer circuits. If the control system voltage falls below the threshold voltage of the transistor, the Nch-Tr of 40 is turned off, and the output of 44 becomes HIGH level. Reference numeral 11 denotes a flip-flop type level shift circuit. If the potential of the gate signals (control system signals) of the Nch-Trs 21 and 22 disappears due to a decrease in the control system power supply voltage, both are turned off. Output keeps the previous state and becomes the level hold state. The 32 Nch-Tr is for fixing the output of the level hold circuit, and the gate of the 32 transistor is turned to the high level when the control system voltage is lowered and is turned on, so that the output of the level shift is fixed to the LOW level. . Therefore, when the control power supply voltage decreases, the output 8 of the IC is fixed at the LOW level.
[0017]
(Example 2)
FIG. 5 shows an embodiment of the present invention, which is an example of a multi-power-supply IC having 5 control-system power supplies and 6 output-system power supplies. Reference numeral 1 denotes a circuit for detecting a power supply voltage of a control system, which is constituted by an output power supply system. Reference numeral 10 denotes a circuit for detecting a power supply voltage of the control system, which is constituted by a control power supply system. An example of the circuit diagram of FIG. 10 is shown in FIG. 6. By using a resistor 61, a reference voltage generating circuit 62, a comparator circuit 63, etc., the power supply voltage of the control system can be reduced more accurately than in the circuit of FIG. By inputting this output to the input of the level hold circuit, when the voltage of the control system decreases, 10 detection circuits operate first to fix the input of the level hold circuit, and when the control system voltage further decreases, 1 detection circuit is detected. The circuit operates to fix the output of the level hold circuit.
[0018]
(Example 3)
FIG. 7 shows an embodiment of the present invention, which is an example of a multi-output multi-output driver in which a control system power supply 88 and an output high-voltage power supply 89 exist. The shift register 73 transfers the serial data 74 with a clock 75 and holds the transferred data in a latch circuit 77 with a latch pulse 76. The latch data passes through the level shift circuit 78 and is output from the output circuit 79 through the output circuit. Reference numeral 80 denotes a circuit for monitoring a control system power supply voltage, which is configured by a high withstand voltage system power supply. When the control system potential of 81 drops, the Nch-Tr of 82 is turned off, so that 83 changes from the LOW level to the HIGH level, and the output 86 changes to the HIGH level. Since the Nch-Tr 87 is turned on, the output of the level shift is forced to the LOW level, and the output is fixed at LOW. The level shift circuit 78 is a flip-flop type and is a level hold circuit that keeps holding previous data when there is no input signal. Therefore, when the control system power supply is lost, the transfer clock signal and the latch signal also stop, and the level shift circuit keeps the state at that time. In the case where the display is performed in an AC manner by the time division driving, if the data stops, a current flows in a specific bit in a DC manner and abnormal light emission with high luminance occurs. However, in the case of the configuration as in this embodiment, if the control system power supply voltage is lost, the output is fixed at the LOW level, so that abnormal light emission does not occur.
[0019]
(Example 4)
FIG. 8 shows an embodiment of the present invention, which is an example of a multi-output multi-output driver in which a control system power supply 88 and an output high-voltage power supply 89 exist. The shift register 73 transfers the serial data 74 with a clock 75 and holds the transferred data in a latch circuit 77 with a latch pulse 76. The latch data passes through the level shift circuit 78, passes through the output circuit, and is output from 79. Reference numeral 80 denotes a circuit for monitoring a control system power supply voltage, which is configured by a high withstand voltage system power supply. When the control system potential of 81 drops, the Nch-Tr of 82 is turned off, so that 83 changes from the LOW level to the HIGH level, and the output 86 changes to the HIGH level. Since the Nch-Tr 87 is turned on, the output of the level shift is forced to the LOW level, and the output is fixed at LOW. Reference numeral 90 denotes a circuit for monitoring a control system power supply voltage, which is constituted by a control system power supply. The internal circuit has the same circuit configuration as that of FIG. With this circuit, the power supply voltage is monitored with high accuracy (about 2.5 V), the level shift input is fixed, and the output is LOW. Further, when the power supply voltage drops to about 1.0 V which is equal to or lower than the threshold voltage of the high-voltage transistor, the circuit 80 operates and the output of the level shift becomes LOW level, and the output is fixed to LOW. The level shift circuit 78 is a flip-flop type and is a level hold circuit that keeps holding previous data when there is no input signal. Therefore, when the control system power supply is lost, the transfer clock signal and the latch signal also stop, and the level shift circuit keeps the state at that time. In the case where the display is performed in an AC manner by the time division driving, if the data stops, a current flows in a specific bit in a DC manner and abnormal light emission with high luminance occurs. If the power supply voltage of the IC that generates clock and data signals also drops, the signal stops, so it is necessary to fix the output to LOW before the power supply voltage completely disappears. However, in the case of the configuration as in this embodiment, the input of the level shift can be fixed and the output can be fixed to the LOW level when the control system power supply voltage drops to about 2.5 V. When the voltage of the control system circuit including the 90 control system power supply voltage monitoring circuit does not operate, the voltage is reduced to about 1.0 V or less, the level shift retains its previous state, but the output may change due to junction leak, channel leak, etc. However, since the voltage monitoring circuit 80 operates and the output is fixed at the LOW level, abnormal light emission does not occur.
[0020]
(Example 5)
FIG. 9 shows an embodiment of the present invention. 96 is a control IC for generating display data, 92 is the multi-output driver, 93 is a booster circuit that boosts a control system voltage to generate a display drive voltage, and 94 is a fluorescent display tube. is there. 95 is a smoothing capacitor for boosted voltage. When the display is turned off, the power supply 98 of the control system is turned off by turning off the power switch 97 of the control system, the power supply voltage of the control system is reduced, and the boosting operation is also stopped. As shown in FIG. 10, when the switch is turned off at the timing of 104, the control system potential 103 immediately drops to about 1 V when electric charge is removed through the path of the transistor of the booster circuit. As a result, the voltage drops slowly. On the other hand, the boosting system potential 102 decreases slowly because the smoothing capacitor is large. In the portion 107 in the figure, the voltage of the control system transistor cannot operate, and the input of the level shift circuit in the multi-output driver becomes indefinite. However, the output is not turned on because the output of the level shift is fixed. For example, if 94 is a liquid crystal display element, an abnormal display at power-off is invisible due to the response speed of the liquid crystal. Even if the head 94 is for a thermal transfer printer, since the driver circuit is an N-ch open drain output, the output transistor has a gate voltage as long as there is only a detection circuit composed of a control system power supply voltage. , The ability to pass current is lost, and abnormal printing does not occur. In the case of a plasma display, there are row and column drivers, and the column driver is an open drain or open collector output. When the control voltage drops, the column driver does not turn on, so that abnormal light emission does not occur. However, in the case of a fluorescent display tube, the response speed is high, the brightness is high, and both the anode and grid are driven by push-pull. It emits light. Therefore, by using the multi-output driver for the fluorescent display tube module, abnormal light emission that does not appear in other display elements can be suppressed.
[0021]
【The invention's effect】
According to the semiconductor integrated circuit of the present invention, the output of the level hold circuit can be fixed when the power supply voltage of the control system decreases, so that the output of the IC can be fixed when the power is turned off. Therefore, there is no need to perform any special operation when power is externally supplied to or turned off from the multi-power supply IC, so that there is no need to attach external parts. Although the channel leak of the transistor and the junction leak of the drain portion are different due to the difference in the IC manufacturing time and the like, the sorting is difficult, but the sorting operation is not required. Even when a flip-flop type level shift circuit is used, the output can be fixed when the power is off, so that there is an effect that a multi-output driver with a free power supply sequence can be provided. Use of the multi-output driver of the present invention in a fluorescent display module has the effect of suppressing abnormal light emission when the power is turned off.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a semiconductor integrated circuit according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a circuit configuration of a conventional semiconductor integrated circuit.
FIG. 3 is a diagram showing a circuit configuration of a conventional semiconductor integrated circuit.
FIG. 4 is a diagram showing a circuit example in a first embodiment of the semiconductor integrated circuit according to the present invention.
FIG. 5 is a diagram showing a circuit example in a second embodiment of the semiconductor integrated circuit according to the present invention.
FIG. 6 is a diagram showing an example of a power supply voltage detection circuit in a second embodiment of the semiconductor integrated circuit according to the present invention.
FIG. 7 is a diagram showing a circuit example in a third embodiment of the multiple output driver according to the present invention.
FIG. 8 is a diagram showing a circuit example of a multi-output driver according to a fourth embodiment of the present invention.
FIG. 9 is a diagram showing a circuit example in a fifth embodiment of the fluorescent display tube module according to the present invention.
FIG. 10 is a diagram showing a potential change when a power supply is turned off in a fifth embodiment of the fluorescent display tube module according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Control system power supply voltage detection circuit composed of output power supply system 2 Level hold circuit 3 Output fixing circuit 4 Control circuit 5 Control system power supply 6 Output system power supply 7 Output circuit 8 Output terminal 9 Ground power supply 10 Control system power supply voltage detection circuit Flip-flop type level shift circuits 21, 22, 32-34, 38-40, 42 Nch-Tr
23, 24, 30, 31, 36, 37, 43 Pch-Tr
25 Configuration of control power supply system with AND circuit 26 Configuration of control power supply system with inverter circuit 27 Voltages 35, 41, 61 lower than output power supply voltage Resistor 62 Reference voltage generation circuit 63 Comparator circuit 73 Shift register circuit 74 Serial data input 75 Transfer Clock input 76 Latch pulse input 77 Latch circuit 78 Level shift circuit 79 Output terminal 80 Control system power supply voltage detection circuit composed of output power supply system 81 Control system potential 84 Serial data output 88 Control power supply voltage region 89 Output power supply voltage Reference numeral 90 denotes an area. A control power supply voltage detection circuit comprises a control power supply system. 92 Multi-output driver 93 of the present invention.
97 Power switch 98 Control system power supply 99 Becomes an output power supply with boosted output 100 Y axis 101 representing power supply voltage X axis 102 representing time Output power supply voltage curve 103 Control power supply voltage curve

Claims (5)

A control circuit of a first power supply system, a level hold circuit of a second power supply system that receives an output of the control circuit as an input, and an output circuit of a second power supply system that receives an output of the level hold circuit as an input And a means for detecting a first power supply voltage which is constituted by a second power supply system, and a means for fixing an output of the level hold circuit by a signal from the detection means. Semiconductor integrated circuit. 2. The semiconductor device according to claim 1, further comprising: means for detecting a first power supply voltage which is constituted by a first power supply system; and means for fixing an input of a level hold circuit by a signal of said detection means. Characteristic semiconductor integrated circuit. A shift register that converts serial data into parallel data in a first power supply system, a latch circuit that latches the parallel data, a level shift circuit that receives the latch data in a second power supply system, and an output of the level shift circuit that is input A multi-output driver constituted by an output circuit comprising: means for detecting a first power supply voltage constituted by a second power supply system; and means for fixing an output of the level shift circuit by a signal of the means. A multi-output driver. 4. The multi-output driver according to claim 3, further comprising: means for detecting a first power supply voltage which is constituted by a first power supply system; and means for fixing an input of a level shift circuit by said detection means. Features multiple output drivers. 5. A multi-output driver according to claim 3 or 4, wherein the first power supply system controls display data, boosts the first power supply, generates a display drive voltage, and performs display. A fluorescent display tube module.

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