JP7322653B2 - switch drive - Google Patents

Description

The present invention relates to a switch driving device for driving upper and lower arm switches connected in series with each other.

As a driving device of this type, there is known one that protects a switch from an overcurrent flowing through the switch, as described in Patent Document 1. In this drive device, the switch is protected when the sense current flowing through the sense terminal of the switch exceeds the threshold.

JP 2012-217087 A

A cause of overcurrent flowing through the switch is an upper and lower arm short-circuit, which is a phenomenon in which at least one of the upper and lower arm switches is short-circuited and both of the upper and lower arm switches are turned on. Even when the upper and lower arms are short-circuited, it is required to protect the switch from overcurrent (short-circuit current) flowing through the switch.

Here, when a switch protection operation is performed based on the detection result of a short-circuit current as in the drive device described in Patent Document 1, in a configuration using a switch with a small short-circuit resistance, a short-circuit current flows through the switch. The short-circuit energy generated during the transition from the start to the protective operation may exceed the short-circuit tolerance. Therefore, there is still room for improvement in techniques for protecting switches from short-circuit currents.

SUMMARY OF THE INVENTION It is a primary object of the present invention to provide a switch driving device capable of properly protecting upper and lower arm switches from short-circuit current.

The present invention provides a switch driving device for driving an upper arm switch and a lower arm switch that are connected in series with each other,
Each of the upper arm switch and the lower arm switch has a first main terminal, a second main terminal and a gate, and is turned on when the potential difference of the gate with respect to the second main terminal becomes equal to or higher than a threshold voltage. , is turned off when the potential difference becomes less than the threshold voltage,
An upper arm voltage, which is the voltage between the first main terminal and the second main terminal of the upper arm switch, is detected, and based on the detected upper arm voltage, a short failure of the upper arm switch occurs. an upper arm determination unit that determines
A lower arm voltage, which is a voltage between the first main terminal and the second main terminal of the lower arm switch, is detected, and based on the detected lower arm voltage, a short failure of the lower arm switch occurs. a lower arm determination unit that determines
a lower arm protection unit that maintains the lower arm switch in an off state when it is determined that a short failure has occurred in the upper arm switch;
an upper arm protection unit that maintains the upper arm switch in an off state when it is determined that a short failure has occurred in the lower arm switch.

The upper arm voltage when a short failure occurs in the upper arm switch is different from the upper arm voltage when no failure occurs. In view of this point, in the present invention, based on the detected upper arm voltage, it is determined that a short failure has occurred in the upper arm switch. Then, when it is determined that the upper arm switch is short-circuited, the lower arm switch is kept off. Therefore, when a short-circuit failure occurs in the upper arm switch before the lower arm switch is switched to the ON state next time, it is possible to prevent the upper and lower arm short-circuits from occurring due to the lower arm switch being switched to the ON state thereafter.

Further, in the present invention, similar to the upper arm side, based on the detected lower arm voltage, it is determined that a short failure has occurred in the lower arm switch. Then, when it is determined that a short-circuit failure has occurred in the lower arm switch, the upper arm switch is kept off. Therefore, when a short-circuit failure occurs in the lower arm switch before the upper arm switch is switched to the ON state next time, it is possible to prevent the upper arm switch from being switched to the ON state after that and causing an upper and lower arm short circuit.

According to the present invention described above, even if a short-circuit failure occurs in one of the upper and lower arm switches, the upper and lower arm switches can be properly protected from the short-circuit current.

1 is an overall configuration diagram of a control system according to a first embodiment; FIG. The figure which shows the structure for information transmission in a control system. 4 is a flow chart showing a processing procedure of an upper arm logic circuit; 4 is a flow chart showing a processing procedure of a lower arm logic circuit; 4 is a flow chart showing the procedure of short-circuit failure determination processing for the upper arm logic circuit; 4 is a flowchart showing the procedure of a short-circuit failure determination process for the lower arm logic circuit; 4 is a time chart showing an example of protective operation for preventing short-circuiting of upper and lower arms; FIG. 11 is a flow chart showing the procedure of short-circuit failure determination processing of the upper arm logic circuit according to the second embodiment; FIG. 4 is a flowchart showing the procedure of a short-circuit failure determination process for the lower arm logic circuit; 4 is a time chart showing an example of protective operation for preventing short-circuiting of upper and lower arms;

<First Embodiment>
A first embodiment of a driving device according to the present invention will be described below with reference to the drawings. The drive device is applied to a DCDC converter and a three-phase inverter as power converters. In this embodiment, a control system including a power conversion device is installed in a vehicle such as an electric vehicle or a hybrid vehicle.

As shown in FIG. 1, the control system includes a DCDC converter 20, an inverter 30, a rotating electric machine 40, and a control device 60. The rotary electric machine 40 is, for example, an in-vehicle main machine, and its rotor can transmit power to drive wheels (not shown). The rotary electric machine 40 is, for example, a synchronous machine.

A storage battery 10 as a DC power supply is connected to each phase winding 41 of the rotating electric machine 40 via an inverter 30 and a DCDC converter 20 . The DCDC converter 20 includes a first capacitor 21, a reactor 22, a second capacitor 23, an upper arm transforming switch SCH and a lower arm transforming switch SCL. The DCDC converter 20 has a function of boosting the output voltage of the storage battery 10 with a predetermined voltage as the upper limit. In the present embodiment, each of the transformation switches SCH, SCH is a voltage-controlled semiconductor switching element, specifically an N-channel MOSFET made of SiC. The upper and lower arm transformer switches SCH and SCL have upper and lower arm body diodes DCH and DCL.

A positive electrode bus Lp is connected to the drain of the upper arm transforming switch SCH. The drain of the lower arm transformation switch SCL is connected to the source of the upper arm transformation switch SCH. A negative electrode bus Ln is connected to the source of the lower arm transforming switch SCL. Each bus line Lp, Ln is composed of, for example, a bus bar, which is a conductive member.

A second capacitor 23 is connected in parallel to the series connection of the upper arm transformation switch SCH and the lower arm transformation switch SCL. A first end of a reactor 22 is connected to a connection point between the upper arm transforming switch SCH and the lower arm transforming switch SCL. A first end of the first capacitor 21 and a positive terminal of the storage battery 10 are connected to a second end of the reactor 22 . A negative electrode bus line Ln is connected to the negative electrode terminal of the storage battery 10 and the second end of the first capacitor 21 .

The inverter 30 includes a series connection of upper arm switches SWH and lower arm switches SWL for three phases. In this embodiment, each of the switches SWH and SWL is a voltage-controlled semiconductor switching element, more specifically, an N-channel MOSFET made of SiC. The upper and lower arm switches SWH and SWL have upper and lower arm body diodes DH and DL. A first end of the winding 41 is connected to the connection point of the upper and lower arm switches SWH and SWL in each phase. A second end of each phase winding 41 is connected at a neutral point. The windings 41 of each phase are shifted from each other by an electrical angle of 120°.

In this embodiment, in each of the switches SWH, SWL, SCH, and SCL, the drain corresponds to the first main terminal and the source corresponds to the second main terminal.

The control system comprises phase current sensors 50 and voltage sensors 51 . Phase current sensor 50 detects at least two phase currents among the phase currents flowing in rotating electric machine 40 . The voltage sensor 51 detects the voltage across the terminals of the second capacitor 23 as the power supply voltage VHr. Detection values of the phase current sensor 50 and the voltage sensor 51 are input to the control device 60 .

The control device 60 is mainly composed of a microcomputer. The control device 60 operates the upper arm transformation switch SCH and the lower arm transformation switch SCL to control the output voltage of the DCDC converter 20 (the voltage across the terminals of the second capacitor 23) to its target value. For example, in order to alternately turn on the upper arm transforming switch SCH and the lower arm transforming switch SCL, the control device 60 sends main drive signals corresponding to the upper and lower arm transforming switches SCH and SCL to the drive circuit of the DCDC converter 20. Output. In this embodiment, drive circuits are individually provided corresponding to the upper and lower arm transforming switches SCH and SCL, respectively.

Control device 60 operates switches SWH and SWL of inverter 30 in order to control the control amount of rotating electric machine 40 to its target value. The controlled variable is, for example, torque. The controller 60 provides the inverter 30 with main drive signals corresponding to the upper and lower arm switches SWH and SWL in order to alternately turn on the upper and lower arm switches SWH and SWL with a dead time in each phase. Output to the drive circuit. In the present embodiment, drive circuits are individually provided corresponding to each phase and each arm of the inverter 30 .

The upper and lower arm switches SWH and SWL constituting the inverter 30 among the switches constituting the DCDC converter 20 and the inverter 30 will be mainly described below.

As shown in FIG. 2, the control system includes an upper arm drive coupler 61H, an upper arm logic circuit 62H, an isolation transfer section 63, and an upper arm drive circuit DrH that drives the upper arm switch SWH.

The controller 60 generates an upper arm main drive signal GH for the upper arm switch SWH and a lower arm main drive signal GL for the lower arm switch SWL. Each drive signal takes either an ON command for instructing switching to the ON state of the switch or an OFF command for instructing switching to the OFF state.

The upper arm drive coupler 61H transmits the generated upper arm main drive signal GH to the upper arm logic circuit 62H. The upper arm drive coupler 61H is, for example, a photocoupler or a magnetic coupler.

Processing of the upper arm logic circuit 62H will be described with reference to FIG. This process is repeatedly executed, for example, at a predetermined control cycle.

In step S10, it is determined whether or not the lower arm determination signal SigL input via the insulation transmission unit 63 is an abnormal signal (SigL=H).

If it is determined in step S10 that the signal is not abnormal (SigL=L), the process proceeds to step S11, in which the upper arm main drive signal GH input from the upper arm drive coupler 61H is used as the upper arm drive signal GinH, and the upper arm drive circuit DrH is switched to the upper arm drive circuit DrH. output to That is, the ON command or OFF command represented by the upper arm main drive signal GH is directly output as the upper arm drive signal GinH.

On the other hand, if it is determined to be an abnormal signal in step S10, the process proceeds to step S12, and regardless of the logic of the upper arm main drive signal GH input from the upper arm drive coupler 61H, the upper arm drive signal GinH of the off command is generated. is output to the upper arm drive circuit DrH.

Returning to the description of FIG. 2, the control system includes a lower arm drive coupler 61L, a lower arm logic circuit 62L, and a lower arm drive circuit DrL that drives the lower arm switch SWL.

The lower arm drive coupler 61L transmits the generated lower arm main drive signal GL to the lower arm logic circuit 62L. The lower arm drive coupler 61L is, for example, a photocoupler or a magnetic coupler.

Processing of the lower arm logic circuit 62L will be described with reference to FIG. This process is repeatedly executed, for example, at a predetermined control cycle.

In step S20, it is determined whether or not the upper arm determination signal SigH input via the insulation transfer section 63 is an abnormal signal (SigH=H).

If it is determined in step S20 that it is not an abnormal signal (SigH=L), the process proceeds to step S21, where the lower arm main drive signal GL input from the lower arm drive coupler 61L is used as the lower arm drive signal GinL, and the lower arm drive circuit DrL output to

On the other hand, if it is determined to be an abnormal signal in step S20, the process proceeds to step S22, and regardless of the logic of the lower arm main drive signal GL input from the lower arm drive coupler 61L, the lower arm drive signal GinL of the OFF command is generated. is output to the lower arm drive circuit DrL.

The isolation transmission unit 63 electrically isolates the upper arm logic circuit 62H and the lower arm logic circuit 62L, and transmits information transmitted from one of the upper arm logic circuit 62H and the lower arm logic circuit 62L. transmit to the other. For example, a photocoupler or a magneto-magnetic coupler can be used as the insulation transmission part 63 . This enables information transmission between the logic circuits 62H and 62L having different reference potentials.

Returning to the description of FIG. 2, when the upper arm drive circuit DrH determines that the upper arm drive signal GinH input via the upper arm logic circuit 62H is an ON command, the upper arm drive circuit DrH supplies the charging current to the gate of the upper arm switch SWH. supply. As a result, the gate voltage of the upper arm switch SWH becomes equal to or higher than the threshold voltage Vth, and the upper arm switch SWH is switched to the ON state. On the other hand, when the upper arm drive circuit DrH determines that the upper arm drive signal GinH is an OFF command, the upper arm drive circuit DrH causes a discharge current to flow from the gate of the upper arm switch SWH to the ground portion. As a result, the gate voltage of the upper arm switch SWH becomes less than the threshold voltage Vth, and the upper arm switch SWH is switched off.

The upper arm switch SWH has an upper arm sense terminal StH. A minute current having a correlation with the drain current of the upper arm switch SWH flows through the upper arm sense terminal StH. A current flowing through the upper arm sense terminal StH is detected as an upper arm sense voltage VsH, which is the potential difference of the resistor connected to the sense terminal StH. The detected upper arm sense voltage VsH is input to the upper arm logic circuit 62H.

The upper arm logic circuit 62H detects the voltage between the drain and source of the upper arm switch SWH (hereinafter referred to as upper arm voltage VdsH).

The lower arm drive circuit DrL supplies charging current to the gate of the lower arm switch SWL when determining that the lower arm drive signal GinL input via the lower arm logic circuit 62L is an ON command. As a result, the gate voltage of the lower arm switch SWL becomes equal to or higher than the threshold voltage Vth, and the lower arm switch SWL is switched to the ON state. On the other hand, when the lower arm drive circuit DrL determines that the lower arm drive signal GinL is an OFF command, the discharge current flows from the gate of the lower arm switch SWL to the ground portion. As a result, the gate voltage of the lower arm switch SWL becomes less than the threshold voltage Vth, and the lower arm switch SWL is switched off.

The lower arm switch SWL has a lower arm sense terminal StL. A minute current having a correlation with the drain current of the lower arm switch SWL flows through the lower arm sense terminal StL. A current flowing through the lower arm sense terminal StL is detected as a lower arm sense voltage VsL, which is the potential difference of the resistor connected to the sense terminal StL. The detected lower arm sense voltage VsL is input to the lower arm logic circuit 62L.

The lower arm logic circuit 62L detects the voltage between the drain and source of the lower arm switch SWL (hereinafter referred to as lower arm voltage VdsL).

Next, processing for suppressing the occurrence of upper and lower arm short circuits will be described. In this embodiment, the upper arm logic circuit 62H corresponds to the upper arm determination section, and the upper arm logic circuit 62H and the upper arm drive circuit DrH correspond to the upper arm protection section. The lower arm logic circuit 62L corresponds to the lower arm determination section, and the lower arm logic circuit 62L and the lower arm drive circuit DrL correspond to the lower arm protection section.

FIG. 5 shows the processing performed by the upper arm logic circuit 62H. This process is repeatedly executed, for example, at a predetermined control cycle.

In step S30, it is determined whether or not the upper arm main drive signal GH output from the upper arm drive coupler 61H is an ON command.

If a negative determination is made in step S30, it is determined that it is an OFF command, and the process proceeds to step S31. In step S31, it is determined whether or not the detected upper arm voltage VdsH is lower than the upper arm OFF determination value VαH (>0). In this embodiment, it is determined whether or not the upper arm voltage VdsH continues to be lower than the upper arm OFF determination value VαH for the mask time tm. The processing of step S31 is processing for determining whether or not a short-circuit failure has occurred in the upper arm switch SWH.

That is, when there is no failure in the upper arm switch SWH (that is, it is normal), the upper arm voltage VdsH of the upper arm switch SWH that is turned off is the voltage drop Vf of the upper arm body diode DH through which the return current flows. or more voltage. On the other hand, when a short-circuit failure occurs in the upper arm switch SWH, the upper arm voltage VdsH drops to near 0V, which is lower than the voltage drop amount Vf. The upper arm OFF determination value VαH may be set, for example, to a value smaller than the lower limit value of the range (for example, about 1 to 3 V) of the ON voltage of the upper arm switch SWH in which no failure has occurred. The ON voltage is the drain-source voltage when the upper arm switch SWH is in the ON state, and is generally lower than the voltage drop amount Vf.

If a negative determination is made in step S31, it is determined that the upper arm switch SWH is not short-circuited, and the process proceeds to step S32. In step S32, the logic of the upper arm determination signal SigH is set to L.

On the other hand, if an affirmative determination is made in step S31, it is determined that the detected upper arm voltage VdsH is stuck on the 0V side and that the upper arm switch SWH is short-circuited, and the process proceeds to step S33. At step S33, the logic of the upper arm determination signal SigH is set to H.

If it is determined in step S30 that it is an ON command, the process proceeds to step S34, and the upper arm ON determination value VβH (>0) is set larger as the detected upper arm sense voltage VsH increases. The upper arm sense voltage VsH used in step S34 is a value detected when the drain current flowing through the upper arm switch SWH reaches a steady state after the upper arm switch SWH is turned on. Further, the process of step S34 corresponds to the judgment value setting section.

In step S35, it is determined whether or not the detected upper arm voltage VdsH is lower than the upper arm ON determination value VβH set in step S34. In this embodiment, it is determined whether or not the upper arm voltage VdsH continues to be lower than the upper arm ON determination value VβH for the mask time tm. The processing of step S35 is processing for determining whether or not a short-circuit failure has occurred in the upper arm switch SWH. That is, when a short-circuit failure occurs in the upper arm switch SWH, the upper arm voltage VdsH becomes a value smaller than the lower limit value of the range that the ON voltage of the upper arm switch SWH can take, and sticks to the 0V side.

The upper arm ON determination value VβH is set so as to be able to determine this sticking to the 0V side. The upper arm ON determination value VβH is determined, for example, when a drain current corresponding to the upper arm sense voltage VsH used in step S34 flows through the upper arm switch SWH in which no failure has occurred. It may be set to a value smaller than the lower limit of the possible range.

The upper arm voltage VdsH changes in a wide voltage range from a voltage near 0V to the power supply voltage VHr. In this case, if the voltage detection resolution is set according to the power supply voltage VHr on the upper limit side of this voltage range, the voltage detection accuracy of the upper arm voltage VdsH near 0V may decrease. Here, the higher the drain current, the higher the upper arm voltage VdsH when a short circuit failure occurs. Therefore, by providing the process of step S34, it is possible to improve the determination accuracy of the short-circuit failure.

If a negative determination is made in step S35, the process proceeds to step S32. On the other hand, if an affirmative determination is made in step S35, it is determined that the detected upper arm voltage VdsH is stuck on the 0V side and that the upper arm switch SWH is short-circuited, and the process proceeds to step S33.

FIG. 6 shows the processing performed by the lower arm logic circuit 62L. This process is repeatedly executed, for example, at a predetermined control cycle.

In step S40, it is determined whether or not the lower arm main drive signal GL output from the lower arm drive coupler 61L is an ON command.

If a negative determination is made in step S40, it is determined that it is an OFF command, and the process proceeds to step S41. In step S41, it is determined whether or not the detected lower arm voltage VdsL is lower than the lower arm OFF determination value VαL (>0). In the present embodiment, it is determined whether or not the lower arm voltage VdsL continues to be lower than the lower arm OFF determination value VαL for the mask time tm. The process of step S41 is a process for determining whether or not a short failure has occurred in the lower arm switch SWL. Note that the lower arm OFF determination value VαL may be set to a value smaller than the lower limit value of the range (for example, about 1 to 3 V) that the ON voltage of the lower arm switch SWL with no failure can take.

If a negative determination is made in step S41, it is determined that the lower arm switch SWL is not short-circuited, and the process proceeds to step S42. At step S42, the logic of the lower arm determination signal SigL is set to L.

On the other hand, if an affirmative determination is made in step S41, it is determined that the detected lower arm voltage VdsL is stuck on the 0V side and that the lower arm switch SWL is short-circuited, and the process proceeds to step S43. At step S43, the logic of the lower arm determination signal SigL is set to H.

If it is determined in step S40 that it is an ON command, the process proceeds to step S44, and the larger the detected lower arm sense voltage VsL is, the larger the lower arm ON determination value VβL (>0) is set. Note that the lower arm sense voltage VsL used in step S44 is a value detected when the drain current flowing through the lower arm switch SWL reaches a steady state after the lower arm switch SWL is turned on. Also, the process of step S44 corresponds to the determination value setting unit.

In step S45, it is determined whether or not the detected lower arm voltage VdsL is lower than the lower arm ON determination value VβL set in step S44. In this embodiment, it is determined whether or not the lower arm voltage VdsL continues to be lower than the lower arm ON determination value VβL for the mask time tm. The process of step S45 is a process for determining whether or not a short failure has occurred in the lower arm switch SWL. It should be noted that the lower arm ON determination value VβL is set, for example, when the lower arm switch SWL in which a failure has not occurred flows a drain current corresponding to the lower arm sense voltage VsL used in step S44. It may be set to a value smaller than the lower limit of the range that the voltage can take.

If a negative determination is made in step S45, the process proceeds to step S42. On the other hand, if an affirmative determination is made in step S45, it is determined that the detected lower arm voltage VdsL is stuck on the 0V side and that the lower arm switch SWL is short-circuited, and the process proceeds to step S43.

When the process of step S33 in FIG. 5 or step S43 in FIG. 6 is executed, the logic of the judgment signal whose logic is switched to H among the judgment signals SigH and SigL is continuously maintained at H. All you have to do is

Further, in step S33 of FIG. 5 and step S43 of FIG. 6, a process of notifying the control device 60 that a short-circuit failure has occurred may be performed. In this case, the control device 60 performs, for example, a process of outputting an OFF command to all the switches constituting the DCDC converter 20 and the inverter 30, and a switch of a phase different from the phase in which the short-circuit failure occurred in the inverter 30. A process of outputting an OFF command, or a process of outputting an ON command to all the switches on the side of the upper and lower arms of the inverter 30 where the short failure has occurred may be performed.

Next, an example in which the upper arm switch SWH of the inverter 30 is short-circuited will be described with reference to FIG. 7A shows the transition of the upper arm main drive signal GH output from the control device 60, and FIG. 7B shows the transition of the upper arm main drive signal GH output from the upper arm drive coupler 61H. 7(c) shows transition of the upper arm drive signal GinH output from the upper arm logic circuit 62H. FIG. 7(d) shows transition of the lower arm main drive signal GL output from the control device 60, and FIG. 7(e) shows transition of the lower arm main drive signal GL output from the lower arm drive coupler 61L. 7(f) shows transition of the lower arm drive signal GinL output from the lower arm logic circuit 62L. FIG. 7(g) shows transition of the upper arm determination signal SigH, FIG. 7(h) shows transition of the upper arm voltage VdsH, and FIG. 7(i) shows transition of the lower arm voltage VdsL.

At time t1 during the period in which the upper arm main drive signal GH is turned on, a short failure occurs in the upper arm switch SWH. Therefore, the upper arm voltage VdsH sticks to the 0V side, and the lower arm voltage VdsL sticks to the terminal voltage VH side of the second capacitor 23 . Since the state in which the upper arm voltage VdsH is lower than the upper arm ON determination value VβH continues for the mask time tm, the upper arm determination signal SigH is switched to logic H at time t2. The upper arm determination signal SigH of logic H is transmitted to the lower arm logic circuit 62L via the insulation transfer section 63. FIG.

After that, at time t3, the upper arm main drive signal GH is switched to the OFF command. Thereafter, at time t4, the upper arm main drive signal GH output from the upper arm drive coupler 61H is switched to an OFF command, and thereafter the upper arm drive signal GinH output from the upper arm logic circuit 62H is switched to an OFF command. .

Thereafter, at time t5 when the dead time DT has elapsed from time t3, the lower arm main drive signal GL is switched to the ON command. Then, at time t6, the lower arm main drive signal GL output from the lower arm drive coupler 61L is switched to ON command. However, since the logic H upper arm determination signal SigH is input to the lower arm logic circuit 62L, the lower arm drive signal GinL output from the lower arm logic circuit 62L is maintained at the OFF command.

7(h) and 7(i) show transitions of the arm voltages VdsH and VdsL when there is no failure in the upper arm switch SWH.

Although the upper and lower arm switches SWH and SWL of the inverter 30 have been mainly described, the configuration for protecting the switches from short-circuiting of the upper and lower arms can be similarly applied to the upper and lower arm transformer switches SCH and SCL of the DCDC converter 20. , can be similarly applied to each of the following embodiments.

According to the present embodiment described above, it is possible to prevent the lower arm switch SWL from being turned on next time after the upper arm switch SWH is short-circuited. As a result, after the upper arm switch SWH is short-circuited, it is possible to prevent short-circuiting of the upper and lower arms without causing a short-circuit current to flow through the upper and lower arm switches SWH and SWL.

The upper and lower arm switches SWH and SWL of this embodiment are made of SiC, and their semiconductor chip size is reduced. As a result, the short-circuit withstand capability of the upper and lower arm switches SWH and SWL tends to decrease. Therefore, it is highly advantageous to apply the above-described configuration for preventing the upper and lower arms from being short-circuited to a switch having a small short-circuit resistance.

<Second embodiment>
The second embodiment will be described below with reference to the drawings, focusing on differences from the first embodiment. In this embodiment, the method for determining a short failure of the switch SW is changed.

In the present embodiment, the output signal of the lower arm drive coupler 61L and the lower arm voltage VdsL are input to the upper arm logic circuit 62H via the insulation transfer section 63, and the output of the upper arm drive coupler 61H is sent to the lower arm logic circuit 62L. A signal and the upper arm voltage VdsH are input via the insulation transfer section 63 .

The upper arm logic circuit 62H also performs the processing shown in FIG. 8 in addition to the processing shown in FIG. This process is repeatedly executed, for example, at a predetermined control cycle.

In step S50, it is determined whether both the upper arm main drive signal GH output from the upper arm drive coupler 61H and the lower arm main drive signal GL output from the lower arm drive coupler 61L are OFF commands.

If an affirmative determination is made in step S50, the process proceeds to step S51 to acquire the lower arm voltage VdsL detected by the lower arm logic circuit 62L in the current control cycle. This lower arm voltage VdsL is a value detected when the upper and lower arm switches SWH and SWL are in the off state. Then, it is determined whether or not the obtained lower arm voltage VdsL and the upper arm voltage VdsH detected in the current control cycle are equivalent. The processing of step S51 is processing for determining whether or not an abnormality has occurred in the detection function of the upper arm voltage VdsH in the upper arm logic circuit 62H. By the processing of step S51, it is possible to prevent the short-circuit failure determination accuracy from deteriorating.

Note that if it is determined in step S51 that they are not equivalent, the process of FIG. 8 may be stopped.

If it is determined that they are equal in step S51, the process proceeds to step S52 to determine whether the detected upper arm voltage VdsH exceeds a value obtained by subtracting a predetermined value ΔV from the power supply voltage VHr (hereinafter referred to as an upper arm threshold value). judge. In this embodiment, it is determined whether or not the upper arm voltage VdsH continues to exceed the upper arm threshold "VHr-ΔV" for the mask time tm. The processing of step S52 is processing for determining whether or not a short-circuit failure has occurred in the lower arm switch SWL.

That is, under the condition that the return current does not flow in the upper and lower arm body diodes DH and DL and no failure occurs in the upper and lower arm switches SWH and SWL, the upper arm voltage VdsH and the lower arm voltage VdsL are respectively is basically 1/2 of the power supply voltage VHr. On the other hand, when a short-circuit failure occurs in the lower arm switch SWL, the upper arm voltage VdsH on the opposite arm side sticks to the power supply voltage VHr side. The upper arm threshold value "VHr-ΔV" is set to a value that allows determination of this sticking. Note that the process of step S52 includes a threshold value setting unit. The upper arm threshold "VHr-ΔV" increases as the detected power supply voltage VHr increases.

If a negative determination is made in step S52, the process advances to step S53 to output the upper arm main drive signal GH input from the upper arm drive coupler 61H to the upper arm drive circuit DrH as the upper arm drive signal GinH. That is, the ON command or OFF command represented by the upper arm main drive signal GH is directly output as the upper arm drive signal GinH.

On the other hand, if a negative determination is made in step S52, it is determined that the lower arm switch SWL is short-circuited, and the process proceeds to step S54. In step S54, regardless of the logic of the upper arm main drive signal GH input from the upper arm drive coupler 61H, the upper arm drive signal GinH of the OFF command is output to the upper arm drive circuit DrH.

The lower arm logic circuit 62L also performs the processing shown in FIG. 9 in addition to the processing shown in FIG. This process is repeatedly executed, for example, at a predetermined control cycle.

In step S60, the same processing as in step S50 is performed.

If an affirmative determination is made in step S60, the process proceeds to step S61 to acquire the upper arm voltage VdsH detected by the upper arm logic circuit 62H in the current control cycle. Then, it is determined whether or not the acquired upper arm voltage VdsH and the lower arm voltage VdsL detected in the current control cycle are equivalent. The processing of step S61 is processing for determining whether or not an abnormality has occurred in the detection function of the lower arm voltage VdsL in the lower arm logic circuit 62L.

If it is determined that they are not equivalent in step S61, the process of FIG. 9 may be stopped.

If it is determined that they are equal in step S61, the process proceeds to step S62 to determine whether the detected lower arm voltage VdsL exceeds a value obtained by subtracting a predetermined value ΔV from the power supply voltage VHr (hereinafter referred to as a lower arm threshold value). judge. In this embodiment, it is determined whether or not the lower arm voltage VdsL continues to exceed the lower arm threshold "VHr-ΔV" for the mask time tm. The processing of step S62 is processing for determining whether or not a short-circuit failure has occurred in the upper arm switch SWH. Although the lower arm threshold and the upper arm threshold are set to the same value "VHr-ΔV" in the present embodiment, the lower arm threshold and the upper arm threshold may be set to different values. Incidentally, the processing of step S62 includes a threshold value setting unit.

If a negative determination is made in step S62, the process advances to step S63 to output the lower arm main drive signal GL input from the lower arm drive coupler 61L to the lower arm drive circuit DrL as the lower arm drive signal GinL. That is, the ON command or OFF command represented by the lower arm main drive signal GL is directly output as the lower arm drive signal GinL.

On the other hand, if a negative determination is made in step S62, it is determined that the upper arm switch SWH is short-circuited, and the process proceeds to step S64. In step S64, regardless of the logic of the lower arm main drive signal GL input from the lower arm drive coupler 61L, the lower arm drive signal GinL of the OFF command is output to the lower arm drive circuit DrL.

Next, an example in which the upper arm switch SWH of the inverter 30 is short-circuited will be described with reference to FIG. 10(a) to 10(h) correspond to FIGS. 7(a) to 7(f), 7(h) and 7(i).

At time t1, the upper arm main drive signal GH is switched to an OFF command, and at time t2, the upper arm main drive signal GH output from the upper arm drive coupler 61H is switched to an OFF command, and then the upper arm logic circuit 62H. The upper arm drive signal GinH output from is switched to an OFF command. In the example shown in FIG. 10, it is assumed that a short failure occurs in the upper arm switch SWH at time t2. Therefore, the upper arm voltage VdsH sticks to the 0V side, and the lower arm voltage VdsL sticks to the terminal voltage VH side of the second capacitor 23 .

Since the state in which the lower arm voltage VdsL exceeds the lower arm threshold value “VHr−ΔV” continues for the mask time tm, after time t3, the logic of the lower arm main drive signal GL input to the lower arm logic circuit 62L becomes Regardless, the lower arm drive signal GinL is maintained at the OFF command.

After that, at time t4 when the dead time DT has elapsed from time t1, the lower arm main drive signal GL is switched to an ON command, and at time t5, the lower arm main drive signal GL output from the lower arm drive coupler 61L is also an ON command. can be switched to However, the lower arm drive signal GinL output from the lower arm logic circuit 62L is maintained at the OFF command.

10(g) and 10(h), the dashed-dotted lines show transitions of the arm voltages VdsH and VdsL when the upper arm switch SWH is not short-circuited.

According to the present embodiment described above, it is possible to detect the occurrence of a short-circuit failure during the dead time DT during which no return current flows.

<Other embodiments>
It should be noted that each of the above-described embodiments may be modified as follows.

- In step S30 of FIG. 5 of the first embodiment, it may be determined whether or not an ON command for the upper arm switch SWH is issued based on the detected value of the gate voltage of the upper arm switch SWH. Specifically, when it is determined that the detected value of the gate voltage is equal to or higher than the threshold voltage Vth, it may be determined that the ON command is issued. The same applies to step S40 in FIG.

- The process of step S34 in FIG. 5 may be omitted. In this case, the upper arm ON determination value VβH may be set to a fixed value that is less than the lower limit of the possible range of the ON voltage of the upper arm switch SWH in which no failure has occurred, for example. Similarly, the process of step S44 in FIG. 6 may be omitted.

- The processing shown in FIG. 5 may be performed by the upper arm driving circuit DrH, and the processing shown in FIG. 6 may be performed by the lower arm driving circuit DrL.

- In step S34 of FIG. 5 and step S44 of FIG. 6, instead of the sense voltages VsH and VsL, for example, values detected by the phase current sensor 50 may be used. Even in this case, an effect similar to that of the first embodiment can be obtained.

- The switches constituting the DCDC converter and the inverter are not limited to MOSFETs, and may be IGBTs, for example. In this case, the collector of the IGBT corresponds to the first main terminal, and the emitter of the IGBT corresponds to the second main terminal. Note that the IGBT may be connected to a freewheel diode in anti-parallel.

30... Inverter 60... Control device SWH, SWL... Upper and lower arm switches DrH, DrL... Upper and lower arm drive circuits.

Claims (5)

In a switch driving device for driving upper arm switches (SWH, SCH) and lower arm switches (SWL, SCL) connected in series with each other,
Each of the upper arm switch and the lower arm switch has a first main terminal, a second main terminal and a gate, and is turned on when the potential difference of the gate with respect to the second main terminal becomes equal to or higher than a threshold voltage. , is turned off when the potential difference becomes less than the threshold voltage,
An upper arm voltage (VdsH) that is a voltage between the first main terminal and the second main terminal of the upper arm switch is detected, and based on the detected upper arm voltage, a short failure of the upper arm switch is detected. an upper arm determination unit that determines that the
A lower arm voltage (VdsL) that is a voltage between the first main terminal and the second main terminal of the lower arm switch is detected, and based on the detected lower arm voltage, a short failure of the lower arm switch is detected. a lower arm determination unit that determines that the
a lower arm protection unit that maintains the lower arm switch in an off state when it is determined that a short failure has occurred in the upper arm switch;
an upper arm protection unit that maintains the upper arm switch in an off state when it is determined that a short failure has occurred in the lower arm switch ;
When the upper arm determination unit determines that the detected upper arm voltage is lower than the ON voltage of the upper arm switch in which no failure occurs during a period in which an OFF command is issued to the upper arm switch, determining that a short-circuit failure has occurred in the upper arm switch;
When the lower arm determination unit determines that the detected lower arm voltage is lower than the ON voltage of the lower arm switch in which no failure occurs during a period in which an OFF command is issued to the lower arm switch, A switch driving device for determining that a short-circuit failure of the lower arm switch has occurred . In a switch driving device for driving upper arm switches (SWH, SCH) and lower arm switches (SWL, SCL) connected in series with each other,
Each of the upper arm switch and the lower arm switch has a first main terminal, a second main terminal and a gate, and is turned on when the potential difference of the gate with respect to the second main terminal becomes equal to or higher than a threshold voltage. , is turned off when the potential difference becomes less than the threshold voltage,
An upper arm voltage (VdsH) that is a voltage between the first main terminal and the second main terminal of the upper arm switch is detected, and based on the detected upper arm voltage, a short failure of the upper arm switch is detected. an upper arm determination unit that determines that the
A lower arm voltage (VdsL) that is a voltage between the first main terminal and the second main terminal of the lower arm switch is detected, and based on the detected lower arm voltage, a short failure of the lower arm switch is detected. a lower arm determination unit that determines that the
a lower arm protection unit that maintains the lower arm switch in an off state when it is determined that a short failure has occurred in the upper arm switch;
an upper arm protection unit that maintains the upper arm switch in an off state when it is determined that a short failure has occurred in the lower arm switch;
When the upper arm determination unit determines that the detected upper arm voltage is lower than the ON voltage of the upper arm switch in which no failure occurs during a period in which the ON command is issued to the upper arm switch, determining that a short-circuit failure has occurred in the upper arm switch;
When the lower arm determination unit determines that the detected lower arm voltage is lower than the ON voltage of the lower arm switch in which no failure occurs during a period in which the ON command is issued to the lower arm switch, A switch driving device for determining that a short-circuit failure of the lower arm switch has occurred. The upper arm determination unit detects that the detected upper arm voltage is applied to the series connection body of the upper arm switch and the lower arm switch during a period in which an OFF command is issued to both the upper arm switch and the lower arm switch. If it is determined that the applied power supply voltage (VHr) is stuck, it is determined that a short failure of the lower arm switch has occurred,
If the lower arm determination unit determines that the detected lower arm voltage is stuck to the power supply voltage during a period in which an OFF command is issued to both the upper arm switch and the lower arm switch, the upper arm 3. The switch driving device according to claim 1, wherein it is determined that a short-circuit failure of the arm switch has occurred. In a switch driving device for driving upper arm switches (SWH, SCH) and lower arm switches (SWL, SCL) connected in series with each other,
Each of the upper arm switch and the lower arm switch has a first main terminal, a second main terminal and a gate, and is turned on when the potential difference of the gate with respect to the second main terminal becomes equal to or higher than a threshold voltage. , is turned off when the potential difference becomes less than the threshold voltage,
an upper arm voltage (VdsH), which is the voltage between the first main terminal and the second main terminal of the upper arm switch, during a period in which an OFF command is issued to both the upper arm switch and the lower arm switch; When it is determined that the detected upper arm voltage is stuck to the power supply voltage (VHr) applied to the series connection body of the upper arm switch and the lower arm switch, the short circuit failure of the lower arm switch an upper arm determination unit that determines that is occurring;
Lower arm voltage (VdsL), which is the voltage between the first main terminal and the second main terminal of the lower arm switch, during a period in which an OFF command is issued to both the upper arm switch and the lower arm switch a lower arm determination unit that detects and determines that a short failure of the upper arm switch has occurred when determining that the detected lower arm voltage is stuck to the power supply voltage;
a lower arm protection unit that maintains the lower arm switch in an off state when it is determined that a short failure has occurred in the upper arm switch;
an upper arm protection unit that maintains the upper arm switch in an off state when it is determined that a short failure has occurred in the lower arm switch. When the upper arm determination unit determines that the detected upper arm voltage exceeds an upper arm threshold value (VHr−ΔV) that is greater than 1/2 of the power supply voltage and smaller than the power supply voltage, determining that the detected upper arm voltage is stuck to the power supply voltage;
When the lower arm determination unit determines that the detected lower arm voltage exceeds a lower arm threshold value (VHr−ΔV) that is larger than 1/2 of the power supply voltage and smaller than the power supply voltage, determining that the detected lower arm voltage is stuck to the power supply voltage;
5. The switch driving device according to claim 3, further comprising a threshold value setting unit that sets the upper arm threshold value and the lower arm threshold value higher as the power supply voltage is higher.

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