DESCRIPTION

Technical field of the invention

The present invention relates in general to the electronics field.

More in particular, the present invention concerns a power supply system equipped with an electronic circuit for the protection of a power supply circuit of the same system, in case of a sudden variation in the current at the input of the same power supply circuit.

Prior art

In the automotive field, direct-direct voltage converters (DC-DC) are used (in hybrid or electric vehicles) connected on one side to a high voltage battery (e.g., 400 V) to power the electric motor of the vehicle and on the other side to a low voltage battery (e.g., 12 V) to power the electrical services in the passenger compartment of the same vehicle.

Therefore the DC-DC converter operates bidirectionally so as to supply both the low voltage side and the high voltage side.

DC-DC converter protection circuits are known, in case of input overcurrents to the DC-DC converter, i.e. peak current values which are too high.

Situations may also occur in which there is a sudden variation in the current at the input of the DC-DC converter, for example on the low voltage side in case several electrical/electronic devices are switched on at the same time, or in case of a battery fault on the low or high voltage side, or in case of a fault in an electrical component of the vehicle: in this case it is necessary to protect the DC-DC converter from this sudden variation in its input current, in order to prevent damage to the DC-DC converter itself.

The Applicant has observed that the known overcurrent protection circuits do not allow to detect the situation in which there is a sudden variation in the current at the input of the DC-DC converter with sufficient reliability and speed, thus increasing the risk of damaging it.

Brief summary of the invention

The present invention relates to a power supply system with protection against sudden variations in the input current as defined in enclosed claim 1 and from its preferred embodiments described in the dependent claims from 2 to 9. The basic idea is to use a protection circuit with a differentiator capable of detecting a sudden variation in the current at the input of the power supply circuit, then promptly disconnecting the power supply circuit from the side where the sudden current variation occurred.

The Applicant has perceived that the power supply system according to the present invention allows a sudden variation of the current at the input of a power supply circuit to be detected in a reduced amount of time and reliably, regardless of the absolute value of the input current.

It is also an object of the present invention a vehicle with an electric motor or a hybrid vehicle with a thermal/electric motor, as defined in the enclosed claim 10.

Brief description of the drawings

Additional features and advantages of the invention will become more apparent from the description which follows of a preferred embodiment and its variants, provided by way of example with reference to the appended drawings, in which:

Figure 1 A shows a block diagram of a power supply system according to a first embodiment of the invention;

Figure 1 B shows a block diagram of a power supply system according to a second embodiment of the invention;

Figure 2 shows an electronic protection circuit included in the power supply system of Figure 1 A and 1 B;

Figure 3 schematically shows a possible trend of some signals used in the power supply system of Figure 1 A and in the electronic protection circuit of Figure 2.

Detailed description of the invention

It should be observed that in the following description, identical or analogous blocks, components or modules are indicated in the figures with the same numerical references, even where they are illustrated in different embodiments of the invention.

With reference to Figure 1 A, it shows a block diagram of a power supply system 50 according to a first embodiment of the invention.

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.

The power supply circuit 1 comprises a first pair of terminals FIV+, FIV- and a second pair of terminals LV+, LV-. The first battery 40 is connected in parallel to the first pair of terminals HV+, HV-.

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

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

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

The power supply circuit 1 is for example a direct-direct voltage converter (DC- DC) or (with the appropriate circuit changes) an alternate-direct voltage converter (AC- DC) or direct-alternate voltage converter (DC-AC).

For the purpose of explaining the invention, the power supply circuit 1 is subsequently considered to be a DC-DC voltage converter, but the following considerations can be made similarly for other types of power supply circuits.

The DC-DC converter 1 converts voltage between two levels of different direct current voltage, indicated with first level of direct voltage AHV (also referred to as“high voltage”) and with second level of direct voltage ALV (also referred to as“low voltage”).

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

a conversion from the level of high direct voltage AHV to the low direct voltage level ALV (indicated with“buck" mode), then the first pair of terminals HV+, HV- are input terminals and the second pair of terminals LV+, LV- are output terminals;

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

In this case the first battery 40 is a high voltage battery (e.g., 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 (e.g., 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 (e.g., an electric motor of a vehicle with electric or hybrid electric/thermal propulsion) and the second load 46 is a low voltage load (e.g., the electrical utilities in the electric or hybrid vehicle passenger compartment).

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.

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, as a function of the value of a first switching signal S1_sw, by connecting/disconnecting the internal components of the DC-DC converter 1 to/from the first terminal HV+.

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

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 40, as a function of the value of a further switching signal S2_sw, by connecting/disconnecting the internal components of the DC-DC converter 1 to/from the second terminal LV+.

The current sensor 3 is connected to the DC-DC converter 1 and to the protection circuit 2 and it has the function of detecting the current flowing in input and/or in output to/from the DC-DC converter 1 , in particular the current l_FIV+ flowing in input and/or in output to/from the first terminal FIV+.

In particular, the current sensor 3 comprises an input terminal electrically connected to the DC-DC converter 1 and adapted to receive a current detection signal l_FIV_dtJn which depends on the current l_FIV+ at the input of the first terminal FIV+.

The current sensor 3 further comprises an output terminal electrically connected to the protection circuit 2 and adapted to generate a current measurement signal S1_ms (voltage or current type) representative of the measurement of the current IJHV+ flowing in input to the first terminal FIV+ of the DC-DC converter 1.

The current sensor 3 is implemented for example with an operating amplifier circuit.

Note that the current sensor 3 is shown externally to the DC-DC converter 1 , but the current sensor 3 may also be integrated therein.

The protection circuit 2 has the function of detecting a sudden variation over time of the current l_FIV+ flowing in input and/or in output to/from the first terminal FIV+ of the DC-DC converter 1 , so as to detect the presence of a sudden variation in the input and/or output current l_FIV+ and disconnect the DC-DC converter 1 from the side where the sudden variation in current has been detected, so as to avoid damaging the DC-DC converter 1. Note that the DC-DC converter 1 can remain disconnected from the side where the sudden variation in current has been detected for a certain period of time and is then 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 resolve the cause of the sudden variation in current, without however any guarantee that the fault has actually been resolved.

Alternatively, the DC-DC converter 1 remains disconnected until the cause of the sudden variation in current at the input or at the ouput of the DC-DC converter 1 has actually been resolved.

The term "sudden variation” over time of the input current l_HV+ or l_LV+ means that its trend at a given moment has a high slope (that is, an overly rapid variation in the input current), such as a rising or falling edge of the input current IJHV+ or l_LV+.

This situation can occur, for example, in the following cases:

several electrical/electronic devices are switched on at the same time;

the low voltage battery 41 or the high voltage battery 40 is activated;

a fault in the low voltage battery 41 or the high voltage battery 40 occurs;

a fault occurs in an electrical component powered by the low voltage battery 41.

With reference to Figure 2, the protection circuit 2 is shown in greater detail.

The protection circuit 2 comprises an input terminal 11 _IN adapted to receive (from the current sensor 3) the current measurement signal S1_ms representative of the measurement of the current l_HV+ at the input of the first voltage terminal HV+ of the DC-DC converter 1.

The protection circuit 2 further comprises a differentiator 2-1 configured to measure the slope of the current l_HV+ flowing in input to the first terminal HV+ of the DC-DC converter 1 and configured to detect if the value of the measured slope is greater than or less than a threshold value; in particular, said measurement of the slope of the input current l_HV+ is carried out by means of a differentiation operation of the current measurement signal S1_ms generated by the current sensor 3.

Lastly, 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 an electrical disconnection of the power supply circuit 1 from the battery 40 and having a second value (e.g., a low logic value) representative of an electrical connection of the power supply circuit 1 to the battery 40.

In particular, the disconnection signal S1_dsn is received at the control terminal of a switch 1 -1 inside the DC-DC converter 1 , which alternatively connects the DC-DC converter 1 to the high voltage battery 40 by means of the first terminal HV+ or disconnects the DC-DC converter 1 from the high voltage battery 40.

Therefore, when an excessively rapid variation in the slope of the current IJHV+ at the input of 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+, in order to avoid damaging the DC-DC converter 1 ; when instead a non-rapid (i.e., gradual) variation in the slope of the current l_HV+ at the input of 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+.

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.

In particular, the capacitor 2-2 has a first terminal connected to the input terminal 11 _IN of the protection circuit 2 (and thus 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.

For example, the capacitor 2-2 has a capacity C14= 15 nF [nf=nanofarad] and the resistor 2-3 has a resistance R34= 47 kQ [kQ= kilo Ohm]

Advantageously, the protection circuit 2 further comprises a voltage divider having the function of shifting the central voltage, so as to allow sudden variations to be detected in both directions of the power supply circuit 1 , i.e., both sudden variations in the current at the input of the first terminal FIV+ and exiting from the first terminal FIV+, and sudden variations in the current at the input of the second terminal LV+ and exiting from the second terminal LV+.

The voltage divider comprises a resistor 2-4 connected between the second terminal of the resistor 2-3 and a first reference voltage VCC_33 (e.g., equal to 3.3 V) and comprises a resistor 2-5 connected between the second terminal of the resistor 2-3 and a low reference voltage GND lower than the first reference voltage VCC33 (e.g., the low reference voltage GND is the ground reference voltage). The voltage divider is configured to generate a divided voltage on the second terminal of the resistor 2-3, equal for example to 1.65 Volts, in case the voltage divider is supplied by the first reference voltage VDC_33 equal to 3.3 Volts.

For example, the resistor 2-4 has a resistance R664= 2.2 kQ and the resistor 2-5 has a resistance R665= 2.2 kQ.

Preferably, the protection circuit 2 further comprises a capacitor 2-6 connected between the node N1 which is common to the capacitor 2-3 and the resistor 2-3 and the ground reference voltage.

For example, the capacitor 2-6 has a capacity C1 10= 220 pF [pf=picofarad].

The protection circuit 2 further comprises a driving stage interposed between the node N1 which is common to the capacitor 2-3 and the resistor 2-3 and the output terminal 11 _0 of the protection circuit 2.

The driving stage has the function of detecting the presence of a sudden variation in the current at the input of the DC-DC converter 1 in both directions, i.e., both a sudden variation from the current l_FIV+ at the input of the first terminal FIV+ and exiting from the first terminal FIV+ when the DC-DC converter 1 operates in buck mode, and a sudden variation from the current l_LV+ at the input of the second terminal LV+ and exiting from the second terminal LV+ when the DC-DC converter 1 operates in boost mode.

The driving stage comprises a first comparator 2-10, a second comparator 2-1 1 , a resistor 2-12, a resistor 2-18, a resistor 2-22, a capacitor 2-21 , a resistor 2-26, a capacitor 2-25, a resistor 2-20, a resistor 2-24, a resistor 2-23, a resistor 2-32, a MOSFET transistor 2-30, a resistor 2-31 and a Zener diode 2-35, which are connected together as shown in Fig.2.

The set of the first comparator 2-10, of the second comparator 2-1 1 and of the resistor 2-12 have the function of determining the voltage value on the node N5 which is in common in output from the first and the second comparators 2-10, 2-1 1.

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

The second comparator 2-1 1 has an operation analogous to that of the first comparator 2-10, i.e., the second comparator 2-1 1 generates at the output terminal a high logic value when the voltage value of the positive input terminal is greater than the voltage value of the negative input terminal, while the second comparator 2-11 generates at the output terminal a low logic value when the voltage value of the positive input terminal is less than the voltage value of the negative input terminal.

The comparators 2-10, 2-1 1 are implemented with respective integrated circuits, such as the integrated circuits identified with LM339, LM239, LM139, LM2901 sold by Texas Instruments.

The driving stage further comprises:

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

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

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

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

a series connection of a resistor 2-23 and of 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;

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

The set of the 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, have the function of determining the levels of intervention of the protection against sudden variations in the current at the input/output of the power supply circuit 1 and the threshold values of the hysteresis which avoids oscillations between the activation and the deactivation of the protection circuit 2, thus reducing the probability of oscillations between the disconnection of the power supply circuit and the connection of the power supply circuit. The positive terminal of the second comparator 2-1 1 is connected to the negative terminal of the first comparator 2-10 and it is also connected to the node N1 which is common to the capacitor 2-2 and to the first resistor 2-3.

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

The negative terminal of the second comparator 2-1 1 is connected to a node N2 which is common to the first terminal of the capacitor 2-21 , to the first terminal of the resistor 2-22, to the first terminal of the resistor 2-20 and to the first terminal of the resistor 2-23.

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

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

the resistor 2-23 comprises a first terminal connected to a node N2 which is common to the first terminal of the capacitor 2-12, to the first terminal of the resistor 2- 22 and to the first terminal of the resistor 2-20;

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

the switch 2-30 comprises a second terminal connected to the second terminal of the capacitor 2-12 and to the second terminal of the resistor 2-22, i.e., to the ground reference voltage.

With reference to Figure 1 B, it shows a block diagram of a power supply system 150 based on a second embodiment of the invention.

The second embodiment of Figure 1 B differs from the first embodiment of Figure 1 A 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 l_LV+ flowing in input and/or in output to/from the second terminal LV+.

Note that for the sake of simplicity, Figure 1 B shows two different protection circuits 2, 102, but the invention can also be made using a single protection circuit which performs both the protection functions of the circuits 2 and 102. Therefore the current sensor 103 of the second embodiment of Figure 1 B has a function analogous to the current sensor 3 of the first embodiment of Figure 1 A, with the difference that the current sensor 103 has the function of detecting the current l_LV+ flowing in input and/or in output to/from the second terminal LV+, thereby generating a further current measurement signal S2_ms (voltage or current type) representative of the measurement of the current l_LV+ flowing in input to the second terminal LV+.

Furthermore, the protection circuit 102 of the second embodiment of Figure 1 B has a function analogous to the protection circuit 2 of the first embodiment of Figure 1 A, with the difference that the protection circuit 102 has the function of detecting a sudden variation over time of the current l_LV+ flowing in input and/or in output to/from the second terminal LV+.

Finally the switch 1 -2 has the function of electrically connecting or disconnecting the internal components of the DC-DC converter 1 to/from the second terminal FIV+ connected to the low voltage battery 41.

Therefore, the foregoing considerations relating to the first terminal FIV+ may also be made analogous to the second terminal LV+, i.e., the input terminal I2JN of the protection circuit 102 is adapted to receive a further current measurement signal S2_ms representative of the measurement of the current l_LV+ at the input of the second terminal LV+ of the DC-DC converter 1.

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

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

Therefore, when in the second embodiment an excessively rapid variation in the slope of the current l_LV+ at the input of the terminal LV+ of the DC-DC converter 1 is detected (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+, in order to avoid damaging the DC-DC converter 1 ; when instead in the second embodiment a non-rapid (i.e., gradual) variation in the slope of the current l_LV+ at the input of the terminal LV+ of the DC-DC converter 1 is detected (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+.

Below are the possible values of the resistances and capacities of the components of the driving stage of the protection circuit 2 of the first embodiment:

resistor 2-12: resistance R663= 1.0 kQ;

resistor 2-20: resistance R654= 2.0 kQ;

capacitor 2-21 : capacity C108= 1.0 nF;

resistor 2-22: resistance R656= 13 kQ;

resistor 2-24: resistance R639= 6.8 kQ;

capacitor 2-25: capacity C107= 1.0 nF;

resistor 2-26: resistance R640= 15 kQ;

resistor 2-31 : resistance R657= 10 kQ;

resistor 2-32: resistance R658= 20 kQ;

resistor 2-23: resistance R656= 13 kQ;

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, which is generated by an external control unit (e.g., a microprocessor),

The enable stage 2-50 is interposed between the driving stage of the protection circuit 2 and the output terminal 11 _0 of the protection circuit 2.

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.

The switch 2-14 is interposed between the terminal which is common to the output of the first and second comparators 2-10, 2-1 1 and the output terminal 11 _0 of the protection circuit 2; in addition, the switch 2-14 comprises a control terminal adapted to control the opening and closing of the switch 2-14.

The control terminal is connected to a terminal which is common to the resistors 2-13 and 2-15.

The switch 2-14 is implemented for example with a MOSFET transistor. The resistor 2-13 is connected between the terminal which is common to the output of the first and second comparators 2-10, 2-11 and the control terminal of the switch 2-14.

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

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

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

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

The switch 2-40 comprises a first, a second and a third terminal and comprises a control terminal adapted to receive the enable signal S_en in order to connect, alternatively, the first terminal to the second or to the third terminal.

The switch 2-40 is such to switch between the following two possible positions, as a function of the value of the enable signal S_en:

a first position in which the resistor 2-15 is connected to the resistor 2-16: in this position the operation of the protection circuit 2 is enabled, i.e., the enable stage 2-50 is such to detect a sudden variation in the current IJHV+, l_LV+ at the input of the DC-DC converter 1 , in order to electrically disconnect the DC-DC converter 1 from the high voltage battery 40 and the low voltage battery 41 , respectively, as illustrated above; a second position in which the resistor 2-15 is connected to the resistor 2-17: in this position the operation of the protection circuit 2 is disabled, i.e., the enable stage 2- 50 is such not to detect a sudden variation in the current IJHV+, l_LV+ at the input of the DC-DC converter 1.

The resistor 2-16 is connected between the second terminal of the switch 2-40 and the first supply voltage VCC_33.

The resistor 2-17 is connected between the third terminal of the switch 2-40 and the low reference voltage GND.

Below are the possible values of the resistances and capacities of the components of the enable stage of the protection circuit 1 :

resistor 2-15: resistance R659= 1.0 kQ;

resistor 2-16: resistance R661 = 100 kQ; resistor 2-17: resistance R660= 100 kQ;

resistor 2-13: resistance R662= 100 kQ;

Preferably, the protection circuit further comprises a resistor 2-18 connected between the output terminal of the protection circuit and a second supply voltage VDC_5 greater than the first supply voltage VDC_33 (e.g., VDC_5= 5 Volts and VDC_33= 3.3 Volts).

The resistor 2-18 has for example a resistance R638=1.0 kQ.

With reference to Figure 3, it shows schematically the trend over time of the current l_HV+ at the input of the DC-DC converter 1 , of the current measurement signal S1_ms generated in output from the current sensor 3, of the disconnection signal S1_dsn generated in output from the protection circuit 2, in case a sudden variation in the input current l_HV+ occurs.

It is assumed that the DC-DC converter 1 is automatically reconnected after a defined time interval DT following the instant of detection of sudden variation in the current at the input of the first input terminal HV+ of the DC-DC converter 1 ; the defined time interval DT is calculated for example by means of a time counter inside the protection circuit 2.

It is possible to observe the following behaviour.

In the instants comprised between tO and t1 the input current l_HV+ has a gradually increasing trend from a value 11 to a value I2, thus the disconnection signal S1_dsn has a low logic value V_L (for example, equal to 0 Volts) that maintains the DC- DC converter 1 connected to the high voltage battery 40 by means of the first input terminal HV+.

In addition, in the instants comprised between tO and the voltage V_N1 of the node N1 has a minimum value Vmin which is small.

It should be noted that the difference between the I2 and I0 values of the input current l_HV+ may also be high, but the disconnection signal S1_dsn maintains the low logic value V_L, as there has been no sudden variation in the trend of the input current l_HV+, which instead has had a gradually increasing trend over time.

Instead in the instants comprised between t1 and t2 (t2 following t1 ) the input current l_HV+ has a sudden variation from the value I2 at the instant t1 to the value I3 at the instant t2, where I3 is much greater than I2 and where the time interval comprised between t1 and t2 is small: the cause of said sudden variation of the input current l_HV+ is for example a fault of the high voltage battery 40.

In this case, at the instant t2 the voltage V_N1 of the node N1 has a positive peak in the instants comprised between t1 and t2, with a maximum value Vmax greater than the minimum value Vmin.

The disconnection signal S1_dsn has a transition (between the instants t1 and t2) from the low logic value V_L to the high logic value V_H (e.g., 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.

In the instants comprised between t2 and t4 the input current IJHV+ has a substantially constant trend, therefore the fault of the battery 40 is prevented from spreading on the high voltage side of the DC-DC converter 1.

In addition, in the instants comprised between t2 and t4, the disconnection signal S1_dsn maintains the high logic value which maintains the DC-DC converter 1 disconnected from the battery 40.

At the instant t4 the input current IJHV+ starts having a gradually decreasing trend, which continues until the instant t5 in which the input current l_HV+ reaches the value I5 lower than the value I3 of the instant t2 in which the sudden variation in input current occurred.

At the instant t5 the protection circuit 2 detects that the input current IJHV+ has returned to have a trend without sudden variations for a defined time interval DT (comprised between t2 and t5), during which it is possible to identify and possibly resolve the cause of the sudden variation of the input current.

Therefore, after the defined time interval DT has elapsed, the DC-DC converter 1 is automatically reconnected to the high voltage battery 40, which is assumed to no longer be affected by the fault.

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

In the instants comprised between t6 and t7 the input current IJHV+ 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+.