Motor driver circuit and electronic apparatus using the same

Abstract

To provide a motor driver circuit equipped with a reference current source that is hardly affected by switching noise.SOLUTION: An external setting resistor RSET is connected to a current setting pin ISET. A first transistor M11 has a first electrode connected to the current setting pin ISET. An operational amplifier OA11 receives a reference voltage VREF at a first input (+), receives a voltage VFB of the current setting pin ISET at a second input (-), and an output is connected to a control electrode (a gate) of the first transistor M11. A current mirror circuit CM11 turns back a first current I1 flowing through the first transistor M11. A first resistor R11 is connected to an output node of the current mirror circuit CM11. A low pass filter 510 receives a first voltage signal V1, which is a voltage drop across the first resistor R11. A voltage / current converter 520 converts a second voltage signal V2 output from the low pass filter 510 into a reference current IREF.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a motor driver circuit.

Background Art

[0002] Many semiconductor integrated circuits include a reference current source that generates a reference current. The reference current source may be configured such that the amount of the reference current can be freely changed by a designer of a system application including the semiconductor integrated circuit. Specifically, a semiconductor integrated circuit is provided with a pin for current setting, and an external resistor can be connected to this pin for current setting. The reference current source of the semiconductor integrated circuit applies a reference voltage to the external resistor and generates a reference current having an amount corresponding to the resistance value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] The inventor has come to recognize the following problems when integrating a reference current source whose current amount can be set by an external resistor into a motor driver circuit.

[0005] A motor driver circuit includes an inverter as an output stage. The inverter generates switching noise associated with switching. Since the pin for current setting has a high impedance, it is easily affected by noise. When the switching noise is input to the pin for current setting, the amount of the reference current changes.

[0006] [Summary] The present disclosure has been made in view of such problems, and an exemplary object of one of its aspects is to provide a motor driver circuit including a reference current source that is hardly affected by switching noise.

[0007] A motor driver circuit according to an aspect of the present disclosure includes a current setting pin to which an external setting resistor is to be connected, and a reference current source that generates a reference current having a current amount determined by the setting resistor. The reference current source includes a first transistor having a first electrode connected to the current setting pin, an operational amplifier that receives a reference voltage at a first input, receives a voltage of the current setting pin at a second input, and has an output connected to a control electrode of the first transistor, a current mirror circuit that folds back a first current flowing through the first transistor, a first resistor connected to an output node of the current mirror circuit, a low-pass filter that receives a first voltage signal that is a voltage drop of the first resistor, and a voltage / current converter that converts a second voltage signal output from the low-pass filter into a reference current.

[0008] In addition, combinations of the above components arbitrarily, and those in which the components and expressions of the present disclosure are mutually replaced among methods, apparatuses, systems, etc. are also effective as aspects of the present invention.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

[0010] [Detailed Description] (Overview of the Embodiment) An overview of some exemplary embodiments of the present disclosure is described. This overview is for the purpose of providing a basic understanding of the embodiments as a prelude to the detailed description that follows, and simplifies and describes some concepts of one or more embodiments. It is not intended to limit the scope of the invention or the disclosure. For convenience, "one embodiment" may be used to refer to one embodiment (example or variation) or a plurality of embodiments (examples or variations) disclosed herein.

[0011] This overview is not an exhaustive overview of all possible embodiments, nor is it intended to identify important elements of all embodiments or to delineate the scope of some or all aspects. Its sole purpose is to present in a simplified form some concepts of one or more embodiments as a prelude to the more detailed description presented later.

[0012] A motor driver circuit according to one embodiment includes a current setting pin to which an external setting resistor is to be connected, and a reference current source that generates a reference current having a current amount determined by the setting resistor. The reference current source includes a first transistor having a first electrode connected to the current setting pin, an operational amplifier that receives a reference voltage at a first input, receives the voltage of the current setting pin at a second input, and has an output connected to the control electrode of the first transistor, a current mirror circuit that folds back a first current flowing through the first transistor, a first resistor connected to the output node of the current mirror circuit, a low-pass filter that receives a first voltage signal that is the voltage drop of the first resistor, and a voltage / current converter that converts the second voltage signal output by the low-pass filter into a reference current.

[0013] The first transistor and the operational amplifier, together with the external setting resistor, form a voltage / current converter (V / I converter). When the resistance value of the setting resistor is R SET and the reference voltage is V REF , the current amount of the first current I1 flowing through the first transistor is represented by the following equation. I1 = V REF / R SET If switching noise is mixed into the current setting pin, the first current I1 fluctuates, and the first voltage signal, which is the voltage of the first resistor, fluctuates. This fluctuation is removed by a low-pass filter, and the second voltage signal with the noise removed is converted into a reference current. According to this configuration, a reference current that is less affected by switching noise can be generated.

[0014] In one embodiment, the cut-off frequency of the low-pass filter may be 10 kHz or less. In a motor driver, the switching frequency is often set higher than the audible band. Therefore, if the cut-off frequency is set to 10 kHz or less, the influence of switching noise can be preferably removed.

[0015] In one embodiment, the cut-off frequency of the low-pass filter may be 1 / 4 or less of the switching frequency of the motor driver circuit.

[0016] In one embodiment, the first resistor and the second resistor may be formed by pairing on a semiconductor substrate. Thereby, the relative accuracy of the resistance values of the first resistor and the second resistor can be improved, and the influence of process variations and temperature changes on the reference current can be reduced.

[0017] In one embodiment, the low-pass filter may be an RC filter.

[0018] In one embodiment, the low-pass filter may be an LC filter.

[0019] In one embodiment, the low-pass filter may be an LR filter.

[0020] In one embodiment, the low-pass filter may be an active filter.

[0021] In one embodiment, the motor driver circuit may include a capacitor charged by a reference current, and further include a timer circuit that measures a time inversely proportional to the reference current. Thereby, fluctuations in the time measured by the timer circuit can be suppressed.

[0022] In one embodiment, the motor driver circuit may further include a high-side driver that drives a high-side transistor and a low-side driver that drives a low-side transistor. The motor driver circuit may control the dead time between the high-side transistor and the low-side transistor using a timer circuit. Thereby, fluctuations in the dead time can be suppressed.

[0023] In one embodiment, the motor driver circuit may further include a high-side driver that drives a high-side transistor with a constant current and a low-side driver that drives a low-side transistor with a constant current. The drive currents of the high-side driver and the low-side driver may be according to the reference current. Thereby, fluctuations in the turn-on time and turn-off time of the high-side transistor and the low-side transistor can be suppressed.

[0024] In one embodiment, the motor driver circuit may be integrally integrated on a single semiconductor substrate. "Integrally integrated" includes cases where all of the circuit components are formed on the semiconductor substrate and cases where the main circuit components are integrally integrated, and some resistors, capacitors, etc. may be provided outside the semiconductor substrate for adjusting circuit constants. By integrating the circuit on a single chip, the circuit area can be reduced and the characteristics of the circuit elements can be kept uniform.

[0025] An electronic device according to one embodiment may include a motor and a motor driver circuit that drives the motor.

[0026] (Embodiment) Hereinafter, preferred embodiments will be described with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. Also, the embodiments are illustrative and not restrictive of the invention, and not all of the features and combinations thereof described in the embodiments are necessarily essential to the invention.

[0027] In this specification, the phrase "member A is in a state of being connected to member B" includes not only the case where member A and member B are physically directly connected, but also the case where member A and member B are indirectly connected via other members without substantially affecting their electrical connection states or impairing the functions and effects achieved by their connection.

[0028] Similarly, the phrase "member C is in a state of being provided between member A and member B" includes not only the case where member A and member C, or member B and member C are directly connected, but also the case where they are indirectly connected via other members without substantially affecting their electrical connection states or impairing the functions and effects achieved by their connection.

[0029] FIG. 1 is a circuit diagram of a motor driver circuit 200 according to an embodiment. The motor driver circuit 200, together with a bridge circuit 110, constitutes a motor driving device 300. The motor driving device 300 drives a three-phase motor 302, which is a load, and controls its rotational state.

[0030] The bridge circuit 110 is a three-phase inverter and has legs for the U-phase, V-phase, and W-phase. Each phase leg has an upper arm and a lower arm. An input voltage V is supplied to a power line 102, and a ground line 104 is grounded. The upper arm includes a high-side transistor MH, which is a power transistor, and a flywheel diode. The lower arm includes a low-side transistor ML and a flywheel diode. IN is supplied, and the ground line 104 is grounded. The upper arm includes a high-side transistor MH, which is a power transistor, and a flywheel diode. The lower arm includes a low-side transistor ML and a flywheel diode.

[0031] The motor driver circuit 200 includes a control circuit 210, high-side driver circuits 220U to 220W, low-side driver circuits 260U to 260W, and a reference current source 500. The control circuit 210 generates control signals indicating the states of the six arms constituting the bridge circuit 110 based on the state of the three-phase motor 302 which is the load.

[0032] The motor driver circuit 200 has a current setting pin ISET to which an external setting resistor R SET is to be connected.

[0033] The reference current source 500 generates a reference current I SET having a current amount determined by the setting resistor R REF . The reference current I REF is copied and supplied to each circuit block constituting the motor driver circuit 200.

[0034] FIG. 2 is a circuit diagram of the reference current source 500 according to the embodiment. The reference current source 500 includes a first transistor M11, a first operational amplifier OA11, a current mirror circuit CM11, a first resistor R11, a low-pass filter 510, and a V / I converter 520.

[0035] The first transistor M11 is an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and a first electrode (source) thereof is connected to the current setting pin ISET. The first operational amplifier OA11 receives a reference voltage V REF at a first input (non-inverting input +), and receives a voltage V FB of the current setting pin ISET at a second input (inverting input -). The output of the first operational amplifier OA11 is connected to a control electrode (gate) of the first transistor M11. When an imaginary short (V FB = V REF ) holds in the steady state, a first current I1 flowing through the first transistor M11 is represented by Equation (1). I1 = V REF / R SET ...(1)

[0036] The current mirror circuit CM11 folds back the first current I1 flowing through the first transistor M1. The mirror ratio α of the current mirror circuit CM11 may be 1 or may be greater than 1. The second current I2 output from the current mirror circuit CM11 is represented by Equation (2). I2 = α·I1 = αV REF / R SET …(2)

[0037] The first resistor R11 is connected between the output node of the current mirror circuit CM11 and the ground. When the second current I2 output from the current mirror circuit CM11 flows through the first resistor R11, a voltage drop occurs across the first resistor R11. The first voltage signal V1, which is the voltage drop across the first resistor R11, is input to the low-pass filter 510. V1 = I2 × R11 = α·R11 / R SET ×V REF …(3)

[0038] The low-pass filter 510 receives the first voltage signal V1, removes frequency components higher than the cut-off frequency fc, and generates a second voltage signal V2. The cut-off frequency of the low-pass filter 510 may be 10 kHz or less. In a motor driver, the switching frequency f SW is often set higher than the audible band. Therefore, if the cut-off frequency is set to 10 kHz or less, the influence of switching noise can be preferably removed. From another perspective, the cut-off frequency fc of the low-pass filter 510 may be 1 / 4 or less of the switching frequency f SW of the motor driver circuit. Specifically, the cut-off frequency fc may be set to about 5 kHz. The low-pass filter 510 is, for example, an RC filter and includes a resistor R21 and a capacitor C21.

[0039] The V / I converter 520 converts the second voltage signal V2 output by the low-pass filter 510 into a reference current I REF .

[0040] The V / I converter 520 includes a second transistor M12, a second resistor R12, and a second operational amplifier OA12. The first terminal of the second resistor R12 is grounded. The second transistor M12 is an N-channel MOSFET, and its first electrode (source) is connected to the second terminal of the second resistor R12. The second operational amplifier OA12 receives a second voltage signal V2 at its first input (non-inverting input +) and receives the voltage at the second terminal of the second resistor R12 at its second input (inverting input -). The output of the second operational amplifier OA12 is connected to the control electrode (gate) of the second transistor M12.

[0041] The reference current I flowing through the second transistor M12 REF is represented by Equation (4). I REF = V2 / R12 …(4)

[0042] Assuming that V1 = V2 holds in the steady state, Equation (5) is obtained. I REF = α · (R11 / R12) × 1 / R SET × V REF …(5) The first resistor R11 and the second resistor R12 may be formed by pairing on a semiconductor substrate. Thereby, the relative error in the resistance values of the first resistor R11 and the second resistor R12 is reduced, and the term (R11 / R12) becomes less susceptible to process variations and temperature, and the process variations and temperature changes affecting the reference current I REF can be reduced.

[0043] The above is the configuration of the reference current source 500.

[0044] Figure 3 is a diagram for explaining the operation of the reference current source 500 in Figure 2. Before time t0, it is in the steady state, and an imaginary short circuit, that is, V REF = V FB holds. At this time, the first current I1 represented by Equation (1) flows, and the reference current I REF represented by Equation (5) is generated.

[0045] Noise occurs at time t0 and is mixed into the current setting pin ISET. Due to this noise, the voltage V FB of the current setting pin ISET, that is, the source voltage of the first transistor M11, fluctuates. Due to the noise, when the source voltage V FB becomes higher than the reference voltage V REF , the first operational amplifier OA11 decreases the gate voltage V FB of the first transistor M11 so that the source voltage V REF approaches the reference voltage V FB , that is, so that the source voltage V G becomes lower. As a result, the gate-source voltage V GS of the first transistor M11 becomes smaller, the first current I1 decreases, and the second current I2 also decreases. In this example, it is assumed that the mirror ratio of the current mirror circuit CM11 is 1.

[0046] Due to the noise, when the source voltage V FB becomes lower than the reference voltage V REF , the first operational amplifier OA11 increases the gate voltage V FB of the first transistor M11 so that the source voltage V REF approaches the reference voltage V FB , that is, so that the source voltage V G becomes higher. As a result, the gate-source voltage V GS of the first transistor M11 becomes larger, the first current I1 increases, and the second current I2 also increases. Thus, the first current I1 and the second current I2 are greatly affected by the noise and fluctuate.

[0047] When the second current I2 fluctuates, the first voltage signal V1, which is the voltage drop across the first resistor R11, fluctuates. Since the cut-off frequency fc of the low-pass filter 510 is set lower than the frequency of the noise, the fluctuation of the first voltage signal V1 is removed by the low-pass filter 510. Therefore, the second voltage signal V2, which is the output of the low-pass filter 510, hardly fluctuates and becomes a constant voltage. As a result, the reference current I REF represented by Equation (5) can be made constant without being affected by the noise.

[0048] The present disclosure is understood as a block diagram or a circuit diagram in FIG. 2, or extends to various devices and methods derived from the above description, and is not limited to a specific configuration. Hereinafter, in order to help understand the essence and operation of the present disclosure and the present invention, and to clarify them, rather than narrowing the scope of the present disclosure, more specific configuration examples, embodiments, and modification examples will be described.

[0049] FIG. 4 is a circuit diagram showing a configuration example of the low-pass filter 510. The low-pass filter 510 can be configured by an LC filter and may include an inductor L21 and a capacitor C22.

[0050] FIG. 5 is a circuit diagram showing another configuration example of the low-pass filter 510. The low-pass filter 510 can be configured by an LR filter and may include a resistor R22 and an inductor L22.

[0051] The low-pass filter 510 may be another type of passive filter such as a π-type filter, or may be an active filter.

[0052] FIG. 6 is a circuit diagram showing yet another configuration example of the low-pass filter 510. The low-pass filter 510 may be configured by an active filter and may include an operational amplifier OA21, resistors R23, R24, R25, and a capacitor C23.

[0053] Subsequently, the use of the reference current I in the motor driver circuit 200 will be described. REF of will be described.

[0054] FIG. 7 is a circuit diagram of a motor driver circuit 200A according to an embodiment. The motor driver circuit 200A includes a high-side sensor 202, a low-side sensor 204, a control circuit 210, a timer circuit 230, a high-side driver circuit 220, a low-side driver circuit 260, and a reference current source 500. Only the configuration for one phase is shown in FIG. 7.

[0055] The motor driver circuit 200A can switch between a high output state (V OUT =V IN ) in which the high-side transistor MH is on and the low-side transistor ML is off, and a low output state (V OUT = 0V) in which the high-side transistor MH is off and the low-side transistor ML is on.

[0056] During the transition between the high output state and the low output state, if the high-side transistor MH and the low-side transistor ML are turned on simultaneously, a through current will flow, which is not preferable. Therefore, dead-time control is implemented in the motor driver circuit 200A to prevent the simultaneous turn-on of the high-side transistor MH and the low-side transistor ML.

[0057] The dead-time control will be described. When the control signal CTRL instructs a transition from the high output state to the low output state, the control circuit 210 controls the high-side driver circuit 220 so that the high-side transistor MH turns off. The high-side off sensor 202 monitors the gate-source voltage of the high-side transistor MH and asserts the off detection signal S OFFH when it detects the turn-off of the high-side transistor MH. In response to the assertion of the off detection signal S OFFH , the control circuit 210 operates the timer circuit 230. The timer circuit 230 returns a time-up signal TU to the control circuit 210 after the elapse of the dead time T DEAD . In response to the time-up signal TU, the control circuit 210 controls the low-side driver circuit 260 so that the low-side transistor ML turns on.

[0058] Also, when the control signal CTRL instructs a transition from the low output state to the high output state, the control circuit 210 controls the low-side driver circuit 260 so that the low-side transistor ML turns off. The low-side off sensor 204 monitors the gate-source voltage of the low-side transistor ML and asserts the off detection signal SOFFL asserts. The control circuit 210 operates the timer circuit 230 in response to the assertion of the off detection signal S OFFL . The timer circuit 230 returns a time-up signal TU to the control circuit 210 after the elapse of the dead time T DEAD . In response to the time-up signal TU, the control circuit 210 controls the high-side driver circuit 220 so that the high-side transistor MH turns on.

[0059] The timer circuit 230 includes a capacitor C31, a current source CS31, a comparator COMP31, and a discharge switch SW31. The current source CS31 generates a charging current I REF proportional to the reference current I C generated by the reference current source 500 to charge the capacitor C31. The discharge switch SW31 is on while the timer circuit 230 is stopped, and the charge of the capacitor C31 is reset. The control circuit 210 turns off the discharge switch SW31 and starts measuring time. When the discharge switch SW31 turns off, the capacitor C31 is charged by the current I C , and the voltage V C31 of the capacitor C31 rises at a constant slope. Then, when the voltage V C31 reaches the threshold voltage V TH , the time-up signal TU is asserted. The dead time T DEAD measured by this timer circuit 230 is represented by Equation (6). T DEAD = C31 × V TH / I C …(6)

[0060] The timer circuit 230 measures the dead time T DEAD during the switching of the bridge circuit 110, which can be said to be the situation where switching noise is most likely to occur. As described above, since the reference current I REF generated by the reference current source 500 is less affected by switching noise, the charging current I C is also stable without being affected by switching noise. Therefore, the dead time T DEADThe fluctuations can also be suppressed.

[0061] As for the driving formats of the high-side driver circuit 220 and the low-side driver circuit 260 (hereinafter collectively referred to as the gate driver), a voltage driving format and a constant current driving format are known. When using the above-mentioned reference current source 500, it brings great advantages when the gate driver is configured in a constant current driving format.

[0062] When the gate driver in the constant current driving format turns on the power transistor to be driven, a constant driving current (turn-on current) I ON is sourced to the gate of the power transistor, and the gate voltage is increased at a constant slope. Also, when turning off the power transistor, a constant driving current (turn-off current) I OFF is sunk from the gate of the power transistor, and the gate voltage is decreased at a constant slope. The gate driver may change the amounts of the driving currents I ON , I OFF in two steps or three or more steps over time.

[0063] The gate driver may include a current source CS1 that generates the driving current I ON and a current source CS2 that generates the driving current I OFF . Each of the current sources CS1 and CS2 receives the reference current I REF generated by the reference current source 500, and can be configured to amplify the reference current I REF using a current mirror circuit to generate a driving current.

[0064] The high-side driver circuit 220 and the low-side driver circuit 260 generate a driving current during the switching of the bridge circuit 110, which can be said to be the situation where switching noise is most likely to occur. As described above, the reference current I REFSince it is less affected by switching noise, the drive current is also stable without being affected by switching noise. Variations in the turn-on time, turn-off time of the high-side transistor MH, and the turn-on time and turn-off time of the low-side transistor ML can be suppressed.

[0065] Next, the applications of the motor drive device 300 will be described. The motor drive device 300 can be used for controlling the spindle motor of a hard disk and for controlling the lens drive motor of an imaging device. Alternatively, it can be used for driving the head drive motor or the paper feed motor of a printer. Alternatively, the motor drive device 300 can be used for driving motors in electric vehicles, hybrid vehicles, etc.

[0066] The embodiments are illustrative, and it is understood by those skilled in the art that various modifications are possible for the combination of each component and each processing process, and such modifications are also within the scope of the present disclosure or the present invention. Hereinafter, such modifications will be described.

[0067] (Modification 1) In FIG. 2, the first transistor M11 may be a P-channel MOSFET. In this case, the reference voltage V REF may be input to the inverting input terminal of the first operational amplifier OA11, and the voltage VFB may be input to the non-inverting input terminal. The same applies to the second transistor M12. Also, the first transistor M11, the second transistor M12, and other transistors may be constituted by bipolar transistors.

[0068] (Modification 2) The reference current source 500 may further include a built-in resistor R INT between the source of the first transistor M11 and the current setting terminal ISET. In this case, the first current I1 flowing through the first transistor M11 is represented by Equation (7). I1 = V REF / (R INT + R SET ) …(7) In this format, when the user of the motor driver circuit 200 wants to use it in the state of I1 = V REF / R INT it is possible to adopt a configuration in which an external current setting resistor R SET is omitted and shorted to ground, and the cost can be reduced.

[0069] (Modification Example 3) In the embodiment, the bridge circuit 110 is composed of discrete components. However, the bridge circuit 110 may be integrated into the motor driver circuit 200, not limited to this.

[0070] (Modification Example 4) The power transistors constituting the bridge circuit 110 may be bipolar transistors or IGBTs (Insulated Gate Bipolar Transistors).

[0071] (Modification Example 5) In the embodiment, the motor driver circuit 200 including the reference current source 500 has been described. However, the present disclosure is not limited thereto, and is widely applicable to semiconductor integrated circuits including switching circuits such as a controller circuit of a DC / DC converter. For example, in the controller circuit of a DC / DC converter, dead time control is often introduced. Therefore, if the reference current given to the timer circuit for dead time is generated by the reference current source 500 according to the embodiment, fluctuations in the dead time can be suppressed.

[0072] The embodiments described using specific terms only show the principles and applications of the present invention. In the embodiments, many modifications and arrangement changes are allowed without departing from the idea of the present invention defined in the claims.

[0073] (Supplementary Note) The following techniques are disclosed in this specification.

[0074] (Item 1) A current setting pin to which an external setting resistor is to be connected, and A reference current source that generates a reference current having a current value determined by the set resistance, comprising: The reference current source includes: A first transistor having a first electrode connected to the current setting pin; An operational amplifier that receives a reference voltage at a first input, receives the voltage of the current setting pin at a second input, and has an output connected to the control electrode of the first transistor; A current mirror circuit that folds back a first current flowing through the first transistor; A first resistor connected to the output node of the current mirror circuit; A low-pass filter that receives a first voltage signal which is the voltage drop of the first resistor; A voltage / current converter that converts the second voltage signal output by the low-pass filter into the reference current. A motor driver circuit including the above components.

[0075] (Item 2) The motor driver circuit according to Item 1, wherein the cut-off frequency of the low-pass filter is 10 kHz or less.

[0076] (Item 3) The motor driver circuit according to Item 1 or 2, wherein the cut-off frequency of the low-pass filter is 1 / 4 or less of the switching frequency of the motor driver circuit.

[0077] (Item 4) The motor driver circuit according to any one of Items 1 to 3, wherein the first resistor and the second resistor are formed in a paired manner on a semiconductor substrate.

[0078] (Item 5) The motor driver circuit according to any one of Items 1 to 4, wherein the low-pass filter is an RC filter.

[0079] (Item 6) The motor driver circuit according to any one of Items 1 to 4, wherein the low-pass filter is an LC filter.

[0080] (Item 7) The low-pass filter is an LR filter, and the motor driver circuit according to any one of Items 1 to 4.

[0081] (Item 8) The low-pass filter is an active filter, and the motor driver circuit according to any one of Items 1 to 4.

[0082] (Item 9) The motor driver circuit according to any one of Items 1 to 8, further comprising a capacitor charged by the reference current and a timer circuit for measuring a time inversely proportional to the reference current.

[0083] (Item 10) A high-side driver for driving a high-side transistor, A low-side driver for driving a low-side transistor, further comprising The motor driver circuit according to Item 9, wherein a dead time between the high-side transistor and the low-side transistor is controlled using the timer circuit.

[0084] (Item 11) A high-side driver for driving a high-side transistor with a constant current, A low-side driver for driving a low-side transistor with a constant current, further comprising The motor driver circuit according to any one of Items 1 to 10, wherein drive currents of the high-side driver and the low-side driver are in accordance with the reference current.

[0085] (Item 12) The motor driver circuit according to any one of Claims 1 to 11, wherein the reference current source further includes an internal resistance connected between the first electrode of the first transistor and the current setting pin.

[0086] (Item 13) The motor driver circuit according to any one of Items 1 to 12, integrally integrated on a single semiconductor substrate.

[0087] (Item 14) A motor, The motor driver circuit according to Item 13 for driving the motor, An electronic device comprising the same.

Description of Reference Numerals

[0088] 100 Switching circuit 102 Power supply line 104 Ground line 110 Bridge circuit MH High-side transistor ML Low-side transistor 200 Motor driver circuit 202 High-side off-sensor 204 Low-side off-sensor 210 Control circuit 220 High-side driver circuit 260 Low-side driver circuit 300 Motor drive device 302 Three-phase motor 500 Reference current source ISET Current setting pin M11 First transistor OA11 First operational amplifier CM11 Current mirror circuit R11 First resistor 510 Low-pass filter 520 V / I converter M12 Second transistor R12 Second resistor OA12 Second operational amplifier 230 Timer circuit

Claims

1. A current setting pin to which an external setting resistor is to be connected, A reference current source that generates a reference current having a current amount determined by the setting resistor, Comprising, The reference current source, A first transistor having a first electrode connected to the current setting pin, An operational amplifier that receives a reference voltage at a first input, receives the voltage of the current setting pin at a second input, and has an output connected to a control electrode of the first transistor, A current mirror circuit that folds back a first current flowing through the first transistor, A first resistor connected to an output node of the current mirror circuit, A low-pass filter that receives a first voltage signal that is a voltage drop of the first resistor, A voltage / current converter that converts a second voltage signal output by the low-pass filter into the reference current, A motor driver circuit including.

2. The motor driver circuit according to claim 1, wherein a cut-off frequency of the low-pass filter is 10 kHz or less.

3. The motor driver circuit according to claim 1 or 2, wherein the cut-off frequency of the low-pass filter is 1 / 4 or less of a switching frequency of the motor driver circuit.

4. The motor driver circuit according to claim 1 or 2, wherein the first resistor and the second resistor are formed by pairing on a semiconductor substrate.

5. The motor driver circuit according to claim 1 or 2, wherein the low-pass filter is an RC filter.

6. The motor driver circuit according to claim 1 or 2, wherein the low-pass filter is an LC filter.

7. The motor driver circuit according to claim 1 or 2, wherein the low-pass filter is an LR filter.

8. The motor driver circuit according to claim 1 or 2, wherein the low-pass filter is an active filter.

9. Including a capacitor charged by the reference current, and further comprising a timer circuit that measures a time inversely proportional to the reference current, the motor driver circuit according to claim 1 or 2.

10. A high-side driver that drives a high-side transistor, A low-side driver that drives a low-side transistor, Further comprising, The motor driver circuit according to claim 9, wherein a dead time of the high-side transistor and the low-side transistor is controlled using the timer circuit.

11. A high-side driver that drives a high-side transistor with a constant current, A low-side driver for driving a low-side transistor, further comprising, The drive currents of the high-side driver and the low-side driver are according to the reference current. The motor driver circuit according to claim 1 or 2.

12. The reference current source further includes an internal resistance connected between the first electrode of the first transistor and the current setting pin. The motor driver circuit according to claim 1 or 2.

13. The motor driver circuit according to claim 1 or 2, integrally formed on one semiconductor substrate.

14. A motor, The motor driver circuit according to claim 13 for driving the motor, An electronic device comprising.

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