Protection circuit

Abstract

Protection Circuit This description relates to a protection circuit (100) comprising: at least one transistor (102) having a first conduction node connected to a first node (N1) and a second conduction node connected to a second node (N2), the first node (N1) being configured to be connected to a ground-referenced power supply (140), and the second node (N2) being configured to be connected to a ground-referenced load (130); a control circuit (160) connecting a control node (NG) of said at least one transistor to ground and configured to disable said at least one transistor (102) when an overvoltage or overcurrent occurs; at least one first transient voltage suppression diode (116) having its anode connected to a third node (N3) and its cathode connected to the first node (N1);at least one second diode (120) having its anode connected to the third node (N3) and its cathode connected to the control node of said at least one transistor (102); a controllable rectifier arrangement connecting the second node (N2) to ground; and a third diode (150) having its cathode connected to the control node of the rectifier arrangement. Figure for the abbreviation: Fig. 1;

Description

Title of the invention: Protection circuit technical field

[0001] This description relates generally to the field of power electronic circuits and more particularly to protection circuits adapted for protection against overvoltages or overcurrents. Previous technique

[0002] Nowadays, it is useful to equip electronic systems and devices with overvoltage and overcurrent protection circuits. For example, in systems operating at high voltages of hundreds of volts, cables can store energy that causes overvoltages, significant current variations, or overcurrent interruptions. This energy must be dissipated without damaging the components. Summary of the invention

[0003] There is a need to provide protection circuits with improved energy dissipation at reasonable costs.

[0004] An embodiment overcomes all or part of the drawbacks of known protection circuits.

[0005] One embodiment provides a protection circuit comprising: - at least one transistor having a first conduction node connected to a first node and a second conduction node connected to a second node, the first node being configured to be connected to a ground-referenced power source, and the second node being configured to be connected to a ground-referenced load; - a control circuit connecting a control node of said at least one transistor to ground and which is configured to disable said at least one transistor when an overvoltage or overcurrent occurs; - at least one first transient voltage suppression diode having its anode connected to a third node and its cathode connected to the first node; - at least one second diode having its anode connected to the third node and its cathode connected to the control node of said at least one transistor; - a controllable rectification arrangement connecting the second node to ground; and - a third diode having its cathode connected to the control node of the rectifier arrangement.

[0006] According to one embodiment, the controllable rectifier arrangement consists of at least one thyristor.

[0007] According to one embodiment, the controllable rectification arrangement consists of at least one triac in series with at least one reverse biased diode.

[0008] According to one embodiment, the third diode has its anode connected to the third node.

[0009] According to one embodiment, the protection circuit includes at least a second transient voltage suppression diode having its anode connected to the anode of the third diode.

[0010] According to one embodiment, said second transient voltage suppression diode has its cathode connected to the first node.

[0011] According to one embodiment, the avalanche voltage of the first transient voltage suppression diode is less than the avalanche voltage of the second transient voltage suppression diode.

[0012] According to one embodiment, said at least a second transient voltage suppression diode has its cathode connected to ground.

[0013] According to one embodiment, the protection circuit comprises a plurality of transistors, each having: - a conduction node connected to the first node; and - a conduction node connected to the second node; the control nodes of the transistors of the plurality being connected to each other.

[0014] According to one embodiment, the protection circuit further comprises a plurality of second diodes, each having their anode connected to the third node and their cathode connected to the respective control node of the transistors of the plurality.

[0015] According to one embodiment, said at least one transistor or plurality of transistors are of the MOSFET or IGBT type.

[0016] According to one embodiment, said first or second transient voltage suppression diodes comprise two transient voltage suppression diodes in series.

[0017] According to one embodiment, the avalanche voltage of the first transient voltage suppression diode is greater than the supply voltage.

[0018] According to one embodiment, the protection circuit comprises several transistors, each having a first conduction node connected to the first node and a second conduction node connected to the second node; said control circuit being configured to disable all said transistors when an overvoltage or overcurrent occurs.

[0019] One embodiment provides an energy conversion circuit comprising: - a power source referenced to ground; - a load referenced to mass; - the protection circuit as described, in which the first node of the protection circuit is connected to the power source and the second node of the protection circuit is connected to the load.

[0020] One embodiment provides for a vehicle comprising: - a power source referenced to ground; - a load referenced to mass; - the protection circuit as described, in which the first node of the protection circuit is connected to the power source and the second node of the protection circuit is connected to the load.

[0021] According to one embodiment, the load is a battery to be charged.

[0022] One embodiment provides a method for using the protection circuit such that described, including the use of the controllable rectifier arrangement and the transient voltage suppression diode to dissipate energy when an overvoltage or overcurrent occurs. Brief description of the drawings

[0023] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0024] [Fig.1] represents an embodiment of a protection circuit;

[0025] [Fig.2] represents an embodiment of a protection circuit;

[0026] Figure 3 represents an embodiment of a protection circuit; and

[0027] [Fig.4] represents an embodiment of a protection circuit. Description of the implementation methods

[0028] The same elements have been designated by the same reference numerals in the different figures. In particular, structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0029] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been represented and are detailed.

[0030] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or linked through one or more other elements.

[0031] In the following description, when referring to absolute positional qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative, such as the terms "above", "below", "superior", "inferior", etc., or to orienting qualifiers, such as the terms "horizontal", "vertical", etc., it refers, unless otherwise specified, to the orientation of the figures.

[0032] Unless otherwise specified, the expressions "approximately", "roughly", and "on the order of" mean within 10% or 10°, preferably within 5% or 5°.

[0033] Many power applications use DC-DC or AC-DC power converters to power a load or to charge a battery, for example. In the event of a short circuit or overcurrent, a switch, also called a circuit breaker, which may be a MOSFET or IGBT transistor, for example, is triggered to open the circuit to protect other components. Due to the parasitic inductance of the wiring harness or an inductive load, an overvoltage or overcurrent can be generated across the transistor and exceed its absolute maximum ratings, thus leading to destruction or degradation.

[0034] One solution consists of active clipping with a transient voltage suppression diode between the drain and gate (in the case of a MOSFET) or between the collector and gate (in the case of an IGBT). During active clipping, the power dissipation is distributed between the MOSFET or IGBT transistor and the transient voltage suppression diode. However, in the case of a high operating voltage or a high current cutoff, the power dissipated by the transient voltage suppression diode and the transistor may be too high. Various solutions can be applied to limit this dissipation.

[0035] To limit energy losses using a transient voltage suppression diode, one solution could be to add a resistor in series. This solution results in a higher clipping voltage and may be sufficient to limit the power dissipated. Energy can also be dissipated by means of the printed circuit board to which the transistor is soldered. However, the costs and surface area involved are too high. Another solution could be to add several transient voltage suppression diodes, which adds costs and leads to a dispersion of voltage and temperature breakdown values. In all cases, the use of one or more transient voltage suppression diodes does not solve the transistor's power dissipation problem.

[0036] Another solution could be the use of a freewheeling diode. However, this latter solution cannot be implemented directly when the load is a battery, since a reverse-biased battery connection must be provided. One drawback, in the case of a very high switching current, lies in the delay which can appear before the freewheeling diode is fully conductive, causing an excessively high voltage peak across the transistor.

[0037] To limit power losses in the transistor, one solution could be to increase the active area of ​​the transistor or increase the number of transistors. A larger heat sink could also be used. However, these solutions consume surface area and are expensive.

[0038] To overcome these drawbacks, the proposed embodiments describe a protection circuit comprising: - at least one transistor having a first conduction node connected to a first node and a second conduction node connected to a second node, the first node being configured to be connected to a ground-referenced power source, and the second node being configured to be connected to a ground-referenced load; - a control circuit connecting a control node of said at least one transistor to ground and which is configured to disable said at least one transistor when an overvoltage or overcurrent occurs; - at least one first transient voltage suppression diode having its anode connected to a third node and its cathode connected to the first node; - at least one second diode having its anode connected to the third node and its cathode connected to the control node of said at least one transistor; - a controllable rectification system, connecting the second node to ground; and - a third diode having its cathode connected to the control node of the controllable rectifier arrangement.

[0039] The controllable rectification arrangement consists of at least one thyristor or at least one triac in series with at least one reverse-biased diode.

[0040] This solution allows for the rapid clipping of the overvoltage initially by the transient voltage suppression diode, while the thyristor activates more slowly to create a freewheeling dissipation loop in the wiring harness inductance. Subsequently, the energy is short-circuited by the complete triggering of the thyristor, which creates a discharge freewheeling loop with the parasitic inductance of the cables or the load. The remaining voltage is then reduced, and the circuit to be protected is safe.

[0041] One advantage is that slow clipping occurs across the transistor during the switch-off. Another advantage is that low energy is dissipated in the transistor and the transient voltage suppression diode during a switch-off.

[0042] The described embodiments make it possible to keep the number of transistors or the size of the transistors low in order to ensure the dissipation of energy from the transistor.

[0043] Moreover, since this solution leads to lower internal heating by short-circuiting the energy dissipation, the dispersion in the components due to a self-heating temperature is reduced.

[0044] Fig. 1 represents a first embodiment of a protection circuit 100. More particularly, the protection circuit 100 is a circuit for protection against overvoltages which appear after protection against an overcurrent also called overcurrent.

[0045] In the example shown, the protection circuit 100 includes at least one transistor 102, which is, for example, a MOSFET or an IGBT. The transistor 102 has a first conduction node connected, preferably connected, to a first node N1 and a second conduction node connected, preferably connected, to a second node N2. The first node is configured to be connected, preferably connected, to a ground-referenced power supply 140. In one example, the power supply could be a battery. The second node N2 is configured to be connected, preferably connected, to a ground-referenced load 130 (LOAD).

[0046] In the example shown, the protection circuit 100 also includes a control circuit 160 (GATE DRIVER) connecting a control node NG of the transistor 102 to ground, for example, via a series resistor 119. The control circuit 160 is configured to turn off the transistor 102 when an overvoltage or overcurrent occurs. In one example, the control circuit 130 applies a zero or negative voltage to the MOSFET transistor that drives the node to turn it on. The control circuit includes, for example, a shunt resistor in series with the load, and when a difference across the shunt resistor reaches a threshold, the transistor is then turned off.

[0047] In the example shown, the protection circuit 100 further includes at least one transient voltage suppression (TVS) diode 116 having its anode connected, preferably connected, to a third node N3 and its cathode connected, preferably connected, to the first node NI. In one example, the TVS 116 consists of two or more TVS diodes in series to obtain a higher avalanche voltage. In the figures, transient voltage suppression diodes are represented with the symbol for a Zener diode. The TVS 116 is, for example, adapted to withstand, across its terminals, a voltage generated by the power supply 140.

[0048] In one example, the avalanche voltage of the TVS 116 is greater than the supply voltage.

[0049] The use of TVS may be preferable to the use of a Zeener diode because it has higher voltage breakdown breaking capacities. In Figure 1, the protection circuit 100 includes at least one diode 120, the anode of which is preferably connected to the third node N3 and its cathode connected to the control node NG of transistor 102. Diode 120 has, for example, an avalanche voltage higher than the gate voltage present at node NG. In other words, the reverse voltage of diode 120 is higher than the voltage present at node NG, which can exceed 22 V. Diode 120 prevents current from flowing through the TVS 116 when a positive voltage is applied to node NG to turn on transistor 102. In the illustrated example, the protection circuit 100 includes at least one thyristor 110 (cathode-triggered thyristor) connecting the second node N2 to ground. In this example, a diode 150 has its cathode connected to the control node of the thyristor 110 and its anode connected, preferably, to the third node N3. The diode 150 helps balance voltages and, if a battery is used as a load, prevents reverse battery voltage.

[0050] A thyristor, also called a silicon-controlled rectifier (SCR), is a bipolar power device with a gate, i.e., a control node, controlled by a current level. The main current flows from the anode to the cathode when the gate current is sufficiently high and prevents current flow otherwise. The thyristor remains open if no current flows through its gate or control node.

[0051] In an example not shown, the thyristor is replaced by a triac, connecting the second node N2 to ground. In this case, the control node of the triac is connected to the cathode of diode 150 and a reverse-biased diode is connected, preferably connected, in series with the triac to prevent current conduction from N2 to ground (the cathode of the diode being directed towards node N2).

[0052] The thyristor 110, or the triac in series with the reverse-biased diode, constitutes the rectification arrangement, controllable by means of the thyristor gate or the triac gate.

[0053] The example described concerns a thyristor constituting the controllable rectification arrangement, but it will be understood that in each of the and all embodiments, this thyristor can be replaced by a triac in series with a reverse biased diode.

[0054] During operation, at the moment of an overvoltage, overcurrents ranging from more than 1,000 A up to 2,500 A occur across the terminals of transistor 102; the control circuit 160 opens transistor 102. With very high voltages, for example, more than 500 V, for example, 900 V, the inductance of the cable bundle or The load inductance can always add an additional overvoltage to the protection circuit on top of the supply voltage. Initially, this overvoltage becomes sufficiently high, exceeding the avalanche voltage, to cause the TVS 116 to conduct. This triggers the overvoltage to be suppressed in less than 0.1 ps, for example, 1 ns, but also reactivates the transistor and the thyristor 110 (or triac). Since the complete blocking of the thyristor (or triac) takes longer than the TVS to reach the conduction state, the TVS 116 initially dissipates some of the energy and lowers the overvoltage when it reaches its avalanche voltage. The voltage applied to the control node is then lowered, and the transistor is turned on again.Meanwhile, when the thyristor (or triac) becomes fully locked, it creates a freewheeling loop that discharges the remaining energy into the cable bundle inductance. The thyristor (or triac) remains active until the current is low and the voltage across the TVS falls below its avalanche voltage. The thyristor (or triac) remains active even when no longer driven until the current through it becomes sufficiently low (also called the holding current), for example, below a few dozen mA. In other words, during active clipping protection, the TVS 116 becomes conductive when its avalanche voltage is reached, causing transistor 102 to become partially conductive again.Consequently, the overvoltage across the TVS 116 decreases below its avalanche voltage and, when this voltage decreases sufficiently, the transistor 102 becomes blocked again which in turn creates the overvoltage again leading to the conduction of the TVS 116 and the whole process described above is repeated.

[0055] This architecture, combining a TVS between the control node and the first conduction node of the transistor with a freewheeling thyristor loop, allows for a rapid response to dissipate energy, and then the remaining energy is safely dissipated in the freewheeling loop. The clipping voltage thus remains lower than the absolute maximum rated characteristics of the transistor, and the number of transistors necessarily remains small.

[0056] In one example, diodes 120 and 150 are PN diodes, that is, diodes formed in a semiconductor substrate, or Schottky diodes.

[0057] Fig. 2 represents an embodiment of a protection circuit 200.

[0058] Circuit 200 of [Fig. 2] is similar to circuit 100 of [Fig. 1] except that the Diode 150 has its anode connected to the anode of another TVS 216. The TVS 216 has its cathode connected to node NI. In this example, the anode of diode 150 is therefore disconnected from node N3.

[0059] In one example, the avalanche voltage of TVS 116 is lower than the avalanche voltage of TVS 216 in order to first turn on transistor 102, and thus allow for a fast response. This condition allows TVS 116 to be activated first so that active clipping occurs first and to ensure that the voltage across transistor 102 is lower than its maximum rated characteristics (AMR).

[0060] In one example, TVS 116 and 216 comprise two or more TVS in series.

[0061] Figure 3 represents an embodiment of a protection circuit 300.

[0062] Circuit 300 of [Fig. 3] is similar to circuit 200 of [Fig. 2], except that the TVS 216 has its cathode connected to ground in order to obtain a compromise between the TVS breakdown voltage and the response time to activate active clipping and the thyristor (or triac).

[0063] [Fig.4] represents an embodiment of a protection circuit 400. The circuit 400 of [Fig.4] is similar to the circuit 100 of [Fig.1], except that instead of having only one transistor 102, a plurality of, for example eight, transistors 102, 411, 421, 431, 441, 451, 461, 471, are arranged in parallel with their conduction nodes connected to node NI and respectively N2. Each transistor 102, 411, 421, 431, 441, 451, 461, 471 of the plurality has its control node, i.e. its gate, connected to node N3 by means of a diode 401, 402, 403, 404, 405, 406, 407, for example similar to diode 120. In this example, the cathodes of diodes 401, 402, 403, 404, 405, 406, 407 are connected to the control node of the respective transistor 102, 411, 421, 431, 441, 451, 461, 471.

[0064] Each transistor 102, 411, 421, 431, 441, 451, 461, 471 of the plurality has its control node, i.e. its gate, connected to the control circuit 160 via a respective resistance 119, 419, 429, 439, 449, 459, 469, 479.

[0065] In the illustrated example, the TVS 116 comprises two TVS in series.

[0066] In the example of [Fig.4], the control circuit includes a resistor of A bypass resistor 410 is connected in series between the load 130 and node N2. The voltage across the bypass resistor 410, or the current flowing through it, is monitored by an amplifier 430. When the detected current or voltage exceeds a threshold, for example, the state of the amplifier's output signal is modified. A gate driver 420 of the control circuit 160 responds by blocking the transistors, modifying the voltage applied to their control nodes.

[0067] In one example, the 420 gate driver is included in an integrated circuit.

[0068] The application area of ​​the protection circuits described is, for example Automotive applications, for example, include charging electric vehicles and on-board chargers (OBCs). Uninterruptible power supplies (UPS) and industrial power supplies are also affected by this use. The protection circuits described are also applicable to DC-DC or AC-DC converter circuits, as well as electronic functions for powering a load or charging a battery. Furthermore, the described protection circuits can be implemented in powertrains, motor control systems, induction heating systems, or photovoltaic module control systems.

[0069] As a general characteristic, the protection circuits described can be used in applications that deal with high voltages, for example, a few hundred volts.

[0070] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will be apparent to those skilled in the art. Preferably, the controllable rectifier arrangement comprises a single thyristor or a single triac in series with a single diode.

[0071] Finally, the practical implementation of the described embodiments and variants is within the grasp of a person skilled in the art, based on the functional indications given above. In particular, the control circuit can be implemented by a person skilled in the art in various ways, provided that, when an overvoltage or overcurrent occurs in the circuit, the control circuit applies a voltage to the transistor's control node so that the transistor is switched off when the overvoltage or overcurrent is detected. A person skilled in the art will also be able to adapt the voltage applied to the transistor according to the type of transistor involved.

Claims

Demands

1. Protection circuit (100, 200, 300, 400) comprising: - at least one transistor (102) having a first conduction node connected to a first node (N1) and a second conduction node connected to a second node (N2), the first node (N1) being configured to be connected to a ground-referenced power supply (140), and the second node (N2) being configured to be connected to a ground-referenced load (130); - a control circuit (160) connecting a control node (NG) of said at least one transistor to ground and configured to disable said at least one transistor (102) when an overvoltage or overcurrent occurs; - at least one first transient voltage suppression diode (116) having its anode connected to a third node (N3) and its cathode connected to the first node (N1);- at least one second diode (120) having its anode connected to the third node (N3) and its cathode connected to the control node of said at least one transistor (102); - a controllable rectifier arrangement connecting the second node (N2) to ground; and - a third diode (150) having its cathode connected to the control node of the rectifier arrangement.

2. Protection circuit according to claim 1, wherein the controllable rectification arrangement consists of at least one thyristor.

3. Protection circuit according to claim 1, wherein the controllable rectification arrangement consists of at least one triac in series with at least one reverse biased diode.

4. Protection circuit according to any one of claims 1 to 3, wherein the third diode (150) has its anode connected to the third node (N3).

5. Protection circuit according to any one of claims 1 to 4, wherein the protection circuit comprises at least one second transient voltage suppression diode (216) having its anode connected to the anode of the third diode (150).

6. Protection circuit according to claim 5, wherein said at least one second transient voltage suppression diode (216) has its cathode connected to the first node (NI).

7. Protection circuit according to claim 6, wherein the avalanche voltage of the first transient voltage suppression diode (116) is less than the avalanche voltage of the second transient voltage suppression diode (216).

8. Protection circuit according to claim 5, wherein said at least one second transient voltage suppression diode (216) has its cathode connected to ground.

9. A protection circuit according to any one of claims 1 to 8, comprising a plurality of transistors (102, 411, 421, 431, 441, 451, 461, 471) each having: - a conduction node connected to the first node (NI); and - a conduction node connected to the second node (N2); the control nodes of the transistors of the plurality being connected to each other.

10. Protection circuit according to claim 9, further comprising a plurality of second diodes (120, 401, 402, 403, 404, 405, 406, 407) each having their anode connected to the third node (N3) and their cathode connected to the respective control node of the transistors of the plurality.

11. Protection circuit according to claim 8 or 9, wherein said at least one transistor or plurality of transistors are of the MOSFET or IGBT type.

12. Protection circuit according to claim 3 and any one of claims 4 to 11, wherein said first or second transient voltage suppression diodes (116, 216) comprise two transient voltage suppression diodes in series.

13. Protection circuit according to any one of claims 1 to 12, wherein the avalanche voltage of the first transient voltage suppression diode (116) is greater than the supply voltage (140).

14. A protection circuit according to any one of claims 1 to 13, wherein the protection circuit (100, 200, 300, 400) comprises several transistors (102), each having a first node conduction connected to the first node (NI) and a second conduction node connected to the second node (N2); said control circuit (160) being configured to disable all said transistors (102) when an overvoltage or overcurrent occurs.

15. Power conversion circuit comprising: - a ground-referenced power supply (140); - a ground-referenced load (130); - the protection circuit according to any one of claims 1 to 14, wherein the first node (NI) of the protection circuit is connected to the power supply and the second node (N2) of the protection circuit is connected to the load.

16. Vehicle comprising: - a ground-referenced power supply (140); - a ground-referenced load (130); - the protection circuit according to any one of claims 1 to 14, wherein the first node of the protection circuit is connected to the power supply and the second node of the protection circuit is connected to the load.

17. Energy conversion circuit according to claim 15 or vehicle according to claim 16, wherein the load is a battery to be charged.

18. Method of using the protection circuit (100, 200, 300, 400) according to any one of claims 1 to 14, comprising the use of the controllable rectifier arrangement and the transient voltage suppression diode (116) to dissipate energy when an overvoltage or overcurrent occurs.

Images