JP2008532055A - Apparatus, method and system for driving display - Google Patents

Abstract

An apparatus, method and system for controlling a cell of an electrochromic display are disclosed. The device is connected to each cell of the display, controlled to drive the cell according to its state of charge, and outputs the characteristics of the selected cell to the sensor. The device operates in detection mode and program mode. In detection mode, the device determines the characteristics of the selected cell, and in program mode, the device sets the charge state of the cell. In a method and system for controlling a display element, a changing drive signal (such as a sawtooth signal) is applied to the display element to increase charge transfer over that produced using a constant drive signal.

Description

  The present invention relates to an apparatus, a method and a system for driving a display and a display element, in particular an electrochromic display. A typical electrochromic display consists of a glass display screen, a substrate, a track, and electrochromic segments or pixels that change color upon application of an electrical potential.

  In one embodiment, the electrochromic pixel comprises a first electrode consisting of a semiconducting metal oxide nanostructure film and a single layer of electrochromic viologen that naturally gathers. The electric charge for emitting electrochromic molecules is supplied by a second nanostructure counter electrode made of a doped semiconductor. Between these electrodes is a reflector made of a porous film of titanium dioxide.

  An electrochromic display is typically a device driven by direct current. A voltage can be applied to each segment or pixel of the display via a transparent conductive track from the edge of the glass screen to the pixel. The transparent conductive track is usually made from indium tin oxide (ITO) and acts like a resistor in series with the pixel.

  Electrochromic pixels have the same characteristics as capacitors in that they have the ability to store charge. A pixel is rendered conductive (turned on) by applying a voltage to its anode, that is, charged. The charge capacity of the pixel is proportional to the area of the pixel. Once charged, the pixel remains in an open circuit configuration and remains intact. This characteristic of electrochromic displays is called bistability. However, like a capacitor, the electric charge gradually disappears with time, and the color development of the pixels deteriorates.

This arrangement of the capacitor and the resistor determines the speed at which the pixel is charged according to the relationship dV / dt = V / RC. Thus, the speed at which individual pixels are turned on is inversely proportional to the area of the pixel and the resistance of the associated track. Thus, individual pixels are charged at different rates. Pixels, like capacitors, can be destroyed when subjected to voltages that exceed their capacitance. Thus, due to this limitation on applied voltage and the resistance of large ITO tracks coupled to large capacitance, the response time to electrochromic display switching can be quite slow.

  Exposure to ultraviolet light and voltage coupling from adjacent pixels cause potentially dangerous changes within individual pixels. If the pixel reaches the voltage capacity and is still driven, the pixel will be damaged. U.S. Pat. No. 5,973,819 discloses a driver for controlling the charge state (ie color level) of an electrochromic device. After initialization, the driver changes and measures the charge level and repeats until the maximum or minimum charge level of the electrochromic device is achieved.

In particular, US Pat. No. 5,973,819 discloses connecting one driver element in turn to each of a number of electrochromic (EC) elements via a switching matrix.
U.S. Pat.No. 5,973,819

  According to the invention, a driving device for driving a multi-cell display is connected to each cell to be driven of the display. This driving device comprises a cell driver that drives the cell according to the state of charge indicator for each cell, and a signal path that receives the characteristics of the selected cell and outputs the characteristics to the sensor. Operate. In the program mode, the charge states of the plurality of cells are set according to the charge state indicator. In the detection mode, the characteristics of the selected cell among the plurality of cells are received via the signal path, and one or more cells among the remaining cells are driven according to the state of charge indicator for that cell.

  Using the present invention, the state of one EC element can be detected while the remaining cells are driven. This provides better control of the display.

  In the preferred embodiment, potentially dangerous changes in the pixel caused by photoelectric effects, voltage coupling from other charged pixels, etc. are detected and compensated. Pixel response time is improved by using higher drive voltages in a safe, controlled environment. Once charged, the pixel is left in an open circuit state, ensuring improved pixel life. Leakage current from or between pixels can be determined using voltage detection and measurements can be made to maintain the correct look of the display.

  In another aspect, a method and system for driving a display element is provided. Here, a changing drive signal is applied to the display element, and charge transfer is improved as compared to the case of using a constant drive signal. In one embodiment, a sawtooth waveform is used to drive the display element to achieve a substantially constant charge / discharge of the display element. This method and system can be applied to a variety of display elements, including electrochromic display elements, that can show the difference in light emission between the periphery and the center. In one embodiment, the voltage at the periphery is monitored and a sawtooth waveform is used to allow charge propagation across the display element and a more accurate measurement of the state of charge at the periphery.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
Referring to FIG. 1, a system diagram of a driving apparatus 10 for driving a multi-cell display is shown. The device 10 is connected to a micro control unit 12 and an electrochromic display 14.

  The nanostructured membrane electrode of the pixel of the electrochromic display comprises a large surface area with a large number of electrochromic viologen molecules attached to the surface, allowing the viologen to be rapidly switched from colorless to colored or vice versa. Many attached viologen molecules produce intense coloration and fast electron transfer results in high switching speeds. Different colors can be achieved with different viologen molecules. The doped semiconductor electrode accumulates charge due to its high impedance, and the display device as such has a memory, resulting in bistability and low power consumption.

  In one embodiment of the invention, the device 10 comprises 65 output channels 16 named O [1], O [2],... O [64], O [65]. Each output channel 16 is connected via a corresponding conductive track 18 to the 65 cathodes of the electrochromic display 14 or one cathode 20 of the pixels 22. As will be appreciated, the number of pixels may be less than 65. Similarly, more than 65 pixels can be used by cascading many ICs.

  In one embodiment, the pixel 22 can be turned on or off by applying a dc voltage to the cathode 20. One common anode 24 corresponding to the plurality of cathodes 20 is connected to the power supply voltage Vcc. In one embodiment, a negative pixel voltage requirement is avoided by applying a positive voltage to the anode with respect to ground. When the pixel is on, the pixel voltage applied to the cathode 20 is positive but lower than Vcc.

  The output channel 16 is designed as a voltage source in which a current flows and a current flows out in order to apply an applied voltage to the connected pixel 22 as quickly as possible. Each of the 65 output channels 16 supports four voltage states. The four voltage states are two “on” voltage states, Vref1 and Vref2, an open circuit, ie, a high impedance (Hi-Z) state and an off-voltage state.

  These two “on” voltages are defined by the voltages at pins Vref1 and Vref2 provided in device 10. The current reference resistor R3 of the internal circuit and the external circuit defines a constant current source. This constant current source is used to flow out Vref2 and a pair of resistors R1 and R2 correctly determine the voltage at Vref1 and Vref2. The voltage drops at Vref1 and Vref2 remain constant with respect to Vcc because there is a constant current flowing through them, ensuring that the contrast of the electrochromic display 14 does not change when the supply voltage Vcc changes.

  This constant current is determined by the resistance value of the resistor R3 connected between the ground and the Iref pin provided in the device 10. In this embodiment, the equation for constant current is 1.25 / R3. For example, if the resistor R3 has a value of 270 kΩ, the current flowing through the resistors R1 and R2 is 1.43 μA. Similarly, if resistor R3 has a value of 888 kΩ, the current through resistors R1 and R2 is 4.6 μA. The values of R1 and R2 are set to give the required voltage drop from Vcc to drive the display 14. In this embodiment, Vref1 is set to 0.8V, which is lower than Vcc, and Vref2 is set between 1.5V and 2V, which is lower than Vcc.

  The plurality of pixels 22 assume an open circuit or high impedance state when the output channel 16 is disconnected from the pixel 22. When an “on” voltage is applied to pixel 22, pixel 22 assumes a high impedance state without any change to the display image. This is known as bistability due to the property that the pixel accumulates charge. The same display image is maintained in a period before the voltage is changed due to the leakage of electric charge and the pixel image is formed. Depending on the characteristics of the pixel, the image can last several minutes or days.

  The off state is achieved by setting the state of the output channel to Vcc, thereby eliminating the voltage drop across the pixel terminals and causing the pixel to turn off. Generally, it is considered to be off when the pixel is about 400 mV or less. When the pixel is turned off, it is set to a high impedance state. The device 10 further comprises three inputs, DATA_IN, SCLK and LOAD, which are connected to corresponding terminals 26, 28, 30 of the microcontroller unit 12. An output SENSE provided in the device 10 is connected to an analog / digital converter A / D on the micro control unit 12.

  The device 10 operates in one time in one of two modes: a program mode or a detection mode. In order to program the state of some or all pixels of the display 14, the device 10 must be operated in a program mode. In the program mode, the device 10 outputs information representing a pixel to the input DATA_IN by a clock signal output to the input SCLK. The device 10 operates in a detection mode to monitor the behavior of each of the plurality of pixels 22. In the detection mode, a signal representing the state of one pixel is output as a SENSE output, sent to the analog-digital converter A / D, and compared with a reference value by the analog-digital converter A / D. This mode allows the MCU 12 to detect pixel voltage variations due to exposure to ultraviolet light, voltage coupling to nearby pixels that are switched, pixel irregularities, response to applied voltage, and other variables. enable.

  Referring to FIG. 2, a block diagram of an apparatus 10 according to a preferred embodiment of the invention is shown. Device 10 comprises a control logic unit 32 and a 130-bit shift register 34. The shift register 34 is connected to a 130-bit latch 36. The contents of this 130-bit latch 36 are sent to 65 2-bit to 4-bit binary quaternary decoders 38. The outputs of those decoders 38 are connected to 65 corresponding CD (chromodynamic or electrochromic) drivers 40. The NCD driver is then connected to the output channel 16. The true value table for the operation of each decoder 38 is shown below as Table 1.

  The 130-bit shift register 134 is also connected to a 7-bit latch 44. The contents of the 7-bit latch 44 are sent to a 7-bit to 65-bit decoder 46. The plurality of outputs of the decoder 46 are connected to 65 switches 42 which control pixel monitoring. The 65 NCD drivers 40 are connected to 65 switches 42, which in turn output inputs to the output SENSE. Input DATA_IN is connected to a 130-bit shift register, inputs SCLK and LOAD are connected to control logic unit 32, which in turn is connected to 130-bit shift register 34 at two points. The SLCK input is an input of a clock signal and is controlled by the MCU 12. In the preferred embodiment, the maximum frequency of the clock SLCK is 10 MHz. The LOAD input takes a high level signal value or a low level signal value and is also controlled by the MCU 12. The value of the LOAD input determines whether the shift register 34 is filled with 7 bits or 130 bits.

  In order for the device 10 to operate in program mode, the micro control unit must send a low level signal value to the logic control unit 32 via the device input LOAD, as described in FIG. 3a. The microcontroller unit then provides 130 bits to register 34 via input DATA_IN. Each 130-bit binary 2-bit value represents the desired state of one of the 65 pixels.

  Data representing the desired state of each of the 65 pixels is shifted from the input DATA_IN to the shift register 34 for each transition from the low level to the high level of the SCLK clock. When the shift register 34 is filled with a 130-bit binary value, the MCU 12 outputs a high level signal value at the LOAD input, causing the contents of the shift register 34 to be loaded into the 130-bit latch 36. A plurality of decoders 38 decode the data and supply the desired state information for each pixel to the corresponding NCD driver 40. The plurality of NCD drivers 40 output the requested voltage to the output channel 16 according to Table 1, and this is applied to the pixel.

  As shown in FIG. 3b, when a high level signal value is input to the device input LOAD, the operation mode changes from the program mode to the detection mode. In the detection mode, each bit of the 7-bit binary value representing the pixel number to be detected is input to the shift register 34 at every transition from the low level to the high level of the SCLK clock. After shifting by 7 clocks, the LOAD input signal instantaneously changes from high level to low level and returns to the high level state. As a result, a 7-bit binary value is input to the 7-bit latch 44. From there, it is decoded by the decoder 46 and applied to the switch 42 corresponding to the pixel number among the 65 switches 42. The switch 42 disconnects the corresponding NCD driver 40 from the corresponding output channel 16. Thereby, the pixel 22 takes a high impedance state and enables detection of the voltage. The detected voltage is added to the SENSE output and sent to an analog / digital converter A / D provided in the micro control unit. The A / D converter converts the signal to a digital value, which is compared with a fixed reference value, and its output determines whether to change the state of the pixel 22. When detection is over, the NCD driver 40 is reconnected to its associated output channel 16.

  Referring to FIG. 4, the applied pixel voltage is illustrated with respect to time. In order to accelerate the switch operation and increase the responsiveness of the display 12, the requested pixel is driven by the voltage Vref2, exceeding the safe voltage limit of the pixel. Ideally, before the pixels are fully charged, a safe voltage Vref1 is applied to ensure that the pixels do not exceed their voltage capacity too long.

  In the first embodiment, as shown in FIG. 5, the device 10 operates in a detection mode during charging. This operation is performed until it is detected that the pixel voltage is within a predetermined range of the fixed reference voltage, that is, Vref1, and the applied voltage is changed from Vref2 to Vref1 to prevent overcharge. However, as will be appreciated, the detection mode also determines whether the pixel voltage in the high impedance state has changed and requires that the voltage Vref2 or Vref1 be applied to return the pixel voltage to the desired level. Can be used to determine. MCU 10 then sends a low level signal to the LOAD input, causing device 10 to change to program mode, and the requested voltage (including open circuit) sets the input bits for that pixel to the requested state. Is applied to the associated pixel output channel 16. Next, the device 10 returns to the detection mode.

  In other embodiments, the MCU 12 has timing information for each pixel of the display 12. This timing information is obtained from the known capacitance of each pixel and its associated ITO track resistance and outputs an estimate of the period for the application of both Vref1 and Vref2. In this embodiment, the MCU 12 timing information also includes an estimate of the time that the display 14 is colored. This timing information is used for the pixel detection schedule. If a pixel is detected by this schedule and is determined not to reach a predetermined range that defines the requirements for changing the applied voltage due to voltage variations, the timing information associated with that pixel voltage is: It is increased by a predetermined amount and the schedule is updated accordingly. Similarly, if a pixel is detected by this schedule and is determined to exceed a predetermined range that defines the requirements for changing the applied voltage due to voltage variations, the timing information associated with that pixel voltage is , Decreased by a predetermined amount, the schedule is updated accordingly, and the required voltage (including open circuit) is applied to the pixel. Similarly, if MCU 12 detects that a pixel in a high impedance state has leaked charge, it adjusts the associated timing information, updates the schedule, changes the operating mode of device 10 to program mode, Apply the required safe voltage to “replenish” the pixel with charge.

  In this preferred embodiment, the device 10 operates in the program mode and changes the applied voltage of one or more pixels according to the estimated timing information stored in the MCU 12 and the result of the detection operation. In other embodiments, the timing information is increased or decreased by an amount, directly related to the approximate charge rate of the pixel at the time the pixel was detected. In order to determine the charge rate of a pixel, the MCU 12 stores the time when each pixel enters each state.

  In other embodiments, when the detection function is performed on a pixel, the MCU 12 determines the time of that pixel and the associated voltage. The same pixel is detected again and the MCU again determines the time of that pixel and the associated voltage. The MCU uses these two results to determine the pixel charging rate and update the timing information as appropriate.

  In other embodiments, each time the detection function is used, the MCU 12 determines the first time of the pixel and the associated voltage, and then determines the second time of the pixel and the associated voltage. Before making a decision, the output channel of the pixel is momentarily reconnected to the NCD driver. These values are then used to determine the pixel charging rate and update the timing information as appropriate.

  In another embodiment, the analog to digital converter located in MCU 12 is replaced with a comparator. This comparator compares the detected voltage signal with the safety voltage Vref1. In a preferred embodiment, the device can be set to a standby state. This is accomplished by setting all output channels to a high impedance state and setting the device to program mode. In this state, the constant current sources that output the Vref1 and Vref2 voltages are shut down, causing the device to achieve very low power consumption.

  As will be appreciated, the timing information can be derived from a number of factors such as the size of the pixel, its proximity to the crossover point, the electrical conductivity of the substrate resistance, the switched condition, or a combination thereof. For example, if only one pixel is on when all other pixels are white (off), the apparent voltage on the substrate will be on due to the effect of the white pixel. The pixel is "pushed up" to a level that will develop faster than if it was one of many pixels that were turned on.

  In particular, when performing a delayed detection, a pre-programmed delay value or a currently calculated delay value is determined by comparing the size of the active area to be turned off with the size of the active area to be turned on. Can be calculated as a factor.

  For example, if a large aggregate area is switched off and a small area is switched on, a relatively large amount of charge is freed from the area that is switched off. This charge is used to develop a small area that is switched on. This large amount of excess charge results in the small area being driven to the desired voltage faster than normal, and if not taken care of, the small area will be driven too much.

  Therefore, if the driver normally waits for a delay time t1 before detecting that a pixel that has been switched on has reached the target voltage, this time t1 is obtained from a large area that is switched off. The time is reduced by adjusting by a factor, taking into account the charge to be taken.

  The above coefficient, calculated as a function of the area switched off and the area switched on, causes the pixel to be detected faster than usual in order to expect a faster charge time than normal, thereby driving The pixel is detected before it is overdoed. Conversely, if a large area is switched on and a small area is switched off, the charge availability at the anode (back) will be reduced, so it will take longer than usual to fully charge. Which can be compensated by adjusting t1 up with a factor greater than one.

  The exact details on how the coefficients are calculated depend on the characteristics of the display and the drive circuit. However, at the first level of approximation, this factor is proportional to [(area switched on) / (area switched off)].

  Furthermore, due to the resistive nature of the substrate, a plurality of pixels close to a pixel that is turned on are more affected by that pixel's switching time than a pixel that is far away. That is, the microcontroller knows the size and position of each pixel internally. At each switch, the microcontroller calculates the value of the coefficient for all pixels based on an equation relating the transition of all other pixels to the position of all other pixels.

  Again, due to the resistive nature of the substrate after the switch, multiple pixels can be in different contrasts even though their detected voltages are the same. This is due to local fluctuations in the apparent voltage of the substrate. These different contrasts can be compensated for by setting a plurality of threshold voltages for each pixel that is turned on. These threshold voltages can be calculated by the microcontroller as a function of the previously on and off pixels, the previously off and on pixels, and the position of these pixels.

  FIG. 6 shows a 7-segment display implemented using an electrochromic device as described herein. As shown in FIG. 6, the plurality of segments are considered to have a peripheral portion 60 and a central portion 61. In another embodiment, the display element is an electrophoretic element that serves as electronic ink. As used herein, the term element generally refers to a display element having segments as shown in FIG. 6, which is a type of display element. Other types of display elements (including electrophoretic display elements) with different shapes and configurations are similarly understood as elements.

  As shown in FIG. 7, the electrochromic display element is modeled as a set of distributed variable resistors and capacitors. These elements of this model are made variable because the values change over time based on the state of charge and discharge at various points in the electrochromic display element. Referring back to FIG. 7, the ANODE (anode) 70 is an anode of an electrochromic display element, and anode resistances 72, 74, 76, 78, and 80 are distributed along the electrochromic display element. Vdrive 71 represents an electrically conductive element to which a drive signal is applied. In one embodiment, anode 70 is common to the entire electrochromic display element and Vdrive 71 represents the individual electrodes that make up one pixel or segment in the display. Vdrive 71 can be modeled as having distributed drive track resistors 112, 114, 116, 118, 120 and 122.

  The display element shown in FIG. 6 includes a peripheral part 60 and a central part 61. When the display element is realized as an electrochromic element, the peripheral part 60 and the central part 61 are charged differently. Thus, the electrochromic display element has a spatially changing parameter and a temporally changing property. The spatial change can be modeled as a plurality of distributed variable capacitors and variable resistors appearing between the anode (ANODE) 70 and the Vdrive 71, and as shown in FIG. 7, the peripheral capacitor (C-EDGE) 81 And the peripheral resistor (R-EDGE) 100 are intermediate capacitors 83, 104, 106, 108 in series with the intermediate resistors 102, 104, 106, 108, respectively, with respect to the central capacitor (C-center) 91 and the central resistor (R-CENTER) 110. Shown with 85, 87, 89.

  An electrochromic display element operates more like a transmission line than a mass of resistance and capacitance. In addition to the properties of the transmission line, the fact that the impedance at different points in the electrochromic device varies depending on its charge state causes the electrochromic device to operate as a transmission line that changes with time. As a result, it may be difficult to obtain uniform charging and color development of the electrochromic device. Waveforms that change over time are used to obtain a uniform color by substantially putting waves into the electrochromic display element. The waveform matches the spatially and temporally varying impedance of the electrochromic device.

  The application of a constant waveform drive signal causes the segment to develop very quickly but not uniformly, so the use of a changing (and potentially matched) waveform as the drive signal is a constant waveform drive. It is preferable to the application of a signal. By changing the drive signal to the display element over time, the charge transfer is increased as compared with the case where a constant drive signal is used. In addition, changing the Vdrive waveform can prevent unsafe charging of the display element. In one embodiment, the waveform is changed to achieve charging and discharging of the electrochromic display element with a substantially constant current. In charging obtained using a constant voltage drive signal, the charging current is initially very large but decreases as the device is charged, but charging at a constant current allows more uniform color development of the electrochromic display device. To.

  Referring to FIG. 8, a sawtooth waveform can be used to obtain a substantially constant current drive signal for an electrochromic display element. A sawtooth signal that is positive, such as OFF 151 in FIG. 8, can be used to turn off the electrochromic display element, and a sawtooth signal that is negative, such as ON 153 in FIG. 8, turns on the electrochromic display element. Can be used to In one embodiment, the drive signal is changed from voltage V-safe 160 to a larger voltage, such as V-attack 162. In one embodiment, Vsafe 160 is equal to Vref1 having a value of about 500 mV. In this embodiment, V-attack 162 is equal to Vdrive-ON 154 having a value of about 1000 mV. A signal of the same magnitude but different polarity, such as OFF 151, can be used to turn off the electrochromic display element. In one embodiment, these signals are referenced to the level established by Virtual-GND 152. As shown in FIG. 8, rise time 163 and fall time 165 are associated with a sawtooth waveform.

  One advantage of using a sawtooth waveform is that the decreasing blade portion of the sawtooth waveform is used to draw the voltage at the periphery 60 at the display element, thereby providing a more uniform charge across the display element. Resulting in a more uniform color development. Another advantage of using the sawtooth waveform shown in FIG. 8 is that while the safe voltage for the electrochromic display element (in this case V-safe 160) is momentarily exceeded, the drive signal rises to V-attack 162. The next is to go back low. Due to the transmission line-like nature of the display element, even if ON153 is changed to Vdrive-ON162, the entire display element will not reach a voltage higher than the safe voltage; Proceed through the element to achieve uniform color development.

  In one embodiment, the voltage at the periphery 60 of the display element is detected to determine the state of charge of the display element. This allows the amount of charge on the display element to be monitored and ensures that the element is not compromised. Due to the nature of the display element's transmission line, the use of a changing waveform allows the charge to move efficiently along the display element, and the average of the overall electrochromic element when the periphery is monitored. Gives a voltage reading representing voltage and charge. By using a changing waveform, such as the sawtooth wave shown in FIG. 8, the charge proceeds to the central portion 61 of the display element, and a safe voltage can be measured at the peripheral portion 60. Even if what appears to be an “unsafe” voltage is applied to the display element, only the charge travels to the center of the display element and no unsafe long-term voltage is applied to the entire display element.

  FIG. 9 shows a block diagram of one embodiment of a driver system. In this driver system, the MCU 12 includes a plurality of digital-to-analog converters (DACs) 170, a voltage / constant current switching circuit 172, a waveform shaping circuit 174, a current control capacitor 182, a phase inversion circuit 180, a window comparator 176, (VIRTUAL_GROUND 152 Used with virtual ground generator 178 and multiple output channels 16. In one embodiment, the MCU 12 is used to control the DAC 170 to create the waveform used by the voltage constant current circuit 172 and the window comparator 176. Both outputs are used to drive the waveform shaping circuit 174. The waveform shaping circuit 174 forms a waveform together with the current control capacitor 182. This waveform is inverted by the phase inversion circuit 180, and the electrochromic display 181. Applied to the output channel 16 for application to.

  FIG. 10 illustrates one embodiment of the waveform shaping circuit 174. In this embodiment, a first current mirror transistor (Q6) 190 is used in conjunction with a second current mirror transistor (Q16) 192, which make a matched pair. The current-in load 191 is set using a preset resistor (not shown), and is mirrored on the collector of the current mirror transistor (Q6) 190. This creates a constant current that is used to charge the current control capacitor (C17) 182 through transistor (Q9) 199. When the voltage at the current control capacitor 182 reaches V-SAFE 160, the comparator (IC2A) 197 turns off the transistor (Q13) 200 and turns on the transistor (Q9) 199. The current control capacitor 182 is discharged to V-ATTACK 162. The current control capacitor 182 is discharged with a constant current. When the voltage at current control capacitor 182 discharges to V-ATTACK 162, IC2A 197 turns off transistor (Q13) 200, turns on transistor (Q9) 199, and the cycle repeats.

  The constant current applied to the current control capacitor 182 creates a linear voltage waveform (rise and fall) at the current control capacitor 182, and this signal is composed of IC 4 C 206, transistor (Q 7) 201, and transistor (Q 12) 202. Buffered by a push-pull transistor pair. The generated voltage VDRIVE-ON 154 drives the plurality of segments and is inverted by IC4D 203, so that transistor (Q5) 204 and transistor (Q5) 205 create VDRIVE-OFF 150, and VDRIVE-OFF 150 does not drive the segment. Used for.

  The waveform shaping circuit 174 is used to change the parameters of the rise time 163, the fall time 165, the V-SAFE 160, and the V-ATTACK 162. A sharp rise time is used to make the filling fill and color from the central portion 61 to the peripheral portion 60 more uniform.

  Using the driving waveform described here, it is possible to charge the display element with a constant current, thereby decreasing the voltage and making an error regarding the state of charge detected by the voltage sensor located at the peripheral portion 60. Avoid reading. In one embodiment, additional charge is output if the segment did not reach the correct voltage with the applied charge (from the applied waveform). When the segment reaches the correct voltage, the driver enters a high impedance state.

  In one embodiment, the system shown in FIG. 9 can be used to learn the electrochromic display 181 so that different sized segments can be driven by varying the amount of charge applied to each segment. Since there is a linear relationship between the voltage applied to the current mirror transistor and the area under the sawtooth voltage waveform, the sawtooth voltage waveform can be modulated segment by MCU 12.

The present invention is not limited to the embodiments described herein, and can be modified without departing from the invention described in the claims.

System diagram of the device and electrochromic display of the present invention connected to a micro control unit 1 is a block diagram of the apparatus of FIG. 1 according to the present invention. Timing diagram for the apparatus of FIG. 1 operating in program mode. Timing diagram of the apparatus of FIG. 1 operating in detect mode Figure against applied voltage time Figure of applied voltage against time including detection time Illustration of a multi-segment display with a segment with a perimeter and a center Model diagram for electrochromic display elements Diagram of drive signals for electrochromic display elements Block diagram for display element drivers Diagram of embodiment of waveform shaping circuit

Explanation of symbols

  10 segment driver, 10,12 drive unit, 14 multi-segment display, 18, 40, 42 signal path, 20,22 segment, 40, 42, 46, 44, 34 state of charge indicator.

Claims (44)

A driving device for driving a multi-cell display connected to each cell to be driven of the multi-cell display,
It consists of a cell driver that drives the cell according to the state of charge indicator for each cell, and a signal path that receives the characteristics of the selected cell and outputs the characteristics to the sensor,
Operates in program mode and detect mode,
In the program mode, the state of charge of the plurality of cells is set by the state of charge indicator,
In the detection mode, characteristics of a selected cell among the plurality of cells are received via the signal path, and one or more cells among the remaining cells are driven according to a charge state indicator for that cell. Drive device.   The drive device according to claim 1, wherein the drive device is connected to a controller that operates as the sensor.   3. The driving apparatus according to claim 2, wherein a signal indicating the characteristic of the selected cell is output to the controller in a detection mode.   4. The drive device according to claim 2, wherein a signal indicating a required charge state of one or more of the cells is received from the controller in a program mode.   5. The driving device according to claim 2, wherein the operation mode is determined by a logic signal received from the controller. 6.   6. The driving device according to claim 2, wherein when at least one of the one or more characteristics of the cell is determined to be within a reference range, the operation mode is changed from the detection mode to the program mode. A drive device characterized by that.   The driving apparatus according to claim 2, further comprising a shift register for storing information received from the controller.   8. The driving apparatus according to claim 7, wherein information is continuously input to the shift register in accordance with a clock signal.   9. The driving apparatus according to claim 8, wherein in the program mode, the information includes cell charge state information indicating a charge state of each of a plurality of cells for which a charge state is requested. The drive device characterized in that the information comprises an identifier of the selected cell.   2. The driving apparatus according to claim 1, wherein the state of charge is one of an off state, an on state, and a high impedance state.   11. The driving apparatus according to claim 10, wherein the ON state is one of a low speed charging state and a high speed charging state.   11. The driving apparatus according to claim 10, wherein the cell to be detected is set in a high impedance state in a detection mode.   13. A control system for a display comprising a drive device and a controller as claimed in any one of claims 1 to 12, wherein the controller is obtained from the characteristics of the cell or each cell. The control system characterized by storing timing information about.   14. The control system according to claim 13, wherein the controller is scheduled to switch the driving device to a detection mode based on the timing information.   14. The control system according to claim 13, wherein the controller periodically adjusts the timing information.   14. The control system according to claim 13, wherein the driving device is the driving device according to claim 3, wherein the controller is responsive to the signal received from the driving device. A control system characterized by adjusting.   14. The control system according to claim 13, wherein the controller changes timing information about a cell depending on a charge state of another cell.   18. The control system according to claim 17, wherein the controller is characterized by a coefficient factor determined by a ratio of an aggregate area of the cell to be turned on and an aggregate area of the cell to be turned off at a certain time. A control system characterized by changing timing. A driving method of a multi-cell display,
Connecting to each cell of the controlled multi-cell display;
Driving each cell with a state of charge indicator associated with the cell;
Receiving the characteristics of the selected cell;
The step of outputting the above characteristics to the sensor,
In the program mode, the charge state of the plurality of cells is set by the charge state indicator, and in the detection mode, the characteristic of the cell selected from the plurality of cells is a signal path. One or more of the remaining cells are set by the state of charge indicator associated with the cell,
Driving method. A driving method of a display element having an impedance that changes with time,
a) applying a drive signal to the display element;
b) A step and a driving method for changing the driving signal to the display element with time to substantially increase the charge movement to the display element over the charge movement that occurs using a constant driving signal.   21. The driving method according to claim 20, wherein changing the driving signal in time in step b prevents unsafe charging of the display element.   21. The driving method according to claim 20, wherein the temporal change of the driving signal in step b is achieved using a sawtooth signal waveform.   21. The driving method according to claim 20, wherein the time-varying of the driving signal in step b is performed using a negative portion of the sawtooth signal waveform to achieve charging of the display element. And how to.   21. The driving method according to claim 20, wherein the time-varying of the driving signal in step b is performed using the positive portion of the sawtooth signal waveform to achieve display element discharge. And how to. A method for driving an electrochromic display element having an impedance that changes with time,
a) applying a voltage to the electrochromic display element;
b) A driving method for achieving charging or discharging of the electrochromic display element with a substantially constant current by changing a voltage to the electrochromic display element. The driving method according to claim 25, comprising:
A driving method characterized in that the voltage to the electrochromic display element is changed in a sawtooth shape.   26. The driving method according to claim 25, wherein in step b of changing the voltage, charging of the display element is achieved using a negative portion of the sawtooth signal waveform.   26. The driving method according to claim 25, wherein in step b of changing the voltage, discharging of the display element is achieved using a positive portion of the sawtooth signal waveform. A method for charging an electrochromic display element comprising a peripheral area and a central area,
a) applying a drive signal to the electrochromic display element;
b) Changing the drive signal to the electrochromic display element to make the color development uniformity between the peripheral area and the central area higher than the uniformity obtained using a constant drive signal .   30. The charging method according to claim 29, wherein the drive signal is a voltage drive signal.   30. The charging method according to claim 29, wherein the drive signal is a current drive signal. The charging method according to claim 29, further comprising:
c) A charging method characterized by detecting whether the charging level is sufficient by detecting a charging level in the peripheral area. The charging method according to claim 29, further comprising:
d) A charging method comprising detecting a charge level in the peripheral area and determining whether or not a safe charge level has been exceeded. A driving method of a display element,
a) applying a driving signal to the display element to charge the display element;
b) detecting the display element to determine a charge level of the display element;
c) determining whether the charge level of the display element exceeds a predetermined charge range;
d) A driving method for changing the driving signal when the charging level of the display element exceeds the charging range.   35. A driving method as claimed in claim 34, wherein the determination in step c is achieved using voltage monitoring of the display element.   35. The driving method according to claim 34, wherein the change of the drive signal in step d is achieved by changing the voltage of the drive signal.   35. The driving method according to claim 34, wherein the change of the drive signal in step d is achieved by changing the timing of the drive signal.   38. The driving method according to claim 37, wherein the timing varies depending on a charging speed of the display element. A driving method of a display element having a peripheral area and a central area,
a) applying a drive signal to the display element;
b) changing the drive signal to remove part of the charge from the peripheral area,
c) A driving method for detecting a charge in the peripheral area to obtain a measure of the total charge in the display element.   40. The driving method according to claim 39, wherein the driving signal is a voltage signal.   41. The driving method according to claim 40, wherein the change of the driving signal in step b is achieved using a voltage level lower than the charging threshold. A driver for a display element having an impedance that varies with time,
a) a control circuit that generates a control voltage that substantially matches the impedance of the display element that varies with time;
b) A driver comprising a variable voltage driving circuit including a waveform generator controlled by the control voltage.   43. The driver of claim 42, wherein the control circuit generates a control voltage that produces a substantially constant current signal to the display element. A driver for an electrochromic display element,
a) a driver circuit that creates a waveform that varies with time for application to the electrochromic display element;
b) a sensing element for measuring the voltage at the electrochromic display element;
c) A driver comprising a control circuit that controls the driver circuit with the voltage measured by the electrochromic display element.

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