Protective device

Abstract

To provide a technology for protecting an electronic apparatus from over-voltage.SOLUTION: A protective device is constituted by comprising a voltage detection unit and an output control unit. The voltage detection unit detects whether first voltage supplied to a first node is higher than second voltage. The output control unit comprises: a delay circuit which delays the first voltage to be transmitted to the second node; and a first switch element constituted to output voltage based on the first voltage according to voltage of the second node. The delay circuit is constituted to make the first switch element into an open state in an initial state. When supply of the first voltage is started, the delay circuit makes the first switch element into a short circuit state on the basis of the voltage of the second node when the voltage detection unit detects that the first voltage is equal to or lower than the second voltage, and the delay circuit maintains the first switch element in the initial state by reducing the voltage of the second node when the voltage detection unit detects that the first voltage is higher than the second voltage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a protection device. [Background technology]

[0002] Electronic devices that use various power supply voltages are commercially available as electronic devices that are powered by external power sources such as AC adapters and batteries. Therefore, there is a concern that, for example, an unintended voltage may be applied to the circuit of the electronic device due to misuse by the user. In particular, if a voltage higher than the normal voltage of the electronic device is applied to the circuit of the electronic device, the circuit may be damaged.

[0003] Conventionally, Zener diodes have been used to protect electronic devices from overvoltage, for example. In this case, the Zener diode reduces the voltage supplied to the electronic device, thereby protecting the electronic device from overvoltage. However, in this case, power is constantly supplied to the electronic device even while an overvoltage is being input. Therefore, the operation of the electronic device cannot be stopped while an overvoltage is being input. Furthermore, a current constantly flows through the Zener diode while an overvoltage is being input, which can cause a problem of increased power consumption.

[0004] In addition, in some conventional electronic devices, when an overvoltage is detected using an overvoltage detection circuit, the supply of power to the electronic device is stopped. However, in this case, there is a possibility that the overvoltage may be supplied to the electronic device between the time when the overvoltage starts to be supplied and the time when the power supply is stopped.

[0005] In light of the above, for example, Patent Document 1 proposes a protection device having a comparison circuit, a delay circuit, and a switch unit. The comparison circuit determines whether the input voltage is an overvoltage. The delay circuit delays the supply of voltage via the cutoff switch. The switch unit is opened before a voltage is supplied from an external power source. When an overvoltage is supplied from the external power source, the protection device protects the electronic device by maintaining the cutoff switch in an open state based on the operation of the comparison circuit. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-017636 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a technique for protecting electronic devices from voltage abnormalities such as overvoltage. [Means for solving the problem]

[0008] According to one aspect of the present invention, there is provided a protection device including a voltage detection unit and an output control unit, wherein the voltage detection unit detects whether a voltage Vin supplied to a terminal PVin is higher than a voltage Vex, and the output control unit includes a delay circuit that delays the voltage Vin and transmits it to a node N5, and a switch element Q1 that is configured to be able to output a voltage based on the voltage Vin in accordance with the voltage of the node N5, wherein the delay circuit is configured to open the switch element Q1 in an initial state, and when the supply of the voltage Vin starts, if the voltage detection unit detects that the voltage Vin is equal to or lower than the voltage Vex, the delay circuit shorts the switch element Q1 based on the voltage of the node N5, and if the voltage detection unit detects that the voltage Vin is higher than the voltage Vex, the delay circuit reduces the voltage of the node N5 to maintain the initial state.

[0009] According to another aspect of the present invention, there is provided a protection device according to the above aspect, wherein the delay circuit is configured to gradually increase the voltage of the node N5 when the supply of the voltage Vin starts, and to gradually bring the switch element Q1 into a short-circuit state when the voltage Vin is equal to or lower than the voltage Vex.

[0010] According to yet another aspect of the present invention, there is provided the protection device according to any of the above aspects, wherein the voltage detection unit is configured to detect whether the voltage Vin is higher than the voltage Vex after the supply of the voltage Vin starts and before the switch element Q1 is short-circuited.

[0011] According to yet another aspect of the present invention, there is provided a protection device according to any of the above aspects, wherein the delay circuit includes a resistor R6 and a capacitor C3, one end of the resistor R6 is connected to the terminal PVin, the other end of the resistor R6 is connected to the node N5, and one end of the capacitor C3 is connected to the node N5, and the voltage detection unit is configured to discharge the charge accumulated in the capacitor C3 when it detects that the voltage Vin is higher than the voltage Vex.

[0012] According to yet another aspect of the present invention, there is provided a protection device according to any of the above aspects, wherein the output control unit further includes a switch element Q2 connected to the terminal PVin via a resistor R5, and including a first terminal connected to the gate of the switch element Q1, a second terminal grounded, and a gate connected to the node N5, and the output control unit is configured so that when the voltage of the node N5 is equal to or higher than a voltage Vth1, the switch element Q2 is brought into a short-circuit state, thereby bringing the switch element Q1 into a short-circuit state, and when the voltage of the node N5 is lower than the voltage Vth1, the switch element Q2 is brought into an open state, thereby bringing the switch element Q1 into an open state.

[0013] According to yet another aspect of the present invention, there is provided a protection device according to any of the above aspects, wherein the output control unit further includes a switch element Q3 including a first terminal connected to the node N5, a second terminal grounded, and a gate connected to the voltage detection unit, and the voltage detection unit is configured to output, when it detects that the voltage Vin is higher than the voltage Vex, a signal to the gate of the switch element Q3 to put the switch element Q3 into a short-circuited state, and to output, when it detects that the voltage Vin is equal to or lower than the voltage Vex, a signal to the gate of the switch element Q3 to put the switch element Q3 into an open state.

[0014] According to yet another aspect of the present invention, there is provided a protection device according to any of the above aspects, wherein the voltage detection unit includes a voltage detector having a first terminal to which a voltage based on the voltage Vin is input, and detecting whether the voltage Vin is higher than the voltage Vex.

[0015] According to yet another aspect of the present invention, there is provided a protection device according to any of the above aspects, wherein the voltage detection unit further includes a resistor R1 and a resistor R2, one end of the resistor R1 is connected to the terminal PVin, the other end of the resistor R1 is connected to the first end of the voltage detector, one end of the resistor R2 is connected to the first end of the voltage detector, and the other end of the resistor R2 is grounded.

[0016] According to yet another aspect of the present invention, there is provided a protection device according to any of the above aspects, wherein the voltage detection unit further includes a diode D2, the diode D2 being a Zener diode, the cathode of the diode D2 being connected to the first end of the voltage detector, and the anode of the diode D2 being grounded.

[0017] According to yet another aspect of the present invention, there is provided a protection device according to any of the above aspects, wherein the output control unit further includes a discharge circuit for discharging the charge of the capacitor C3 when the supply of the voltage Vin to the terminal PVin is stopped.

[0018] According to yet another aspect of the present invention, there is provided a protection device according to any of the above aspects, wherein the discharge circuit includes a diode D3, the diode D3 being a Schottky barrier diode, the cathode of the diode D3 being connected to the terminal PVin, and the anode of the diode D3 being connected to the node N5.

[0019] According to yet another aspect of the present invention, there is provided a protection device according to any of the above aspects, wherein the voltage detection unit further comprises a capacitor C1 having one end connected to the first end of the voltage detector and the other end grounded, and a discharge circuit for discharging the charge of the capacitor C1 when the supply of the voltage Vin to the terminal PVin is stopped.

[0020] According to yet another aspect of the present invention, there is provided a protection device according to any of the above aspects, wherein the discharge circuit includes a diode D1, the diode D1 being a Schottky barrier diode, the cathode of the diode D1 being connected to the terminal PVin, and the anode of the diode D1 being connected to the first end of the voltage detector and one end of the capacitor C1. [Brief explanation of the drawings]

[0021] [Figure 1]FIG. 1 is a circuit diagram illustrating a configuration of a protection device according to an embodiment. [Figure 2] 4 is a timing chart for explaining the operation of the protection device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are more specific embodiments of any of the above aspects. The following items can be incorporated into each of the above aspects, either singly or in combination.

[0023] Furthermore, the embodiments shown below are merely examples of configurations for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention is not limited by the materials, shapes, structures, etc. of the components described below. Various modifications can be made to the technical idea of ​​the present invention within the technical scope defined by the claims.

[0024] It should be noted that the drawings are schematic, and the relationship between dimensions in one direction and dimensions in another direction, and the relationship between the dimensions of one member and the dimensions of another member, etc. may differ from the actual situation.

[0025] 1. Embodiment A semiconductor device according to an embodiment will be described.

[0026] The semiconductor device according to the embodiment is, for example, a semiconductor module including a protection device and an electronic device. The protection device is, for example, a device that protects the electronic device from overvoltage when a voltage is supplied to the electronic device from a power source external to the semiconductor device.

[0027] 1.1 Configuration The configuration of the semiconductor device according to the embodiment will be described with reference to Fig. 1. Fig. 1 is a circuit diagram for explaining the configuration of the semiconductor device according to the embodiment.

[0028] The semiconductor device 1 according to the embodiment includes a protection device 10 and an electronic device 20.

[0029] The protection device 10 is configured to be able to supply a voltage Vout based on a voltage Vin supplied from a power supply 2 external to the semiconductor device 1 to an electronic device 20. The power supply 2 is, for example, a constant voltage source such as an AC adapter or a battery. The electronic device 20 is, for example, a load such as various electronic circuits.

[0030] In the following, the configuration of the protection device 10 will be mainly described.

[0031] The protection device 10 includes a voltage detection unit 11 and an output control unit 12 .

[0032] The voltage detection unit 11 is connected to the terminal PVin. The terminal PVin is supplied with the voltage Vin from the power supply 2. The voltage detection unit 11 is configured to be able to detect whether the voltage Vin is higher than the voltage Vex. Here, the voltage Vex is, for example, an overvoltage that is higher than the voltage within the normal operating range of the electronic device 20. The voltage detection unit 11 controls the output control unit 12 based on the result of the above detection. A more specific configuration of the voltage detection unit 11 will be described later.

[0033] The output control unit 12 is connected to the terminal PVin. The output control unit 12 is also connected to the electronic device 20. When the voltage Vin is not supplied from the power supply 2, the output control unit 12 opens the connection between the terminal PVin and the electronic device 20. That is, the terminal PVin is electrically insulated from the electronic device 20. The state of the protection device 10 in which the terminal PVin and the electronic device 20 are open is also referred to as the initial state. The output control unit 12 is configured to output a voltage Vout to the electronic device 20 in accordance with the voltage Vin when the power supply 2 supplies a voltage Vin within the normal operating range of the electronic device 20. The output control unit 12 is configured to maintain the protection device 10 in the initial state based on the detection result of the voltage detection unit 11 when, for example, a voltage Vin higher than the voltage Vex is supplied. That is, when a voltage Vin higher than the voltage Vex is supplied, the output control unit 12 maintains the protection device 10 so as not to supply power to the electronic device 20. A more specific configuration of the output control unit 12 will be described later.

[0034] 1.2 Voltage detection section The configuration of the voltage detection unit 11 will be described again with reference to FIG.

[0035] The voltage detection unit 11 includes resistors R1, R2, R3, and R4, diodes D1 and D2, capacitors C1 and C2, and a reset circuit RS. The diode D1 is, for example, a Schottky barrier diode. The diode D2 is, for example, a Zener diode.

[0036] One end of the resistor R1 is connected to the terminal PVin, and the other end of the resistor R1 is connected to the node N1.

[0037] One end of the resistor R2 is connected to the node N1, and the other end of the resistor R2 is grounded.

[0038] With the above-described configuration of the resistors R1 and R2, the voltage at the node N1 is a divided voltage of the voltage Vin based on the ratio of the resistance values ​​of the resistors R1 and R2.

[0039] One end of the resistor R3 is connected to the node N1, and the other end of the resistor R3 is connected to the node N2.

[0040] One end of the capacitor C1 is connected to the node N2 together with the other end of the resistor R3, and the other end of the capacitor C1 is grounded.

[0041] The reset circuit RS is, for example, a voltage detector. The reset circuit RS has, for example, a first terminal, a second terminal, a third terminal, and a fourth terminal. The first terminal of the reset circuit RS is connected to a node N2. The reset circuit RS can adjust the voltage to detect a voltage Vin outside the lineup of the voltage detector (or a voltage Vin higher than the maximum detection voltage of the voltage detector) by using a voltage division configuration using the resistors R1 and R2 connected to nodes N1 and N2. The second terminal of the voltage detector reset circuit RS is connected to a node N3. The node N3 is connected to the output control unit 12. A signal can be output from the second terminal of the reset circuit RS to the output control unit 12. The third terminal of the reset circuit RS is grounded. The fourth terminal of the reset circuit RS is grounded, for example, via a capacitor C2.

[0042] The reset circuit RS is driven based on the voltage of a node N2, which is based on the voltage Vin. While the reset circuit RS is driven, the reset circuit RS monitors the voltage Vin via the node N2. The reset circuit RS outputs a signal from the second terminal of the reset circuit RS based on the voltage Vin. The reset circuit RS is a circuit that outputs a high-level signal from the second terminal of the reset circuit RS when the voltage input to the first terminal of the reset circuit RS is higher than a specified voltage, and outputs a low-level signal from the second terminal of the reset circuit RS when the voltage input to the first terminal of the reset circuit RS is equal to or lower than the specified voltage. More specifically, while the reset circuit RS is driven, if the voltage Vin is higher than the voltage Vex, the reset circuit RS is configured to output a high-level signal from the second terminal of the reset circuit RS to the output control unit 12. That is, when the voltage Vin is higher than the voltage Vex, the reset circuit RS sets the voltage VN3 of the node N3 to a high level. Furthermore, while the reset circuit RS is driven, if the voltage Vin is equal to or lower than the voltage Vex, the reset circuit RS is configured to output, for example, an "L" level signal from the second terminal of the reset circuit RS to the output control unit 12. In other words, while the reset circuit RS is driven, if the voltage Vin is equal to or lower than the voltage Vex, the reset circuit RS sets the voltage VN3 to the "L" level.

[0043] When the reset circuit RS is not driven (when the reset circuit is in a stopped state), the second terminal of the reset circuit RS is, for example, in a floating state.

[0044] The cathode of diode D1 is connected to terminal PVin. The anode of diode D1 is connected to node N1. In the above configuration, diode D1 functions as a discharge circuit for discharging the charge stored in capacitor C1 and the charge at nodes N1 and N2. Diode D1 functions as a discharge circuit, for example, when the input of voltage to terminal PVin is stopped.

[0045] The cathode of diode D2 is connected to node N1. The anode of diode D2 is grounded. The Zener voltage of diode D2 is lower than the maximum rated voltage of the reset circuit RS. This prevents a voltage higher than the maximum rated voltage from being input to the reset circuit RS.

[0046] The other end of the resistor R2, the anode of the diode D2, the other end of the capacitor C1, and the third end of the reset circuit RS are grounded, for example, via a common node. However, this is not limiting, and the other end of the resistor R2, the anode of the diode D2, the other end of the capacitor C1, and the third end of the reset circuit RS may each be grounded independently.

[0047] One end of the resistor R4 is connected to the terminal PVin, and the other end of the resistor R4 is connected to the node N3.

[0048] 1.3 Output control section The configuration of the output control unit 12 will be described again with reference to FIG.

[0049] The output control unit 12 includes resistors R5, R6, and R7, a capacitor C3, a diode D3, and switch elements Q1, Q2, and Q3. The diode D3 is, for example, a Schottky barrier diode. The switch element Q1 is, for example, a P-type metal-oxide-semiconductor field effect transistor (MOSFET). The switch elements Q2 and Q3 are, for example, N-type MOSFETs.

[0050] A first terminal of the switch element Q1 is connected to the terminal PVin. The first terminal of the switch element Q1 functions as the source of the switch element Q1. A second terminal of the switch element Q1 is connected to the electronic device 20. The second terminal of the switch element Q1 functions as the drain of the switch element Q1. When the voltage Vin is supplied and the switch element Q1 is in the on state (short-circuit state), a voltage Vout based on the voltage Vin is output from the second terminal of the switch element Q1 to the electronic device 20. When the switch element Q1 is in the off state (open state), no power is supplied from the protection device 10 to the electronic device 20.

[0051] One end of resistor R5 is connected to terminal PVin, and the other end of resistor R5 is connected to the gate of switch element Q1. That is, the first end (terminal PVin) of switch element Q1 and the gate of switch element Q1 are connected via resistor R5.

[0052] One end of the resistor R6 is connected to the terminal PVin, and the other end of the resistor R6 is connected to the node N4.

[0053] One end of the resistor R7 is connected to the node N4, and the other end of the resistor R7 is connected to the node N5.

[0054] One end of the capacitor C3 is connected to the node N5, and the other end of the capacitor C3 is grounded.

[0055] The cathode of diode D3 is connected to terminal PVin. The anode of diode D3 is connected to node N4. In the above configuration, diode D3 functions as a discharge circuit for discharging the charge stored in capacitor C3 and the charge at nodes N4 and N5. Diode D3 functions as a discharge circuit, for example, when the input of voltage to terminal PVin is stopped.

[0056] A first terminal of the switch element Q2 is connected to the gate of the switch element Q1 and the other terminal of the resistor R5. The first terminal of the switch element Q2 functions as the drain of the switch element Q2. The gate of the switch element Q2 is connected to the node N5. The second terminal of the switch element Q2 is grounded. The second terminal of the switch element Q2 functions as the source of the switch element Q2.

[0057] In the initial state of the protection device 10, the voltage VN5 is set to, for example, a voltage lower than the threshold voltage of the switching element Q2. That is, the switching element Q2 is set to the OFF state. This also sets the switching element Q1 to the OFF state.

[0058] In the above configuration, the resistor R6 and the capacitor C3 function as a delay circuit. As a result, for example, when the supply of the voltage Vin from the power supply 2 begins, the voltage VN5 (the voltage at the gate of the switch element Q2) gradually increases. In other words, at this time, the voltage VN5 increases with a predetermined delay.

[0059] A first terminal of the switching element Q3 is connected to the node N4. The first terminal of the switching element Q3 functions as the drain of the switching element Q3. The gate of the switching element Q3 is connected to the node N3. That is, a signal can be input to the gate of the switching element Q3 from the voltage detection unit 11. The second terminal of the switching element Q3 is grounded. The second terminal of the switching element Q3 functions as the source of the switching element Q3.

[0060] The switching element Q3 is turned on when the signal from the voltage detection unit 11 is at the “H” level (when the voltage VN3 is at the “H” level). When the switching element Q3 is turned on, nodes N4 and N5 are grounded. This causes the charge stored in capacitor C3 and the residual charge at nodes N4 and N5 to be discharged via the switching element Q3. Therefore, the voltage VN5 is maintained at a voltage lower than the threshold voltage of the switching element Q2. In this way, when the signal from the voltage detection unit 11 is at the “H” level, the switching element Q2 is turned off. Furthermore, when the switching element Q2 is turned off, the switching element Q1 is also turned off. In other words, the protection device 10 is in its initial state. Hereinafter, the threshold voltage of the switching element Q2 will be referred to as voltage Vth1.

[0061] On the other hand, when the signal from the voltage detection unit 11 is at the “L” level (when the voltage VN3 is at the “L” level), the switching element Q3 is in the OFF state. When the switching element Q3 is in the OFF state and the voltage Vin is equal to or greater than the voltage Vth1, the switching element Q2 is in the ON state. That is, when the voltage Vin is equal to or greater than the voltage Vth1 and equal to or less than the voltage Vex, the switching element Q2 is in the ON state. As a result, the switching element Q1 is also in the ON state. As described above, the delay circuit including the resistor R5 and the capacitor C3 causes the voltage VN5 to gradually increase when the supply of the voltage Vin starts. As a result, when the supply of the voltage Vin starts, the switching element Q1 is in the ON state after the first period has elapsed. Furthermore, when the switching element Q1 is changed from the OFF state to the ON state, for example, the switching element Q1 is changed from a weak ON state to a strong ON state as the voltage VN5 increases. That is, the protection device 10 according to the embodiment can be said to have a slow start function.

[0062] The detection time of the voltage detection unit 11 is shorter than the on-time of the switching element Q1. The detection time of the voltage detection unit 11 is, for example, the period from the time when the power supply 2 starts to supply the voltage Vin to the time when the reset circuit RS outputs a signal based on the detection of the voltage Vin. The on-time of the switching element Q1 is, for example, the shortest period from the time when the power supply 2 starts to supply the voltage Vin to the time when the switching element Q1 starts to change from the off state to the on state.

[0063] Furthermore, the second terminal of the switch element Q2, the second terminal of the switch element Q3, and the other terminal of the capacitor C3 are grounded, for example, via a common node. However, this is not limiting, and the second terminal of the switch element Q2, the other terminal of the capacitor C3, and the second terminal of the switch element Q3 may each be independently grounded.

[0064] 1.4 Operation Next, the operation of the protection device 10 according to the embodiment will be described with reference to FIG. 2. FIG. 2 is a timing chart for explaining the operation of the protection device according to the embodiment. In the operation example shown with reference to FIG. 2, first, a normal voltage V1 starts to be supplied to the terminal PVin, and then a voltage Vout based on the voltage V1 is supplied from the terminal PVout. Also, an example is shown in which, after the supply of the voltage V1 ends, the protection device 10 protects the electronic device 20 from the overvoltage when an overvoltage higher than the voltage Vex is supplied to the terminal PVin. Note that in FIG. 2 and the following description, the ground voltage is referred to as the voltage VSS.

[0065] At time T1, the power supply 2 starts supplying a voltage V1 to the terminal PVin as the voltage Vin. The voltage V1 is, for example, within the normal operating range of the electronic device 20 and is equal to or greater than the voltage Vth1. Furthermore, a delay circuit including a resistor R5 and a capacitor C3 causes a voltage VN5 to gradually increase. Note that the voltage VN3 increases for a short period of time due to the voltage Vin. The voltage VN3 is maintained at the "L" level by, for example, a reset circuit RS.

[0066] At time T2, voltage VN5 reaches voltage Vth1. As a result, switching element Q2 changes from an off state to an on state, and switching element Q1 changes from an off state to an on state. At time T2, switching element Q1 is put into a weak on state ("Q1; weak on state" in FIG. 2). Voltage Vout begins to be supplied to electronic device 20. Before time T2, the reset circuit RS detects that voltage Vin is equal to or lower than voltage Vex before the on time of switching element Q1 has elapsed since time T1. The reset circuit RS outputs an "L" level signal. As a result, the reset circuit RS maintains voltage VN3 at "L" level.

[0067] At time T3, voltage VN5 becomes, for example, substantially equal to voltage V1. This causes switch element Q1 to be in a strong on state ("Q1; strong on state" in FIG. 2). Furthermore, voltage Vout substantially equal to voltage V1 is supplied to electronic device 20.

[0068] At time T4, the supply of voltage Vin from the power supply 2 is stopped. That is, for example, the power supply 2 is disconnected from the semiconductor device 1. At time T4, for example, the charge stored in capacitor C3 and the charge at nodes N4 and N5 are discharged via diode D3, causing voltage VN5 to drop quickly. As a result, switch elements Q1 and Q2 change from the on state to the off state. Furthermore, the charge stored in capacitor C1 and the charge at nodes N1 and N2 are discharged via diode D1. As a result, the voltage at node N2 drops quickly. Furthermore, the reset circuit RS quickly goes into a stopped state.

[0069] At time T5, the power supply 2 starts to supply an overvoltage higher than the voltage Vex to the terminal PVin as the voltage Vin. Also, similar to the operation at time T1, the voltage VN5 starts to gradually increase. Note that, similar to the operation at time T1, the voltage VN3 is maintained at the "L" level.

[0070] At time T6, before the on-time of switch element Q1 has elapsed since time T5, the reset circuit RS of the voltage detection unit 11 outputs an “H” level signal. This causes switch element Q3 to change from the off state to the on state (“Q3; on state” in FIG. 2). Furthermore, the charge stored in capacitor C3 and the charge at nodes N4 and N5 are discharged via switch element Q3 (“discharge via Q3” in FIG. 2). As a result, switch elements Q1 and Q2 are maintained in the off state. That is, the protection device 10 is maintained in the initial state. In this way, the protection device 10 prevents power from being supplied to the electronic device 20 when an overvoltage is supplied to the terminal PVin.

[0071] At time T7, the supply of voltage Vin to terminal PVin from power supply 2 is stopped, causing voltages Vin and VN3 to be voltage VSS.

[0072] This completes the operation of the protection device 10.

[0073] 1.5 Effects The protection device 10 according to the embodiment can provide a technique for protecting an electronic device from voltage abnormalities such as overvoltage.

[0074] A protection device 10 according to an embodiment includes a voltage detection unit 11 and an output control unit 12. The voltage detection unit 11 detects whether the voltage Vin supplied to a terminal PVin is higher than the voltage Vex. The output control unit 12 includes a switch element Q1 and a delay circuit configured with a resistor R6 and a capacitor C3. The delay circuit is configured to delay the voltage Vin and transmit it to a node N5. The switch element Q1 can output a voltage based on the voltage Vin in response to the delayed voltage VN5 at the node N5. The delay circuit also turns off the switch element Q1 in an initial state in which the voltage Vin is not supplied from the power supply 2. When the supply of the voltage Vin from the power supply 2 begins, if the voltage detection unit 11 detects that the voltage Vin is equal to or lower than the voltage Vex, the delay circuit turns on the switch element Q1 based on the voltage VN5. If the voltage detection unit 11 detects that the voltage Vin is higher than the voltage Vex, the delay circuit reduces the voltage VN5 to maintain the delay circuit in its initial state. That is, the delay circuit resets the voltage VN5 at the node N5 to maintain the switch element Q1 in the off state. With the above-described configuration, the protection device 10 according to the embodiment can protect the electronic device 20 from voltage abnormalities such as overvoltage.

[0075] Furthermore, according to the embodiment, as described above, the delay circuit of the output control unit 12 includes a resistor R6 and a capacitor C3. With this configuration, the delay circuit gradually increases the voltage VN5. As a result, when the voltage Vin is equal to or lower than the voltage Vex, the switch element Q1 is gradually changed from a weak on state to a strong on state as the voltage VN5 increases. This makes it possible to suppress an increase in the load on the electronic device 20 when protecting the electronic device 20 from an overvoltage.

[0076] To add to that, for example, if the detection circuit detects that the input voltage is normal, and the switch element that supplies voltage to the electronic device is short-circuited in a short time, a large load will be placed on the electronic device. That is, the switch will be changed from an off state to a strong on state in a short time, and a sudden voltage will be applied to the electronic device.

[0077] According to the embodiment, the above-described configuration prevents the switch element Q1 from suddenly becoming strongly on when power is supplied to the electronic device 20. This prevents surges and ripples from occurring when a switch element that is off suddenly becomes strongly on. Therefore, an increase in the load on the electronic device 20 is suppressed.

[0078] Furthermore, in the protection device 10 according to the embodiment, the voltage detection unit 11 detects whether the voltage Vin is higher than the voltage Vex after the supply of the voltage Vin starts and before the switch element Q1 is short-circuited. This prevents an overvoltage from being supplied to the electronic device 20 until the detection of the voltage Vin is completed. This configuration also makes it possible to protect the electronic device 20 from an overvoltage.

[0079] Furthermore, in the delay circuit of the protection device 10 according to the embodiment, as described above, the voltage Vin at the terminal PVin is delayed and transmitted to the node N5. More specifically, in the delay circuit of the protection device 10 according to the embodiment, one end of the resistor R6 is connected to the terminal PVin. The other end of the resistor R6 is connected to the node N5. Furthermore, one end of the capacitor C3 is connected to the node N5. With the above-described configuration, the protection device 10 according to the embodiment can, for example, execute the operation of the voltage detection unit 11 and the operation of the output control unit 12 in parallel when the supply of the voltage Vin from the power supply 2 starts. Therefore, the protection device 10 according to the embodiment can quickly supply power to the electronic device 20.

[0080] To add to this, for example, if a detection circuit that detects whether the input voltage from the power supply is an overvoltage and a delay circuit that delays the input voltage operate in series, the input voltage within the normal voltage range will be supplied to the electronic device after an addition period, which is the sum of the detection period of the detection circuit and the delay period of the delay circuit, has elapsed. This may result in a delay in the supply of power by the amount of the addition period.

[0081] According to the protection device 10 of this embodiment, as described above, the node N5 is connected to the terminal PVin via the resistor R6 of the delay circuit. With this configuration, when the supply of the voltage Vin starts, the protection device 10 can detect, using the voltage detection unit 11, whether the voltage Vin is higher than the voltage Vex, while gradually increasing the voltage VN5 using the delay circuit of the output control unit 12. That is, the operation of the voltage detection unit 11 and the operation of the output control unit 12 can be performed in parallel. Therefore, the protection device 10 can start supplying the voltage Vout based on the voltage Vin without waiting for the above-described addition period to elapse. Therefore, according to the protection device 10 of this embodiment, power can be quickly supplied to the electronic device 20.

[0082] Furthermore, according to the protection device 10 of the embodiment, as described above, the voltage detection unit 11 can detect that the voltage Vin is an overvoltage before the switch element Q1 starts to output the voltage Vout. This eliminates the need to wait for the voltage detection unit 11 to detect the voltage Vin before the output control unit 12 outputs the voltage Vout. With the above-described configuration, the protection device 10 of the embodiment can quickly supply power to the electronic device 20.

[0083] The protection device 10 according to the embodiment also includes a diode D3. The cathode of the diode D3 is connected to the terminal PVin. The anode of the diode D3 is connected to the node N4. With this configuration, for example, when the supply of the voltage Vin from the power supply 2 is stopped at time T4 and time T7, the charge accumulated in the capacitor C3 and the residual charge at the nodes N4 and N5 can be quickly discharged via the diode D3. This allows the switch elements Q1 and Q2 to be quickly turned off. Therefore, for example, if an overvoltage is supplied to the input terminal immediately after the supply of the input voltage is stopped, the overvoltage is prevented from being supplied to the electronic device before the cutoff switch is turned off.

[0084] The protection device 10 according to the embodiment also includes a diode D1. The cathode of the diode D1 is connected to the terminal PVin. The anode of the diode D1 is connected to the node N1. With this configuration, the reset circuit RS can be quickly brought to a stopped state when the supply of the voltage Vin from the power supply 2 is stopped. With this configuration, even if an overvoltage is applied immediately after the supply of the voltage Vin is stopped, the application of the overvoltage to the electronic device 20 is suppressed.

[0085] Specifically, when the supply of voltage Vin from the power supply 2 is stopped, the charge stored in capacitor C1 and the charges at nodes N1 and N2 are quickly discharged via diode D1. This quickly switches the reset circuit RS to a stopped state. Furthermore, the second terminal of the reset circuit RS is set to a floating state. Therefore, even if an overvoltage is applied to terminal PVin immediately after the supply of voltage Vin is stopped, node N3 is pulled up via resistor R4 (voltage VN3 is set to the “H” level), turning on switch element Q3. In this way, the charge stored in capacitor C3 and the residual charge at nodes N4 and N5 can be discharged via switch element Q3. Therefore, for example, even if an overvoltage is applied to terminal PVin immediately after the supply of voltage V1 is stopped, switch elements Q1 and Q2 can be maintained in an off state. [Explanation of symbols]

[0086] 1...semiconductor device, 10...protection device, 11...voltage detection section, 12...output control section, Q1, Q2, Q3...switching elements, R1, R2, R3, R4, R5, R6, R7...resistors, C1, C2, C3...capacitors, D1, D2, D3...diodes

Claims

1. A voltage detection unit and an output control unit are provided, the voltage detection unit detects whether a first voltage supplied to a first node is higher than a second voltage; the output control unit includes a delay circuit that delays the first voltage and transmits it to a second node, and a first switch element that is configured to be able to output a voltage based on the first voltage in accordance with a voltage of the second node, the delay circuit is configured to set the first switch element to an open state in an initial state, When the supply of the first voltage is started, When the voltage detection unit detects that the first voltage is equal to or lower than the second voltage, the delay circuit brings the first switch element into a short-circuit state based on the voltage of the second node; When the voltage detection unit detects that the first voltage is higher than the second voltage, the delay circuit reduces the voltage of the second node to maintain the initial state. It is configured as follows: Protective device.

2. When the supply of the first voltage starts, the delay circuit gradually increasing the voltage of the second node; When the first voltage is equal to or lower than the second voltage, the first switch element is gradually brought into a short-circuit state. It is configured as follows: The protection device of claim 1.

3. The voltage detection unit detecting whether the first voltage is higher than the second voltage after the supply of the first voltage starts and before the first switch element is short-circuited; It is configured as follows: The protection device of claim 2.

4. the delay circuit includes a first resistor and a first capacitor; one end of the first resistor is connected to the first node, and the other end of the first resistor is connected to the second node; one end of the first capacitor is connected to the second node; The voltage detection unit When it is detected that the first voltage is higher than the second voltage, the charge stored in the first capacitor is discharged. It is configured as follows: The protection device of claim 1.

5. the output control unit further includes a second switch element connected to the first node via a first resistor and including a first end connected to a gate of the first switch element, a second end grounded, and a gate connected to the second node; The output control unit when the voltage of the second node is equal to or higher than a third voltage, the second switch element is brought into a short-circuit state, thereby bringing the first switch element into a short-circuit state; When the voltage of the second node is lower than the third voltage, the second switch element is set to an open state, thereby setting the first switch element to an open state. It is configured as follows: The protection device of claim 1.

6. the output control unit further includes a third switch element including a first end connected to the second node, a second end grounded, and a gate connected to the voltage detection unit; The voltage detection unit When it is detected that the first voltage is higher than the second voltage, a signal is output to a gate of the third switch element to put the third switch element into a short-circuit state; When it is detected that the first voltage is equal to or lower than the second voltage, a signal is output to a gate of the third switch element to place the third switch element in an open state. It is configured as follows:

6. The protection device of claim 5.

7. the voltage detection unit includes a voltage detector having a first terminal to which a voltage based on the first voltage is input, and detecting whether the first voltage is higher than the second voltage; The protection device of claim 1.

8. the voltage detection unit further includes a first resistor and a second resistor; one end of the first resistor is connected to the first node, and the other end of the first resistor is connected to the first end of the voltage detector; one end of the second resistor is connected to the first end of the voltage detector, and the other end of the second resistor is grounded; 8. The protection device of claim 7.

9. the voltage detection unit further includes a first diode; the first diode is a Zener diode, The cathode of the first diode is connected to the first end of the voltage detector, and the anode of the first diode is grounded.

8. The protection device of claim 7.

10. the output control unit further includes a discharge circuit for discharging the charge of the first capacitor when the supply of the first voltage to the first node is stopped.

5. The protection device of claim 4.

11. the discharge circuit includes a first diode; the first diode is a Schottky barrier diode, The cathode of the first diode is connected to the first node, and the anode of the first diode is connected to the second node.

11. The protection device of claim 10.

12. The voltage detection unit a first capacitor having one end connected to the first end of the voltage detector and the other end grounded; a discharge circuit for discharging the charge of the first capacitor when the supply of the first voltage to the first node is stopped; Further provided with 8. The protection device of claim 7.

13. the discharge circuit includes a first diode; the first diode is a Schottky barrier diode, a cathode of the first diode connected to the first node, and an anode of the first diode connected to the first end of the voltage detector and one end of the first capacitor; 13. The protection device of claim 12.

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