JP2015082926A - Current detection circuit and motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current detection circuit capable of highly accurately detecting currents flowing through a switch element without being affected by the individual variations of on-resistance and a motor control device capable of accurately determining an overcurrent state without being affected by the individual variations of the on-resistance.SOLUTION: A current detection circuit 1 configured to detect currents flowing to a switch element Q whose one end S is connected via a wiring member Rp includes: first resistance Rd whose one end is connected to the other end D of the switch element Q; and second resistance Roff whose one end is connected to the other end of the first resistance Rd, and whose other end is grounded. A voltage of a connection point N between the first resistance Rd and the second resistance Roff is output as a detection voltage showing currents flowing to the switch element Q, and the resistance value of the second resistance Roff is a value based on the resistance value of the first resistance Rd, the specification value of the on-resistance of the switch element Q and the measured value of the on-resistance of the switch element Q.

Description

  The present invention relates to a current detection circuit and a motor control device. More specifically, the present invention relates to a current detection circuit that detects a current flowing through a switch element, and a motor control device that converts DC power into AC power using the switch element and controls an AC motor using the AC power.

  2. Description of the Related Art Conventionally, there is known a motor control device that performs rotation control of an AC motor using a full bridge circuit composed of switching elements such as MOSFETs. Patent Document 1 describes a method for detecting whether or not a switch element is in an overcurrent state by using a voltage drop in the switch element.

  Here, the overcurrent state refers to a state in which a current flowing through the switch element (hereinafter also simply referred to as “switch current”) exceeds a predetermined overcurrent detection threshold.

  According to the technique using the above voltage drop, it is possible to determine whether or not an overcurrent state exists without using a current sensor such as a shunt or a Hall element.

  In general, one end of the low-side switch element of the full bridge circuit is grounded via a wiring member such as a wiring pattern of a printed wiring board. Patent Document 2 proposes a current detection circuit that can output the voltage of the switch element without being affected by variations in the resistance value of the wiring member by canceling the voltage drop due to the resistance component of the wiring member.

JP-A-4-308420 JP 2013-70574 A

  By the way, the on-resistance of the switch element varies from individual to individual. The individual variation (initial variation) of the on-resistance is so large that it cannot be ignored. For example, the maximum variation is about ± 20 to 30% at Tj = 25 ° C. Due to this individual variation, there is a problem that the detection accuracy of the switch current is greatly reduced.

  In addition, the motor control device has a problem that it is difficult to accurately determine the overcurrent state due to individual variations in the on-resistance of the switch element.

  Therefore, the present invention provides a current detection circuit that can detect a current flowing through a switch element with high accuracy without being affected by individual variations in on-resistance, and an overcurrent state without being affected by individual variations in on-resistance. It is an object of the present invention to provide a motor control device capable of making a determination.

A current detection circuit according to one embodiment of the present invention includes:
A current detection circuit for detecting a current flowing through a switch element having one end grounded via a wiring member;
A first resistor having one end connected to the other end of the switch element;
A second resistor having one end connected to the other end of the first resistor and the other end grounded;
With
A voltage at a connection point of the first resistor and the second resistor is output as a detection voltage indicating a current flowing through the switch element;
The resistance value of the second resistor is a value based on the resistance value of the first resistor, the specification value of the on-resistance of the switch element, and the actually measured value of the on-resistance of the switch element.
It is characterized by that.

In the current detection circuit,
The resistance value of the second resistor may be a value calculated by Equation (1) based on the resistance value of the wiring member.

  Here, Roff: resistance value of the second resistor, Rp: resistance value of the wiring member, Rd: resistance value of the first resistor, Ron (typ.): Specification value of on-resistance of the switch element, Ron (msd.): An actual measurement value of the on-resistance of the switch element.

In the current detection circuit,
The resistance value of the second resistor may be a value calculated by equation (2).

  Here, Roff: resistance value of the second resistor, Rd: resistance value of the first resistor, Ron (typ.): Specification value of the on-resistance of the switch element, Ron (msd.): The switch element Measured value of on-resistance, n: a number larger than the value obtained by dividing the specified value of on-resistance by the minimum value of on-resistance.

In the current detection circuit,
The actual value of the on-resistance of the switch element is a value obtained by measuring the voltage of the switch element when a predetermined measurement current is passed through the switch element and dividing the measured voltage by the measurement current. May be.

In the current detection circuit,
The voltage of the switch element may be a value measured at the same temperature as the temperature condition of the specification value of the on-resistance of the switch element.

In the current detection circuit,
The value of the combined resistance of the first resistor and the second resistor is a combined resistance of the resistance of the wiring member and the on-resistance of the switch element so as to satisfy a predetermined detection error with respect to the current flowing through the switch element. You may make it large enough compared with a value.

The motor control device according to the first aspect of the present invention includes:
A plurality of pairs of switch elements each having a high side switch element having one end connected to a DC power source and a low side switch element having one end connected to the other end of the high side switch element and the other end grounded via a wiring member A full bridge circuit that converts a DC voltage input from the DC power source into an AC voltage and supplies the AC voltage to the AC motor;
A current detection unit that detects a current flowing through the low-side switch element for each of the plurality of switch element pairs;
An overcurrent determination unit that outputs an overcurrent detection signal when the detection voltage output from the current detection circuit is higher than a reference voltage;
A control unit that outputs a control signal for controlling the high-side switch element and the low-side switch element to a conductive state or a cutoff state;
A signal gate that receives the control signal, outputs the control signal when the overcurrent detection signal is not received, and blocks the control signal when the overcurrent detection signal is received; ,
With
Each of the current detection circuits includes a first resistor having one end connected to one end of the low-side switch element, and a second resistor having one end connected to the other end of the first resistor and the other end grounded. Output a voltage at a connection point of the first resistor and the second resistor as a detection voltage indicating a current flowing through the low-side switch element;
The resistance value of the second resistor is a value based on a resistance value of the first resistor, a specification value of an on-resistance of the switch element, and an actually measured value of the on-resistance of the switch element.

In the motor control device,
The full bridge circuit includes a first switch element pair, a second switch element pair, and a third switch element pair as the plurality of pairs of switch elements,
The current detection unit detects a current flowing through the low-side switch element of the first switch element pair, and detects a current flowing through the low-side switch element of the second switch element pair. Current detection circuit and a third current detection circuit for detecting a current flowing through the low-side switch element of the third switch element pair as the current detection circuit,
The overcurrent determination unit replaces the determination voltage when the detection voltage output from the current detection circuit is higher than a reference voltage with the detection voltage output from each of the first to third current detection circuits. The overcurrent detection signal may be output when an averaged average voltage or a voltage obtained by amplifying the average voltage is higher than a reference voltage.

In the motor control device,
The resistance value of the second resistor may be a value calculated by Expression (3) based on the resistance value of the wiring member.

  Here, Roff: resistance value of the second resistor, Rp: resistance value of the wiring member, Rd: resistance value of the first resistor, Ron (typ): specification value of on-resistance of the switch element, Ron (msd): an actual measured value of the on-resistance of the switch element.

In the motor control device,
The resistance value of the second resistor may be a value calculated by equation (4).

  Here, Roff: resistance value of the second resistor, Rd: resistance value of the first resistor, Ron (typ.): Specification value of the on-resistance of the switch element, Ron (msd.): The switch element Measured value of on-resistance, n: a number larger than the value obtained by dividing the specified value of on-resistance by the minimum value of on-resistance.

In the motor control device,
A temperature detecting means for detecting the temperature of the low-side switch element;
The control unit may input the temperature of the low-side switch element from the temperature detection unit, and output a voltage that increases as the temperature increases to the overcurrent determination unit as the reference voltage.

The motor control device according to the second aspect of the present invention is:
A plurality of pairs of switch elements each having a high side switch element having one end connected to a DC power source and a low side switch element having one end connected to the other end of the high side switch element and the other end grounded via a wiring member A full bridge circuit that converts a DC voltage input from the DC power source into an AC voltage and supplies the AC voltage to the AC motor;
A control signal for controlling the high-side switch element and the low-side switch element to a conductive state or a cut-off state is output, and a reference voltage is generated based on an actually measured value of the on-resistance of the low-side switch element, and the reference voltage is output A control unit,
An overcurrent determination unit that inputs the reference voltage from the control unit and outputs an overcurrent detection signal when a voltage based on a voltage at a connection point between the high-side switch element and the low-side switch element is higher than the reference voltage. When,
A signal gate that receives the control signal, outputs the control signal when the overcurrent detection signal is not received, and blocks the control signal when the overcurrent detection signal is received; ,
It is characterized by providing.

In the motor control device,
The full bridge circuit includes a first switch element pair, a second switch element pair, and a third switch element pair as the plurality of pairs of switch elements,
The overcurrent determination unit includes a first voltage based on a voltage at a connection point between a high-side switch element and a low-side switch element in the first switch element pair, and a high-side switch element and a low-side in the second switch element pair. A second voltage based on a voltage at a connection point of the switch elements, and a third voltage based on a voltage at a connection point between the high-side switch element and the low-side switch element in the third switch element pair; The first voltage, the second voltage, and the third voltage are averaged instead of the determination condition that the voltage based on the voltage at the connection point of the switch element and the low-side switch element is higher than the reference voltage. The overcurrent detection signal is output when the average voltage or the voltage obtained by amplifying the average voltage is higher than the reference voltage. It may be.

In the motor control device,
A temperature detecting means for detecting the temperature of the low-side switch element;
The control unit receives the temperature of the low-side switch element from the temperature detection unit, generates a reference voltage based on the measured value of the temperature and the on-resistance, and outputs the reference voltage to the overcurrent determination unit. It may be.

The motor control device according to the third aspect of the present invention is:
A plurality of pairs of switch elements each having a high side switch element having one end connected to a DC power source and a low side switch element having one end connected to the other end of the high side switch element and the other end grounded via a wiring member A full bridge circuit that converts a DC voltage input from the DC power source into an AC voltage and supplies the AC voltage to the AC motor;
A control unit that outputs a control signal for controlling the high-side switch element and the low-side switch element to a conductive state or a cut-off state, and generates a reference voltage based on an actual measurement value of an on-resistance of the low-side switch element;
With
The control unit receives a voltage based on a voltage at a connection point between the high-side switch element and the low-side switch element, and stops the output of the control signal when the voltage is higher than the reference voltage. And

In the motor control device,
The full bridge circuit includes a first switch element pair, a second switch element pair, and a third switch element pair as the plurality of pairs of switch elements,
The control unit includes a first voltage based on a voltage at a connection point between the high-side switch element and the low-side switch element in the first switch element pair, and a high-side switch element and a low-side switch element in the second switch element pair. A second voltage based on the voltage at the connection point of the first switch and a third voltage based on the voltage at the connection point between the high-side switch element and the low-side switch element in the third switch element pair, and the first voltage A determination condition in which a total voltage obtained by summing the second voltage and the third voltage is calculated, and a voltage based on a voltage at a connection point between the high-side switch element and the low-side switch element is higher than the reference voltage. Alternatively, the output of the control signal may be stopped when the total voltage is higher than the reference voltage.

In the motor control device,
A temperature detecting means for detecting the temperature of the low-side switch element;
The control unit may receive a temperature of the low-side switch element from the temperature detection unit, and generate a reference voltage based on the measured value of the temperature and the on-resistance.

  In the current detection circuit according to the present invention, the resistance value of the second resistor is a value based on the resistance value of the first resistor, the specification value of the on-resistance of the switch element, and the actually measured value of the on-resistance of the switch element. The current detection circuit can output a constant voltage with respect to a predetermined switch current regardless of individual variations in on-resistance of the switch elements.

  Therefore, according to the current detection circuit of the present invention, the current flowing through the switch element can be detected with high accuracy.

  In the motor control device according to the first aspect of the present invention, the current detection circuit according to the present invention detects the current flowing through the low-side switch element of the full bridge circuit, and the detection voltage output from the current detection circuit is higher than the reference voltage. When it is high, the overcurrent determination unit outputs an overcurrent detection signal.

  In the motor control device according to the second aspect of the present invention, the control unit generates a reference voltage based on the actually measured value of the on-resistance of the low-side switch element, and based on the voltage at the connection point between the high-side switch element and the low-side switch element. When the voltage is higher than the reference voltage, the overcurrent determination unit outputs an overcurrent detection signal.

  In the motor control device according to the third aspect of the present invention, the control unit generates a reference voltage based on the actually measured value of the on-resistance of the low-side switch element, and sets the voltage at the connection point of the high-side switch element and the low-side switch element. Based on the input voltage, the output of the control signal is stopped when the voltage is higher than the reference voltage.

  Therefore, according to the motor control devices according to the first to third aspects of the present invention, it is possible to accurately determine the overcurrent state without being affected by the individual variation of the on-resistance of the switch element.

1 is a circuit diagram of a current detection circuit according to a first embodiment of the present invention. (A), (b), and (c) are all diagrams illustrating an operation example of the current detection circuit according to the first embodiment. (A), (b), and (c) are all diagrams illustrating an operation example of the current detection circuit according to the second embodiment of the present invention. It is a flowchart for demonstrating the manufacturing process of the current detection circuit which concerns on one Embodiment of this invention. It is a schematic block diagram of the motor control apparatus which concerns on the 3rd Embodiment of this invention. It is a schematic block diagram of the motor control apparatus which concerns on the 4th Embodiment of this invention. It is a flowchart for demonstrating operation | movement of the motor control apparatus which concerns on 4th Embodiment. It is a schematic block diagram of the motor control apparatus which concerns on the 5th Embodiment of this invention. It is a figure which shows the relationship between a rotor angle and the electricity supply pattern in the case of driving a motor by a 180 degree | times electricity supply system. It is a schematic block diagram of the overcurrent determination part 15B which concerns on this modification of the 3rd and 4th embodiment of this invention.

  Hereinafter, a current detection circuit (first and second embodiments) and a motor control device (third to fifth embodiments) according to the present invention will be described with reference to the drawings.

  In addition, in each figure, the component which has an equivalent function is attached | subjected the same code | symbol, and detailed description of the component of the same code | symbol is not repeated.

(First embodiment)
The current detection circuit 1 according to the first embodiment of the present invention will be described in detail with reference to FIG. The current detection circuit 1 is a current detection circuit that detects a current flowing through the switch element Q.

  As shown in FIG. 1, one end of the switch element Q to be measured for current is grounded via a wiring member. Moreover, the wiring member Rp has a resistance component.

  For example, the switch element Q is a semiconductor switch mounted on a printed wiring board, and one end is installed via a wiring pattern. When the switch element Q is an n-type MOSFET, the source terminal is grounded via the wiring member. In this case, the switch current is the drain current Id.

  As shown in FIG. 1, the current detection circuit 1 includes a first resistor Rd and a second resistor Roff connected in series between the other end (drain terminal) of the switch element Q and the ground. . That is, one end of the first resistor Rd is connected to the other end (drain terminal) of the switch element Q, and one end of the second resistor Roff is connected to the other end of the first resistor Rd, and the other end is grounded. Has been.

  Note that the value of the combined resistance of the first resistor Rd and the second resistor Roff (Rd + Roff) is the combined resistance of the wiring member resistance and the on-resistance of the switch element Q so as to satisfy a predetermined detection error with respect to the switch current. It is preferable that the value (Rp + Ron) is sufficiently large (for example, 10 ^ 5 or more).

  The current detection circuit 1 outputs the voltage at the connection point N of the first resistor Rd and the second resistor Roff as a detection voltage indicating the current flowing through the switch element Q.

  In the current detection circuit 1, variations in voltage drop due to individual variations in on-resistance of the switch element Q are compensated by the second resistor Roff.

  In the first embodiment, in order to compensate for individual variations in on-resistance, the difference between the actually measured value and the specification value of the on-resistance of the switch element Q is assigned to the resistance value of the wiring member. That is, the resistance value of the second resistor Roff is determined by adding the above difference to the resistance value of the wiring member and assuming that the ON resistance of the switch element Q is equal to the specification value.

Specifically, the resistance value of the second resistor Roff is calculated by the following equation (1).

  Here, Roff: resistance value of the second resistor, Rp: resistance value of the wiring member, Rd: resistance value of the first resistor, Ron (typ.): Specification value of the on-resistance of the switch element Q, Ron (msd .): Actual measured value of the on-resistance of the switch element Q.

  As described above, the resistance value of the second resistor Roff includes the resistance value of the first resistor Rd, the specification value Ron (typ.) Of the on-resistance of the switch element Q, and the actual value Ron (msd of the on-resistance of the switch element Q. .) And the resistance value Rp of the wiring member.

  Thereby, the current detection circuit 1 can output a constant voltage with respect to a predetermined switch current without being affected by the individual variation of the on-resistance of the switch element Q.

  Next, an example of the operation of the current detection circuit 1 will be described in detail with reference to FIG. In FIG. 2A, the actual measured value (Ron (msd.)) Of the on-resistance of the switch element Q is 8 mΩ. This resistance value is equal to the specification value (Ron (typ.)) Of the on-resistance of the switch element Q. FIG. 2B shows the case where the actual measured value of on-resistance (Ron (msd.)) Is 6 mΩ, and FIG. 2C shows the case where the actual measured value of on-resistance (Ron (msd.)) Is 10 mΩ. Show.

  2A, 2B, and 2C, the resistance value of the wiring member is 5 mΩ, and the resistance value of the first resistor Rd is 1000Ω.

  If the resistance value of the second resistor Roff is calculated by substituting the above value into the equation (1), it becomes 1600Ω in the case of FIG. 2A, 2666Ω in the case of FIG. 2B, and FIG. ) Is 1142Ω.

  When a current is passed through the switch element Q, the voltage at the drain terminal of the switch element Q varies depending on the on-resistance of the switch element Q. For example, when a current of 100 A is passed through the switch element Q, the voltage at the drain terminal of the switch element Q is 1.3 V in FIG. 2A and 1.1 V in FIG. In the case of c), it becomes 1.5V.

  On the other hand, the value of the output voltage of the current detection circuit 1 (the voltage at the connection point N) is a constant value (in FIG. 2A, FIG. 2B, and FIG. 2C). 0.8V). This output value is equal to the voltage Vds of the switch element Q whose on-resistance is equal to the specification value.

  As described above, the current detection circuit 1 can cancel the voltage drop due to the resistance component of the wiring member and output the voltage Vds of the switch element Q, and regardless of individual variations in the on-resistance of the switch element Q. A constant voltage can be output with respect to a predetermined switch current. In other words, the output voltage of the current detection circuit 1 changes according to the switch current without being influenced by the value of the on-resistance of the switch element Q.

  Therefore, the current detection circuit according to the first embodiment can detect the current flowing through the switch element with high accuracy.

(Second Embodiment)
Next, a current detection circuit according to the second embodiment of the present invention will be described. This embodiment is an embodiment in the case where it is not necessary to cancel the voltage drop due to the resistance component of the wiring member. For example, it is applied when the resistance value of the wiring member is sufficiently smaller than the on-resistance value of the switch element Q.

  Hereinafter, the current detection circuit 1A according to the second embodiment will be described focusing on differences from the first embodiment.

  The configuration of the current detection circuit 1A is the same as that of the above-described current detection circuit 1, and includes a first resistor Rd and a second resistor Roff connected in series between the drain terminal of the switch element Q and the ground. .

  In the second embodiment, the resistance value of the second resistor Roff is determined so that the voltage Vds of the switch element Q is converted to 1 / n times in order to compensate for individual variations in the on-resistance of the switch element Q.

Specifically, the resistance value of the second resistor Roff is calculated by the following equation (2).

  Here, Roff: resistance value of the second resistor, Rd: resistance value of the first resistor, Ron (typ.): Specification value of the ON resistance of the switch element Q, Ron (msd.): ON of the switch element Q Measured value of resistance, n: a number larger than the value obtained by dividing the specified value of on-resistance by the minimum value of on-resistance.

  In other words, the value of n is selected so that the denominator on the right side of Equation (2) is a positive value.

  As described above, the resistance value of the second resistor Roff includes the resistance value of the first resistor Rd, the specification value Ron (typ.) Of the on-resistance of the switch element Q, and the actual value Ron (msd of the on-resistance of the switch element Q. .) And a predetermined number (n).

  Thus, the current detection circuit 1A can output a constant voltage with respect to a predetermined switch current without being affected by individual variations in the on-resistance of the switch element Q.

  Next, an example of the operation of the current detection circuit 1A will be described in detail with reference to FIG. In FIG. 3A, the actual measured value (Ron (msd.)) Of the on-resistance of the switch element Q is 8 mΩ. This resistance value is equal to the specification value (Ron (typ.)) Of the on-resistance of the switch element Q. FIG. 3B shows the case where the actual measured value of on-resistance (Ron (msd.)) Is 6 mΩ, and FIG. 3C shows the case where the actual measured value of on-resistance (Ron (msd.)) Is 10 mΩ. Show.

  In any of the cases of FIGS. 3A, 3B, and 3C, the resistance value of the first resistor Rd is 1000Ω.

  Substituting the above value and n = 2 into equation (2), the resistance value of the second resistor Roff is calculated to be 1000Ω in the case of FIG. 2A and 2000Ω in the case of FIG. 2B. In the case of FIG. 2C, it becomes 666.66Ω. Note that the value of n is selected as a value larger than 1.33 (= 8 mΩ / 6 mΩ), assuming that the minimum value of the on-resistance is 6 mΩ.

  When a current is passed through the switch element Q, the voltage at the drain terminal of the switch element Q varies depending on the on-resistance of the switch element Q. For example, when a current of 100 A is passed through the switch element Q, the voltage at the drain terminal of the switch element Q is 0.8 V in FIG. 3A and 0.6 V in FIG. In the case of c), it becomes 1.0V.

  On the other hand, the value of the output voltage (voltage at the connection point N) of the current detection circuit 1A is a constant value (in FIG. 3 (a), FIG. 3 (b), and FIG. 3 (c)). 0.4V).

  In this way, the current detection circuit 1A can output a constant voltage with respect to a predetermined switch current regardless of individual variations in the on-resistance of the switch element Q. That is, the output voltage of the current detection circuit 1A changes according to the switch current without being influenced by the value of the on-resistance of the switch element Q.

  Therefore, the current detection circuit according to the second embodiment can detect the current flowing through the switch element with high accuracy.

(Manufacturing method of current detection circuits 1 and 1A)
Next, a manufacturing method of the above-described current detection circuits 1 and 1A will be described with reference to the flowchart of FIG.

  First, the switch element Q to be measured is turned on, and a predetermined measurement current (Id) is passed through the switch element Q (step S1).

  Next, the voltage (Vds) between the source and the drain of the switch element Q is measured (step S2). The voltage is measured using a voltmeter or the like connected in parallel to the switch element Q.

  Next, the voltage (Vds) is divided by the measured current (Id) to obtain the actually measured value (Ron (msd.)) Of the on-resistance of the switch element Q (step S3). Thus, the actual measured value of the on-resistance of the switch element Q is a value obtained by measuring the voltage (Vds) of the switch element Q when a predetermined measurement current is passed through the switch element Q and dividing the measured voltage by the measured current. It is.

  Next, the resistance value of the second resistor Roff is calculated (step S4). Specifically, the resistance value of the second resistor Roff is calculated using the above-described equation (1) or equation (2).

  Next, the resistance having the resistance value calculated in step S4 is mounted on the current detection circuit as the second resistance Roff (step S5).

  Note that step S5 may be performed by adjusting the resistance value of the variable resistor connected in advance between the first resistor Rd and the ground to the resistance value calculated in step S4.

  In step S2, the voltage (Vds) of the switch element Q is preferably a value measured at the same temperature as the temperature condition of the on-resistance specification value (Ron (typ.)) Of the switch element Q. As a result, an accurate on-resistance difference (Ron (msd.) − Ron (typ.)) Can be obtained, so that the resistance value of the second resistor Roff can be calculated more accurately.

(Third embodiment)
Next, a motor control device 11 according to a third embodiment of the present invention will be described with reference to FIG. The motor control device 11 according to the present embodiment includes the above-described current detection circuit 1 and corrects individual variations in on-resistance with hardware (first resistor Rd and second resistor Roff).

  The motor control device 11 performs rotation control of a three-phase AC motor (hereinafter also simply referred to as “motor”) 10. The motor 10 is, for example, a starter motor for starting a vehicle engine or a traveling motor for an electric motorcycle.

  In the case of a three-phase brushless motor, the motor 10 includes a stator having U-phase, V-phase, and W-phase coils, and a rotor made of permanent magnets. Three-phase (U, V, W) coils are wound around the stator in order in the circumferential direction.

  As shown in FIG. 5, the motor control device 11 includes a full bridge circuit 12, a signal gate unit 13, a current detection unit 14, an overcurrent determination unit 15, and a control unit 16.

  The full bridge circuit 12 includes high side switch elements Q1, Q2, Q3 and low side switch elements Q4, Q5, Q6. The switch elements Q1 to Q6 are, for example, semiconductor switches (such as n-type MOSFETs) mounted on a printed wiring board. In the following description, the high-side switch element and the low-side switch element are also simply referred to as “switch elements”.

  The full bridge circuit 12 converts the DC voltage input from the DC power supply B into an AC voltage and supplies the AC voltage to the motor 10. The full bridge circuit 12 is, for example, a three-phase bridge circuit including three switch element pairs (first to third switch element pairs), and outputs a three-phase AC voltage. The first to third switch element pairs are connected between the DC power source B and the ground.

  Each switch element pair is composed of one high-side switch element and one low-side switch element.

  The first switch element pair includes a switch element Q1 having one end (drain terminal) connected to the DC power source B, and a switch element Q4 having one end (drain terminal) connected to the other end (source terminal) of the switch element Q1. Have

  Similarly, the second switch element pair includes a switch element Q2 having one end (drain terminal) connected to the DC power source B, and a switch having one end (drain terminal) connected to the other end (source terminal) of the switch element Q2. It has element Q5. The third switch element pair includes a switch element Q3 having one end (drain terminal) connected to the DC power supply B, and a switch element Q6 having one end (drain terminal) connected to the other end (source terminal) of the switch element Q3. Have

  The other ends (source terminals) of the switch elements Q4, Q5 and Q6 are grounded via wiring members Rp1, Rp2 and Rp3, respectively.

  Here, the wiring members Rp1, Rp2, and Rp3 are, for example, wiring patterns of a printed wiring board on which the switch elements Q1 to Q6 are mounted. The resistance value of the wiring pattern varies depending on the arrangement state of the switch elements Q1 to Q6 mounted on the printed wiring board, and varies depending on, for example, the length, width, and thickness of the wiring pattern.

  The signal gate unit 13 receives a control signal (gate signal) from the control unit 16 and receives an overcurrent detection signal from the overcurrent determination unit 15. The control signal is a signal for controlling the high-side switch elements Q1 to Q6 to a conductive state or a cut-off state.

  The signal gate unit 13 outputs a control signal when the overcurrent detection signal is not received, and blocks the control signal when the overcurrent detection signal is received. Therefore, when the overcurrent determination unit 15 outputs an overcurrent detection signal, the control signal is blocked by the signal gate unit 13 and the operation of the full bridge circuit 12 is stopped.

  The signal gate circuit 13 may include a pre-driver circuit that outputs a voltage according to the specifications of the switch elements Q1 to Q6.

  The signal gate unit 13 is configured by, for example, a two-input AND gate (not shown) provided for each of the switch elements Q1 to Q6.

  A first input terminal of the AND gate is connected to the control unit 16 and receives a control signal output from the control unit 16. The second input terminal of the AND gate is connected to the output terminal of the overcurrent determination unit 15 and receives a signal obtained by ORing the output signals of the comparators CP1, CP2, and CP3. The output terminal of the AND gate is connected to the gate terminal of the switch element. In this case, when any one of the switching elements Q1 to Q6 is in an overcurrent state, the signal input to the second input terminal of the AND gate becomes L level, and thus is input to the first input terminal. The control signal is cut off.

  The current detection unit 14 includes a current detection circuit that detects a current flowing through the low-side switch element for each of the first to third switch element pairs. Specifically, as shown in FIG. 5, the current detection unit 14 includes a current detection circuit 1a for the third switch element pair, a current detection circuit 1b for the second switch element pair, and a first switch. And a current detection circuit 1c for element pairs.

  The current detection circuits 1a, 1b, and 1c have the same configuration as that of the current detection circuit 1 described above. That is, the current detection circuit 1a includes a first resistor R1 and a second resistor Ro1 that are connected in series between the drain terminal of the switch element Q6 and the ground. A connection point N1 between the resistor R1 and the resistor Ro1 is an output terminal.

  Similarly, the current detection circuit 1b includes a first resistor R2 and a second resistor Ro2 connected in series between the drain terminal of the switch element Q5 and the ground, and a connection point N2 between the resistor R2 and the resistor Ro2 is Output pin. Similarly, the current detection circuit 1c includes a resistor R3 and a resistor Ro3 connected in series between the drain terminal of the switch element Q4 and the ground. A connection point N3 between the resistor R3 and the resistor Ro3 is an output terminal.

  Current detection circuits 1a, 1b and 1c output voltages at connection points N1, N2 and N3 as detection voltages indicating currents flowing through low-side switch elements Q4, Q5 and Q6, respectively.

  The resistance values of the second resistors Ro1, Ro2, and Ro3 are values calculated using the above equation (1). When it is not necessary to cancel the voltage drop due to the resistance component of the wiring members Rp1, Rp2, and Rp3, the resistance values of the second resistors Ro1, Ro2, and Ro3 are calculated using the above equation (2). Also good.

  The overcurrent determination unit 15 determines whether the switch elements Q4 to Q6 are in an overcurrent state based on the output of the current detection unit 14. More specifically, when the detection voltage output from at least one of the current detection circuits 1a, 1b, and 1c of the current detection unit 14 is higher than the reference voltage, the overcurrent determination unit 15 An overcurrent detection signal is output to the control unit 16.

  The overcurrent determination unit 15 includes, for example, comparators CP1, CP2, and CP3 as shown in FIG. The inverting input terminal (−) of the comparator CP1 is connected to the node N1, and the non-inverting input terminal (+) is connected to the reference voltage VR1. Comparator CP1 outputs an L level signal when the voltage at node N1 is higher than reference voltage VR1.

  Similarly, the inverting input terminal (−) of the comparator CP2 is connected to the connection point N2, and the non-inverting input terminal (+) is connected to the reference voltage VR2. Comparator CP2 outputs an L level signal when the voltage at node N2 is higher than reference voltage VR2.

  Similarly, the inverting input terminal (−) of the comparator CP3 is connected to the connection point N3, and the non-inverting input terminal (+) is connected to the reference voltage VR3. Comparator CP3 outputs an L level signal when the voltage at node N3 is higher than reference voltage VR3.

  As shown in FIG. 5, the output terminals of the comparators CP1, CP2, and CP3 are commonly connected to the signal line OCL to form a wired OR circuit. Therefore, when the output of any of the comparators CP1, CP2 and CP3 becomes L level, the signal line OCL becomes L level.

  Note that the overcurrent detection signal is not necessarily an L level signal. For example, the overcurrent detection signal may be an H level signal by exchanging the connection destinations of the input terminals (+, −) of the comparators CP1, CP2, and CP3.

  The control unit 16 controls the entire motor control device 11 and is configured by, for example, a microcomputer chip. The control unit 16 outputs control signals for the switch elements Q1 to Q6 to the signal gate unit 13. Further, when the overcurrent detection signal is received, the control circuit 16 may turn on the lamp or display an alarm on the display panel in order to notify the user that the overcurrent state is present.

  The motor control device 11 of the present embodiment determines an overcurrent state based on output voltages of the current detection circuits 1a, 1b, and 1c that can detect the current flowing through the switch element with high accuracy.

  Therefore, according to the motor control device according to the third embodiment, it is possible to accurately determine the overcurrent state without being affected by the individual variation in the on-resistance of the switch element.

  Furthermore, in the third embodiment, the individual variations in the on-resistance of the switch element Q are corrected by hardware (current detection circuits 1a, 1b, 1c), and the hardware (comparators CP1, CP2, CP3) Since the current determination is performed, the overcurrent state can be detected quickly.

  Since the on-resistance of the switch element changes depending on the temperature, the overcurrent determination may be performed in consideration of the temperature of the switch element.

  In this case, the motor control device 11 further includes temperature detection means (not shown) for detecting the temperature (case temperature, etc.) of the low-side switch element. This temperature detection means is a thermistor or the like, and may be provided in all of the low-side switch elements Q4, Q5, and Q6, or may be provided in at least one of them.

  The control unit 16 is connected to the temperature detection means and inputs the temperature of the low-side switch element from the temperature detection means.

  Control unit 16 is connected to comparators CP1, CP2 and CP3. That is, the non-inverting input terminals (+) of the comparators CP1, CP2 and CP3 are not grounded via a DC power supply but are connected to the terminal (D / A output terminal or the like) of the control unit 16.

  The control unit 16 outputs reference voltages VR1, VR2, and VR3. More specifically, the control unit 16 outputs a reference voltage corrected based on the temperature of the low-side switch element input from the temperature detection unit as the reference voltage.

  Since the on-resistance of the switch element increases as the temperature increases, the voltage (Vds) of the switch element at a predetermined overcurrent detection threshold (the value of the switch current that is determined to be an overcurrent state) is equal to the increase in on-resistance. Get higher.

  Therefore, the control unit 16 changes the output reference voltage according to the temperature of the switch element. More specifically, the control unit 16 outputs a voltage that increases as the temperature of the low-side switch element increases to the overcurrent determination unit 15 as a reference voltage.

(Fourth embodiment)
Next, a motor control device 21 according to a fourth embodiment of the present invention will be described with reference to FIG. In the motor control device 21 according to the present embodiment, the control unit 16A provides the overcurrent determination unit 15A with reference voltages for the U, V, and W phases based on the actually measured value of the on-resistance of the switch element. Hereinafter, the motor control device 21 according to the present embodiment will be described focusing on the differences from the third embodiment.

  As shown in FIG. 6, the motor control device 21 includes a full bridge circuit 12, a signal gate unit 13, an overcurrent determination unit 15A, a control unit 16A, a temperature detection unit 17, a voltage amplification unit 18, and a storage. Part 19.

  The control unit 16A outputs a control signal for the switch element, and based on the actual measured values of the on-resistances of the low-side switch elements Q4, Q5, and Q6, the reference voltage (U-phase reference voltage, V Phase reference voltage, W phase reference voltage). The reference voltage may be generated in consideration of the resistance values of the wiring members Rp1, Rp2, and Rp3.

  Also, the control unit 16A outputs the generated reference voltage to the overcurrent determination unit 15A. The reference voltage may be output as an analog voltage value from the D / A terminal of the control unit 16A, or output as a PWM signal from the control unit 16A, and the overcurrent determination unit 15A converts the PWM signal into an analog voltage value. It may be converted to a value.

  The overcurrent determination unit 15A receives the reference voltage from the control unit 16A, and outputs an overcurrent detection signal when the voltage based on the voltage at the connection point between the high-side switch element and the low-side switch element is higher than the reference voltage.

  That is, the overcurrent determination unit 15A outputs an overcurrent detection signal when the voltage at the connection point N4 of the high-side switch element Q3 and the low-side switch element Q6 (or a voltage obtained by amplifying the voltage) is higher than the W-phase reference voltage. To do. The overcurrent determination unit 15A outputs an overcurrent detection signal when the voltage at the connection point N5 (or the amplified voltage) of the high-side switch element Q2 and the low-side switch element Q5 is higher than the V-phase reference voltage. To do. The overcurrent determination unit 15A outputs an overcurrent detection signal when the voltage at the connection point N6 of the high-side switch element Q1 and the low-side switch element Q4 (or a voltage obtained by amplifying the voltage) is higher than the U-phase reference voltage. To do.

  Similar to the above-described overcurrent determination unit 15, the overcurrent determination unit 15A is configured using three comparators for each of the U, V, and W phases. For example, the inverting input terminal (−) of the comparator is connected to the output terminal of the voltage amplifier 18, and the non-inverting input terminal (+) is connected to the reference voltage output terminal of the controller 16 </ b> A.

  The temperature detection means 17 detects the temperature (case temperature, etc.) of the low-side switch element. The temperature detection means 17 is a thermistor or the like, and may be provided only in the low side switch element Q4 as shown in FIG. Alternatively, the temperature detection means 17 may be provided in all of the low-side switch elements Q4, Q5, and Q6, or may be provided in at least one of the low-side switch elements Q4, Q5, and Q6.

  The controller 16A inputs the temperature of the low-side switch element from the temperature detection means 17 after the activation. Then, control unit 16A generates a reference voltage based on the input temperature and the actually measured value of on-resistance, and outputs the reference voltage to overcurrent determination unit 15A.

  The voltage amplifier 18 is composed of an operational amplifier or the like, and amplifies each voltage at the connection points N4, N5, and N6. The voltage amplifying unit 18 is not an essential component, and may be deleted when the on-resistance is relatively large.

  The storage unit 19 is, for example, a non-volatile memory (such as an EEPROM), and stores actually measured values of the low-side switch elements Q4, Q5, and Q6. The storage unit 19 may store various conversion tables created based on data learned in advance.

  The conversion table is a later-described temperature-voltage table, on-resistance-temperature table, or the like. The temperature-voltage table is a table in which the temperature of the switch element is associated with the voltage output from the temperature detection means 17. The on-resistance-temperature table is a table in which the on-resistance of the switch element is associated with the temperature of the switch element.

  The signal line ADL is a signal line for transmitting the voltage at the connection points N4, N5, N6 (or the voltage obtained by amplifying the voltage at the connection points N4, N5, N6) to the control unit 16A. Three signal lines ADL are used, one end is connected to the output terminal of the voltage amplifier 18 and the other end is connected to a terminal (A / D input terminal or the like) of the controller 16A. When the voltage amplifier 18 is omitted, one end of each signal line ADL is directly connected to the connection points N4, N5, and N6.

  The select signal line SSL in FIG. 6 has one end connected to the select signal output terminal of the control unit 16A and the other end connected to the select signal input terminal of the changeover switch (not shown) of the voltage amplifier unit 18. This selector switch is a three-input / one-output selector switch that receives a select signal and outputs a signal at an input terminal indicated by the select signal.

  For example, by using two select signal lines SSL, it is possible to specify which of the three inputs of the changeover switch is to be output. Therefore, the signal line ADL is connected to the output terminal of the changeover switch, and the voltage at the connection point of each phase of U, V, W (or the voltage obtained by amplifying the voltage) is connected to the three input terminals, respectively. Only one ADL can be used. Thus, even when the number of A / D input terminals of the control unit 16A is limited and the number of motor phases (three) cannot be secured, the actual measured values of the on-resistance of the low-side switch elements of the U, V, and W phases. Can be input to the control unit 16A.

  Next, the operation of the motor control device 21 will be described with reference to the flowchart of FIG.

  First, the actual measured value (Ron (msd.)) Of the on-resistance of the low-side switch element for each of the U, V, and W phases is learned and stored in the storage unit (step S11). The actual measured value of the on-resistance is obtained in the same manner as in steps S1 to S3 in FIG. The obtained actual measurement value is stored in the storage unit 19. This step is performed, for example, before product shipment (inspection process or the like) of the motor control device 21.

  Next, the temperature of the switch element is detected (step S12). More specifically, the temperature detection means 17 detects the temperature (case temperature or the like) of at least one of the low-side switch elements Q4, Q5, and Q6. The temperature is detected using, for example, a temperature-voltage table stored in advance in the storage unit 19. The controller 16A acquires the current temperature of the switch element using the temperature-voltage table based on the voltage acquired (detected) via the A / D input terminal or the like. Note that the temperature of the switch element may be obtained by calculation using the B constant, not by the temperature-voltage table.

  Next, a reference voltage is generated based on the actually measured value of the on-resistance of the switch element and the temperature of the switch element (step S13). The reference voltage is generated as follows, for example.

  Based on the current temperature obtained in step S12, the on-resistance specification value corresponding to the current temperature of the switch element is obtained using the on-resistance-temperature table. Next, by multiplying this resistance value by Ron (msd.) / Ron (typ.), The current on-resistance value is calculated.

  Next, a reference voltage is calculated from the current value of the on-resistance and a predetermined overcurrent detection threshold value (switch current value determined to be an overcurrent state). For example, when the current on-resistance value is 13.5 mΩ and the overcurrent detection threshold is 100 A, 1.35 V (= 13.5 mΩ × 100 A) is output as the reference voltage.

  Next, the voltage at the connection point (N4, N5, N6) between the high-side switch element and the low-side switch element is compared with the reference voltage (U-phase reference voltage, V-phase reference voltage, W-phase reference voltage) (step S14). ).

  Next, when the voltage at the connection point is higher than the reference voltage, the control signal of the switch element is cut off (step S15). For example, as described in the third embodiment, the control signal is blocked by transmitting an overcurrent detection signal to the signal gate circuit 13.

  As described above, in the motor control device 21 according to the fourth embodiment, the control unit 16A generates the reference voltages for the U, V, and W phases based on the actually measured values of the on-resistances of the switch elements, and the overcurrent The determination unit 15A compares the reference voltage with a voltage based on the voltage at the connection point (the voltage at the connection point or a voltage obtained by amplifying the voltage) to determine whether or not an overcurrent state exists.

  Since the reference voltage based on the actually measured value of the on-resistance is used in this way, according to the motor control device according to the fourth embodiment, the overcurrent state can be accurately determined without being affected by the individual variation of the on-resistance of the switch element. Can be judged.

  Furthermore, the overcurrent state can be more accurately determined by using the reference voltage generated based on the actual measured value of the on-resistance of the switch element and the current temperature of the switch element.

(Modifications of the third and fourth embodiments)
When the three-phase AC motor 10 is driven by a 180-degree energization method, as shown in FIG. 9, there is a timing at which a current flowing through a certain phase coil flows through the other two-phase coils. For example, in the rotor stage 2 (rotor angle 60 ° to 120 °) in FIG. 9, the U-phase high-side switch element (Q1) is in a conductive state, and the V-phase and W-phase low-side switch elements (Q5 and Q6) ) Are both conductive. Therefore, the current that has flowed through the U-phase coil flows in half in the V-phase coil and the W-phase coil.

  In this case, when the overcurrent determination is performed for each phase, the voltage at the connection points N1 and N2 (or connection points N4 and N5) is halved. Cannot detect.

  Therefore, in this modification, an overcurrent determination is performed by comparing a voltage obtained by averaging the voltages of the U, V, and W phases (average voltage) or a voltage obtained by amplifying the average voltage with a reference voltage.

  FIG. 10 shows a schematic configuration of the overcurrent determination unit 15B of this modification.

  The overcurrent determination unit 15B includes a voltage amplification unit 22, a voltage generation unit 23, a comparator CP4 for instantaneous overcurrent determination, and a comparator CP5 for average overcurrent determination.

  The voltage amplification unit 22 includes operational amplifiers 22a, 22b, and 22c, and amplifies the voltage at the connection points N1, N2, and N3 (or N4, N5, and N6).

  The voltage generator 23 generates an average voltage obtained by averaging the output voltages of the operational amplifiers 22a, 22b, and 22c, or a voltage obtained by amplifying the average voltage. As shown in FIG. 10, the output terminals of the operational amplifiers 22a, 22b and 22c are electrically connected via a connection point M via resistors. The voltage at the connection point M is a voltage obtained by averaging the output voltages of the operational amplifiers 22a, 22b, and 22c.

  The voltage generation unit 23 may include operational amplifiers 23a and 23b as illustrated in FIG. The operational amplifier 23a amplifies the voltage at the connection point M and outputs it to the comparator CP4, and the operational amplifier 23b amplifies the voltage at the connection point M and outputs it to the comparator CP5. The operational amplifiers 23a and 23b amplify the input voltage three times, for example. By providing the operational amplifiers 23a and 23b, when the average voltage is small, the influence of noise or the like can be removed and the determination accuracy can be increased. It is not essential to provide the operational amplifiers 23a and 23b.

  The comparator CP4 outputs an L level signal when the output voltage of the operational amplifier 23a is higher than the reference voltage VR4. The response time of a delay circuit (not shown) connected to the input terminal of the comparator CP4 is, for example, several microseconds to several tens of microseconds. For this reason, the comparator CP4 can detect an instantaneous change in the switch current. For example, the comparator CP4 outputs an L level signal when the switch current instantaneously increases to 200 A or more, and notifies the control units 16 and 16A of the overcurrent state.

  The comparator CP5 outputs an L level signal when the output voltage of the operational amplifier 23b is higher than the reference voltage VR5. The response time of a delay circuit (not shown) connected to the input terminal of the comparator CP5 is, for example, several milliseconds to several tens of milliseconds. For this reason, the comparator CP5 can detect an average change in the switch current. For example, the comparator CP5 outputs an L level signal when the switch current rises to 150 A or more on average and notifies the control units 16 and 16A of the overcurrent state.

  Only one of the comparator CP4 and the comparator CP5 may be provided.

  When the operational amplifiers 23a and 23b are not provided, the comparator CP4 and the comparator CP5 output an L level signal when the voltage at the connection point M is higher than the reference voltages VR4 and VR5.

  The signals output from the comparators CP4 and CP5 when the output voltage of the operational amplifiers 23a and 23b or the voltage at the connection point M is higher than the reference voltages VR4 and VR5 are not necessarily L level signals but are H level signals. Also good.

  The input of the overcurrent determination unit 15B is connected to the connection points N1, N2, and N3 of the current detection unit 14 as a modification of the third embodiment, and is a full bridge circuit as a modification of the fourth embodiment. Connected to 12 connection points N4, N5 and N6.

  In the modification of the fourth embodiment, the voltage amplification unit 22 of the overcurrent determination unit 15B performs the same function as the voltage amplification unit 18 described in FIG. Any one of the amplifying units 18 may be provided. Further, the voltage amplifying units 18 and 22 are not essential components, and may be deleted when the on-resistance is relatively large.

  The output of the overcurrent determination unit 15B is connected to the control unit 16 as a modification of the third embodiment, and is connected to the control unit 16A as a modification of the fourth embodiment.

As a modification of the third embodiment, the overcurrent determination unit 15B has an average voltage obtained by averaging the detection voltages output from the current detection circuits 1a, 1b, and 1c, or a voltage obtained by amplifying the average voltage as a reference voltage. If it is higher than that, an overcurrent detection signal is output.
As a modification of the fourth embodiment, the overcurrent determination unit 15B inputs the voltages at the connection points N4, N5, and N6 directly or through the voltage amplification unit 18, and averages the input voltage or When the voltage obtained by amplifying the average voltage is higher than the reference voltage, an overcurrent detection signal is output.

  As described above, in this modification, the overcurrent determination unit 15B performs overcurrent determination by comparing the average voltage obtained by averaging the voltages of the U, V, and W phases or the voltage obtained by amplifying the average voltage with the reference voltage. . For this reason, even when there is a timing when the current flowing through a coil of a certain phase branches and flows into another two-phase coil, such as when a motor is driven by a 180-degree energization method, the overcurrent state is accurately determined. can do.

(Fifth embodiment)
Next, a motor control device 31 according to a fifth embodiment of the present invention will be described with reference to FIG. In the motor control device 31 according to the present embodiment, the control unit 16B determines an overcurrent state of the switch element. Hereinafter, the motor control device 31 according to the present embodiment will be described focusing on differences from the third and fourth embodiments.

  As shown in FIG. 8, the motor control device 31 includes a full bridge circuit 12, a control unit 16B, a temperature detection unit 17, a voltage amplification unit 18, a storage unit 19, and a pre-driver unit 20. .

  The pre-driver circuit 20 amplifies the control signal output from the control unit 16B to a voltage corresponding to the specifications of the switch elements Q1 to Q6, and outputs the amplified voltage.

  The voltage amplifying unit 18 is not an essential component, and may be deleted when the on-resistance is relatively large. The pre-driver unit 20 is not an essential configuration, and can be deleted when the control unit 16B can output voltages according to the specifications of the switch elements Q1 to Q6.

  The control unit 16B outputs a control signal for the switch element, and based on the actual measured values of the on-resistances of the low-side switch elements Q4, Q5, and Q6, the reference voltage for each of the U, V, and W phases (U-phase reference voltage, V Phase reference voltage, W phase reference voltage). The reference voltage may be generated in consideration of the resistance values of the wiring members Rp1, Rp2, and Rp3.

  The control unit 16B inputs a voltage based on the voltage at the connection point between the high-side switch element and the low-side switch element, and stops output of the control signal to the switch elements Q1 to Q6 when the voltage is higher than the reference voltage. To do.

  That is, the control unit 16B stops the output of the control signal when the voltage (or a voltage obtained by amplifying the voltage) at the connection point N4 between the high-side switch element Q3 and the low-side switch element Q6 is higher than the W-phase reference voltage. In addition, the control unit 16B stops outputting the control signal when the voltage at the connection point N5 between the high-side switch element Q2 and the low-side switch element Q5 is higher than the V-phase reference voltage. Further, the control unit 16B stops the output of the control signal when the voltage at the connection point N6 between the high-side switch element Q1 and the low-side switch element Q4 is higher than the U-phase reference voltage.

  Note that the control unit 16B may input the temperature of the low-side switch element from the temperature detection unit 17, generate a reference voltage based on the measured value of the temperature and the on-resistance, and compare the reference voltage with the voltage. Since the method of generating the reference voltage is the same as that of the fifth embodiment, detailed description thereof is omitted.

  As described above, in the motor control device 31 according to the fifth embodiment, the control unit 16B generates the reference voltages for the U, V, and W phases based on the actually measured values of the on-resistances of the switch elements, and A comparison is made between the reference voltage and a voltage based on the voltage at the connection point (the voltage at the connection point or a voltage obtained by amplifying the voltage) to determine whether or not an overcurrent state exists.

  Since the reference voltage based on the actually measured value of the on-resistance is used in this way, according to the motor control device according to the fifth embodiment, the overcurrent state can be accurately determined without being affected by individual variations in the on-resistance of the switch element. Can be judged.

    Furthermore, the overcurrent state can be more accurately determined by using the reference voltage generated based on the actual measured value of the on-resistance of the switch element and the current temperature of the switch element.

(Modification of the fifth embodiment)
As described in the modification examples of the third and fourth embodiments, when the three-phase AC motor 10 is driven by the 180-degree energization method, the low-side switch element of two phases among the U phase, the V phase, and the W phase is provided. There is a timing to become a conductive state. In this case, detection of overcurrent is delayed or overcurrent cannot be detected.

  In order to deal with the above problem, the control unit 16B inputs the voltages at the connection points N4, N5, and N6 (or the voltage obtained by amplifying the voltages at the connection points N4, N5, and N6 by the voltage amplification unit 18), and outputs these voltages. The summed total voltage is calculated, and when the calculated total voltage is higher than a predetermined reference voltage (a reference voltage generated by the control unit 16B), the output of the control signal is stopped. The total voltage is calculated by software executed by the control unit 16B.

  As described above, in the present modification, the control unit 16B performs overcurrent determination by comparing the total voltage obtained by summing the voltages of the U, V, and W phases with the reference voltage. For this reason, even when there is a timing when the current flowing through a coil of a certain phase branches and flows into another two-phase coil, such as when a motor is driven by a 180-degree energization method, the overcurrent state is accurately determined. can do.

  Based on the above description, those skilled in the art may be able to conceive additional effects and various modifications of the present invention, but the aspects of the present invention are not limited to the individual embodiments described above. . You may combine suitably the component covering different embodiment. Various additions, modifications, and partial deletions can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

1, 1A, 1a, 1b, 1c Current detection circuit 10 Three-phase AC motor 11, 21, 31 Motor controller 12 Full bridge circuit 13 Signal gate unit 14 Current detection unit 15, 15A, 15B Overcurrent determination unit 16, 16A, 16B Control unit 17 Temperature detection means 18, 22 Voltage amplification unit 19 Storage unit 20 Pre-driver units 22a, 22b, 22c Operational amplifier 23 Voltage generation unit 23a, 23b Operational amplifier ADL Signal line B DC power supply CP1, CP2, CP3, CP4, CP5 Id Drain current M, N, N1, N2, N3, N4, N5, N6 Connection point OCL Signal line Q Switch element Q1, Q2, Q3 High side switch element Q4, Q5, Q6 Low side switch element Rd, R1, R2, R3 first resistors Roff, Ro1, Ro2, Ro3 second resistors Rp, Rp1, p2, Rp3 wiring member SSL select signal line VR1, VR2, VR3, VR4, VR5 reference voltage

Claims (17)

A current detection circuit for detecting a current flowing through a switch element having one end grounded via a wiring member;
A first resistor having one end connected to the other end of the switch element;
A second resistor having one end connected to the other end of the first resistor and the other end grounded;
With
A voltage at a connection point of the first resistor and the second resistor is output as a detection voltage indicating a current flowing through the switch element;
The resistance value of the second resistor is a value based on the resistance value of the first resistor, the specification value of the on-resistance of the switch element, and the actually measured value of the on-resistance of the switch element.
A current detection circuit. 2. The current detection circuit according to claim 1, wherein the resistance value of the second resistor is a value calculated by Expression (1) based on a resistance value of the wiring member.

Here, Roff: resistance value of the second resistor, Rp: resistance value of the wiring member, Rd: resistance value of the first resistor, Ron (typ.): Specification value of on-resistance of the switch element, Ron (msd.): An actual measurement value of the on-resistance of the switch element. The current detection circuit according to claim 1, wherein the resistance value of the second resistor is a value calculated by Expression (2).

Here, Roff: resistance value of the second resistor, Rd: resistance value of the first resistor, Ron (typ.): Specification value of the on-resistance of the switch element, Ron (msd.): The switch element Measured value of on-resistance, n: a number greater than the value obtained by dividing the specified value of on-resistance by the minimum value of on-resistance   The actual value of the on-resistance of the switch element is a value obtained by measuring the voltage of the switch element when a predetermined measurement current is passed through the switch element and dividing the measured voltage by the measurement current. The current detection circuit according to claim 1, wherein the current detection circuit is a current detection circuit.   The current detection circuit according to claim 4, wherein the voltage of the switch element is a value measured at the same temperature as the temperature condition of the specification value of the on-resistance of the switch element.   The value of the combined resistance of the first resistor and the second resistor is a combined resistance of the resistance of the wiring member and the on-resistance of the switch element so as to satisfy a predetermined detection error with respect to the current flowing through the switch element. The current detection circuit according to claim 1, wherein the current detection circuit is sufficiently larger than the value. A plurality of pairs of switch elements each having a high side switch element having one end connected to a DC power source and a low side switch element having one end connected to the other end of the high side switch element and the other end grounded via a wiring member A full bridge circuit that converts a DC voltage input from the DC power source into an AC voltage and supplies the AC voltage to the AC motor;
A current detection unit that detects a current flowing through the low-side switch element for each of the plurality of switch element pairs;
An overcurrent determination unit that outputs an overcurrent detection signal when the detection voltage output from the current detection circuit is higher than a reference voltage;
A control unit that outputs a control signal for controlling the high-side switch element and the low-side switch element to a conductive state or a cutoff state;
A signal gate that receives the control signal, outputs the control signal when the overcurrent detection signal is not received, and blocks the control signal when the overcurrent detection signal is received; ,
With
Each of the current detection circuits includes a first resistor having one end connected to one end of the low-side switch element, and a second resistor having one end connected to the other end of the first resistor and the other end grounded. Output a voltage at a connection point of the first resistor and the second resistor as a detection voltage indicating a current flowing through the low-side switch element;
The resistance value of the second resistor is a value based on a resistance value of the first resistor, a specification value of an on-resistance of the switch element, and an actually measured value of the on-resistance of the switch element. Control device. The full bridge circuit includes a first switch element pair, a second switch element pair, and a third switch element pair as the plurality of pairs of switch elements,
The current detection unit detects a current flowing through the low-side switch element of the first switch element pair, and detects a current flowing through the low-side switch element of the second switch element pair. Current detection circuit and a third current detection circuit for detecting a current flowing through the low-side switch element of the third switch element pair as the current detection circuit,
The overcurrent determination unit replaces the determination voltage when the detection voltage output from the current detection circuit is higher than a reference voltage with the detection voltage output from each of the first to third current detection circuits. The motor control device according to claim 7, wherein the overcurrent detection signal is output when an averaged average voltage or a voltage obtained by amplifying the average voltage is higher than a reference voltage. 9. The motor control device according to claim 7, wherein the resistance value of the second resistor is a value calculated by Expression (3) based on a resistance value of the wiring member.

Here, Roff: resistance value of the second resistor, Rp: resistance value of the wiring member, Rd: resistance value of the first resistor, Ron (typ): specification value of on-resistance of the switch element, Ron (msd): an actual measured value of the on-resistance of the switch element. 9. The motor control device according to claim 7, wherein the resistance value of the second resistor is a value calculated by an expression (4).

Here, Roff: resistance value of the second resistor, Rd: resistance value of the first resistor, Ron (typ.): Specification value of the on-resistance of the switch element, Ron (msd.): The switch element Measured value of on-resistance, n: a number greater than the value obtained by dividing the specified value of on-resistance by the minimum value of on-resistance A temperature detecting means for detecting the temperature of the low-side switch element;
The said control part inputs the temperature of the said low side switch element from the said temperature detection means, and outputs the voltage which becomes high as the said temperature becomes high to the said overcurrent determination part as the said reference voltage. The motor control apparatus in any one of 7-10. A plurality of pairs of switch elements each having a high side switch element having one end connected to a DC power source and a low side switch element having one end connected to the other end of the high side switch element and the other end grounded via a wiring member A full bridge circuit that converts a DC voltage input from the DC power source into an AC voltage and supplies the AC voltage to the AC motor;
A control signal for controlling the high-side switch element and the low-side switch element to a conductive state or a cut-off state is output, and a reference voltage is generated based on an actually measured value of the on-resistance of the low-side switch element, and the reference voltage is output A control unit,
An overcurrent determination unit that inputs the reference voltage from the control unit and outputs an overcurrent detection signal when a voltage based on a voltage at a connection point between the high-side switch element and the low-side switch element is higher than the reference voltage. When,
A signal gate that receives the control signal, outputs the control signal when the overcurrent detection signal is not received, and blocks the control signal when the overcurrent detection signal is received; ,
A motor control device comprising: The full bridge circuit includes a first switch element pair, a second switch element pair, and a third switch element pair as the plurality of pairs of switch elements,
The overcurrent determination unit includes a first voltage based on a voltage at a connection point between a high-side switch element and a low-side switch element in the first switch element pair, and a high-side switch element and a low-side in the second switch element pair. A second voltage based on a voltage at a connection point of the switch elements, and a third voltage based on a voltage at a connection point between the high-side switch element and the low-side switch element in the third switch element pair; The first voltage, the second voltage, and the third voltage are averaged instead of the determination condition that the voltage based on the voltage at the connection point of the switch element and the low-side switch element is higher than the reference voltage. The overcurrent detection signal is output when the average voltage or the voltage obtained by amplifying the average voltage is higher than the reference voltage. The motor control device according to claim 12, wherein. A temperature detecting means for detecting the temperature of the low-side switch element;
The control unit receives the temperature of the low-side switch element from the temperature detection unit, generates a reference voltage based on the measured value of the temperature and the on-resistance, and outputs the reference voltage to the overcurrent determination unit. The motor control device according to claim 12 or 13, characterized by the above-mentioned. A plurality of pairs of switch elements each having a high side switch element having one end connected to a DC power source and a low side switch element having one end connected to the other end of the high side switch element and the other end grounded via a wiring member A full bridge circuit that converts a DC voltage input from the DC power source into an AC voltage and supplies the AC voltage to the AC motor;
A control unit that outputs a control signal for controlling the high-side switch element and the low-side switch element to a conductive state or a cut-off state, and generates a reference voltage based on an actual measurement value of an on-resistance of the low-side switch element;
With
The control unit receives a voltage based on a voltage at a connection point between the high-side switch element and the low-side switch element, and stops the output of the control signal when the voltage is higher than the reference voltage. A motor control device. The full bridge circuit includes a first switch element pair, a second switch element pair, and a third switch element pair as the plurality of pairs of switch elements,
The control unit includes a first voltage based on a voltage at a connection point between the high-side switch element and the low-side switch element in the first switch element pair, and a high-side switch element and a low-side switch element in the second switch element pair. A second voltage based on the voltage at the connection point of the first switch and a third voltage based on the voltage at the connection point between the high-side switch element and the low-side switch element in the third switch element pair, and the first voltage A determination condition in which a total voltage obtained by summing the second voltage and the third voltage is calculated, and a voltage based on a voltage at a connection point between the high-side switch element and the low-side switch element is higher than the reference voltage. Instead, the output of the control signal is stopped when the total voltage is higher than the reference voltage. The motor control device according to 15. A temperature detecting means for detecting the temperature of the low-side switch element;
17. The motor according to claim 15, wherein the control unit receives the temperature of the low-side switch element from the temperature detection unit, and generates a reference voltage based on the measured value of the temperature and the on-resistance. Control device.

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