JP2008083374A - Power-saving of lcd function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an LCD driving circuit and a liquid crystal display apparatus which reduce power consumption by on-off driving specific segments without resetting a microcomputer from a standby mode to normal operation. <P>SOLUTION: The LCD drive circuit dynamically drives a liquid crystal display part with a plurality of segments using a plurality of segment signals and a plurality of common signals. In this case, the LCD drive circuit is provided with a timer circuit 12 which outputs a periodic timer signal showing an on-off period, and a multiplexor 14 which is inserted in signal lines SEG_ON, SEG_OFF for transmitting specific signals to indicate turning-on or turning-off of the specific segment, and outputs an on-off signal SEG_C in the down-stream from the signal line to indicate turning on-off to the specific segment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an LCD driving circuit and a liquid crystal display device for blinking a specific segment of a display device during a standby mode of a microcomputer.

  Conventionally, a liquid crystal display device (hereinafter referred to as an LCD) is used as a display device for home appliances such as a remote controller and a rice cooker. In order to express that the second is counted when displaying the clock or cooking time on the LCD display, “:”, “.”, And the like of the LCD segment are blinked at a cycle of 1 second. This blinking pattern is created by using microcomputer software or an LCD driver IC that can generate a blinking pattern (for example, see Patent Document 1).

  FIG. 11 is a diagram showing a connection example of an LCD tube that is dynamically driven with a 1/4 duty. The LCD tube 101 shown in the figure has four common signal lines and four segment signal lines. Four segments are connected to each common signal line or each segment signal line. Each segment is connected to the intersection of the common signal line and the segment signal line. Each segment is turned on when the potential difference between the common signal connected thereto and the segment signal is larger than a predetermined value, and is turned off when the potential difference is smaller. The common signals COM1 to COM4 are sequentially driven at a 1/4 duty within one cycle.

  FIG. 10 is a block diagram showing a configuration of an LCD drive circuit built in a microcomputer according to the prior art. The microcomputer MCU includes a segment driver 104 that drives the segment signals SEG1 to SEG4, a common driver 105 that drives the common signals COM1 to COM4, a segment output latch 106 that holds segment data indicating whether the segments are turned on / off, A timing controller 107 that outputs a signal driving timing signal and a multiplexer 108 that selects segment data are provided.

  The segment output latch 106 holds segment data indicating ON / OFF of the number of segments × the number of COM signal lines. The multiplexer 108 supplies the signal to the segment driver 104 while switching in synchronization with the drive timing signal from the timing controller 107. The drive timing signal indicates the timing of COM1 to COM4 within the dynamic drive period.

  FIG. 12 is a time chart showing the driving timing of the common signal and the segment signal. The common signals COM1 to COM4 are periodically turned on in this order. Here, the turning on of the common signal means a level (VLC1 or Vss) that enables lighting as in the periods t1 and t2. The segment output latch 106 holds (ON, ON, OFF, OFF) as data indicating lighting / extinguishing of the four segments connected to the segment signal SEGx (x is any one of 1 to 4). When the potential difference between the segment signal and the common signal is VLC1-Vss, the segment is lit. The segment connected to the common signal COM1 is lit at the timing t1 in the figure, and the segment connected to the common signal COM2 is lit at the timing t2 in the figure. Thereby, the segment connected to the segment signal SEGx and the common signal COM1 and the segment connected to the segment signal SEGx and the common signal COM2 appear to be continuously lit.

As described above, the conventional LCD driving circuit drives the segment in correspondence with the combination of the segment signal and the common signal, so the number of signal lines is reduced.
JP-A-5-88637

  By the way, in a device that operates using a dry battery such as a remote controller, it is necessary to blink a specific segment even if the microcomputer is set to the standby mode for power saving. The specific segment is, for example, “.” Or “:”.

  However, the above-described prior art has a problem that it is necessary to return the microcomputer from the standby mode to the normal mode and perform software control in a short cycle, and use wasted power. For example, when the “.” Segment is blinked at a 500 ms cycle to represent the count of seconds on a clock display, etc., the microcomputer is conventionally returned from standby mode to normal operation every 500 ms (120 times per minute). I am letting.

  Moreover, although the said subject can be solved by using the LCD driver IC which produces | generates the said blink pattern, there exists a subject to which cost becomes high for LCD driver IC.

  The present invention solves the above-described conventional problems, and provides an LCD driving circuit and a liquid crystal display device that can drive a specific segment in a blinking manner and reduce power consumption without returning to normal operation from a standby mode of a microcomputer. With the goal.

  An LCD driving circuit according to the present invention for solving the problem is an LCD driving circuit that dynamically drives a liquid crystal display unit having a plurality of segments by using a plurality of segment signals and a plurality of common signals, and exhibits a blinking cycle. A timer circuit that outputs a periodic timer signal and a signal line that transmits a specific signal for instructing to turn on or off a specific segment are inserted into the specific segment in accordance with the timer signal. And switching means for switching the blinking signal and the specific signal to output downstream of the signal line. Here, the signal line is preferably dedicated to the specific segment.

  According to this configuration, since the specific LCD segment is driven to blink in accordance with a periodic timer signal indicating the blinking period, it is not necessary to return the microcomputer to the normal operation from the standby mode for the blinking, thereby reducing power consumption. be able to. Further, the blinking cycle can be arbitrarily changed by setting from the microcomputer to the timer circuit.

  Here, the LCD driving circuit is further incorporated in a microcomputer, and as the specific lighting signal, an on signal for instructing to turn on the specific segment and an off signal for instructing to turn off the specific segment, The switching means alternately selects the on signal and the off signal according to the timer signal, outputs the selected signal as the blinking signal, and the output of the switching means The signal may be supplied to the specific segment connected to the signal line.

  According to this configuration, if a timer circuit built in the microcomputer is used with respect to the conventional microcomputer having an LCD driving function, for example, a multiplexer is added as a switching means, and an on signal and an off signal are output. This can be easily realized simply by adding a function to the segment driver, and the LCD driving circuit of the conventional microcomputer can be used effectively.

  Here, each of the common signals is driven with a first potential, a second potential, and at least one intermediate potential that is an intermediate potential between the first and second potentials, and the LCD driving circuit further includes: An inversion circuit that generates the specific signal by inverting a common signal supplied to the specific segment, and a determination circuit that determines whether the common signal supplied to the specific segment is at an intermediate potential. An AND circuit that takes a logical product of the determination result of whether or not the intermediate potential is in the determination means and the timer signal, and the switching means performs the inversion according to the logical product output from the AND circuit The lighting signal from the circuit and a signal indicating an intermediate potential are alternately selected, the selected signal is output as the blinking signal, and the output of the switching means is the specific segment connected to the signal line It may be supplied.

  According to this configuration, a timer circuit built in the microcomputer can be obtained by adding a few circuits such as an inverting circuit, a determination circuit, and a switching means (multiplexer) to the outside of the conventional microcomputer having an LCD drive function (on the printed circuit board). Thus, the LCD drive function can be used effectively without adding a terminal to the conventional microcomputer.

  Here, the LCD driving circuit further includes a register built in the microcomputer and holding a flag indicating whether or not to request the blinking of the specific segment, and the signal line into which the switching circuit is inserted is , A signal line for transmitting the data corresponding to the specific segment among the segment data input to the segment driver as the specific signal, and when the flag requests the blinking, the switching circuit The blinking signal may be output according to a timer signal.

  According to this configuration, a specific segment can be driven to blink only by adding a few circuits (a flag holding register and a simple logic circuit) inside a conventional microcomputer with an LCD drive function.

  Here, the switching means alternately selects an inverted signal obtained by inverting the specific signal and the specific signal according to the timer signal, outputs the selected signal as the blinking signal, and outputs the switching means May be supplied to the specific segment connected to the signal line.

  According to this configuration, the blinking operation of the specific segment can be statically driven by switching between the timer signal and its inverted signal.

  Here, the LCD driving circuit is further built in the microcomputer, and a selection circuit for sequentially selecting data corresponding to each common signal among the segment data, and a signal line into which the switching circuit is inserted are A signal line that transmits data corresponding to the specific segment of the segment data as the specific signal between the data holding unit and the selection circuit, and the switching circuit requests the flag to blink. The blinking signal may be output according to the timer signal.

  According to this configuration, the blinking control of a specific segment can be performed by adding simple hardware without adding a circuit outside the microcomputer.

  Further, the liquid crystal display device of the present invention has the same configuration as described above, and has the same effect.

  As described above, according to the present invention, LCD segment blink drive can be performed in the standby mode without returning the microcomputer from the standby mode for software control in order to display blinking of a specific segment. For example, in a clock display without a second digit, it is only necessary to return to the normal operation from the standby mode only once per minute in order to update the minute digit, and the power consumption of the microcomputer can be suppressed.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
In this embodiment, an LCD driving circuit and an LCD display device that perform blinking driving of a specific segment using a timer circuit, a segment driver, and a selection circuit (multiplexer) that operate even when the microcomputer is in a standby mode will be described.

  FIG. 1 is a block diagram showing a configuration of an LCD display device according to Embodiment 1 of the present invention. The LCD display device of the figure shows an LCD drive circuit provided inside and outside the microcomputer MCU and an LCD tube 15. The LCD driving circuit includes a segment driver 4, a common driver 5, a segment output latch 6, a timing controller 7, a multiplexer 8, and a timer circuit 12.

  The segment driver 4 drives the segment signal SEG_ON and the segment signal SEG_OFF in addition to driving the segment signals SEG1 to SEG4 similar to the conventional technology. The segment signal SEG_ON is a signal for instructing lighting of a specific segment to be blinked. The segment signal SEG_OFF is a signal that instructs the specific segment to be blinked to be turned off. The segment signal SEG_ON and the segment signal SEG_OFF are alternately connected to a specific segment via the multiplexer 14. In the figure, segment signals SEG1 to SEG4 are omitted.

  The common driver 5 drives the common signals COM1 to COM4. The common signals COM1 to COM4 are sequentially turned on with 1/4 duty within one cycle.

  The segment output latch 6 holds segment data indicating lighting / extinguishing of each segment.

  The timing controller 7 outputs a timing signal indicating the output timing of each common signal.

  The multiplexer 14 selects the segment signal SEG_ON when the timer signal TMO from the timer circuit 12 is at a high level, and selects the segment signal SEG_OFF when the timer signal TMO is at a low level. Thereby, according to the timer signal TMO from the timer circuit 12, the segment signal SEG_ON and the segment signal SEG_OFF are alternately selected and output to the specific segment as the segment signal SEG_C. As a result of alternately selecting the segment signals SEG_ON and SEG_OFF, the specific segment blinks.

  The timer circuit 12 operates even when the microcomputer MCU is in the standby mode, and outputs a timer signal TMO indicating a cycle for blinking a specific segment. The cycle of the timer signal TMO is, for example, 0. It may be several seconds or around 1 second.

  FIG. 2 is a diagram showing a connection example of the LCD tube 15. The LCD tube 15 shown in the figure has 16 segments representing the characters “8.8.”, Four common signals COM1 to COM4, four segment signal lines SEG1 to SEG4, and a segment signal SEG_C. . A segment indicating “.” On the left side is a specific segment to be blinked and is connected to the common signal COM4 and the segment signal SEG_C. Only the segment to be blinked is connected to the segment signal SEG_C.

  Four segments are connected to each common signal line. Four segments are connected to the segment signal lines SEG1, 3, 4 and three segments are connected to the segment signal line SEG2. The segment signal line SEG_C is not connected to a plurality of segments, but is connected only to the specific segment. Each segment is lit when both the common signal and the segment signal connected thereto are valid (that is, when the potential difference between the common signal and the segment signal S is VLC1-Vss), and is extinguished when one is invalid. To do.

  FIG. 3 is a timing chart showing the drive timing of the LCD display device. In the figure, a common signal COM4, segment signals SEG_ON, SEG_OFF, a timer signal TMO, and a segment signal SEG_C are shown.

  As shown in the figure, the common signal COM4 is effective in a period of 1/4 of the dynamic lighting cycle T. The segment signal SEG_ON is output so as to be valid during the valid period of the common signal COM4. The segment signal SEG_OFF is output so as to be invalid during the valid period of the common signal COM4. The timer signal TMO repeatedly outputs a high level and a low level with a blinking cycle of about 1 second.

  The specific segment is connected to the common signal COM4 and the segment signal SEG_C. When the timer signal TMO is at a high level, the potential difference from the segment signal SEG_C becomes VLC1-Vss, so that the specific segment is lit. When the timer signal TMO is at a low level, the potential difference from the segment signal SEG_C is smaller than VLC1-Vss, so that the specific segment is turned off. The multiplexer 8 alternately selects the segment signal SEG_ON and the segment signal SEG_OFF in the cycle of the timer signal TMO and outputs it as the segment signal SEG_C. As a result, the specific segment repeats lighting and extinguishing, that is, blinks, in synchronization with the cycle of the high level and low level of the timer signal TMO. Note that during the period in which the timer signal TMO is at a high level, the specific segment is dynamically lit with a duty of ¼, and it appears to be lit by human eyes.

  As described above, according to the LCD drive circuit in the present embodiment, a specific LCD segment can be driven to blink without returning the microcomputer from the standby mode to the normal operation. Further, it can be easily realized by adding a timer circuit 12 and a multiplexer 14 to the conventional microcomputer having an LCD driving function and adding functions to the segment driver 6, and the conventional LCD driving circuit for the microcomputer. Can be used effectively.

  In FIG. 1, only the multiplexer 14 is mounted outside the microcomputer MCU, but the entire LCD drive circuit may be mounted inside the microcomputer MCU, or a part thereof may be mounted. However, if a timer built in the microcomputer MCU is used as the timer circuit 12 as shown in FIG. In other words, the present invention can be easily applied to a conventional microcomputer MCU having an LCD drive function only by attaching the multiplexer 14 externally.

  Further, in the present embodiment, the segment signal SEG_C is connected only to a specific segment (“.” In FIG. 2), but may be connected to another segment for which blinking is desired.

  The common signal COM_C is connected to the specific segment (“.” In FIG. 2) instead of the segment signal SEG_C, and the segment driver 4 outputs the common signals COM_ON and COM_OFF instead of the segment signals SEG_ON and SEG_OFF. The output may be the common signal COM_C.

(Embodiment 2)
In the first embodiment, two segment signals SEG_ON and SEG_OFF are required. In the second embodiment, a configuration that does not require the two segment signals will be described. The LCD segment is lit when the potential difference between the SEG signal and the COM signal is Vss-VLC1. The LCD drive circuit according to the second embodiment supplies a signal that is physically inverted from the COM signal corresponding to this segment to the specific segment as the segment signal SEG_C in the lighting period within the blinking cycle, thereby obtaining the Vss-VLC1. It is configured to create a potential difference and light a specific segment.

  FIG. 4 is a block diagram showing a configuration of the LCD display device according to Embodiment 2 of the present invention. FIG. 5 is a timing chart of each signal of the LCD display device.

  Compared with FIG. 1, the LCD display device of FIG. 4 includes a point where the multiplexer 14 is deleted, a point that a segment driver 4a is provided instead of the segment driver 4, a comparator circuit 16, an AND circuit 18, an inverting circuit 19 and The difference is that a multiplexer 21 is added. Components having the same reference numerals as those in FIG.

  The segment driver 4a does not generate and output the segment signals SEG_ON and SEG_OFF of the first embodiment, and drives the segment signals SEG1 to SEG4 as in the conventional case.

  The comparator circuit 16 receives the common signal (here COM4) connected to the specific segment to be blinked and the reference voltages Vref1 and Vref2, and the voltage of the common signal COM4 as shown in the timing chart of FIG. However, when it is within the range from the reference voltage Vref1 to Vref2, it outputs a high level, and when it is outside the range from the reference voltage Vref1 to Vref2, it outputs a low level. Here, the reference voltage Vref1 corresponds to an intermediate potential between Vss and VLC3, and the reference voltage Vref2 corresponds to an intermediate potential between VLC2 and VLC1. Thus, if the input signal (common signal COM4 in FIG. 5) is an intermediate level (VLC2, VLC3), the comparator circuit 16 outputs a high level, and if it is a level outside that range (VLC1, Vss). In this case, a low level is output (CTL signal in FIG. 5). Such a comparator circuit 16 can be constituted by, for example, two comparators, two diodes, a pull-up resistor, and two reference voltage sources.

  The AND circuit 18 takes the logical product of the inverted signal of the output of the comparator circuit 16 (CTL signal in FIG. 5) and the timer signal TMO17 from the timer circuit 12 in the microcomputer MCU. As a result, the AND circuit 18 masks the output signal CTL of the comparator circuit 16 when the timer signal TMO17 is at a low level (during the extinguishing period within the blinking cycle), and when the timer signal TMO17 is at a high level (within the blinking cycle). The output signal CTL of the comparator circuit 16 is inverted and output during the lighting period.

  The inverting circuit 19 inverts the common signal COM4. Since the COM signal has intermediate potentials VLC2 and VLC3, the inverting circuit 19 can logically invert VCL1 and Vss that are not intermediate potentials, but cannot logically invert the intermediate potentials VLC2 and VLC3 to intermediate potentials. Therefore, the period during which the comparator circuit 16 is at the intermediate potential level is determined, and the MUX 21 outputs the segment signal SEG_C corresponding to VLC3 during the period at the intermediate potential level.

  The multiplexer 21 selects the output signal of the inverting circuit 19 when the output signal of the AND circuit 18 is at a high level (the lighting period within the blinking period and the CTL signal is at the low level), and the output signal of the AND circuit 18 is at the low level. When (when the light is extinguished within the blinking period), the fixed level VLC3 is selected. As a result, the multiplexer 21 outputs the inverted signal of the common signal COM4 as the segment signal SEG_C when the voltage of the common signal COM4 is VLC1 and during the period of Vss. Accordingly, the segment signal SEG_C becomes an inverted signal of the common signal COM4 during the lighting period within the blinking period and when the CTL signal is at a low level, when the voltage of the common signal COM4 is VLC1, and during the period of Vss. Therefore, the specific segment is turned on.

  As described above, the LCD display device according to the present embodiment can drive a specific LCD segment in a blinking manner without returning the microcomputer from the standby mode to the normal operation as in the first embodiment. In the first embodiment, two segment signals SEG_ON and SEG_OFF are required, but in the second embodiment, the segment signals are not required.

  Further, by using the LCD tube of the current technology and the LCD driving circuit in the microcomputer, a specific LCD segment can be driven to blink even in the microcomputer standby mode. Further, it is not necessary to use an extra microcomputer terminal.

(Embodiment 3)
In the LCD drive circuit of the third embodiment, data specifying ON / OFF of a specific segment is blinked using a timer signal TMO between a multiplexer and a segment driver that select segment data output from the segment output latch. It is comprised so that it may change into the data which show.

  FIG. 6 is a block diagram showing the configuration of the LCD display device according to Embodiment 3 of the present invention. Compared with FIG. 1, the LCD display device of FIG. 6 is different from that of FIG. 1 in that the multiplexer 14 is deleted, a blinking request register 28, an OR circuit 29, and an AND circuit 30 are added, and a segment driver 4 is used instead of the segment driver 4. The difference is that the driver 4b is provided. Since the components with the same reference numerals as those in FIG.

  The blink request register 28 holds a blink request flag and outputs a blink request signal indicating its value. Here, the blink request flag “1” means that the specific segment is requested to blink, and the blink request flag “0” does not require. The blink request flag is set by the CPU of the microcomputer MCU.

  The OR circuit 29 outputs a logical sum of the timer signal TMO and the inversion of the blink request signal. That is, the OR circuit 29 outputs the timer signal TMO as it is when the blinking request signal indicates that blinking is requested, and masks the timer signal TMO when the blinking request signal indicates that blinking is not requested (here, the high level signal). Is output).

  The AND circuit 30 is a logical product of data indicating ON / OFF corresponding to a specific segment (hereinafter referred to as specific segment data) among the segment data held in the segment output latch 6 and the output of the OR circuit 29. Is output to the segment driver 4b. In other words, when the blink request signal indicates that blinking is not requested, the AND circuit 30 outputs the specific segment data as it is. On the other hand, when the blink request signal indicates that blink is requested and the specific segment data indicates lighting, the AND circuit 30 outputs data to be turned on / off at the cycle of the timer signal TMO to the segment driver 4b. However, even if the blink request signal indicates that blinking is requested, when the data corresponding to the specific segment indicates extinguishing, the output of the AND circuit 30 indicates OFF (extinguishment).

  The segment driver 4b drives the segment signal SEG_C to the specific segment to be blinked according to ON / OFF of the output of the AND circuit 30 in addition to driving the segment signals SEG1 to SEG4 similar to the conventional technology.

  With the above configuration, the specific segment data is specified to be turned on / off according to the flag value of the blink request register and the timer signal TMO between the multiplexer 8 that selects the segment data and the segment driver 4b. Drive the segment blinking.

  According to the LCD drive circuit of the present embodiment, a specific LCD segment can be driven to blink without returning the microcomputer from the standby mode to the normal operation. In addition, a specific circuit is simply added to the inside of the microcomputer MCU (OR circuit 29, AND circuit 30, and blink request register 28) without providing a special circuit outside the microcomputer MCU (on the substrate). The segment can be driven to blink.

  In FIG. 6, instead of the AND circuit 30, an exclusive OR circuit for inputting an inverted signal of the OR circuit 29 and data indicating lighting / extinguishing corresponding to a specific segment may be provided. In this case, even when the data corresponding to the specific segment indicates extinction, if the blink request signal indicates that the blink is requested, a blink signal that is turned on / off in the cycle of the timer signal TMO is output.

(Embodiment 4)
The LCD drive circuit according to the fourth embodiment is configured to blink a specific segment to be blinked by static drive using a dedicated common signal and segment signal. Therefore, the LCD drive circuit is provided with a microcomputer MCU built-in timer circuit that outputs a common signal COM_C to a specific segment to be blinked, and a simple circuit (an inverting circuit and a multiplexer) outside the microcomputer MCU. The specific segment to be blinked is caused to blink using the other timer circuit.

  FIG. 7 is a block diagram showing a configuration of an LCD display device according to Embodiment 4 of the present invention. FIG. 8 is a diagram showing a connection example of the LCD tube 15a. As shown in the figure, a dedicated common signal COM_C and a segment signal SEG_C are connected to the specific segment “.” To be blinked.

  The LCD display device of FIG. 8 is different from that of FIG. 1 in that a timer circuit 12 a and an inverting circuit 34 are added and a multiplexer 35 is provided instead of the multiplexer 14. Since the same reference numerals are the same components, the description will be omitted, and different points will be mainly described.

  The timer circuit 12a is a second timer circuit built in the microcomputer MCU and outputs a common signal COM_C (pulse signal) for static driving.

The inverting circuit 34 inverts the common signal COM_C and outputs an inverted signal.
The multiplexer 35 receives the common signal COM_C and its inverted signal, selects the common signal COM_C when the timer signal TMO is at a high level, and selects the inverted signal of the common signal COM_C when the timer signal TMO is at a low level. The selected signal is output as a segment signal SEG_C to a specific segment.

  The LCD display device configured as described above will be described. When the common signal COM_C is selected by the multiplexer 35, since the potential difference of VLC1-Vss is generated in the specific segment, the specific segment is lit. When the inverted signal of the common signal COM_C is selected, no potential difference is generated in the specific segment, so the specific segment is turned off. Therefore, the specific segment blinks in synchronization with the period of the timer signal TMO.

  As described above, if the waveform of the segment signal SEG_C of the static drive and the waveform of the common signal COM_C are exactly the same (in phase), the specific segment is turned off, and if one is inverted (reverse phase), it is turned on. . The LCD display device blinks a specific segment by switching between the in-phase and the anti-phase of the segment signal SEG_C and the common signal COM_C in synchronization with the timer signal TMO.

  As described above, according to the LCD display device of the present embodiment, a specific LCD segment can be driven to blink without returning the microcomputer from the standby mode to the normal operation. Further, blinking control of a specific segment can be performed with a simple hardware configuration without providing a special circuit in the microcomputer.

  In FIG. 7, the outputs of the inverting circuit 34 and the multiplexer 35 may be connected to a specific segment as a common signal, and the common signal COM_C may be connected to the specific segment as a segment signal.

(Embodiment 5)
The LCD drive circuit according to the fifth embodiment uses the timer signal TMO as data for designating ON / OFF of a specific segment between the segment output latch and the multiplexer that selects the segment data output from the segment output latch. Is changed to data indicating blinking.

  FIG. 9 is a block diagram showing a configuration of an LCD display device according to Embodiment 5 of the present invention. Further, it is assumed that the connection to the segment of the LCD tube 101 is the same as that in FIG. The LCD display device of FIG. 9 is different from that of FIG. 1 in that a blinking request register 38, an OR circuit unit 39, and an AND circuit unit 40 are added, and the multiplexer 14 is deleted. Since the same reference numerals are the same components, the description will be omitted, and different points will be mainly described.

  The blink request register 38 holds a blink request flag corresponding to each segment and outputs the value as a blink request signal. The number of blink request flags is (number of segment signals × number of common signals) or the number of mounted segments. In this embodiment, the blink request register 38 holds 16 blink request flags. Each blink request flag “1” requests blinking of the corresponding segment, and the blink request flag “0” means that blinking is not requested. Each blink request flag is set by the CPU of the microcomputer MCU.

  The OR circuit unit 39 outputs a logical sum of the timer signal TMO and the inversion of each blink request signal to the AND circuit unit 40. Although only four OR gates are shown in the OR circuit unit 39 in FIG. 9, the OR circuit unit 39 includes 16 OR gates corresponding to 16 segments of the LCD tube. Each OR gate outputs the timer signal TMO as it is when the blink request signal indicates that blink is requested. This output (timer signal TMO) instructs the AND circuit unit 40 in the subsequent stage to blink the corresponding segment.

  On the other hand, each OR gate masks the timer signal TMO (in this case, outputs a high level) when the blink request signal indicates that no blink is requested. This output (high level) instructs the AND circuit unit 40 in the subsequent stage not to blink the corresponding segment.

  The AND circuit unit 40 outputs the ethical product of the segment data held in the segment output latch 6 and the output of the OR circuit unit 39 to the segment driver 4b. Although only four AND gates are shown in the AND circuit unit 40 in FIG. 9, the AND circuit unit 40 includes 16 AND gates corresponding to the 16 segments of the LCD tube. Each AND gate outputs, to the segment driver 4b, a logical product of the bit indicating lighting / extinguishing of the corresponding segment in the segment data and the output of the corresponding OR gate. In other words, when the output of the corresponding OR gate is at a high level, each AND gate outputs the bit indicating lighting / extinguishing of the corresponding segment as it is, and the output of the corresponding OR gate has the same timer signal TMO. At this time, a bit indicating lighting of the corresponding segment is output as a bit blinking in the timer signal TMO cycle.

  The operation of the LCD display device configured as described above will be described. The AND circuit unit 40 outputs the segment data as it is when the blink request signal indicates that blinking is not requested for each bit corresponding to the segment. On the other hand, for each bit corresponding to the segment, the AND circuit unit 40 indicates that the blink request signal requests blinking, and when the segment data indicates lighting, for each bit corresponding to the segment signal and the common signal, Data to be turned on / off in the cycle of the timer signal TMO is output to the segment driver 4b. As described above, the LCD driving circuit in the present embodiment can be blinked for each segment at the cycle of the timer signal TMO. As long as the microcomputer MCU sets the blink request flag corresponding to the desired segment to be blinked, the LCD drive circuit blinks the segment even after the microcomputer MCU enters the standby mode.

  With the above configuration, the microcomputer MCU can be blinked not only for a specific segment but also for an arbitrary segment without returning to normal operation from the standby mode. In the third embodiment, it is necessary to add a terminal for the segment signal SEG_C of the microcomputer to one specific segment to be blinked. However, in this embodiment, it is not necessary to add a terminal. In the present embodiment, it is necessary to provide a lighting request register for holding a lighting request flag for each segment inside the microcomputer MCU. However, not only a specific segment but also any segment blinks without forming a special circuit outside. Drive can be performed.

  In the fifth embodiment, the blink request register 38 holds only the blink request flag corresponding to one or more desired segments to be blinked, and the OR circuit unit 39 and the AND circuit unit 40 also include the one or more blinking request flags. An OR gate and an AND gate corresponding to the segment may be provided. For example, as in the first to fourth embodiments, a blink request register that holds only the blink request flag corresponding to the “.” Segment, and an OR gate and an AND gate corresponding thereto may be provided. In this way, an increase in the circuit inside the microcomputer MCU can be minimized.

  The LCD display device according to the present invention does not require flashing control by software in a display device that requires flashing display, and aims for a power saving effect until the microcomputer can be set in the standby mode. This is useful for home appliances that are driven by dry batteries such as remote controls and digital watches.

1 is a block diagram showing a configuration of an LCD display device in Embodiment 1. FIG. 3 is a diagram showing an example of connection of an LCD tube 15. FIG. It is a timing chart figure which shows the drive timing of a LCD drive circuit. FIG. 10 is a block diagram showing a configuration of an LCD display device in a second embodiment. It is a figure which shows the timing chart of each signal of a LCD display device. FIG. 10 is a block diagram showing a configuration of an LCD display device in a third embodiment. FIG. 10 is a block diagram showing a configuration of an LCD display device in a fourth embodiment. It is a figure which shows the example of a connection of the LCD pipe | tube 15a. FIG. 10 is a block diagram showing a configuration of an LCD display device in a fifth embodiment. It is a figure which shows the example of a connection of the LCD pipe | tube dynamically driven by a 1/4 duty. It is a block diagram which shows the structure of the LCD drive circuit built in the microcomputer in a prior art. It is a time chart which shows the drive timing of a common signal and a segment signal.

Explanation of symbols

1 LCD tube 2 SEG signal 3 COM signal 4 Segment driver 5 Common driver 6 Segment output latch 7 Timing control 8 Multiplexer 12 Timer circuit 14 MUX (switching circuit)
15 LCD tube 16 Comparator circuit 17 Flashing control pulse signal 18 AND circuit 19 Inversion circuit 20 VLC3 level input 21 Multiplexer 22 Multiplexer 23 LCD tube 24 Vref1
25 Vref2
28 Flashing request register 29 OR circuit 30 AND circuit 31 LCD tube 35 Multiplexer 38 Flashing request register 39 OR circuit unit 40 AND circuit unit

Claims (12)

An LCD driving circuit that dynamically drives a liquid crystal display unit having a plurality of segments using a plurality of segment signals and a plurality of common signals,
A timer circuit for outputting a periodic timer signal indicating a blinking cycle;
Switching that is inserted into a signal line that transmits a specific signal for instructing to turn on or off a specific segment, and that outputs a flashing signal that instructs the specific segment to flash in accordance with the timer signal downstream of the signal line And an LCD driving circuit. The LCD driving circuit further includes:
A segment driver built in the microcomputer, which outputs an on signal for instructing lighting to the specific segment and an off signal for instructing to turn off the specific segment as the specific lighting signal,
The switching means alternately selects the on signal and the off signal according to the timer signal, and outputs the selected signal as the blinking signal,
The LCD driving circuit according to claim 1, wherein an output of the switching unit is supplied to the specific segment connected to the signal line. Each of the common signals is driven with a first potential, a second potential, and one or more intermediate potentials that are intermediate potentials between the first and second potentials,
The LCD driving circuit further includes:
An inverting circuit for generating the specific signal by inverting the common signal supplied to the specific segment;
A determination circuit for determining whether or not a common signal supplied to the specific segment is at an intermediate potential;
An AND circuit that takes a logical product of the determination result of whether or not the intermediate potential is at the determination means and the timer signal;
The switching unit alternately selects the lighting signal from the inverting circuit and a signal indicating an intermediate potential in accordance with a logical product output from the AND circuit, and outputs the selected signal as the blinking signal.
The LCD driving circuit according to claim 1, wherein an output of the switching unit is supplied to the specific segment connected to the signal line. The LCD driving circuit further includes:
A register that is built in the microcomputer and holds a flag indicating whether or not to request blinking of the specific segment;
The signal line into which the switching circuit is inserted is a signal line that transmits data corresponding to the specific segment among the segment data input to the segment driver as the specific signal,
The LCD driving circuit according to claim 1, wherein the switching circuit outputs the blinking signal according to the timer signal when the flag requests blinking. The switching means alternately selects an inverted signal obtained by inverting the specific signal and the specific signal according to the timer signal, and outputs the selected signal as the blinking signal.
The LCD driving circuit according to claim 1, wherein an output of the switching unit is supplied to the specific segment connected to the signal line. The LCD driving circuit further includes:
A selection circuit that is built in the microcomputer and sequentially selects data corresponding to each common signal among the segment data;
The signal line into which the switching circuit is inserted is a signal line that transmits data corresponding to the specific segment of the segment data as the specific signal between the data holding unit and the selection circuit,
The LCD driving circuit according to claim 1, wherein the switching circuit outputs the blinking signal according to the timer signal when the flag requests blinking. A liquid crystal display connected to a plurality of segment signals and a plurality of common signals;
A timer circuit that is built in the microcomputer and outputs a periodic timer signal indicating the blinking cycle;
Switching that is inserted into a signal line that transmits a specific signal for instructing to turn on or off a specific segment, and that outputs a flashing signal that instructs the specific segment to flash in accordance with the timer signal downstream of the signal line Means and
The liquid crystal display device, wherein the signal line is connected only to the specific segment. The LCD display circuit further includes:
A segment driver that is built in the microcomputer and outputs an on signal that instructs lighting of the specific segment and an off signal that instructs to turn off the specific segment as the specific signal;
The switching means alternately selects the on signal and the off signal according to the timer signal, and outputs the selected signal as the blinking signal,
The liquid crystal display device according to claim 7, wherein an output of the switching unit is supplied to the specific segment connected to the signal line. Each of the common signals is driven with a first potential, a second potential, and one or more intermediate potentials that are intermediate potentials between the first and second potentials,
The liquid crystal display device further includes:
An inverting circuit for generating the specific signal by inverting the common signal supplied to the specific segment;
A determination circuit for determining whether or not a common signal supplied to the specific segment is at an intermediate potential;
An AND circuit that takes a logical product of a determination result that is not at an intermediate potential by the determination means and the timer signal;
The switching unit alternately selects the lighting signal from the inverting circuit and a signal indicating an intermediate potential in accordance with a logical product output from the AND circuit, and outputs the selected signal as the blinking signal.
The liquid crystal display device according to claim 7, wherein an output of the switching unit is supplied to the specific segment connected to the signal line. The liquid crystal display device further includes:
A segment driver built in the microcomputer and indicating segment data indicating lighting and extinction of each segment; accordingly, a segment driver for driving the plurality of segment signals;
A register that is built in the microcomputer and holds a flag indicating whether or not to request blinking of the specific segment;
The signal line into which the switching circuit is inserted is a signal line that transmits data corresponding to the specific segment among the segment data input to the segment driver as the specific signal,
The liquid crystal display device according to claim 7, wherein the switching circuit is built in the microcomputer and outputs the blinking signal according to the timer signal when the flag requests blinking. The switching means alternately selects an inverted signal obtained by inverting the specific signal and the specific signal according to the timer signal, and outputs the selected signal as the blinking signal.
The liquid crystal display device according to claim 7, wherein an output of the switching unit is supplied to the specific segment connected to the signal line. The liquid crystal display device further includes:
A data holding unit built in the microcomputer for holding segment data indicating lighting and extinguishing of each segment;
A selection circuit that is built in the microcomputer and sequentially selects data corresponding to each common signal among the segment data;
A segment driver built in the microcomputer and driving the plurality of segment signals according to data output from a selection circuit;
The signal line into which the switching circuit is inserted is a signal line that transmits data corresponding to the specific segment of the segment data as the specific signal between the data holding unit and the selection circuit,
The liquid crystal display device according to claim 7, wherein the switching circuit is built in the microcomputer and outputs the blinking signal according to the timer signal when the flag requests blinking.

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