JP5060750B2 - Motor drive circuit and electronic device using the same - Google Patents

Description

  The present invention relates to a motor drive technique for controlling torque based on a current flowing in a motor coil.

For example, in order to control the motor current so as to be an allowable maximum value, it is generally performed to detect the current flowing in the motor coil (Patent Document 1 below). In the motor drive device of Patent Document 1, the ground sides of the two low-side switches of the H bridge are connected to each other, and a resistor provided between the connection point and the ground is used for current detection.
JP-A-8-154389 (especially FIG. 2)

  In the so-called current limit function, it can be said that the technique of Patent Document 1 has achieved a certain result. However, when controlling the current flowing in the motor coil to be constant, there is room for improvement in the technique of Patent Document 1 in order to increase the accuracy of current detection. Specifically, the motor current detection circuit described in Patent Document 1 cannot detect a regenerative current when either a low-side switch or a high-side switch is driven by a pulse width modulation (PWM) signal. For the torque control, current detection accuracy is not sufficient.

  The present invention has been made in recognition of such a situation, and an object thereof is to improve the detection accuracy of the current flowing in the motor coil.

  One embodiment of the present invention is a motor drive circuit. This motor drive circuit has two sets of a high side switch and a low side switch, an H bridge circuit that energizes the motor coil, and a current detection circuit that detects a current flowing through the motor coil and outputs a detection voltage corresponding to the result A pulse signal generation unit that generates a pulse signal whose duty ratio changes so that the magnitude of the detected voltage matches a voltage value determined by the torque instruction signal, and a direction instruction signal and a pulse that indicate the energization direction to the motor coil And a pre-driver for driving the switching circuit based on the signal. The pre-driver fixedly turns on one of the high-side switch and the low-side switch arranged diagonally, and periodically turns on and off the other based on the pulse signal. When driving the first set of the high-side switch and the low-side switch, the current detection circuit has a current flowing during an energization period in which both the high-side switch and the low-side switch are turned on, and at least one of the high-side switch and the low-side switch A current that flows during a regeneration period that is turned off, a first resistor that is provided on a path through which both flow, and a current that flows during the energization period when driving the second set of high-side switches and low-side switches; Current flowing in the period, and a second resistor provided on a path through which both flow, and when driving the first set of high-side switches and low-side switches, the voltage drop of the first resistor is When driving a pair of high-side and low-side switches, the voltage drop across the second resistor is used as the detection result. Used.

  According to this aspect, since both the current flowing during the energization period and the current flowing during the regeneration period are detected, the detection accuracy of the current of the motor coil is increased, and the motor torque can be controlled more accurately.

  Another embodiment of the present invention is also a motor drive circuit. The motor drive circuit includes a switching circuit for energizing the motor coil, a current detection circuit for detecting a current flowing in the motor coil and outputting a detection voltage corresponding to the result, and the magnitude of the detection voltage is determined by a torque instruction signal. A pulse signal generation unit that generates a pulse signal whose duty ratio changes so as to match the voltage value, and a pre-driver that drives the switching circuit based on the direction indication signal and the pulse signal instructing the energization direction to the motor coil Prepare. The switching circuit includes a first terminal and a second terminal connected to both ends of the motor coil, a first switching transistor provided between the power supply terminal and the first terminal, and between the power supply terminal and the second terminal. A second switching transistor provided between, a third switching transistor provided between the first terminal and the fixed voltage terminal, and a fourth switching transistor provided between the second terminal and the fixed voltage terminal. Have. The pre-driver, when flowing the current in the first direction through the motor coil, either turns on either the first switching transistor or the fourth switching transistor fixedly, and periodically turns the other on / off based on the pulse signal, When a current in the second direction is passed through the motor coil, one of the second switching transistor and the third switching transistor is fixedly turned on, and the other is periodically turned on / off based on the pulse signal. The current detection circuit includes a current flowing through the motor coil during a period in which the first switching transistor and the fourth switching transistor are simultaneously turned on when a current in the first direction flows, and one of the first switching transistor and the fourth switching transistor. When the current flows in the second direction, and when the current flows in the second direction, the second switching transistor and the third switching transistor are simultaneously turned on. A second resistor provided in a path through which both the current flowing in the motor coil during the period when the current flows and the current flowing in the motor coil during the period when either the second switching transistor or the third switching transistor is off. When the current in the first direction flows 1 a voltage drop across the resistor, when current flows in the second direction voltage drop of the second resistor is used as each of the detection result.

  According to this aspect, when the current in the first direction flows, the first resistor is provided in the path through which the motor coil current flows, and when the current in the first direction flows, the voltage drop of the first resistor is detected. Use as a result. Further, a second resistor is provided in a path through which the motor coil current flows consistently when a current in the second direction flows, and a voltage drop of the second resistor is used as a detection result when a current in the second direction flows. . As a result, the motor coil is used throughout the entire period including the period when one of the paired high-side switch and low-side switch is off, both when the current in the first direction flows and when the current in the second direction flows. Current can be detected. Therefore, the current of the motor coil can be detected with high accuracy, and the motor torque can be controlled more accurately.

  Yet another embodiment of the present invention is also a motor drive circuit. The motor drive circuit includes a switching circuit for energizing the motor coil, a current detection circuit for detecting a current flowing in the motor coil and outputting a detection voltage corresponding to the result, and the magnitude of the detection voltage is determined by a torque instruction signal. A pulse signal generation unit that generates a pulse signal whose duty ratio changes so as to match the voltage value, and a pre-driver that drives the switching circuit based on the direction indication signal and the pulse signal instructing the energization direction to the motor coil Prepare. The switching circuit includes a first terminal and a second terminal connected to both ends of the motor coil, a first switching transistor provided between the power supply terminal and the first terminal, and between the power supply terminal and the second terminal. A second switching transistor provided between, a third switching transistor provided between the first terminal and the fixed voltage terminal, and a fourth switching transistor provided between the second terminal and the fixed voltage terminal. Have. When flowing the current in the first direction through the motor coil, the pre-driver fixedly turns on one of the first switching transistor and the fourth switching transistor, and periodically turns on / off the other based on the pulse signal, The current detection circuit uses a voltage drop of the switching transistor that is fixedly turned on as a detection result. When flowing the current in the second direction through the motor coil, the pre-driver fixedly turns on one of the second switching transistor and the third switching transistor and periodically turns on / off the other based on the pulse signal, The current detection circuit uses a voltage drop of the switching transistor that is fixedly turned on as a detection result.

  According to this aspect, the voltage drop of the switching transistor that is fixedly turned on when the current in the first direction flows through the motor coil is used as the detection result when the current in the first direction flows. Further, the voltage drop of the switching transistor that is fixedly turned on when the current in the second direction flows through the motor coil is used as a detection result when the current in the second direction flows. Accordingly, one of the high-side switch and the low-side switch that are paired with each other when the current in the first direction flows and when the current in the second direction flows without separately providing a resistor for current detection. It is possible to detect the current of the motor coil throughout the entire period including the period in which is turned off. Therefore, the current of the motor coil can be detected with high accuracy, and the motor torque can be controlled more accurately. In addition, since a resistor for current detection is not required, the loss can be reduced correspondingly and the efficiency is high.

  Yet another embodiment of the present invention is an electronic device. The electronic device includes a motor and the motor drive circuit that drives the motor.

  According to this aspect, the merit of accurate torque control can be enjoyed as an electronic device, and the value of the electronic device is increased.

  It should be noted that any combination of the above-described constituent elements and a representation obtained by converting the expression of the present invention between methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  According to the present invention, the detection accuracy of the current flowing through the motor coil can be increased.

(First embodiment)
FIG. 1 shows a configuration of a motor drive circuit 100 according to the first embodiment. This circuit can be used, for example, as a motor driver for driving a motor for a diaphragm, autofocus, zoom lens of a digital camera.
The motor drive circuit 100 includes an H-bridge circuit 12, a current detection circuit 14, a pulse signal generation unit 16, and a predriver 18, which are integrated on a single semiconductor substrate. Note that “integrated integration” includes the case where all the circuit components are formed on a semiconductor substrate and the case where the main components of the circuit are integrated, and is used for adjusting circuit constants. The resistance of the part or the like may be provided outside the semiconductor substrate. By being integrated on a single semiconductor substrate, mounting on an electronic device is facilitated. The motor drive circuit 100 receives the power supply voltage Vdd from the power supply terminal 106 and is connected to the ground via the fixed voltage terminal 108.

The H bridge circuit 12 is a switching circuit that energizes the motor coil 150.
The current detection circuit 14 detects a current flowing through the motor coil 150 and outputs a detection voltage Vdet corresponding to the result.
The pulse signal generation unit 16 generates a pulse signal Vpls whose duty ratio changes so that the magnitude of the detection voltage Vdet matches the voltage value determined by the torque instruction signal Strq. As the pulse signal generator 16, a general PWM circuit can be used. The torque instruction signal Strq is supplied from, for example, a microprocessor (not shown).
The pre-driver 18 generates and outputs pre-drive signals V1 to V4, which will be described later, based on the direction instruction signal Sdrc and the pulse signal Vpls for instructing the energization direction to the motor coil 150, and drives the H-bridge circuit 12 by these signals. To do. The direction instruction signal Sdrc is a binary signal generated based on the result of detecting the position of the rotor. The direction of the current flowing through the motor coil 150 is determined depending on whether the binary signal is high level or low level. Various known techniques can be used to detect the position of the rotor.

  The H bridge circuit 12 includes a first terminal 102, a second terminal 104, a first switching transistor M1, a second switching transistor M2, a third switching transistor M3, and a fourth switching transistor M4.

The first switching transistor M1 and the second switching transistor M2 constitute a high-side switch of the H bridge circuit 12, respectively. FIG. 1 shows a case where these are P-channel MOSFETs (Metal Oxide Semiconductor Field Effect Transistors).
The third switching transistor M3 and the fourth switching transistor M4 constitute a low-side switch of the H bridge circuit 12, respectively. FIG. 1 shows a case where they are N-channel MOSFETs.
In the present embodiment, the body diode between the back gate and the drain of each of the first switching transistor M1 to the fourth switching transistor M4 is used as a regenerative current path.

  The first terminal 102 and the second terminal 104 are connected to both ends of the motor coil 150, respectively. The source of the first switching transistor M1 is connected to the power supply terminal 106, and the drain is connected to the first terminal 102. The source of the second switching transistor M2 is connected to the power supply terminal 106, and the drain is connected to the second terminal 104. The drain of the third switching transistor M3 is connected to the first terminal 102, and the source is connected to the fixed voltage terminal 108 via a second resistor R2 described later. The drain of the fourth switching transistor M4 is connected to the second terminal 104, and the source is connected to the fixed voltage terminal 108 via a first resistor R1 described later.

  The gates of the first switching transistor M1 to the fourth switching transistor M4 are driven by predrive signals V1 to V4 output from the predriver 18, respectively. Details will be described later in the time chart.

  The current detection circuit 14 includes a first resistor R1, a second resistor R2, a first switch SW1, a second switch SW2, a third switch SW3, a fourth switch SW4, and an amplifier 42. The first resistor R1 and the second resistor R2 are paired on one semiconductor substrate. Note that “pairing” means that a plurality of elements of the same type are formed in close proximity on a single semiconductor substrate, so that variations in manufacturing characteristics, temperature variations, and the like are related to the characteristics of these elements. That means aligning. Each of the first switch SW1 to the fourth switch SW4 is an electronic switch such as a MOSFET.

  The first resistor R1 is provided in a path connecting the source of the fourth switching transistor M4 and the fixed voltage terminal 108. The second resistor R2 is provided in a path connecting the source of the third switching transistor M3 and the fixed voltage terminal 108. The first switch SW1 is provided on a path connecting the contact point of the third switching transistor M3 and the second resistor R2 and the non-inverting input terminal of the amplifier 42. The second switch SW2 is provided in a path connecting the contact point of the second resistor R2 and the fixed voltage terminal 108 and the inverting input terminal of the amplifier 42. The third switch SW3 is provided in a path that connects the contact point of the first resistor R1 and the fixed voltage terminal 108 to the inverting input terminal of the amplifier 42. The fourth switch SW4 is provided in a path connecting the contact point of the fourth switching transistor M4 and the first resistor R1 and the non-inverting input terminal of the amplifier 42.

The first switch SW1 and the second switch SW2 are switches for inputting a potential difference between both ends of the second resistor R2, that is, a voltage drop, to the amplifier 42. The third switch SW3 and the fourth switch SW4 are switches for inputting a potential difference between both ends of the first resistor R1 to the amplifier 42. As a signal for controlling on / off of the first switch SW1 to the fourth switch SW4, a part of the predrive signal from the predriver 18 may be used, or a signal from a switch control circuit (not shown) may be used. The on / off timing of these switches will be described in detail in the later-described time chart.
The amplifier 42 amplifies a potential difference between both ends of the first resistor R1 or the second resistor R2, and outputs the amplified voltage difference to the pulse signal generation unit 16 as a detection voltage Vdet.

  Hereinafter, the operation of the motor drive circuit 100 will be described with reference to FIG.

  FIG. 2 is a time chart showing on / off of the first switching transistor M1 to the fourth switching transistor M4 and the first switch SW1 to the fourth switch SW4 of FIG.

  A period indicated by “T1” indicates a period in which current flows in a direction from the first terminal 102 to the second terminal 104 through the motor coil 150 (hereinafter referred to as “first direction”). This period is hereinafter referred to as “first period”. A period indicated by “T2” indicates a period in which current flows in a direction opposite to the first direction (hereinafter referred to as “second direction”). This period is hereinafter referred to as “second period”. The pre-driver 18 drives the H bridge circuit 12 so as to repeat the first period and the second period in accordance with the direction instruction signal Sdrc.

  In the first period, the pre-driver 18 periodically turns on and off the first switching transistor M1 and turns on the fourth switching transistor M4 in a fixed manner. On the other hand, the second switching transistor M2 and the third switching transistor M3 are turned off. The current detection circuit 14 turns on the third switch SW3 and the fourth switch SW4, and turns off the first switch SW1 and the second switch SW2.

During the period in which both the first switching transistor M1 and the fourth switching transistor M4 are on (hereinafter referred to as “first driving period”), the current of the motor coil 150 is supplied from the power supply terminal 106 to the first switching transistor M1, the first terminal. 102, the motor coil 150, the second terminal 104, the fourth switching transistor M4, the first resistor R1, and the fixed voltage terminal 108.
On the other hand, during the period in which the first switching transistor M1 is off and the fourth switching transistor M4 is on (hereinafter also referred to as “first regeneration period”), the current of the motor coil 150 flows from the fixed voltage terminal 108 to the second resistance. R2, the body diode of the third switching transistor M3, the first terminal 102, the motor coil 150, the second terminal 104, the fourth switching transistor M4, and the first resistor R1 flow through the path.

  Here, it should be noted that the same current as that of the motor coil 150 flows through the first resistor R1 throughout the first period. In other words, in the present embodiment, the first resistor R1 is provided in a path through which the same current as the current of the motor coil 150 flows throughout the first period. During this period, the current detection circuit 14 uses the voltage across the first resistor R1 as a detection result, amplifies the voltage by the amplifier 42, and outputs it as the detection voltage Vdet. Thus, the current flowing through the motor coil 150 can be detected throughout the first period, that is, both in the first drive period and the first regeneration period.

  In the second period, the pre-driver 18 periodically turns on and off the second switching transistor M2, and turns on the third switching transistor M3 in a fixed manner. On the other hand, the first switching transistor M1 and the fourth switching transistor M4 are turned off. The current detection circuit 14 turns on the first switch SW1 and the second switch SW2, and turns off the third switch SW3 and the fourth switch SW4.

During the period in which both the second switching transistor M2 and the third switching transistor M3 are on (hereinafter referred to as “second driving period”), the current of the motor coil 150 is supplied from the power supply terminal 106 to the second switching transistor M2, the second terminal. 104, the motor coil 150, the first terminal 102, the third switching transistor M3, the second resistor R2, and the fixed voltage terminal 108.
On the other hand, during the period in which the second switching transistor M2 is off and the third switching transistor M3 is on (hereinafter also referred to as “second regeneration period”), the current of the motor coil 150 flows from the fixed voltage terminal 108 to the first resistance. R1, the body diode of the fourth switching transistor M4, the second terminal 104, the motor coil 150, the first terminal 102, the third switching transistor M3, and the second resistor R2.

  Here, it should be noted that the same current as that of the motor coil 150 flows through the second resistor R2 throughout the second period. In other words, in the present embodiment, the second resistor R2 is provided in a path through which the same current as that of the motor coil 150 flows throughout the second period. During this period, the current detection circuit 14 uses the voltage across the second resistor R2 as a detection result, amplifies the voltage by the amplifier 42, and outputs it as the detection voltage Vdet. Thereby, the current flowing through the motor coil 150 can be detected throughout the second period, that is, both in the second drive period and the second regeneration period.

  Thus, according to the motor drive circuit 100 of the present embodiment, the current detection circuit 14 causes the current flowing through the motor coil 150 through the first resistor R1 and the second resistor R2 throughout the first period and the second period. Can be detected. Therefore, the accuracy of current detection is improved, and the torque of the motor can be controlled more accurately. In addition, since the fluctuation of the detection result is small compared to the case where the current is detected with a single resistor as in the prior art, the performance of the amplifier that amplifies the voltage of the detection result is sufficient, and the cost is low. It is.

  Further, since the first resistor R1 and the second resistor R2 are paired on one semiconductor substrate, the relative error between their resistance values and electrical characteristics can be minimized, and the accuracy of current detection can be improved. Enhanced.

  Further, the current flowing through the first resistor R1 has the same direction throughout the first period. Similarly, the current flowing through the second resistor R2 is in the same direction throughout the second period. Therefore, since it is not necessary to invert the voltage as the current detection result in the current detection circuit 14, the configuration is complicated in order to detect the current flowing through the motor coil 150 throughout the first period and the second period. Risk can be reduced.

(Second Embodiment)
In the motor drive circuit 100 according to the first embodiment, the current flowing through the motor coil 150 is detected by the first resistor R1 and the second resistor R2 throughout the first period and the second period. In the motor drive circuit 200 of the second embodiment, the current flowing through the motor coil 150 is similarly detected without providing the first resistor R1 and the second resistor R2. For this reason, in the motor drive circuit 200 of the second embodiment, the on-resistances of the fourth switching transistor M4 and the third switching transistor M3 are used instead of the first resistor R1 and the second resistor R2 of FIG. The “on resistance” refers to a channel resistance when the switching transistor is turned on.

  FIG. 3 shows a configuration of a motor drive circuit 200 according to the second embodiment. The time chart of FIG. 2 is applied to the motor drive circuit 200 as well. In FIG. 3, the same or similar components as those shown in FIG. Hereinafter, the difference will be mainly described.

  In the motor drive circuit 200, the fourth switching transistor M4 and the third switching transistor M3 constitute a low-side switch of the H-bridge circuit 12 as in the case of FIG. 1, and different from FIG. Instead of the resistor R1 and the second resistor R2, it is used for current detection. The third switching transistor M3 and the fourth switching transistor M4 are paired on one semiconductor substrate in FIG. Compared with FIG. 1, the motor drive circuit 200 further includes a characteristic compensation circuit 56 that compensates for the on-resistance characteristics of the third switching transistor M3 and the fourth switching transistor M4. The characteristic compensation circuit 56 changes the duty ratio of the pulse signal Vpls in accordance with the change in the ON resistance of the third switching transistor M3 and the fourth switching transistor M4 in addition to the change in the detection voltage Vdet. Specifically, the value of the torque control voltage Vtrq determined by the torque instruction signal Strq is changed. The configuration of the characteristic compensation circuit 56 will be described later.

  Similar to the first resistor R1 of FIG. 1, the same current as that of the motor coil 150 flows between the source and drain of the fourth switching transistor M4 of FIG. 3 throughout the first period. Further, similarly to the second resistor R2 of FIG. 1, the same current as the current of the motor coil 150 flows between the source and drain of the third switching transistor M3 of FIG. 3 throughout the second period.

  Referring to the time chart of FIG. 2, in the first period, the voltage between the source and the drain of the fourth switching transistor M4 is a detection result of the current flowing in the motor coil 150 in the current detection circuit 54. Similarly, in the second period, the voltage between the source and the drain of the third switching transistor M3 becomes a detection result of the current flowing through the motor coil 150.

Therefore, according to the motor drive circuit 200 of the second embodiment, by using the on-resistances of the third switching transistor M3 and the fourth switching transistor M4 without providing the first resistor R1 and the second resistor R2, The current flowing through the motor coil 150 can be detected throughout the first period and the second period.
Furthermore, since the first resistor R1 and the second resistor R2 are removed, losses due to these resistors are eliminated, so that the motor drive is made more efficient.
In addition, since the third switching transistor M3 and the fourth switching transistor M4 are paired on one semiconductor substrate, the relative error in the resistance value and electrical characteristics of these on-resistances can be minimized, The accuracy of current detection is increased.

FIG. 4 shows a configuration of the characteristic compensation circuit 56 of FIG.
The characteristic compensation circuit 56 includes a monitoring transistor M5, a current source 62, a buffer 64, and a DAC 66 (DAC: Digital-Analog Converter). The DAC 66 has a resistance ladder and a switch group. One switch is selected from the switch group of the DAC 66 by the torque instruction signal Strq. The voltage output via this switch is the torque control voltage Vtrq. The torque control voltage Vtrq is output from the DAC 66 to the pulse signal generator 16.

  The monitoring transistor M5 is an N-channel MOSFET, and is paired with the third switching transistor M3 and the fourth switching transistor M4 in FIG. 3 on one semiconductor substrate. Therefore, the relative errors in their on-resistance and electrical characteristics are minimized. Further, since the gates of the third switching transistor M3, the fourth switching transistor M4, and the monitoring transistor M5 are driven by the power supply voltage Vdd, the power supply voltage characteristics of their on-resistances are made uniform.

The current source 62 and the monitoring transistor M5 are connected in series between the power supply terminal 106 and the fixed voltage terminal 108.
The source of the monitor transistor M5 is connected to the fixed voltage terminal 108, and the drain is connected to the input of the buffer 64. The gate of the monitor transistor M5 is connected to the power supply terminal 106. Therefore, the monitoring transistor M5 is always turned on.

The current source 62 passes a current having the same magnitude as the current to be supplied to the motor coil 150 of FIG. 3 to the monitoring transistor M5.
The buffer 64 uses the output as the high potential side reference voltage of the DAC 66.

  Now, consider that the ON resistance of the third switching transistor M3 and the fourth switching transistor M4 has increased due to the temperature rise. At this time, even if currents of the same magnitude flow, the voltage between the source and drain of the third switching transistor M3 and the fourth switching transistor M4 becomes larger than before the temperature rise. As a result, the current detection circuit 54 changes the detection voltage Vdet in the same manner as when the current increases, even though the same amount of current flows. Then, the pulse signal generator 16 tries to suppress the current flowing through the motor coil 150 by changing the duty ratio of the pulse signal Vpls. In this regard, when the characteristic compensation circuit 56 of FIG. 4 is provided, the voltage value of the torque control voltage Vtrq increases as the temperature rises. This is because the on-resistance of the monitor transistor M5 also rises, and the voltage between the source and drain increases, and the high-potential side reference voltage of the DAC 66 output from the buffer 64 increases. This attempts to increase the current flowing through the motor coil 150 by changing the duty ratio of the pulse signal Vpls generated by the pulse signal generator 16. That is, when the temperature rises, the torque control voltage Vtrq changes so as to offset the influence due to the change in the detection voltage Vdet from the current detection circuit 54. Therefore, the temperature characteristics of the on-resistances of the third switching transistor M3 and the fourth switching transistor M4 are compensated. Similarly, when the on-resistance increases due to the change of the power supply voltage Vdd, the compensation is performed. Conversely, when the on-resistance decreases, the detection voltage Vdet changes the duty ratio of the pulse signal Vpls to increase the current flowing through the motor coil 150, whereas the torque control voltage Vtrq decreases. Thus, the duty ratio of the pulse signal Vpls is changed to reduce the current flowing through the motor coil 150. These effects are offset and the effects when the on-resistance is reduced are also compensated.

  In this way, by providing the characteristic compensation circuit 56, even if each on-resistance of the third switching transistor M3 and the fourth switching transistor M4 changes due to various factors, the influence of the change is reduced. More accurate torque control is possible as compared with the case where no provision is made.

  Those skilled in the art will understand that the above-described embodiment is an exemplification, and that various modifications can be made to the combination of each component and each treatment process, and such modifications are within the scope of the present invention. . Hereinafter, modifications will be listed.

(Modification 1)
In the first embodiment, the first resistor R1 is provided in the path connecting the source of the fourth switching transistor M4 and the fixed voltage terminal 108, and the path connecting the source of the third switching transistor M3 and the fixed voltage terminal 108. The second resistor R2 is provided. However, the path for providing the first resistor R1 and the second resistor R2 is not limited to this.
In the modification, the first resistor R1 may be provided in a path connecting the drain of the fourth switching transistor M4 and the second terminal 104. Since the same current as the current of the motor coil 150 flows through this path throughout the first period, the current flowing through the motor coil 150 can be detected throughout the first period.
In the modification, the second resistor R2 may be provided in a path connecting the drain of the third switching transistor M3 and the first terminal 102. Since the same current as that of the motor coil 150 flows through this path throughout the entire second period, the current flowing through the motor coil 150 can be detected throughout the entire second period.

(Modification 2)
In the embodiment, the pre-driver 18 periodically turns on and off the first switching transistor M1 and fixedly turns on the fourth switching transistor M4 in the first period. In the second period, the second switching transistor M2 is periodically turned on / off, and the third switching transistor M3 is fixedly turned on.
In the modification, on the contrary, the pre-driver 18 periodically turns on and off the fourth switching transistor M4 and fixedly turns on the first switching transistor M1 in the first period. In the second period, the third switching transistor M3 is periodically turned on / off, and the second switching transistor M2 is fixedly turned on.

  When this modification is applied to the first embodiment, the path for providing the first resistor R1 and the second resistor R2 is changed. The path for providing the first resistor R1 may be a path for connecting the source of the first switching transistor M1 and the power supply terminal 106 or a path for connecting the drain of the first switching transistor M1 and the first terminal 102. The path for providing the second resistor R2 may be a path for connecting the source of the second switching transistor M2 and the power supply terminal 106 or a path for connecting the drain of the second switching transistor M2 and the second terminal 104. Also in this case, the same effect as that of the first embodiment can be obtained.

  When this modified example is applied to the second embodiment, the switching transistor serving as a substitute for the first resistor R1 and the second resistor R2 is changed. That is, the current detection circuit 54 uses the voltage between the source and drain of the first switching transistor M1 as the detection result of the current flowing in the motor coil 150 in the first period, and the source and drain of the second switching transistor M2 in the second period. The voltage between the drains is taken as the detection result of the current flowing through the motor coil 150. Also in this case, the same effect as the second embodiment can be obtained.

(Modification 3)
In the embodiment, in the pre-driver 18, the third switching transistor M3 is turned off in the first period. In the modification, the third switching transistor M3 is exclusively turned on / off with the first switching transistor M1 in the first period, and synchronous rectification is performed. Similarly, in the second period, the fourth switching transistor M4 is exclusively turned on / off with the second switching transistor M2, and synchronous rectification is performed. Thereby, the channel between the source and the drain of the third switching transistor M3 can be used for the current path in the first regeneration period, and the channel between the source and the drain of the fourth switching transistor M4 can be used for the current path in the second regeneration period. Therefore, compared with the case where each body diode of the third switching transistor M3 and the fourth switching transistor M4 is used as a path, the voltage drop due to the switching transistor can be reduced, so that the driving efficiency of the motor is increased.

(Other variations)
In the embodiment, the second switch SW2 and the third switch SW3 connected to the inverting input terminal of the amplifier 42 are provided, but one of them may be provided. Alternatively, both may be omitted, and a fixed voltage may be fixedly input from the fixed voltage terminal 108 to the inverting input terminal of the amplifier 42.

  In the embodiment, the first switching transistor M1 and the second switching transistor M2 are P-channel MOSFETs. In a modification, they may be N-channel MOSFETs. In this case, in FIG. 1 or FIG. 3, the positions of the source and drain of the first switching transistor M1 and the second switching transistor M2 are exchanged.

  In the embodiment, the case where the first switching transistor M1 to the fourth switching transistor M4 are MOSFETs has been described. In a modification, each switching transistor may be a bipolar transistor. In this case, the configuration of FIG. 1 or FIG. 3 can be applied mutatis mutandis by making the high-side switch a PNP transistor, the low-side switch an NPN transistor, and correlating the collector, emitter, and base with the drain, source, and gate, respectively. A diode for securing a path for the regenerative current may be provided as appropriate.

  In the embodiment, the case where the first resistor R1 and the second resistor R2 are built in the IC has been described. In a variant, these resistors may be externally attached.

  In the embodiment, the case where the motor drive circuit is integrated on one semiconductor substrate has been described. However, the present invention is not limited to this, and a part or all of the circuit elements are configured by discrete components. Also good. In particular, the first switching transistor M1 to the fourth switching transistor M4 may be externally attached.

It is a circuit diagram which shows the structure of the motor drive circuit concerning 1st Embodiment. 2 is a time chart showing ON / OFF of a first switching transistor to a fourth switching transistor and a first switch to a fourth switch in FIG. 1. It is a circuit diagram which shows the structure of the motor drive circuit concerning 2nd Embodiment. FIG. 4 is a circuit diagram illustrating a configuration of the characteristic compensation circuit of FIG. 3.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 12 ... H bridge circuit, 14 ... Current detection circuit, 16 ... Pulse signal generation part, 18 ... Pre-driver, 100 ... Motor drive circuit, 102 ... 1st terminal, 104. ..Second terminal 106 ... Power supply terminal 108 ... Fixed voltage terminal 150 ... Motor coil M1 ... First switching transistor M2 ... Second switching transistor M3 ... 3rd switching transistor, M4 ... 4th switching transistor, R1 ... 1st resistance, R2 ... 2nd resistance, Strq ... Torque instruction signal, Vtrq ... Torque control voltage, Vdet ... Detection voltage, Vpls ... pulse signal.

Claims (5)

A switching circuit for energizing the motor coil;
A current detection circuit for detecting a current flowing in the motor coil and outputting a detection voltage according to the result;
A pulse signal generation unit that generates a pulse signal whose duty ratio changes so that the magnitude of the detection voltage matches a voltage value determined by a torque instruction signal;
A direction indication signal for instructing the energization direction to the motor coil and a pre-driver for driving the switching circuit based on the pulse signal;
The switching circuit is
A first terminal and a second terminal respectively connected to both ends of the motor coil;
A first switching transistor provided between a power supply terminal and the first terminal;
A second switching transistor provided between the power supply terminal and the second terminal;
A third switching transistor provided between the first terminal and the fixed voltage terminal;
A fourth switching transistor provided between the second terminal and the fixed voltage terminal;
The pre-driver is
When a current in the first direction flows through the motor coil, the fourth switching transistor is fixedly turned on, the first switching transistor is periodically turned on / off based on the pulse signal,
When a current in the second direction flows through the motor coil, the third switching transistor is fixedly turned on, and the second switching transistor is periodically turned on / off based on the pulse signal,
The current detection circuit includes:
A first resistor provided in series with the fourth switching transistor between the second terminal and the fixed voltage terminal;
A second resistor provided in series with the third switching transistor between the first terminal and the fixed voltage terminal;
A first switch having one end connected to a terminal on the high potential side of the second resistor;
A second switch having one end connected to a low-potential-side terminal of the second resistor;
A third switch having one end connected to a terminal on the low potential side of the first resistor;
A fourth switch having one end connected to a terminal on the high potential side of the first resistor;
The other end of the first switch and the other end of the fourth switch are connected to one input terminal, and the other end of the second switch and the other end of the third switch are connected to the other input terminal. An amplifier that generates a detection voltage according to a potential difference between the one input terminal and the other input terminal;
The third and fourth switches are turned on, the first and second switches are turned off, and the current in the second direction is A motor driving circuit characterized in that the first and second switches are in an on state and the third and fourth switches are in an off state during a period of flowing through a motor coil . A switching circuit for energizing the motor coil;
A current detection circuit for detecting a current flowing in the motor coil and outputting a detection voltage according to the result;
A pulse signal generation unit that generates a pulse signal whose duty ratio changes so that the magnitude of the detection voltage matches a voltage value determined by a torque instruction signal;
A direction indication signal for instructing the energization direction to the motor coil and a pre-driver for driving the switching circuit based on the pulse signal;
The switching circuit is
A first terminal and a second terminal respectively connected to both ends of the motor coil;
A first switching transistor provided between a power supply terminal and the first terminal;
A second switching transistor provided between the power supply terminal and the second terminal;
A third switching transistor provided between the first terminal and the fixed voltage terminal;
A fourth switching transistor provided between the second terminal and the fixed voltage terminal;
The pre-driver is
When flowing a current in the first direction through the motor coil, the first switching transistor is fixedly turned on, the fourth switching transistor is periodically turned on / off based on the pulse signal,
When a current in the second direction flows through the motor coil, the second switching transistor is fixedly turned on, and the third switching transistor is periodically turned on / off based on the pulse signal,
The current detection circuit includes:
A first resistor provided in series with the first switching transistor between the first terminal and the power supply terminal;
A second resistor provided in series with the second switching transistor between the second terminal and the power supply terminal;
A first switch having one end connected to a terminal on the high potential side of the second resistor;
A second switch having one end connected to a low-potential-side terminal of the second resistor;
A third switch having one end connected to a terminal on the low potential side of the first resistor;
A fourth switch having one end connected to a terminal on the high potential side of the first resistor;
The other end of the first switch and the other end of the fourth switch are connected to one input terminal, and the other end of the second switch and the other end of the third switch are connected to the other input terminal. An amplifier that generates a detection voltage according to a potential difference between the one input terminal and the other input terminal;
The third and fourth switches are turned on, the first and second switches are turned off, and the current in the second direction is A motor driving circuit characterized in that the first and second switches are in an on state and the third and fourth switches are in an off state during a period of flowing through a motor coil . The motor drive circuit according to claim 1 or 2, characterized in that said first resistor and said second resistor is paired with a single semiconductor substrate. The motor drive circuit according to any one of claims 1 to 3, characterized in that it is integrated on a single semiconductor substrate. A motor and a motor drive circuit according to any one of claims 1 to 4 for driving the motor,
An electronic device comprising:

Images