Overvoltage detection device and overvoltage protection circuit

Abstract

This invention provides an overvoltage detection device capable of reliably detecting overvoltages. The overvoltage detection device (10) detects the power supply voltage (V). DC The overvoltage detection device (10) includes: a voltage detection circuit (11) that generates a voltage that reduces the power supply voltage by a predetermined ratio. The voltage generated by the voltage detection circuit (11) is output. The overvoltage detection device (10) also includes: a clamping circuit (12) that clamps the power supply voltage (V) at a predetermined ratio. DC If the voltage is lower than the specified threshold, the output voltage (V) of the overvoltage detection device (10) will be lowered. O The clamp is zero.

Description

Technical Field

[0001] The present invention relates to an overvoltage detection device for detecting overvoltage of a power supply that supplies power to the main circuit, and an overvoltage protection circuit having the overvoltage detection device. Background Technology

[0002] In order to protect the circuit from the effects of overvoltage, when the voltage of the power source supplying power to the main circuit such as the power conversion circuit becomes overvoltage due to noise or surge, an overvoltage protection circuit is installed.

[0003] As prior art related to overvoltage protection circuits, a technique using a voltage divider resistor as an overvoltage detection device and a comparator to determine whether an overvoltage has been detected is known (see, for example, Patent Document 1). The voltage divider of the power supply voltage output from the voltage divider resistor is input to the comparator. The comparator compares the input voltage divider with a reference voltage generated by a reference voltage generation circuit. When the comparator determines that the voltage divider is greater than the reference voltage, it outputs a control signal that stops the main circuit device, such as an inverter.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2004-70666 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In the aforementioned prior art, when noise is superimposed on the output of the voltage divider resistor, the overvoltage protection circuit may malfunction by operating at a voltage lower than the overvoltage setting. That is, there is a possibility that the overvoltage detection device may falsely detect an overvoltage.

[0009] Therefore, the present invention provides an overvoltage detection device capable of reliably detecting overvoltages and an overvoltage protection circuit having such an overvoltage detection device.

[0010] Methods for solving problems

[0011] To address the aforementioned issues, the overvoltage detection device of the present invention detects overvoltage of the power supply voltage and includes: a voltage detection circuit that generates a voltage that reduces the power supply voltage by a predetermined ratio; and an output voltage generated by the voltage detection circuit. The overvoltage detection device of the present invention further includes: a clamping circuit that clamps the output voltage of the overvoltage detection device to zero when the power supply voltage is below a predetermined threshold.

[0012] To address the aforementioned issues, the overvoltage protection circuit of the present invention protects the main circuit from overvoltage of the power supply voltage. It comprises: an overvoltage detection device that detects overvoltage of the power supply voltage; and a comparator that compares the output voltage of the overvoltage detection device with a reference voltage, and outputs a command signal to stop the operation of the main circuit when the output voltage exceeds the reference voltage. This overvoltage detection device is the overvoltage detection device of the present invention described above.

[0013] Invention Effects

[0014] According to the present invention, false detection of overvoltage can be prevented, thus improving the reliability of the overvoltage detection device and the overvoltage protection circuit.

[0015] Other issues, structures, and effects not mentioned above will be clarified through the following description of the implementation methods. Attached Figure Description

[0016] Figure 1 This is a block diagram illustrating the circuit structure of an overvoltage detection device according to one embodiment.

[0017] Figure 2 This is a block diagram showing the circuit structure of the overvoltage detection device in Embodiment 1.

[0018] Figure 3 This is a circuit diagram illustrating a first structural example of the overvoltage detection device of Embodiment 1.

[0019] Figure 4 This is a circuit diagram illustrating a second structural example of the overvoltage detection device of Embodiment 1.

[0020] Figure 5 This is a block diagram showing the circuit structure of the overvoltage detection device in Embodiment 2.

[0021] Figure 6 This is a circuit diagram illustrating the structure of the overvoltage detection device in Embodiment 2. Detailed Implementation

[0022] Figure 1 This is a block diagram illustrating the circuit structure of an overvoltage detection device according to one embodiment of the present invention.

[0023] An overvoltage protection circuit, consisting of an overvoltage detection device 10 and a comparator 20, protects the power conversion circuit 100, which is the main circuit, from DC power supply voltage V. DC The effect of overvoltage.

[0024] As a power conversion circuit 100, it utilizes semiconductor switching elements (in... Figure 1The circuit includes DC / AC converter circuits (inverter circuits) and DC / DC converter circuits, which are parallel circuits of IGBTs and freewheeling diodes. The power conversion circuit 100 controls the switching of semiconductor switching elements through the control device 200 to convert the input DC power into the desired power.

[0025] The overvoltage detection device 10 uses a voltage detection circuit 11 to reduce the input DC power supply voltage V. DC The overvoltage detection device 10 outputs the reduced voltage (V). O Comparator 20 converts the output voltage V of overvoltage detection device 10 into voltage V. O The reference voltage V generated by the reference voltage generation circuit (not shown) ref The comparison is performed. Comparator 20 determines V as V. O More than V ref (V) O >V ref When V DC When the voltage exceeds a preset overvoltage setting value, and the overvoltage detection device 10 determines that an overvoltage has been detected, it sends a command signal to the control device 200 to stop the operation of the power conversion circuit 100. Upon receiving the command signal from the comparator 20, the control device 200 stops the switching of the semiconductor switching element.

[0026] Voltage detection circuit 11 ensures that the input DC power supply voltage V DC The voltage value is generated by reducing the voltage (V) by a specified ratio within the allowable input voltage range of the comparator 20 in the subsequent stage. O ) and output.

[0027] The overvoltage detection device 10 also includes: output voltage (V) O Clamping circuit 12, which will output voltage V O The clamping voltage is specified. When the DC power supply voltage V... DC When the voltage drops below the overvoltage setting value, the output voltage clamping circuit 12 clamps the output potential of the overvoltage detection device 10 to the reference potential (GND). That is, the output voltage clamping circuit 12 clamps the output voltage V... O The clamp is zero volts. Therefore, at V... DC When the voltage is lower than the overvoltage setting value, the overvoltage detection device 10 is prevented from falsely detecting overvoltage.

[0028] In this embodiment, the output voltage clamping circuit 12 is set at the DC power supply voltage V. DC Below the preset threshold V DC_th In the case of (V) DC <V DC_th ), will output voltage V O The clamp is at zero volts. Threshold VDC_th It is a voltage value lower than the overvoltage setting value, and is set to V. O The voltage value becomes the same as or higher than that during overvoltage detection due to noise.

[0029] According to this embodiment, the overvoltage detection device 10 includes an output voltage clamping circuit 12, thereby enabling the overvoltage detection device to clamp the voltage at V. DC When the voltage is lower than the overvoltage setting value, false detection by the overvoltage detection device 10 is prevented. This improves the reliability of the overvoltage detection device 10. Therefore, the reliability of the overvoltage protection circuit is improved.

[0030] Hereinafter, embodiments of the present invention will be described using the accompanying drawings through the following Examples 1 and 2. In each figure (including those described above)... Figure 1 In the accompanying drawings, the parts with the same reference numerals represent the same structural elements or structural elements with similar functions.

[0031] Example 1

[0032] Figure 2 This is a block diagram showing the circuit structure of the overvoltage detection device as Embodiment 1 of the present invention.

[0033] Voltage detection circuit 11 inputs DC power supply voltage V DC Reduce the input V at a specified rate DC The voltage detection circuit 11 outputs the reduced voltage (V). O ).

[0034] In Embodiment 1, the output voltage clamping circuit 12 includes: a short-circuit circuit 13 connected between the output of the voltage detection circuit 11 and the reference potential GND; and a threshold detection circuit 14 that detects a DC power supply voltage V DC Below the above threshold V DC_th When this occurs, the short-circuit circuit 13 is activated.

[0035] According to Example 1, at DC power supply voltage V DC Below the aforementioned threshold V DC_th In this case, short-circuit circuit 13 operates, and the output of voltage detection circuit 11 is short-circuited with the reference potential GND. Therefore, the output voltage V... O It is clamped to zero volts.

[0036] Furthermore, according to this embodiment, by using the short-circuit circuit 13, the output voltage clamping circuit 12 can be made into a relatively simple circuit structure.

[0037] Figure 3 This is a circuit diagram illustrating a first structural example of the overvoltage detection device of Embodiment 1.

[0038] like Figure 3 As shown, the voltage detection circuit 11 is composed of a resistor voltage divider circuit. In the first structural example, the resistor voltage divider circuit has a series circuit of resistors R1 to R4, with one end of the series circuit connected to the high potential VDC of the DC power supply and the reference potential GND, respectively.

[0039] exist Figure 3 In the diagram, resistors R1, R2, R3, and R4 are connected in series from VDC towards GND. The symbols R1, R2, R3, and R4 denote resistors and their resistance values.

[0040] The resistor voltage divider circuit draws the DC power supply voltage V from the two ends of the series circuit of resistors R1~R4. DC Voltage after voltage division (V) O The output is from the series connection point A of resistor R4 connected to GND and resistor R3 connected in series with resistor R4. V0 is the resistance value R of the series circuit of resistors R1~R4. Figure 3 In the circuit, R = R1 + R2 + R3 + R4) and the resistance R between the output of the resistor divider circuit and GND. O ( Figure 3 In the context of R0 = R4, the voltage divider ratio (=R) is set. O / R) from V DC partial pressure (V) O = (R) O / R)×V DC The voltage divider ratio is set to V. O The voltage value becomes the accepting V O The subsequent circuitry in this embodiment ( Figure 1 The voltage value in () represents the range of allowable input voltage for comparator 20.

[0041] The short-circuit circuit 13 is composed of a MOSFET M1, which acts as a semiconductor switching element. MOSFET M1 is connected in parallel with resistor R4. That is, MOSFET M1 is connected between GND and the series connection point A of resistors R3 and R4, which forms the output of the resistor divider circuit. Figure 3 In the structural example, an N-channel MOSFET is used as MOSFET M1. The drain and source of MOSFET M1 are connected to the series connection point A and GND, respectively.

[0042] When V DC Below V DC_th When the threshold detection circuit 14 is turned on, MOSFET M1 is short-circuited between the two ends of resistor R4, i.e., the output of the resistor voltage divider circuit, and GND.

[0043] The threshold detection circuit 14 consists of a resistor voltage divider circuit and a NOT circuit L1 that serves as the driving circuit for MOSFET M1.

[0044] The resistor voltage divider circuit has a series circuit of resistors R5 to R8. One end of the series circuit is connected to the high potential VDC of the DC power supply and the reference potential GND, respectively.

[0045] exist Figure 3 In the diagram, resistors R5, R6, R7, and R8 are connected in series from VDC towards GND. The labels R5, R6, R7, and R8 indicate resistors and their resistance values.

[0046] The resistor voltage divider circuit draws the DC power supply voltage V from the two ends of the series circuit of resistors R5~R8. DC The voltage after voltage division, based on the voltage division ratio set according to the resistance values ​​of resistors R5~R8, is input to NOT circuit L1. When the voltage input from the resistor divider circuit to NOT circuit L1 is set to V... in At that time, the partial pressure ratio is set to V. DC >V DC_th The situation and V DC <V DC_th V in the case in These correspond to the 1 (HIGH) and 0 (LOW) inputs of the NOT circuit, respectively. Therefore, the output of NOT circuit L1 is at V... DC >V DC_th The situation and V DC <V DC_th In the case of 0 (LOW) and 1 (HIGH), the values ​​are respectively 0 (LOW) and 1 (HIGH

[0047] That is, if V DC For V DC_th In the case of (V) DC =V DC_th V in Let V be the input threshold in NOT circuit L1. in_th Then the NOT circuit L1 at V in >V in_th In this case, a control signal is output to turn off MOSFET M1. Additionally, the NOT circuit L1 outputs a control signal to turn off MOSFET M1 under V conditions. in <V in_th The output signal turns on MOSFET M1 under certain conditions.

[0048] The output of the NOT circuit L1 is connected to the gate of MOSFET_M1. Therefore, MOSFET_M1 at V DC >V DC_th The situation and V DC <V DC_thThe states are respectively off and on. Therefore, MOSFET_M1 is in the V state. DC <V DC_th In the case of short circuit, the output of the voltage detection circuit 11, which is composed of resistors R1 to R4, is short-circuited with the reference potential GND.

[0049] According to the first structural example, the voltage detection circuit 11, the short-circuit circuit 13, and the threshold detection circuit 14 can be constructed with relatively simple circuits, thus reducing the circuit size of the overvoltage detection device 10.

[0050] Figure 4 This is a circuit diagram illustrating a second structural example of the overvoltage detection device of Embodiment 1.

[0051] The following is an example of the first structure ( Figure 3 Explain the differences between them.

[0052] like Figure 4 As shown, in the second structural example, the input of the NOT circuit L1 is connected to the high potential VDC of the DC power supply.

[0053] When the voltage input to NOT circuit L1 is set to V in At that time, V in =V DC , with V DC >V DC_th The situation and V DC <V DC_th V in the case in The threshold values ​​of NOT circuit L1 are set in a manner that corresponds to 1 (HIGH) and 0 (LOW) values ​​at the input of the NOT circuit, respectively. Therefore, the output of NOT circuit L1 is at V... DC >V DC_th The situation and V DC <V DC_th In the case of 0 (LOW) and 1 (HIGH), the values ​​are respectively 0 (LOW) and 1 (HIGH

[0054] Therefore, if V DC_th Let V be the input threshold in NOT circuit L1. in_th Then, the NOT circuit L1 is similar to the first and second structural examples, in V in >V in_th In the case of V, a control signal is output to turn off MOSFET M1. in <V in_th The output signal turns on MOSFET M1 under certain conditions.

[0055] Therefore, similar to the first structural example, MOSFET_M1 in V DC <VDC_th In this case, the output of the voltage detection circuit 11 is short-circuited with the reference potential GND.

[0056] According to the second structural example, the total number of circuit components constituting the overvoltage detection device 10 can be reduced.

[0057] Example 2

[0058] Figure 5 This is a block diagram showing the circuit structure of the overvoltage detection device as Embodiment 2 of the present invention.

[0059] The following is a comparison with Example 1 ( Figure 2 Explain the differences between them.

[0060] Voltage detection circuit 11 inputs DC power supply voltage V DC Reduce the input V at a specified rate DC The voltage detection circuit 11 outputs the reduced voltage (V). O As will be described later, the operation of the voltage detection circuit 11 is controlled by the threshold detection circuit 14.

[0061] In embodiment 2, the output voltage clamping circuit 12 includes: a short-circuit circuit 13, which is composed of a passive circuit connected between the output of the voltage detection circuit 11 and the reference potential GND; and a threshold detection circuit 14, which detects a DC power supply voltage V DC Below the aforementioned threshold V DC_th When this occurs, the voltage detection circuit 11 stops operating.

[0062] According to Example 2, at DC power supply voltage V DC Below the aforementioned threshold V DC_th In the case that the voltage detection circuit 11 stops detecting V DC Generate and output ratio V DC When operating at a reduced voltage, the output potential of the voltage detection circuit 11 is clamped to the reference potential GND via the short-circuit circuit 13. Therefore, the output voltage V O It is clamped to zero volts.

[0063] Furthermore, according to Embodiment 2, by using a short-circuit circuit 13 composed of passive circuits, the output voltage clamping circuit 12 can be made into a relatively simple circuit structure.

[0064] Figure 6 This is a circuit diagram illustrating the structure of the overvoltage detection device in Embodiment 2.

[0065] like Figure 6As shown, the voltage detection circuit 11 is composed of a resistor voltage divider circuit. In this example, the resistor voltage divider circuit has a series circuit of resistors R1~R4 and MOSFET M1, with one end of the series circuit connected to the high potential VDC of the DC power supply and the reference potential GND, respectively.

[0066] exist Figure 6 In the diagram, resistors R1, R2, R3, MOSFET M1, and resistor R4 are connected in series from VDC towards GND. The symbols R1, R2, R3, and R4 denote resistors and their resistance values.

[0067] When MOSFET M1 is in the ON state, the resistor voltage divider circuit draws the DC power supply voltage V from the two ends of the series circuit consisting of resistors R1~R3, MOSFET M1, and resistor R4. DC Voltage after voltage division (V) O The output is from the series connection point A of resistor R4 connected to GND and MOSFET M1 connected in series with resistor R4.

[0068] The on-resistance of MOSFET M1 is sufficiently small compared to R1~R4, therefore V0 is equal to the resistance value R of the series connection circuit of resistors R1~R4 (in Figure 6 In the circuit, R = R1 + R2 + R3 + R4) and the resistance R between the output of the resistor divider circuit and GND. O (exist Figure 6 In the middle, R O =R4) set voltage ratio (=R O / R) from V DC partial pressure (V) O = (R) O / R)×V DC The voltage divider ratio is set to V. O The voltage value becomes the accepting V O The subsequent circuitry in this embodiment ( Figure 1 The voltage value in () represents the range of allowable input voltage for comparator 20.

[0069] The short-circuit circuit 13 is composed of resistor R4, which is a passive element.

[0070] The threshold detection circuit 14 is composed of MOSFET M1. Figure 6 In the structural example, an N-channel MOSFET is used as MOSFET M1. The drain and source of MOSFET M1 are connected to one end of the GND side of resistor R3 and one end of the VDC side of resistor R4, respectively.

[0071] The gate of MOSFET M1 is connected to VDC. Therefore, MOSFET M1 receives V...DC As a control signal, the input voltage threshold, i.e., the gate threshold voltage, of the control signal in MOSFET M1 is set to V. DC_th This makes V DC >V DC_th Under these conditions, MOSFET M1 becomes active, and V DC <V DC_th In this case, MOSFET M1 becomes off.

[0072] When MOSFET M1 is off, the electrical connection between R3 and the output in the resistor divider circuit is released, thus stopping the operation of the resistor divider circuit. At this time, the connection between the output of the resistor divider circuit and resistor R4 is maintained, therefore the output of the resistor divider circuit is connected to GND via resistor R4. Consequently, the output potential is clamped to the reference potential GND, therefore the output voltage V... O It is clamped to zero volts. That is, at V DC <V DC_th Under these conditions, the output voltage V O It is clamped to zero volts.

[0073] according to Figure 6 The example structure of the overvoltage detection device 10 shown can be constructed with relatively simple circuits, including the voltage detection circuit 11, the short-circuit circuit 13, and the threshold detection circuit 14, thus reducing the circuit size of the overvoltage detection device 10.

[0074] Furthermore, the present invention is not limited to the embodiments and examples described above, and includes various modifications. For example, the embodiments described above are examples that have been explained in detail for the purpose of easily understanding the present invention, and are not necessarily limited to having all the structures described. In addition, regarding a part of the structure of each embodiment, deletions, additions to other structures, and substitutions with other structures are possible.

[0075] For example, a resistor divider circuit constituting a voltage detection circuit may also include a parallel circuit of multiple resistors. Alternatively, a voltage detection circuit may also include a capacitive divider circuit using capacitors.

[0076] Alternatively, other semiconductor switching elements such as junction FETs can be used to replace MOSFET M1.

[0077] Symbol Explanation

[0078] 10: Overvoltage detection device; 11: Voltage detection circuit; 12: Output voltage clamping circuit; 13: Short circuit circuit; 14: Threshold detection circuit; 20: Comparator; 100: Power conversion circuit; 200: Control device.

Claims

1. An overvoltage detection device for detecting overvoltages in a power supply voltage, characterized in that, have: A voltage detection circuit generates a voltage that is reduced by a predetermined ratio from the power supply voltage. The voltage generated by the voltage detection circuit is output. The overvoltage detection device includes: A clamping circuit that clamps the output voltage of the overvoltage detection device to zero when the power supply voltage is lower than a specified threshold.

2. The overvoltage detection device according to claim 1, characterized in that, The clamping circuit includes: A short-circuit circuit is connected between the output of the overvoltage detection device and the reference potential. A threshold detection circuit activates the short-circuit circuit when it detects that the power supply voltage is lower than the threshold.

3. The overvoltage detection device according to claim 2, characterized in that, The voltage detection circuit has a first resistor voltage divider circuit. The short-circuit circuit has a semiconductor switching element. When the threshold detection circuit detects that the power supply voltage is lower than the threshold, it turns on the semiconductor switching element.

4. The overvoltage detection device according to claim 3, characterized in that, The threshold detection circuit includes: The second resistor voltage divider circuit; and The driving circuit takes the voltage divided by the second resistor voltage divider circuit as input, takes the voltage divided when the power supply voltage is the threshold as the input threshold, and outputs a control signal to turn on the semiconductor switching element when the voltage divided is lower than the input threshold.

5. The overvoltage detection device according to claim 3, characterized in that, The threshold detection circuit includes: The driving circuit takes the power supply voltage as input, uses the threshold as the input threshold, and outputs a control signal to turn on the semiconductor switching element when the power supply voltage is lower than the input threshold.

6. The overvoltage detection device according to claim 1, characterized in that, The clamping circuit includes: The short-circuit circuit consists of passive components connected between the output of the overvoltage detection device and the reference potential. A threshold detection circuit stops operating when it detects that the power supply voltage is lower than the threshold.

7. The overvoltage detection device according to claim 6, characterized in that, The voltage detection circuit includes a resistor divider circuit, which connects multiple resistors and a semiconductor switching element in series. It operates when the semiconductor switching element is in a conducting state. When the threshold detection circuit detects that the power supply voltage is lower than the threshold, it turns on the semiconductor switching element.

8. The overvoltage detection device according to claim 7, characterized in that, The short-circuit circuit is composed of a portion of the plurality of resistors. The threshold detection circuit is composed of the semiconductor switching element. The semiconductor switching element receives the power supply voltage as a control signal and uses the threshold as the input voltage threshold. When the voltage of the control signal is lower than the input voltage threshold, it is disconnected.

9. An overvoltage protection circuit that protects the main circuit from overvoltage of the power supply voltage, characterized in that, have: An overvoltage detection device that detects the overvoltage of the power supply voltage; and A comparator compares the output voltage of the overvoltage detection device with a reference voltage. If the output voltage exceeds the reference voltage, it outputs a command signal to stop the operation of the main circuit. The overvoltage detection device is the overvoltage detection device according to claim 1.

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