FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See section 10, rule 13)
“SYSTEM AND METHOD FOR RESETTING LATCH IN DC-DC
CONVERTERS”
MINDA CORPORATION LIMITED, of E-5/2, Chakan Industrial Area, Phase-III, M.I.D.C., Nanekarwadi,Tal: Khed, Dist.Pune-410 501, India
The following specification particularly describes the invention.

SYSTEM AND METHOD FOR RESETTING LATCH IN DC-DC
CONVERTERS
FIELD OF THE DISCLOSURE
The present disclosure relates to the field of electric vehicles. More specifically, the present disclosure relates to system and method for resetting latch in DC-DC converter of the electric vehicle.
BACKGROUND OF THE DISCLOSURE
It is well known that in the field of automation, individual circuit components are typically protected from short-circuiting and excessive currents by a fuse or a circuit breaker interposed between the component and a power supply. Electronic components are typically powered by a constant voltage direct current (DC) power source. These electronic components are specifically designed to be powered with a particular DC voltage, with some margin of error. Any spike, even temporary, in the input voltage may cause permanent component failures. In the similar fashion, DC-DC converters, in an electric vehicle, are also protected from short-circuiting and excessive currents by a fuse. In electric vehicles, the DC-DC converter is used to convert the available battery voltage to suitable voltage (i.e. 12V, 18 V) as per the requirement, to feed into auxiliary loads of the vehicle. However, there may be few temporary/momentary faults which may disturb the working of DC-DC converters and the high voltage transients may be passed to the loads. Some of these faults may be high voltage transients and high side MOSFET faults. In order to operate the vehicle normally, it is necessary that during these momentary faults, the DC-DC converter should not allow to pass high voltage transients to output such as auxiliary loads.
There exist various methods in the art to prevent the DC- DC converter to pass the high voltage transient in the faulty situation. Few of the existing methods are based on Silicon Controlled Rectifiers (SCR) latches, which perform one of the following actions during the momentary faults:
■ Blow of the input line fuse of Converter, or
■ Disconnect the series pass element (MOSFET or Relay) between input

and output of the Converter.
However, the existing classical methods based on SCR Latches counter many problems. For example, in the existing method, an SCR is fired whenever there is an occurrence of fault in DC-DC converter. The SCR in turn presents a short-circuit condition, thereby blowing out a series fuse. Since the fuse has been blown, it needs a replacement before the system is restored to its former condition, once the fault is rectified. Also, the SCR is prone to nuisance tripping due to stray transients encountered in power and signal lines of the electric vehicle subsystems. Hence, solution pertaining to the SCR based latch suffers from two major drawbacks mentioned as follows:
• It is not “user resettable” since it blows out a fuse, which needs replacement by a service technician.
• It is prone to nuisance tripping, leading to undesired tripping of the SCR, even when the system is healthy.
Hence, there is a need to provide improved techniques which overcome the above-mentioned drawbacks. Accordingly, the present disclosure is directed to provide most eminent solution to the aforementioned problems existing in the prior art.
OBJECT OF THE DISCLOSURE
An object of the present disclosure is to provide a system for resetting electronic latch in DC-DC converters.
Another object of the present disclosure is to provide a method for resetting electronic latch in DC-DC converters.
SUMMARY OF THE DISCLOSURE
In an aspect, the present disclosure is related to a system for resetting latch in electronic converters. The disclosed system may comprise of a DC-DC converter, a fault detection circuit, a latch circuit and a protection switch. The DC-DC converter may receive power from a power supply unit and convert received power

into desired level of DC power. The protection switch is placed between Power supply unit and DC-DC converter. The latch circuit is connected to the fault detection circuit and the protection circuit.
The fault detection circuit may be connected to the DC-DC converter and may detect at least one type of fault occurring at the DC-DC converter. The latch circuit may be configured to: switch OFF the protection switch upon detection of the fault by the fault detection circuit and in response the protection switch is configured to disconnect the DC-DC converter from the power supply unit. The system may also comprise a latch reset circuit connected to the latch circuit, wherein the latch reset unit is configured to reset latch circuit for further use.
In another aspect of the present disclosure, the fault detection circuit may comprise a first resistor R6 connected to a second resistor R7. The output voltage (Vout) of DC-DC converter is connected to the fault detection circuit i.e. R6 and R7. The voltage across the first resistor and the second resistor may increase when the fault occurs in the DC-DC converter.
In still another aspect of the present disclosure, the latch circuit may comprise a first transistor Q3 connected to a second transistor Q2.
In another aspect of the present disclosure, the first transistor Q3 may be turned ON upon detection of the fault and may turn ON the second transistor Q2 to form the latch circuit.
In still another aspect of the present disclosure, the latch reset circuit may comprise a third resistor connected to a fourth resistor and a capacitor.
In yet another aspect of the present disclosure, the latch circuit may turn ON a third transistor Q1 which turns OFF the protection switch.
In another aspect of the present disclosure, the latch reset input is provided by a user by reinserting ignition key.

In still another aspect of the present disclosure, the latch reset input may turn ON the fourth transistor Q4 which resets the latch circuit.
In yet another aspect of the present disclosure, the type of fault may be high voltage transients and high side MOSFET fault.
In an aspect, the present disclosure relates to a method for resetting latch in electronic converters. The method may comprise receiving power from a power supply unit and converting the received power into desire level of DC power. Then, at least one type of fault that occurs in the DC-DC converter may be detected and the protection switch may be switched OFF upon detection of the fault. The DC-DC converter may be disconnected from the power supply unit and the latch circuit may be reset for further use.
In another aspect of the present disclosure, a latch reset input is provided to the latch reset circuit by a user by reinserting ignition key.
Those skilled in the art will appreciate that the conception upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures for carrying out the several purposes of the invention. It is important therefore that the claims be regarded as including such equivalent constructions as do not depart from the spirit and scope of the invention.
The following paragraphs are provided in order to describe the best mode of working the invention and nothing in this section should be taken as a limitation of the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Further aspects and advantages of the present disclosure will be readily understood from the following detailed description with reference to the accompanying drawings, where like reference numerals refer to identical or similar or functionally

similar elements. The figures together with the detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the aspects/embodiments and explain various principles and advantages, in accordance with the present disclosure wherein:
Figure 1 depicts a basic block-level system schematic of system for resetting electronic latch in DC-DC converters, according to an embodiment of the present disclosure;
Figure 2 depicts a component level circuit schematic implementation of the system shown in Figure 1, according to an embodiment of the present disclosure;
Figure 3 depicts a circuit diagram to provide “Latch Reset” pulse, according to an embodiment of the present disclosure; and
Figure 4 depicts a flow chart illustrating steps for resetting electronic latch in DC-DC converters.
DESCRIPTION OF THE PRESENT DISCLOSURE
Referring to the drawings, there is shown an illustrative embodiment of the system for resetting electronic latch in DC-DC converters, according to the present disclosure. It should be understood that the disclosure is susceptible to various modifications and alternative forms; specific embodiments thereof have been shown by way of example in the drawings and will be described in detail below.
Before describing in detail embodiments, it may be observed that the novelty and inventive step that are in accordance with the present disclosure resides in the circuit assembly of the system for resetting electronic latch in DC-DC converters in electric vehicles. It is to be noted that a person skilled in the art can be motivated from the present disclosure and modify the various constructions of assembly, which may vary from vehicle to vehicle. However, such modification should be construed within the spirit and scope of the invention. Accordingly, the drawings show only

those specific details that are pertinent for understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device that comprises a list of components does not comprise only those components but may comprise other components not expressly listed or inherent to such setup or device. In other words, one or more elements in a system or apparatus proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.
Fig. 1 depicts the basic block-level system (100) schematic of the system for resetting electronic latch in DC-DC converters. The system (100) may comprise a DC-DC converter (101), a fault detection circuit (103), a latch circuit (105), a protection switch (107) and a latch reset circuit (111). As shown in fig. 1, the protection switch (107) may be placed between a power supply unit (109) and DC-DC converter (101). The latch circuit (105) may be connected to the fault detection circuit (103) and the protection circuit (107).
The DC-DC converter (101) may receive an input voltage from the power supply unit (109), if the protection switch (107) is ON. The DC-DC converter (101) may convert the input voltage into a suitable voltage such as 12 V and provide an output voltage to auxiliary loads (not shown in fig. 1). It should be apparent to a person skilled in the art that the DC-DC converter (101) may convert the input voltage into any suitable voltage depending on the auxiliary load.
In the event, any momentary fault occurs in the DC-DC converter, the fault detection circuit (103) may detect the fault and send a signal to latch circuit (105). In an embodiment, the momentarily fault may be voltage transients, high side MOSFET fault, etc. It should be apparent to a person skilled in the art that other

momentary faults can also occur, which will fall within the scope of the present disclosure. In an embodiment, momentary fault may be any fault which is temporary, for example, which occurs in a pulse. The latch circuit (105) may then operate the protection switch (107) to disconnect DC-DC converter (101) from the power supply unit (109), to avoid damage to auxiliary loads connected on the DC-DC converter (101). This way, the latch circuit (105) may protect the DC-DC converter (101) from the momentary faults. The latch reset circuit (111) may then reset the latch circuit (105) by generating a “Latch Reset” pulse. The “Latch Reset” may be generated when a user reinserts the ignition key, as will be explained in detail with reference to Fig. 3.
Fig. 2 depicts component level circuit diagram of the system (100) of Fig. 1. As shown in Fig. 2, in an embodiment, the fault detection circuit (103) may comprise a first resistor (R6) connected in series to a second resistor (R7). The latch circuit (105) may comprise a first transistor (Q3) connected to a second transistor (Q2). As shown in Fig. 2, the output voltage (Vout) of DC-DC converter (101) is connected to the fault detection circuit (103) i.e. the first and second resistors R6 and R7. When the momentary fault occurs in the DC-DC converter (101) i.e. when the output voltage (Vout) is high, the voltage across the first and second resistors R6 and R7 may increase, which causes the base-emitter voltage across the first transistor Q3 to increase and results in turning ON the first transistor Q3. In response, the first transistor Q3 causes the base-emitter voltage across the second transistor Q2 to increase and results in turning ON the second transistor Q2. In this way, the first and second transistor Q2 and Q3 latch with each other and form the latch circuit (105) of Fig. 1. After latching of the first and second transistors Q2 and Q3, the base-emitter voltage across the transistor Q1 is increased, results in turning ON of transistor Q1. In response, transistor Q1 switches OFF the protection switch (107). As shown in Fig. 2, collector of transistor Q1 is connected to the protection switch (107). Hence, when the transistor Q1 is ON, it causes the protection switch (107) to go OFF. The protection switch (107) then cuts off the power supply to the DC-DC converter (101), thereby, protecting the DC-DC converter (101) from momentary fault. In an embodiment, the protection switch (107) may comprise of PMOS MOSFET.

To reset the latch circuit (105), transistor Q4 of Fig. 2 is used. As shown in Fig. 2, base of transistor Q4 is connected to an external pulse “Latch Reset”. In an embodiment, the “Latch Reset” is provided by Key-in-out signal given by the user.
Fig. 3 depicts a latch reset circuit (111) for generating “Latch Reset” pulse. As shown in Fig. 3, the latch reset circuit (111) may comprise a third resistor (Rr1) connected to a fourth resistor (Rr2) and a capacitor (Cr1). When the user takes out and re-inserts the ignition key, RC network Rr1, Cr1 and Rr2 converts 0 Volt to 12 Volts and provides a narrow reset pulse as shown in Fig. 3.
This reset pulse is provided to the base of transistor Q4, which switches ON the transistor, Q4¸which in turn removes voltage from base of transistors, Q1 and Q3, thereby breaking the latching. This results in reset of protection switch (107) back to ON State, providing power supply to the DC-DC converter (101).
In this way, the user can easily reset the latch circuit (105), which in turn resets the protection switch (107), without any intervention of a technician.
In an embodiment, when a momentary fault occurs, the user may get an indication on the instrument panel of the vehicle. Then, the user may start the vehicle again by re-inserting the key, causing a “Latch Reset” pulse to be sent to the latch circuit. Thereby, resetting the latch circuit. In an alternate embodiment, when the momentary fault occurs, the user may not get any indication. Rather, the user may start the vehicle again, causing a “Latch Reset” pulse to be sent to the latch circuit, thereby resetting the latch circuit.
One more advantage of the proposed latch circuit is that the proposed latch circuit avoids nuisance tripping as it does not use SCR (SCR can gets fired up due to interference/transients in gate circuit which causes the nuisance trip). The latch circuit (105) comprises of interconnection of bipolar junction transistors to form a circuit which is not prone to nuisance tripping.

It is to be noted that a person skilled in the art may use any other suitable component other than the disclosed components to achieve the desired objective.
Fig. 4 discloses a method for resetting a latch circuit (105) in an electric vehicle. As shown in Fig. 4, at step (201), the DC-DC converter receives power from a power supply unit (109) and converts the received power into desire level of DC power. Next, at step 203, the fault detection circuit (103) detects at least one type of fault that occurs in the DC-DC converter (101). At step 205, the latch circuit (105) is activated to turn OFF the protection switch (107). At step 207, the DC-DC converter is disconnected from the power supply (109), thereby protecting the DC-DC converter (101) from the fault. A “Latch Reset” pulse is provided. At step 209, the latch circuit (105) is reset, to turn ON the protection switch (107), thereby resuming the power supply to the DC-DC converter (101). In an embedment, the latch circuit (105) is reset by a latch reset circuit (111). The latch reset circuit (111) receives a latch reset input by a user when the user reinserts the ignition key. This way, the latch circuit (105) is easily reset by the user without any intervention from a technician.
The scope of the present disclosure is not limited to the explained embodiments only. A person skilled in the art can easily extend the scope and use of the invention to any other suitable field. The present disclosure is described with reference to the figures and specific embodiments, this description is not meant to be construed in a limiting sense. Various alternate embodiments of the invention will become apparent to persons skilled in the art upon reference to the description of the disclosure. It is therefore contemplated that such alternative embodiments form part of the present disclosure.

We Claim:
1. A system (100) for resetting latch in electronic converters, said system
(100) comprising:
a DC-DC converter (101) configured to receive power from a power supply unit (109) and convert received power into desired level of DC power;
a fault detection circuit (103) connected to the DC-DC converter (101), wherein the fault detection circuit is configured to detect at least one type of fault that occurs at the DC-DC converter (101);
a latch circuit (105) connected to the fault detection circuit (103) and a protection switch (107) placed between the power supply unit (109) and the DC-DC converter (101), wherein the latch circuit (105) is configured to:
switch OFF the protection switch (107) upon detection of the fault by the fault detection circuit (103) and in response the protection switch (107) is configured to disconnect the DC-DC converter (101) from the power supply unit (109); and
a latch reset circuit (111) connected to the latch circuit (105), wherein the latch reset unit is configured to reset latch circuit (105) for further use.
2. The system (100) as claimed in claim 1, wherein the fault detection circuit
(103) comprises:
a first resistor (R6) connected in series to a second resistor (R7).
3. The system (100) as claimed in claim 1, wherein the latch circuit (105)
comprises:
a first transistor (Q3) connected to a second transistor (Q2).
4. The system (100) as claimed in claim 2, wherein the voltage across the
first resistor (R6) and the second resistor (R7) increases when the fault occurs in
the DC-DC converter, due to increase of output voltage Vout.

5. The system (100) as claimed in claim 3, wherein the first transistor (Q3) is turned ON upon detection of the fault and turns ON the second transistor Q2 to form the latch circuit (105).
6. The system (100) as claimed in claim 1, wherein the latch reset circuit (111) comprises:
a third resistor (Rr1) connected to a fourth resistor (Rr2) and a capacitor (Cr1).
7. The system (100) as claimed in claim 3, wherein the latch circuit (105) turns OFF a third transistor (Q1) which turns OFF the protection switch (107).
8. The system (100) as claimed in claim 1, wherein the latch reset input is provided by a user by reinserting ignition key.
9. The system (100) as claimed in claim 8, wherein the latch reset input turns ON the fourth transistor (Q4) which turns ON the protection switch (107) resets the latch circuit (105).
10. The system (100) as claimed in claim 1, wherein the type of fault is high voltage transients and high side MOSFET fault.
11. A method (200) for resetting latch in electronic converters, the method comprising:
receiving (201) power from a power supply unit (109) and converting the received power into desire level of DC power;
detecting (203) at least one type of fault that occurs in the DC-DC converter (101);
switching OFF (205) the protection switch (107) upon detection of the fault;
disconnecting (207) the DC-DC converter (101) from the power supply unit (109); and

resetting (209) the latch circuit (105) by for further use.
12. The method (200) as claimed in claim 11, comprising:
providing a latch reset input to the latch reset circuit (111) by a user by reinserting ignition key.