JP7085924B2 - Booster circuit, semiconductor device, liquid crystal display device, and electronic mirror device - Google Patents

Description

The present invention relates to a booster circuit, a semiconductor device, a liquid crystal display device, and an electronic mirror device.

In recent years, semiconductor devices used in fields where high reliability is required, such as automobile applications, are required to have high safety for their functions. For example, ISO 26262 is known as a functional safety standard for automobiles that requires such high safety.

A charge pump circuit is known as a circuit that boosts an input voltage and obtains a high voltage. The charge pump circuit is a circuit that boosts the input voltage by repeatedly switching the switch on and off to generate charge and discharge to the capacitor.

An example of such a charge pump circuit that reduces current consumption while maintaining good boost efficiency is disclosed in Japanese Patent Application Laid-Open No. 2004-005773. In this circuit, when the output boost voltage is low, a charge pump cell with a small number of stages is used, and when the output boost voltage is high, the charge pump cell is switched to a larger number of stages to perform the boost operation.

Japanese Unexamined Patent Publication No. 2004-005773

As a failure mode of the booster circuit including the charge pump circuit, an overvoltage failure mode that outputs an overvoltage can be considered. When an overvoltage failure occurs in the booster circuit, it is conceivable that a voltage exceeding the withstand voltage of the element inside the semiconductor device is applied to the semiconductor device, and as a result, the semiconductor device fails. Therefore, in order to satisfy a strict standard such as ISO26262, it is important to have a mechanism for preventing overvoltage failure, but the technique is not disclosed in the prior art.

The present invention has been made to solve the above-mentioned problems, and an object thereof is a booster circuit capable of quickly eliminating an overvoltage, and a semiconductor device, a liquid crystal display device, and an electronic device including the booster circuit. It is to provide a mirror device.

The booster circuit of the present disclosure receives an input voltage and outputs a booster voltage. The booster circuit consists of a register that holds the value of a variable that indicates the boosting factor when boosting the input voltage, a charge pump circuit that boosts the input voltage with the boosting factor indicated by the value of the variable, and outputs the boosted voltage. It is provided with an overvoltage detection circuit for detecting that the value exceeds the determination value and a boost magnification control circuit for controlling the writing of the value of the variable to the register. The boost magnification control circuit writes the value of the variable to the register when the overvoltage detection circuit detects that the boost voltage exceeds the determination value.

According to the present invention, in a booster circuit having a charge pump circuit in which a booster factor is set in a register, even if an overvoltage occurs, the value of a variable indicating an appropriate booster multiplier is promptly written to the register. The overvoltage can be eliminated quickly.

It is a block diagram which shows the structure of the semiconductor device 21 and the step-up circuit 11 which concerns on Embodiment 1. FIG. It is a circuit diagram which shows the structure of the charge pump circuit 104. It is a figure for demonstrating the control state of the switch element of the charge pump circuit when the step-up magnification is 1.5 times. It is a circuit diagram for demonstrating the control state of each switch element in mode 1-1 when the step-up magnification is 1.5 times. It is a circuit diagram for demonstrating the control state of each switch element in mode 1-2 when the step-up magnification is 1.5 times. It is a figure for demonstrating the control state of the switch element of the charge pump circuit when the step-up magnification is 2 times. It is a circuit diagram for demonstrating the control state of each switch element in mode 2-1 when the step-up magnification is 2 times. It is a circuit diagram for demonstrating the control state of each switch element in mode 2-2 when the step-up magnification is 2 times. It is a figure for demonstrating the control state of the switch element of the charge pump circuit when the step-up magnification is 3 times. It is a circuit diagram for demonstrating the control state of each switch element in mode 3-1 when the step-up magnification is 3 times. It is a circuit diagram for demonstrating the control state of each switch element in mode 3-2 when the step-up magnification is 3 times. It is a flowchart which shows the rewriting process of the value BR1 of the variable which shows the boosting magnification in Embodiment 1. FIG. It is a typical block diagram of the step-up magnification control circuit 103 which executes the process of a flowchart. It is a figure which shows the example of FMEA (Failure Mode and Effect Analysis) of the charge pump circuit. It is a flowchart which shows the process which is executed in the modification of Embodiment 1. It is a block diagram which shows the structure of the semiconductor device 21A and the step-up circuit 11A which concerns on Embodiment 2. FIG. It is a flowchart which shows the rewriting process of the value BR1 of the variable which shows the boost magnification in Embodiment 2. It is a flowchart which shows the process which is executed in the modification of Embodiment 2. It is a block diagram which shows the structure of the semiconductor device 21B and the step-up circuit 11B which concerns on Embodiment 3. FIG. It is a flowchart which shows the process which is executed in the modification of Embodiment 3. It is a block diagram which shows the structure of the semiconductor device 21C and the step-up circuit 11C which concerns on Embodiment 4. FIG. It is a flowchart which shows the rewriting process of the value BR1 of the variable which shows the boost magnification in Embodiment 4. It is a flowchart which shows the process which is executed in the modification of Embodiment 4. It is a figure which shows the structure of the liquid crystal display device to which a booster circuit is applied. It is a figure which shows the state which the electronic mirror device is installed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, a plurality of embodiments will be described, but it is planned from the beginning of the application to appropriately combine the configurations described in the respective embodiments. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

Embodiment 1.
FIG. 1 is a block diagram showing a configuration of a semiconductor device 21 and a booster circuit 11 according to the first embodiment.

The semiconductor device 21 includes a booster circuit 11 and an internal circuit 106. The booster circuit 11 is configured to receive the input voltage Vin and output the booster voltage Vout. The internal circuit 106 is a circuit that receives a boosted voltage Vout as a power supply voltage. The internal circuit 106 is not particularly limited as long as it is a circuit that receives a boosted voltage Vout, but is, for example, a drive circuit for a liquid crystal panel.

The booster circuit 11 boosts the input voltage Vin at the boost factor 102 indicated by the variable value BR1 and the register 102 that holds the value BR1 of the variable indicating the boost magnification when boosting the input voltage Vin, and outputs the boost voltage Vout. The charge pump circuit 104, the overvoltage detection circuit 105 for detecting that the boost voltage Vout exceeds the determination value for determining the overvoltage, and the boost magnification control circuit 103 for controlling the writing of the variable value BR1 to the register 102. To prepare for.

When the overvoltage detection circuit 105 detects that the boost voltage Vout exceeds the determination value, the boost magnification control circuit 103 writes the variable value BR1 to the register 102.

The booster circuit 11 further includes a non-volatile memory 101 that stores a set value BR2 for a variable indicating the booster magnification. When the overvoltage detection circuit 105 detects that the boost voltage Vout exceeds the determination value, the boost magnification control circuit 103 reads the set value BR2 from the non-volatile memory 101, and sets the read set value BR2 as a variable value. Write to register 102 as BR1.

The charge pump circuit 104 is configured so that a plurality of boosting factors can be switched, and generates a boosting voltage Vout based on the value BR1 of the variable indicating the boosting factor stored in the register 102.

In the booster circuit 11 having such a configuration, in order to prevent an overvoltage failure, it is conceivable to stop the booster operation of the charge pump circuit 104 when the overvoltage is detected. When the boosting operation of the charge pump circuit 104 is stopped, the boosting voltage drops. Then, when the boost voltage becomes lower than the overvoltage detection determination value, the operation of the charge pump circuit is restarted.

However, when the boosting operation is stopped and restarted in this way, if the cause of the overvoltage is not eliminated, the overvoltage is intermittently repeatedly generated, and as a result, the ripple of the boosting voltage may increase. For example, when a charge pump circuit mounted on an LED (Light-Emitting Diode) or LCD (Liquid Crystal Display) driver IC (Integrated Circuit) used in a liquid crystal display device repeatedly generates overvoltage, the liquid crystal display is displayed due to an increase in ripple. Flickering occurs on the screen of the device.

In the present embodiment, in order to solve such a problem, a booster circuit capable of preventing an overvoltage while suppressing an increase in the ripple of the boost voltage is proposed. After explaining the configuration and operation of the charge pump circuit, the operation of preventing the overvoltage of the booster circuit 21 will be described below.

FIG. 2 is a circuit diagram showing the configuration of the charge pump circuit 104. With reference to FIG. 2, the charge pump circuit 104 has a pump unit 400 that boosts the input voltage Vin supplied to the input node Nin and outputs the boosted voltage to the node N2, and an output node Nout that outputs the boosted voltage Vout. Includes a switch element 404 connected between the and the output of the pump unit 400. The charge pump circuit 104 further includes a capacitor 503 connected between the output node Nout and the ground node, and a switch control circuit 510.

The pump unit 400 is between the switch element 401 connected between the input node Nin and the node N1, the switch element 402 connected between the node N1 and the ground node, and the input node Nin and the node N2. Includes the switch element 403 to be connected.

The pump unit 400 is further connected between the capacitor 501 connected between the node N2 and the node N3, the switch element 407 connected between the node N3 and the node N1, and the node N2 and the node N4. It includes a switch element 405 to be formed, a switch element 406 connected between the node N3 and the node N4, and a capacitor 502 connected between the node N4 and the node N1.

Preferably, the switch elements 401 to 407 are transistors that receive the gate control signals G401 to G407 at the control electrodes, respectively. The transistor may be, for example, a MOS field effect transistor (Metal-Oxide-Semiconductor Field-Effect Transistor) or a bipolar transistor.

The switch control circuit 510 receives the variable value BR1 from the register 102, and outputs the gate control signals G401 to G407 so that the pump unit 400 performs the boosting operation at the boosting factor corresponding to the received variable value BR1.

FIG. 3 is a diagram for explaining a control state of the switch element of the charge pump circuit when the boost magnification is 1.5 times. When the step-up magnification indicated by the variable value BR1 is 1.5 times, the control states of the modes 1-1 and mode 1-2 shown in FIG. 3 are alternately repeated.

FIG. 4 is a circuit diagram for explaining a control state of each switch element in mode 1-1 when the boost magnification is 1.5 times. As shown in FIGS. 3 and 4, in mode 1-1, the states of the switch elements 401, 402, 403, 404, 405, 406, and 407 are OFF, ON, ON, OFF, OFF, respectively. It is controlled to be ON and OFF. In this state, since the capacitor 501 and the capacitor 502 are connected in series between the ground node and the input node Nin, a voltage of 0.5 × Vin is applied to each of the capacitors 501 and 502.

FIG. 5 is a circuit diagram for explaining a control state of each switch element in mode 1-2 when the boost magnification is 1.5 times. As shown in FIGS. 3 and 5, in mode 1-2, the states of the switch elements 401, 402, 403, 404, 405, 406, and 407 are set to ON, OFF, OFF, ON, ON, respectively. It is controlled to be OFF and ON. In this state, since the capacitor 501 and the capacitor 502 are connected in parallel between the input node Nin and the output node Nout, a voltage of 0.5 × Vin is added to the input voltage Vin, and the boost voltage Vout is 1.5. It becomes × Vin.

FIG. 6 is a diagram for explaining a control state of the switch element of the charge pump circuit when the boost magnification is 2 times. When the boost magnification indicated by the variable value BR1 is 2, the control states of the modes 2-1 and mode 2-2 shown in FIG. 6 are alternately repeated.

FIG. 7 is a circuit diagram for explaining a control state of each switch element in mode 2-1 when the boost magnification is 2 times. As shown in FIGS. 6 and 7, in mode 2-1 the switch elements 401, 402, 403, 404, 405, 406, and 407 are in the OFF, ON, ON, OFF, ON, respectively. It is controlled to be OFF and ON. In this state, since the capacitor 501 and the capacitor 502 are connected in parallel between the ground node and the input node Nin, a voltage of 1.0 × Vin is applied to each of the capacitors 501 and 502.

FIG. 8 is a circuit diagram for explaining a control state of each switch element in mode 2-2 when the boost magnification is 2 times. As shown in FIGS. 6 and 8, in mode 2-2, the states of the switch elements 401, 402, 403, 404, 405, 406, and 407 are set to ON, OFF, OFF, ON, ON, respectively. It is controlled to be OFF and ON. In this state, since the capacitor 501 and the capacitor 502 are connected in parallel between the input node Nin and the output node Nout, a voltage of 1.0 × Vin is added to the input voltage Vin, and the boost voltage Vout is 2.0. It becomes × Vin.

FIG. 9 is a diagram for explaining a control state of the switch element of the charge pump circuit when the boost magnification is 3 times. When the step-up magnification indicated by the variable value BR1 is 3 times, the control states of the modes 3-1 and mode 3-2 shown in FIG. 9 are alternately repeated.

FIG. 10 is a circuit diagram for explaining a control state of each switch element in mode 3-1 when the boost magnification is 3 times. As shown in FIGS. 9 and 10, in mode 3-1 the switch elements 401, 402, 403, 404, 405, 406, and 407 are in the OFF, ON, ON, OFF, ON, respectively. It is controlled to be OFF and ON. In this state, since the capacitor 501 and the capacitor 502 are connected in parallel between the ground node and the input node Nin, a voltage of 1.0 × Vin is applied to each of the capacitors 501 and 502.

FIG. 11 is a circuit diagram for explaining the control state of each switch element in the mode 3-2 when the boost magnification is 3 times. As shown in FIGS. 9 and 11, in mode 3-2, the states of the switch elements 401, 402, 403, 404, 405, 406, and 407 are set to ON, OFF, OFF, ON, OFF, respectively. It is controlled to be ON and OFF. In this state, since the capacitor 501 and the capacitor 502 are connected in series between the input node Nin and the output node Nout, a voltage of 2.0 × Vin is added to the input voltage Vin, and the boost voltage Vout is 3.0. It becomes × Vin.

FIG. 12 is a flowchart showing a rewriting process of the value BR1 of the variable indicating the boosting magnification in the first embodiment. The processing of this flowchart is called and executed in the boost magnification control circuit 103 of FIG. 1 at a predetermined control cycle from the main routine that executes the boosting operation. FIG. 13 is a typical configuration diagram of the boost magnification control circuit 103 that executes the processing of the flowchart. The boost magnification control circuit 103 includes a processor 111 and a memory 112. A program that executes the process of the flowchart of FIG. 12 is stored in the memory 112. This program is read into the processor 111, and the processor 111 operates as the boost magnification control circuit 103. The memory 112 may include the non-volatile memory 101 and the register 102 of FIG. 1. However, the boost magnification control circuit 103 of the present embodiment does not need to be realized by a processor and software, and may be realized by hardware, that is, hard-wired logic or the like.

When the processing of the flowchart of FIG. 12 is started, the boost magnification control circuit 103 determines whether or not the overvoltage detection circuit 105 has detected the overvoltage in step S1. When the overvoltage detection circuit 105 does not detect the overvoltage (NO in S1), the boost magnification control circuit 103 proceeds to step S4 as it is without changing the value BR1 of the variable held in the register 102.

It is considered that the cause of the overvoltage is that the value BR1 of the variable indicating the boost magnification with respect to the input voltage Vin is not appropriate. The set value BR2 indicating the boosting magnification in the boosting operation that should be performed by the charge pump circuit 104 is stored in advance in the non-volatile memory 101. This value is read from the non-volatile memory 101 and written to the register 102 as the variable value BR1 when the power supply of the semiconductor device including the booster circuit 11 is turned on.

For example, when the value BR1 of the variable stored in the register 102 changes due to disturbance noise, the value BR1 of the variable indicating the boost magnification with respect to the input voltage Vin may be in an inappropriate state. For example, when the input voltage Vin is in the voltage range in which the boosting factor should be set to 2 times, and the variable value BR1 changes so as to indicate the boosting factor of 3 times, the boosting voltage Vout becomes overvoltage.

Therefore, when the overvoltage detection circuit 105 detects the overvoltage (YES in S1), the value BR1 of the variable held by the register 102 changes due to noise or the like, and there is a high possibility that the value BR1 of the variable is not a correct value. The boost magnification control circuit 103 reads the boost magnification set value BR2 from the non-volatile memory 101 in step S2.

Then, the booster magnification control circuit 103 stores the booster magnification setting value BR2 read from the non-volatile memory 101 in step S3 as a variable value BR1 in the register 102. As a result, the value BR1 of the variable that has been set to an erroneous value due to noise or the like is rewritten to the correct value. Then, the process proceeds to step S4. In step S4, the process is returned to the main routine, and the boosting operation of the booster circuit 11 is continued. At this time, the charge pump circuit 104 performs a boosting operation at the boosting factor indicated by the value BR1 of the variable newly stored in the register 102.

As described above, according to the booster circuit 11 of the first embodiment, the value BR1 of the variable stored in the register 102 is rewritten to one showing a higher boost magnification than the original due to external noise or the like, thereby boosting the voltage. When the voltage Vout becomes an overvoltage, the overvoltage can be returned to the normal voltage. Specifically, when an overvoltage is detected, the boost voltage is set in the normal range by writing the set value indicating the original boost magnification stored in the non-volatile memory 101 to the register 102 to set the normal boost magnification. It will be possible to fit in.

(Modified Example of Embodiment 1)
In the modified example of the first embodiment, a configuration in which the boosting operation is stopped when an overvoltage occurs when the set value of the boosting magnification is correct will be described.

FIG. 14 is a diagram showing an example of FMEA (Failure Mode and Effect Analysis) of the charge pump circuit. Generally, as a failure mode of a charge pump circuit having a function of changing the boost magnification to 1.5 times, 2 times, and 3 times, as shown in FIG. 14, a failure mode in which the boost voltage becomes an overvoltage and a boost voltage. There is a failure mode in which the voltage becomes low.

In the failure mode in which the boost voltage becomes low, the failure may be due to the malfunction or malfunction of the circuit using the boost voltage as a power source. The setting value of the boost magnification is not appropriate for the input voltage, and the boost magnification is low, or the input voltage range is below the guaranteed operating range, which is considered to be the cause of the failure mode in which the voltage becomes low. Be done. Further, in the case of a failure of the switch element of the charge pump circuit or a failure of the capacitor, the boosting operation cannot be performed, which also causes a failure mode in which the voltage becomes low.

On the other hand, in the case of a failure mode in which the boosted voltage becomes an overvoltage, it is conceivable that the element is destroyed because the boosted voltage exceeds the element withstand voltage of the circuit using the boosted voltage as a power source as an effect of the failure. Further, it is considered that the cause of the failure is that the set value of the boost magnification is not appropriate for the input voltage and the boost magnification is high, and that the input voltage exceeds the operation guarantee range.

Therefore, even in the booster circuit 11 of FIG. 1, the occurrence of overvoltage is not necessarily limited to the case where the value BR1 of the variable held by the register 102 is rewritten by noise or the like. According to FIG. 14, overvoltage may occur even when the input voltage Vin exceeds the operation guarantee range. In such a case, it is not appropriate for the charge pump circuit 104 to continue the boosting operation.

Therefore, in the modification of the first embodiment, when the value BR1 of the variable held by the register 102 is appropriate, the charge pump circuit 104 stops the boosting operation in order to prevent overvoltage.

FIG. 15 is a flowchart showing a process executed in the modified example of the first embodiment. The processing of this flowchart is called and executed in the boost magnification control circuit 103 of FIG. 1 at a predetermined control cycle from the main routine that executes the boosting operation.

When the processing of this flowchart is started, the boost magnification control circuit 103 determines whether or not the overvoltage detection circuit 105 has detected the overvoltage in step S11. When the overvoltage detection circuit 105 does not detect the overvoltage (NO in S11), the boost magnification control circuit 103 proceeds to step S17 as it is without changing the value BR1 of the variable held in the register 102.

On the other hand, when the overvoltage detection circuit 105 detects an overvoltage (YES in S11), there is a possibility that the variable value BR1 held by the register 102 changes due to noise or the like, and the variable value BR1 is not a correct value. high. In this case, the boost magnification control circuit 103 reads the boost magnification set value BR2 from the non-volatile memory 101 in step S12.

Then, the boost magnification control circuit 103 compares the boost magnification setting value BR2 read from the non-volatile memory 101 in step S13 with the variable value BR1 held in the register 102. As a result, it becomes clear whether or not the variable value BR1 is set to an erroneous value due to noise or the like, which is the cause of the overvoltage generation.

Then, in step S14, the booster magnification control circuit 103 determines whether or not the value BR1 of the variable indicating the booster magnification matches the set value BR2.

When the variable value BR1 is different from the set value BR2, it is considered that the overvoltage has occurred because the variable value BR1 stored in the register has been rewritten due to external noise or the like. Therefore, when the variable value BR1 does not match the set value BR2 (NO in S14), in step S15, the booster magnification control circuit 103 rewrites the variable value BR1 to the correct value indicated by the correct set value BR2. Then, the process proceeds to step S17. In step S17, the process is returned to the main routine, and the boosting operation of the booster circuit 11 is continued. At this time, the charge pump circuit 104 performs the boosting operation at the boosting factor indicated by the value BR1 of the newly stored variable.

On the other hand, when the variable value BR1 matches the set value BR2 (YES in S14), there is a possibility that the booster circuit 11 outputs an overvoltage due to a cause other than the setting of the register 102. For example, it is considered that the input voltage exceeds the operation guarantee range, resulting in an overvoltage. In this case, in step S16, the boost magnification control circuit 103 stops the boosting operation of the charge pump circuit 104 and ends the process.

As described above, in the booster circuit of the modified example of the first embodiment, it is determined whether the value BR1 of the variable indicating the booster magnification is appropriate, and if the value BR1 of the variable is appropriate, the charge pump circuit 104. Stop the boost operation.

More specifically, the boost magnification control circuit 103 reads the variable value BR1 from the register 102 when the overvoltage detection circuit 105 detects that the boost voltage Vout exceeds the determination value. When the variable value BR1 read from the register 102 is different from the set value BR2 read from the non-volatile memory 101, the booster magnification control circuit 103 sets the set value BR2 as the variable value BR1 and registers 102. Write to. On the other hand, the boost magnification control circuit 103 stops the boosting operation of the charge pump circuit 104 when the variable value BR1 read from the register 102 matches the set value BR2 read from the non-volatile memory 101. Let me.

By controlling in this way, it is possible to avoid a situation in which the generation of overvoltage continues, and it is possible to prevent failure of the internal circuit 106 due to overvoltage.

Embodiment 2.
The booster circuit of the first embodiment obtains the booster magnification setting value from the non-volatile memory 101, while the booster circuit of the second embodiment obtains the booster magnification setting value from an external device outside the semiconductor device. FIG. 16 is a block diagram showing the configuration of the semiconductor device 21A and the booster circuit 11A according to the second embodiment.

The semiconductor device 21A includes a booster circuit 11A and an internal circuit 106. The booster circuit 11A is configured to receive the input voltage Vin and output the booster voltage Vout. The internal circuit 106 is a circuit that receives a boosted voltage Vout as a power supply voltage. The internal circuit 106 is not particularly limited as long as it is a circuit that receives a boosted voltage Vout, but is, for example, a drive circuit for a liquid crystal panel.

The booster circuit 11A boosts the input voltage Vin and outputs the boost voltage Vout with the register 102 holding the value BR1 of the variable indicating the boost magnification when boosting the input voltage Vin and the boost magnification indicated by the variable value BR1. The charge pump circuit 104 is provided, the overvoltage detection circuit 105 for detecting that the boost voltage Vout exceeds the determination value, and the boost magnification control circuit 103A for controlling the writing of the variable value BR1 to the register 102.

The charge pump circuit 104 is configured so that a plurality of boosting factors can be switched, and generates a boosting voltage based on the value BR1 of the variable indicating the boosting factor stored in the register 102.

When the overvoltage detection circuit 105 detects that the boost voltage Vout exceeds the determination value, the boost magnification control circuit 103A writes the variable value BR1 to the register 102. Regarding the above points, the booster circuit 11A is generally the same as the booster circuit 11 of the first embodiment, but the operation of the booster magnification control circuit 103A is different.

When the boost magnification control circuit 103A receives a command including the boost magnification setting value BR2 from the external device 12, the boost magnification control circuit 103A stores the boost magnification setting value BR2 included in the command in the register 102.

When the overvoltage detection circuit 105 detects that the boost voltage Vout exceeds the determination value, the boost magnification control circuit 103A requests the external device 12 to transmit the set value BR2 indicating the correct boost magnification, and requests it. Accordingly, the set value BR2 transmitted from the external device 12 is written to the register 102 as the variable value BR1.

FIG. 17 is a flowchart showing a rewriting process of the value BR1 of the variable indicating the boosting magnification in the second embodiment. The process of this flowchart is called and executed in the boost magnification control circuit 103A of FIG. 16 from the main routine for executing the boost operation at a predetermined control cycle. Further, the typical configuration of the boost magnification control circuit 103A that executes the processing of the flowchart is the same as that of FIG. 13, and the description thereof will not be repeated.

When the processing of the flowchart of FIG. 17 is started, the boost magnification control circuit 103A determines whether or not the overvoltage detection circuit 105 has detected the overvoltage in step S21. When the overvoltage detection circuit 105 does not detect the overvoltage (NO in S21), the boost magnification control circuit 103A proceeds to step S24 as it is without changing the value BR1 of the variable held in the register 102.

It is considered that the cause of the overvoltage is that the value BR1 of the variable indicating the boost magnification with respect to the input voltage Vin is not appropriate. The set value BR2 indicating the boosting magnification in the boosting operation that should be performed by the charge pump circuit 104 is set by a command transmitted by the external device 12. This value is written to the register 102 in response to a command given from the external device 12 when the power supply of the semiconductor device including the booster circuit 11A is turned on.

For example, when the variable value BR1 stored in the register 102 changes due to disturbance noise, or when the wrong variable value BR1 is stored in the register 102 due to a misrecognition of a command transmitted from the external device 12. , The value BR1 of the variable indicating the boost magnification with respect to the input voltage Vin may be in an inappropriate state.

Therefore, when the overvoltage detection circuit 105 detects the overvoltage (YES in S21), there is a high possibility that the value BR1 of the variable held by the register 102 is not a correct value, so that the boost magnification control circuit 103A is stepped. In S22, the external device 12 is requested to retransmit the command including the information of the boost magnification set value BR2.

The external device 12 transmits a command to the boost magnification control circuit 103A according to the retransmission request. The boost magnification control circuit 103A stores the set value BR2 indicated by the content of the command received from the external device 12 in step S23 in the register 102 as the variable value BR1. As a result, the value BR1 of the variable set to the incorrect value is rewritten to the correct value. Then, the process proceeds to step S24. In step S24, the process is returned to the main routine, and the boosting operation of the booster circuit 11A is continued. At this time, the charge pump circuit 104 performs the boosting operation at the boosting factor indicated by the value BR1 of the newly stored variable.

As described above, according to the booster circuit of the second embodiment, the value BR1 of the variable indicating the booster magnification stored in the register 102 due to erroneous recognition of the command becomes a value indicating the booster magnification higher than the appropriate value. This is effective when an overvoltage occurs. In this case, the boost magnification control circuit 103A requests the external device 12 to retransmit the command. By having the command including the setting value information of the boosting magnification retransmitted in this way, the variable value BR1 is reset to the register 102 so as to indicate the appropriate boosting magnification, and the boosting voltage Vout is kept within the normal range. Can be done.

(Modified Example of Embodiment 2)
In the modified example of the second embodiment, similarly to the modified example of the first embodiment, control for stopping the boosting operation when an overvoltage occurs when the set value of the boosting magnification is correct will be described. FIG. 18 is a flowchart showing a process executed in the modified example of the second embodiment. The process of this flowchart is called and executed in the boost magnification control circuit 103A of FIG. 16 from the main routine for executing the boost operation at a predetermined control cycle.

When the processing of this flowchart is started, the boost magnification control circuit 103A determines whether or not the overvoltage detection circuit 105 has detected the overvoltage in step S31. When the overvoltage detection circuit 105 does not detect the overvoltage (NO in S31), the boost magnification control circuit 103A proceeds to step S37 as it is without changing the value BR1 of the variable held in the register 102.

On the other hand, when the overvoltage detection circuit 105 detects the overvoltage (YES in S31), there is a high possibility that the value BR1 of the variable held in the register 102 is not a correct value due to erroneous recognition of a command or the like. In that case, the boost magnification control circuit 103A requests the external device 12 to retransmit the command in step S32. This command contains information on the set value BR2 indicating the correct boost magnification.

Then, the boost magnification control circuit 103A compares the boost magnification setting value BR2 indicated by the command retransmitted from the external device 12 in step S33 with the variable value BR1 held in the register 102. As a result, it becomes clear whether or not the variable value BR1 is set to an erroneous value due to erroneous recognition of a command or the like, which is the cause of the overvoltage generation.

Then, in step S34, the booster magnification control circuit 103A determines whether or not the value BR1 of the variable indicating the booster magnification matches the set value BR2.

When the value BR1 of the variable indicating the boost magnification is different from the set value BR2, it is considered that the overvoltage has occurred because the value BR1 of the variable stored in the register is not an appropriate value due to erroneous recognition of the command or the like. Therefore, when the variable value BR1 does not match the set value BR2 (NO in S34), in step S35, the boost magnification control circuit 103A rewrites the variable value BR1 to the correct value indicated by the set value BR2. Then, the process proceeds to step S37. In step S37, the process is returned to the main routine, and the boosting operation of the booster circuit 11A is continued. At this time, the charge pump circuit 104 performs the boosting operation at the boosting factor indicated by the value BR1 of the newly stored variable.

On the other hand, when the variable value BR1 matches the set value BR2 (YES in S34), there is a possibility that the booster circuit 11A outputs an overvoltage due to a cause other than the setting of the register 102. For example, it is considered that the input voltage exceeds the operation guarantee range, resulting in an overvoltage. In this case, in step S36, the boost magnification control circuit 103A stops the boosting operation of the charge pump circuit 104 and ends the process.

As described above, in the booster circuit of the modified example of the second embodiment, it is determined whether the value BR1 of the variable indicating the booster magnification is appropriate, and if the value BR1 of the variable is appropriate, the charge pump circuit 104. Stop the boost operation.

More specifically, the boost magnification control circuit 103A reads the variable value BR1 from the register 102 when the overvoltage detection circuit 105 detects that the boost voltage Vout exceeds the determination value. Then, when the variable value BR1 read from the register 102 is different from the set value BR2 transmitted from the external device 12, the boost magnification control circuit 103A writes the set value BR2 to the register 102 as the variable value BR1. .. On the other hand, the boost magnification control circuit 103A stops the boosting operation of the charge pump circuit 104 when the value BR1 of the variable read from the register 102 matches the set value BR2 transmitted from the external device 12.

By controlling in this way, the booster circuit of the modified example of the second embodiment can avoid the situation where the overvoltage continues to be generated in addition to the effect of the booster circuit of the second embodiment, and the overvoltage can be prevented. It is possible to prevent the failure of the internal circuit 106 due to the above.

Embodiment 3.
In the booster circuits of the first and second embodiments, the set value is rewritten when an overvoltage is detected in order to return the value of the variable held by the register to the original value. On the other hand, in the booster circuit of the third embodiment, a case where the value of the variable held by the register is rewritten so as to reduce the booster magnification will be described. FIG. 19 is a block diagram showing the configuration of the semiconductor device 21B and the booster circuit 11B according to the third embodiment.

The semiconductor device 21B includes a booster circuit 11B and an internal circuit 106. The booster circuit 11B is configured to receive the input voltage Vin and output the booster voltage Vout. The internal circuit 106 is a circuit that receives a boosted voltage Vout as a power supply voltage. The internal circuit 106 is not particularly limited as long as it is a circuit that receives a boosted voltage Vout, but is, for example, a drive circuit for a liquid crystal panel.

The booster circuit 11B boosts the input voltage Vin with the register 102 holding the value BR1 of the variable indicating the boosting factor when boosting the input voltage Vin and the boosting factor indicated by the variable value BR1, and outputs the boosted voltage Vout. It includes a charge pump circuit 104, an overvoltage detection circuit 105 that detects that the boost voltage Vout exceeds a determination value, and a boost magnification control circuit 103B that controls writing of the variable value BR1 to the register 102.

The charge pump circuit 104 is configured so that a plurality of boosting factors can be switched, and generates a boosting voltage based on the value BR1 of the variable indicating the boosting factor stored in the register 102.

When the overvoltage detection circuit 105 detects that the boost voltage Vout exceeds the determination value, the boost magnification control circuit 103B writes the variable value BR1 to the register 102. Regarding the above points, the booster circuit 11B is generally the same as the booster circuit 11 of the first embodiment, but the operation of the booster magnification control circuit 103B is different.

The boost magnification control circuit 103B has a variable value with respect to the register 102 so that the boost magnification indicated by the variable value BR1 decreases when the overvoltage detection circuit 105 detects that the boost voltage Vout exceeds the determination value. Rewrite BR1. For example, if the value BR1 of the variable is a value indicating a boost magnification of 3 times, this is rewritten to a value indicating 2 times or 1.5 times.

According to the booster circuit 11B of the third embodiment, when an overvoltage is detected, the value of the variable indicating the booster magnification is changed to a value indicating a magnification lower than the present, so that the booster voltage Vout becomes an overvoltage. Can be prevented.

(Modified Example of Embodiment 3)
In the modified example of the third embodiment, a configuration is described in which the boosting operation is stopped when the overvoltage continues to be generated even when the set value of the boosting magnification is lowered.

In the modification of the third embodiment, the boost magnification control circuit 103B rewrites the variable value BR1 with respect to the register 102 so that the boost magnification indicated by the variable value BR1 decreases, and then the boost voltage determines the determination value. When the overvoltage detection circuit 105 detects again within a certain determination period, the boosting operation of the charge pump circuit 104 is stopped.

FIG. 20 is a flowchart showing a process executed in the modified example of the third embodiment. The process of this flowchart is called and executed in the boost magnification control circuit 103B of FIG. 19 from the main routine for executing the boost operation at a predetermined control cycle.

When the processing of this flowchart is started, the boost magnification control circuit 103B determines whether or not the overvoltage detection circuit 105 has detected the overvoltage in step S41. When the overvoltage detection circuit 105 does not detect the overvoltage (NO in S41), the boost magnification control circuit 103B proceeds to step S45 as it is without changing the value BR1 of the variable held in the register 102.

On the other hand, when the overvoltage detection circuit 105 detects the overvoltage (YES in S41), the boost magnification control circuit 103B sets the value BR1 of the variable held by the register 102 in step S42 to a lower boost magnification than the present. Rewrite to the indicated value. For example, if the current boost factor is 3x, the variable value BR1 is changed to indicate a boost factor of 2x or 1.5x.

Subsequently, in step S43, the boost magnification control circuit 103B determines whether or not the overvoltage detection circuit 105 detects the overvoltage again within the determination period. If the overvoltage is detected again within the determination period (YES in S43), it is considered that the overvoltage has occurred due to the failure of the charge pump circuit 104. Therefore, the boost magnification control circuit 103B boosts the charge pump circuit 104 in step S44. Stops the operation and ends the process.

On the other hand, if the overvoltage is not detected within the determination period (NO in S43), it is considered that the overvoltage has been eliminated by changing the boost magnification, so that the boost magnification control circuit 103B does not perform the process of step S44 and takes step S45. Proceed to the process. In this case, the process is returned to the main routine, and the charge pump circuit 104 continues to operate at the changed boost magnification.

According to the booster circuit 11B of the modification of the third embodiment, when an overvoltage is detected, the value of the variable indicating the booster magnification is changed to a value indicating a magnification lower than the present, so that the booster voltage Vout becomes an overvoltage. It can be prevented from becoming. Further, if the overvoltage is detected even after the variable value BR1 is changed, the operation of the charge pump circuit is stopped, so that the situation where the overvoltage continues to occur can be avoided, and the internal circuit due to the overvoltage can be avoided. It is possible to prevent the failure of 106.

Embodiment 4.
In the booster circuit of the fourth embodiment, unlike the other embodiments, the input voltage is measured, the booster magnification corresponding to the input voltage is calculated, and the value of the variable is rewritten. Such control is particularly suitable when the input voltage fluctuates. FIG. 21 is a block diagram showing the configuration of the semiconductor device 21C and the booster circuit 11C according to the fourth embodiment.

The semiconductor device 21C includes a booster circuit 11C and an internal circuit 106. The booster circuit 11C is configured to receive the input voltage Vin and output the booster voltage Vout. The internal circuit 106 is a circuit that receives a boosted voltage Vout as a power supply voltage. The internal circuit 106 is not particularly limited as long as it is a circuit that receives a boosted voltage Vout, but is, for example, a drive circuit for a liquid crystal panel.

The booster circuit 11C boosts the input voltage Vin with the register 102 holding the value BR1 of the variable indicating the boosting factor when boosting the input voltage Vin and the boosting factor indicated by the variable value BR1, and outputs the boosted voltage Vout. It includes a charge pump circuit 104, an overvoltage detection circuit 105 that detects that the boost voltage Vout exceeds a determination value, and a boost magnification control circuit 103C that controls writing of the variable value BR1 to the register 102.

The charge pump circuit 104 is configured to be able to switch between a plurality of boosting factors, and generates a boosting voltage at the boosting factor indicated by the value BR1 of the variable stored in the register 102.

When the overvoltage detection circuit 105 detects that the boost voltage Vout exceeds the determination value, the boost magnification control circuit 103C writes the variable value BR1 to the register 102. Regarding the above points, the booster circuit 11C is generally the same as the booster circuit 11 of the first embodiment, but the operation of the booster magnification control circuit 103C is different.

The booster circuit 11C is an AD converter 201 that converts an input voltage Vin into a digital value, and a booster magnification calculation circuit that receives a digital value output by the AD converter 201 and calculates a booster magnification setting value corresponding to the input voltage Vin. Further equipped with 202.

The booster magnification control circuit 103C is configured to write the set value BR3 of the booster magnification calculated by the booster magnification calculation circuit 202 to the register 102 as the variable value BR1.

Since the input voltage Vin is observed by using the AD converter 201 and the boosting ratio is changed according to the change of the input voltage Vin, the charge pump circuit 104 operates at an appropriate boosting ratio even if the input voltage Vin changes. It is possible to do. Further, by performing the AD conversion at regular intervals, it is possible to reduce the power consumption as compared with the constant AD conversion.

When the overvoltage detection circuit 105 detects that the boost voltage Vout exceeds the determination value, the boost magnification control circuit 103C outputs a trigger signal TG to the AD converter 201 so as to convert the input voltage Vin into a digital value. Send and request. Further, the booster magnification control circuit 103C writes the set value BR3 of the booster magnification calculated by the booster magnification calculation circuit 202 as the variable value BR1 in the register 102.

By transmitting the trigger signal TG in this way, the AD converter 201 performs an AD conversion operation at a requested time, in addition to the AD conversion operation performed at a fixed cycle. As a result, the boost magnification setting value BR3 corresponding to the input voltage Vin at the time when the overvoltage is generated is calculated by the boost magnification calculation circuit 202, and this value is stored in the register 102 as the variable value BR1.

FIG. 22 is a flowchart showing a rewriting process of the value BR1 of the variable indicating the boosting magnification in the fourth embodiment. The process of this flowchart is called and executed in the boost magnification control circuit 103C of FIG. 21 from the main routine for executing the boost operation at a predetermined control cycle. Further, the typical configuration of the boost magnification control circuit 103C that executes the processing of the flowchart is the same as that of FIG. 13, and the description thereof will not be repeated.

When the processing of the flowchart of FIG. 22 is started, the boost magnification control circuit 103C determines whether or not the overvoltage detection circuit 105 has detected the overvoltage in step S51. When the overvoltage detection circuit 105 does not detect the overvoltage (NO in S51), the boost magnification control circuit 103C proceeds to step S52.

In step S52, the boost magnification control circuit 103C determines whether or not a certain time has elapsed since the previous timer was cleared. If a certain time has not elapsed yet (NO in S52), the boost magnification control circuit 103C proceeds to step S56 without performing AD conversion.

On the other hand, if a certain time has elapsed in step S52 (YES in S52), the boost magnification control circuit 103C clears the timer counting the passage of time in step S53 and processes in step S54. To proceed.

Further, even when the overvoltage detection circuit 105 detects the overvoltage in step S51 (YES in S51), the boost magnification control circuit 103C proceeds to the process in step S54. The timer may be cleared at this time as well.

In step S54, the boost magnification control circuit 103C requests the AD converter 201 to execute the AD conversion. As a result, the input voltage Vin at that time is converted into a digital value, and the boost magnification calculation circuit 202 receives the updated digital value. The boost magnification calculation circuit 202 calculates the boost magnification corresponding to this digital value, and outputs the updated boost magnification setting value BR3 to the boost magnification control circuit 103C.

Subsequently, in step S55, the boost magnification control circuit 103C writes the obtained set value BR3 to the register 102. Then, the process proceeds to step S56. In step S56, the process is returned to the main routine, and the boosting operation of the booster circuit 11C is continued. At this time, the charge pump circuit 104 performs the boosting operation at the boosting factor indicated by the value BR1 of the newly stored variable.

Even in the booster circuit 11C that obtains the set value of the booster magnification by AD-converting the input voltage Vin at regular intervals by performing such control, when an overvoltage is detected, the AD converter 201 is immediately used. Since the AD conversion request is issued, it is possible to quickly respond to the overvoltage while suppressing the power consumption.

(Modified Example of Embodiment 4)
In the modified example of the fourth embodiment, a configuration is described in which the boosting operation is stopped when the overvoltage continues to be generated even when the set value of the boosting magnification is changed. FIG. 23 is a flowchart showing the processing executed in the modified example of the fourth embodiment. The process of this flowchart is called and executed in the boost magnification control circuit 103C of FIG. 21 from the main routine for executing the boost operation at a predetermined control cycle.

When the processing of this flowchart is started, the boost magnification control circuit 103C determines whether or not the overvoltage detection circuit 105 has detected the overvoltage in step S61. When the overvoltage detection circuit 105 does not detect the overvoltage (NO in S61), the boost magnification control circuit 103C proceeds to step S62.

In step S62, the boost magnification control circuit 103C determines whether or not a certain time has elapsed since the previous timer was cleared. If a certain time has not passed yet (NO in S62), the boost magnification control circuit 103C proceeds to step S69 without performing AD conversion.

On the other hand, if a certain time has elapsed in step S62 (YES in S62), the boost magnification control circuit 103C clears the timer counting the passage of time in step S63 and processes in step S64. To proceed.

Further, even when the overvoltage detection circuit 105 detects the overvoltage in step S61 (YES in S61), the boost magnification control circuit 103C proceeds to the process in step S64. The timer may be cleared at this time as well.

In step S64, the boost magnification control circuit 103C requests the AD converter 201 to execute the AD conversion. As a result, the input voltage Vin at that time is converted into a digital value, and the boost magnification calculation circuit 202 receives the updated digital value. The boost magnification calculation circuit 202 calculates the boost magnification corresponding to this digital value, and outputs the updated boost magnification setting value BR3 to the boost magnification control circuit 103C.

Subsequently, in step S65, the booster magnification control circuit 103C compares the booster magnification setting value BR3 calculated by the booster magnification calculation circuit 202 based on the AD conversion result with the variable value BR1 held in the register 102.

Then, in step S66, the boost magnification control circuit 103C determines whether or not the value BR1 of the variable indicating the boost magnification matches the set value BR3.

If the value BR1 of the variable indicating the boost magnification is different from the set value BR3, the overvoltage is due to the variable value BR1 stored in the register being no longer an appropriate value due to a sudden change in the input voltage Vin or a malfunction of the AD conversion. It is thought that it became. Therefore, when the variable value BR1 does not match the set value BR3 (NO in S66), in step S67, the boost magnification control circuit 103C sets the variable to the correct value indicated by the set value BR3 obtained by the AD conversion. Rewrite the value BR1. Then, the process proceeds to step S69. In step S69, the process is returned to the main routine, and the boosting operation of the booster circuit 11C is continued. At this time, the charge pump circuit 104 performs the boosting operation at the boosting factor indicated by the value BR1 of the newly stored variable.

On the other hand, when the variable value BR1 matches the set value BR3 (YES in S66), there is a possibility that the booster circuit 11C outputs an overvoltage due to a cause other than the setting of the register 102. For example, it is considered that the input voltage exceeds the operation guarantee range, resulting in an overvoltage. In this case, in step S68, the boost magnification control circuit 103C stops the boosting operation of the charge pump circuit 104 and ends the process.

As described above, in the modified example of the fourth embodiment, when the overvoltage detection circuit 105 detects that the boost voltage Vout exceeds the determination value, the boost magnification control circuit 103C has a variable value BR1 from the register 102. Is read. When the variable value BR1 read from the register 102 is different from the booster magnification set value BR3 calculated by the booster multiplier calculation circuit 202, the booster magnification control circuit 103C is boosted by the booster magnification calculation circuit. The magnification setting value BR3 is written to the register 102 as the variable value BR1. On the other hand, in the boost magnification control circuit 103C, when the value BR1 of the variable read from the register 102 matches the set value BR3 of the boost magnification calculated by the boost magnification calculation circuit 202, the boost magnification of the charge pump circuit 104 is boosted. Stop the operation.

According to the booster circuit 11C of the modified example of the fourth embodiment, when the variable value BR1 is an appropriate value, the operation of the charge pump circuit is stopped, so that the situation where the overvoltage continues to occur is avoided. This makes it possible to prevent the internal circuit 106 from failing due to overvoltage.

In steps S51 to S53 of FIG. 22 and steps S61 to S63 of FIG. 23, when the overvoltage is not detected, the timer is cleared after waiting for a certain period of time, but the timer is not limited to this. It may be the processing of. For example, a process requesting AD conversion may be executed at regular intervals, and AD conversion may be executed by interrupt processing when an overvoltage is detected in parallel with the process. When the processing is realized by hardware, a hard-wired logic that periodically operates the AD conversion request to the AD converter and the AD conversion request by detecting the overvoltage is used. It may be realized.

(Control of boost magnification change timing)
In the first to fourth embodiments described above, in the boost magnification control circuits 103, 103A, 103B, 103C, the switch element 404 of the charge pump circuit 104 shown in FIG. 2 is turned off when the value BR1 of the variable held by the register 102 is changed. It is preferable to do it in the state.

The charge pump circuit 104 is a circuit that switches the charge / discharge to the capacitors 501, 502, 503 by turning on and off the switch elements 401 to 407 to boost the voltage. When the value BR1 of the variable stored in the register 102 is rewritten while the switch element 404 connected to the output node Out is on, the boost voltage Vout fluctuates due to the connection switching of the switch element 404 connected to the capacitor 503. There is a fear. Therefore, by rewriting the value BR1 of the variable stored in the register 102 while the switch element 404 connected to the output node Nout is off, the fluctuation of the boost voltage Vout when the set value of the boost magnification is changed is suppressed. be able to.

(Application example of booster circuit)
The booster circuit and the semiconductor device shown in the first to fourth embodiments can be used for a liquid crystal display device and an electronic mirror device including the liquid crystal display device.

FIG. 24 is a diagram showing a configuration of a liquid crystal display device to which a booster circuit is applied. With reference to FIG. 24, the liquid crystal display device 601 includes a liquid crystal panel 602, an LCD driver IC 603, 604, an LED driver IC 605, and a light emitting element 606.

The LED driver IC 605 emits light from a light emitting element 606 to which LEDs are connected in series. The light from the light emitting element 606 is used as a backlight of the liquid crystal panel 602.

The LCD driver IC 603 includes a plurality of driving elements arranged along the horizontal direction of the liquid crystal panel 602. The LCD driver IC 604 includes a plurality of driving elements arranged along the vertical direction of the liquid crystal panel 602. An image is displayed on the liquid crystal panel 602 by driving the liquid crystal element of the liquid crystal panel 602 on the LCD driver ICs 603 and 604.

In such a liquid crystal display device 601, the LED driver IC 605 and the LCD driver ICs 603 and 604 are configured to have a built-in booster circuit or to supply a booster voltage from the booster circuit. As this booster circuit, the booster circuit shown in the first to fourth embodiments can be used. Further, in the semiconductor device shown in the first to fourth embodiments, the internal circuit 106 is an LCD drive element or a liquid crystal drive element, so that the semiconductor device of the first to fourth embodiments becomes an LED driver IC or an LCD driver IC.

FIG. 25 is a diagram showing a state in which the electronic mirror device is installed. As shown in FIG. 25, the electronic mirror devices 701 to 703 are installed around the front seat of the vehicle. The electronic mirror devices 701 to 703 can be visually recognized from the driver's seat provided with the steering wheel 704. The electronic mirror device 701 is a rear-view mirror. The electronic mirror devices 702 and 703 are door mirrors.

A liquid crystal display device is adopted as these electronic mirror devices. For example, if the booster circuit of the present embodiment is mounted on an in-vehicle liquid crystal display device, it is possible to suppress the occurrence of flicker on the liquid crystal screen due to repeated boosting stop due to overvoltage detection and boosting restart due to voltage drop. As a result, the driver's comfort when driving the vehicle is improved.

The embodiments disclosed this time should be considered to be exemplary and not restrictive in all respects. The scope of the present invention is shown by the scope of claims rather than the description of the embodiments described above, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

11, 11A, 11B, 11C booster circuit, 12 external device, 21,21A, 21B, 21C semiconductor device, 101 non-volatile memory, 102 register, 103, 103A, 103B, 103C boost magnification control circuit, 104 charge pump circuit, 105 Overvoltage detection circuit, 106 internal circuit, 111 processor, 112 memory, 201 converter, 202 boost magnification calculation circuit, 400 pump section, 401-407 switch element, 501-503 capacitor, 510 switch control circuit, 601 liquid crystal display device, 602 Liquid crystal panel, 603 to 605 driver IC, 606 light emitting element, 701 to 703 electronic mirror device, N1 to N4 node, Now output node.

Claims (10)

A booster circuit that receives an input voltage and outputs a booster voltage.
A register that holds the value of a variable that indicates the boost magnification when boosting the input voltage, and
A charge pump circuit that boosts the input voltage at the boosting factor indicated by the value of the variable and outputs the boosted voltage.
An overvoltage detection circuit that detects that the boosted voltage exceeds the determination value, and
A boost magnification control circuit that controls the writing of the value of the variable to the register, and
It is equipped with a non-volatile memory that stores the set values for the variables .
When the overvoltage detection circuit detects that the boost voltage exceeds the determination value, the boost magnification control circuit writes the value of the variable to the register .
When the overvoltage detection circuit detects that the boost voltage exceeds the determination value, the boost magnification control circuit reads the set value from the non-volatile memory and uses the read set value as the variable. Write to the register as the value of
The boost magnification control circuit reads the value of the variable from the register when the overvoltage detection circuit detects that the boost voltage exceeds the determination value.
(A) When the value of the variable read from the register is different from the set value read from the non-volatile memory, the set value is written to the register as the value of the variable.
(B) A booster circuit for stopping the boosting operation of the charge pump circuit when the value of the variable read from the register matches the set value read from the non-volatile memory . A booster circuit that receives an input voltage and outputs a booster voltage.
A register that holds the value of a variable that indicates the boost magnification when boosting the input voltage, and
A charge pump circuit that boosts the input voltage at the boosting factor indicated by the value of the variable and outputs the boosted voltage.
An overvoltage detection circuit that detects that the boosted voltage exceeds the determination value, and
A boost magnification control circuit for controlling the writing of the value of the variable to the register is provided.
When the overvoltage detection circuit detects that the boost voltage exceeds the determination value, the boost magnification control circuit writes the value of the variable to the register.
When the overvoltage detection circuit detects that the boost voltage exceeds the determination value, the boost magnification control circuit requests the external device to transmit a set value indicating the boost magnification, and responds to the request. The set value transmitted from the external device is written to the register as the value of the variable, and the setting value is written to the register.
The boost magnification control circuit reads the value of the variable from the register when the overvoltage detection circuit detects that the boost voltage exceeds the determination value.
(A) When the value of the variable read from the register is different from the set value transmitted from the external device, the set value is written to the register as the value of the variable.
(B) A booster circuit for stopping the boosting operation of the charge pump circuit when the value of the variable read from the register matches the set value transmitted from the external device. The variable booster control circuit holds the variable so that the booster factor indicated by the value of the variable decreases when the overvoltage detection circuit detects that the booster voltage exceeds the determination value. The booster circuit according to claim 1 or 2 , wherein the value of is rewritten. The boost magnification control circuit detects that the boost voltage exceeds the determination value after rewriting the value of the variable held by the register so that the boost magnification indicated by the value of the variable decreases. The booster circuit according to claim 3, wherein if the circuit detects again within the determination period, the booster operation of the charge pump circuit is stopped. A booster circuit that receives an input voltage and outputs a booster voltage.
A register that holds the value of a variable that indicates the boost magnification when boosting the input voltage, and
A charge pump circuit that boosts the input voltage at the boosting factor indicated by the value of the variable and outputs the boosted voltage.
An overvoltage detection circuit that detects that the boosted voltage exceeds the determination value, and
A boost magnification control circuit that controls the writing of the value of the variable to the register, and
An AD converter that converts the input voltage into a digital value,
It is provided with a boost magnification calculation circuit that receives the digital value output by the AD converter and calculates a boost magnification setting value corresponding to the input voltage.
When the overvoltage detection circuit detects that the boost voltage exceeds the determination value, the boost magnification control circuit writes the value of the variable to the register.
The booster magnification control circuit is configured to write the set value of the booster magnification calculated by the booster magnification calculation circuit to the register as the value of the variable.
The boost magnification control circuit requests the AD converter to convert the input voltage into the digital value when the overvoltage detection circuit detects that the boost voltage exceeds the determination value. At the same time , the booster circuit writes the set value of the booster magnification calculated by the booster magnification calculation circuit to the register as the value of the variable. The boost magnification control circuit reads the value of the variable from the register when the overvoltage detection circuit detects that the boost voltage exceeds the determination value.
(A) When the value of the variable read from the register is different from the booster magnification setting value calculated by the booster magnification calculation circuit, the booster magnification setting value calculated by the booster magnification calculation circuit is used. Write to the register as the value of the variable,
(B) Claim 5 to stop the boosting operation of the charge pump circuit when the value of the variable read from the register matches the set value of the boosting factor calculated by the boosting factor calculation circuit. The booster circuit described in. The charge pump circuit is
A pump unit that boosts the input voltage supplied to the input node, and
It includes a switch element connected between an output node that outputs the boosted voltage and the output of the pump unit.
The booster circuit according to any one of claims 1 to 6 , wherein the boost magnification control circuit changes the value of the variable held by the register when the switch element is in the off state. A semiconductor device comprising the booster circuit according to any one of claims 1 to 7 . The semiconductor device according to claim 8 and
A liquid crystal display device including a liquid crystal panel driven by the semiconductor device. An electronic mirror device including the liquid crystal display device according to claim 9 .

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