Power supply system with protection against current variations

Abstract

A power supply system (50) is disclosed, comprising a power supply circuit (1), a sensor (3) of a current (I_HV+) flowing through a terminal of the power supply circuit and a protection circuit (2). The protection circuit comprises a differentiator (2-1; 2-2, 2-3) adapted to measure a slope of a current measurement signal (S1_ms) and comprises a drive stage. The power supply circuit (1) is configured to receive a disconnect signal (S1_dsn) and, alternatively, depending on a value of the disconnect signal (S1_dsn), to electrically connect internal components of the power supply circuit to terminals of the power supply circuit or to electrically disconnect the internal components of the power supply circuit from the terminals of the power supply circuit.

Description

[0001] TECHNICAL FIELD

[0002] The present invention relates to the electronic field in general.

[0003] More particularly, the present invention relates to a power supply system equipped with an electronic circuit for protecting the power supply circuit of the same system in case of sudden variation of the current at the input of the same power supply circuit. PRIOR ART

[0004] In the automotive field, a direct current-direct current voltage converter (DC-DC) (in hybrid or electric vehicles) is used to be connected on one side to a high-voltage battery (for example, 400 V) to power the electric motor of the vehicle, while on the other side to a low-voltage battery (for example, 12 V) to power the electrical services in the passenger compartment of the same vehicle.

[0005] The DC-DC converter therefore works bidirectionally in order to power both the low-voltage side and the high-voltage side.

[0006] In the event of overcurrent at the input of the DC-DC converter (i.e. too high peak current value), DC-DC converter protection circuits are known.

[0007] It is also possible that the event of sudden variation of the current at the input of the DC-DC converter occurs, for example, in the event of simultaneous switching on of a plurality of electrical / electronic devices on the low-voltage side, or in the event of failure of the battery on the low-voltage or high-voltage side, or in the event of failure of an electrical component of the vehicle: in such cases, it is necessary to protect the DC-DC converter from the sudden variation of its input current in order to prevent damage to the DC-DC converter itself.

[0008] The Applicant has observed that the known overcurrent protection circuits do not allow to detect the event of sudden variation of the current at the input of the DC-DC converter with sufficient reliability and speed, thus increasing the risk of damaging it.

[0009] BRIEF SUMMARY OF THE INVENTION

[0010] The present invention, as defined in the preferred embodiments of the attached claims 1 and 2 to 9 depending therefrom, relates to a power supply system with protection against sudden variation of the input current.

[0011] The basic idea is to use a protection circuit with differentiator that is able to detect the sudden variation of the current at the input of the power supply circuit and then quickly disconnect the power supply circuit from the side where the sudden variation of the current has occurred.

[0012] The Applicant has realized that the power supply system according to the present application allows to reliably detect a sudden variation of the current at the input of the power supply circuit in a reduced time, regardless of the absolute value of the input current.

[0013] Another object of the present application is a vehicle with an electric motor or a hybrid vehicle with a thermal / electric motor, as defined in the appended claim 10. BRIEF DESCRIPTION OF DRAWINGS

[0015] The additional features and advantages of the present application will become more apparent from the following description of preferred embodiments, given by way of example only, thereof with reference to the accompanying drawings, in which:

[0016] - Figure 1A a block diagram of a power supply system according to a first embodiment of the present application is shown;

[0017] - Figure 1B a block diagram of a power supply system according to a second embodiment of the present application is shown;

[0018] - Figure 2 an electronic protection circuit included in the power supply system of Figure 1A and Figure 1B is shown;

[0019] - Figure 3 possible trends of some signals used in the power supply system of Figure 1A and in the electronic protection circuit of Figure 2 are schematically shown. DETAILED DESCRIPTION

[0021] It should be observed that in the following description, identical or similar blocks, components or modules are denoted with the same reference numerals in the figures, even if they are shown in different embodiments of the present application.

[0022] Reference is made to Figure 1A which shows a block diagram of a power supply system 50 according to a first embodiment of the present application.

[0023] The power supply system 50 comprises a power supply circuit 1, a first battery 40, a first load 45, a second battery 41, a second load 46, a current sensor 3 and a protection circuit 2.

[0024] The power supply circuit 1 comprises a first pair of terminals HV+, HV- and a second pair of terminals LV+, LV-.

[0025] The first battery 40 is connected in parallel to the first pair of terminals HV+, HV-.

[0026] The first load 45 is connected in parallel to the first battery 40.

[0027] The second battery 41 is connected in parallel to the second pair of terminals LV+, LV-.

[0028] The second load 46 is connected in parallel to the second battery 41.

[0029] The power supply circuit 1 is, for example, a direct current-direct current voltage converter (DC-DC) or (with appropriate circuit changes) an alternating current-direct current voltage converter (AC-DC) or a direct current-alternating current voltage converter (DC-AC).

[0030] For the purposes of explaining the present invention, the power supply circuit 1 is considered below as a DC-DC voltage converter, but the following considerations can be similarly made for other types of power supply circuits.

[0031] The DC-DC converter 1 converts the voltage between two different direct current voltage levels indicated with a first direct current voltage level AHV (also referred to as "high voltage") and a second direct current voltage level ALV (also referred to as "low voltage").

[0032] In addition, the converter DC-DC 1 is bidirectional, i.e. it is able to perform:

[0033] - a conversion from the high direct current voltage level AHV to the low direct current voltage level ALV (indicated as "buck" mode), then the first pair of terminals HV+, HV- are input terminals, while the second pair of terminals LV+, LV- are output terminals;

[0034] - a conversion from the low direct current voltage level ALV to the high direct current voltage level AHV (indicated as "boost" mode), then the first pair of terminals LV+, LV- are input terminals, while the second pair of terminals HV+, HV- are output terminals.

[0035] In this case, the first battery 40 is a high-voltage battery (for example, 400 V) connected in parallel to the input / output terminals HV+, HV- of the DC-DC converter 1, the second battery 41 is a low-voltage battery (for example, 12 V) connected in parallel to the input / output terminals LV+, LV- of the DC-DC converter 1, the first load 45 is a high-voltage load (for example, an electric motor of a vehicle with electric or hybrid electric / thermal propulsion) and the second load 46 is a low-voltage load (for example, electrical installations in the passenger compartment of an electric or hybrid vehicle).

[0036] The DC-DC converter 1 comprises a switch 1-1 having the function of electrically connecting or disconnecting the internal components of the DC-DC converter 1 to / from the first terminal HV+ connected to the high-voltage battery 40.

[0037] In particular, the switch 1-1 has the function of electrically connecting / disconnecting the DC-DC converter 1 to / from the high-voltage battery 40 by connecting / disconnecting the internal components of the DC-DC converter 1 to / from the first terminal HV+ depending on the value of the first switch signal S1_sw.

[0038] Furthermore, the DC-DC converter 1 comprises a further switch 1-2 (see Figure 1B ), which has the function of electrically connecting / disconnecting the internal components of the DC-DC converter 1 to / from the low-voltage terminal LV+, which is connected to the low-voltage battery 41.

[0039] In particular, the further switch 1-2 has the function of electrically connecting / disconnecting the DC-DC converter 1 to / from the low-voltage battery 41 by connecting / disconnecting the internal components of the DC-DC converter 1 to / from the second terminal LV+ depending on the value of the further switch signal S2_sw.

[0040] The current sensor 3 is connected to the DC-DC converter 1 and to the protection circuit 2 and has the function of detecting the current that flows into and / or out of the DC-DC converter 1, in particular the current I_HV+ that flows into and / or out of the first terminal HV+.

[0041] In particular, the current sensor 3 comprises an input terminal, which is electrically connected to the DC-DC converter 1 and is adapted to receive a current detection signal I_HV_dt_in, which depends on the current I_HV+ when the first terminal HV+ is input.

[0042] The current sensor 3 also comprises an output terminal, which is electrically connected to the protection circuit 2 and is adapted to generate a current measurement signal S1_ms (voltage or current type), which represents the measured value of the current I_HV+ that flows into the first terminal HV+ of the DC-DC converter 1.

[0043] The current sensor 3 is implemented, for example, with an operational amplifier circuit.

[0044] It is noted that the current sensor 3 is shown outside the DC-DC converter 1, but it can also be integrated therein.

[0045] The protection circuit 2 has the function of detecting a sudden variation over time of the current I_HV+ flowing into and / or out of the first terminal HV+ of the DC-DC converter 1, in order to detect the presence of a sudden variation of the input and / or output current I_HV+ and to disconnect the DC-DC converter 1 from the side where the current sudden variation has been detected, thus avoiding damaging the DC-DC converter 1. Note that the DC-DC converter 1 can remain disconnected from the side where the current sudden variation has been detected for a certain period of time and then be automatically connected again to the same side; in this case, the time interval during which the DC-DC converter 1 remains disconnected is used to identify and solve the cause of the current sudden variation, however it cannot be guaranteed that the fault has actually been solved.

[0046] Alternatively, the DC-DC converter 1 remains disconnected until the cause of the current sudden variation at the input or at the output of the DC-DC converter 1 is actually solved.

[0047] The term "sudden variation" of the input current I_HV+ or I_LV+ over time means that its trend at a given instant has a high slope (i.e. an excessively rapid variation of the input current), such as a rising or falling edge of the input current I_HV+ or I_LV+.

[0048] For example, this can happen in the following cases:

[0049] - simultaneous switching on of a plurality of electrical / electronic devices;

[0050] - activation of the low-voltage battery 41 or of the high-voltage battery 40;

[0051] - malfunction of the low-voltage battery 41 or of the high-voltage battery 40;

[0052] - malfunction in an electrical component powered by the low-voltage battery 41.

[0053] With reference to Figure 2 the protection circuit 2 is shown in greater detail.

[0054] The protection circuit 2 comprises an input terminal I1_IN adapted to receive a current measurement signal S1_ms (from the current sensor 3) representative of the measured value of the current I_HV+ at the input of the first voltage terminal HV+ of the DC-DC converter 1.

[0055] The protection circuit 2 further comprises a differentiator 2-1 configured to measure the slope of the current I_HV+ flowing into the first terminal HV+ of the DC-DC converter 1 at the input and configured to detect whether the value of the measured slope is greater than or less than a threshold value; in particular, said measurement of the input current I_HV+ slope is implemented by means of a differentiation operation on the current measurement signal S1_ms generated by the current sensor 3.

[0056] Finally, the protection circuit 2 comprises an output terminal 11 0 adapted to generate a disconnection signal S1 dsn having a first value (e.g. a high logic value) representative of the electrically disconnected condition of the power supply circuit 1 from the battery 40 and a second value (e.g. a low logic value) representative of the electrically connected condition of the power supply circuit 1 to the battery 40.

[0057] In particular, the disconnection signal S1 dsn is received at a control terminal of a switch 1-1 inside the DC-DC converter 1 which alternately connects the DC-DC converter 1 to the high-voltage battery 40 or disconnects the DC-DC converter 1 from the high-voltage battery 40 by means of a first terminal HV+.

[0058] Therefore, when a too fast variation of the slope of the current I HV+ inputted into the first terminal HV+ of the DC-DC converter 1 is detected (by means of the sensor 3 and the protection circuit 2), the DC-DC converter 1 is electrically disconnected from the first battery 40 by disconnecting the internal components of the DC-DC converter 1 from the first terminal HV+ to avoid damaging the DC-DC converter 1; on the contrary, when a not fast (i.e. gradual) variation of the slope of the current I HV+ inputted into the first terminal HV+ of the DC-DC converter 1 is detected (by means of the sensor 3 and the protection circuit 2), the electrical connection of the DC-DC converter 1 to the first battery 40 is maintained by means of the connection of the internal components of the DC-DC converter 1 to the first terminal HV+.

[0059] Advantageously, the differentiator 2-1 is an RC circuit, i.e. it comprises a capacitor 2-2 connected in series to a resistor 2-3.

[0060] In particular, the capacitor 2-2 has a first terminal connected to the input terminal 11 IN of the protection circuit 2 (and therefore the first terminal of the capacitor 2-2 is connected to the output terminal of the current sensor 3), and the resistor 2-3 has a first terminal connected to a second terminal of the capacitor 2-2.

[0061] For example, the capacitor 2-2 has a capacitance C14 = 15 nF [nF = nanofarad] and the resistor 2-3 has a resistance R34 = 47 kΩ [kΩ = kilo-ohm].

[0062] Advantageously, the protection circuit 2 further comprises a voltage divider having a moving center voltage function allowing to detect sudden variations in both directions of the power supply circuit 1, i.e. sudden variations of the current inputted into and outcoming from the first terminal HV+ and sudden variations of the current inputted into and outcoming from the second terminal LV+.

[0063] The voltage divider includes a resistor 2-4 connected between the second terminal of resistor 2-3 and a first reference voltage VCC_33 (e.g., equal to 3.3V), and a resistor 2-5 connected between the second terminal of resistor 2-3 and a low reference voltage GND (e.g., the low reference voltage GND is a ground reference voltage) that is lower than the first reference voltage VCC_33.

[0064] When the voltage divider is powered by a first reference voltage VCC_33 equal to 3.3 volts, the voltage divider is configured to generate a voltage drop of, for example, equal to 1.65 volts at the second terminal of resistors 2-3.

[0065] For example, the resistance of resistor 2-4 is R664 = 2.2kΩ, and the resistance of resistor 2-5 is R665 = 2.2kΩ.

[0066] Preferably, the protection circuit 2 further includes a capacitor 2-6 connected between the common node N1 of the capacitor 2-2 and the resistor 2-3 and the ground reference voltage.

[0067] For example, the capacitance of capacitor 2-6 is C110 = 220pF [pF = picofarad].

[0068] Protection circuit 2 also includes a drive stage placed between the common node N1 of capacitor 2-2 and resistor 2-3 and the output terminal I1_O of protection circuit 2.

[0069] The driver stage has the following functions: detecting the presence of sudden changes in the current of the input DC-DC converter 1 in two directions, namely, when the DC-DC converter 1 is operating in buck mode, the current I_HV+ input to the first terminal HV+ and the current I_LV+ flowing out of the first terminal HV+ suddenly changes, and when the DC-DC converter 1 is operating in boost mode, the current I_LV+ input to the second terminal LV+ and the current I_LV+ flowing out of the second terminal LV+ suddenly changes.

[0070] Driver level includes, for example Figure 2 The following components are connected together: first comparator 2-10, second comparator 2-11, resistor 2-12, resistor 2-18, resistor 2-22, capacitor 2-21, resistor 2-26, capacitor 2-25, resistor 2-20, resistor 2-24, resistor 2-23, resistor 2-32, MOSFET transistor 2-30, resistor 2-31, and Zener diode 2-35.

[0071] The set of first comparator 2-10, second comparator 2-11 and resistor 2-12 has the function of determining the voltage value at node N5, which is the common output of first comparator 2-10 and second comparator 2-11.

[0072] In particular, the first comparator 2-10 is powered by a first supply voltage VCC_33, comprises two input terminals (positive terminal and negative terminal) and one output terminal and it works as a voltage comparator, i.e. it generates a high logic value at the output terminal when the voltage value of the positive input terminal is greater than the voltage value of the negative input terminal, while it generates a low logic value at the output terminal when the voltage value of the positive input terminal is less than the voltage value of the negative input terminal.

[0073] The second comparator 2-11 has a similar operation to the first comparator 2-10, i.e. it generates a high logic value at the output terminal when the voltage value of the positive input terminal is greater than the voltage value of the negative input terminal, while it generates a low logic value at the output terminal when the voltage value of the positive input terminal is less than the voltage value of the negative input terminal.

[0074] The comparators 2-10, 2-11 are implemented with respective integrated circuits, for example with the integrated circuits sold by Texas Instruments having the identification LM339, LM239, LM139, LM2901.

[0075] The driving stage further comprises:

[0076] - a first parallel connection of a capacitor 2-21 and a resistor 2-22;

[0077] - a second parallel connection of a capacitor 2-25 and a resistor 2-26;

[0078] - a resistor 2-20 connected between the first parallel connection and a reference voltage Vref;

[0079] - a resistor 2-24 connected between the reference voltage Vref and the second parallel connection;

[0080] - a series connection of a resistor 2-23 and a switch 2-30, the switch 2-30 comprising a control terminal connected to the node N4 and adapted to control the opening and closing of the switch 2-30;

[0081] - a resistor 2-31 connected between the control terminal of the switch 2-30 and the common node N4.

[0082] The set of capacitor 2-21, resistor 2-22, capacitor 2-25, resistor 2-26, resistor 2-20, resistor 2-24, resistor 2-23, resistor 2-32, MOSFET transistor 2-30, resistor 2-31 and Zener diode 2-35 has the following function: determining the threshold of the level of intervention and hysteresis of the protection against sudden variations of current at the input / output of the power supply circuit 1, which avoids oscillations between activation and deactivation of the protection circuit 2, thus reducing the possibility of oscillations between disconnection of the power supply circuit and connection of the power supply circuit.

[0083] The positive terminal of the second comparator 2-11 is connected to the negative terminal of the first comparator 2-10 and it is also connected to the common node N1 of the capacitor 2-2 and the first resistor 2-3.

[0084] The positive terminal of the first comparator 2-10 is connected to the node N3, which is the common node of the first terminal of the capacitor 2-25, the first terminal of the resistor 2-26, the first terminal of the resistor 2-24 and the first terminal of the resistor 2-32.

[0085] The negative terminal of the second comparator 2-11 is connected to the node N2, which is the common node of the first terminal of the capacitor 2-21, the first terminal of the resistor 2-22, the first terminal of the resistor 2-20 and the first terminal of the resistor 2-23.

[0086] The resistor 2-12 is connected between the output terminal of the first comparator 2-10 and the first supply voltage VCC_33.

[0087] The series connection (of the resistor 2-23 and the switch 2-30) is connected in parallel with the first parallel connection (of the capacitor 2-21 and the resistor 2-22), i.e.:

[0088] The resistor 2-23 comprises a first terminal connected to the node N2, which is the common node of the first terminal of the capacitor 2-21, the first terminal of the resistor 2-22 and the first terminal of the resistor 2-20;

[0089] The resistor 2-23 comprises a second terminal connected to the first terminal of the switch 2-30;

[0090] The switch 2-30 comprises a second terminal connected to the second terminal of the capacitor 2-21 and to the second terminal of the resistor 2-22, i.e. to the ground reference voltage.

[0091] Reference Figure 1B which shows a block diagram of a power supply system 150 based on the second embodiment of the present application.

[0092] Figure 1B The second embodiment differs from the first embodiment of the application in that it comprises a further protection circuit 102, a further current sensor 103 and a further switch 1-2 in the DC-DC converter 101 in order to further detect the current I_LV+ flowing into the second terminal LV+ at input and / or out of the second terminal LV+ at output. Figure 1A

[0093] Note that, for simplicity, Figure 1B two different protection circuits 2, 102 are shown, but the application can also be implemented using a single protection circuit which performs the protection functions of both circuits 2 and 102.

[0094] Thus, Figure 1B The current sensor 103 of the second embodiment has a function similar to that of the current sensor 3 of the first embodiment of the application, except that the current sensor 103 has the function of detecting the current I_LV+ flowing into the second terminal LV+ at input and / or out of the second terminal LV+ at output, generating a further current measurement signal S2_ms (voltage or current type) representative of a measured value of the current I_LV+ flowing into the second terminal LV+ at input. Figure 1A

[0095] Furthermore, Figure 1B The protection circuit 102 of the second embodiment has a function similar to that of the protection circuit 2 of the first embodiment of the application, except that the protection circuit 102 has the function of detecting sudden changes in the current I_LV+ flowing into the second terminal LV+ at input and / or out of the second terminal LV+ at output over time. Figure 1A Finally, the switch 1-2 has the function of electrically connecting / disconnecting the internal components of the DC-DC converter 1 to / from the second terminal LV+ connected to the low-voltage battery 41.

[0096] Thus, the aforementioned considerations relating to the first terminal HV+ can be similarly made for the second terminal LV+, i.e. the input terminal I2_IN of the protection circuit 102 is adapted to receive a further current measurement signal S2_ms representative of a measured value of the current I_LV+ at input to the second terminal LV+ of the DC-DC converter 1.

[0097] In this second embodiment, the differentiator 2-1 of the protection circuit 102 is configured to measure the slope of the current I_LV+ at input to the second terminal LV+ of the DC-DC converter 1 and it is configured to detect whether the measured slope value is greater than or less than a further threshold value.

[0098]

[0099] ​​​Finally, the protection circuit 102 comprises an output terminal I2_0 adapted to generate a further disconnect signal S2_dsn having a first value (e.g. a high logic value) representative of the electrical disconnection of the power supply circuit 1 from the battery 41 and a second value (e.g. a low logic value) representative of the electrical connection of the power supply circuit 1 to the battery 41.

[0100] Therefore, when a too fast variation of the slope of the current I_LV+ at the input of the terminal LV+ of the DC-DC converter 1 is detected in the second embodiment (by means of the sensor 103 and the protection circuit 102), the DC-DC converter 1 is electrically disconnected from the second battery 41 by disconnecting the internal components of the DC-DC converter 1 from the input terminal LV+ to avoid damaging the DC-DC converter 1; on the contrary, when a non-fast (i.e. gradual) variation of the slope of the current I_LV+ at the input of the terminal LV+ of the DC-DC converter 1 is detected in the second embodiment (by means of the sensor 103 and the protection circuit 102), the electrical connection of the DC-DC converter 1 to the second battery 41 is maintained by means of the connection of the internal components of the DC-DC converter 1 to the input terminal LV+.

[0101] Below are possible values of the resistances and capacitances of the components of the drive stage of the protection circuit 2 of the first embodiment:

[0102] - resistor 2-12: resistance R663 = 1.0 kQ;

[0103] - resistor 2-20: resistance R654 = 2.0 kQ;

[0104] - capacitor 2-21 : capacity C108 = 1.0 nF;

[0105] - resistor 2-22: resistance R656 = 13 kQ;

[0106] - resistor 2-24: resistance R639 = 6.8 kQ;

[0107] - capacitor 2-25: capacity C107 = 1.0 nF;

[0108] - resistor 2-26: resistance R640 = 15 kQ;

[0109] - resistor 2-31 : resistance R657 = 10 kQ;

[0110] - resistor 2-32: resistance R658 = 20 kQ;

[0111] - resistor 2-23: resistance R656 = 13 kQ;

[0112] Preferably, the protection circuit 2 further comprises an enable stage 2-50 having the function of enabling or disabling the operation of the protection circuit 2 as a function of the value of an enable signal S_en generated by an external control unit, for example a microprocessor.

[0113] The enable stage 2-50 is interposed between the drive stage of the protection circuit 2 and the output terminal I1_O of the protection circuit 2.

[0114] The enable stage 2-50 comprises a switch 2-14, a resistor 2-13, a resistor 2-15, a switch 2-40, a resistor 2-16 and a resistor 2-17.

[0115] The switch 2-14 is interposed between the terminal of the common output of the first comparator 2-10 and of the second comparator 2-11 and the output terminal I1_O of the protection circuit 2; moreover, the switch 2-14 comprises a control terminal adapted to control the opening and the closing of the switch 2-14.

[0116] The control terminal is connected to the common terminal of the resistors 2-13 and 2-15.

[0117] The switch 2-14 is implemented, for example, with a MOSFET transistor.

[0118] The resistor 2-13 is connected between the terminal of the common output of the first comparator 2-10 and of the second comparator 2-11 and the control terminal of the switch 2-14.

[0119] The resistor 2-15 is connected between the control terminal of the switch 2-14 and the switch 2-40.

[0120] The switch 2-40 is connected between the resistor 2-15 and the resistors 2-16, 2-17.

[0121] The resistor 2-16 is connected between the switch 2-40 and the first reference voltage VCC_33.

[0122] The resistor 2-17 is connected between the switch 2-40 and the low reference voltage GND.

[0123] The switch 2-40 comprises a first terminal, a second terminal and a third terminal and comprises a control terminal adapted to receive the enable signal S_en so as to alternatively connect the first terminal to the second terminal or to the third terminal.

[0124] The switch 2-40 is used to switch between the following two possible positions as a function of the value of the enable signal S_en:

[0125] - resistor 2-15 connected to a first position of resistor 2-16: in this position, the operation of protection circuit 2 is enabled, i.e. enable stage 2-50 detects sudden variations of currents I_HV+, I_LV+ at the input of DC-DC converter 1 in order to disconnect DC-DC converter 1 from high voltage battery 40 and low voltage battery 41, respectively, as shown above;

[0126] - resistor 2-15 connected to a second position of resistor 2-17: in this position, the operation of protection circuit 2 is disabled, i.e. enable stage 2-50 does not detect sudden variations of currents I_HV+, I_LV+ at the input of DC-DC converter 1.

[0127] Resistor 2-16 is connected between the second terminal of switch 2-40 and first supply voltage VCC_33.

[0128] Resistor 2-17 is connected between the third terminal of switch 2-40 and low reference voltage GND.

[0129] Below are possible values of resistances and capacitances of the components of the enable stage of protection circuit 2:

[0130] - resistor 2-15: resistance R659 = 1.0 kQ;

[0131] - resistor 2-16: resistance R661 = 100 kQ;

[0132] - resistor 2-17: resistance R660 = 100 kQ;

[0133] - resistor 2-13: resistance R662 = 100 kQ;

[0134] Preferably, the protection circuit further comprises resistor 2-18 connected between the output terminal of the protection circuit and a second supply voltage VCC_5 greater than first supply voltage VCC_33 (for example, VCC_5 = 5 volts and VCC_33 = 3.3 volts).

[0135] Resistor 2-18 has, for example, resistance R638 = 1.0 kQ.

[0136] Reference Figure 3 which schematically shows the trend of current I_HV+ at the input of DC-DC converter 1 over time in the event of a sudden variation of input current I_HV+, the trend of current measurement signal S1_ms generated from the output of current sensor 3 over time, the trend of disconnection signal S1_dsn generated from the output of protection circuit 2 over time.

[0137] It is assumed that the DC-DC converter 1 is automatically reconnected after a defined time interval AT after the moment in which the sudden variation of the input current of the first input terminal HV+ of the DC-DC converter 1 is detected; the defined time interval AT is calculated, for example, by means of a time counter internal to the protection circuit 2.

[0138] The following behavior can be observed.

[0139] At the moment comprised between t0 and tl, the input current I_HV+ has a gradual increasing trend from the value I1 to the value I2, therefore the disconnection signal S1_dsn has a low logic value V_L (for example, equal to 0 volts) which keeps the DC-DC converter 1 connected to the high-voltage battery 40 by means of the first input terminal HV+.

[0140] Furthermore, at the moment comprised between t0 and tl, the voltage V_N1 of the node N1 has a small minimum value Vmin.

[0141] It should be noted that the difference between the values I2 and I0 of the input current I_HV+ can also be high, but the disconnection signal S1_dsn remains at the low logic value V_L because the trend of the input current I_HV+ does not have a sudden variation, but has a gradual increasing trend over time.

[0142] On the contrary, at the moment comprised between tl and t2 (t2 being subsequent to tl), the input current I_HV+ has a sudden variation from the value I2 at the moment tl to the value I3 at the moment t2, in which I3 is much greater than I2, and the time interval comprised between tl and t2 is small: the cause of said sudden variation of the input current I_HV+ is, for example, a malfunction of the high-voltage battery 40.

[0143] In this case, at the moment t2, the voltage V_N1 of the node N1 has a positive peak value at the moment comprised between tl and t2, the maximum value Vmax being greater than the minimum value Vmin.

[0144] The disconnection signal S1_dsn has a transition (between the moments tl and t2) from the low logic value V_L to the high logic value V_H (for example, equal to 5 V) which disconnects the DC-DC converter 1 from the battery 40 by disconnecting the internal components of the DC-DC converter 1 from the first input terminal HV+, thus avoiding damaging the DC-DC converter 1.

[0145] At the moment comprised between t2 and t4, the input current I_HV+ has a substantially constant trend, therefore the malfunction of the battery 40 is prevented from spreading on the high-voltage side of the DC-DC converter 1.

[0146] Furthermore, at the instants comprised between t2 and t4, the disconnection signal S1_dsn maintains the high logic value which keeps the DC-DC converter 1 disconnected from the battery 40.

[0147] At the instant t4, the input current I_HV+ starts having a decreasing trend which continues until the instant t5 at which the input current I_HV+ reaches a value I5 lower than the value I3 of the instant t2 at which the input current sudden variation occurred.

[0148] At the instant t5, the protection circuit 2 detects that the input current I_HV+ has returned to a trend without sudden variations within the defined time interval AT (comprised between t2 and t5), during which it is possible to identify and possibly solve the cause of the input current sudden variation.

[0149] Therefore, after the defined time interval AT has elapsed, the DC-DC converter 1 is automatically reconnected to the high-voltage battery 40, here assuming that the high-voltage battery 40 is no longer affected by the fault.

[0150] The protection circuit 2 generates the disconnection signal S1_dsn which has a transition from the high logic value V_H to the low logic value V_L (between the instants t5 and t6) which restores the electrical connection between the DC-DC converter 1 and the battery 40 by means of the first input terminal HV+.

[0151] At the instants comprised between t6 and t7, the input current I_HV+ has a substantially constant trend, therefore the disconnection signal S1_dsn maintains the low logic value which maintains the electrical connection between the DC-DC converter 1 and the battery 40 by means of the first input terminal HV+.

Claims

1. A power supply system (50), comprising: - a power supply circuit (1) having a terminal (HV+) having a voltage level (AHV); - a current sensor (3) adapted to generate a current measurement signal (S1 ms) representative of a measured value of a current (I HV+) flowing through a terminal of the power supply circuit; - a protection circuit (2) comprising: - an input terminal (11 IN) adapted to receive the current measurement signal (S1 ms) representative of a measured value of a current flowing through the terminal of the power supply circuit; - a differentiator (2-1; 2-2, 2-3) adapted to measure a slope of the current measurement signal; - a drive stage (2-10, 2-12, 2-11, 2-20, 2-21, 2-22, 2-23, 2-30, 2-24, 2-25, 2-26, 2-31, 2-32, 2-35) interposed between the differentiator and an output terminal of the protection circuit, the drive stage being adapted to generate a disconnect signal (S1 dsn) carrying: - a first value representative of an electrical connection of internal components of the power supply circuit to the terminal (HV+) of the power supply circuit in case the measured value of the slope of the current signal flowing through the terminal of the power supply circuit is less than or equal to a threshold value; or - a second value representative of a disconnection of internal components of the power supply circuit from the terminal (HV+) of the power supply circuit in case the measured value of the slope of the current signal flowing through the terminal of the power supply circuit is greater than the threshold value; - an output terminal (11 0) adapted to generate the disconnect signal (S1 dsn); - an enable stage (2-50) interposed between the drive stage and the output terminal (11 0) of the protection circuit; wherein the power supply circuit (1) is configured to receive the disconnect signal (S1 dsn) and, alternatively, to electrically connect or to disconnect the internal components of the power supply circuit to / from the terminal of the power supply circuit as a function of the value of the disconnect signal (S1 dsn); wherein the differentiator comprises a series connection of a first capacitor (2-2) and a first resistor (2-3), wherein: - the input terminal (11 IN) of the protection circuit is connected to a first terminal of the first capacitor (2-2); - an input terminal of the drive stage is connected to a node (N1) common to the first capacitor (2-2) and the first resistor (2-3); the drive stage further comprising: - a second capacitor (2-20) and a second resistor (2-21) connected in series, wherein: - a first terminal of the second capacitor (2-20) is connected to the node (N1) common to the first capacitor (2-2) and the first resistor (2-3); - a second terminal of the second capacitor (2-20) is connected to a first terminal of the second resistor (2-21); - a second terminal of the second resistor (2-21) is connected to a second terminal of the first capacitor (2-2); and - a node (N2) common to the second capacitor (2-20) and the second resistor (2-21) is connected to an input terminal of the drive stage. - a first comparator (2-10) and a second comparator (2-11), comprising a respective positive input terminal, a respective negative input terminal and a respective output terminal, adapted to generate a respective comparison signal between the signal values of the positive input terminal and of the negative input terminal, powered by a first supply voltage (VCC_33); - a second resistor (2-12); - a third resistor (2-18), connected between an output terminal (II_O) of the protection circuit and a second supply voltage (VCC_5) greater than the first supply voltage; the power supply system further comprising a fourth resistor (2-15); wherein: - the negative input terminal of the first comparator (2-10) is connected to the positive input terminal of the second comparator and to a node (N1) common to the first capacitor (2-2) and to the first resistor (2-3); - the positive input terminal of the first comparator (2-10) is biased to a reference voltage (Vref); - the negative input terminal of the second comparator (2-11) is biased to a reference voltage (Vref); - the output terminal of the first comparator (2-10) is connected to the output terminal of the second comparator; - the output terminal (II_O) of the protection circuit is associated with a node (N5) common to the output terminals of the first comparator and of the second comparator; - the second resistor (2-12) is connected between the node (N5) common to the output terminals of the first comparator and of the second comparator and the first supply voltage (VCC_33); and wherein: - the protection circuit further comprises a first switch (2-14) connected between the node (N5) common to the output terminals of the first comparator and of the second comparator and the output terminal (II_O) of the protection circuit, the first switch (2-14) comprising a control terminal for controlling the opening and the closing of the first switch (2-14); - the fourth resistor (2-15) is placed between the control terminal of the first switch (2-14) and the first supply voltage (VCC_33) and the enable stage is configured to enable or disable the operation of the first switch (2-14) as a function of the value of an enable signal (S_en).

2. The power supply system according to claim 1, wherein: - the first capacitor (2-2) has a first terminal connected to an input terminal (II_IN) of the protection circuit; - the first resistor (2-3) has a first terminal connected to a second terminal of the first capacitor; the protection circuit further comprises a voltage divider (2-4, 2-5) configured to generate a divided voltage on the second terminal of the first resistor (2-3); - the second terminal of the first resistor (2-3) is connected to a node (N1) common to the first capacitor (2-2) and to the negative input terminal of the first comparator (2-10) and to the positive input terminal of the second comparator (2-11). and wherein said drive stage is placed between a node (N1) common to a second terminal of said first capacitor and a first terminal of said first resistor and an output terminal (11_0) of said protection circuit.

3. The power supply system of claim 2, wherein, said voltage divider comprises: - a fifth resistor (2-4) connected between a second terminal of said first resistor (2-3) and a first supply voltage (VCC_33); - a sixth resistor (2-5) connected between a second terminal of said first resistor (2-3) and a low reference voltage (GND) lower than said first supply voltage.

4. The power supply system according to claim 2 or 3, wherein said power supply circuit (1) comprises a second switch (1-1) configured to electrically connect or to electrically disconnect internal components of said power supply circuit to / from an input terminal (HV+) of said power supply circuit, said second switch (1-1) comprises a control terminal (S1_sw) adapted to receive a disconnection signal (S1_dsn) generated by said protection circuit, wherein said second switch (1-1) is configured to: - electrically connect said internal components of said power supply circuit to said input terminal (HV+) of said power supply circuit in case said disconnection signal (S1_dsn) carries a first value representative of an electrical connection; - electrically disconnect said internal components of said power supply circuit from said input terminal (HV+) of said power supply circuit in case said disconnection signal (S1_dsn) carries a second value representative of an electrical disconnection.

5. The power supply system according to claim 4, further comprising: - a first parallel connection of a second capacitor (2-21) and a seventh resistor (2-22); - a second parallel connection of a third capacitor (2-25) and an eighth resistor (2-26); - a ninth resistor (2-20) connected between a first terminal of said seventh resistor (2-22) and a reference voltage (Vref); - a tenth resistor (2-24) connected between said reference voltage (Vref) and a first terminal of said eighth resistor (2-26); - an eleventh resistor (2-31) placed between a control terminal of a third switch (2-30) for controlling its opening and closing and a source of said first switch (2-14); - a twelfth resistor (2-32) having a first terminal connected to said first terminal of said eighth resistor (2-26) and a second terminal connected to a source of said first switch (2-14) via a Zener diode (2-35); - a thirteenth resistor (2-23) in series connection with said third switch (2-30); wherein: - a first terminal of said thirteenth resistor (2-23) is connected to a drain of said third switch (2-30) and a second terminal of said thirteenth resistor (2-23) is connected to said first terminal of said seventh resistor (2-22); - the source of the third switch (2-30) is connected to the second terminal of the seventh resistor (2-22).

6. The power supply system of claim 5, wherein, The enable stage comprises: - a fourteenth resistor (2-13) connected between a node (N5) common to the output terminals of the first and second comparators and a control terminal of the first switch (2-14); - a fourth switch (2-40) comprising a first terminal, a second terminal and a third terminal and comprising a control terminal adapted to receive the enable signal (S_en) so as to alternatively connect the first terminal to the second terminal or to the third terminal according to the value of the enable signal; - the fourth resistor (2-15) is connected between the control terminal of the first switch (2-14) and the first terminal of the fourth switch (2-40); - a fifteenth resistor (2-16) connected between the second terminal of the fourth switch (2-40) and the first supply voltage (VCC_33); - a sixteenth resistor (2-17) connected between the third terminal of the fourth switch (2-40) and a low reference voltage (GND); The system further comprises a control unit configured to generate the enable signal (S_en) so as to enable or disable the operation of the protection circuit.

7. The power supply system of claim 1, wherein, The power supply circuit is a bidirectional type DC-DC voltage converter configured to convert the voltage level of high voltage direct current type (AHV) into a low voltage direct current level (ALV) and vice versa, The converter comprises a first pair of input / output terminals (HV+, HV-) adapted to receive / generate a high voltage direct current level and a second pair of input / output terminals (LV+, LV-) adapted to receive / generate a low voltage direct current level, The system further comprises: - a high voltage battery (40) connected in parallel to the first pair of input / output terminals; - a high voltage electrical load (45) connected in parallel with the high voltage battery (40); - a low voltage battery (41) connected in parallel to the second pair of input / output terminals; - a low voltage electrical load (46) connected in parallel with the low voltage battery (41).

8. An electric vehicle or a hybrid vehicle with an electric motor and an internal combustion engine, comprising a power supply system according to any one of claims 1-7.

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