JP6686611B2 - Voltage converter - Google Patents

Description

  The present invention relates to a voltage conversion device.

  Patent Document 1 discloses a power supply device having an overvoltage protection function. This power supply device includes a reverse connection protection MOSFET and an overvoltage protection MOSFET. The overvoltage protection MOSFET is configured to shut off the input side of the power conversion circuit when the input voltage Vs becomes equal to or higher than the overvoltage determination threshold value, and to automatically recover when the Vs voltage returns to a normal value.

JP, 2005-51919, A

  By the way, when an overvoltage is generated in this type of voltage converter, it is assumed that the cause thereof is based on an internal factor of the voltage converter or an external factor. For example, when a temporary overvoltage occurs due to an external change (external factor) that tends to occur in a vehicle environment, it is desirable to restore the operation of the voltage conversion device when the external change is resolved and the voltage returns to a normal state. Can be said. On the other hand, if an overvoltage is generated due to an internal failure (internal factor) of the voltage conversion device, the overvoltage may not be resolved even if it is left as it is, and further malfunction may occur. It may be desirable to prohibit operation of the device.

  The present invention has been made based on the above-described circumstances. It is possible to forcibly stop the operation of the voltage conversion unit when an overvoltage occurs to protect it, and to operate the voltage conversion unit when the internal abnormality of the voltage conversion unit occurs. It is an object of the present invention to provide a voltage conversion device capable of increasing the degree of protection by prohibiting the above.

The voltage conversion device of the present invention is
The voltage input from either the first conductive path or the second conductive path is stepped up or down by the on / off operation of the switch element connected between the first conductive path or the second conductive path and the reference conductive path. And a voltage converter that outputs to the other,
A drive unit that outputs a control signal for turning on and off the switch element;
An abnormality detection unit that detects an abnormality in the voltage or current of the first conductive path or the second conductive path;
A protection unit for forcibly stopping the operation of the voltage conversion unit when a predetermined overvoltage state occurs in the voltage conversion unit;
A canceling unit that cancels the forced stop when no abnormality is detected by the abnormality detecting unit during the forced stop of the voltage conversion unit by the protection unit,
A prohibition unit that prohibits the operation of the voltage conversion unit when the operation of the voltage conversion unit by the protection unit is repeated a predetermined number of times or a predetermined time,
Have.

According to the present invention, when the voltage conversion unit is in a predetermined overvoltage state, the protection unit can forcibly stop the operation of the voltage conversion unit, and the protection can be quickly achieved.
When such an overvoltage occurs due to an internal factor (internal failure, etc.) of the voltage conversion unit, the abnormality detection unit does not detect any abnormality during the forced stop of the voltage conversion unit, and the forced stop of the voltage conversion unit is released. The overvoltage will be detected again during the later operation of the voltage conversion unit. That is, when an overvoltage occurs due to an internal factor of the voltage conversion unit, the operation of the voltage conversion unit is stopped and released repeatedly, and when the operation of the voltage conversion unit reaches a predetermined number of times or a predetermined time, the prohibition unit causes the voltage conversion unit to stop. Is prohibited. Therefore, when the internal voltage of the voltage conversion unit is abnormal, the operation of the voltage conversion unit can be prohibited to enhance the degree of protection.
On the other hand, even when an overvoltage occurs due to an external factor of the voltage conversion unit, the protection unit forcibly stops the operation of the voltage conversion unit. However, in this case, since there is a high possibility that the abnormality is continuously detected by the abnormality detection unit during the forced stop of the voltage conversion unit, it is difficult for the voltage conversion unit to repeatedly stop and cancel the operation, and it is difficult to prohibit the operation of the voltage conversion unit. Become.

FIG. 3 is a circuit diagram schematically illustrating the voltage conversion device according to the first embodiment. 5 is a flowchart illustrating a periodic process executed by the voltage conversion device according to the first embodiment.

Preferred forms of the invention are shown below.
In the present invention, the voltage conversion unit may be configured to step up or step down the voltage applied to the first conductive path and output it to the second conductive path. The protection unit may include a nullification circuit that nullifies a control signal issued from the drive unit when the output voltage of the second conductive path is in a predetermined overvoltage state.

  According to this configuration, when the output voltage applied to the second conductive path is in the overvoltage state, the invalidation circuit can invalidate the control signal, and the operation of the voltage conversion unit can be quickly stopped.

  In the present invention, the abnormality detection unit may be configured to detect an abnormality in the voltage of the second conductive path. The canceling unit may be configured to cancel the forced stop when the abnormality detecting unit does not detect the voltage abnormality of the second conductive path during the forced stop of the voltage converting unit by the protecting unit.

  In this configuration, when the abnormality detection unit detects the voltage abnormality of the output-side second conductive path during the forced stop of the voltage conversion unit by the protection unit, it is considered that an overvoltage has occurred regardless of the operation of the voltage conversion unit, It is highly possible that the cause is not an internal factor of the voltage conversion unit but an external factor. On the contrary, if the abnormality detection unit does not detect the voltage abnormality of the second conductive path on the output side during the forced stop of the voltage conversion unit by the protection unit, it is considered that the overvoltage has occurred only during the operation of the voltage conversion unit, and the voltage conversion is performed. The possibility that an internal abnormality of the part has occurred becomes extremely high. That is, if the abnormality determination is performed based on the voltage state of the second conductive path on the output side during the forced stop, it becomes easier to more accurately distinguish the overvoltage based on the external factor from the overvoltage based on the internal factor.

<Example 1>
Hereinafter, Example 1 embodying the present invention will be described.
The voltage conversion device 1 shown in FIG. 1 is configured as, for example, a step-up / down type DCDC converter for a vehicle, and boosts or reduces the DC voltage applied to one of the first conductive path 91 and the second conductive path 92. The voltage is reduced and output to the other conductive path.

  The voltage conversion device 1 includes a first conductive path 91 and a second conductive path 92. The first conductive path 91 is electrically connected to, for example, a high-potential-side terminal of a first power supply unit (not shown), and has a configuration in which a predetermined DC voltage is applied from the first power supply unit. The second conductive path 92 is electrically connected to the high-potential-side terminal of the second power supply section 102, and a predetermined DC voltage is applied from the second power supply section 102.

  The first power supply unit (not shown) and the second power supply unit 102 are composed of known power storage means such as a lithium ion battery, an electric double layer capacitor, a lead storage battery, and other power storage elements. The low-potential-side terminals of the first power supply unit and the second power supply unit 102 are kept at the ground potential (0V).

  Between the first conductive path 91 and the second conductive path 92, the voltage conversion unit 6 that raises or lowers the input voltage applied to the first conductive path 91 to generate the output voltage applied to the second conductive path 92. Is provided. The voltage conversion unit 6 is provided between the first conductive path 91 and the second conductive path 92, and includes switch elements T1, T2, T3, T4 arranged in an H-bridge structure, and a coil 12. The switch elements T1, T2, T3, T4 are all configured as MOSFETs. The first conductive path 91 is provided with an input-side capacitor (not shown), and the second conductive path 92 is provided with an output-side capacitor (not shown).

  In the voltage conversion unit 6, the drain of the switch element T1 is connected to the first conductive path 91, and the source of the switch element T1 is connected to the drain of the switch element T2 and one end of the coil 12. The second conductive path 92 is connected to the drain of the switch element T3, and the drain of the switch element T4 and the other end of the coil 12 are connected to the source of the switch element T3. The third conductive path 93 is connected between the respective sources of the switch elements T2 and T4 and the reference conductive path 99 (ground). Signals from AND circuits 71, 72, 73 and 74 described later are input to the gates of the switch elements T1, T2, T3 and T4, respectively.

  The voltage detection circuit 8 is configured as a known voltage detection circuit that detects the voltage of the second conductive path 92, and inputs a value that reflects the voltage value of the second conductive path 92 to the control unit 2 as a detected value. In the example of FIG. 1, the voltage detection circuit 8 is configured as a voltage divider that divides the voltage value of the second conductive path 92 by the resistors R1 and R2, and the control unit 2 sets a value proportional to the voltage value of the second conductive path 92. Generate as an input value to.

  The current detection circuit 10 is configured as a known current detection circuit that detects a current flowing through the second conductive path 92. The current detection circuit 10 is composed of, for example, a shunt resistor provided in the second conductive path 92 and a differential amplifier that amplifies and outputs the voltage across the shunt resistor. The current value flowing through the second conductive path 92 is ascertained based on the input value from.

  The control unit 2 is configured as, for example, an MCU (Micro Controller Unit), and is fed back by a known method based on the voltage value and the current value input from the voltage detection circuit 8 and the current detection circuit 10 and the target voltage value and the target current value. Control is performed to set the duty ratio of the PWM signal. Then, the PWM signal having the set duty ratio is output to the drive unit 4.

  The drive unit 4 is a circuit that outputs a control signal for turning on / off the switch elements T1, T2, T3, T4. The drive unit 4 has a function of distributing and outputting the PWM signal generated by the control unit 2. The drive unit 4 is configured to output the first signal S1 and the second signal S2. The first signal S1 output from the drive unit 4 is input as it is to the first input terminal of the AND circuit 71, and the inverted signal of the first signal S1 is input to the first input terminal of the AND circuit 72. . The second signal S2 output from the drive unit 4 is inverted and input to the first input terminal of the AND circuit 73, and the second signal S2 is directly input to the first input terminal of the AND circuit 74.

  The applied voltage of the signal line 76 is input to the respective second input terminals of the AND circuits 71, 72, 73, 74. Specifically, an H level signal is input to each second input terminal of the AND circuits 71, 72, 73, 74 when the switch Tr1 described later is in the off state, and in this case, the AND circuits 71, 72, 73, 74. The respective signals of the first input terminals of the AND circuits 71, 72, 73, 74 are output as they are. Then, when the H level signal is input to the second input terminals of the AND circuits 71, 72, 73, and 74 in this way, the voltage conversion unit 6 becomes operable, and at this time, the driving unit 4 operates in the step-down mode or Driven in boost mode.

  In the step-down mode, the PWM signal is output as the first signal S1 and the L level signal is output as the second signal S2. In this case, the PWM signal is complementarily output to the gates of the switch elements T1 and T2 in the form of setting the dead time, and the OFF signal is output to the switch element T2 while the ON signal is being output to the switch element T1. The ON signal is output to the switch element T2 while the OFF signal is being output to the switch element T1. When the first state in which the switch element T1 is turned on and the switch element T2 is turned off and the second state in which the switch element T1 is turned off and the switch element T2 is turned on are switched alternately, the first state The DC voltage applied to the conductive path 91 is stepped down and output to the second conductive path 92. The output voltage of the second conductive path 92 is determined according to the duty ratio of the PWM signal given to the gates of the switch elements T1 and T2. In the step-down mode, the ON signal is continuously input to the gate of the switch element T3, and the switch element T3 is maintained in the ON state. Further, the OFF signal is continuously input to the gate of the switch element T4, and the switch element T4 is maintained in the OFF state.

  In the boost mode, the H level signal is output as the first signal S1 and the PWM signal is output as the second signal S2. In this case, the PWM signals are complementarily output to the gates of the switch elements T3 and T4 with dead times set, and the OFF signal is output to the switch element T4 while the ON signal is being output to the switch element T3. The ON signal is output to the switch element T4 while the OFF signal is being output to the switch element T3. When the first state in which the switch element T3 is turned on and the switch element T4 is turned off and the second state in which the switch element T3 is turned off and the switch element T4 is turned on are switched alternately, the first state The DC voltage applied to the conductive path 91 is boosted and output to the second conductive path 92. The output voltage of the second conductive path 92 is determined according to the duty ratio of the PWM signal given to the gates of the switch elements T3 and T4. In the boost mode, the ON signal is continuously input to the gate of the switch element T1, and the switch element T1 is maintained in the ON state. Further, an off signal is input to the gate of the switch element T2, and the switch element T2 is maintained in the off state.

  Next, the operation of the protection unit 20 will be described. The protection unit 20 is a circuit that functions to forcibly stop the operation of the voltage conversion unit 6 when the voltage conversion unit 6 is in a predetermined overvoltage state, and specifically, the output of the second conductive path 92. It functions as a nullification circuit that nullifies the control signal issued from the drive unit 4 when the voltage is in a predetermined overvoltage state.

  The protection unit 20 includes a resistor R3 having one end connected to the second conductive path 92, and the other end of the resistor R3 is connected to one electrode of the capacitor 62 and the positive-side input terminal of the operational amplifier 60. The other electrode of the capacitor 62 is grounded. A reference voltage determined by the voltage dividing resistors R4 and R5 is input to the negative input terminal of the operational amplifier 60. A feedback resistor R6 is connected between the output terminal of the operational amplifier 60 and the positive input terminal. One electrode of the capacitor 62 is connected to the collector of the switch Tr2 (NPN transistor), and the emitter of the switch Tr2 is grounded. The cathode of the diode D1 is connected to the output terminal of the operational amplifier 60, and the anode of the diode D1 is connected to the signal line 50. One end of the resistor R7 is connected to the power supply line Vcc, and the other end is connected to each anode of the diodes D1 and D2 via the signal line 50. The cathode of the diode D2 is connected to one ends of the resistors R8 and R9, and the other end of the resistor R8 is grounded. The other end of the resistor R9 is connected to the base of the switch Tr1 (NPN transistor). The resistor R10 is connected between the base and the emitter of the switch Tr1, and the emitter of the switch Tr1 is grounded.

  In the voltage conversion device 1 shown in FIG. 1, when the applied voltage (output voltage) of the second conductive path 92 is smaller than the predetermined threshold value, the output from the operational amplifier 60 becomes L level. In this case, the signal input to the control unit 2 via the signal line 50 is an L level signal. In this case, since the switch Tr1 is maintained in the off state, the H level signal is input to the second input terminals of the AND circuits 71, 72, 73, 74 by the signal line 76. In this case, the signals input to the first input terminals of the AND circuits 71, 72, 73, 74 are output from the AND circuits 71, 72, 73, 74 as they are.

  However, when the applied voltage (output voltage) of the second conductive path 92 becomes equal to or higher than the predetermined threshold value, the output from the operational amplifier 60 becomes H level. In this case, the signal input to the control unit 2 via the signal line 50 is an H level signal (overvoltage signal). When the signal line 50 is at H level, the switch Tr1 is turned on, so that the potential of the signal line 76 connected to each second input terminal of the AND circuits 71, 72, 73, 74 becomes L level. That is, in this case, the output signals from the AND circuits 71, 72, 73, 74 are all at the L level, and the signal from the drive unit 4 is invalidated. As described above, in the state where the signal from the drive unit 4 is invalidated, the switch elements T1, T2, T3, T4 are always kept in the off state, and the voltage conversion unit 6 continues to stop.

  The control unit 2 is configured to be able to cancel the invalidation in such a "state in which it is invalidated by the protection unit 20". The control unit 2 maintains the signal line 52 in the L level state, and outputs the H level signal (release signal) to the signal line 52 in the “state in which it is invalidated by the protection unit 20”. Then, cancel the invalidation state. When an H level signal is output to the signal line 52 in the “state in which it is invalidated by the protection unit 20”, the switch Tr2 is turned on, the charge of the capacitor 62 is discharged, and the output from the operational amplifier 60 becomes L. You can switch to a level. Then, the signal line 50 is switched to the L level and the switch Tr1 is switched to the OFF state, so that the signal line 76 inputs the H level signal to the respective second input terminals of the AND circuits 71, 72, 73, and 74. In this way, the invalidation state is released.

Next, the periodic process executed by the control unit 2 will be described.
In the voltage conversion device 1, the control unit 2 executes the periodic process shown in FIG. 2 every predetermined short time. After starting the periodic process of FIG. 2, the control unit 2 first determines whether or not an overvoltage signal is generated on the signal line 50 (S1). When the overvoltage signal is not generated on the signal line 50, the process proceeds to No in S1 and determines whether the charging / discharging operation is being executed (S8). When the charging / discharging operation is being performed by the voltage conversion unit 6 under the drive control of the driving unit 4, the process proceeds to No in S8 and the retry count is cleared (S9). As described above, in the voltage conversion device 1, the number of retries is cleared to 0 when the charging / discharging operation is performed without the overvoltage state in the second conductive path 92. If it is determined in S8 that the charging / discharging operation is not executed, the process proceeds to Yes in S8, and the cycle process ends.

  In the determination process of S1, if it is determined that the overvoltage signal is generated on the signal line 50, the process proceeds to Yes in S1 and it is determined whether the voltage state is recovered (S2). When it is determined that the overvoltage signal is generated in S1, the switch Tr1 is turned on by the operation of the protection unit 20 described above, and the output signals from the AND circuits 71, 72, 73, 74 are all switched to the L level. To be At S2, it is determined whether or not the detection voltage of the voltage detection circuit 8 is within the normal voltage range while the operation of the switch elements T1, T2, T3, T4 is stopped by invalidating the control signal in this way. To judge. In S2, if it is determined that the detection voltage of the voltage detection circuit 8 is within the normal voltage range, the process proceeds to Yes, and if not, the process proceeds to No. If the process proceeds to No in S2, the cycle process ends.

  In this configuration, the control unit 2 that performs the determination process of S2 corresponds to an example of an abnormality detection unit, and functions to detect an abnormality in the voltage of the second conductive path 92.

  When the process proceeds to Yes in S2, it is determined whether the number of retries exceeds the upper limit value (for example, 5 times). If the number of retries does not exceed the upper limit value, the process proceeds to No in S3 and the number of retries is counted up (S6). Then, by outputting the H level signal (latch release signal) to the signal line 52, the switch Tr1 is switched to the OFF state and the disabled state is released.

  In the present configuration, the control unit 2 that performs the process of S7 corresponds to an example of the canceling unit, and cancels the forced stop when the abnormality detecting unit detects no abnormality during the forced stop of the voltage converting unit 6 by the protecting unit 20. To function.

  When it is determined in S3 that the number of retries exceeds the upper limit value, the process proceeds to Yes in S3 and a failure determination is performed (S4). In the process of S4, information indicating that an internal failure has occurred in the voltage conversion device 1 is transmitted to, for example, a host system (not shown) such as a host ECU. After S4, the operation of the voltage conversion unit 6 is prohibited (S5). After the processing of S5 is executed, the operation of the voltage conversion unit 6 is continuously prohibited.

  The control unit 2 that executes the process of S5 corresponds to an example of a prohibition unit, and prohibits the operation of the voltage conversion unit 6 when the stop of the operation of the voltage conversion unit 6 by the protection unit 20 is repeated a predetermined number of times. Works like.

As described above, in the voltage conversion device 1 of the present configuration, when the voltage conversion unit 6 is in a predetermined overvoltage state, the protection unit 20 forcibly stops the operation of the voltage conversion unit 6 to achieve quick protection. be able to.
When such an overvoltage occurs due to an internal factor (internal failure or the like) of the voltage conversion unit 6, no abnormality is detected by the abnormality detection unit during the forced stop of the voltage conversion unit 6 and the forced stop of the voltage conversion unit 6 is released. Thus, the overvoltage is detected again during the operation of the voltage conversion unit 6 after the release. That is, when an overvoltage occurs due to an internal factor of the voltage conversion unit 6, the operation of the voltage conversion unit 6 is repeatedly stopped and released, and when the operation of the voltage conversion unit 6 reaches a predetermined number of times, the prohibition unit causes the voltage conversion unit to be released. The operation of 6 will be prohibited. Therefore, when the voltage conversion unit 6 has an internal abnormality, the operation of the voltage conversion unit 6 can be prohibited and the degree of protection can be increased.
On the other hand, even when an overvoltage occurs due to an external factor of the voltage conversion unit 6, the protection unit 20 forcibly stops the operation of the voltage conversion unit 6. However, in this case, since there is a high possibility that the abnormality detection unit continues to detect an abnormality during the forced stop of the voltage conversion unit 6, it is difficult for the voltage conversion unit 6 to be repeatedly stopped and released, and the operation of the voltage conversion unit 6 is It's hard to be banned.

  Further, the voltage conversion unit 6 is configured to step up or step down the voltage applied to the first conductive path 91 and output it to the second conductive path 92, and the protection unit 20 outputs the output voltage of the second conductive path 92. It includes a nullification circuit for nullifying the control signal issued from the drive unit 4 when in a predetermined overvoltage state. According to this configuration, when the output voltage applied to the second conductive path 92 is in the overvoltage state, the invalidating circuit can invalidate the control signal, and the operation of the voltage conversion unit 6 can be quickly stopped.

  Further, the control unit 2 corresponding to the abnormality detection unit is configured to detect an abnormality in the voltage of the second conductive path 92, and the control unit 2 corresponding to the release unit is forcibly stopped by the protection unit 20 of the voltage conversion unit 6. When the abnormality detecting unit does not detect the voltage abnormality of the second conductive path 92, the forced stop is released. In this configuration, when the abnormality detecting unit detects the voltage abnormality of the second conductive path 92 on the output side during the forced stop of the voltage converting unit 6 by the protection unit 20, the overvoltage occurs regardless of the operation of the voltage converting unit 6. It is highly likely that the cause is not an internal factor of the voltage conversion unit 6 but an external factor. On the contrary, if the abnormality detecting unit does not detect the voltage abnormality of the second conductive path 92 on the output side during the forced stop of the voltage converting unit 6 by the protecting unit 20, it is considered that the overvoltage occurs only during the operation of the voltage converting unit 6. Therefore, the possibility that the internal abnormality of the voltage conversion unit 6 has occurred becomes extremely high. That is, if the abnormality determination is performed based on the voltage state of the second conductive path 92 on the output side during the forced stop, it becomes easier to more accurately distinguish the overvoltage based on the external factor from the overvoltage based on the internal factor.

<Other Examples>
The present invention is not limited to the embodiments described by the above description and drawings, and the following embodiments are also included in the technical scope of the present invention.
(1) In the first embodiment, the voltage converter configured as the step-up / down type DCDC converter is illustrated, but it may be applied to the step-up type DCDC converter or the step-down type DCDC converter. Further, it may be applied to a unidirectional DCDC converter that converts a voltage input from one side and outputs the voltage to the other side, or may be applied to a bidirectional DCDC converter.
(2) In the above-described embodiment, the single-phase DCDC converter is illustrated, but the present invention may be applied to a multiphase DCDC converter.
(3) Although the generator, the load, etc. connected to the first conductive path 91 and the second conductive path 92 are omitted in the above-described embodiment, various devices and electronic parts are provided in the first conductive path 91 and the second conductive path 91. It can be connected to the second conductive path 92.
(4) In the above-described embodiment, an example is shown in which the operation of the voltage conversion unit 6 is prohibited when the operation of the voltage conversion unit 6 by the protection unit 20 is stopped a predetermined number of times. The operation of the voltage conversion unit 6 may be prohibited when the operation stop time of the unit 6 (for example, the accumulated time when the protection unit 20 is forcibly stopped) reaches a predetermined time.

1 ... Voltage conversion device 2 ... Control circuit (abnormality detection unit, cancellation unit, prohibition unit)
4 ... Driving part 6 ... Voltage conversion part 20 ... Protecting part 91 ... 1st conductive path 92 ... 2nd conductive path 99 ... Reference conductive path T1, T2, T3, T4 ... Switching element

Claims (3)

The voltage input from either the first conductive path or the second conductive path is stepped up or down by the on / off operation of the switch element connected between the first conductive path or the second conductive path and the reference conductive path. And a voltage converter that outputs to the other,
A drive unit that outputs a control signal for turning on and off the switch element;
An abnormality detection unit that detects an abnormality in the voltage or current of the first conductive path or the second conductive path;
A protection unit for forcibly stopping the operation of the voltage conversion unit when a predetermined overvoltage state occurs in the voltage conversion unit;
A canceling unit that cancels the forced stop when no abnormality is detected by the abnormality detecting unit during the forced stop of the voltage conversion unit by the protection unit,
During the forced stop of the voltage conversion unit by the protection unit, no abnormality is detected by the abnormality detection unit, the forced stop is released by the release unit, and the overvoltage state is again set during the operation of the voltage conversion unit after the release. a prohibition unit that stops the operation of the voltage converter by the protective portion based on be to prohibit the operation of the voltage converter when repeated a predetermined number of times or for a predetermined time,
Voltage converter having a. The voltage conversion unit is configured to step up or step down the voltage applied to the first conductive path and output the voltage to the second conductive path.
The voltage conversion device according to claim 1, wherein the protection unit includes an invalidation circuit that invalidates the control signal issued from the drive unit when the output voltage of the second conductive path is in the predetermined overvoltage state. . The abnormality detection unit is configured to detect an abnormality in the voltage of the second conductive path,
The voltage conversion device according to claim 2, wherein the canceling unit cancels the forced stop when the abnormality detecting unit detects no voltage abnormality of the second conductive path during the forced stop of the voltage converting unit by the protection unit. .

Images