Drive circuit

Abstract

Provided is a driving circuit which makes it possible to reduce the amount of surge that occurs during an off operation performed when an overcurrent is detected, while reducing switching loss at a normal operation. The present invention is characterized by comprising: a switching element; an on circuit that injects electric charges to the gate of the switching element in response to a driving signal; a first off circuit that extracts electric charges from the gate of the switching element in response to a driving signal; and a second off circuit that is different from the first off circuit and that extracts electric charges from the gate of the switching element in response to an overcurrent detection signal.

Description

[Technical Field]

[0001] The present invention relates to the configuration of a drive circuit and its control, and in particular to a technique that is effective when applied to a drive circuit for an inverter. [Background technology]

[0002] The power semiconductors used in power conversion equipment (inverters) are voltage-driven power semiconductors such as IGBTs (Insulated Gate Bipolar Transistors) and SiC MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), and in recent years, they have become increasingly capable of withstanding higher voltages and carrying larger currents.

[0003] Power conversion devices are also used in electric vehicles, where they convert DC power supplied from a battery to generate AC power for driving a motor. In such applications, there is a demand for reducing switching loss in order to improve battery usage efficiency and suppress losses due to heat generation in the power conversion device.

[0004] Furthermore, when an overcurrent occurs in a phase of the motor, a protective control is required to prevent the motor from burning out or the like.

[0005] Background art in this technical field includes, for example, technology such as that disclosed in Patent Document 1. Patent Document 1 discloses "a power conversion device that enables more effective protection control by configuring a plurality of protection circuits to have priorities assigned to them." [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-5229 Summary of the Invention [Problem to be solved by the invention]

[0007] In order to reduce the switching loss of a power conversion device, it is necessary to lower the gate resistance RG of the switching elements that make up the power conversion device and increase the slew rate, which represents the rate at which the output voltage can change per specified unit time.

[0008] On the other hand, if the gate resistance RG is reduced and the slew rate is increased, the surge amount also increases, and there is a possibility that the surge voltage will exceed the rated voltage of the device and destroy the element.

[0009] Therefore, in the switching elements of conventional power conversion devices, the gate resistance RG is generally determined under the worst-case conditions, including overcurrent of the phase. Since the driving capacity is determined based on these conditions, the element size of the switching element is also limited.

[0010] In the technology of Patent Document 1, when an overcurrent occurs in a phase of the motor, the switching elements of all three phases are turned off using the same control as normal control. Even in the case of a surge that occurs when turning off the switching elements in a large current state due to an overcurrent, it is necessary to control the gates of the switching elements so that the switching elements are not destroyed, and this technology is not optimized for driving the switching elements in a normal operating state.

[0011] Therefore, an object of the present invention is to provide a drive circuit and a control method for the drive circuit that can reduce the amount of surge during an OFF operation when an overcurrent is detected while reducing switching loss during normal operation. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention provides a power supply voltage regulator including a switching element, an ON circuit that injects charge into a gate of the switching element in response to a drive signal, a first OFF circuit that extracts charge from the gate of the switching element in response to the drive signal, and a second OFF circuit that is different from the first OFF circuit and extracts charge from the gate of the switching element in response to an overcurrent detection signal. a first overcurrent detection circuit for detecting an overcurrent in a phase; and a second overcurrent detection circuit for detecting an overcurrent in the switching element;Equipped with The switching element has a control terminal connected to the gate of the switching element and an auxiliary terminal that forms a current mirror circuit through which a current flows that is a constant ratio to the current flowing in the main path, and a first resistor is connected to the auxiliary terminal, and the current acquired by the auxiliary terminal is converted into a voltage and detected by the first overcurrent detection circuit. When an overcurrent of a phase is detected, the ON circuit and the first OFF circuit are disabled. The second overcurrent detection circuit detects an overcurrent of the switching element based on the current-to-voltage converted voltage and a voltage corresponding to the overcurrent of the switching element calculated from the current ratio of the auxiliary terminal. It is characterized by: [Effects of the Invention]

[0014] According to the present invention, it is possible to realize a drive circuit and a control method for the drive circuit that can reduce the amount of surge during an OFF operation when an overcurrent is detected, while reducing switching loss during normal operation.

[0015] This will improve the efficiency and reliability of the power conversion device (inverter).

[0016] Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram showing a schematic configuration of a power conversion device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a circuit configuration of a pre-driver 400 in FIG. [Figure 3] FIG. 10 is a diagram showing the relationship between the slew rate and surge in a switching element. [Figure 4] FIG. 10 is a diagram illustrating losses in a switching element. [Figure 5] FIG. 10 is a diagram showing a schematic configuration of a power conversion device according to a second embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing a circuit configuration of a pre-driver 420 in FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and detailed description of overlapping parts will be omitted. [Example]

[0019] A drive circuit and a control method for the drive circuit according to a first embodiment of the present invention will be described with reference to FIGS.

[0020] FIG. 1 is a diagram showing a schematic configuration of a power conversion device (inverter) 1 of this embodiment, and shows an example in which it is connected between a battery 300 and an electric motor 800.

[0021] As shown in FIG. 1, the power conversion device 1 of this embodiment includes, as its main components, switching elements 500-505, a control circuit 100, pre-drivers 400-405, current sensors 600-602, and overcurrent detection circuits 700-702.

[0022] Voltage-driven power semiconductors such as IGBTs and SiC MOSFETs are used for the switching elements 500 to 505. However, other power semiconductors may be used without being limited to IGBTs and SiC MOSFETs. By charging and discharging electric charge to and from the control terminals of the switching elements 500 to 505, the switching of the switching elements 500 to 505 is performed, and the path through which the current flows is switched, thereby converting power from the battery 300 side to the electric motor 800 side.

[0023] The control circuit 100 outputs control signals to the pre-drivers 400 to 405 based on operation instruction information (for example, target rotation speed, target torque, etc.) for the electric motor 800 from a higher-level control unit (not shown).

[0024] The battery 300 supplies a DC voltage that serves as a power source for the power conversion device 1.

[0025] Capacitor 310 plays a role in stabilizing the voltage by supplying power in the event of a momentary voltage drop when motor 800 is driven. In addition, capacitor 310 reduces noise generated during the switching operations of switching elements 500 to 505, which will be described later, by charging and discharging electric charge from capacitor 310.

[0026] The pre-drivers 400 to 405 are pre-driver circuits that drive the switching elements 500 to 505, respectively.

[0027] The current sensors 600 to 602 respectively detect information on the amount of current flowing through each phase of the power supply system to the electric motor 800, and output the information to the overcurrent detection circuits 700 to 702. The current sensors 600 to 602 may use a method of detecting from a magnetic field using a Hall element, or a method of detecting using a shunt resistor, or any other method may also be used.

[0028] The overcurrent detection circuits 700 to 702 are circuits that detect overcurrent in each phase of the power supply system to the electric motor 800. If the current of each phase detected by the current sensors 600 to 602 exceeds a certain value in both the positive and negative directions, an output indicating an overcurrent is generated.

[0029] For example, if the current sensors 600 to 602 use Hall elements, two comparators are used to output a detection result indicating an overcurrent when the current of each phase of the electric motor 800 is greater than a certain positive value or less than a certain negative value.

[0030] The OR circuit 210 is a circuit that takes the logical sum of the overcurrent detection circuits 700 to 702 and outputs the result to the pre-drivers 400 to 405. As a result, when an overcurrent is detected in any one of the phases of the motor 800, one of the pre-drivers 400 to 405 performs an overcurrent shutoff process.

[0031] The OR circuit 210 may have a latch function, and when an overcurrent state is detected, the state may be maintained until it is released. The held state may be released by an instruction from the control circuit 100, or it may be configured to release the overcurrent state after maintaining it for a certain period of time.

[0032] The electric motor 800 operates as a motor when supplied with electric power. In this embodiment, the electric motor 800 is assumed to be a three-phase motor, and an example is given in which the electric motor 800 is driven using six switching elements 500 to 505 mounted on the power conversion device 1, but the present invention is not limited to this, and the number of phases and the number of switching elements of the electric motor 800 may be increased or decreased, including a circuit for driving the electric motor 800 in accordance with the configuration.

[0033] The detailed operation of the pre-drivers 400 to 405 will be mainly described with reference to Fig. 2. Fig. 2 is a diagram showing the circuit configuration of the pre-driver 400 in Fig. 1, and shows a circuit (pre-driver 400) for one system of the pre-drivers 400 to 405 that drive the switching elements 500 to 505.

[0034] As shown in FIG. 2, the pre-driver 400 is composed of a drive circuit 900 that injects charge into the control terminal of the switching element 500 via a resistor 1000, a drive circuit 901 that extracts charge from the control terminal of the switching element 500 via a resistor 1001, and a drive circuit 902 that extracts charge from the control terminal of the switching element 500 via a resistor 1002.

[0035] During normal operation, the switching element 500 is controlled using the drive circuits 900 and 901. When a signal input from the control circuit 100 commands ON, the drive circuit 900 injects charge into the control terminal of the switching element 500, turning the switching element 500 ON.

[0036] Moreover, when the signal input from the control circuit 100 instructs to turn off the switching element 500, the drive circuit 901 extracts the charge from the control terminal of the switching element 500, and the switching element 500 turns off.

[0037] On the other hand, when an overcurrent is detected in a phase of the electric motor 800 (described later), the drive circuit 902 is used to extract charge from the control terminal of the switching element 500. That is, the drive circuit 902 extracts charge from the control terminal of the switching element 500, turning off the switching element 500. At this time, the drive circuits 900 and 901 are both in the off state, and the extraction of charge is performed using only the drive circuit 902. In other words, when an overcurrent in a phase is detected, the drive circuits 900 and 901 are disabled.

[0038] In this process when an overcurrent is detected, the resistance value of resistor 1002 is greater than the resistance value of resistor 1001, and the speed at which charges are drawn is slower than in the process during normal operation.

[0039] FIG. 3 is a diagram showing the relationship between the slew rate and surge in a switching element.

[0040] 3, the faster the speed at which electric charges are extracted from the control terminal and the higher the slew rate of the switching element, the larger the surge generated in the switching element 500, and the higher the possibility that the surge voltage will exceed the rated voltage and destroy the switching element 500. In particular, when an overcurrent is detected, a larger current flows than during normal operation, and there is a high possibility that a larger surge will occur.

[0041] Therefore, in the pre-driver 400 of this embodiment, during normal operation, the driving circuit 901 and the resistor 1001 are used to control the switching element 500 to be turned off, and when an overcurrent is detected, the driving circuit 902 and the resistor 1002, which has a resistance value greater than that of the resistor 1001, are used to control the switching element 500 to be turned off.

[0042] Fig. 4 is a diagram showing losses in switching elements. As shown in Fig. 4, losses in voltage-driven switching elements used in power conversion devices can be divided into on-loss when the switching element is on and switching loss when the switching element switches from on to off. Because on-loss is determined by the characteristics of the switching element, it is not possible to reduce the loss unless the characteristics of the switching element are improved.

[0043] On the other hand, by increasing the amount of change in the charge injected into or extracted from the control terminal of the switching element and increasing the switching slew rate of the switching element, it is possible to shorten the time required for switching, and therefore to reduce switching loss.

[0044] In the conventional pre-driver configuration, the same control is performed using the same drive circuit and the same resistor, i.e., drive circuit 901 and resistor 1001 in Figure 2, both during normal operation and when an overcurrent is detected in a phase of motor 800.

[0045] Therefore, in order to prevent the switching element 500 from being destroyed by a surge even when a large current is detected when an overcurrent is detected, it is necessary to select a large resistance value for the resistor corresponding to resistor 1001, thereby limiting the speed at which charges are extracted from the control terminal and suppressing the slew rate of the switching element 500.

[0046] Therefore, even during normal operation, the resistance value of the resistor corresponding to resistor 1001 becomes large, and switching loss cannot be reduced.

[0047] In the pre-driver 400 of this embodiment, the drive circuits used to extract charge from the control terminal are separated during normal operation and when an overcurrent is detected in a phase of the motor 800, making it possible to individually adjust the resistor 1001 used during normal operation and the resistor 1002 used when an overcurrent is detected in a phase of the motor 800.

[0048] As a result, during normal operation, by increasing the speed at which charges are extracted from the control terminal and increasing the slew rate of the switching element 500, it is possible to reduce switching losses and suppress losses, leading to improved utilization efficiency of the battery 300.

[0049] Furthermore, when an overcurrent is detected in a phase of the electric motor 800, the surge amount in the large current can be adjusted by the resistor 1002, and breakdown of the switching element 500 can be prevented.

[0050] Although the configuration has been described using the pre-driver 400 here, the pre-drivers 401 to 405 each have a similar configuration.

[0051] As described above, the power conversion device 1 of this embodiment includes switching elements 500 to 505, an ON circuit (drive circuit 900 and resistor 1000) that injects charge into the gates of the switching elements 500 to 505 in response to a drive signal from the control circuit 100, a first OFF circuit (drive circuit 901 and resistor 1001) that extracts charge from the gates of the switching elements 500 to 505 in response to a drive signal from the control circuit 100, and a second OFF circuit (drive circuit 902 and resistor 1002) different from the first OFF circuit (drive circuit 901 and resistor 1001) that extracts charge from the gates of the switching elements 500 to 505 in response to an overcurrent detection signal.

[0052] The speed at which the second off circuit (drive circuit 902 and resistor 1002) extracts charge from the gates of the switching elements 500 to 505 is slower than the speed at which the first off circuit (drive circuit 901 and resistor 1001) extracts charge from the gates of the switching elements 500 to 505.

[0053] According to this embodiment, when an overcurrent in a phase of the electric motor 800 is detected, the speed at which electric charge is extracted from the control terminals of the switching elements 500 to 505 is reduced, thereby suppressing the amount of surge generated in the switching elements 500 to 505, and during normal operation, the slew rate of the switching elements 500 to 505 is increased, thereby reducing switching losses and making it possible to provide an efficient power conversion device that improves the utilization efficiency of the battery 300. [Example]

[0054] Second Embodiment A drive circuit and a control method for the drive circuit according to a second embodiment of the present invention will be described with reference to FIGS.

[0055] FIG. 5 is a diagram showing a schematic configuration of a power conversion device (inverter) 1 of this embodiment, and shows an example in which it is connected between a battery 300 and an electric motor 800.

[0056] The power conversion device 1 of this embodiment differs from embodiment 1 (FIG. 2) in that, as shown in FIG. 6, an overcurrent detection circuit 1200 is arranged in each of the pre-drivers 420 to 425 to detect overcurrent in each of the switching elements 510 to 515.

[0057] The detailed operation of the pre-drivers 420 to 425 will be mainly described with reference to Fig. 6. Fig. 6 is a diagram showing the circuit configuration of the pre-driver 420 in Fig. 5, and shows a circuit (pre-driver 420) for one system of the pre-drivers 420 to 425 that drive the switching elements 510 to 515.

[0058] As shown in FIG. 6, the pre-driver 420 charges and discharges the control terminal of the switching element 510 by the drive circuits 900 and 901 via resistors 1000 and 1001 during normal operation.

[0059] On the other hand, when the overcurrent detection circuits 700 to 702 detect an overcurrent in a phase of the electric motor 800, the drive circuit 902 controls the amount of charge extracted using the resistor 1002 via the logical sum circuit 1300 to extract charge from the control terminal of the switching element 510, thereby shutting off the switching element 510.

[0060] In addition, in the case of an overcurrent in the switching element 510, if the overcurrent detection circuit 1200 detects a voltage above a certain level, it is deemed to be an overcurrent, and the drive circuit 902 performs a shutoff process by drawing out charge from the control terminal of the switching element 510 via the logical OR circuit 1300.

[0061] Both the overcurrent in the phase of the electric motor 800 and the overcurrent in the switching element 510 are conditions that require shutoff processing from a large current state, and are environments in which the surge is likely to become large for the switching element.

[0062] In these two states, the surge amount is kept low by slowly extracting the charge stored in the control terminal of the switching element 510 by the drive circuit 902 through a resistor 1002 having a resistance value greater than that of the resistor 1001, and during normal operation, a drive circuit 901 other than the drive circuit 902 is used to extract the charge through the resistor 1001 having a low resistance value, thereby increasing the slew rate of the switching element 510, reducing switching losses, and improving the utilization efficiency of the battery 300.

[0063] Furthermore, by sharing a circuit that handles overcurrent of the phase of the electric motor 800 and overcurrent of the switching element 510, it is possible to minimize the circuit scale.

[0064] Although the configuration has been described using the pre-driver 420 here, the pre-drivers 421 to 425 each have a similar configuration.

[0065] The switching elements 510 to 515 are voltage-driven switching elements similar to the switching elements 500 to 505 of the first embodiment, and voltage-driven power semiconductors such as IGBTs and SiC MOSFETs are used. However, other power semiconductors may be used without being limited to IGBTs and SiC MOSFETs. As in the first embodiment, switching is performed by charging and discharging electric charge to and from the control terminal, and power conversion is performed by switching the path through which the current flows.

[0066] However, unlike the first embodiment, the switching elements 510 to 515 of this embodiment have auxiliary terminals for obtaining the amount of current flowing in order to detect overcurrent.

[0067] This auxiliary terminal is configured to allow a current that is a fixed ratio to the current flowing through the main path, and is configured, for example, as a current mirror circuit. In the case of a current mirror circuit, the ratio is determined by the area ratio with the control terminal to which it is connected.

[0068] Resistors 1100 to 1105 are connected to the auxiliary terminals, respectively, and current-to-voltage conversion is performed, and the converted voltages are input to the pre-drivers 420 to 425. If the voltage input to the pre-drivers 420 to 425 exceeds the voltage corresponding to the overcurrent of the switching element obtained from this current-to-voltage conversion and the current ratio of the auxiliary terminals, the overcurrent detection circuit 1200 in the pre-drivers 420 to 425 determines that an overcurrent has flowed through the switching elements 510 to 515, and performs shutoff processing.

[0069] As described above, the power conversion device 1 of this embodiment is equipped with a first overcurrent detection circuit (overcurrent detection circuits 700 to 702) that detects overcurrent in a phase, and a second overcurrent detection circuit (overcurrent detection circuit 1200) that detects overcurrent in the switching elements 510 to 515, and an off circuit consisting of a drive circuit 902 and a resistor 1002 is shared as an off circuit that draws charge from the gates of the switching elements 510 to 515 when an overcurrent in a phase is detected by the first overcurrent detection circuit (overcurrent detection circuits 700 to 702), and as an off circuit that draws charge from the gates of the switching elements 510 to 515 when an overcurrent in a switching element is detected by the second overcurrent detection circuit (overcurrent detection circuit 1200).

[0070] In each of the above embodiments, the drive circuit has been described using a power conversion device that drives an electric motor as an example, but the invention is not limited to this and can also be applied to automotive inverter circuits, uninterruptible power supplies, power conversion devices for trains and ships, industrial power conversion devices such as electric motors for factory equipment, power conversion devices for solar power generation systems, power conversion devices for household electric motors, etc.

[0071] Furthermore, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0072] 1...power conversion device (inverter), 100...control circuit, 210...logical OR circuit, 300...battery, 310...capacitor, 400-405, 420-425...pre-drivers, 500-505, 510-515...switching elements, 600-602...current sensors, 700-702, 1200...overcurrent detection circuits, 800...electric motor, 900-902...drive circuits, 1000-1002, 1100-1105...resistors, 1300...logical OR circuit.

Claims

1. A switching element; an ON circuit that injects charge into the gate of the switching element in response to a drive signal; a first off circuit that extracts charge from the gate of the switching element in response to a drive signal; a second off circuit different from the first off circuit, which extracts charge from the gate of the switching element in response to an overcurrent detection signal; a first overcurrent detection circuit for detecting an overcurrent in a phase; a second overcurrent detection circuit that detects an overcurrent in the switching element; Equipped with The switching element has a control terminal connected to a gate of the switching element and an auxiliary terminal forming a current mirror circuit through which a current flows that is a constant ratio to a current flowing through a main path, a first resistor is connected to the auxiliary terminal, and a current acquired by the auxiliary terminal is converted into a voltage; When the first overcurrent detection circuit detects an overcurrent in a phase, Disabling the ON circuit and the first OFF circuit; The second overcurrent detection circuit is a drive circuit that detects an overcurrent of the switching element based on the current-to-voltage converted voltage and a voltage corresponding to the overcurrent of the switching element calculated from the current ratio of the auxiliary terminal.

2. 2. The drive circuit of claim 1, When the second off circuit is used to extract charge from the gate of the switching element, a drive circuit that turns off the ON circuit and the first OFF circuit;

3. 2. The drive circuit of claim 1, A drive circuit in which the speed at which the second off circuit extracts charges from the gate of the switching element is slower than the speed at which the first off circuit extracts charges from the gate of the switching element.

4. 4. The drive circuit according to claim 3, the first off circuit has a second resistor; the second off circuit has a third resistor; the first off circuit controls a rate at which charges are extracted from the gate of the switching element by the second resistor; The second off circuit is a drive circuit in which the speed at which charges are extracted from the gate of the switching element is controlled by the third resistor.

5. 5. The drive circuit according to claim 4, A driving circuit in which the resistance value of the third resistor is greater than the resistance value of the second resistor.

6. A switching element; an ON circuit that injects charge into the gate of the switching element in response to a drive signal; a first off circuit that extracts charge from the gate of the switching element in response to a drive signal; a second off circuit different from the first off circuit, which extracts charge from the gate of the switching element in response to an overcurrent detection signal; a first overcurrent detection circuit for detecting an overcurrent in a phase; a second overcurrent detection circuit that detects an overcurrent in the switching element; Equipped with The switching element has a control terminal connected to a gate of the switching element and an auxiliary terminal forming a current mirror circuit through which a current flows that is a constant ratio to a current flowing through a main path, a first resistor is connected to the auxiliary terminal, and a current acquired by the auxiliary terminal is converted into a voltage; When the first overcurrent detection circuit detects an overcurrent in a phase, a logical sum of the overcurrents in the phase is held; The second overcurrent detection circuit is a drive circuit that detects an overcurrent of the switching element based on the current-to-voltage converted voltage and a voltage corresponding to the overcurrent of the switching element calculated from the current ratio of the auxiliary terminal.

7. 7. A drive circuit according to claim 6, A drive circuit in which the held state of the logical sum is cleared by a control circuit that outputs the drive signal.

8. 7. A drive circuit according to claim 6, A drive circuit in which the held state of the logical sum is cleared after a certain period of time has elapsed.

9. A switching element; an ON circuit that injects charge into the gate of the switching element in response to a drive signal; a first off circuit that extracts charge from the gate of the switching element in response to a drive signal; a second off circuit different from the first off circuit, which extracts charge from the gate of the switching element in response to an overcurrent detection signal; a first overcurrent detection circuit for detecting an overcurrent in a phase; a second overcurrent detection circuit that detects an overcurrent in the switching element, The switching element has a control terminal connected to a gate of the switching element and an auxiliary terminal forming a current mirror circuit through which a current flows that is a constant ratio to a current flowing through a main path, a first resistor is connected to the auxiliary terminal, and a current acquired by the auxiliary terminal is converted into a voltage; When the first overcurrent detection circuit detects an overcurrent in a phase, Disabling the ON circuit and the first OFF circuit; the second overcurrent detection circuit detects an overcurrent of the switching element based on the current-to-voltage converted voltage and a voltage corresponding to the overcurrent of the switching element obtained from the current ratio of the auxiliary terminal; A drive circuit in which the second off circuit is shared by an off circuit that draws charge from the gate of the switching element when an overcurrent of a phase is detected by the first overcurrent detection circuit, and an off circuit that draws charge from the gate of the switching element when an overcurrent of the switching element is detected by the second overcurrent detection circuit.

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