JP6028895B2 - Voltage generation circuit, display device having voltage generation circuit, and voltage generation method - Google Patents

Description

  The present invention relates to a voltage generation circuit used for an electronic device or an electric device, a display device including the voltage generation circuit, and a voltage generation method.

  2. Description of the Related Art Conventionally, there are cases where electronic devices or electrical devices have a plurality of circuits, motors, and the like that require different voltages inside the device. Such devices include a type that directly supplies a plurality of voltages from the outside and a type that generates a plurality of voltages inside the device by supplying a single voltage from the outside.

  Some of these devices require high-accuracy voltage values for a plurality of voltages in order to cause the devices to perform accurate operations. For example, a display device such as a liquid crystal display or an organic EL needs to supply an accurate display voltage corresponding to the gradation value to a liquid crystal display panel or an organic EL display panel in order to accurately express the gradation of an image. In order to generate the display voltage, a plurality of accurate voltages are required. Such an accurate plurality of voltages may be referred to as a reference voltage. Although the number of reference voltages varies depending on the display device, it is several to several hundreds, and some devices may require the same number of display gradations.

  As described above, an accurate voltage value is required for the reference voltage. In Patent Document 1, in order to reduce power consumption in a liquid crystal display device, a reference voltage generator is provided with a reference voltage without a means for adjusting a potential difference between a pixel electrode and a common electrode, which is included in a signal generator for a common electrode. It is described that it has a function of shifting. The reference voltage is input to a source driver circuit that outputs a source signal to the liquid crystal panel.

JP 2002-108312 A

  However, in the reference voltage generation unit in Patent Document 1, the amount of current in the source driver circuit changes abruptly because the voltage shift of the plurality of reference voltages is performed at the same timing. For this reason, it is assumed that the levels of the plurality of source signals output from the source driver circuit change suddenly, although they are caused by the potential difference that shifts in each reference voltage. In a normal case, there are a plurality of source signals whose output voltage is a voltage value indicated by one reference voltage. For this reason, the change in the source signal accompanying this sudden change in the reference voltage results in an increase in the amount of current flowing through the source driver circuit. This phenomenon may increase the load of the power supply unit that supplies power to the source driver circuit, leading to a decrease in power supply voltage. A drop in power supply voltage can cause malfunctions in various parts of the overall device.

  Further, when the same power supply unit as that of the source driver circuit is used for the reference voltage generation unit, a state in which an accurate reference voltage cannot be maintained is caused. For example, this may cause a state in which the upper and lower relations of the voltage values of a plurality of reference voltages are reversed. Depending on the configuration of the source driver circuit, a state similar to latch-up occurs, which causes a large amount of flow. It is conceivable that the elements constituting the source driver circuit are destroyed by the current.

  The problem described above can be solved if the device has a power supply unit that can withstand a sudden change in current and can supply a stable voltage, but for this purpose, a power supply unit with a larger capacity that can cover the assumption. Therefore, there is a high possibility that the size is large and the cost is high for use in a display device.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following embodiments or application examples.

[Application Example 1]
The voltage generation circuit according to this application example is a voltage generation circuit that outputs a plurality of voltages, a first voltage generation unit that generates a first output voltage, and a first voltage that is lower than the first output voltage. A second voltage generator that generates two output voltages, wherein the output of the first output voltage is controlled to become a first reference voltage value while increasing the voltage value stepwise, and the second output voltage The output of the second output voltage is controlled to become the second reference voltage value while gradually increasing the voltage value, the start of the output of the second output voltage is performed after the start of the output of the first output voltage, The time when the first output voltage becomes the first reference voltage value and the time when the second output voltage becomes the second reference voltage value are substantially the same time.

  According to this configuration, in the voltage generation circuit, the first output voltage that is the output of the first voltage generation unit is controlled to be the first reference voltage value while gradually increasing the voltage, and the second voltage generation unit The output is controlled so that the second output voltage becomes the second reference voltage value while increasing the voltage stepwise, the second output voltage is lower than the first output voltage, and the start of the output of the second output voltage is the first. The first output voltage is performed after the start of the output of the one output voltage, and the second output voltage becomes the second reference voltage value when the first output voltage becomes the first reference voltage value. A sudden change in the current flowing from the power supply unit to the circuit to which the second output voltage is input can be suppressed.

[Application Example 2]
In the voltage generation circuit according to the application example, the first output voltage is increased stepwise by a first voltage value, and the second output voltage is increased stepwise by a second voltage value. The value and the second voltage value are preferably substantially the same.

  According to this configuration, the first output voltage is increased stepwise by the first voltage value, the second output voltage is increased stepwise by the second voltage value, and the first voltage value and the second voltage value are substantially reduced. By being the same, the circuit configuration in the voltage generation circuit can be a circuit configuration having little influence on the change in the amount of current.

[Application Example 3]
The voltage generation circuit according to the application example further includes a third voltage generation unit that generates a third output voltage that is lower than the second output voltage, and the output of the third output voltage is The third reference voltage value is controlled to be increased by three voltage values stepwise, and the output of the third output voltage is started after the start of the output of the second output voltage. The time when the output voltage becomes the second reference voltage value and the time when the third output voltage becomes the third reference voltage value are substantially the same time, and the second voltage value and the third voltage value are the same. The voltage value is preferably substantially the same.

  According to this configuration, the third voltage generator is further provided, and the third output voltage lower than the second output voltage generated by the third voltage generator is increased stepwise by the third voltage value. The output of the third output voltage is controlled to be the reference voltage value, the start of the output of the third output voltage is later than the start of the output of the second output voltage, and the second output voltage is the third output voltage becomes the third reference voltage value It is substantially the same time as the second reference voltage value, and the third voltage value is substantially the same voltage value as the second voltage value, so that the circuit to which the third output voltage is input flows from the power supply unit. A rapid change in the amount of current can be suppressed, and the circuit configuration in the voltage generation circuit can be a circuit configuration that has little influence on the change in the amount of current.

[Application Example 4]
In the voltage generation circuit according to the application example described above, the timing of the stepwise change in the first output voltage is substantially the same as the timing of the stepwise change in the second output voltage. The stepwise change timing and the stepwise change timing in the third output voltage are preferably substantially the same timing.

  According to this configuration, the change timing of the first output voltage and the change timing of the second output voltage are substantially the same timing, and the change timing of the second output voltage and the change timing of the third output voltage are the same. Since the timing is substantially the same, it is not necessary to configure a circuit for controlling the timing of voltage change in the voltage generation circuit for each output voltage, and the first output voltage is made higher than the second output voltage. The period during which the second output voltage is lower than the period during which the second output voltage is lower than the third output voltage can be eliminated.

[Application Example 5]
A display device having a voltage generation circuit according to this application example includes a display unit that requires a plurality of reference voltages and a voltage generation circuit that generates the plurality of voltages, and the voltage generation circuit has a first output. A first voltage generation unit that generates a voltage; and a second voltage generation unit that generates a second output voltage that is lower than the first output voltage. The output of the first output voltage is stepwise The output of the second output voltage is controlled to become the second reference voltage value while gradually increasing the voltage value, while increasing the voltage value to the second reference voltage value. The output of the output voltage is started after the start of the output of the first output voltage, and the time when the first output voltage becomes the first reference voltage value and the second output voltage are the second The time when the reference voltage value is reached is substantially the same time, One output voltage increases stepwise by a first voltage value, and the second output voltage increases stepwise by a second voltage value, and the first voltage value and the second voltage value are substantially the same. It is characterized by being.

  According to this configuration, the display device includes a display unit that requires a plurality of reference voltages and a voltage generation circuit that generates a plurality of voltages, and the voltage generation circuit generates a first output voltage. And a second voltage generator that generates a second output voltage that is lower than the first output voltage, so that the output of the first output voltage becomes the first reference voltage value while gradually increasing the voltage value. The output of the second output voltage is controlled to be the second reference voltage value while gradually increasing the voltage value, and the start of the output of the second output voltage is greater than the start of the output of the first output voltage. The time when the first output voltage becomes the first reference voltage value and the time when the second output voltage becomes the second reference voltage value are substantially the same time, and the first output voltage is The voltage is increased stepwise by one voltage value, and the second output voltage is stepped by the second voltage value. Since the first voltage value and the second voltage value are substantially the same, a rapid change in the amount of current accompanying a change in each of the first output voltage and the second output voltage in the display device is suppressed. I can do things.

[Application Example 6]
In the display device having the voltage generation circuit according to the application example, the voltage generation circuit further includes a third voltage generation unit that generates a third output voltage that is lower than the second output voltage, The output of the third output voltage is controlled to be the third reference voltage value while gradually increasing the third voltage value, and the start of the output of the third output voltage is the output of the second output voltage. The time when the second output voltage becomes the second reference voltage value and the time when the third output voltage becomes the third reference voltage value are substantially the same time after the start. The second voltage value and the third voltage value are preferably substantially the same.

  According to this configuration, the third voltage generator is further provided, and the third output voltage lower than the second output voltage generated by the third voltage generator is increased stepwise by the third voltage value. The output of the third output voltage is controlled to be the reference voltage value, the start of the output of the third output voltage is later than the start of the output of the second output voltage, and the second output voltage is the third output voltage becomes the third reference voltage value The current that flows from the power supply unit to the circuit to which the third output voltage is input when the second reference voltage is substantially the same time and the third voltage value is substantially the same as the second voltage value. A rapid change in the amount can be suppressed, and the current amount in the voltage generation circuit can be easily controlled.

[Application Example 7]
The voltage generation method according to this application example is a voltage generation method for outputting a plurality of voltages, a first voltage generation step for generating a first output voltage, and a voltage lower than the first output voltage. A second voltage generating step for generating two output voltages, wherein in the first voltage generating step, the output of the first output voltage becomes a first reference voltage value while increasing the first voltage value stepwise. In the second voltage generation step, the output of the second output voltage is controlled so as to become the second reference voltage value while increasing the second voltage value stepwise, and the second voltage generation step is started. Is after the first voltage generation step is started, and in the first voltage generation step and the second voltage generation step, the time when the first output voltage becomes the first reference voltage value and the The second output voltage is equal to the second reference voltage value. And time Rutoki is controlled to be substantially the same time, characterized in that said first voltage value and the second voltage value is substantially the same.

  According to this method, the first voltage generation step includes a first voltage generation step of generating a first output voltage and a second voltage generation step of generating a second output voltage that is a voltage lower than the first output voltage. The output of the first output voltage is controlled to become the first reference voltage value while increasing the voltage value stepwise, and the output of the second output voltage is increased while increasing the voltage value stepwise in the second voltage generation step. The second voltage generation step is started after the first voltage generation step is started, and the time when the first output voltage becomes the first reference voltage value and the second reference voltage value are controlled. Control is performed in the first voltage generation step and the second voltage generation step so that the time when the output voltage becomes the second reference voltage value is substantially the same time, and the first voltage value and the second voltage value are Are substantially the same, each of the first output voltage and the second output voltage. It can be controlled to suppress an abrupt change in the current amount due to the change in voltage.

[Application Example 8]
The voltage generation method according to the application example further includes a third voltage generation step of generating a third output voltage that is lower than the second output voltage, and in the third voltage generation step, The output of the three output voltages is controlled to be the third reference voltage value while gradually increasing the third voltage value, and the start of the third voltage generation step is after the second voltage generation step is started. Yes, in the second voltage generation step and the third voltage generation step, a time when the second output voltage becomes the second reference voltage value and a time when the third output voltage becomes the third reference voltage value Preferably, the second voltage value and the third voltage value are substantially the same, and are controlled so as to be substantially the same time.

  The method further includes a third voltage generation step of generating a third output voltage that is a voltage lower than the second output voltage, and the output of the third output voltage is stepwise in the third voltage generation step. The third voltage generation step is started after the second voltage generation step is started, and the third voltage generation step is started after the second voltage generation step and the third voltage generation step. In the voltage generation step, the time when the second output voltage becomes the second reference voltage value and the time when the third output voltage becomes the third reference voltage value are controlled to be substantially the same time, and the second By controlling the voltage value and the third voltage value to be substantially the same, it is possible to suppress a sudden change in the amount of current flowing from the power supply unit to the circuit to which the third output voltage is input and to generate a voltage. This makes it easy to control the amount of current in the circuit. .

The schematic block diagram of a voltage generation circuit. The schematic block diagram of a 1st voltage generation part. The flowchart of the process in a voltage generation circuit. 1 is a schematic block diagram of a display device having a voltage generation circuit. The graph which shows the output voltage of a voltage generation circuit. The schematic block diagram of a voltage generation circuit. The schematic block diagram of the voltage generation part in a voltage generation circuit. The graph which shows the output voltage of the conventional voltage generation circuit. The graph which shows the output voltage of a voltage generation circuit.

  Embodiments of the present invention will be described with reference to the drawings. The drawings used for explanation are for convenience showing at least the portions necessary for explanation. Further, configurations in the following embodiments including this embodiment do not limit the implementation of the present invention. In the following description of the embodiments, the word “on” or “off” is used. However, depending on the signal, after being turned on or off, unless the signal is turned off or turned on, the on state or the off state is maintained. Some of them are turned on only for a predetermined period from the off state. Since these can be discriminated by the function of the signal, in the description, ON or OFF is used without mentioning this difference.

(First embodiment)
FIG. 1 shows a voltage generation circuit 100 to which the present invention is applied. The voltage generation circuit 100 includes an external interface 110 (hereinafter referred to as an external IF 110), a control unit 120, an oscillator 130, and n voltage generation units. In addition, a power supply signal 102 is connected to the voltage generation circuit 100 in order to supply power necessary for operation. In FIG. 1, illustration of GND connection is omitted. The voltage generation circuit 100 is a circuit that generates and outputs n reference voltages by n voltage generation units. In FIG. 1, the first voltage generation unit 140, the second voltage generation unit 150, the third voltage generation unit 160, and the nth voltage generation unit 170 among the n voltage generation units are illustrated.

  The voltage generation circuit 100 is controlled by a host device (not shown). The external signal 101 connects the host device. The type of the external signal 101 is not particularly limited. It may be adapted to the specifications of a connectable host device. For example, the external signal 101 may be an I2C bus, SPI, or USB. It is the role of the external IF 110 to exchange signals with the external signal 101 and to transmit commands from the host device and transmit / receive data to / from the voltage generation circuit 100.

  The control unit 120 is a part that controls the inside of the voltage generation circuit 100 and executes a command transmitted from the external IF 110. In response to an instruction from the control unit 120 according to the command, for example, a reference voltage value is set for each of the n voltage generation units via the internal control signal 121. Here, the reference voltage value is a voltage that is finally output by the voltage generation circuit 100. In addition, the control unit 120 performs control of time until the outputs of the n voltage generation units reach the reference voltage value, control of unit voltage that is increased in stages, and the like. If there is an abnormality in the voltage generation circuit 100, the information is held as a status, and is provided to the host device via the external IF 110 in accordance with the status read command of the host device. The internal control signal 121 is a signal composed of a plurality of signals as will be described later.

  The oscillator 130 is a part that provides a clock necessary for the operation to each of the external IF 110, the control unit 120, and the n voltage generation units. The clock frequency is a predetermined frequency set in advance after the power is turned on, but thereafter, the control unit 120 sets a clock frequency suitable for the operation.

  The first voltage generator 140 is a part that generates the first reference voltage 141. Similarly, the second voltage generator 150 is a part that generates the second reference voltage 151, and the third voltage generator 160 is a part that generates the third reference voltage 161. And then. The nth voltage generator 170 is a part that generates the nth reference voltage 171.

  In the present embodiment, the first reference voltage 141 has the highest voltage value among the n reference voltages. The second reference voltage 151 has the next highest voltage value after the first reference voltage value, and the nth reference voltage 171 has the lowest voltage value among the n reference voltages. When an arbitrary reference voltage from the second reference voltage to the (n−1) th reference voltage is the mth reference voltage, the voltage difference between the m−1th reference voltage and the mth reference voltage is the mth reference voltage. It is almost equal to the voltage difference with the (m + 1) th reference voltage. This voltage difference is called a unit voltage.

  FIG. 2 shows a schematic block diagram of the first voltage generator 140. Although not shown, the configuration of the other voltage generation units is the same as that of the first voltage generation unit 140. The first voltage generation unit 140 includes a first register 145, a second register 144, a digital-analog converter 143 (hereinafter referred to as a DAC 143), and an output amplifier 142. The data signal 122, the write instruction signal 123, and the write instruction signal 124 are all signals output from the control unit 120 and are included in the internal control signal 121. In the following description, the description of the second voltage generation unit 150 to the nth voltage generation unit 170 will also be performed using the component numbering shown in FIG.

  The DAC 143 converts the digital signal 126 output from the second register 144 into an analog signal 127 and outputs the analog signal 127 to the output amplifier 142. The analog signal 127 is a signal having a level corresponding to the value of the digital signal 126. The analog signal 127 is output as the first reference voltage 141 by the output amplifier 142. The output amplifier 142 may be a so-called operational amplifier, and the analog signal 127 and the first reference voltage 141 have a voltage follower relationship.

  The first register 145 is a register in which a set value transmitted by the data signal 122 is written according to an instruction of the write instruction signal 123. The second register 144 is a register in which the output of the first register 145 is written according to the instruction of the write instruction signal 124. As described above, the data signal 122, the write instruction signal 123, and the write instruction signal 124 are all signals output from the control unit 120. The set value written to the first register 145 by the instruction of the write instruction signal 123 is written to the second register 144 by the instruction of the write instruction signal 124.

  The digital signal 126 output from the second register 144 is converted into an analog signal 127 by the DAC 143 and output as the first reference voltage 141 via the output amplifier 142. However, the update timing of the value of the second register 144 is instructed to be written. By controlling with the signal 124, the switching timing of the first reference voltage can be controlled by the control unit 120. As described above, each of the n voltage generators has the same configuration. The data signal 122 is connected to a common signal line, but the write instruction signal 123 and the write instruction signal 124 are transmitted through independent signal lines in each voltage generation unit. As a result, the control unit 120 can individually write different setting values to the first register 145 of each voltage generation unit, and the update of the second register 144 in all the voltage generation units is substantially the same. Can be done at the timing. As a result, all the reference voltages are changed at substantially the same timing. The control unit 120 sets a value corresponding to the voltage to be output to the first register 145 of each voltage generation unit, and repeatedly writes this value to the second register 144, so that the output from all the voltage generation units is output. The target reference voltage value can be set.

  Next, a control method will be described using a flowchart. FIG. 3A shows a control flowchart F100 in the voltage generation circuit 100. FIG.

  First, when the apparatus having the voltage generation circuit 100 is turned on, initial setting (processing S101) is performed. The initial setting (process S101) includes a process for setting a control mode and the like by a power-on reset performed when the apparatus is turned on and an initial setting routine executed thereafter.

  Although the flowchart of the initialization routine is not particularly shown, the execution of the initialization routine may be performed by the control unit 120. The control unit 120 sets the external IF 110 in a state in which communication with the host device is possible, and the setting of the frequency of the operation clock 131 used in the first voltage generation unit 140 to the nth voltage generation unit 170 is performed.

  The initial value of the second register 144 in all voltage generation units is set by a power-on reset so that the voltage output as the reference voltage becomes 0 V (volt). When the frequency of the operation clock 131 is set by the initial setting routine and the first voltage generation unit 140 to the nth voltage generation unit 170 can be operated, according to the value of the second register 144, the first reference voltage 141 to the nth The output of the reference voltage 171 becomes 0V (volt).

  Next, the reference voltage is set with respect to the first reference voltage 141 to the nth reference voltage 171 (processing S102 to processing S104). The first reference voltage 141 to the nth reference voltage 171 are increased stepwise by a predetermined unit voltage, and finally set to the prescribed reference voltages that are intended for each. It is determined in step S104 whether or not all the reference voltage outputs have reached the specified reference voltage (reference voltage value). If it is determined that all the reference voltage outputs have reached the reference voltage value, The reference voltage setting process ends.

  The setting of the reference voltage with respect to the first reference voltage 141 to the n-th reference voltage 171 by the processes S102 to S104 is performed as follows.

  First, the control unit 120 outputs the set value “K” corresponding to the unit voltage “P” to the data signal 122, and the first register in the first voltage generation unit 140 by the write instruction signal 123 to the first voltage generation unit 140. The writing to 145 is instructed (processing S102). As a result, the set value “K” is written and held in the first register 145 in the first voltage generator 140. For “P”, description of units such as V (volt) is omitted.

  Next, when writing to the second register 144 in the first voltage generation unit 140 is instructed by the write instruction signal 124, the set value “K” held in the first register 145 becomes the second register 144 in the first voltage generation unit 140. Is written to. As a result, the value of the digital signal 126 that is the input signal of the DAC 143 becomes the set value “K”, and the analog signal 127 of the DAC 143 changes. In accordance with the analog signal 127, the voltage value of the first reference voltage, which is the output of the output amplifier 142, becomes “P” (processing S103). In this state, the output voltages of the second reference voltage 151 to the n-th reference voltage 171 remain 0 V (volts). Accordingly, since all the reference voltages are not set, it is not determined that the process is finished, and the process proceeds to process S102 (process S104).

  Next, the control unit 120 outputs a set value “2 × K” corresponding to “2 × P”, which is twice the unit voltage, to the data signal 122, and the write instruction signal 123 for the first voltage generation unit 140 generates the first value. The 1 voltage generator 140 is instructed to write to the first register 145. Subsequently, the control unit 120 outputs a set value “K” corresponding to the unit voltage “P” to the data signal 122, and a first instruction in the second voltage generation unit 150 by the write instruction signal 123 to the second voltage generation unit 150. Instructs writing to the register 145. Accordingly, the set value “2 × K” is written and held in the first register 145 in the first voltage generation unit 140, and the set value “K” is written and held in the first register 145 in the second voltage generation unit 150. (Process S102).

  Next, the value held in each first register 145 is written to each second register 144 by the write instruction signal 124 for each of the first voltage generation unit 140 and the second voltage generation unit 150. As a result, the output of the output amplifier 142 in the first voltage generator 140 becomes “2 × P”, and the output of the output amplifier 142 in the second voltage generator 150 becomes “P” (processing S103). In this state, the output voltages of the third reference voltage 161 to the nth reference voltage 171 remain 0 V (volts). Accordingly, since all the reference voltages are not set, it is not determined that the process is finished, and the process proceeds to process S102 (process S104).

  In the next process S102, the setting value “3 × K” is written to the first register 145 in the first voltage generation unit 140, and the setting value “2 × K” is written to the first register 145 in the second voltage generation unit 150. Then, the set value “K” is written to the first register 145 in the third voltage generator 160. In the next process S103, the values of the first registers 145 of the first voltage generator 140, the second voltage generator 150, and the third voltage generator 160 are written into the second registers 144, respectively. The output voltage of the reference voltage 141 changes to “3 × P”, the output voltage of the second reference voltage 151 changes to “2 × P”, and the output voltage of the third reference voltage 161 changes to “P”.

  The control as described above is repeated by the control unit 120, and when it is determined in step S104 that the outputs of all the voltage generation units have reached the reference voltage value, the reference voltage setting process ends.

  The present embodiment is an example of an electronic device using the voltage generation circuit 100. FIG. 4 shows a schematic block diagram of the display device 10. The display device 10 includes a voltage generation circuit 100, a pixel signal driver circuit 200, and a display panel 300. In the display device 10, the voltage generation circuit 100 and the pixel signal driver circuit 200 are supplied with power by a power supply signal 102 connected to a power supply unit (not shown). Although not specifically shown, the power signal 102 may be used as a power source for other parts in the display device 10. It is assumed that the reference voltage in the display device 10 is eight types (n = 8).

  The display panel 300 may be a liquid crystal panel, for example. The pixel signal driver circuit 200 outputs a plurality of pixel data signals 201 and a timing signal 202 for instructing the timing for capturing the pixel data signals 201 to the display panel 300. The pixel data signal 201 is a signal indicating the display gradation of the pixel by the difference in voltage. In order to display a correct image on the display panel 300, it is necessary to maintain an accurate gradation level in the pixel data signal 201. The reference voltages of the first reference voltage 141 to the eighth reference voltage 171 output from the voltage generation circuit 100 are used as reference voltages for generating an accurate gradation level in the pixel signal driver circuit 200.

  When the reference voltage increases, the gradation level voltage of the pixel data signal 201 output from the pixel signal driver circuit 200 increases accordingly. The number of pixel data signals 201 is a number corresponding to the number of pixels in one display line of the display panel 300, and is generally several hundred to several thousand. When the gradation level voltage of the pixel data signal 201 rises, a current corresponding to the voltage flows from the power supply signal 102 to the pixel signal driver circuit 200, resulting in an increase in power consumption. After this is done, power consumption decreases. FIG. 5 shows a graph in which changes in the outputs of the eight reference voltages of the first reference voltage 141 to the eighth reference voltage 171 in the reference voltage setting period are associated with changes in power consumption corresponding thereto. In the display device 10, since the output start of each reference voltage is at a different timing and the change in the output of each reference voltage is stepwise, the difference in which the power required for charging also changes stepwise. It becomes the amount of.

  FIG. 8 shows the change in the output of the eight reference voltages and the change in the power consumption with respect to this when the output of the eight reference voltages is simultaneously started and changed to the specified reference voltage (conventional case). An example of a graph in which The maximum power consumption in FIG. 8 is larger than the maximum power consumption in FIG. By applying the present invention, it is possible to suppress a rapid change in power consumption until the reference voltage reaches a specified reference voltage. In order to maintain a stable voltage in the apparatus, a power supply unit with a larger amount of power supply is required in the case shown in FIG. 8 than in the case shown in FIG. As will be understood, by applying the present invention, it is possible to maintain a stable voltage even when a power supply unit smaller than the conventional one is used.

(Second Embodiment)
FIG. 6 shows a voltage generation circuit 400 to which the present invention is applied. The voltage generation circuit 400 outputs eight reference voltages of the first reference voltage 411 to the eighth reference voltage 418. In the present embodiment, the same components or the same functions as those in the first embodiment are denoted by the same reference numerals, and the description thereof may be omitted.

  As shown in FIG. 6, the voltage generation circuit 400 includes an external IF 110, a control unit 120, an oscillator 130, and a reference voltage generation unit 410. In addition, the power supply signal 102 is connected to the voltage generation circuit 400. still. As in FIG. 1, the GND connection is not shown.

  FIG. 7 shows a schematic block diagram of the reference voltage generation unit 410. The reference voltage generation unit 410 includes eight output amplifiers 421 to 428, a voltage dividing unit 420, and a voltage change control unit 430. FIG. 7 shows a part of a portion related to the first reference voltage 411, the second reference voltage 412, the seventh reference voltage 417, and the eighth reference voltage 418. The output amplifiers 421 to 428 have the same function as the output amplifier 142 in the first embodiment.

  The voltage divider 420 includes a resistor r1, a resistor r2, seven resistors r3 connected between the resistors r1 and r2, and a plurality of switches. The plurality of switches are switches for selecting input signals to the output amplifiers 421 to 428. The plurality of switches are controlled by signals output from a voltage change control unit 430 described later.

  As shown in FIG. 7, the resistor r1 is a resistor connected to the power signal 102 side, and the resistor r2 is a resistor connected to the GND side. Here, the resistance value of the resistor r2 is equal to the resistance value of the resistor r3. Specific resistance values of the resistors r1, r2, and r3 are not particularly mentioned, but appropriate resistance values are set based on the output reference voltage and the voltage of the power supply signal 102. In FIG. 7, the voltage at the node d8 is “8 × P”, the voltage at the node d7 is “7 × P”, and the voltage at the node d6 is “6 × P”. The voltage at the node d1 is “P”.

  In the present embodiment, the reference voltage output as the first reference voltage 411 is the highest reference voltage and the reference voltage output as the eighth reference voltage 418 is the lowest reference voltage, as in the first embodiment. In addition, the respective reference voltages increase step by step by unit voltage, and reach the prescribed reference voltage at substantially the same timing. The stepwise voltage output start at the first reference voltage 411 is performed at the earliest time, and the stepwise voltage output start at the eighth reference voltage 418 is performed at the latest time.

  The output of the first reference voltage 411 is the GND level and any voltage of the nodes d1 to d8, and the output of the eighth reference voltage 418 is the GND level and any voltage of the node d1. The switching of the output voltage is 8 times for the first reference voltage 411, decreases once from the second reference voltage 412 toward the eighth reference voltage 418, and for the eighth reference voltage 418. Once. Therefore, the number of switches for changing the output of the first reference voltage 411 by adding the switches for the GND connection is nine, and the number of switches for changing the output of the eighth reference voltage 418 is two. It is. The block diagram of the voltage divider 420 in FIG. 7 shows this state.

  The voltage change control unit 430 is a part that generates switch control signals for selecting the inputs to the output amplifiers 421 to 428 and for controlling the plurality of switches described above. The switch control signal is generated for each reference voltage. 7 includes a voltage output control unit 510 that generates switch control signals 511 to 519 for the first reference voltage 411, a voltage output control unit 520 that generates switch control signals 522 to 529 for the second reference voltage 412, and a seventh reference. A voltage output control unit 570 that generates switch control signals 577 to 579 for the voltage 417 and a voltage output control unit 580 that generates switch control signals 588 and 589 for the eighth reference voltage 418 are shown. The control part for the third to sixth reference voltages not shown has a similar structure to that shown.

  Next, the operation of the voltage generation circuit 400 will be described using a flowchart.

  FIG. 3B illustrates a control flowchart F200 in the voltage generation circuit 400. First, when the apparatus having the voltage generation circuit 400 is turned on, initial setting (processing S201) is performed. The initial setting (process S201) includes a process of setting a control mode and the like by a power-on reset performed when the apparatus is turned on and an initial setting routine executed thereafter. Each of the voltage output control units 510 to 580 has a voltage output permission flag therein. The voltage output permission flag is set to off (output not permitted) in the initial setting (process S201). When the voltage output permission flag is off, the switch control signal is controlled so that the GND level is fixedly selected for the inputs to the output amplifiers 421 to 428. Specifically, the switch control signal 519, the switch control signal 529, the switch control signal 579, and the switch control signal 589 shown in FIG. 7 are turned on. Thereby, as described above, at the end of the initial setting, the outputs of the first reference voltage 411 to the eighth reference voltage 418 are 0 V (volts).

  Next, setting of operating conditions for the voltage output control units 510 to 580 is performed by the control unit 120 (processing S202). The operating conditions to be set are a time interval (first condition) for changing the output voltage of the first reference voltage 411 to the eighth reference voltage 418 and permission of the output reference voltage (second requirement (second condition)). is there.

  The first condition may be defined by the count number of the clock output from the oscillator 130. The count number is set by the control unit 120 in a count counter (not shown) in the voltage generation circuit 400 via the internal control signal 121. The count counter continuously counts when it starts counting, and turns on the setting instruction signal 501 each time the defined count number is counted. The setting instruction signal 501 is input to the voltage output control unit 510 and used for switching timing control of the switch control signals 511 to 519.

  The setting instruction signal 502 is a signal used for switching timing control of the switch control signals 522 to 529, and the voltage output control unit 510 turns on the setting instruction signal 501 generated after the setting instruction signal 501 is turned on once. It is a signal to be transmitted. The setting instruction signal 503 is a signal to which the setting instruction signal 502 is similarly transmitted by the voltage output control unit 520. Similarly, the ON state of the setting instruction signal 501 is sequentially transmitted to the setting instruction signal 507 and the setting instruction signal 508.

  The setting of the second condition is performed by turning on an output permission flag existing in each of the voltage output control units 510 to 580. The process of turning on the output permission flag is performed by the control unit 120 via the internal control signal 121. When the output permission flag is ON, the output of the switch control signal is changed at the ON timing of the setting instruction signals 501 to 508 described above. Even when the output permission flag is off, the setting instruction signal is transmitted.

  Next, a reference voltage setting start instruction is issued from the control unit 120 via the internal control signal 121 (processing S203). In response to the instruction to start the reference voltage setting, the counting counter starts counting. By instructing the start of reference voltage setting, the reference voltage setting process in the control unit 120 ends.

  Next, an operation after an instruction to start setting the reference voltage when the output permission flag is set to ON in all of the voltage output control units 510 to 580 will be described.

  In response to the instruction to start setting the reference voltage, the count counter (not shown) in the voltage generation circuit 400 starts counting the first condition, and the setting instruction signal 501 output from the count counter is turned on each time the count is incremented. When the setting instruction signal 501 is turned on, the voltage output control unit 510 controls the switch control signals 511 to 519 so that the switch control signal 519 is turned off and the switch control signal 518 is turned on. As a result, the output voltage of the first reference voltage becomes “P” (FIG. 5- (a)).

  The count of the first condition by the count counter is continued, and when the count is counted up, the setting instruction signal 501 is turned on again. As a result, the voltage output control unit 510 controls the switch control signals 511 to 519, the switch control signal 518 is turned off and the switch control signal 517 is turned on. As a result, the output voltage of the first reference voltage becomes “2 × P” (FIG. 5B). Further, the setting instruction signal 502 is turned on, and the voltage output control unit 520 controls the switch control signals 522 to 529. The switch control signal 529 is turned off and the switch control signal 528 is turned on. As a result, the output voltage of the second reference voltage becomes “P” (FIG. 5B).

  As described above, when the setting instruction signal 501 to the setting instruction signal 508 are turned on based on the count-up of the count counter, the switch control signal is controlled, and the first reference voltage 411 to the eighth reference voltage 418 are When the unit voltage “P” increases by the time interval designated as the first condition and reaches the voltage defined as the object, the counting by the counting counter is ended. The state of change of the first reference voltage 411 to the eighth reference voltage 418 at this time is as shown in FIG.

  The first reference voltage 411 to the eighth reference voltage 418 are changed step by step by a unit voltage over a predetermined period, so that a rapid change in power consumption as a device can be suppressed.

  As an example of when the voltage output permission flag is turned off, the states of the first reference voltage 411 to the eighth reference voltage 418 when the voltage output permission flag in the voltage output control unit 520 is turned off are shown in FIG. In this case, the output of the second reference voltage 412 remains at the GND level.

  The application examples and embodiments of the present invention have been described above, but the implementation of the present invention is not limited to the above contents. For example, in the second embodiment, the setting instruction signal output from the voltage output control unit in which the voltage output permission flag is set to OFF may be directly output as the setting instruction signal. As a result, it is possible to shorten the period for setting the reference voltage. The present invention can be widely applied without departing from the spirit of the present invention.

  DESCRIPTION OF SYMBOLS 10 ... Display apparatus, 100 ... Voltage generation circuit, 101 ... External signal, 102 ... Power supply signal, 110 ... External IF (external interface), 120 ... Control part, 121 ... Internal control signal, 122 ... Data signal, 123 ... Write instruction Signal: 124 ... Write instruction signal, 126 ... Digital signal, 127 ... Analog signal, 130 ... Oscillator, 131 ... Operation clock, 140 ... First voltage generator, 141 ... First reference voltage, 142 ... Output amplifier, 143 ... DAC (Digital-analog converter) 144... 2nd register 145... 1st register 150... 2nd voltage generator 151... 2nd reference voltage 160 ... 3rd voltage generator 161. 170: n-th voltage generator, 171: n-th reference voltage (eighth reference voltage), 200: pixel signal driver circuit, 201: pixel data 202, timing signal, 300, display panel, 400, voltage generation circuit, 410, reference voltage generation unit, 411, first reference voltage, 412, second reference voltage, 417, seventh reference voltage, 418, eighth. Reference voltage, 420 ... voltage dividing unit, 421-428 ... output amplifier, 430 ... voltage change control unit, 501 ... setting instruction signal, 502 ... setting instruction signal, 503 ... setting instruction signal, 507 ... setting instruction signal, 508 ... setting Instruction signal 510 ... Voltage output control unit, 511-519 ... Switch control signal, 520 ... Voltage output control unit, 522-529 ... Switch control signal, 570 ... Voltage output control unit, 777-579 ... Switch control signal, 580 ... Voltage output control unit, 588... Switch control signal, 589.

Claims (10)

A voltage generation circuit that outputs a plurality of voltages,
A first voltage generator for generating a first output voltage;
A second voltage generator that generates a second output voltage that is lower than the first output voltage;
The output of the first output voltage is controlled to become the first reference voltage value while gradually increasing the voltage value,
The output of the second output voltage is controlled to become the second reference voltage value while gradually increasing the voltage value,
The start of the output of the second output voltage is performed after the start of the output of the first output voltage,
A voltage generation characterized in that the time when the first output voltage becomes the first reference voltage value and the time when the second output voltage becomes the second reference voltage value are substantially the same time. circuit. The first output voltage is increased stepwise by a first voltage value,
The second output voltage is increased stepwise by a second voltage value,
The voltage generation circuit according to claim 1, wherein the first voltage value and the second voltage value are substantially the same. And a third voltage generator that generates a third output voltage that is lower than the second output voltage.
The output of the third output voltage is controlled so as to be a third reference voltage value while gradually increasing the third voltage value,
The start of the output of the third output voltage is performed after the start of the output of the second output voltage,
The time when the second output voltage becomes the second reference voltage value and the time when the third output voltage becomes the third reference voltage value are substantially the same time,
The voltage generation circuit according to claim 2, wherein the second voltage value and the third voltage value are substantially the same. The stepwise change timing in the first output voltage and the stepwise change timing in the second output voltage are substantially the same timing,
4. The voltage generation circuit according to claim 3, wherein the stepwise change timing in the second output voltage and the stepwise change timing in the third output voltage are substantially the same timing. A display unit that requires a plurality of reference voltages;
A voltage generation circuit for generating the plurality of voltages,
The voltage generation circuit includes:
A first voltage generator for generating a first output voltage;
A second voltage generator that generates a second output voltage that is lower than the first output voltage;
The output of the first output voltage is controlled to become the first reference voltage value while gradually increasing the voltage value,
The output of the second output voltage is controlled to become the second reference voltage value while gradually increasing the voltage value,
The start of the output of the second output voltage is performed after the start of the output of the first output voltage,
The time when the first output voltage becomes the first reference voltage value and the time when the second output voltage becomes the second reference voltage value are substantially the same time,
The first output voltage is increased stepwise by a first voltage value,
The second output voltage is increased stepwise by a second voltage value,
The display device having a voltage generation circuit, wherein the first voltage value and the second voltage value are substantially the same. The voltage generation circuit further includes a third voltage generation unit that generates a third output voltage that is lower than the second output voltage,
The output of the third output voltage is controlled to be the third reference voltage value while gradually increasing the third voltage value,
The start of the output of the third output voltage is performed after the start of the output of the second output voltage,
The time when the second output voltage becomes the second reference voltage value and the time when the third output voltage becomes the third reference voltage value are substantially the same time,
The display device having a voltage generation circuit according to claim 5, wherein the second voltage value and the third voltage value are substantially the same. A voltage generation method for generating a plurality of voltage outputs,
A first voltage generating step for generating a first output voltage;
A second voltage generation step of generating a second output voltage that is lower than the first output voltage;
Including
In the first voltage generation step, the output of the first output voltage is controlled to be a first reference voltage value while increasing the first voltage value stepwise,
In the second voltage generation step, the output of the second output voltage is controlled to become a second reference voltage value while increasing the second voltage value stepwise.
The start of the second voltage generation step is after the first voltage generation step is started,
In the first voltage generation step and the second voltage generation step, a time when the first output voltage becomes the first reference voltage value and a time when the second output voltage becomes the second reference voltage value Are controlled to be approximately the same time,
The voltage generation method, wherein the first voltage value and the second voltage value are substantially the same. And a third voltage generating step of generating a third output voltage that is a voltage lower than the second output voltage,
In the third voltage generation step, the output of the third output voltage is controlled to be a third reference voltage value while increasing the third voltage value stepwise.
The start of the third voltage generation step is after the second voltage generation step is started,
In the second voltage generation step and the third voltage generation step, a time when the second output voltage becomes the second reference voltage value and a time when the third output voltage becomes the third reference voltage value Are controlled to be approximately the same time,
The voltage generation method according to claim 7, wherein the second voltage value and the third voltage value are substantially the same. A voltage generation circuit that outputs a plurality of voltages,
A first voltage generator for generating a first output voltage;
A second voltage generator that generates a second output voltage that is lower than the first output voltage;
Including
At the time of initial setting, the output of the first output voltage is controlled to become the first reference voltage value while gradually increasing the voltage value,
At the time of initial setting, the output of the second output voltage is controlled to become the second reference voltage value while gradually increasing the voltage value,
The start of the output of the second output voltage is performed after the start of the output of the first output voltage,
A voltage generation characterized in that the time when the first output voltage becomes the first reference voltage value and the time when the second output voltage becomes the second reference voltage value are substantially the same time. circuit. A voltage generation method for generating a plurality of voltage outputs,
A first voltage generating step for generating a first output voltage at the time of initial setting;
A second voltage generating step of generating a second output voltage that is lower than the first output voltage at the time of initial setting;
Including
In the first voltage generation step, the output of the first output voltage is controlled to become the first reference voltage value step by step,
In the second voltage generation step, the output of the second output voltage is controlled so as to gradually become the second reference voltage value,
The start of the second voltage generation step is after the first voltage generation step is started,
In the first voltage generation step and the second voltage generation step, a time when the first output voltage becomes the first reference voltage value and a time when the second output voltage becomes the second reference voltage value Are controlled so as to have substantially the same time.

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