Drive circuit

Abstract

To provide a drive circuit capable of reducing a load to be imposed on a switching element.SOLUTION: A drive circuit includes a switching element having a control electrode, a power supply side electrode, and a ground side electrode, a current detection circuit for detecting a drive current flowing through the switching element, a temperature detection circuit for detecting a temperature, and a control circuit for setting the voltage level of the control electrode to a first level such that the current value of the drive current decreases while the drive current continues to flow when the current value of the drive current exceeds a predetermined value. When the temperature exceeds a first temperature while the current value of the drive current exceeds the predetermined value, the control circuit changes the voltage level of the control electrode from the first level to a second level such that the current value of the drive current further decreases while the drive current continues to flow.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a drive circuit. [Background technology]

[0002] For example, there is a drive circuit that controls a drive current flowing through a load to drive the load (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-005862 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the drive circuit may include, for example, a temperature detection circuit that detects temperature. Such a drive circuit stops driving the load when the temperature exceeds a predetermined temperature and reaches an overheated state, and resumes driving the load when the temperature falls below the predetermined temperature.

[0005] However, if the driving of the load is repeatedly stopped and restarted in this manner in accordance with an increase or decrease in temperature near the predetermined temperature, stress is applied to the switching elements included in the driving circuit, raising concerns that the switching elements may be destroyed.

[0006] The present invention has been made in consideration of the above-mentioned problems in the conventional art, and an object of the present invention is to provide a drive circuit capable of reducing the load on a switching element. [Means for solving the problem]

[0007] A first aspect of the drive circuit of the present invention that solves the above-mentioned problems comprises a switching element having a control electrode, a power supply side electrode, and a ground side electrode, a current detection circuit that detects a drive current flowing through the switching element, a temperature detection circuit that detects a temperature, and a control circuit that sets the voltage level of the control electrode to a first level when the current value of the drive current exceeds a predetermined value, so that the current value of the drive current decreases while the drive current continues to flow, and when the temperature exceeds a first temperature while the current value of the drive current exceeds the predetermined value, the control circuit changes the voltage level of the control electrode from the first level to a second level so that the current value of the drive current further decreases while the drive current continues to flow.

[0008] A second aspect of the drive circuit of the present invention that solves the above-mentioned problems comprises a switching element having a control electrode, a power supply side electrode, and a ground side electrode, a current detection circuit that detects a drive current flowing through the switching element, and a control circuit that sets the voltage level of the control electrode to a first level when the current value of the drive current exceeds a predetermined value, so that the current value of the drive current decreases while the drive current continues to flow, and when the period during which the current value of the drive current exceeds the predetermined value reaches a predetermined period, the control circuit changes the voltage level of the control electrode from the first level to a second level so that the current value of the drive current further decreases while the drive current continues to flow. Effect of the Invention

[0009] According to the present invention, it is possible to provide a drive circuit capable of reducing the load on a switching element. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating an example of the configuration of a motor control device 10. FIG. [Diagram 2] FIG. 2 is a diagram showing an example of the configuration of a drive circuit 11a. [Diagram 3] 1 is a diagram showing an example of the relationship between temperature T, voltages Vy, Vz, and voltage V2. [Figure 4] FIG. 4 is a diagram illustrating an example of the operation of the drive circuit 11a. [Diagram 5] FIG. 2 is a diagram showing an example of the configuration of a drive circuit 11b. [Figure 6] FIG. 2 illustrates an example of the configuration of a timer 157. [Figure 7] FIG. 11 is a diagram illustrating an example of the operation of the drive circuit 11b. [Figure 8] FIG. 13 is a diagram showing an example of the configuration of a drive circuit 11c. [Figure 9] FIG. 2 is a diagram showing an example of the configuration of a drive circuit 11d. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] At least the following matters will become apparent from the description of this specification and the accompanying drawings. Preferred embodiments of the present invention will be described below with reference to the drawings. The same or equivalent components, members, etc. shown in each drawing are designated by the same reference numerals, and duplicated descriptions will be omitted as appropriate.

[0012] =====This embodiment===== <<<Overview of Motor Control Device 10>>> FIG 1 is a diagram showing the configuration of a motor control device 10 according to one embodiment of the present invention. The motor control device 10 is a device including a drive circuit 11a and a microcomputer (MCU) 12. The drive circuit 11a controls a load 13, which is a motor provided in an automobile, based on a signal S1 from the microcomputer 12. Specifically, the drive circuit 11a controls, for example, a drive current Idrv flowing through the load 13, which is a motor, based on the signal S1. A power supply voltage Vcc (e.g., 13 V) from a power supply (not shown) is applied to the load 13.

[0013] The drive circuit 11a is a semiconductor module having a control terminal G to which a signal S1 is input, a power supply side terminal D connected to a power supply via a load 13, and a ground side terminal S connected to ground. The power supply side terminal D corresponds to a "first terminal", and the ground side terminal S corresponds to a "second terminal".

[0014] The microcomputer 12 outputs a signal S1 based on an instruction (not shown) input from the outside, and controls the drive circuit 11a.

[0015] <<<Configuration of drive circuit 11a>>> 2 is a diagram showing an example of the configuration of the drive circuit 11a. The drive circuit 11a supplies or stops the drive current Idrv to the load 13 based on a signal S1. Specifically, when a high-level (for example, a voltage level of 5 V, hereinafter referred to as "H" level) signal S1 is output, the drive circuit 11a causes the drive current Idrv to flow through the load 13.

[0016] On the other hand, the drive circuit 11a stops the drive current Idrv flowing to the load 13 when a low-level (for example, a voltage level of 0 V, hereinafter referred to as "L" level) signal S1 is output.

[0017] The drive circuit 11a includes an NMOS transistor 100, diodes 101, 112, and 170, resistors 110, 111, 113, and 130, detection circuits (DET) 120 and 140, a control circuit (CTRL) 150a, and a depletion-type NMOS transistor 160.

[0018] The NMOS transistor 100 has a gate electrode, a drain electrode, and a source electrode, and controls a drive current Idrv flowing through the load 13 based on a voltage Vg applied to the gate electrode. The gate electrode is electrically connected to a control terminal G, the drain electrode is connected to a power supply terminal D, and the source electrode is connected to a ground terminal S. The voltage between the drain electrode and the source electrode of the NMOS transistor 100 is a voltage Vds. In this embodiment, the NMOS transistor is described as an NMOS transistor, but a bipolar transistor may also be used. The NMOS transistor 100 corresponds to a "switching element", the gate electrode corresponds to a "control electrode", the drain electrode corresponds to a "power supply electrode", and the source electrode corresponds to a "ground electrode".

[0019] The diode 101 is a parasitic diode of the NMOS transistor 100 .

[0020] The resistor 110 is a so-called gate resistor, and is provided between a line L1 connected to the control terminal G and a line L2 connected to the gate electrode. In this embodiment, the voltage applied to the line L1 is defined as a voltage V1.

[0021] The resistor 111 is a so-called gate resistor, and is provided between the resistor 110 and the gate electrode. A voltage V2 of the line L2 is applied to one end of the resistor 111. The voltage at the connection point of the resistor 111 and the NMOS transistor 100 is set to a voltage Vg. When an "H" level signal S1 is output, the parasitic capacitance between the gate and source of the NMOS transistor 100 is charged via the resistors 110 and 111.

[0022] The diode 112 is an element through which a current flows when the NMOS transistor 100 is turned off, and is provided in parallel with the resistor 110 together with the resistor 113. Specifically, when an “L” level signal S1 is output, the diode 112 applies a ground level voltage Vg to turn off the NMOS transistor 100, and thus discharges the parasitic capacitance between the gate and source of the NMOS transistor 100 via the resistor 110 and the resistor 111.

[0023] Depending on the resistance values ​​of the resistors 110, 111, and 113, the rate of change per unit time of the voltage Vg can be set separately when the NMOS transistor 100 is turned on or off.

[0024] ==Detection circuit 120== The detection circuit 120 detects the drive current Idrv flowing between the drain electrode and the source electrode of the NMOS transistor 100. Specifically, when the NMOS transistor 100 is turned on, the detection circuit 120 detects the drive current Idrv based on the voltage level of the voltage Vds that is determined according to the product of the on-resistance of the NMOS transistor 100 and the drive current Idrv.

[0025] The detection circuit 120 is a voltage divider circuit consisting of resistors 121 and 122, to which a voltage Vds is applied, and generates a voltage Vx according to the voltage Vds at the connection point of the resistors 121 and 122. The resistance values ​​of the resistors 121 and 122 are set so that when the NMOS transistor 100 is turned on, for example, an inrush current flows from the load 13 (for example, a motor) and the voltage level of the voltage Vds exceeds a predetermined level, the voltage Vx becomes a voltage that turns on the NMOS transistor 154 (described later). In this embodiment, when the voltage Vx becomes a voltage that turns on the NMOS transistor 154, the current value of the drive current Idrv exceeds a predetermined value, and the drive current Idrv is an overcurrent. The detection circuit 120 corresponds to a "current detection circuit."

[0026] Resistor 130 limits the current supplied to a circuit (e.g., inverter circuit 152 (described later)) that operates using voltage Va of line La as a power supply voltage, and has one end connected to line L1 and the other end connected to line La. Note that when a large amount of current flows through resistor 130, voltage Va drops and the operation of the circuit (e.g., inverter circuit 152) is stopped.

[0027] ==Detection circuit 140== The detection circuit 140 detects the temperature T of the drive circuit 11a, and generates a voltage indicating the temperature T. The detection circuit 140 includes a depletion-type NMOS transistor 141 and diodes D1a to D6a.

[0028] The NMOS transistor 141 operates as a current source, its gate electrode and source electrode are connected, a voltage Va is applied to its drain electrode, and a current flows from its source electrode to the diodes D1a to D6a.

[0029] The diodes D1a to D6a are elements that generate a voltage indicative of the temperature T of the drive circuit 11a. Specifically, the diodes D1a to D6a generate a voltage Vy at a connection node N0 between the diodes D1a and D2a, and generate a voltage Vz at a connection node N1 between the NMOS transistor 141 and the diode D1a.

[0030] When the temperature T rises, the voltages Vy and Vz decrease as shown in Fig. 3. Fig. 3 also shows a case where the current value of the drive current Idrv is higher than a predetermined value, and the voltage Vy is indicated by a solid line, and the voltage Vz is indicated by a dashed line. The detection circuit 140 corresponds to a "temperature detection circuit", the NMOS transistor 141 corresponds to a "current source", the diodes D1a to D6a correspond to "k diodes", the node N0 corresponds to a "first node", and the node N1 corresponds to a "second node".

[0031] ==Control circuit 150a== The control circuit 150a controls the voltage V2 of the line L2 based on the drive current Idrv and the temperature T. Specifically, when the current value of the drive current Idrv exceeds a predetermined value, the control circuit 150a sets the voltage level of the voltage Vg to 3.5V so that the drive current Idrv continues to flow while its current value decreases. Here, 3.5V corresponds to the forward voltage generated in the diodes D1b to D5b (described later) and corresponds to the "first level."

[0032] On the other hand, when the temperature T exceeds temperature T1 while the current value of the drive current Idrv exceeds a predetermined value, the control circuit 150a changes the voltage level of the voltage Vg via the line L2 from 3.5V to 2.1V so that the current value of the drive current Idrv further decreases while still flowing. Here, 2.1V corresponds to the forward voltage generated in the diodes D1b to D3b (described later) and corresponds to the "second level."

[0033] When the temperature T exceeds the temperature T2, the control circuit 150a sets the voltage level of the voltage V2 to 0V and the voltage Vg to 0V in order to stop the drive current Idrv.

[0034] The control circuit 150a includes a switch control circuit (SWCT) 151a, NMOS transistors 154 to 156, and diodes D1b to D5b.

[0035] The switch control circuit 151a controls the on / off of the NMOS transistors 155 and 156. Specifically, the switch control circuit 151a turns on the NMOS transistor 155 when the temperature T exceeds a temperature T1, and turns on the NMOS transistor 156 when the temperature T exceeds a temperature T2 that is higher than the temperature T1.

[0036] The switch control circuit 151a includes inverter circuits 152 and 153. The inverter circuit 152 turns on or off the NMOS transistor 155. Specifically, as shown in FIG. 3, when the temperature T exceeds the temperature T1 and the voltage Vy falls below the threshold voltage Vthy, the inverter circuit 152 determines that the temperature T exceeds the temperature T1 and turns on the NMOS transistor 155.

[0037] On the other hand, when the temperature T falls below the temperature T1 and the voltage Vy exceeds the threshold voltage Vthy, the inverter circuit 152 determines that the temperature T falls below the temperature T1 and turns off the NMOS transistor 155. The inverter circuit 152 also operates using the voltage Va as a power supply voltage, and turns off the NMOS transistor 155 when an “L” level signal S1 is input to the control terminal G of the drive circuit 11a.

[0038] 3, when the temperature T exceeds the temperature T2 and the voltage Vz falls below the threshold voltage Vthz, the inverter circuit 153 determines that the temperature T exceeds the temperature T2 and turns on the NMOS transistor 156.

[0039] On the other hand, when the temperature T falls below the temperature T2 and the voltage Vz exceeds the threshold voltage Vthz, the inverter circuit 153 determines that the temperature T falls below the temperature T2, and turns off the NMOS transistor 156. The inverter circuit 153 also operates using the voltage Va as a power supply voltage, and turns off the NMOS transistor 156 when an “L” level signal S1 is input to the control terminal of the drive circuit 11a.

[0040] In FIG. 3, the threshold voltages Vthy and Vthz are depicted as the same voltage, but the threshold voltages Vthy and Vthz may be different threshold voltages while maintaining the relationship of T1 < T2. Also, in this embodiment, the inverter circuits 152 and 153 are used to determine the temperature T, but in this case, a comparator may be used instead of the inverter circuits 152 and 153.

[0041] If a comparator is used, instead of using the voltages Vy and Vz, the voltage level of the voltage Vz may be compared with the two threshold voltages Vthy and Vthz to determine whether the temperature T has reached the temperature T1 or T2. Also, the threshold voltage Vthy corresponds to the "third level", and the threshold voltage Vthz corresponds to the "fourth level".

[0042] The NMOS transistor 154 is an element that is turned on when the drive current Idrv exceeds a predetermined value and controls the voltage V2 of the line L2 by the diodes D1b to D5b. The NMOS transistor 154 is provided between the diodes D1b to D5b and the source electrode of the NMOS transistor 100. Specifically, the NMOS transistor 154 is turned on when the voltage Vx generated by the detection circuit 120 exceeds the threshold voltage Vthx of the NMOS transistor 154. At this time, the NMOS transistor 154 detects that the drive current Idrv is an overcurrent.

[0043] Note that the voltage division ratio of the resistors 121 and 122 of the detection circuit 120 is set such that when the voltage level of the voltage Vds exceeds a predetermined level, the voltage Vx exceeds the threshold voltage Vthx and the NMOS transistor 154 is turned on. Thereby, when the voltage level of the voltage Vds exceeds a predetermined level and the current value of the drive current Idrv exceeds a predetermined value, as shown in FIG. 3, the voltage level of the voltage V2 becomes, for example, 3.5V, and the voltage level of the voltage Vg also becomes 3.5V. Also, the NMOS transistor 154 corresponds to the "first switch".

[0044] The NMOS transistor 155 is an element that detects whether or not the temperature T is higher than the temperature T1, and is connected in parallel to the diodes D4b and D5b. Specifically, the NMOS transistor 155 is turned on when the temperature T exceeds the temperature T1. As a result, when the temperature T exceeds the temperature T1 with the current value of the drive current Idrv exceeding a predetermined value, the voltage level of the voltage V2 becomes, for example, 2.1 V, and the voltage level of the voltage Vg becomes 3.5 V to 2.1 V, as shown in FIG. 3. The NMOS transistor 155 corresponds to a "second switch."

[0045] The NMOS transistor 156 is an element that detects whether or not the temperature T is higher than the temperature T2, and is provided between the line L2 and the source electrode. Specifically, when the temperature T exceeds the temperature T2, the NMOS transistor 156 is turned on, and the voltage Vg is set to 0 V via the line L2. Then, the NMOS transistor 156 turns off the NMOS transistor 100, and stops the drive current Idrv. The NMOS transistor 156 corresponds to a "third switch."

[0046] The diodes D1b to D5b control the voltage V2 of the line L2 based on the drive current Idrv and the temperature T, and are connected in series to the line L2. Specifically, when the current value of the drive current Idrv exceeds a predetermined value, the diodes D1b to D5b set the voltage level of the voltage V2 of the line L2 to a voltage (e.g., 3.5V) obtained by summing the forward voltages of the diodes D1b to D5b. At this time, the voltage level of the voltage Vg becomes 3.5V.

[0047] Furthermore, when the temperature T exceeds temperature T1 while the current value of the drive current Idrv exceeds a predetermined value, the diodes D1b to D5b set the voltage V2 of the line L2 to a voltage (e.g., 2.1 V) obtained by summing the forward voltages of the diodes D1b to D3b. At this time, the voltage level of the voltage Vg becomes 2.1 V.

[0048] In this way, when the current value of the drive current Idrv exceeds a predetermined value, the voltage Vg is set to 3.5 V, and when the temperature T exceeds temperature T1, the voltage level of the voltage Vg is reduced from 3.5 V to 2.1 V, thereby reducing the current value of the drive current Idrv.

[0049] This can prevent the temperature T from rising further. Therefore, the temperature T is prevented from exceeding the temperature T2, and as a result, the NMOS transistor 100 is prevented from being repeatedly turned on and off in an overheated state due to the temperature T rising or falling near the temperature T2. The five diodes D1b to D5b correspond to "n diodes", the temperature T1 corresponds to the "first temperature", and the temperature T2 corresponds to the "second temperature". In the present embodiment, the number of diodes D1b to D5b connected in series is five, but this is not limited to this.

[0050] The NMOS transistor 160 passes a current from the line L2 to the source electrode of the NMOS transistor 100. Specifically, the NMOS transistor 160 is a depletion-type NMOS transistor provided between the line L2 and the source electrode of the NMOS transistor 100, with its gate electrode and source electrode connected.

[0051] In addition, by allowing the NMOS transistor 160 to pass a current, it is possible to prevent the NMOS transistor 100 from being erroneously turned on when no voltage is applied to the control terminal G and the control terminal G is in an open state.

[0052] The diode 170 is an element that protects the control terminal G, and has an anode connected to the source electrode of the NMOS transistor 100 and a cathode connected to the control terminal G.

[0053] <<<Operation of drive circuit 11a>>> 4 is a diagram showing an example of the operation of the drive circuit 11a. At time t0, when an "H" level signal S1 is output, the NMOS transistor 100 is turned on. Then, when the current value of the drive current Idrv exceeds a predetermined value and the voltage Vx according to the voltage Vds exceeds the threshold value Vthx, the NMOS transistor 154 is turned on, and the diodes D1b to D5b set the voltage level of the voltage V2 to 3.5V. Then, the voltage level of the voltage Vg becomes 3.5V.

[0054] As a result, the current value of the drive current Idrv decreases, and the voltage Vds decreases, causing the voltage Vx to decrease; however, the voltage Vx is still higher than the threshold voltage Vthx, and the current value of the drive current Idrv exceeds a predetermined value, resulting in an overcurrent state.

[0055] At time t1, when the temperature T rises and exceeds the temperature T1 while the drive current Idrv is in an overcurrent state, the voltage Vy falls below the threshold voltage Vthy. Then, the inverter circuit 152 outputs an “H” level signal, the NMOS transistor 155 is turned on, and the diodes D1b to D5b set the voltage level of the voltage V2 to 2.1 V. Then, the voltage level of the voltage Vg changes from 3.5 V to 2.1 V.

[0056] As a result, the current value of the drive current Idrv further decreases and the voltage Vx decreases, but the voltage Vx is still higher than the threshold voltage Vthx, the current value of the drive current Idrv exceeds the predetermined value, and the drive current Idrv is an overcurrent.

[0057] However, since the current value of the drive current Idrv has been decreasing since time t0, the increase in temperature T is reduced. Therefore, after time t1, the temperature T is prevented from exceeding temperature T2. However, in order to explain the operation of the drive circuit 11a, the following explanation will be given assuming that the temperature T exceeds temperature T2.

[0058] At time t2, when temperature T exceeds temperature T2, inverter circuit 153 outputs an “H” level signal, turning on NMOS transistor 156. When NMOS transistor 156 is turned on, the voltage level of voltage V2 becomes 0V, and the voltage level of voltage Vg also becomes 0V.

[0059] As a result, the drive current Idrv is stopped and the voltage Vds becomes the power supply voltage Vcc by turning off the NMOS transistor 100. In addition, the voltage Vx becomes a voltage according to the power supply voltage Vcc because the NMOS transistor 100 is turned off.

[0060] At time t3, for example, when the temperature T becomes lower than the temperature T2 due to the influence of the ambient temperature of the drive circuit 11a, the NMOS transistor 156 is turned off. Even if the NMOS transistor 156 is turned off, if the current value of the drive current Idrv exceeds a predetermined value and the temperature T exceeds the temperature T1, the voltage level of the voltage V2 becomes 2.1 V, and the voltage level of the voltage Vg also becomes 2.1 V. Note that the same operation continues after time t3.

[0061] Then, at time t7, when the signal S1 is output at the "L" level, the NMOS transistor 100 is turned off. When the NMOS transistor 100 is turned off, the voltage Vx becomes a voltage according to the power supply voltage Vcc.

[0062] In FIG. 4, a case has been described in which the current value of the drive current Idrv exceeds a predetermined value, resulting in an overcurrent state. However, when the drive current Idrv is not in an overcurrent state, the NMOS transistor 154 is off, and therefore the control circuit 150a does not control the voltage V2 of the line L2.

[0063] Therefore, when an "H" level signal S1 is output to the control terminal G, the voltage level of the voltage Vg becomes, for example, 5 V, and the NMOS transistor 100 turns on. On the other hand, when an "L" level signal S1 is output to the drive terminal G, the voltage level of the voltage Vg becomes 0 V, and the NMOS transistor 100 turns off.

[0064] Furthermore, in a state where an “H” level signal S1 is output to the control terminal G, if the temperature T reaches temperature T1 and then drops, and the current value of the drive current Idrv exceeds a predetermined value, the control circuit 150a sets the voltage level of the voltage V2 on the line L2 to 3.5 V. Similarly, regardless of the voltage level of the voltage V2, if the current value of the drive current Idrv falls below a predetermined value, the voltage level of the voltage V2 becomes 5 V.

[0065] === Variations === <<<Configuration of drive circuit 11b>>> 5 is a diagram showing an example of the configuration of the drive circuit 11b. The drive circuit 11b differs from the drive circuit 11a in that the drive circuit 11b turns on an NMOS transistor 155 based on the voltage Vx.

[0066] The drive circuit 11b includes an NMOS transistor 100, diodes 101, 112, and 170, resistors 110, 111, 113, and 130, detection circuits 120 and 140, a control circuit 150b, and a depletion-type NMOS transistor 160.

[0067] The control circuit 150b controls the voltage level of the voltage V2 of the line L2 based on the drive current Idrv and the temperature T. Specifically, when the current value of the drive current Idrv exceeds a predetermined value, the control circuit 150b reduces the voltage level of the voltage V2 so that the drive current Idrv continues to flow while the current value decreases, and sets the voltage level of the voltage Vg to 3.5V.

[0068] On the other hand, when a predetermined period P has elapsed with the current value of the drive current Idrv exceeding a predetermined value, the control circuit 150b reduces the voltage level of voltage V2 so that the drive current Idrv continues to flow while its current value further decreases, and changes the voltage level of voltage Vg from 3.5V to 2.1V.

[0069] When the temperature T exceeds the temperature T2, the control circuit 150b sets the voltage level of the voltage V2 to 0V and the voltage level of the voltage Vg to 0V in order to stop the drive current Idrv.

[0070] The control circuit 150b includes a switch control circuit 151b, NMOS transistors 154 to 156, and diodes D1b to D5b.

[0071] When the period during which the current value of the drive current Idrv exceeds a predetermined value reaches a predetermined period P, the switch control circuit 151b turns on the NMOS transistor 155. The switch control circuit 151b includes inverter circuits 152 and 153 and a timer 157.

[0072] 6 is a diagram showing an example of the configuration of the timer 157. The timer (TMR) 157 outputs a voltage Vy to the inverter circuit 152 based on the voltage Vx. Specifically, when an "H" level signal S1 is output, the timer 157 outputs a voltage Vy that turns on the NMOS transistor 155 when the period during which the current value of the drive current Idrv exceeds a predetermined value becomes a predetermined period P.

[0073] The timer 157 includes a discharge circuit (DCHG) 200, a resistor 201, a capacitor 202, and an exclusive OR circuit 203.

[0074] When the “H” level signal S1 is output, the discharge circuit 200 discharges the capacitor 202 during the reset period Prst. The discharge circuit 200 includes a resistor 210, a capacitor 211, an inverter circuit 212, an AND circuit 213, and an NMOS transistor 214.

[0075] A current flows through the resistor 210 to charge the capacitor 211 when the signal S1 at the “H” level is output.

[0076] When an "H" level signal S1 is output, the capacitor 211 is charged via the resistor 210. On the other hand, when an "L" level signal S1 is output, the capacitor 211 is discharged via the resistor 210. The voltage generated in the capacitor 211 is designated as voltage Vq.

[0077] When the reset period Prst has elapsed since the “H” level signal S1 was output, and the voltage Vq exceeds the threshold voltage of the inverter circuit 212, the inverter circuit 212 outputs the voltage Vr, which is the ground voltage. On the other hand, when the voltage Vq falls below the threshold voltage of the inverter circuit 212, the inverter circuit 212 outputs the voltage Vr, which is the voltage Va.

[0078] When the “H” level signal S1 is output, the AND circuit 213 outputs a voltage Vs which is the voltage Va based on the voltage V1 of, for example, 5V and the voltage Vr which is the voltage Va, and turns on the NMOS transistor 214.

[0079] On the other hand, the AND circuit 213 turns off the NMOS transistor 214 when the signal S1 of the "L" level is output or when the inverter circuit 212 outputs the voltage Vr which is the ground voltage after the reset period Prst has elapsed.

[0080] Therefore, during the period from when the "H" level signal S1 is output until the reset period Prst has elapsed, the NMOS transistor 214 is turned on and the capacitor 202 is discharged. On the other hand, when the reset period Prst has elapsed from when the "H" level signal S1 is output, the NMOS transistor 214 is turned off and the capacitor 202 is charged via the resistor 201. The resistor 201 corresponds to a "charging circuit."

[0081] Furthermore, the voltage Vp generated by the capacitor 202 exceeds the threshold voltage Vthp when the charging period Pchg has elapsed since the capacitor 202 started to be charged via the resistor 201. On the other hand, the voltage Vp is less than the threshold voltage Vthp before the charging period Pchg has elapsed. The reset period Prst corresponds to the "first period", and the charging period Pchg corresponds to the "second period".

[0082] The exclusive OR circuit 203 outputs a voltage Vy based on the voltage Vp generated in the capacitor 202 and the voltage Vx. Specifically, even if the current value of the drive current Idrv exceeds a predetermined value, the exclusive OR circuit 203 outputs the voltage Vy which is equal to the voltage Va while the voltage Vp does not exceed the threshold voltage Vthp, and turns off the NMOS transistor 155.

[0083] On the other hand, when the signal S1 of the "L" level is output, or when the voltage Vp exceeds the threshold voltage Vthp while the current value of the drive current Idrv remains above the predetermined value, the exclusive OR circuit 203 outputs the voltage Vy, which is the ground voltage. Also, when the current value of the drive current Idrv falls below the predetermined value, the exclusive OR circuit 203 outputs the voltage Vy, which is the ground voltage. Then, the NMOS transistor 155 is turned on.

[0084] That is, when the voltage Vx is higher than the threshold voltage Vthx and the voltage Vp is lower than the threshold voltage Vthp, or when the voltage Vx is lower than the threshold voltage Vthx and the voltage Vp is higher than the threshold voltage Vthp, the exclusive OR circuit 203 outputs the voltage Vy which is the voltage Va. Then, the NMOS transistor 155 is turned off.

[0085] Moreover, the exclusive OR circuit 203 outputs the voltage Vy, which is the ground voltage, when the voltage Vx is higher than the threshold voltage Vthx and the voltage Vp is higher than the threshold voltage Vthp, or when the voltage Vx is lower than the threshold voltage Vthx and the voltage Vp is lower than the threshold voltage Vthp. Then, the NMOS transistor 155 is turned on. The exclusive OR circuit 203 corresponds to an "ON circuit."

[0086] Furthermore, when the signal S1 is at the "L" level, the drive current Idrv is stopped and the NMOS transistor 154 is turned off, so that even if the NMOS transistor 155 is turned on, there is no effect on the voltage level of the voltage V2 on the line L2. Similarly, when the current value of the drive current Idrv falls below a predetermined value, the NMOS transistor 154 is turned off, so that the diodes D1b to D5b do not affect the voltage V2 on the line L2, and there is no problem even if the NMOS transistor 155 is turned on.

[0087] From the above operation, the timer 157 turns on the NMOS transistor 155 when the period during which the current value of the drive current Idrv exceeds a predetermined value becomes the predetermined period P after the signal S1 of the "H" level is output.

[0088] The reason for this operation is that when the NMOS transistors 154 and 155 are turned on immediately after the "H" level signal S1 is output, the voltage V2 on the line L2 may become 2.1 V, which is close to the threshold voltage (e.g., 2.0 V) of the NMOS transistor 100. In this case, there is a possibility that the NMOS transistor 100 will not be turned on.

[0089] On the other hand, since the timer 157 keeps the NMOS transistor 155 off until the reset period Prst has elapsed, even if the NMOS transistor 154 is turned on immediately after the “H” level signal S1 is output, the phenomenon in which the NMOS transistor 100 is not turned on is suppressed.

[0090] This is because even if the NMOS transistor 154 is turned on, the voltage level of the voltage V2 is 3.5V, which is sufficiently higher than the threshold voltage of the NMOS transistor 100, 2.0V.

[0091] Furthermore, when a predetermined period P has elapsed since the signal S1 of the “H” level was output while the current value of the drive current Idrv remained above a predetermined value, the control circuit 150b changes the voltage level of the voltage Vg from 3.5 V to 2.1 V. Note that the predetermined period P includes the reset period Prst and the charging period Pchg.

[0092] In this way, the drive circuit 11b can prevent the temperature T from exceeding the temperature T2 by lowering the current value of the drive current Idrv in two stages, and can prevent the NMOS transistor 100 from being continuously turned on and off near the temperature T2. This can reduce the load on the NMOS transistor 100.

[0093] <<<Operation of drive circuit 11b>>> 7 is a diagram showing an example of the operation of the drive circuit 11b. In FIG 7, times t13 to t18 correspond to times t2 to t7 in FIG 4, respectively.

[0094] At time t10, when an "H" level signal S1 is output, the NMOS transistor 100 is turned on. Then, when the current value of the drive current Idrv exceeds a predetermined value and the voltage Vx according to the voltage Vds exceeds the threshold value Vthx, the NMOS transistor 154 is turned on, and the diodes D1b to D5b set the voltage level of the voltage V2 to 3.5V. Then, the voltage level of the voltage Vg becomes 3.5V.

[0095] At this time, since the capacitor 211 of the timer 157 has not yet been charged, the voltage Vq is low, and the inverter circuit 212 outputs the voltage Vr, which is the voltage Va. Then, the AND circuit 213 turns on the NMOS transistor 214 based on the voltage V1 and the voltage Vr.

[0096] When the NMOS transistor 214 is turned on, the capacitor 202 is discharged, so that even if the current value of the drive current Idrv exceeds a predetermined value, the voltage Vp remains low. Therefore, the exclusive OR circuit 203 outputs the voltage Vy, which is the voltage Va, and the NMOS transistor 155 is turned off.

[0097] As a result, the voltage level of the voltage V2 on the line L2 remains reduced to 3.5V.

[0098] At time t11 when the reset period Prst has elapsed from time t10, the capacitor 211 is charged, and when the voltage Vq exceeds the threshold voltage of the inverter circuit 212, the inverter circuit 212 outputs the voltage Vr which is the ground voltage.

[0099] The AND circuit 213 outputs the voltage Vs, which is the ground voltage, based on the voltage V1, which is 5 V, and the voltage Vr, which is the ground voltage, and turns off the NMOS transistor 214. When the NMOS transistor 214 is turned off, the capacitor 202 starts to be charged with the voltage Vx via the resistor 201, and the voltage Vp starts to rise.

[0100] At time t12 when the charging period Pchg has elapsed since time t11 and the voltage Vp becomes the threshold voltage Vthp, the exclusive-OR circuit 203 outputs the voltage Vy, which is the ground voltage, based on the voltages Vx and Vp, and turns on the NMOS transistor 155. When the NMOS transistor 155 is turned on, the control circuit 150b sets the voltage level of the voltage V2 on the line L2 to 2.1V.

[0101] As a result, the current value of the drive current Idrv further decreases and the voltage Vx decreases, but the voltage Vx is still higher than the threshold voltage Vthx and the current value of the drive current Idrv exceeds the predetermined value.

[0102] However, since the current value of the drive current Idrv has been decreasing since time t10, the increase in temperature T is reduced. Therefore, after time t12, the temperature T is prevented from exceeding the temperature T2. This reduces the load on the NMOS transistor 100.

[0103] <<<Configuration of drive circuit 11c>>> 8 is a diagram showing an example of the configuration of the drive circuit 11c. The drive circuit 11c is a drive circuit in which the detection circuit 120 of the drive circuit 11a is replaced with a detection circuit (DET) 300.

[0104] The detection circuit 300 detects the drive current Idrv, and includes an NMOS transistor 301 and a resistor 302. The NMOS transistor 301 is an element through which a current flows that is smaller than the drive current Idrv in response to the drive current Idrv flowing through the NMOS transistor 100. A voltage Vg is applied to a gate electrode of the NMOS transistor 301, and a drain electrode and a source electrode are connected to the drain electrode and source electrode of the NMOS transistor 100, respectively.

[0105] The current flowing through the NMOS transistor 301 flows through the resistor 302, and a voltage Vx is generated at the connection node between the NMOS transistor 301 and the resistor 302 in accordance with the flowing current.

[0106] When an “H” level signal S1 is output, the NMOS transistor 301 is turned on in the same manner as the NMOS transistor 100 is turned on. Then, the resistor 302 generates a voltage Vx based on the current flowing through the NMOS transistor 301.

[0107] In addition, when the voltage level of the voltage V2 on the line L2 is controlled by the control circuit 150a, the voltage Vg changes accordingly, the NMOS transistors 100 and 301 are put into the same operating state, and a current corresponding to the drive current Idrv flowing through the NMOS transistor 100 flows through the NMOS transistor 301.

[0108] On the other hand, when an “L” level signal S1 is output, the NMOS transistor 301 is turned off in the same manner as the NMOS transistor 100. Then, since no current flows through the NMOS transistor 301, the resistor 302 generates the voltage Vx, which is the ground voltage.

[0109] <<<Configuration of drive circuit 11d>>> 9 is a diagram showing an example of the configuration of a drive circuit 11d. The drive circuit 11d is a drive circuit in which the detection circuit 120 of the drive circuit 11b is replaced with a detection circuit 300. The detection circuit 300 operates as described above, and therefore a description thereof will be omitted. ===Summary=== The motor control device 10 of this embodiment has been described above. The drive circuit 11a includes an NMOS transistor 100, detection circuits 120 and 140, and a control circuit 150a. The control circuit 150a controls the voltage level of the voltage Vg to one of 5V, 3.5V, and 2.1V based on the drive current Idrv and the temperature T. In addition, when the current value of the drive current Idrv exceeds a predetermined value, the control circuit 150a first controls the voltage level of the voltage Vg to 3.5V, and when the overcurrent state continues and the temperature T becomes temperature T1, the control circuit 150a next controls the voltage level of the voltage Vg to 2.1V. In this way, when the drive current Idrv becomes an overcurrent, the voltage level of the voltage Vg is changed stepwise to gradually reduce the current value of the drive current Idrv, thereby preventing the temperature T from becoming higher than the temperature T1. This makes it possible to provide a drive circuit that can reduce the load on the switching element.

[0110] The control circuit 150a also includes diodes D1b-D5b, NMOS transistors 154, 155, and a switch control circuit 151a. The control circuit 150a changes the number of diodes D1b-D5b connected in series to gradually change the voltage level of the voltage Vg and gradually reduce the current value of the drive current Idrv. This makes it possible to easily reduce the drive current Idrv in stages and to prevent the temperature T from reaching the temperature T2.

[0111] Furthermore, the control circuit 150a includes an NMOS transistor 156, and the switch control circuit 151a turns on the NMOS transistor 156 when the temperature T exceeds the temperature T2. The control circuit 150a turns off the NMOS transistor 100 when the temperature T exceeds the temperature T2. In this way, the control circuit 150a suppresses a further increase in the temperature T and suppresses damage to the drive circuit 11a.

[0112] Moreover, the detection circuit 140 includes an NMOS transistor 141 and diodes D1a-D6a, and the switch control circuit 151a turns on the NMOS transistor 155 when the voltage level of the node N0 (i.e., the voltage level of the voltage Vy) becomes the threshold voltage Vthy. Moreover, the switch control circuit 151a turns on the NMOS transistor 156 when the voltage level of the node N1 (i.e., the voltage level of the voltage Vz) becomes the threshold voltage Vthz. In this way, the detection circuit 140 can generate the voltages Vy and Vz by the series of diodes D1a-D6a, and can cause the NMOS transistor 155 to detect that the temperature T has become the temperature T1, and the NMOS transistor 156 to detect that the temperature T has become the temperature T2.

[0113] The drive circuit 11a is a semiconductor module having a power supply terminal D and a ground terminal S. As a result, the drive circuit 11a operates as a low-side IPS (Intelligent Power Switch).

[0114] Moreover, the drive circuit 11b includes an NMOS transistor 100, a detection circuit 120, and a control circuit 150b. When the period during which the current value of the drive current Idrv exceeds a predetermined value exceeds a predetermined period, the drive circuit 11b can reduce the voltage level of the voltage Vg from 3.5V to 2.1V, thereby reducing the drive current Idrv. This makes it possible to provide a drive circuit that can prevent the temperature T from reaching the temperature T2 and reduce the load on the switching element.

[0115] Moreover, the control circuit 150b includes diodes D1b to D5b, NMOS transistors 154 and 155, and a switch control circuit 151b. This makes it possible to easily reduce the drive current Idrv in stages, and to prevent the temperature T from reaching the temperature T2.

[0116] Furthermore, the drive circuit 11b includes a detection circuit 140, the control circuit 150b includes an NMOS transistor 156, and the switch control circuit 151b turns on the NMOS transistor 156 when the temperature T exceeds the temperature T2. This allows the control circuit 150b to suppress a further increase in the temperature T and suppress damage to the drive circuit 11b.

[0117] Moreover, the switch control circuit 151b includes a capacitor 202, a discharge circuit 200, a resistor 201, and an exclusive OR circuit 203. After the “H” level signal S1 is output, the timer 157 turns off the NMOS transistor 155 for a predetermined period P. This makes it possible to prevent the voltage level of the voltage V2 on the line L2 from erroneously becoming 2.1 V, which causes the NMOS transistor 100 to not turn on.

[0118] Moreover, the drive circuit 11b is a semiconductor module having a power supply side terminal D and a ground side terminal S. As a result, the drive circuit 11b operates as a low-side IPS.

[0119] The above-mentioned embodiment is for the purpose of facilitating understanding of the present invention, and is not intended to limit the present invention. Furthermore, the present invention can be modified or improved without departing from the spirit of the present invention, and it goes without saying that the present invention includes equivalents thereof. [Explanation of symbols]

[0120] 10 Motor control device 11a, 11b, 11c, 11d Drive circuit 12 Microcomputer 13 Load 100, 141, 154~156, 160, 214, 301 NMOS transistors 101,112,170 Diodes 110,111,113,121,122,130,201,210,302 Resistance 120,140,300 Detection circuit 150a, 150b Control circuit 151a, 151b Switch control circuit 152,153,212 Inverter circuit 157 Timer 200 discharge circuit 202,211 Capacitor 203 Exclusive OR circuit 213 AND Circuit

Claims

1. a switching element having a control electrode, a power supply electrode, and a ground electrode; a current detection circuit for detecting a drive current flowing through the switching element; a temperature detection circuit for detecting a temperature; a control circuit that sets a voltage level of the control electrode to a first level so that, when a current value of the driving current exceeds a predetermined value, the current value of the driving current decreases while the driving current continues to flow; Equipped with The control circuit includes: when the temperature exceeds a first temperature while the current value of the driving current exceeds the predetermined value, the voltage level of the control electrode is changed from the first level to a second level so that the current value of the driving current further decreases while the driving current continues to flow. Drive circuit.

2. 2. The drive circuit of claim 1, The control circuit includes: n (n>1) diodes connected in series to the control electrode; a first switch that is provided between the n diodes and the ground electrode and that is turned on when the current value of the drive current exceeds the predetermined value; a second switch connected in parallel to m (n>m>0) diodes among the n diodes; a switch control circuit that turns on the second switch when the temperature exceeds the first temperature; A drive circuit including:

3. 3. The drive circuit according to claim 2, The control circuit includes: a third switch provided between the control electrode and the ground electrode; The switch control circuit includes: when the temperature exceeds a second temperature higher than the first temperature, turning on the third switch; Drive circuit.

4. 4. The drive circuit according to claim 3, The temperature detection circuit includes: A current source; k (k>1) diodes connected in series between the current source and the ground electrode; Including, The switch control circuit includes: when a voltage level of a predetermined first node among the plurality of nodes of the k diodes reaches a third level, turning on the second switch; when a voltage level of a second node between the current source and the k diodes reaches a fourth level, turning on the third switch; Drive circuit.

5. A drive circuit according to any one of claims 1 to 4, the drive circuit is a semiconductor module, The semiconductor module includes: a first terminal connected to a power supply via a load; a second terminal connected to ground; A drive circuit including:

6. a switching element having a control electrode, a power supply electrode, and a ground electrode; a current detection circuit for detecting a drive current flowing through the switching element; a control circuit that sets a voltage level of the control electrode to a first level so that, when a current value of the driving current exceeds a predetermined value, the current value of the driving current decreases while the driving current continues to flow; Equipped with The control circuit includes: when the period during which the current value of the driving current exceeds the predetermined value reaches a predetermined period, the voltage level of the control electrode is changed from the first level to a second level so that the current value of the driving current further decreases while continuing to flow. Drive circuit.

7. 7. A drive circuit according to claim 6, The control circuit includes: n (n>1) diodes connected in series to the control electrode; a first switch that is provided between the n diodes and the ground electrode and that is turned on when the current value of the drive current exceeds the predetermined value; A second switch connected in parallel to m (n>m>0) of the n diodes; a switch control circuit that turns on the second switch when a period during which the current value of the drive current exceeds the predetermined value has elapsed; A drive circuit including:

8. 8. A drive circuit according to claim 7, a temperature detection circuit for detecting a temperature; Equipped with The control circuit includes: a third switch provided between the control electrode and the ground electrode; The switch control circuit includes: When the temperature exceeds a second temperature, the third switch is turned on. Drive circuit.

9. 9. A drive circuit according to claim 8, The switch control circuit includes: A capacitor; a discharge circuit that discharges the capacitor for a first period that is a part of the predetermined period after the switching element is turned on; a charging circuit that charges the capacitor after the capacitor has been discharged for the first period of time; an on circuit that turns on the second switch when the capacitor is charged and a second period that is a part of the predetermined period has elapsed; A drive circuit including:

10. A drive circuit according to any one of claims 6 to 9, the drive circuit is a semiconductor module, The semiconductor module includes: a first terminal connected to a power supply via a load; a second terminal connected to ground; A drive circuit including:

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