Device for protecting electrical circuit coupled to power supply network from overvoltage

Abstract

The invention relates to a device for protecting an electrical circuit coupled to a power supply network, in particular a vehicle power supply network, from overvoltage, comprising: an electrical input for applying an input voltage; an electrical output for providing an output voltage to a power supply network or a connected circuit; and an electrical protection circuit having a detection section, a semiconductor switch and a limiting section, the semiconductor switch being arranged between the electrical input and the electrical output and being actuatable in such a way that the output voltage output at the electrical output can be interrupted, wherein the detection section is configured to actuate the semiconductor switch by means of an actuation voltage when a threshold value of the input voltage is reached in such a way that the output of the output voltage is interrupted, the detection section having a voltage threshold detection element, such as a Zener diode, and wherein the limit section is configured to limit the output voltage when the output voltage is interrupted. The control voltage for the semiconductor switch is limited.

Description

TECHNICAL FIELD

[0001] The invention relates to a device for protecting a circuit coupled to a power supply network, in particular a vehicle power supply network, from overvoltages. The device can be configured, for example, for protecting a circuit or a device coupled to a power supply network of a vehicle having a generator or a motor-generator.

[0002] The invention thus relates to the field of circuit technology, protection circuits, in particular to avoid damage in vehicle networks due to overvoltages. BACKGROUND

[0003] In different application scenarios, for example in vehicles having a generator, higher overvoltages can occur due to fluctuations in the load current. This can occur in particular when the connection to the vehicle battery has a relatively high impedance or is completely interrupted. Due to the inductance of the generator, higher induced voltages occur when the load current changes rapidly, which are discharged as voltage peaks. Here, the energy stored in the magnetic field of the generator is discharged in the form of a voltage rise, in whole or in part, into the vehicle network. This effect is generally referred to as "load dump".

[0004] A further effect comes from the limited speed of the charging regulator and the inductance of the field circuit, whereby the field current can only change at a limited speed. In the case of a disappearance of the load current, this likewise triggers a voltage rise.

[0005] Load dumps can cause severe damage to circuits or devices coupled to the vehicle network due to overvoltages. These can be sensors or actuators, for example.

[0006] Various strategies have been proposed in order to protect electrical devices from such voltage peaks. DE 102017 123 484 A1 describes an overvoltage protection circuit; from US 2002 / 0109952 A1 a high voltage protection circuit for a motor vehicle is known, which protects an electrical load from damage and / or current interruption under overvoltage conditions; US 2003 / 0223169 A1 describes an overvoltage protection circuit and a series conduction circuit for protecting an electrical load from damage caused by overvoltages. Finally, US 2004 / 0061379 A1 also describes a system for protecting a vehicle system from load dumps. In US 2014 / 0002941 A1 an overvoltage protection with a preloaded lock is described.

[0007] A protection circuit can be proposed in which the subsequent circuit part is protected by means of voltage limitation. Here, problems can arise when the circuit can only take up limited loads when it is faced with high-frequency repeated overvoltage pulses.

[0008] Furthermore, it is known to integrate a voltage limitation by means of a transient voltage suppression diode or Zener diode in the rectifier of the generator. This usually limits the voltage to approximately 80 V, so that this single and otherwise unaided protection is not sufficient to ensure comprehensive protection.

[0009] In known systems, in the event of an overvoltage, the voltage supply to the device to be protected is usually interrupted, and it is also possible to propose that a current is caused to flow through a resistor, by means of the heat generated by which the energy of the voltage peak is dissipated. This way places a significant load on the components, so that the circuit durability is only limited, especially in the case of frequent and / or long-lasting overvoltage pulses.

[0010] For example, a short circuit (English: Crowbar) can be carried out on the vehicle electrical system, in which a high current intensity is generated and also a relatively high local power loss occurs. Furthermore, it is also possible to cause a connection to be interrupted, in which no excessively high power loss occurs locally and no current flows, but the energy of the overvoltage is retained in other parts of the vehicle electrical system, for example in the transient voltage suppression diode of the generator. SUMMARY

[0011] It is an object of the present application to provide a device of the type mentioned at the outset, which is able to provide reliable and robust protection against overvoltage pulses for electrical components and which can be used durably and flexibly here.

[0012] The object is therefore achieved by a device for protecting an electrical circuit coupled to an electrical supply network, in particular a vehicle electrical supply network, from overvoltages. The device comprises an electrical input for applying an input voltage, for example for coupling to a generator of a vehicle. The device also comprises an electrical output for outputting an electrical output voltage to the electrical supply network and, if necessary, to an electrical circuit or consumer coupled to the electrical supply network. The device also comprises an electrical protection circuit, which has a detection section, a semiconductor switch and a limitation section. Here, the semiconductor switch is arranged between the electrical input and the electrical output and can be actuated in such a way that the output of the output voltage on the electrical output is interrupted or can be interrupted. Here, the detection section is configured to actuate the semiconductor switch by means of an actuation voltage in such a way that the output of the output voltage is interrupted or the power output via the electrical output is interrupted when a threshold value of the input voltage is reached or exceeded. Here, the detection section has a voltage threshold detection element, for example a Zener diode. Here, the limitation section is also configured to limit the actuation voltage for the semiconductor switch, in particular to a predetermined / defined maximum value, in the event of an interruption of the output voltage. Here, the detection section comprises a current regulation component for limiting the current flowing through the voltage threshold detection element.

[0013] Thereby, it is advantageously prevented that the semiconductor switch is damaged or destroyed due to a corresponding higher operating voltage acting on the semiconductor switch in the case of a larger overvoltage.

[0014] Advantageously, the device can also be designed to be able to withstand high loads by simple means and thus to withstand overvoltage pulses of almost arbitrary frequency and duration.

[0015] In the following, a "circuit" to be protected is understood in particular as a circuit, component and / or device which is coupled to a power supply network.

[0016] In the device, the semiconductor switch is in particular operated by an operating voltage of the detection section.

[0017] A "current sink" is understood in particular as a circuit which serves to limit the current in the event of an overvoltage and to ensure that no current which is harmful to the device flows. In particular, the occurring current strength is prevented from exceeding a predetermined value. Thus, in particular, an abnormally high current is prevented from occurring inside the device.

[0018] The current sink can be realized, for example, by means of a combination of a transistor, a resistor and a reference voltage. For example, a transistor can be used, the collector of which is connected to the output of the voltage to be limited, while the emitter is connected to ground. A resistor connected in series with the collector or between the base and the emitter can control the current flowing through the base of the transistor.

[0019] A stable reference voltage can be provided, for example, by means of a Zener diode in order to control the base-emitter voltage of the transistor.

[0020] When the input voltage exceeds a set value, the Zener diode begins to conduct. Here, the current sink limits the current flowing through the Zener diode to an allowed value.

[0021] The Zener diode together with the current sink monitors the input voltage and limits the current flow when the voltage exceeds a certain value; for example, a transistor is used in a regulating loop for this purpose.

[0022] In a design variant, the detection section comprises a Zener diode which is configured to block the current flow until the input voltage threshold is reached.

[0023] Thereby, the detection section can advantageously be formed in particular simply and with components which are readily available. In particular, the Zener diode serves as a sensor element for reaching or exceeding the input voltage threshold, since the current flow is enabled when the input voltage threshold is exceeded.

[0024] In a further design variant, the semiconductor switch is designed as a P-channel field effect transistor, in particular as a P-channel MOSFET (metal oxide semiconductor field effect transistor).

[0025] In a refinement, the gate port of the semiconductor switch, in particular of the semiconductor switch designed as a P-channel field effect transistor, is connected to the detection section via a transistor and is actuated by the detection section.

[0026] However, suitable P-channel MOSFETs are difficult to obtain on the market, for example P-channel MOSFETs suitable for a specified maximum test voltage of 207 V or other voltages of more than 200 V. The use of N-channel MOSFETs can be achieved by means of a circuit variant. Advantageously thereby, the selection of suitable components is wider.

[0027] In a further design variant, the semiconductor switch is designed as an N-channel FET, in particular as an N-channel MOSFET. These components advantageously have a better voltage resistance.

[0028] In contrast to the device circuit for N-channel transistors, for P-channel FETs, actuation with a gate voltage that is negative relative to the source voltage is used. If this possibility cannot be implemented directly, an alternative semiconductor switch actuation scheme can be implemented.

[0029] In a further design variant, the detection section is connected to the galvanic isolation element in such a way that, upon exceeding a threshold value of the input voltage, the semiconductor switch is actuated by the galvanic isolation element in such a way that the output of the output voltage is interrupted. This design variant can be used in particular for semiconductor switches with N-channel FETs.

[0030] In one embodiment, the current regulation component of the detection section is designed to limit the current flowing through the galvanic isolation element.

[0031] In a design variant, the galvanic isolation element comprises an opto-coupler, in particular an opto-coupler with a solar cell. The galvanic isolation element can for example be designed as an opto-coupler with a light-emitting diode and a solar cell. Advantageously, this opto-coupler can implement the function of limiting the semiconductor switch actuation voltage.

[0032] In a further design variant, the device is designed for protecting a power supply network in the event of a load dump, in particular in the case of a generator of a vehicle being coupled to the electrical input. In particular, a corresponding dimensioning of the components is specified here, so that the protection circuit can be protected from overvoltage pulses of the input voltage.

[0033] Further details and advantages of the application will now be explained in more detail on the basis of the embodiments shown in the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0034] In the drawings:

[0035] Figure 1 a schematic diagram of a first embodiment of a device with a P-channel field effect transistor; and

[0036] Figure 2 a schematic diagram of a second embodiment of a device with an N-channel field effect transistor. DETAILED DESCRIPTION

[0037] With reference to Figure 1 A schematic diagram of a first embodiment of a device with a P-channel field effect transistor is described.

[0038] The device 100 of the first embodiment has an electrical input 125 at which an input voltage can be applied. In the first embodiment of the device 100, the electrical input 125 is connected with a generator of a vehicle.

[0039] The device 100 further has an electrical output 130 via which an output voltage can be output. In the first embodiment, a certain circuit is coupled to the electrical output 130 as a consumer, for example a sensor. An example of a coupled sensor can be a radar sensor of a vehicle.

[0040] A connection line 120 extends from the electrical input 125 to the electrical output 130.

[0041] The device 100 further has a port 110 connected to a ground potential (English: ground, GND).

[0042] The device 100 comprises an electrical protection circuit having a detection section 135 and a limiting section 140 and a semiconductor switch T109 arranged in the connection line 120, wherein the detection section and the limiting section are coupled to the connection line 120.

[0043] The semiconductor switch T109, which is designed as a P-channel FET T109 in the first embodiment, is arranged between the electrical input 125 and the electrical output 130, so that a current flow to a circuit coupled to the electrical output 130 can be switched off or on by the semiconductor switch.

[0044] In this regard, the semiconductor switch T109 can be similar to a valve, which can switch off or on the current flow from the electrical input 125 to the electrical output 130.

[0045] The detection section 135 is designed to manipulate the semiconductor switch T109 via a manipulation voltage. In the first embodiment, the detection section 135 is designed to detect an overvoltage when the voltage exceeds, for example, 18 V or 47 V and, in this case, to output a manipulation voltage to the semiconductor switch T109, such that the circuit to be protected is separated from the input voltage.

[0046] In the first embodiment, the detection section 135 comprises a first resistor R117 in a first branch between the electrical input 125 and the port 110 connected to the ground potential, and a first transistor T102 connected downstream of the first resistor. In parallel thereto, a second resistor R118, a second transistor T104 downstream of the second resistor, and a third resistor R105 downstream of the second transistor are connected in a second branch.

[0047] The first branch and the second branch of the detection section 135 are coupled between the electrical input 125 and the semiconductor switch T109.

[0048] The base of the second transistor T104 of the second branch is connected to the first branch between the first resistor R117 and the first transistor T102. The base of the first transistor T102 is connected to the second branch between the second transistor T104 and the third resistor R105.

[0049] In the second branch, a Zener diode D103 is also arranged between the second resistor R118 and the second transistor T104, which points in the opposite direction from the electrical input 125 to the port 110 connected to the ground potential. That is, the Zener diode D103 blocks the current flow until the input voltage applied to the electrical input 125 reaches or exceeds a threshold value, which is, for example, 18 V or 47 V in the first embodiment.

[0050] Between the first branch and the second branch of the detection section 135 and the semiconductor switch T109, two further ports are arranged for a first branch and a second branch of a limiting section 140.

[0051] The limiting section 140 is similar in structure to the detection section 135. In the first branch of the limiting section 140, a fourth resistor R110 and a third transistor T101 are arranged. Conversely, in the second branch of the limiting section 140, a fourth transistor T103 and a fifth resistor R103 downstream of the fourth transistor are arranged. Here, the base of the fourth transistor T103 is connected to the first branch between the fourth resistor R110 and the third transistor T101. Conversely, the base of the third transistor T101 is connected to the second branch downstream of the fourth transistor T103.

[0052] The limiting section 140 is connected to the connection line 120 via two further lines. Here, a fifth transistor T107 is arranged in one of the lines, the base of which is connected to the second branch of the detection section 135 between the second resistor R118 and the Zener diode D103. In addition, the limiting section 140 also comprises a second Zener diode D104, which is arranged in the opposite direction from the connection line 120 in the other one of the lines.

[0053] The second Zener diode D104, as in the first embodiment, is designed to conduct in the opposite direction when a threshold value of, for example, 18 V or 47 V is reached or exceeded.

[0054] The limiting section 140 is also connected to the gate port of the semiconductor switch T109 via a control line 145. By means of this, a control voltage can be applied to the gate port of the semiconductor switch T109 in order to switch the electrical connection between the electrical input 125 and the electrical output 130 via the semiconductor switch.

[0055] By means of the circuit of the detection section 135, which cooperates with the limiting section 140 of the device, and the control of the semiconductor switch T109 described above, the occurrence of a voltage peak of, for example, 18 V or 47 V can be detected and, in this case, the semiconductor switch T109 is controlled via the gate port of the semiconductor switch, so that the circuit to be protected at the electrical output 130 of the device 100 is separated from the input voltage at the electrical input 125. At the same time, the limiting section ensures in this case that the control voltage is limited and the current is also limited by the current sink. In this way, the semiconductor switch T109 is protected from damage due to voltage peaks.

[0056] Reference is made to Figure 2 , the description of the first embodiment is referred to, and these elements are not described in detail again. In addition, for functionally and / or structurally similar elements, the same reference signs are used; this does not mean that these elements are necessarily the same components in the first embodiment. Figure 1

[0057] In the device 200 according to the second embodiment, an electrical input 125 and an electrical output 130 are also provided, between which an electrical semiconductor switch T105 is arranged.

[0058] In the second embodiment, the semiconductor switch T105 is designed as an N-channel FET T105. The switch is also arranged in such a way that the current flow to the circuit coupled to the electrical output 130 can be switched off or on by means of the switch.

[0059] ​However, in order to establish this connection, a positive control voltage with respect to the source port has to be provided at the gate port of the semiconductor switch T105. To provide this control voltage, a different control scheme is employed in the second embodiment.

[0060] A photo coupler 220 is provided, which serves as an electrical isolation element 220 and comprises a light emitting diode D124, which is arranged in a forward direction between the connection line 120 and a first Zener diode D103 of the detection and limiting section 235. The photo coupler 220 also has a solar cell D125, which is arranged in a forward direction in a control line between the connection line 120 and the gate port of the semiconductor switch T105.

[0061] When the input voltage at the electrical input 125 reaches or exceeds a threshold value of, for example, 18 V or 47 V, the photo coupler no longer provides a control voltage for the semiconductor switch T105, so that the semiconductor switch T105 interrupts the connection to the circuit to be protected at the electrical output 130.

[0062] In this embodiment, the control voltage is limited by limiting the current by the detection and limiting section 235. In particular, the photo coupler 220 is the component that ensures limiting the control voltage of the semiconductor switch T105.

[0063] In other words, the invention provides a device 100 with a protection circuit, which is essentially composed of two parts: a first part of the protection circuit (detection section 135) detects the occurrence of an overvoltage that exceeds a certain level and subsequently acts on a second part of the circuit (limiting section 140). In addition, the second part (in this case also including the semiconductor switch) functions as a kind of "valve" that is added to the supply line of the device to be protected. This valve interrupts the electrical connection to the circuit to be protected under the action of the first part. As a result, the overvoltage does not act on the circuit to be protected. The occurring overvoltage must therefore be completely borne by the valve without current flow and without the valve itself being damaged. The valve can in particular be embodied as a field effect transistor.

[0064] With appropriate dimensioning, the proposed protection circuit can withstand overvoltage events for almost unlimited lengths of time. In this way, damage is limited in the event of a fault, for which the protected circuit is separated from the power supply line for the required length of time.

[0065] List of reference signs

[0066] 100 device

[0067] 110 port (ground)

[0068] 120 connection line

[0069] 125 electrical input

[0070] 130 electrical output

[0071] 135 detection section

[0072] 140 limiting section

[0073] 145 control circuit

[0074] R103 resistor

[0075] R105 resistor

[0076] R110 resistor

[0077] R117 resistor

[0078] R118 resistor

[0079] T101 transistor

[0080] T102 transistor

[0081] T103 transistor

[0082] T104 transistor

[0083] T107 transistor

[0084] T109 semiconductor switch, P-channel FET

[0085] D103 voltage threshold sensing element, diode, Zener diode

[0086] D104 diode, Zener diode

[0087] 200 device

[0088] 220 electrical isolation element, opto-coupler

[0089] 235 detection and limiting section

[0090] T105 semiconductor switch, N-channel FET

[0091] D124 diode, light emitting diode (opto-coupler)

[0092] D125 diode, solar cell (opto-coupler)

Claims

1. An arrangement (100) for protecting a circuit coupled to a power supply network, in particular a vehicle power supply network, from overvoltages, the arrangement comprising: an electrical input (125) for applying an input voltage; an electrical output (130) for providing an output voltage to the power supply network or the coupled circuit; and an electrical protection circuit having a detection section (135), a semiconductor switch (T109) and a limiting section (140), wherein the semiconductor switch (T109) is arranged between the electrical input (125) and the electrical output (130) and can be actuated in such a way that the output of the output voltage at the electrical output (130) can be interrupted; wherein the detection section (135) is configured to actuate the semiconductor switch (T109) by means of an actuation voltage in such a way that the output of the output voltage is interrupted upon reaching a threshold value of the input voltage, wherein the detection section (135) has a voltage threshold detection element (D103), for example a Zener diode (D103), and wherein the limiting section (140) is configured to limit the actuation voltage for the semiconductor switch (T109) in the event of an output voltage interruption, wherein the detection section (135) comprises current regulation components (T102, T104) for limiting the current flowing through the voltage threshold detection element (D103).

2. The arrangement (100) according to claim 1, characterized in that the current regulation components (T102, T104) comprise two transistors (T102, T104).

3. The arrangement (100) according to one of the preceding claims, characterized in that the detection section (135) comprises a Zener diode (D103) which is configured to block current flow before the threshold value of the input voltage is reached.

4. The arrangement (100) according to one of the preceding claims, characterized in that the semiconductor switch (T109) is designed as a P-channel field effect transistor (T109).

5. The arrangement (100) according to claim 3, characterized in that a gate port of the semiconductor switch (T109) is connected to the detection section (135) via a transistor (T107) and is actuated by the transistor (T107).

6. The arrangement (100) according to one of claims 1 to 3, characterized in that the semiconductor switch (T105) is designed as an N-channel FET (T105).

7. The arrangement (200) according to claim 6, characterized in that the detection section (235) is connected to an electrical isolation element (220) in such a way that, upon exceeding the threshold value of the input voltage, the semiconductor switch (T105) is actuated by the electrical isolation element (220) in such a way that the output of the output voltage is interrupted.

8. The arrangement (100) according to claim 7, characterized in that ​ The current regulating means (T102, T104) of the detection section (135) are designed to limit the current flowing through the galvanic isolation element (220).

9. The device (100) according to claim 7 or 8, characterized in that The galvanic isolation element (220) comprises an opto-coupler (220), in particular with a solar cell (D125).

10. The device (100) according to one of the preceding claims, characterized in that The device (100) is designed for protecting a power supply network in the event of a load surge, in particular in the case of a generator of a vehicle being coupled to the electrical input.

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