Voltage conversion circuit, semiconductor circuit, and motor drive module

Abstract

To provide a voltage conversion circuit with improved reliability by suppressing the fluctuation of voltage in the circuit.SOLUTION: A voltage conversion circuit according to an embodiment includes: a current limit circuit including a first switch; a first-stage diode connected to the current limit circuit; a charge pump circuit including two or more second-stage diodes connected in series to the first-stage diode; and a current supply circuit connected between the second-stage diodes of the charge pump circuit and including a rectifying unit in which a direction toward the charge pump circuit is a forward direction, and SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a voltage conversion circuit, a semiconductor circuit, and a motor drive module. [Background technology]

[0002] 2. Description of the Related Art Charge pump voltage conversion circuits are known that convert a power supply voltage into an output voltage of a desired voltage value. Charge pump voltage conversion circuits boost the power supply voltage using multiple stages of switched capacitors and output the boosted voltage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-164142 Summary of the Invention [Problem to be solved by the invention]

[0004] The problem to be solved by the present invention is to provide a voltage conversion circuit that suppresses fluctuations in voltage within the circuit and has improved reliability. [Means for solving the problem]

[0005] The voltage conversion circuit of the embodiment includes a current limiting circuit having a first switch, a first-stage diode connected to the current limiting circuit, a charge pump circuit having two or more subsequent-stage diodes connected in series to the first-stage diode, and a current supply circuit connected between the subsequent-stage diodes of the charge pump circuit and having a rectifier unit whose forward direction is toward the charge pump circuit. The motor drive module of the embodiment includes a voltage conversion circuit having a charge pump circuit that converts an input voltage into an output voltage, a current limiting circuit that switches the connection state between the input voltage and the charge pump circuit, and a current supply circuit that is connected to the charge pump circuit, has a rectifying function, and maintains the potential in the charge pump circuit at a predetermined voltage or higher, and a drive circuit that receives the voltage converted by the voltage conversion circuit and outputs a voltage that drives a motor. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a block diagram showing a voltage conversion circuit according to a first embodiment. [Figure 2] 1 is a diagram illustrating an example of a circuit configuration of a voltage conversion circuit according to a first embodiment. [Figure 3] 5 is a flowchart illustrating the operation of the current limit circuit and the current supply circuit of the voltage conversion circuit according to the first embodiment. [Figure 4] FIG. 10 is a block diagram showing a voltage conversion circuit according to a second embodiment. [Figure 5] FIG. 10 is a diagram illustrating an example of a circuit configuration of a voltage conversion circuit according to a third embodiment. [Figure 6] FIG. 10 is a circuit diagram of a voltage conversion circuit according to a comparative example. [Figure 7] 10 is a flowchart illustrating an operation of a voltage conversion circuit according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0008] The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as those in reality. Furthermore, even when the same part is shown, the dimensions and ratios may be different depending on the drawing.

[0009] Of the pair of opposing electrodes that a capacitor has, the electrode that is connected to the diode in the charge pump circuit is called the first electrode. The electrode of the capacitor opposite the first electrode and connected to the switching circuit is called the second electrode. When multiple capacitors are provided, each of the multiple capacitors has a first electrode and a second electrode.

[0010] In the present specification and the drawings, elements similar to those described above with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0011] (First embodiment) Fig. 1 is a block diagram of a voltage conversion circuit 100 according to a first embodiment. Fig. 2 shows an example of the circuit configuration of the voltage conversion circuit 100 according to the first embodiment. Fig. 3 is a flowchart showing an example of the operation of the voltage conversion circuit 100 according to the first embodiment.

[0012] As shown in FIG. 1 , a voltage conversion circuit 100 according to this embodiment includes a current limit circuit 110 connected to a power supply voltage Vcc, which is an input voltage; a current supply circuit 120 connected to the power supply voltage Vcc; and a charge pump circuit 130 connected to the current limit circuit 110 and the current supply circuit 120. The power supply voltage Vcc is a voltage output from a power supply 101, such as a battery, and the voltage conversion circuit 100 has a terminal T1 to which the power supply voltage Vcc is input. The charge pump circuit 130 outputs an output voltage Vout. A switching circuit 140 is connected between the power supply voltage Vcc and the charge pump circuit 130. Note that the current supply circuit 120 is connected to the same power supply voltage Vcc as the current limit circuit 110, for example, but is not limited to this. For example, a power supply may be provided to supply a potential to the current supply circuit 120. However, it is desirable that the potential supplied to the current supply circuit 120 be equal to the power supply voltage Vcc.

[0013] The output voltage Vout of the voltage conversion circuit 100 is connected to a drive circuit 500. The drive circuit 500 is, for example, a motor drive circuit that drives a motor. The drive circuit 500 is driven by the output voltage Vout converted by the voltage conversion circuit 100. The drive circuit 500 drives an output circuit 600. The output circuit 600 is, for example, a motor. The voltage conversion circuit 100 and the drive circuit 500 together are called a power supply circuit (semiconductor circuit) 700. The power supply circuit 700 supplies power to operate, for example, a motor. The power supply circuit 700 is connected to a power source 101, converts voltage, and drives the output circuit 600. The power supply circuit 700 is, for example, a motor drive module that drives a motor.

[0014] The current limit circuit 110 includes a current detection unit 112 and a first switch 114. When the current detection unit 112 detects a current greater than a predetermined value, the first switch 114 is turned off, thereby disabling the conduction state between the power supply voltage Vcc and the charge pump circuit 130. The first switch 114 can be automatically turned on after a predetermined time has elapsed, for example. The automatic turning on after a predetermined time is achieved by, for example, receiving a clock input and measuring a predetermined time. The clock may be a clock from a clock input unit CLK included in the switching circuit 140, which will be described later with reference to FIG. 2, or a clock input from outside the voltage conversion circuit 100. Alternatively, the first switch 114 may be turned on when the current value detected by the current detection unit 112 falls below a predetermined value.

[0015] The current supply circuit 120 has a rectifier unit 122. The current supply circuit 120 further has a second switch 124. When the second switch 124 is in the on state, the power supply voltage Vcc and the charge pump circuit 130 are connected via the rectifier unit 122. The forward direction of the rectifier unit 122 is the direction from the current supply circuit 120 to the charge pump circuit 130. The current supply circuit 120 has a rectifying function.

[0016] Although not shown in FIG. 1, the current supply circuit 120 may further include a voltage detection circuit for circuit protection in the event of a ground fault or the like occurring in the drive circuit 500 or the output circuit 600. The voltage detection circuit outputs a predetermined potential according to the input voltage. The voltage detection circuit is, for example, a voltage comparison circuit. The voltage comparison circuit compares voltages at two predetermined points (described below) and turns on the second switch 124 under predetermined conditions (described below), providing a path for current flowing from the power supply voltage Vcc to the charge pump circuit 130 via the rectification unit 122.

[0017] The charge pump circuit 130 has a plurality of diodes connected in series. The charge pump circuit 130 is, for example, an asynchronous charge pump circuit. The charge pump circuit 130 also has a plurality of capacitors. The voltage of the capacitors is controlled by a switching circuit 140. The switching circuit 140 periodically switches the connection state between the capacitors and the power supply voltage Vcc, which is the input voltage. By switching the connection state of the capacitors, the charge pump circuit 130 converts the power supply voltage Vcc into an output voltage Vout. The number of capacitors included in the charge pump circuit 130, i.e., the number of stages in the charge pump circuit 130, is an integer equal to or greater than three.

[0018] The switching circuit 140 supplies the charge pump circuit 130 with a voltage that changes over time between a high voltage and a low voltage. The switching circuit 140 includes a third switch 144 and a control unit 142 that periodically switches the third switch 144 between an on state and an off state. The control unit 142 steadily inputs a switching operation signal to the third switch 144. Here, "steadily" means that the operation continues regardless of the internal state of the voltage conversion circuit 100. Here, the internal state of the voltage conversion circuit 100 includes, for example, the on / off state of the first switch 114. The control unit 142, for example, inputs a clock to the third switch 144.

[0019] When the first switch 114 of the current limit circuit 110 is in the OFF state, the power supply voltage Vcc is not supplied to the charge pump circuit 130, and no boosting occurs. On the other hand, the connection state of the third switch 144 of the switching circuit 140 is switched without stopping the operation of the switching circuit 140. This is because when the first switch 114 of the current limit circuit 110 returns to the ON state, the boosting operation by the charge pump circuit 130 can be resumed more quickly. When the second switch 124 is in the ON state, the current supply circuit 120 supplies a predetermined voltage from the power supply voltage Vcc to the charge pump circuit 130 via the rectifier element D0.

[0020] Next, a description will be given with reference to Fig. 2. Fig. 2 shows an example of a circuit configuration.

[0021] The current limit circuit 110 includes a first resistor R1, a first amplifier AMP1, and a first transistor M1. The first amplifier AMP1 amplifies the potential difference across the first resistor R1 and detects the current flowing through the first resistor R1 from the known resistance value of the first resistor R1.

[0022] The first resistor R1 and the first amplifier AMP1 are an example of a current detection unit 112. The first transistor M1 is an example of a first switch 114 included in the current limit circuit 110, and is turned off when the current flowing through the first resistor R1 is greater than a predetermined magnitude. The first transistor M1 is, for example, a MOSFET. The first transistor M1 is, for example, a p-channel MOSFET, and is turned off when the gate voltage is greater than a predetermined threshold voltage. The output of the first amplifier AMP1 is connected to, for example, the gate electrode of the MOSFET.

[0023] The current limit circuit 110 amplifies the potential difference across the first resistor R1 and cuts off the current flowing from the power supply voltage Vcc to the charge pump circuit 130 when the voltage output from the first amplifier AMP1 is greater than the threshold voltage at which the first transistor M1 is turned off.

[0024] The current supply circuit 120 has a rectifying element D0. The rectifying element D0 is an example of the rectifying section 122. The current supply circuit 120 may further have a first comparator COMP1 and a second transistor M2. The second transistor M2 is an example of the second switch 124 included in the current supply circuit 120. The first comparator COMP1 is an example of a voltage detection circuit that detects the output voltage Vout. The voltage detection circuit includes at least the output voltage Vout as an input. The first comparator COMP1 is a voltage comparison circuit that detects the magnitude of the output voltage Vout by comparing the power supply voltage Vcc and the output voltage Vout.

[0025] The first comparator COMP1 compares the power supply voltage Vcc and the output voltage Vout, and switches the on and off states of the second transistor M2. For example, when Vout < Vcc, the first comparator COMP1 turns off the second transistor M2, and when Vout ≥ Vcc, the first comparator COMP1 turns on the second transistor M2. For example, the second transistor M2 is a p-channel MOSFET, and the first comparator COMP1 outputs a voltage higher than the threshold voltage of the second transistor M2 when Vout < Vcc, and outputs a voltage lower than the threshold voltage of the second transistor M2 when Vout ≥ Vcc.

[0026] Note that the first transistor M1 and the second transistor M2 may be n-channel MOSFETs, and the positive and negative of the output signals of the first amplifier AMP1 and the first comparator COMP1 and the offset may be adjusted as appropriate.

[0027] The rectifying element D0 has a rectifying action in the forward direction from the current supply circuit 120 to the charge pump circuit 130. The rectifying element D0 is, for example, a diode. It is desirable that the forward voltage Vf0 of the rectifying element D0 is equal to the forward voltages Vf of the diodes D1, D2, and D3 of the charge pump circuit 130 described later. The rectifying element D0 may be a diode with a forward voltage smaller than Vf, or may be a diode with a forward voltage larger than Vf. Instead of the diode, a MOSFET or a thyristor may be used as the rectifying element D0.

[0028] The charge pump circuit 130 includes a plurality of diodes D1, D2, and D3 connected in series, a first capacitor C1 connected to the cathode of the first diode D1, a second capacitor C2 connected to the cathode of the second diode D2, and a third capacitor C3 connected to the cathode of the third diode D3. The charge pump circuit 130 also includes a second resistor R2 connected in parallel with the third capacitor C3. The first diode D1, the second diode D2, and the third diode D3 each have the same forward voltage Vf.

[0029] The diode stages are numbered in the order from the power supply voltage Vcc to the output voltage Vout, as the first, second, third, initial, and subsequent stages. That is, the stages are counted in the direction of increasing voltage. The first diode D1 is also referred to as the initial-stage diode. The multiple diodes connected to the initial-stage diode, including diodes D2 and D3, are referred to as subsequent-stage diodes. The rectifier element D0 is connected between the subsequent-stage diodes. In other words, the rectifier element D0 is connected to at least one connection point between the subsequent-stage diodes. When the second transistor M2 of the current supply circuit 120 is on, the voltage drop at at least one connection point between the subsequent-stage diodes is maintained below the forward voltage Vf0 of the rectifier element D0, with respect to the power supply voltage Vcc.

[0030] A time-varying voltage is applied to the second electrodes of the first capacitor C1 and the second capacitor C2 on the switching circuit 140 side. The voltage is controlled by the switching circuit 140, which will be described later, to periodically alternate between high and low voltages. The voltages of the second electrodes of the first capacitor C1 and the second capacitor C2, for example, periodically switch between the power supply voltage Vcc and the ground voltage GND. The power supply voltage Vcc is applied to the second electrode of the third capacitor C3.

[0031] The charge pump circuit 130 has a second resistor R2 connected in parallel with the third capacitor C3. The voltages across the second resistor R2 are the power supply voltage Vcc and the output voltage Vout, respectively. When the first transistor M1 of the current limit circuit 110 is in the off state and the boost operation is paused, the output voltage Vout is maintained equal to the power supply voltage Vcc via the second resistor R2.

[0032] The switching circuit 140 has a clock input unit CLK and transistors M14, M24, M34, and M44. The clock input unit CLK is an example of a control unit 142, and the transistors M14, M24, M34, and M44 are an example of a third switch 144. The clock signal may be generated outside the switching circuit 140, or the switching circuit 140 may further include a clock generating unit. The clock input unit CLK inputs a clock signal to the transistors M14, M24, M34, and M44, which perform periodic switching. The transistors M14, M24, M34, and M44 are, for example, MOSFETs. The transistors M14 and M34 are, for example, p-channel MOSFETs, and the transistors M24 and M44 are, for example, n-channel MOSFETs.

[0033] An example of the operation of the charge pump circuit 130 and the switching circuit 140 will now be described.

[0034] When the clock input to the clock input section CLK of the switching circuit is in the L (Low) state, the transistor M14 is turned on and the transistor M24 is turned off. The second electrode of the first capacitor C1 on the switching circuit 140 side is connected to the power supply voltage Vcc. The power supply voltage Vcc is also connected to the gate electrodes of the transistors M34 and M44, so that the transistor M34 is turned off and the transistor M44 is turned on. The second electrode of the second capacitor C2 is grounded via the transistor M44.

[0035] On the other hand, when the clock is in an H (High) state, transistor M14 is turned off and transistor M24 is turned on. A first electrode of first capacitor C1 on the switching circuit 140 side is grounded. Furthermore, gate electrodes of transistors M34 and M44 are grounded, transistor M34 is turned on and transistor M44 is turned off. A second electrode of second capacitor C2 is connected to power supply voltage Vcc via transistor M34.

[0036] When the clock is in the H state, the second electrode of the first capacitor C1 is grounded, and the first electrode is at a voltage of Vcc-Vf, which is the power supply voltage Vcc minus the forward voltage Vf of the first diode D1. In other words, a charge corresponding to the potential difference Vcc-Vf is stored in the first capacitor C1. When the clock transitions to the L state, the voltage of the second electrode of the first capacitor C1 becomes Vcc, and the charge stored in the first capacitor C1 when the clock was in the H state causes the voltage of the first electrode to become 2Vcc-Vf. When the clock is in the L state, the second electrode of the second capacitor C2 is grounded, and the first electrode of the second capacitor C2 becomes 2Vcc-2Vf, which is 2Vcc-Vf minus the forward voltage of the second diode D2. A charge corresponding to the potential difference 2Vcc-2Vf is stored in the second capacitor C2.

[0037] In this way, by repeatedly inputting H and L clocks, the potential difference across the first capacitor C1 becomes Vcc - Vf, while the potential difference across the second capacitor C2 becomes 2Vcc - 2Vf. Taking into account the forward voltage Vf of the third diode D3, the potential difference across the third capacitor C3 becomes 2Vcc - 3Vf, and the output voltage Vout is boosted to 3Vcc - 3Vf = 3(Vcc - Vf). In this way, the boosted voltage is output as the output voltage Vout.

[0038] FIG. 3 is a flowchart showing an example of the operation of the voltage conversion circuit 100 according to this embodiment.

[0039] In step 501 of FIG. 3, when the voltage conversion circuit 100 is starting up or the like, the situation where a large current flows through the current limit circuit 110 is considered. Specifically, in the example shown in FIG. 2, a large current flows through the first resistor R1. When the voltage conversion circuit 100 is not performing a boosting operation and the first capacitor C1 is not charged, that is, when the voltage conversion circuit 100 is starting up or the like, the potential difference across the first resistor R1 becomes large and a large current may flow.

[0040] Next, in step 502, when the current value flowing through the current limit circuit 110 becomes larger than a predetermined value, the current detection unit 112 shown in FIG. 1 turns off the first switch 114. In the example of FIG. 2, due to the large potential difference across the first resistor R1, the gate voltage of the first transistor M1 increases via the first amplifier AMP1, and for example, the transistor M1, which is a p-channel MOSFET, turns off.

[0041] Subsequently, since the operation changes according to whether there is an abnormality in the output voltage Vout after step 503, it is determined whether there is an abnormality in the output voltage Vout. For example, the current supply circuit 120 detects the output voltage Vout. The output voltage Vout is maintained at or above Vcc while the voltage conversion circuit 100 is performing a normal boosting operation. Also, when the voltage conversion circuit 100 is not performing a boosting operation, the output voltage Vout is maintained at, for example, Vout = Vcc via the second resistor R2.

[0042] Therefore, the determination of whether the output voltage Vout is abnormal can be made by the first comparator COMP1 of the current supply circuit 120 comparing Vout and Vcc. For example, whether Vout < Vcc is satisfied may be used as a criterion for determination. It is not limited to Vout < Vcc, and Vout < Vcc - Vm may be used considering a predetermined margin Vm (≧0).

[0043] Situations where Vout < Vcc include, for example, a short circuit occurring in the drive circuit 500 or the output circuit 600 to which the output voltage Vout is supplied. It is possible for the output voltage Vout to be short-circuited to the ground voltage GND. When it is determined in step 503 that the output voltage Vout is abnormal, it is also conceivable that the cause of the large current flowing through the current limit circuit 110 in step 501 is the abnormality of the output voltage Vout.

[0044] First, the case where it is determined in step 503 that the output voltage Vout is abnormal will be described. In the subsequent step 504, the second switch 124 (the second transistor M2 in FIG. 2) of the current supply circuit 120 is turned off. In the example shown in FIG. 2, when the first comparator COMP1 determines in step 503 that the output voltage Vout is abnormal, the gate voltage of the second transistor M2 is controlled to turn off the second transistor M2.

[0045] By turning off the second switch 124 of the current supply circuit 120, the conduction state between the power supply voltage Vcc and the charge pump circuit 130 via the current supply circuit 120 is eliminated. Therefore, the flow of current from the power supply voltage Vcc to the charge pump circuit 130 via the current supply circuit 120 is suppressed. Since it is determined in step 503 that there is an abnormality in Vout, if there is a path for current from the power supply voltage Vcc to the charge pump circuit 130, there is a risk that a large current will flow through the rectifying element D0 of the current supply circuit 120 and cause overheating and breakdown. In step 504, by turning off the second switch 124, the breakdown of the rectifying element D0 of the current supply circuit 120 is prevented.

[0046] Next, in step 505, the abnormality in the output voltage Vout is resolved, and the current supply circuit 120 detects that the abnormality has been resolved. The Vout abnormality is resolved by solving problems such as short circuits in the drive circuit 500 or the output circuit 600. Then, the first comparator COMP1 of the current supply circuit 120 compares the output voltage Vout with the power supply voltage Vcc to detect that the output voltage Vout abnormality has been resolved. After the Vout abnormality is resolved in step 505, the state returns to normal, and for example, Vout = Vcc. Then, the process proceeds to the next step, step 506.

[0047] On the other hand, if the current supply circuit 120 does not detect an abnormality in Vout in step 503, the process proceeds directly to step 506.

[0048] In step 506, the second switch 124 (second transistor M2 in FIG. 2) of the current supply circuit 120 is turned on. First, when proceeding from step 505 to 506, Vout=Vcc is established, and the voltage comparison circuit (e.g., comparator COMP1) of the current supply circuit 120 turns on the second switch 124 (e.g., second transistor M2). Also, when proceeding directly from step 503 to 506, the second switch 124 of the current supply circuit 120 is maintained in the on state (the description of turning on the second switch 124 in step 506 in FIG. 3 includes maintaining the on state). In this way, the power supply voltage Vcc and the charge pump circuit 130 are electrically connected via the current supply circuit 120.

[0049] In step 507, a voltage is supplied from the power supply voltage Vcc to the charge pump circuit 130 via the rectifier unit 122 of the current supply circuit 120. In the example shown in Fig. 2, a voltage of Vcc-Vf0 is supplied to the cathode of the second diode D2 of the charge pump circuit 130 and the first electrode of the second capacitor C2 via the rectifier element D0 (a diode with a forward voltage Vf0).

[0050] By supplying a voltage to the cathode of the second diode D2, a decrease in the voltage of the cathode of the second diode D2 relative to the cathode of the first diode D1 is suppressed.

[0051] Next, in step 508, the current detection unit 112 of the current limit circuit 110 turns on the first switch 114 (the first transistor M1 in FIG. 2). That is, the current limit circuit 110 is restored. The current limit circuit 110 is set to automatically restore after a certain time has elapsed since the first switch 114 of the current limit circuit 110 was turned off in step 502, for example. Alternatively, the first switch 114 may be turned on when the magnitude of the current flowing through the current limit circuit 110 falls below a predetermined value. The first amplifier AMP1 of the current detection unit 112 detects the magnitude of the current flowing through the first resistor R1, thereby turning on the first transistor M1.

[0052] In step 508, the current limit circuit 110 is turned on after reducing the risk of breakdown of the diodes D1-D3 due to a large current flowing through the charge pump circuit 130. Also, in step 508, the switching circuit 140 continues to operate.

[0053] Therefore, in the next step 509, since the current limit circuit 110 is in the ON state, the charge pump circuit 130 resumes the boosting operation, and outputs a voltage obtained by boosting the power supply voltage Vcc as the output voltage Vout.

[0054] As shown in steps 501 to 509, a voltage is supplied to the charge pump circuit 130 via the current supply circuit 120 after a large current flows through the current limit circuit 110 and before the boost operation is resumed.

[0055] Next, a voltage conversion circuit 900 according to a comparative example will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is a diagram showing an example of the circuit configuration of the voltage conversion circuit 900. Fig. 7 is a flowchart showing an example of the operation of the voltage conversion circuit 900.

[0056] As shown in FIG. 6, the voltage conversion circuit 900 includes a power supply voltage Vcc, a current limit circuit 910, a charge pump circuit 920, and a switching circuit 930.

[0057] The current limit circuit 910 includes a resistor R91, an amplifier AMP91, and a transistor M90. When the value of the current flowing through the resistor R91 exceeds a predetermined value, the transistor M90 turns off, thereby canceling the conductive state between the power supply voltage Vcc and the charge pump circuit 920.

[0058] The charge pump circuit 920 includes a plurality of diodes D91, D92, and D93, a plurality of capacitors C91, C92, and C93, and a resistor R92. The voltages of the second electrodes of the capacitors C91, C92, and C93 of the charge pump circuit 920 on the switching circuit 930 side are controlled by the switching circuit 930. The voltages of the second electrodes of the capacitors C91 and C92 are periodically switched between the power supply voltage Vcc and the ground voltage GND. The voltage of the second electrode of the capacitor C93 is maintained at the power supply voltage Vcc, and the resistor R92 is connected in parallel with the capacitor C93.

[0059] The switching circuit 930 has a clock input CLK and transistors M91, M92, M93, and M94. The switching circuit 930 transitions between a connection state in which the transistors M91 and M94 are on and the transistors M92 and M93 are off, and a connection state in which the transistors M91 and M94 are off and the transistors M92 and M93 are on.

[0060] The voltage boosting operation by the charge pump circuit 920 and the switching circuit 930 is not significantly different from that of the voltage conversion circuit 100 according to the first embodiment, and therefore will not be described.

[0061] The operation of the voltage conversion circuit 900 according to the comparative example will be described with reference to Fig. 7. First, as shown in step 801, a large current flows instantaneously through resistor R91 of current limit circuit 910 when the voltage conversion circuit starts up, for example.

[0062] Therefore, in the next step 802, the transistor M90 is turned off and no voltage boosting is performed by the charge pump circuit 920. On the other hand, the clock input unit CLK continues to operate so that the voltage boosting operation can be immediately resumed when the current limit circuit 910 returns to the conductive state, and therefore the operation of the switching circuit 930 does not stop.

[0063] As the switching circuit 930 continues to operate, the transistors M91 and M94 are turned on and the transistors M92 and M93 are turned off as shown in step 803. In this way, the current path CP1 shown in FIG.

[0064] Current path CP1 is a path that runs from power supply voltage Vcc through transistor M91, capacitor C91, diode D92, capacitor C92, and transistor M94 to ground voltage GND. Current flows through current path CP1 in the direction shown in Figure 6 when the potential difference across diode D92 is greater than the forward voltage Vf.

[0065] For example, when no charge is stored in capacitor C91 (before the charge pump circuit 920 performs the boosting operation), the voltage at the anode of diode D92 is the power supply voltage Vcc, and when the voltage at the cathode of diode D92 is smaller than Vcc-Vf, a current flows through current path CP1.

[0066] Next, as shown in step 804, a current flows through the current path CP1, and the second electrode of the capacitor C91 is positively charged while the first electrode is negatively charged, so that the second electrode of the capacitor C91 has a higher voltage than the first electrode.

[0067] In the next step 805, the switching circuit 930 performs a switching operation, turning off the transistors M91 and M94 and turning on the transistors M92 and M93. The second electrode of the capacitor C91 is grounded. Because the first electrode of the capacitor C91 is negatively charged, the first electrode of the capacitor C91 has a negative voltage. This may cause a negative voltage to be generated in some places within the charge pump circuit 920.

[0068] The current limit circuit 910 and the charge pump circuit 920 are formed on the same chip, for example, and if a negative voltage occurs inside the charge pump circuit 920, there is a risk that a parasitic transistor or a parasitic thyristor inside the chip will turn on, which could cause a short circuit and impair the reliability of the voltage conversion circuit.

[0069] In the next step 806, the current limit circuit 910 is reset. It may be set to automatically reset after a certain time, or may be set to reset when the current value flowing through resistor R91 becomes smaller than a predetermined value.

[0070] In step 807, the current limit circuit 910 is restored, thereby restarting the boost operation of the charge pump circuit 920. The switching operation of the switching circuit 930 continues uninterrupted until the current limit circuit 910 is restored, and the boost operation by switching resumes as the current limit circuit 910 is restored.

[0071] As described with reference to Fig. 7, in the voltage conversion circuit 900 according to the comparative example, while the current limit circuit 910 is turned off to prevent a large current from flowing through the charge pump circuit 920, charging of the capacitor C91 occurs due to switching, and a negative voltage may occur inside the charge pump circuit 920. It is not possible to quickly resume the boost operation without stopping the operation of the switching circuit 930, while maintaining the reliability of the voltage conversion circuit. The voltage conversion circuit 900 according to the comparative example has been described above.

[0072] The voltage conversion circuit 100 according to this embodiment can improve the reliability of the voltage conversion circuit by suppressing voltage fluctuations in the charge pump circuit 130, specifically by suppressing the generation of negative voltage. On the other hand, by not stopping the operation of the switching circuit 140, the boost operation can be quickly resumed.

[0073] Suppressing the occurrence of negative voltage will be described again with reference to Fig. 2. Fig. 2 shows an example of a configuration that suppresses the occurrence of negative voltage when negative charges are charged to the first electrode of the first capacitor C1.

[0074] Consider a state in which the first transistor M1 of the current limit circuit 110 is turned off. The cathode of the second diode D2 is connected to the power supply voltage Vcc via the rectifier element D0 (forward voltage Vf0) of the current supply circuit 120, so the voltage of the cathode of the second diode D2 is maintained at least equal to or greater than Vcc-Vf0.

[0075] The second diode D2 passes a current in the forward direction only when a potential difference Vf occurs in the forward direction. Therefore, a current flows through the second diode D2 when the voltage at the anode of the second diode D2 is at least Vcc-Vf0+Vf. For example, when Vf0≦Vf, Vcc-Vf0+Vf≧Vcc, and a positive charge corresponding to the potential difference Vf-Vf0 (≧0) is stored in the first electrode of the first capacitor C1 (or no charge is stored). In other words, even if a current flows through the second diode D2, a negative charge is not stored in the first electrode of the first capacitor C1. Even when the switching circuit 140 operates and the potential of the second electrode of the first capacitor C1 switches, for example, from the power supply voltage Vcc to the ground voltage GND, the potential of the first electrode of the first capacitor C1 does not become negative.

[0076] According to the voltage conversion circuit 100 according to this embodiment, during the period when the first switch 114 in the current limit circuit 110 is in the off state, the forward voltage Vf0 of the rectifying element D0 can control the amount of charge stored in the first capacitor. For example, when Vf0 ≤ Vf, the voltage of the first electrode of the first capacitor C1 is positive with respect to the second electrode or has the same potential as the second electrode. Even when the switching circuit 140 performs a switching operation and the second electrode of the first capacitor C1 is grounded, no negative voltage occurs. That is, by setting Vf0 ≤ Vf, the generation of a negative voltage in the charge pump circuit 130 can be prevented.

[0077] When Vf0 = Vf, for example, in the connection state of the power supply voltage Vcc, the voltage of the first electrode of the first capacitor C1 ideally becomes zero with respect to the second electrode, suppressing the flow of current through the second diode D2 and suppressing the charging of negative charges to the first electrode of the first capacitor C1.

[0078] Furthermore, when Vf0 = Vf, the amount of current flowing through the rectifying element D0 can be reduced, and the conduction loss of the rectifying element D0 related to preventing the generation of a negative voltage can be suppressed. When Vf0 = Vf, current flows through the rectifying element D0 so that the cathode potential of the second diode D2 does not become less than Vcc - Vf. On the other hand, when Vf0 < Vf, when the cathode potential of the second diode D2 tries to become less than Vcc - Vf0 (> Vcc - Vf), current flows through the rectifying element D0 when the range of the cathode potential of the second diode D2 is wider than when Vf0 = Vf. In both cases, the generation of a negative voltage at the first electrode of the first capacitor C1 is prevented, but the amount of current flowing through the rectifying element D0 is smaller when Vf0 = Vf.

[0079] That is, when Vf0≦Vf, the generation of a negative voltage can be suppressed. However, when Vf0 = Vf, the condition for current to flow through the rectifying element D0 is further optimized to be the minimum necessary current amount to prevent the generation of a negative voltage, thereby reducing the conduction loss. For loss reduction, it is desirable that Vf0 = Vf. For example, it is desirable that the rectifying element D0 is the same diode as the second diode D2.

[0080] In addition, even when Vf0>Vf, during the period when the first switch 114 in the current limit circuit 110 is in the off state, the magnitude of the generated negative voltage can be suppressed and the reliability can be improved. The positive charge is lost from the first electrode of the first capacitor C1 (or the negative charge is charged) when the current flows through the second diode D2 and the charge moves. However, the cathode potential of the second diode D2 is maintained at Vcc - Vf0 or higher. Therefore, the positive charge is lost from the first electrode of the first capacitor C1 (or the negative charge is charged) when the anode potential of the second diode D2 is between Vcc - Vf0 + Vf or higher, and the value of Vf0 can be appropriately selected to control the amount of charge stored in the first electrode of the first capacitor C1. When Vf0>Vf, the voltage of the first electrode of the first capacitor C1 can also become a negative voltage, but the magnitude of the generated negative voltage can be controlled by appropriately selecting the value of Vf0. For example, compared with the voltage conversion circuit 900 according to the comparative example, the absolute value of the generated negative voltage can be reduced.

[0081] Also, when Vf0>Vf, no current flows through the rectifying element D0 until the cathode potential of the second diode D2 becomes less than Vcc - Vf0 (<Vcc - Vf). Therefore, compared with the case where Vf0≦Vf, the current flowing through the rectifying element D0 can be reduced to further reduce the conduction loss.

[0082] As described above, according to the voltage conversion circuit 100 according to the present embodiment, the negative voltage generated inside the charge pump circuit 130 can be suppressed by the rectifying unit 122 provided in the current supply circuit 120. According to the voltage conversion circuit 100 according to the present embodiment, by appropriately selecting the forward voltage Vf0 of the rectifying element D0, the negative voltage generated while the first switch 114 in the current limit circuit 110 is in the off state can be controlled. In order to suppress the generation of the negative voltage, it is desirable that the value of Vf0 satisfies Vf0≦Vf. Further, by setting Vf0 = Vf, the loss can be further reduced. On the other hand, even when Vf0>Vf, the magnitude of the generated negative voltage can be suppressed, and the current flowing through the rectifying element D0 can be reduced to reduce the loss.

[0083] Furthermore, according to the voltage conversion circuit 100 according to the present embodiment, when an abnormality occurs in the output voltage Vout, by turning off the second switch 124 of the current supply circuit 120, the rectifying element D0 and the diodes D1, D2, D3 of the charge pump circuit 130 can be prevented from being damaged, and the reliability of the circuit can be further enhanced.

[0084] The first comparator COMP1 of the current supply circuit 120, for example, when Vout<Vcc, turns off the transistor M2 which is an example of the second switch 124, so that no current flows through the rectifying element D0. When the output voltage Vout is short-circuited to GND or the like, it is possible to prevent a large current from flowing through the rectifying element D0 and causing damage.

[0085] In the above description, the first comparator COMP1 and the example of the second transistor have been described as the second switch 124 of the current supply circuit 120. However, instead of the first comparator COMP1, a current detection circuit may be used to control the on / off of the second transistor M2 of the current supply circuit 120. The current detection circuit includes, for example, a resistor and an amplifier, and turns off the second transistor M2 when a current of a predetermined magnitude or more flows. Even with a configuration having a current detection circuit, it is possible to prevent a large current from flowing through the rectifying element D0.

[0086] (Second embodiment) 4 is a diagram showing an example of the circuit configuration of a voltage conversion circuit 200 according to the second embodiment. Some of the points common to the voltage conversion circuit 100 according to the first embodiment shown in FIG. 2 will not be described.

[0087] In the voltage conversion circuit 200 according to this embodiment, the current supply circuit 120 includes a rectifier unit 122, and the forward voltage Vf0 of the rectifier unit 122 is variable. The forward direction of the rectifier unit 122 is from the power supply voltage Vcc to the charge pump circuit 130, and the rectifier unit 122 includes, for example, a MOSFET or a thyristor. The rectifier unit 122 has a gate electrode, and the forward voltage Vf0 can be adjusted by the voltage applied to the gate electrode. For example, the forward voltage Vf0 of the rectifier unit 122 can be made variable by the voltage applied to the gate electrode of a thyristor.

[0088] Furthermore, the voltage conversion circuit 200 according to this embodiment includes a rectification control circuit 150. The rectification control circuit 150 is connected to the gate electrode of the rectification unit 122, and controls the magnitude of the forward voltage Vf0 of the rectification unit 122.

[0089] The rectification control circuit 150 is further connected to the charge pump circuit 130. The rectification control circuit 150 may control the rectification unit 122 based on characteristics such as the forward voltage of the diodes (such as diodes D1-D3 in FIG. 2) inside the charge pump circuit 130. Specifically, when the forward voltage of the diodes inside the charge pump circuit 130 increases (decreases) due to, for example, aging, the forward voltage of the rectification unit 122 may be increased (decreased).

[0090] Alternatively, the rectification control circuit 150 may be connected to, for example, a part that outputs the output voltage Vout inside the charge pump circuit 130. The rectification control circuit 150 can detect an abnormality in the output voltage Vout and adjust the forward voltage Vf0 of the rectification unit 122. For example, when an abnormality in the output voltage Vout is detected, the forward voltage Vf0 of the rectification unit 122 is increased to suppress current flow through the rectification unit 122.

[0091] Although not shown in FIG. 4, the current supply circuit 120 may be provided with the first comparator COMP1 and the second resistor R2 shown in FIG. 2 so as to be connected to the second switch 124. This can suppress thermal breakdown of the rectifier unit 122 and further improve the reliability of the voltage conversion circuit 200.

[0092] According to the voltage conversion circuit 200 according to the present embodiment, since the rectifier unit 122 has the variable forward voltage Vf0, in consideration of suppressing the generation of the negative voltage in the charge pump circuit 130 and reducing the loss of the current flowing through the rectifier element D0, Vf0 can be determined appropriately at a desirable value.

[0093] As described in the first embodiment, when Vf0 < Vf, generation of the negative voltage in the charge pump circuit 130 can be prevented, but the current flowing through the rectifier element D0 may increase. On the other hand, when Vf0 > Vf, the current flowing through the rectifier element D0 becomes small, but generation of the negative voltage may occur.

[0094] The magnitude of the negative voltage that can be tolerated and the like change depending on the characteristics of the circuit, and the optimal value of Vf0 may also change. For example, Vf = Vf0 is desirable, but Vf = Vf0 is not necessarily always optimal. By controlling the forward voltage Vf0 by the rectification control circuit 150, the value of Vf0 can be optimized. Compared with the case of preparing many types of diodes, an optimal current supply circuit 120 can be provided efficiently.

[0095] Furthermore, the forward voltage Vf0 can be changed even after the voltage conversion circuit 200 starts operating. Therefore, an optimal Vf0 that may change depending on the operating environment of the voltage conversion circuit 200 can be set, the magnitude of the negative voltage can be controlled, and the loss can be reduced.

[0096] (Third Embodiment) FIG. 5 is a diagram showing an example of the circuit configuration of a voltage conversion circuit 300 according to the third embodiment. Some descriptions of the points common to the voltage conversion circuit 100 according to the first embodiment shown in FIG. 2 are omitted.

[0097] In the voltage conversion circuit 300 according to this embodiment, the charge pump circuit 130 has n diodes and n capacitors. A plurality of n diodes, from a first diode D1 to an n-th diode Dn, are connected in series. Between the cathode of each of the n diodes and the switching circuit 140, n capacitors C1 to Cn are connected.

[0098] The first diode D1 to the n-th diode Dn have, for example, a forward voltage Vf.

[0099] The current supply circuit 120 has n-2 rectifier elements D01, D02, ..., D0n-2. The n-2 rectifier elements do not necessarily have to be identical to one another. The current supply circuit 120 is connected between the power supply voltage Vcc and n-1 diodes (subsequent-stage diodes) of the charge pump circuit 130, excluding the first diode (initial-stage diode) D1. In other words, the current supply circuit 120 is connected between n-2 connection points between the n-1 diodes (subsequent-stage diodes) excluding the first diode (initial-stage diode) D1. For example, one rectifier element is provided for each of the n-2 connection points.

[0100] The n-2 rectifying elements D01, D02, . . . D0n-2 are, for example, diodes having a forward voltage Vf0.

[0101] A first comparator COMP1 and a second transistor M2 are provided between the n-1 rectifier elements D0 and the power supply voltage Vcc. In the example shown in Fig. 5, one second transistor M2 is provided, and it collectively controls the current flowing through the n-1 rectifier elements D0. However, the second switch 124 provided in the current supply circuit 120 is not limited to being a single one. A plurality of second transistors M2, which are an example of the second switch 124, may be provided to share and control the current flowing through the rectifier elements D01, D02, ... D0n-2.

[0102] Note that, since one or more rectifying elements D0 are provided in the current supply circuit 120, n≧3. That is, the charge pump circuit has three or more diodes and three or more capacitors.

[0103] The switching circuit 140 has 2(n-1) switches S1a, S1b, ..., Sn-1b as the third switch 144. Although the control unit 142 is not shown, it may further include, for example, a clock input unit connected to the 2(n-1) switches S1a, S1b, ..., Sn-1b.

[0104] Switches S1a and S1b are connected to the first capacitor C1. A state in which the switch S1a is on and the switch S1b is off, and a state in which the switch S1a is off and the switch S1b is on are alternately switched. Switches S2a and S2b are connected to the second capacitor C2. A state in which the switch S2a is on and the switch S2b is off, and a state in which the switch S2a is off and the switch S2b is on are alternately switched. Similarly, switches Sn-1a and Sn-1b are connected to the (n-1)th capacitor Cn-1. A state in which the switch Sn-1a is on and the switch Sn-1b is off, and a state in which the switch Sn-1a is off and the switch Sn-1b is on are alternately switched.

[0105] When switch S1a is on, switch S2b is on, switch S3a is on, switch S4b is on, etc., and switch a is on among the odd-numbered switches, and switch b is on among the even-numbered switches. Conversely, when switch S1a is off, switch b is on among the odd-numbered switches, and switch a is on among the even-numbered switches. Switches S1a, S2a, ..., Sn-1a are, for example, n-channel MOSFETs, and switches S1b, S2b, ..., Sn-1b are, for example, p-channel MOSFETs. Switches S1a, S2a, ..., Sn-1a are, for example, p-channel MOSFETs, and switches S1b, S2b, ..., Sn-1b are, for example, n-channel MOSFETs.

[0106] The switches are, for example, transistors. The switching circuit 140 may further have a clock input section, through which a clock is input to each transistor. An inverted signal is input to the odd-numbered switches S1a, S1b, S3a, S3b, etc. The on and off of the multiple switches is controlled as described above, for example.

[0107] Next, the operation of the voltage conversion circuit 300 will be described.

[0108] The voltage boosting operation by the first capacitor C1, the second capacitor C2, and the switches S1a, S1b, S2a, S2b, . . . is the same as in the first embodiment.

[0109] In the first embodiment, the cathode potential of the third diode D3 is used as the output voltage Vout, obtaining a voltage of 3 (Vcc-Vf). In contrast, in this embodiment, the cathode potential of the third diode D3 is further boosted to 4Vcc-3Vf by switching between switches S3a and S3b. Therefore, the cathode potential of the fourth diode D4 (not shown) becomes 4 (Vcc-Vf).

[0110] In this way, the voltage is boosted according to the number of diodes, and the cathode potential of the n-th diode Dn is n×(Vcc-Vf). That is, the voltage conversion circuit 300 according to this embodiment boosts the power supply voltage Vcc to the output voltage Vout=n(Vcc-Vf) using n diodes and n capacitors.

[0111] According to the voltage conversion circuit 300 of this embodiment, it is generally possible to suppress voltage fluctuations in an n-stage charge pump circuit, suppress the occurrence of negative voltage, and quickly resume the boost operation.

[0112] 5 shows current paths CP (CP1, CP2, ... CPn-2). Note that current paths CP1, CP3, CP4 ... CPn-3 are not shown. If a current flows through the current path CP when the first transistor M1 of the current limit circuit 110 is in the off state, there is a risk that a negative charge will be stored in the first electrode of the capacitor.

[0113] As in the first embodiment, the voltage of the cathode of the second diode D2 connected to the power supply voltage Vcc via the rectifier element D01 is kept at a predetermined value or higher to prevent current from flowing through the current path CP1 (the current path passing through the second diode D2 as shown in FIG. 6). This prevents negative charge from being charged to the first electrode of the first capacitor C1.

[0114] 5 again, for current path CP2, the voltage of the cathode of third diode D3, which is connected to power supply voltage Vcc via rectifier element D02 of current supply circuit 120, is maintained at a predetermined voltage or higher. This prevents current from flowing through current path CP2, thereby preventing negative charge from being charged to the first electrode of second capacitor C2.

[0115] Similarly, for the (n-2)th current path CPn-2, the voltage of the cathode of the (n-1)th diode Dn-1, which is connected to the power supply voltage Vcc via the rectifier element D0n-2 of the current supply circuit 120, is maintained at a predetermined voltage or higher. This prevents current from flowing through the current path CPn, thereby preventing negative charge from being charged to the first electrode of the (n-2)th capacitor Cn-2.

[0116] In this way, by suppressing the current flowing through the current paths CP1, CP2, ..., CPn, the charging of negative charges to the first electrodes of the capacitors C1, C2, ..., Cn-2 is suppressed. Generally, this suppresses the generation of negative voltage in a charge pump circuit having multiple capacitors.

[0117] According to the semiconductor device of at least one of the first to third embodiments described above, the switching circuit 140 continues to operate, enabling the charge pump circuit 130 to quickly resume the boost operation. Furthermore, it is possible to suppress voltage fluctuations in the charge pump circuit 130, specifically the occurrence of negative voltage, thereby improving reliability.

[0118] The switches described above are not limited to MOSFETs, but may include transistors such as IGBTs, SiN, and GaN.

[0119] The embodiments have been described above with reference to specific examples. However, the embodiments are not limited to these specific examples. In other words, designs that are appropriately modified by a person skilled in the art from these specific examples are also included within the scope of the embodiments as long as they have the characteristics of the embodiments. The elements, as well as their arrangement, materials, conditions, shapes, sizes, etc., of the above-mentioned specific examples are not limited to those exemplified and can be modified as appropriate.

[0120] Furthermore, the elements of each of the above-described embodiments can be combined to the extent technically possible, and combinations of these are also included within the scope of the embodiments as long as they include the features of the embodiments. In addition, within the scope of the concept of the embodiments, a person skilled in the art may conceive of various modifications and alterations, and it is understood that these modifications and alterations also fall within the scope of the embodiments.

[0121] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0122] 100, 200, 300, 900... Voltage conversion circuit 500···Drive circuit 600···Output circuit 101...Power supply 110, 910... Current limit circuit 120...Current supply circuit 130, 920... Charge pump circuit 140, 930... Switching circuit R1, R2, R91, R92...resistance M1, M2, M14, M24, M34, M44, M90, M91, M92, M93, M94... Transistors COMP1, COMP2, COMP91... Comparators D0: Rectifier element D1, D2, D3, D91, D92, D93...diodes C1, C2, C3, C91, C92, C93... Capacitors CP1, CP2, CPn...current paths

Claims

1. a current limiting circuit having a first switch; a charge pump circuit having a first-stage diode connected to the current limit circuit and two or more subsequent-stage diodes connected in series with the first-stage diode; a current supply circuit connected between the diodes in the subsequent stage of the charge pump circuit and having a rectifier whose forward direction is toward the charge pump circuit; A voltage conversion circuit having:

2. a charge pump circuit that converts an input voltage into an output voltage; a current limit circuit that switches a connection state between the input voltage and the charge pump circuit; a current supply circuit connected to the charge pump circuit, having a rectifying function, and maintaining a potential in the charge pump circuit at a predetermined voltage or higher; A voltage conversion circuit having:

3. the charge pump circuit further includes a plurality of capacitors respectively connected between the first-stage diode and the second-stage diode.

2. The voltage conversion circuit according to claim 1.

4. a switching circuit connected to the charge pump circuit and supplying a time-varying potential to the charge pump circuit; 4. The voltage conversion circuit according to claim 3.

5. The switching circuit includes a plurality of switches and a control unit that steadily switches the connection states of the switches.

5. The voltage conversion circuit according to claim 4.

6. the current supply circuit further includes a second switch connected in series to the rectifier unit.

6. The voltage conversion circuit according to claim 5.

7. the current supply circuit further includes a voltage detection circuit having an input that receives the output voltage Vout of the charge pump circuit; the output of the voltage detection circuit is connected to the second switch; 7. The voltage conversion circuit according to claim 6.

8. a forward voltage Vf0 of the rectifier unit satisfies a relationship of Vf0≦Vf with a forward voltage Vf of the diode of the plurality of diodes of the charge pump circuit, the cathode of which is connected to the rectifier unit; 2. The voltage conversion circuit according to claim 1.

9. the rectification unit is the same diode as a diode in the charge pump circuit, the cathode of which is connected to the rectification unit; 2. The voltage conversion circuit according to claim 1.

10. the first switch is a transistor; the current limit circuit further includes a first resistor and a first amplifier that receives a potential difference across the first resistor as an input and outputs the potential difference to a gate terminal of the transistor.

8. The voltage conversion circuit according to claim 7.

11. the rectifier unit has a variable forward voltage; Further, a rectification control circuit is provided to control the magnitude of the forward voltage of the rectification unit.

2. The voltage conversion circuit according to claim 1.

12. A voltage conversion circuit according to any one of claims 1 to 11; a drive circuit to which the voltage converted by the voltage conversion circuit is input; A semiconductor circuit having:

13. a charge pump circuit that converts an input voltage into an output voltage; a current limit circuit that switches a connection state between the input voltage and the charge pump circuit; a current supply circuit connected to the charge pump circuit, having a rectifying function, and maintaining a potential in the charge pump circuit at a predetermined voltage or higher; a voltage conversion circuit having a drive circuit that receives the voltage converted by the voltage conversion circuit and outputs a voltage for driving a motor; A motor drive module having

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