Field of the Invention:
The present invention relates to a device for charging a load unit for vehicular applications such as two-wheeler, bike, motorbike, scooter and the like.

Background of the Invention:
Present day vehicles come with a charging device for charging a load unit such as a mobile device. The charging device derives power from the battery as provided in the vehicle and uses the same for supply to the load unit.

By way of example, the operations of the charging device may be controlled such that:
(a) only if the battery voltage is equal to or greater than a predetermined first threshold value the charging device should be allowed to turn ON.
(b) once the charging device has been turned ON, if the battery voltage falls below a second threshold value, which is less than the first threshold value, the charging device should be switched OFF automatically.

For example, the charging device is allowed to turn ON only if the battery level is more than about 80% of total capacity (or any other value instead of 80%). Once the charging device is turned ON, the charging device will monitor the battery level and will automatically switch OFF the charging device if the battery level is below about 60% of the total capacity (or any other value instead of 60%).

It has been found that by accurately controlling the operations of the charging device in a manner as mentioned above, the charging device does not over-drain the battery in the vehicle, does not adversely affect the remaining electrical appliances of the vehicle, and supplies maximum charge to the load unit.

However, with the increase in the complexity of the operations of the charging device, the charging device has to be constructed using costly components, which leads to increase in the overall cost of the charging device. Thus, there exists a need for a simple and cost efficient charging device.

Summary of the Invention:
This summary is provided to introduce a selection of concepts in a simplified format that is further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention and nor is it intended for determining the scope of the invention.

The present invention relates to a device for charging a load unit in accordance with an embodiment of the invention. The device comprises a buck converter defining an input terminal, an enable terminal, and an output terminal. The input terminal of buck converter is connectable to a battery and the output terminal is connectable to the load unit. The device further comprises a buck converter control unit connectable between the input and the enable terminals of the buck converter. In an embodiment of the invention, the buck converter control unit comprises a voltage divider element connectable to the input terminal of the buck converter. The buck converter control unit further comprises a comparator unit connectable to the input terminal of the buck converter such that the comparator unit is electrically parallel to voltage divider element. The buck converter control unit further comprises a first switch (Q1) connectable between an output terminal of the comparator unit and the enable pin of the buck converter. In an embodiment of the invention, the voltage divider element comprises a series combination of a first resistor (R1) and a second resistor (R2) which is further coupled in series with a parallel combination of a third resistor (R3) and a second switch (Q2). The comparator unit is adapted to receive a reference voltage from an intermediate point between the first and the second resistors (R1 and R2). The comparator unit is further adapted to generate a control signal based on the reference voltage and a voltage received from the battery. The comparator unit is furthermore adapted to provide the control signal to the first and the second switches (Q1 and Q2).

To further clarify the advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.

Brief Description of the drawings:
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Figure 1 illustrates a block diagram of a device (100) for charging load unit for vehicular application in accordance with an embodiment of the invention;
Figure 2 illustrates a detailed block diagram of the device (100) for charging load unit, showing some of the additional components that may be present in accordance with an embodiment of the invention; and
Figure 3 illustrates a complete circuit diagram of the device (100) for charging a load unit in accordance with an embodiment of the present invention.

Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present invention. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

DETAILED DESCRIPTION OF FIGURES
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the invention and are not intended to be restrictive thereof.

Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises... a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

Referring to Figure 1, there is illustrated block diagram of a device (100) for charging a load unit in accordance with an embodiment of the invention. The device (100) may be provided in a vehicle and may be used for charging a load which is connectable thereto, such as a mobile device (not shown). The device (100) comprises a buck converter (102) defining an input terminal (104), an enable terminal (106), and an output terminal (108). The input terminal (104) is connectable to a battery (110) and the output terminal (108) is connectable to a load unit (112).

The device (110) further comprises a buck converter control unit (114) which is connectable between the input terminal (104) and the enable terminal (106) of the buck converter (102). In an embodiment of the invention, the buck converter control unit (114) comprises a voltage divider element (116) connectable to the input terminal (104) of the buck converter (102). The buck converter control unit (114) further comprises a comparator unit (118) connectable to the input terminal (104) of the buck converter (102) such that the comparator unit (118) is electrically parallel to the voltage divider element (116). The device (100) furthermore comprises a first switch (120) connectable between an output terminal of the comparator unit (118) and the enable pin (106) of the buck converter (102).

In an embodiment of the invention, the voltage divider element (116) comprising a series combination of a first resistor (122) and a second resistor (124) which is further coupled in series with a parallel combination of a third resistor (126) and a second switch (128).

In an embodiment of the invention, the comparator unit (118) is adapted to:
• receive a reference voltage from an intermediate point (130) between the first and the second resistors (122 and 124),
• generate a control signal based on a value of the reference voltage, and
• provide the control signal to the first and the second switches (120 and 128).

In the following paragraphs, the working of the device is elaborated in detail.

In an embodiment of the invention, at the time of starting if the battery voltage is less than a predetermined first threshold value, the comparator unit (118) receives reference voltage from the intermediate point (130) between the first and the second resistors (122 and 124) whose value is less than a second threshold value and in response thereto provides a control signal which causes the first and the second switches (120 and 128) to be in ON condition, the first switch (120) in response to coming to the ON condition, provides a low/disable signal to the enable pin (106) of the buck converter (102) thereby maintaining the buck converter (102) in non-operating state, the second switch (128) in response to coming to the ON condition, provides a low resistance path which is in parallel to the third resistor (126) thereby causing the voltage divider element (116) to have an effective resistance equal to a summation of the first and the second resistors.

On the other hand, when the voltage from the battery is equal to the predetermined first threshold value, the comparator unit (118) receives reference voltage from the intermediate point (130) between the first and the second resistors (122 and 124) whose value is equal to a second threshold value and in response thereto provides a control signal which causes the first and the second switches (120 and 128) to be in OFF condition, the first switch (120) in response to coming to the OFF condition, provides a high/enable signal to the enable pin of the buck converter thereby bringing the buck converter to operating state, the second switch (128) in response to coming to the OFF condition, provides a very high resistance path which is in parallel to the third resistor (126) thereby causing the voltage divider element (116) to have an effective resistance equal to a summation of the first, the second and the third resistors.

Even when the voltage from the battery is more than the predetermined first threshold value, the comparator unit (118) receives reference voltage from the intermediate point (130) between the first and the second resistors (122 and 124) whose value is greater than a second threshold value and in response thereto provides a control signal which maintains the first and the second switches (120 and 128) in OFF condition, the first switch (120) in response to being maintained in the OFF condition, provides a high/enable signal to the enable pin of the buck converter thereby maintaining the buck converter in the operating state, the second switch (128) in response to being maintained in the OFF condition, provides a very high resistance path which is in parallel to the third resistor (126) thereby causing the voltage divider element (116) to have an effective resistance equal to a summation of the first, the second and the third resistors.

Thus, the device is allowed to turn ON only if the battery level is equal to or more than the predetermined first threshold value. In an embodiment of the invention, the predetermined first threshold value for example may be about 80% of total capacity. In another embodiment of the invention, the predetermined first threshold value may be any value instead of 80%.

Once the charging device is turned ON, the charging device will monitor the battery level and will automatically switch OFF the charging device if the battery level is below a predetermined third threshold value. The predetermined third threshold value is less than the predetermined first threshold value.

In particular, when the voltage from the battery is equal to or more than a predetermined third threshold value, the comparator unit (118) receives reference voltage from the intermediate point between the first and the second resistors (122 and 124) whose value is equal to or more than a second threshold value and in response thereto provides a control signal which maintains the first and the second switches (120 and 128) in OFF condition, the first switch (120) in response to being maintained in the OFF condition, provides a high/enable signal to the enable pin of the buck converter thereby maintaining the buck converter in the operating state, the second switch (128) in response to being maintained in the OFF condition, provides a very high resistance path which is in parallel to the third resistor (126) thereby causing the voltage divider element (116) to have an effective resistance equal to a summation of the first, the second and the third resistors.

On the other hand, wherein when the voltage from the battery is less than the predetermined third threshold value, the comparator unit (118) receives reference voltage from the intermediate point between the first and the second resistors (122 and 124) whose value is less than a second threshold value and in response thereto provides a control signal which causes the first and the second switches (120 and 128) to be in ON condition, the first switch (120) in response to coming to the ON condition, provides a low/disable signal to the enable pin of the buck converter thereby brings the buck converter to a non-operating state, the second switch (128) in response to coming to the ON condition, provides a low resistance path which is in parallel to the third resistor (126) thereby causing the voltage divider element to have an effective resistance equal to a summation of the first and the second resistors.

Thus, it can be seen that while the device is allowed to turn ON only if the battery level is equal to or more than the predetermined first threshold value, the device is turned OFF only if the battery level is less than the predetermined third threshold value. Once the device has been turned OFF, it will be turned ON again only when the battery level is equal to or more than the predetermined first threshold value. Thus, when the battery level is equal to or more than the predetermined third threshold value but less than the predetermined first threshold value, the device is still maintained in OFF state.

For instance, when the voltage from the battery is greater than a predetermined third threshold value, but less than a predetermine first threshold value, the comparator unit (118) receives reference voltage from the intermediate point (130) between the first and the second resistors (122 and 124) whose value is less than a second threshold value and in response thereto provides a control signal which causes the first and the second switches (120 and 128) to be in ON condition, the first switch (120) in response to being in ON condition, provides a low/disable signal to the enable pin of the buck converter thereby keeps the buck converter in a non-operating state, the second switch (128) in response to being in ON condition, provides a low resistance path which is in parallel to the third resistor (126) thereby causing the voltage divider element to have an effective resistance equal to a summation of the first and the second resistors.

Thus, it can be seen that:
• when the voltage from the battery is equal to or greater than a predetermined first threshold value; the value of the reference voltage as received from the intermediate point (130) between the first and the second resistors (122 and 124) is equal to or greater than the predetermined second threshold value.
• when the voltage from the battery is less than a predetermined third threshold value; the value of the reference voltage as received from the intermediate point (130) between the first and the second resistors (122 and 124) is less than the predetermined second threshold value;
• when the voltage from the battery is less than the predetermined first threshold value but equal to or greater than the predetermined third threshold value and the voltage divider element has an effective resistance equal to a summation of the first, the second and the third resistors (or in other words, if the first and the second switches (120 and 128) are in OFF condition); the value of the reference voltage as received from the intermediate point (130) between the first and the second resistors (122 and 124) is equal to or greater than the predetermined second threshold value;
• when the voltage from the battery is less than the predetermined first threshold value but equal to or greater than a predetermined third threshold value and the voltage divider element has an effective resistance equal to a summation of the first and the second resistors (or in other words, if the first and the second switches (120 and 128) are in ON condition); the value of the reference voltage as received from the intermediate point (130) between the first and the second resistors (122 and 124) is less than the predetermined second threshold value.

Thus, it can be said that the value of the reference voltage is dependent upon the voltage being supplied by the battery and the effective resistance value of the voltage divider element.

By controlling the effective resistance of the voltage divider element, the present invention is able to control the operations of the charging device such that:
(a) only if the battery voltage is equal to or greater than a predetermined first threshold value the charging device should be allowed to turn ON.
(b) once the charging device has been turned ON, if the battery voltage falls below a third threshold value, which is less than the first threshold value, the charging device should be switched OFF automatically.

It can be seen that the effective resistance of the voltage divider element is being controlled by the second switch (128) while the first switch (120) controls the nature of control signal being provided to the buck converter (102).

Now referring to Figure 2, there is provided a more detailed block diagram of the device (100) for charging a load unit showing some of the additional components that may be present. For instance, the device (100) for charging a load unit may further comprise a transient protection unit (132) providing a transient free input to the device. The device (100) for charging a load unit for vehicles may further comprise a reverse polarity protection unit (134) connected in series with input line providing circuit from polarity interchange. The device (100) for charging a load unit for vehicles may further comprise a capacitor filter (136) connected between input and ground for providing smooth linear input to the buck converter control unit (114). The device (100) for charging a load unit for vehicles may further comprise a current sense unit (138) providing current compensation in the circuit. The device (100) for charging a load unit for vehicles may further comprise a voltage feedback unit (140) providing controlled output voltage to the load (112).

Now referring to Figure 3, there is illustrated a complete circuit diagram of the device (100) for charging a load unit in accordance with an embodiment of the present invention. In an embodiment of the invention, it can be seen that in an embodiment of the invention, the first and the second switches are a first and a second transistor (Q1 and Q2). In an embodiment of the invention, the comparator unit (118) may be a single supply comparator configuration and comprises a three-terminal comparator device (U2) that defines an Anode, a Cathode and a Reference terminal.

In an embodiment of the invention, the Cathode terminal of the three-terminal comparator device (U2) is connected to a base terminal of the first transistor (Q1) and to a base terminal of the second transistor (Q2).

In an embodiment of the invention, an electrical path between the Cathode terminal of the three-terminal comparator device (U2) and the base terminal of the first transistor (Q1) is provided with a first Zener diode (Z1) and an electrical path between the Cathode terminal of the three-terminal comparator device (U2) and the base terminal of the second transistor (Q2) is provided with a second Zener diode (Z2).

In an embodiment of the invention, a first end of a resistor (R7) is connected between the first Zener diode (Z1) and the base terminal of the first switch (Q1) and a second end of the resistor (R7) is connected to a ground terminal; and a first end of a resistor (R6) is connected between the second Zener diode (Z2) and the base terminal of the second switch (Q2) and a second end of the resistor (R6) is connected to a ground terminal.

In an embodiment of the invention, the emitter terminals of each of the first and the second transistors (Q1 and Q2) is connected to the ground terminal. In an embodiment of the invention, collector terminal of the first transistor (Q1) is connected between the battery and the input terminal of the buck converter (102) via a resistor (R8); and collector terminal of the first transistor (Q1) is furthermore coupled to the enable terminal of buck converter (102).

In an embodiment of the invention, the transient protection unit (132) may comprise a transient voltage suppressor diode (TVS). In an embodiment of the invention, the reverse polarity protection unit (134) may comprise a diode (D1). In an embodiment of the invention, the capacitor filter (136) may comprise one or more capacitors. In an embodiment of the capacitor filter (136) may comprise capacitors C1 and C2 which are connected in parallel.

In an embodiment of the invention, the first resistor (122) may include one resistor or two or more resistors connected in series or in parallel. In an embodiment of the invention, the first resistor (122) may include resistors R1 and R15 connected in parallel. In an embodiment of the invention, the second resistor (124) may include resistor R2. In an embodiment of the invention, the third resistor (126) includes resistor R3.

In an embodiment of the invention, the Cathode terminal of the three-terminal comparator device (U2) is connected to a battery via a resistor R4.

While certain present preferred embodiments of the invention have been illustrated and described herein, it is to be understood that the invention is not limited thereto. Clearly, the invention may be otherwise variously embodied, and practiced within the scope of the following claims.

Claims:WE CLAIM:

1. A device (100) for charging a load unit, comprising:
a buck converter (102) defining an input terminal (104), an input terminal (106), and an output terminal (108); the input terminal (104) being connectable to a battery (110) and the output terminal (108) being connectable to the load unit (112); and
a buck converter control unit (114) connectable between the input (104) and the enable terminals (106) of the buck converter (102);
characterised in that the buck converter control unit (114) comprising;
a voltage divider element (116) connectable to the input terminal (104) of the buck converter (102);
a comparator unit (118) connectable to the input terminal (104) of the buck converter (102) such that the comparator unit (118) is electrically parallel to voltage divider element (116);
a first switch (120) connectable between an output terminal of the comparator unit (118) and the enable pin (106) of the buck converter (102);
the voltage divider element (116) comprising a series combination of a first resistor (122) and a second resistor (124) which is further coupled in series with a parallel combination of a third resistor (126) and a second switch (128); and
the comparator unit (118) receiving a reference voltage from an intermediate point (130) between the first and the second resistors (122 and 124), the comparator unit (118) being adapted to generate a control signal based on the reference voltage and a voltage received from the battery (110), the comparator unit (118) being further adapted to provide the control signal to the first and the second switches (120 and 128).

2. The device as claimed in claim 1, wherein at the time of starting if the battery voltage is less than a predetermined first threshold value, the comparator unit (118) receives reference voltage from the intermediate point (130) between the first and the second resistors (122 and 124) whose value is less than a second threshold value and in response thereto provides a control signal which causes the first and the second switches (120 and 128) to be in ON condition, the first switch (120) in response to coming to the ON condition, provides a low/disable signal to the enable pin (106) of the buck converter (102) thereby maintaining the buck converter (102) in non-operating state, the second switch (128) in response to coming to the ON condition, provides a low resistance path which is in parallel to the third resistor (126) thereby causing the voltage divider element (116) to have an effective resistance equal to a summation of the first and the second resistors.

3. The device as claimed in claim 1, wherein when the voltage from the battery is equal to a predetermined first threshold value, the comparator unit (118) receives reference voltage from the intermediate point (130) between the first and the second resistors (122 and 124) whose value is equal to a second threshold value and in response thereto provides a control signal which causes the first and the second switches (120 and 128) to be in OFF condition, the first switch (120) in response to coming to the OFF condition, provides a high/enable signal to the enable pin of the buck converter thereby bringing the buck converter to operating state, the second switch (128) in response to coming to the OFF condition, provides a very high resistance path which is in parallel to the third resistor (126) thereby causing the voltage divider element (116) to have an effective resistance equal to a summation of the first, the second and the third resistors.

4. The device as claimed in claim 1, wherein when the voltage from the battery is more than a predetermined first threshold value, the comparator unit (118) receives reference voltage from the intermediate point (130) between the first and the second resistors (122 and 124) whose value is greater than a second threshold value and in response thereto provides a control signal which maintains the first and the second switches (120 and 128) in OFF condition, the first switch (120) in response to being maintained in the OFF condition, provides a high/enable signal to the enable pin of the buck converter thereby maintaining the buck converter in the operating state, the second switch (128) in response to being maintained in the OFF condition, provides a very high resistance path which is in parallel to the third resistor (126) thereby causing the voltage divider element (116) to have an effective resistance equal to a summation of the first, the second and the third resistors.

5. The device as claimed in claim 1, wherein when the voltage from the battery is equal to a predetermined third threshold value, the comparator unit (118) receives reference voltage from the intermediate point between the first and the second resistors (122 and 124) whose value is equal to a second threshold value and in response thereto provides a control signal which maintains the first and the second switches (120 and 128) in OFF condition, the first switch (120) in response to being maintained in the OFF condition, provides a high/enable signal to the enable pin of the buck converter thereby maintaining the buck converter in the operating state, the second switch (128) in response to being maintained in the OFF condition, provides a very high resistance path which is in parallel to the third resistor (126) thereby causing the voltage divider element (116) to have an effective resistance equal to a summation of the first, the second and the third resistors.

6. The device as claimed in claim 1, wherein when the voltage from the battery is less than a predetermined third threshold value, the comparator unit (118) receives reference voltage from the intermediate point between the first and the second resistors (122 and 124) whose value is less than a second threshold value and in response thereto provides a control signal which causes the first and the second switches (120 and 128) to be in ON condition, the first switch (120) in response to coming to the ON condition, provides a low/disable signal to the enable pin of the buck converter thereby brings the buck converter to a non-operating state, the second switch (128) in response to coming to the ON condition, provides a low resistance path which is in parallel to the third resistor (126) thereby causing the voltage divider element to have an effective resistance equal to a summation of the first and the second resistors.

7. The device as claimed in claim 1, wherein when the voltage from the battery is greater than a predetermined third threshold value, but less than a predetermine first threshold value, the comparator unit (118) receives reference voltage from the intermediate point (130) between the first and the second resistors (122 and 124) whose value is less than a second threshold value and in response thereto provides a control signal which causes the first and the second switches (120 and 128) to be in ON condition, the first switch (120) in response to being in ON condition, provides a low/disable signal to the enable pin of the buck converter thereby keeps the buck converter in a non-operating state, the second switch (128) in response to being in ON condition, provides a low resistance path which is in parallel to the third resistor (126) thereby causing the voltage divider element to have an effective resistance equal to a summation of the first and the second resistors.

8. The device as claimed in claim 1, wherein the value of the reference voltage is dependent upon the voltage being supplied by the battery and the effective resistance value of the voltage divider element.

9. The device as claimed in claim 1, wherein the first and the second switches are a first and a second transistor (Q1 and Q2).

10. The device as claimed in claim 1, wherein the comparator unit (118) is in a single supply comparator configuration and comprises a three-terminal comparator device (U2) that defines an Anode, a Cathode and a Reference terminal.

11. The device as claimed in claim 10, wherein a Cathode terminal of the three-terminal comparator device (U2) is connected to a base terminal of the first transistor (Q1) and to a base terminal of the second transistor (Q2).

12. The device as claimed in claim 11, wherein an electrical path between the Cathode terminal of the three-terminal comparator device (U2) and the base terminal of the first transistor (Q1) is provided with a first Zener diode (Z1) and an electrical path between the Cathode terminal of the three-terminal comparator device (U2) and the base terminal of the second transistor (Q2) is provided with a first Zener diode (Z2).

13. The device as claimed in claim 12, wherein:
a first end of a resistor (R7) is connected between the first Zener diode (Z1) and the base terminal of the first switch (Q1) and a second end of the resistor (R7) is connected to a ground terminal;
a first end of a resistor (R6) is connected between the second Zener diode (Z2) and the base terminal of the second switch (Q2) and a second end of the resistor (R6) is connected to a ground terminal.

14. The device as claimed in claim 9, wherein emitter terminals of each of the first and the second transistors (Q1 and Q2) is connected to the ground terminal.

15. The device as claimed in claim 9, wherein:
collector terminal of the first transistor (Q1) is connected between the battery and the input terminal of the buck converter via a resistor (R8); and
collector terminal of the first transistor (Q1) is furthermore coupled to the enable terminal of buck converter.

16. The device as claimed in claim 1, further comprising:
a transient protection unit (132) providing a transient free input to the device;
a reverse polarity protection unit (134) connected in series with input line providing circuit from polarity interchange;
a capacitor filter (136) connected between input and ground for providing smooth linear input to the buck converter control unit;
a current sense unit (138) providing current compensation in the circuit; and
a voltage feedback unit (140) providing controlled output voltage to the load.