Electronic circuit for verifying integrity of switch

Abstract

The present disclosure relates to an electronic circuit (10) for verifying the integrity of a switch (7). The circuit comprises a voltage comparator (5) and a decoupling switch (1). The decoupling switch is configured to receive a drive signal (SG1) having a first logic value to enable monitoring of the comparison voltage (VDST) and to receive a monitoring enable signal (SDEN) having a first logic value to command opening of the decoupling switch (1). The electronic circuit is configured to generate an output monitoring signal (SDST) having a first logic value if the switch (7) is open and to generate an output monitoring signal (SDST) having a second logic value if the switch (7) is short-circuited.

Description

[0001] Description Technical Field of the Invention

[0002] The present invention generally relates to the field of electronic devices.

[0003] More specifically, the present invention relates to an electronic circuit for verifying the integrity of a switch. Prior Art

[0004] It is known that for safety reasons, switches are used to disconnect the supply voltage.

[0005] For example, in the automotive field, it is important to disconnect the supply voltage in the event of a failure of a component of a battery charger powered by the supply voltage of a battery charger installed on an electric vehicle.

[0006] One known technique for monitoring the condition of a switch is to use the desaturation function of a semiconductor-type switch, which makes it possible to detect whether an increase in the current flowing through the switch is excessive due to a failure of an electronic component powered by the same supply voltage: in this case, the switch can be disconnected to prevent the increase in its current from damaging the switch.

[0007] The applicant points out that the disadvantage of the desaturation function is that it cannot detect a short circuit of the switch, thus preventing the switch from disconnecting and causing a failure of the electronic components connected downstream of the switch or injecting an unwanted current into the power supply (e.g., a direct current from the battery to the mains power supply). Summary of the Invention

[0008] The present invention relates to an electronic circuit for verifying the integrity of a switch, as defined in the preferred embodiments described in appended claim 1 and dependent claims 2 to 8.

[0009] The applicant has recognized that the electronic circuit according to the present invention can detect the short-circuit condition of a switch placed between the supply voltage and an electronic component powered by the supply voltage, thus reducing the risk of damaging the electronic components or injecting an unwanted current into the power supply.

[0010] The basic idea is to use an additional switch, which is connected to the control terminal of the switch and is controlled according to a monitoring enable signal, in order to verify, for example, whether the switch is in a short-circuit condition before the switch is connected to the supply voltage.

[0011] Another object of the present invention is to provide an electronic power supply system, which is defined in the preferred embodiments described in appended claim 9 and dependent claims 10. Brief Description of the Drawings

[0012] Other features and advantages of the present invention will result from the description of the preferred embodiments and their variants provided by way of example with reference to the following drawings, in which: Figure 1 FIG. 2 shows a block diagram of an electronic power supply system according to an embodiment of the present invention, the electronic power supply system including an electronic circuit for verifying the integrity of a switch. DETAILED DESCRIPTION OF THE INVENTION

[0013] Note that in the following description, the same or similar blocks, components, or modules are denoted by the same numerical reference in the drawings, even if they are shown in different embodiments of the present invention.

[0014] REFERENCE Figure 1 , FIG. 3 shows a power electronic system 20 according to an embodiment of the present invention.

[0015] The electronic power supply system 20 is used, for example, to supply power to a battery charger installed on an electric vehicle.

[0016] The electronic system 20 includes a switch 7, an electronic circuit 10, a resistor 4, and a diode 6.

[0017] For the purpose of explaining the present invention, the protection switch 7 is considered, but more generally, the present invention can be applied to verify the integrity of any type of switch.

[0018] The switch 7 includes a first terminal adapted to receive a power supply voltage V_DC of any value, a second terminal including a connection to a ground reference voltage, and a control terminal adapted to receive an output drive signal S_G2, the output drive signal S_G2 commanding the switch 7 to switch between an open position and a closed position according to the value of the output drive signal S_G2 itself.

[0019] The switch 7 is, for example, an IGBT transistor or a MOSFET.

[0020] The electronic circuit 10 includes a first input terminal I1 adapted to receive a power supply voltage VDD, a second input terminal I2 adapted to receive a drive signal S_G1, a third input terminal I3 adapted to receive a monitoring enable signal S_D_EN, a first output terminal O1 adapted to generate an output drive signal S_G2 for driving the switch 7 to open or close, a second output terminal O2 adapted to generate an output monitoring signal S_DST representing the condition of the switch 7, and a third output terminal O3 for generating a comparison voltage V_DST.

[0021] A series connection of the resistor 4 and the diode 6 is placed between the third output terminal O3 and the first terminal of the switch 7 connected to the power supply voltage V_DC.

[0022] In particular, the resistor 4 includes a first terminal connected to the third output terminal O3 and a second terminal connected to the anode terminal of the diode 6.

[0023] The cathode terminal of diode 6 is connected to the first terminal of switch 7 (and thus to the supply voltage V_DC).

[0024] The electronic power supply system 20 operates according to two operating modes: Test mode; Normal operating mode after the test mode.

[0025] The test mode is activated before the supply voltage V_DC is supplied to the electronic system 20.

[0026] In particular, in the test mode, the integrity of switch 7 is verified, i.e., the ability of the switch to correctly switch between the condition where switch 7 is open and the condition where switch 7 is closed.

[0027] In particular, in the test mode, it is verified whether there is a short circuit (i.e., low impedance) in switch 7 by means of decoupling switch 1, which remains open by monitoring a first value (e.g., high logic value) of the monitoring enable signal S_D_EN.

[0028] In the normal operating mode, switch 7 is closed in order to transfer electrical energy from the supply voltage V_DC to the electrical / electronic components powered by it (e.g., a battery charger installed on an electric vehicle), and switch 7 is monitored in the case where a desaturation condition of switch 7 occurs due to overcurrent or incorrect driving of switch 7.

[0029] Specifically, in the normal operating mode, decoupling switch 1 remains closed by means of a monitoring enable signal S_D_EN having a second value (e.g., low logic value), and switch 7 also remains closed by means of a drive signal S_G1 having a first value (e.g., high logic value).

[0030] The electronic circuit 10 includes the following components: Voltage comparator 5; Decoupling switch 1; Resistor 3; Current generator 2; Voltage generator 9; Transistor 8, e.g., a transistor 8 of MOSFET type; Voltage inverter 11.

[0031] The combination of voltage comparator 5, current generator 2, voltage generator 9, transistor 8, and voltage inverter 11 implements a desaturation function during the normal operating mode to detect the presence of an overcurrent flowing through switch 7, which is caused, for example, by a fault or malfunction of an electrical or electronic component powered by the supply voltage V_DC.

[0032] The decoupling switch 1 has the function of allowing verification of whether the switch 7 is in a short-circuit (i.e., low-impedance) condition, for example, before the switch is connected to the supply voltage V_DC.

[0033] The electrical and electronic components of the electronic circuit 10 are electrically connected as Figure 1 shown.

[0034] Specifically, the current generator 2 includes a first terminal connected to the supply voltage VDD and a second terminal connected to the voltage comparator 5.

[0035] The voltage comparator 5 includes a negative terminal connected to the second terminal of the current generator 2 and a positive terminal connected to the reference voltage V_REF (e.g., equal to 7 volts).

[0036] The voltage comparator 5 can also be implemented using an operational amplifier.

[0037] The reference voltage V_REF is generated, for example, by a voltage generator 9 connected between the positive terminal of the voltage comparator 5 and the reference voltage grounded.

[0038] The transistor 8 (e.g., an n-channel MOSFET) includes a first terminal connected to the negative terminal of the voltage comparator 5 and the second terminal of the current generator 2, and includes a second terminal connected to the reference voltage grounded.

[0039] The negative terminal of the voltage comparator 5, the second terminal of the current generator 2, and the first terminal of the transistor 8 are connected together to form a third output terminal O3 of the electronic circuit 10 carrying the comparison voltage V_DST.

[0040] The voltage inverter 11 includes a first terminal adapted to receive the drive signal S_G1 and a second terminal connected to the control terminal of the transistor 8.

[0041] The voltage inverter 11 is implemented, for example, using a NOT logic gate.

[0042] The decoupling switch 1 includes a first terminal connected to the resistor 3, a second terminal connected to the control terminal of the switch 7 (and thus connected to the first output terminal O1), and a control terminal adapted to receive the monitoring enable signal S_D_EN from the third input terminal I3.

[0043] The resistor 3 is placed between the second input terminal I2 and the first terminal of the decoupling switch 1.

[0044] The output monitoring signal S_DST has two functions: During normal operation of the electronic power supply system 20, the output monitoring signal S_DST indicates the presence or absence of the desaturation state of the switch 7; During the test phase (usually before normal operation), the output monitoring signal S_DST indicates the presence or absence of a closed condition (i.e., a short circuit) of switch 7, or the output monitoring signal S_DST indicates the presence or absence of an open condition of switch 7.

[0045] The following truth table shows the possible values of the drive signal S_G1, the monitoring enable signal S_D_EN, the open (high impedance) or closed (short circuit, i.e., low impedance) condition of switch 7, the output monitoring signal S_DST, and the safe / fault condition of switch 7:

[0046] The following behavior can be observed in the table: First row: The logic value of the drive signal S_G1 is low, and the system 20 operates in the normal operation mode; Second and third rows: When the logic value of the drive signal S_G1 is high and the logic value of the monitoring enable signal S_D_EN is low, the decoupling switch 1 is driven to open, and the electronic system 20 can detect whether switch 7 is correctly opened by means of the output monitoring signal S_DST with a high or low logic value (the fault condition or safe condition of switch 7, respectively); Fourth and fifth rows: When the logic value of the drive signal S_G1 is high and the logic value of the monitoring enable signal S_D_EN is high, the decoupling switch 1 is driven to close, and the electronic system 20 can detect whether switch 7 is correctly closed by means of the output monitoring signal S_DST with a high or low logic value (the safe condition or fault condition of switch 7, respectively).

[0047] In other words, if switch 7 is driven to close during the test phase and switch 7 does close, then switch 7 operates correctly (fourth row of the table); conversely, if switch 7 is driven to close but switch 7 remains open, then switch 7 has a fault (fifth row of the table).

[0048] Similarly, if switch 7 is driven to open during the test phase and switch 7 does open, then switch 7 operates correctly (third row of the table); conversely, if switch 7 is driven to open but switch 7 remains closed, then switch 7 has a fault (second row of the table).

[0049] During the normal operation of the electronic power supply system 20, the decoupling switch 1 is closed and switch 7 is closed and a small voltage drop appears across switch 7; in addition, a current with a defined value (e.g., equal to 10 amperes) flows through switch 7.

[0050] The current generator 2 generates a current with a defined value (e.g., equal to 200 microamps), and this current flows through the resistor 4, the diode 6 (which is in the conducting state), and the switch 7 to the reference voltage at ground: Then an appropriate voltage value (e.g., equal to 3 volts) for the comparison voltage V_DST is generated at the negative terminal of the voltage comparator 5.

[0051] In the case where the components powered by the power supply voltage V_DC are free of faults or malfunctions, the voltage comparator 5 detects that the reference voltage V_REF on its positive terminal is greater than the comparison voltage V_DST on its negative terminal, and then generates an output monitoring signal S_DST with a high logic value, which high logic value indicates the correct operation of the electrical and / or electronic components powered by the power supply voltage V_DC.

[0052] On the other hand, in the case where one or more components powered by the power supply voltage V_DC have a fault or malfunction, a desaturation condition of the switch 7 occurs: the current flowing through the resistor 4 and the diode 6 increases to a high value, the voltage drop across the switch 7 increases (desaturation condition), and thus the value of the comparison voltage V_DST on the negative terminal of the voltage comparator (i.e., the voltage of the third output terminal O3) also increases.

[0053] Therefore, the voltage comparator 5 detects that the reference voltage V_REF on its positive terminal is lower than the comparison voltage V_DST on its negative terminal, and thus generates an output monitoring signal S_DST with a low logic value, which low logic value indicates a fault in one or more electrical and / or electronic components powered by the power supply voltage V_DC.

[0054] Therefore, the output monitoring signal S_DST can be used (e.g., by a processing unit) to control the opening of the switch 7, thereby preventing the switch 7 from being damaged.

[0055] During the test operation of the electronic power supply system 20, the drive signal S_G1 is activated (logic high state), the transistor 8 is open (i.e., it is in a high impedance state), and the comparison voltage monitoring V_DST is enabled: the decoupling switch 1 opens or closes according to the value of the monitoring enable signal S_D_EN.

[0056] In the case where the switch 7 is open (i.e., it is in a high impedance state), the transistor 8 is open, and thus the current generator 2 causes an increase in the comparison voltage V_DST.

[0057] Therefore, the voltage comparator 5 detects that the comparison voltage V_DST on its negative terminal is greater than the reference voltage V_REF on its positive terminal, and thus generates an output monitoring signal S_DST with a switching from a high logic value to a low logic value, indicating the open condition of the switch 7 (i.e., correct operation) (the third row of the table).

[0058] On the other hand, in the case where the switch 7 is in a short - circuit condition (i.e., the switch is closed, which means the switch is in a low - impedance state), the current generated by the current generator 2 flows through the resistor 4, the diode 6, and the switch 7 (which is short - circuited), causing the comparator voltage V_DST to be maintained at a value lower than the reference voltage V_REF.

[0059] Therefore, the voltage comparator 5 detects that the reference voltage V_REF on its positive terminal is greater than the voltage on its negative terminal, and thus it generates an output monitoring signal S_DST with a high logic value, which high logic value indicates the short - circuit (i.e., low - impedance) of the switch 7 (the fourth row of the table).

[0060] Therefore, during the test mode, the integrity of the switch 7 can be verified when the switch 7 is open (the second and third rows of the table) and when the switch 7 is closed (i.e., short - circuited, the fourth and fifth rows of the table), which is different from the prior - art desaturation - based circuits where detection is not allowed when the switch 7 is open.

[0061] It should be noted that, for the purpose of explaining the present invention, the case where the decoupling switch 1 is included within the electronic circuit 10 has been considered, but embodiments where the decoupling switch 1 is external to the electronic circuit 10 are also possible.

[0062] It should also be noted that, for the purpose of explaining the present invention, certain logic states of the signals (e.g., the drive signal S_G1 with a high - active logic) have been considered, but different active - logic states can also be used without changing the essence of the operation.

[0063] Finally, it should be noted that, in the test mode, before evaluating the integrity of the switch 7, sufficient time can be waited so that the signals can reach stable values.

Claims

1. An electronic circuit (10) for verifying the integrity of a switch (7), the circuit comprising: A first input terminal (I1) adapted to receive a supply voltage (VDD); A second input terminal (I2) adapted to receive a drive signal (S_G1); A third input terminal (I3) adapted to receive a monitoring enable signal (S_D_EN); A first output terminal (O1) adapted to generate an output control signal (S_G2) to drive the opening or closing of the switch (7); A second output terminal (O2) adapted to generate an output monitoring signal (S_DST) indicative of the condition of the switch (7); A voltage comparator (5) configured to compare a comparison voltage (V_DST) associated with a terminal of the switch connected to another supply voltage (V_DC) with a reference voltage (V_REF) and generate therefrom the output monitoring signal (S_DST); A decoupling switch (1) placed between the first output terminal (O1) and the second input terminal (I2), the decoupling switch being configured to switch between an open position and a closed position according to the value of the monitoring enable signal (S_D_EN); Wherein the decoupling switch is configured to: Receive the drive signal (S_G1) having a first logic value to enable monitoring of the comparison voltage (V_DST); Receive the monitoring enable signal (S_D_EN) having a first logic value to command the opening of the decoupling switch (1); And wherein the voltage comparator (5) is configured to generate the output monitoring signal (S_DST) having a first logic value when the switch (7) is open and generate the output monitoring signal (S_DST) having a second logic value when the switch (7) is closed.

2. The electronic circuit according to claim 1, wherein, The decoupling switch is configured to: Receive the drive signal (S_G1) having a first logic value to enable monitoring of the comparison voltage (V_DST); Receive the monitoring enable signal (S_D_EN) having a second logic value to command the closing of the decoupling switch (1); And wherein the voltage comparator (5) is configured to generate the output monitoring signal (S_DST) having a second logic value when the switch (7) is closed and generate the output monitoring signal (S_DST) having a first logic value when the switch (7) is open.

3. The electronic circuit according to claim 1 or 2, wherein, The decoupling switch includes: An input terminal electrically coupled to the second input terminal (I2); An output terminal electrically connected to the control terminal of the switch; A control terminal adapted to receive the monitoring enable signal (S_D_EN).

4. The electronic circuit according to any one of the preceding claims, further comprising a resistor (3) placed between the second input terminal (I2) and the decoupling switch (1).

5. The electronic circuit according to any one of the preceding claims, further comprising: A current generator (2) having a first terminal adapted to receive the supply voltage (VDD) and a second terminal connected to the first terminal of the voltage comparator; A transistor (8) having a first terminal connected to the first terminal of the voltage comparator and the second terminal of the current generator, a second terminal connected to a ground reference voltage, and a control terminal electrically coupled to the input terminal of the decoupling switch.

6. The electronic circuit according to claim 5, wherein: The transistor (8) is configured to receive the drive signal (S_G1) having a first logic value to enable monitoring of the comparison voltage (V_DST), and the transistor (8) is open; In the case where the switch (7) is open, the voltage comparator is configured to detect that the comparison voltage (V_DST) on one of its negative terminals is greater than the reference voltage (V_REF) on its positive terminal, and the voltage comparator is configured to generate the output monitoring signal (S_DST) having a first logic value indicating an open circuit of the switch; In the case where the switch (7) is short-circuited, the current generated by the current generator flows through the switch (7), and the voltage comparator is configured to detect that the comparison voltage (V_DST) on one of its negative terminals is less than the reference voltage (V_REF) on its positive terminal, and the voltage comparator is configured to generate the output monitoring signal (S_DST) having a second logic value indicating a short circuit of the switch.

7. The electronic circuit according to claim 5 or 6, further comprising: A voltage inverter (11) having an input terminal connected to the second input terminal (I2) and an output terminal connected to the control terminal of the transistor (8); A resistor (3) having a first terminal connected to the second input terminal (I2) and a second terminal connected to the input terminal of the decoupling switch.

8. The electronic circuit according to any one of the preceding claims, wherein, The decoupling switch is implemented with a MOSFET transistor or a bipolar junction transistor.

9. An electronic power supply system (20) comprising: A switch (7) disposed between a supply voltage (V_DC) and a ground reference voltage, the switch (7) being configured to switch between an open position and a closed position according to the value of an output control signal (S_G2); The electronic circuit according to any one of the preceding claims, wherein the first output terminal (O1) of the electronic circuit is connected to the control terminal of the switch (7) adapted to receive the output control signal (S_G2); Wherein the electronic circuit further comprises a third output terminal (O3) connected to the voltage comparator and adapted to generate the comparison voltage (V_DST), the third output terminal (O3) being electrically coupled to a switch terminal, Wherein the electronic system is configured to operate according to two operating modes: A test mode, in which the decoupling switch (1) is driven to open or close according to the value of the monitoring enable signal (S_D_EN), and the electronic circuit is configured to generate the output monitoring signal (S_DST) indicating the opening or closing of the switch (7); A normal operation mode, in which the decoupling switch (1) is closed and the switch (7) is closed, and the electronic circuit is configured to generate the output monitoring signal (S_DST) indicating the normal operation state of the switch (7) or indicating an over-current condition through the switch.

10. The electronic power supply system according to claim 9, further comprising a series connection of a resistor (4) and a diode (6) disposed between the third output terminal (O3) and the switch terminal.

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