Current control circuit and motor drive circuit that can accurately and easily control a drive current

A current control circuit includes a control current generation circuit that generates a control current in accordance with an external current control signal. A plurality of drive current generation circuits generate drive currents in accordance with the control current that is generated by and supplied from the control current generation circuit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to current control circuits and motor drive circuits, and more particularly, to a current control circuit and a motor drive circuit that can control a drive current in accordance with an input control signal.

2. Description of the Related Art

Conventionally, a motor drive circuit is known that controls a drive current for a motor by: driving a current mirror circuit in accordance with an external control signal; separately generating a source control current and a sink control current by the current mirror circuit; controlling a source drive circuit of the motor by the source control current generated by the current mirror circuit; and controlling a sink drive circuit by the sink control current generated by the current mirror circuit (refer to Japanese Laid-Open Patent Application No. 60-237871, for example).

The conventional motor drive circuit separately generates the source control current and the sink control current by the current mirror circuit, and controls the source drive circuit of the motor by the source control current generated by the current mirror circuit. Hence, there is a problem in that the drive current for the motor is varied when the characteristics of a transistor supplying a current to the source of the current mirror circuit and those of a transistor supplying a current to the sink of the current mirror circuit do not match.

In addition, in the conventional motor drive circuit, the configuration of the source drive circuit and that of the sink drive circuit are different. For this reason, the characteristics of the source side and those of the sink side do not match, which results in variation of the drive current for the motor.

SUMMARY OF THE INVENTION

It is a general object of the present invention to provide an improved and useful current control circuit and a motor drive circuit in which one or more of the above-mentioned problems are eliminated.

It is another and more specific object of the present invention to provide a current control circuit and a motor drive circuit that can accurately and easily control a drive current.

In order to achieve the above-mentioned objects, according to one aspect of the present invention, there is provided a current control circuit including:

a control current generation circuit that generates a control current in accordance with an external current control signal; and

a plurality of drive current generation circuits that generate drive currents in accordance with the control current that is generated by and supplied from the control current generation circuit.

Additionally, according to another aspect of the present invention, there is provided a motor drive circuit including:

a first drive current control element that controls supply of a drive current to a motor;

a second drive current control element that draws the drive current from the motor;

a control current generation circuit that generates a control current in accordance with an external current control signal;

a first drive current generation circuit that drives the first drive current control element in accordance with the control current generated by and supplied from the control current generation circuit; and

a second drive current generation circuit that drives the second drive current control element in accordance with the control current generated by and supplied from the control current generation circuit,

wherein driving of the motor is controlled by controlling the first drive current control element and the second drive current control element that are controlled in accordance with the external current control signal.

According to the present invention, the first drive current generation circuit that drives the first drive current control element and the second drive current generation circuit that drives the second drive current control element are driven by the single control current that is generated by the control current generation circuit in accordance with the external current control signal. Hence, the control current is not varied between the first drive current generation circuit and the second drive current generation circuit. Accordingly, it is possible to accurately and easily control the drive current.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a system configuration diagram of one embodiment of the present invention.

A motor drive system1of this embodiment includes a motor11and a motor drive IC (integrated circuit)12. The motor11is formed by, for example, a three-phase brushless motor, which includes a U-phase coil Lu, a V-phase coil Lv, and a W-phase coil Lw. The U-phase coil Lu, the V-phase coil Lv, and the W-phase coil Lw are connected by star connection, that is, one end of each of the coils is connected to the one end of the others. The other end of the U-phase coil Lu is connected to an output terminal Toutu of the motor drive IC12and a voltage detection terminal Tus. The other end of the V-phase coil Lv is connected to an output terminal Toutv of the motor drive IC12and a voltage detection terminal Tvs. The other end of the W-phase coil Lw is connected to an output terminal Toutw of the motor drive IC12and a voltage detection terminal Tws. In addition, the common connection point of the U-phase coil Lu, the V-phase coil Lv, and the W-phase coil Lw is connected to a voltage detection terminal Tcs of the motor drive IC12.

The motor drive IC12includes a position detection circuit21, a three-phase logic circuit22, a drive circuit23, and a speed control circuit24. The applied voltage of the U-phase coil Lu is supplied to the position detection circuit21from the voltage detection terminal Tus. The applied voltage of the V-phase coil Lv is supplied to the position detection circuit21from the voltage detection terminal Tvs. The applied voltage of the W-phase coil Lw is supplied to the position detection circuit21from the voltage detection terminal Tws. The voltage of the connection point of the U-phase coil Lu, the V-phase coil Lv, and the W-phase coil Lw is applied to the position detection circuit21from the voltage detection terminal Tcs.

The position detection circuit21performs waveform shaping on the voltages from the voltage detection terminals Tus, Tvs, Tws, and Tcs, and supplies the voltages to the three-phase logic circuit22. The three-phase logic circuit22detects the position of a rotor magnet of the motor11based on a detected signal from the position detection circuit21, and generates and supplies, to the drive circuit23, a first U-phase timing control signal and a second U-phase timing control signal that determine the timing at which a current is applied to the U-phase coil Lu, a first V-phase timing control signal and a second V-phase timing control signal that determine the timing at which a current is applied to the V-phase coil Lv, and a first W-phase timing control signal and a second W-phase timing control signal that determine the timing at which a current is applied to the W-phase coil Lw.

It should be noted that the first U-phase timing control signal is a signal for controlling the timing at which a current is supplied to the U-phase coil Lu. The second U-phase timing control signal is a signal for controlling the timing at which a current is drawn from the U-phase coil Lu. The first V-phase timing control signal is a signal for controlling the timing at which a current is supplied to the V-phase coil Lv. The second V-phase timing control signal is a signal for controlling the timing at which a current is drawn from the V-phase coil Lv. The first W-phase timing control signal is a signal for controlling the timing at which a current is supplied to the W-phase coil Lw. The second W-phase timing control signal is a signal for controlling the timing at which a current is drawn from the W-phase coil Lw.

Additionally, a speed instruction signal is supplied to a control terminal Tcnt from an external circuit. In a case where the motor11is a spindle motor of a disk drive, for example, the speed instruction signal is generated by a servo control circuit based on rotation information obtained by reading a disk. In addition, the speed instruction signal is generated by the external circuit based on a reference signal and a FG signal obtained from a FG (frequency generator) sensor that is provided in advance to the motor11. The speed instruction signal supplied to the control terminal Tcnt is supplied to the speed control circuit24inside the motor drive IC12. Power source Vcc is applied to a power source terminal Tvcc. The power source terminal Tvcc is directly connected to the drive circuit23and is also connected to the drive circuit23via a resistance Rf for detecting a drive current (hereinafter referred to as a “resistance Rf”). A current supplied to the drive circuit23via the resistance Rf is used as the drive current for the motor11. The voltage across the resistance Rf is applied to the speed control circuit24. Thus, it is possible to detect a current that flows to the motor11.

The speed control circuit24generates a speed control signal in accordance with the speed instruction signal from the control terminal Tcnt and the voltage across the resistance Rf. The speed control signal is a signal that controls the motor11to be rotated at a rotational speed corresponding to the speed instruction signal. The speed control signal generated by the speed control circuit24is supplied to the drive circuit23.

FIG. 2is a circuit configuration diagram of the drive circuit23. The drive circuit23includes a current control circuit31, a first U-phase drive current control circuit32u, a first V-phase drive current control circuit32v, a first W-phase drive current control circuit32w, a second U-phase drive current control circuit33u, a second V-phase drive current control circuit33v, a second W-phase drive current control circuit33w, a U-phase drive circuit34u, a V-phase drive circuit34v, and a W-phase drive circuit34w. The current control circuit31, the first U-phase drive current control circuit32u, the first V-phase drive current control circuit32v, the first W-phase drive current control circuit32w, the second U-phase drive current control circuit33u, the second V-phase drive current control circuit33v, and the second W-phase drive current control circuit33ware connected to the power source terminal Tvcc. The power source Vcc is supplied from the power source terminal Tvcc. Additionally, the U-phase drive circuit34u, the V-phase drive circuit34v, and the W-phase drive circuit34ware connected to the power source terminal Tvcc via the resistance Rf. The power source voltage Vcc is supplied from the power source terminal Tvcc via the resistance Rf.

The current control circuit31includes a variable current source41, NPN transistors Q11and Q12, and PNP transistors Q13and Q14. The speed control signal is supplied to the variable current source41from the speed control circuit24. The variable current source41outputs a current corresponding to the speed control signal. Each pair of the NPN transistors Q11and Q12, and the PNP transistors Q13and Q14forms a current mirror circuit. The current mirror circuit formed by the NPN transistors Q11and Q12draws from the current mirror circuit formed by the PNP transistors Q13and Q14a current corresponding to the current that is output from the variable current source41. The current mirror circuit formed by the PNP transistors Q13and Q14outputs from the collector of the PNP transistor Q14a current corresponding to the current that is drawn by the current mirror circuit formed by the NPN transistors Q11and Q12, that is, a current corresponding to the speed control signal.

The current output from the collector of the PNP transistor Q14is supplied to the first U-phase drive current control circuit32u, the first V-phase drive current control circuit32v, the first W-phase drive current control circuit32w, the second U-phase drive current control circuit33u, the second V-phase drive current control circuit33v, and the second W-phase drive current control circuit33w. On this occasion, the currents supplied to the first U-phase drive current control circuit32u, the first V-phase drive current control circuit32v, the first W-phase drive current control circuit32w, the second U-phase drive current control circuit33u, the second V-phase drive current control circuit33v, and the second W-phase drive current control circuit33ware all supplied from the collector of the PNP transistor Q14. Accordingly, it is possible to supply a current to each circuit without variation.

The first U-phase drive current control circuit32uis formed by transistors Q21uthrough Q25u. The transistor Q21uis formed by a PNP transistor and constitutes a switch circuit. A current is supplied to the emitter of the transistor Q21ufrom the collector of the PNP transistor Q14. The collector of the transistor Q21uis connected to the collector and base of the transistor Q22uand the base of the transistor Q23u. The first U-phase timing control signal is supplied to the base of the transistor Q21ufrom the three-phase logic circuit22. The transistor Q21uis switched in accordance with the first U-phase timing control signal. When the transistor Q21uis ON, a current is supplied to a current mirror circuit formed by the transistors Q22uand Q23u.

The current mirror circuit formed by the transistors Q22uand Q23udraws from a current mirror circuit formed by the transistors Q24uand Q25ua current corresponding to an emitter current of the transistor Q21u. The current mirror circuit formed by the transistors Q24uand Q25usupplies to the U-phase drive circuit34ua current corresponding to the current drawn by the current mirror circuit formed by the transistors Q22uand Q23u.

It should be noted that the current mirror circuit formed by the transistors Q22uand Q23u, and the current mirror circuit formed by the transistors Q24uand Q25uamplify the current from the current control circuit31and supply the amplified current to the U-phase drive circuit34u.

The second U-phase drive circuit33uis formed by transistors Q31uthrough Q35u. The transistor Q31uis formed by a PNP transistor and constitutes a switch circuit. A current is supplied to the emitter of the transistor Q31ufrom the collector of the transistor Q14. Additionally, the collector of the transistor Q31uis connected to the collector and base of the transistor Q32uand the base of the transistor Q33u. The second U-phase timing control signal is supplied to the base of the transistor Q31ufrom the three-phase logic22. The transistor Q31uis switched in accordance with the second U-phase timing control signal. When the transistor Q31uis ON, a current is supplied to a current mirror circuit formed by the transistors Q32uand Q33u.

The current mirror circuit formed by the transistors Q32uand Q33udraws from a current mirror circuit formed by the transistors Q34uand Q35ua current corresponding to an emitter current of the transistor Q31u. The current mirror circuit formed by the transistors Q34uand Q35usupplies to the U-phase drive circuit34ua current corresponding to the current drawn by the current mirror circuit formed by the transistors Q32uand Q33u.

It should be noted that the current mirror circuit formed by the transistors Q32uand Q33u, and the current mirror circuit formed by the transistors Q34uand Q35uamplify the current from the current control circuit31and supply the amplified current to the U-phase drive circuit34u.

The U-phase drive circuit34includes transistors Q41uand Q42u, and resistances R41uand R42u. The transistors Q41uand Q42uare formed by NPN transistors of an identical polarity. The emitter of the transistor Q41uand the collector of the transistor Q42uare connected in series and the power source voltage is applied across the transistors Q41uand Q42u.

The resistance R41uis connected between the base and emitter of the transistor Q41uand biases the transistor Q41u. A current from the first U-phase drive current control circuit32uis supplied to the base of the transistor Q41u. The transistor Q41uis ON when the current is supplied from the first U-phase drive current control circuit32u, and is OFF when the current from the first U-phase drive current control circuit32uis stopped.

The resistance R42uis connected between the base and emitter of the transistor Q42uand biases the transistor Q42u. A current from the second U-phase drive current control circuit33uis supplied to the base of the transistor Q42u. The transistor Q42uis ON when the current is supplied from the second U-phase drive current control circuit33u, and is OFF when the current from the second U-phase drive current control circuit33uis stopped. The connection point of the emitter of the transistor Q41uand the collector of the transistor Q42uis connected to an output terminal Toutu. The U-phase coil Lu is connected to the output terminal Toutu. A current that flows to the U-phase coil Lu is controlled in accordance with the states of the transistors Q41uand Q42u.

When the transistor Q41uis ON and the transistor Q42uis OFF, a drive current is supplied to the output terminal Toutu. Thus, the drive current is supplied to the U-phase coil Lu. Additionally, when the transistor Q41uis OFF and the transistor Q42uis ON, a current is drawn from the output terminal Toutu. Thus, the current is drawn from the U-phase coil Lu.

It should be noted that the configuration of the first V-phase drive current control circuit32vis the same as that of the above-mentioned first U-phase drive current control circuit32u. Current supply to the V-phase drive circuit34vis controlled by the first V-phase timing control signal. Additionally, the configuration of the second V-phase drive current control circuit33vis the same as that of the second U-phase drive current control circuit33u. Current supply to the V-phase drive circuit34vis controlled by the second V-phase timing control signal.

Further, the configuration of the first W-phase drive current control circuit32wis the same as that of the above-mentioned first U-phase drive current control circuit32u. Current supply to the W-phase drive circuit34wis controlled by the first W-phase timing control signal. Additionally, the configuration of the second W-phase drive current control circuit33wis the same as that of the above-mentioned second U-phase drive current control circuit33u. Current supply to the W-phase drive circuit34wis controlled by the second W-phase timing control signal.

In addition, since the V-phase drive circuit34vand the W-phase drive circuit34whave the same configurations as that of the above-mentioned U-phase drive circuit34, a description thereof is omitted.

Next, a description is given below of operations of the drive circuit23.

FIG. 3is a table for explaining the switching timing of the transistors Q21u, Q21v, Q21w, Q31u, Q31v, and Q31wof the drive circuit23.FIG. 4is a diagram for showing currents that flow to the U-phase coil Lu, the V-phase coil Lv, and the W-phase coil Lw.

During a term T1, the second U-phase timing control signal, the first V-phase timing control signal, the first W-phase timing control signal, and the second W-phase timing control signal are at high levels, and the first U-phase timing control signal and the second V-phase timing control signal are at low levels. Thus, the transistors Q31u, Q21v, Q21w, and Q31ware OFF, and the transistors Q21uand Q31vare ON. Hence, a current flows to the output terminal Toutu, and a current is drawn from the output terminal Toutv. Accordingly, during the term T1, a current flows in the direction indicated by I1inFIG. 4.

During a term T2, the second U-phase timing control signal, the first V-phase timing control signal, the second V-phase timing control signal, and the first W-phase timing control signal are at high levels, and the first U-phase timing control signal and the second W-phase timing control signal are at low levels. Thus, the transistors Q31u, Q21v, Q31v, and Q21ware OFF, and the transistors Q21uand Q31ware ON. Hence, a current flows to the output terminal Toutu, and a current is drawn from the output terminal Toutw. Accordingly, during the term T2, a current flows in the direction indicated by12inFIG. 4.

During a term T3, the first U-phase timing control signal, the second U-phase timing control signal, the second V-phase timing control signal, and the first W-phase timing control signal are at high levels, and the first V-phase timing control signal and the second W-phase timing control signal are at low levels. Thus, the transistors Q21u, Q31u, Q31v, and Q21ware OFF, and the transistors Q21vand Q31ware ON. Hence, a current flows to the output terminal Toutv, and a current is drawn from the output terminal Toutw. Accordingly, during the term T3, a current flows in the direction indicated by I3inFIG. 4.

During a term T4, the first U-phase timing control signal, the second V-phase timing control signal, the first W-phase timing control signal, and the second W-phase timing control signal are at high levels, and the second U-phase timing control signal and the first V-phase timing control signal are at low levels. Thus, the transistors Q21u, Q31v, Q21w, and Q31ware OFF, and the transistors Q31uand Q21vare ON. Hence, a current flows to the output terminal Toutv, and a current is drawn from the output terminal Toutu. Accordingly, during the term T4, a current flows in the direction indicated by I4inFIG. 4.

During a term T5, the first U-phase timing control signal, the first V-phase timing control signal, the second V-phase timing control signal, and the second W-phase timing control signal are at high levels, and the second U-phase timing control signal and the first W-phase timing control signal are at low levels. Thus, the transistors Q21u, Q21v, Q31v, and Q31ware OFF, and the transistors Q31uand Q21ware ON. Hence, a current flows to the output terminal Toutw, and a current is drawn from the output terminal Toutu. Accordingly, during the term T5, a current flows in the direction indicated by I5inFIG. 4.

During a term T6, the first U-phase timing control signal, the second U-phase timing control signal, the first V-phase timing control signal, and the second W-phase timing control signal are at high levels, and the second V-phase timing control signal and the first W-phase timing control signal are at low levels. Thus, the transistors Q21u, Q31u, Q21v, and Q31ware OFF, and the transistors Q31vand Q21ware ON. Hence, a current flows to the output terminal Toutw, and a current is drawn from the output terminal Toutv. Accordingly, during the term T6, a current flows in the direction indicated by I6inFIG. 4. By repeating the above-mentioned operations during the terms T1through T6, a rotating magnetic field is produced among the U-phase coil Lu, the V-phase coil Lv, and the W-phase coil Lw. Thus, the rotor magnet of the motor11is rotated.

According to this embodiment, the first U-phase drive current control circuit32u, the second U-phase drive current control circuit33u, the first V-phase drive current control circuit32v, the second V-phase drive current control circuit33v, the first W-phase drive current control circuit32w, and the second W-phase drive current control circuit33ware all controlled by the output current of the current control circuit31. Hence, the drive current is less likely to be affected by variations in characteristics of the transistors. Additionally, since the same circuit configuration can be used on both source side and sink side, it is possible to reduce variations in characteristics of elements between the source side and the sink side.

Additionally, the transistors of the drive circuit23of this embodiment may be formed by transistors of the reverse polarities.

FIG. 5is a circuit configuration diagram of a first modification of the drive circuit23. InFIG. 5, those parts that are the same as those corresponding parts inFIG. 2are designated by the same reference numerals, and a description thereof is omitted.

In a drive circuit123according to this modification, a current control circuit131, a first U-phase drive current control circuit132u, a second U-phase drive current control circuit133u, a first V-phase drive current control circuit132v, a second V-phase drive current control circuit133v, a first W-phase drive current control circuit132w, a second W-phase drive current control circuit133ware formed by transistors having the polarities opposite to those of the corresponding transistors in the drive circuit23shown inFIG. 2.

The current control circuit131includes transistors Q111through Q114. The transistors Q111and Q112correspond to the transistors Q11and Q12shown inFIG. 2, respectively, and are formed by transistors having the polarity opposite to that of the transistors Q11and Q12. Additionally, the transistors Q113and Q114correspond to the transistors Q13and Q14shown inFIG. 2, respectively, and are formed by transistors having the polarity opposite to that of the transistors Q13and Q14. Further, the polarities of the first U-phase timing control signal, the second U-phase timing control signal, the first V-phase timing control signal, the second V-phase timing control signal, the first W-phase timing control signal, and the second W-phase timing control signal are also reversed.

Additionally, the first U-phase drive current control circuit132uis formed by transistors Q121uthrough Q127u. The transistor Q121ucorresponds to the transistor Q21ushown inFIG. 2, and is formed by a transistor having the polarity opposite to that of the transistor Q21u. The transistors Q122uand Q123ucorrespond to the transistors Q22uand Q23ushown inFIG. 2, respectively, and are formed by transistors having the polarity opposite to that of the transistors Q22uand Q23u. The transistors Q124uand Q125ucorrespond to the transistors Q24uand Q25ushown inFIG. 2, respectively, and are formed by transistors having the polarity opposite to that of the transistors Q24uand Q25u. Further, the transistors Q126uand Q127uconstitute a current mirror circuit for reversing a current.

Additionally, the second U-phase drive current control circuit133uis formed by transistors Q131uthrough Q137u. The transistor Q131ucorresponds to the transistor Q31ushown inFIG. 2, and is formed by a transistor having the polarity opposite to that of the transistor Q31u. The transistors Q132uand Q133ucorrespond to the transistors Q32uand Q33ushown inFIG. 2, respectively, and are formed by transistors having the polarity opposite to that of the transistors Q32uand Q33u. The transistors Q134uand Q135ucorrespond to the transistors Q34uand Q35ushown inFIG. 2, respectively, and are formed by transistors having the polarity opposite to that of the transistors Q34uand Q35u. Further, the transistors Q136uand Q137uconstitute a current mirror circuit for reversing a current.

Further, the configurations of the first V-phase drive current control circuit132vand the first W-phase drive current control circuit132ware the same as that of the first U-phase drive current control circuit132u. The configurations of the second V-phase drive current control circuit133vand the second W-phase drive current control circuit133ware the same as that of the second U-phase drive current control circuit133u.

According to this modification, similar to the drive circuit23shown inFIG. 2, the current control circuit131supplies a current to all of the first U-phase drive current control circuit132u, the first V-phase drive current control circuit132v, the first W-phase drive current control circuit132w, the second U-phase drive current control circuit133u, the second V-phase drive current control circuit133v, and the second W-phase drive current control circuit133w. Accordingly, the drive current is less likely to be affected by variations in the transistors and the like. In addition, since the source side and the sink side can be driven by the circuits having the same configuration, it is possible to reduce variations in characteristics between the source side and the sink side.

Further, in this embodiment, the transistors Q41uand Q42u, Q41vand Q42v, and Q41wand Q42wforming the U-phase drive circuit34u, the V-phase drive circuit34v, and the W-phase drive circuit34w, respectively, are of the same polarity. However, the polarity of the transistors Q41u, Q41v, and Q41wmay be opposite to that of the transistors Q42u, Q42v, and Q42w.

FIG. 6is a circuit configuration diagram of a second modification of the drive circuit23. InFIG. 6, those parts that are the same as those corresponding parts inFIG. 2are designated by the same reference numerals, and a description thereof is omitted.

In a drive circuit223according to this modification, transistors Q241u, Q241v, and Q241wof a U-phase drive circuit234u, a V-phase drive circuit234v, and a W-phase drive circuit234w, respectively, are formed by PNP transistors having the polarity opposite to that of the transistors Q41u, Q41v, and Q41wof the U-phase drive circuit34u, the V-phase drive circuit34v, and the W-phase drive circuit34wshown inFIG. 2, respectively.

Hence, in this modification, a current mirror circuit that is formed by transistors Q226uand Q227uand serves to reverse a current is added to the first U-phase drive current control circuit232u. In addition, similarly, a current mirror circuit that is formed by transistors Q226vand Q227vand serves to reverse a current is added to the first V-phase drive current control circuit232v. Further, a current mirror circuit that is formed by transistors Q226wand Q227wand serves to reverse a current is added to the first W-phase drive current control circuit232w.

Additionally, transistors constituting the drive circuit223may be transistors having the polarities opposite to those of the transistors in the second modification.

FIG. 7is a circuit configuration diagram of a third modification of the drive circuit23. InFIG. 7, those parts that are the same as those corresponding parts inFIGS. 5 and 6are designated by the same reference numerals, and a description thereof is omitted.

The configuration of a drive circuit323according to this modification, which is shown inFIG. 7, is similar to that of the drive circuit123shown inFIG. 5. However, inFIG. 7, the U-phase drive circuit134u, the V-phase drive circuit134v, and the W-phase drive circuit134wof the drive circuit123are replaced by the U-phase drive circuit234u, the V-phase drive circuit234v, and the W-phase drive circuit234w, respectively. Based on this, the configurations of a first U-phase drive current control circuit332u, a first V-phase drive current control circuit332v, and a first W-phase drive current control circuit332ware different from those of the corresponding circuits of the drive circuit123shown inFIG. 5. The first U-phase drive current control circuit332uhas a configuration in which the transistors Q126uand Q127ufor reversing polarity are eliminated from the first U-phase drive current control circuit132ushown inFIG. 5. The first V-phase drive current control circuit332vhas a configuration in which the transistors Q126vand Q127vfor reversing polarity are eliminated from the first V-phase drive current control circuit132vshown inFIG. 5. The first W-phase drive current control circuit332whas a configuration in which the transistors Q126wand Q127wfor reversing polarity are eliminated from the first W-phase drive current control circuit132wshown inFIG. 5.

Additionally, in the above-mentioned embodiment and modifications, the drive circuits23,123,223, and323are applied to the sensor-less three-phase brushless motor. However, each of the above-mentioned drive circuits may also be applied to a motor drive circuit of a motor that detects a rotating position of a rotor by a sensor such as a Hall element.

Further, in the above-mentioned embodiment and modifications, the descriptions are given of the drive circuits23,123,223, and323by taking the thee-phase brushless motor as the example. However, each of the above-mentioned drive circuits may also be used as a circuit for controlling a drive current for an apparatus that is driven by controlling source transistors and sink transistors.

In addition, in the above-mentioned embodiment and modifications, the examples are shown in which the resistance Rf for detecting a current supplied to the motor11is incorporated in the motor drive IC12. However, this is not a limitation, and the resistance Rf may be provided outside the motor drive IC12.

The present application is based on Japanese priority application No. 2003-005873 filed on Jan. 14, 2003, the entire contents of which are hereby incorporated by reference.