Direct current conversion device and operation method of the same

This application claims priority to China Application Serial Number 201510184329.2, filed Apr. 17, 2015, which is herein incorporated by reference.

The present invention relates to a direct current conversion technology. More particularly, the present invention relates to a direct current conversion device and an operation method of the same.

Direct current (DC) power conversion is used to convert the DC electric energy between different voltage levels. In many applications, a multiple of series-connected DC conversion circuits or DC conversion modules are used to lower the voltage level of each power conversion circuit. When the DC input ends or the DC output ends of the multiple of DC conversion circuits are coupled in series, the DC input end or the DC output end of each of the DC conversion circuits has to be controlled within a predetermined voltage range to avoid the protective shut-down of the power conversion circuit or the damage of the circuit components due to the voltage that exceeds the limit. However, the implementation and the effect of the control method may vary with the circuit configuration and the operation condition, and may be related to the cost and efficiency of the converter circuit.

When a multiple of energy storing elements are used in the energy storing system such as batteries and capacitors, the storing capacity can be fully used when the charging and discharging energy matches the capacity of each of the energy storing units.

One aspect of the invention provides a direct current (DC) conversion device. The conversion device includes a first DC converter, a second DC converter, a voltage difference adjusting unit, a first control unit and a second control unit. The first DC converter includes a first input end to receive a first input current and a first input voltage, and a first output end to generate a first output current and a first output voltage, wherein the first output end is electrically coupled to a first energy storing element. The second DC converter includes a second input end to receive a second input current and a second input voltage, and a second output end to generate a second output current and a second output voltage, wherein the second output end is electrically coupled to a second energy storing element. The voltage difference adjusting unit is electrically coupled to the first DC converter and the second DC converter to generate a voltage difference adjusting signal. The first control unit generates a first control signal to control the first DC converter. The second control unit generates a second control signal to control the second DC converter to balance the first output voltage and the second output voltage according to the voltage difference adjusting signal.

Yet another aspect of the present invention is to provide a DC conversion device. The conversion device includes a first DC converter, a plurality of second DC converters, a plurality of voltage difference adjusting units, a first control unit and a plurality of second control units. The first DC converter includes a first input end to receive a first input current and a first input voltage, and a first output end to generate a first output current and a first output voltage, wherein the first output end is electrically coupled to a first energy storing element. Any one of the second DC converters includes a second input end to receive a second input current and a second input voltage, and a second output end to generate a second output current and a second output voltage, wherein the second input ends of the plurality of second DC converters are electrically coupled to the first input end in series, and the second output ends of the plurality of second DC converters are electrically coupled to a plurality of second energy storing elements respectively. The voltage difference adjusting units are electrically coupled to the first DC converter and the second DC converters to generate a plurality of voltage difference adjusting signals. The first control unit generates a first control signal to control the first DC converter. Any one of the second control units generates a corresponding second control signal to control the corresponding second DC converter according to the corresponding voltage difference adjusting signal to balance the first output voltage and the corresponding second output voltage.

Still another aspect of the present invention is to provide a DC conversion device operation method used in a DC conversion device. The DC conversion device operation method includes the steps outlined below. A first input current is received by a first input end of a first DC converter to generate a first output current at a first output end of the first DC converter, wherein the first input end has a first input voltage and the first output end is electrically coupled to a first energy storing element. A second input current is received by a second input end of a second DC converter to generate a second output current at a second output end of the second DC converter, wherein the second input end has a second input voltage and the second output end is electrically coupled to a second energy storing element. A voltage difference adjusting signal is generated by a voltage difference adjusting unit electrically coupled to the first DC converter and the second DC converter. A first control signal is generated to control the first DC converter by a first control unit. A second control signal is generated by a second control unit to control the second DC converter to balance the first output voltage and the second output voltage according to the voltage difference adjusting signal.

These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims.

It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed.

The invention can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows:

FIG. 1 is a circuit diagram of a DC conversion device in an embodiment of the present invention;

FIG. 2 is a circuit diagram of a DC conversion device in an embodiment of the present invention;

FIG. 3 is a circuit diagram of a DC conversion device in an embodiment of the present invention;

FIG. 4 is a circuit diagram of a DC conversion device in an embodiment of the present invention;

FIG. 5 is a circuit diagram of a DC conversion device in an embodiment of the present invention;

FIG. 6 is a circuit diagram of a DC conversion device in an embodiment of the present invention;

FIG. 7 is a circuit diagram of a DC conversion device in an embodiment of the present invention;

FIG. 8 is a circuit diagram of a DC conversion device in an embodiment of the present invention; and

FIG. 9 is a flow chart of a DC conversion device operation method in an embodiment of the present invention.

Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

Reference is now made to FIG. 1 . FIG. 1 is a circuit diagram of a direct current (DC) conversion device 1 in an embodiment of the present invention. The DC conversion device 1 includes a first DC converter 100 , a second DC converter 102 , a voltage difference adjusting unit 104 , a first control unit 106 and a second control unit 108 .

The first DC converter 100 includes a first input end In 1 and a first output end O 1 . The first input end In 1 receives a first input current Iin 1 and has a first input voltage Vin 1 . The first DC converter 100 generates a first output current Io 1 at the first output end O 1 . In an embodiment, the first DC converter 100 is a two-level DC to DC converter or a multi-level DC to DC converter, such as a three-level DC to DC converter to convert the first input current Iin 1 to the first output current Io 1 to accomplish the conversion of DC electronic energy between different voltages.

The first output end O 1 is electrically coupled to a first energy storing element Csc 1 . In an embodiment, the first energy storing element Csc 1 is a capacitor, a super capacitor or other types of energy storing elements. The first output current Io 1 generated at the first output end O 1 can charge the first energy storing element Csc 1 . The first output end O 1 outputs a first output voltage Vsc 1 according to the charging result.

The second DC converter 102 includes a second input end In 2 and a second output end O 2 . The second input end In 2 receives a second input current Iin 2 and has a second input voltage Vin 2 . The second DC converter 102 generates a second output current Io 2 at the second output end O 2 . In an embodiment, the second DC converter 102 is a two-level DC to DC converter or a multi-level DC to DC converter, such as a three-level DC to DC converter to convert the second input current Iin 2 to the second output current Io 2 to accomplish the conversion of DC electronic energy between different voltages.

The second input end In 2 is electrically coupled to the first input end In 1 in series. The second output end O 2 is electrically coupled to a second energy storing element Csc 2 . In an embodiment, the second energy storing element Csc 2 is a capacitor, a super capacitor or other types of energy storing elements. The second output current Io 2 generated at the second output end O 2 can charge the second energy storing element Csc 2 . The second output end O 2 has a second output voltage Vsc 2 according to the charging result.

In an embodiment, the DC conversion device 1 further includes bus capacitors C 1 and C 2 electrically coupled in series. The first input end In 1 and the second input end In 2 of the first DC converter 100 and the second DC converter 102 are electrically coupled to the bus capacitors C 1 and C 2 respectively. In some embodiments, the DC conversion device 1 includes resistors electrically coupled in series or a series-connected combination of units in which a resistor and a capacitor are electrically coupled in parallel, and it may be coupled to the first input end In 1 and the second input end In 2 of the first DC converter 100 and the second DC converter 102 respectively. The present invention is not limited thereto.

The voltage difference adjusting unit 104 is electrically coupled to the first DC converter 100 and the second DC converter 102 to generate a voltage difference adjusting signal Vdiff. In the present embodiment, the voltage difference adjusting unit 104 further includes a voltage difference calculating unit 110 and an adjusting unit 112 . The voltage difference calculating unit 110 receives the first output voltage Vsc 1 and the second output voltage Vsc 2 to calculate a difference value ΔV. The adjusting unit 112 perform adjustment according to the difference value ΔV to generate the voltage difference adjusting signal Vdiff. So the voltage difference adjusting signal may be equal to or corresponding to the difference value ΔV. However, the present invention is not limited thereto. In another embodiment, other configurations can be used to implement the voltage difference adjusting unit 104 . In an embodiment, the adjusting unit 112 can be such as, but not limited to a proportional-integral-derivative (PID) controller. In an embodiment, the adjusting unit 112 can adjust corresponding parameters according to the charging and discharging status of the energy storing elements, such as the amount or the sign of the parameters. In an embodiment, the adjusting unit 112 can adjusts corresponding parameters according to the operation frequency of the converters in the system. The present invention is not limited thereto.

The first control unit 106 generates a first control signal Icon 1 to control the first DC converter 100 . In the present embodiment, the first control unit 106 is a current control unit to generate the first control signal Icon 1 according to the first output current Io 1 and a reference current value Iref to further control the first output current Io 1 through a feedback mechanism. In the present embodiment, the reference current value Iref can be a given value. However, the present invention is not limited thereto.

The second control unit 108 generates a second control signal Icon 2 to control the second DC converter 102 according to the voltage difference adjusting signal Vdiff to further realize the adjustment of the second input voltage Vin 2 and the balance of the first output voltage Vsc 1 and the second output voltage Vsc 2 . In the present embodiment, the second control unit 108 is a voltage control unit to generate the second control signal Icon 2 according to the second input voltage Vin 2 and the reference voltage value Vref to further control the operation of the second DC converter 102 . In the present embodiment, the reference voltage value Vref is generated by a sum of a half of the total input voltage value Vin, which is Vin/2, and the voltage difference adjusting signal Vdiff. However, the present invention is not limited thereto. As a result, by using the design of the DC conversion device 1 , the control of the currents and the voltages of the first DC converter 100 and the second DC converter 102 can keep the voltages of the first energy storing element Csc 1 and the second energy storing element Csc 2 equal or close to each other. The serial-connected input voltages' difference between the first DC converter 100 and the second DC converter 102 can also be limited in a small range determined by the difference of the charging consumption rate and the difference of the capacitor capacity. However, the present invention is not limited thereto.

Reference is now made to FIG. 2 . FIG. 2 is a circuit diagram of a DC conversion device 2 in an embodiment of the present invention. The components included in the DC conversion device 2 may be identical to the DC conversion device 1 illustrated in FIG. 1 and the components may include the first DC converter 100 , the second DC converter 102 , the voltage difference adjusting unit 104 , the first control unit 106 and the second control unit 108 . However, the present invention is not limited thereto. In the present embodiment, the first control unit 106 performs control according to the first input current Iin 1 .

As illustrated in FIG. 2 , the first control unit 106 generates the first control signal Icon 1 to control the first DC converter 100 . In the present embodiment, the first control unit 106 is a current control unit to generate the first control signal Icon 1 according to the first input current Iin 1 and a reference current value Iref. However, the present invention is not limited thereto. The second control unit 108 may be identical to that illustrated in FIG. 1 . In the present embodiment, the reference current value Iref can be a given value, but the present invention is not limited thereto.

As a result, by using the close loop control of the first control unit 106 and the close loop control of the second control unit 108 , the input voltage under the stable operation of the first DC converter 100 and the input voltage under the stable operation of the second DC converter 102 which is connected in series with the first DC converter 100 in the input side and the voltages of the first energy storing element Csc 1 and the second energy storing element Csc 2 can all be controlled in a stable manner.

Reference is now made to FIG. 3 . FIG. 3 is a circuit diagram of a DC conversion device 3 in an embodiment of the present invention. The components included in the DC conversion device 3 may be identical to the DC conversion device 1 illustrated in FIG. 1 and the components may include the first DC converter 100 , the second DC converter 102 , the voltage difference adjusting unit 104 , the first control unit 106 and the second control unit 108 . However, the present invention is not limited thereto. In the present embodiment, the DC conversion device 3 may further include a power adjusting unit 300 .

In an embodiment, the input of the reference current value Iref can be given according to the requirement of the operation of the circuit system by the control loop of the DC conversion device 3 , such as but not limited to a total input power value. As illustrated in FIG. 3 , the power adjusting unit 300 receives a reference power value Pref and the total input power value, wherein the total input power value is a product of the total input voltage value Vin and the total input current value Iin, and the reference current value Iref is generated according to the reference power value Pref and the total input power value. However, the present invention is not limited thereto. The first control unit 106 can generate the first control signal Icon 1 according to the first output current Io 1 and the reference current value Iref. The second control unit 108 can be identical to that illustrated in FIG. 1 .

Reference is now made to FIG. 4 . FIG. 4 is a circuit diagram of a DC conversion device 4 in an embodiment of the present invention. The components included in the DC conversion device 4 may be identical to the DC conversion device 1 illustrated in FIG. 1 and the components may include the first DC converter 100 , the second DC converter 102 , the voltage difference adjusting unit 104 , the first control unit 106 and the second control unit 108 . However, the present invention is not limited thereto. In the present embodiment, the DC conversion device 4 may further include a voltage adjusting unit 400 .

In an embodiment, the input of the reference current value Iref can be given according to the requirement of the operation of the circuit system by the control loop of the DC conversion device 4 , such as but not limited to a total input voltage value Vin. As illustrated in FIG. 4 , the voltage adjusting unit 400 receives a reference voltage value Vref and the total input voltage value Vin, and the reference current value Iref is generated according to the reference voltage value Vref and the total input voltage value Vin. However, the present invention is not limited thereto. The first control unit 106 can generate the first control signal Icon 1 according to the first output current Io 1 and the reference current value Iref. The second control unit 108 can be identical to that illustrated in FIG. 1 .

Reference is now made to FIG. 5 . FIG. 5 is a circuit diagram of a DC conversion device 5 in an embodiment of the present invention. The components included in the DC conversion device 5 may be identical to the DC conversion device 3 illustrated in FIG. 3 and the components may include the first DC converter 100 , the second DC converter 102 , the voltage difference adjusting unit 104 , the first control unit 106 , the second control unit 108 and the power adjusting unit 300 . However, the present invention is not limited thereto. In the present embodiment, the DC conversion device 5 may further include a current adjusting unit 500 .

In the present embodiment, besides the control of voltage feedback loop, for example, based on the second input voltage Vin 2 by the second control unit 108 , the current feedback loop control can also be used to achieve better control performance, for example, based on the input current or the output current. As illustrated in FIG. 5 the current adjusting unit 500 receives the second output current Io 2 and the second control signal Icon 2 to generate a third control signal Icon 3 accordingly. However, the present invention is not limited thereto. The operation of the first control unit 106 can be identical to that illustrated in FIG. 3 .

In another embodiment, the current adjusting unit 500 receives the second input current Iin 2 and the second control signal Icon 2 to generate the third control signal Icon 3 . However, the present invention is not limited thereto.

It is appreciated that the current adjusting unit 500 can be used in the embodiments mentioned above, and is not limited to the embodiment illustrated in FIG. 5 .

Reference is now made to FIG. 6 . FIG. 6 is a circuit diagram of a DC conversion device 6 in an embodiment of the present invention. The components included in the DC conversion device 6 may be identical to the DC conversion device 1 illustrated in FIG. 1 and the components may include the first DC converter 100 , the second DC converter 102 , the voltage difference adjusting unit 104 , the first control unit 106 and the second control unit 108 . However, the present invention is not limited thereto. In the present embodiment, the DC conversion device 6 may further include a voltage adjusting unit 600 .

In an embodiment, the voltage adjusting unit 600 uses the first input voltage Vin 1 to control in a feedback mechanism and uses a sum of an adjusting reference voltage Vrref which is close to a half of the total input voltage value (Vin/2) and a negative value of the voltage difference signal Vdiff (i.e., −Vdiff) as the reference given signal of the voltage control loop to generate the reference current value Iref. However, the present invention is not limited thereto. The first control unit 106 can generate the first control signal Icon 1 according to a difference between the first output current Io 1 and the reference current value Iref. The second control unit 108 can be identical to that illustrated in FIG. 1 .

Reference is now made to FIG. 7 . FIG. 7 is a circuit diagram of a DC conversion device 7 in an embodiment of the present invention. The components included in the DC conversion device 7 may be identical to the DC conversion device 1 illustrated in FIG. 1 and the components may include the first DC converter 100 and the first control unit 106 . However, in the present embodiment, the DC conversion device 7 includes n−1 second DC converters 102 , n−1 voltage difference adjusting units 104 and n−1 second control units 108 . However, the present invention is not limited thereto.

As illustrated in FIG. 7 , the first output voltage Vsc 1 at the first output end O 1 of the first DC converter 100 can act as a reference voltage to calculate the voltage differences between the energy storing elements of different DC converters. However, the present invention is not limited thereto. Other DC converters (the group of second converters) can add 1/n of the total input voltage value Vin (i.e. Vin/n) to the voltage difference adjusting signals Vdiff 2 1 to Vdiff 2 n-1 so as to get the voltage control given signals Vref 2 1 to Vref 2 n-1 . For example, the second DC converter 102 corresponding to the bus capacitor Cn can add Vin/n to the voltage difference adjusting signal Vdiff 2 n-1 as the voltage control given signal Vref 2 n-1 .

Reference is now made to FIG. 8 . FIG. 8 is a circuit diagram of a DC conversion device 8 in an embodiment of the present invention. The components included in the DC conversion device 8 may be identical to the DC conversion device 1 illustrated in FIG. 1 and the components may include the first DC converter 100 and the first control unit 106 . In the present embodiment, the DC conversion device 8 includes n−1 second DC converters 102 , n−1 voltage difference adjusting units 104 and n−1 second control units 108 . However, the present invention is not limited thereto.

As illustrated in FIG. 8 , the first output voltage Vsc 1 at the first output end O 1 of the first DC converter 100 can act as a reference voltage to calculate the voltage differences between the energy storing elements of different DC converters. However, the present invention is not limited thereto. Other DC converters (the second converters) can add 1/n of the total voltage expected value Veref (i.e. Veref/n) to the voltage difference adjusting signals Vdiff 2 1 to Vdiff 2 n-1 so as to get the voltage control given signals Vref 2 1 to Vref 2 n-1 . However, the present invention is not limited thereto. The first DC converter 100 corresponding to the reference voltage can use input voltage to perform controlling and the voltage can be given as 1/n of the total voltage expected value Veref subtracting the voltage difference adjusting signals Vdiff 2 1 to Vdiff 2 n-1 of all the other converters. However, the present invention is not limited thereto. In the present embodiment, the DC conversion device 8 may further include a voltage adjusting unit 800 .

In an embodiment, the voltage adjusting unit 800 performs a feedback controlling through the first input voltage Vin 1 and uses 1/n of the total voltage expected value Veref subtracting the voltage difference adjusting signals Vdiff 2 1 to Vdiff 2 n-1 of all the other converters so as to get the reference given signal of the voltage control loop to generate the reference current value Iref. However, the present invention is not limited thereto. The first control unit 106 generates the first control signal Icon 1 according to the difference value between the first output current Io 1 and the reference current value Iref. Besides, the first control unit 106 in FIG. 8 can be omitted such that the first control signal Icon 1 is directly outputted by the voltage adjusting unit 800 .

Actually, any one of a multiple of converters can be selected as the first DC converter 100 such that the other converters become the second DC converters 102 . The configuration is not limited to those illustrated in FIG. 1 to FIG. 8 .

Reference is now made to FIG. 9 . FIG. 9 is a flow chart of a DC conversion device operation method 900 in an embodiment of the present invention. The DC conversion device operation method 900 can be used in each of the DC conversion devices illustrated in FIG. 1 to FIG. 8 . The following description is made by using the DC conversion device 1 illustrated in FIG. 1 as an example. However, unless the sequence of the steps is expressly indicated, the sequence of the steps is interchangeable, and all or part of the steps may be simultaneously, partially simultaneously, or sequentially performed.

In step 901 , the first input current Iin 1 is received by the first input end In 1 of the first DC converter 100 to generate the first output current Io 1 at the first output end O 1 of the first DC converter 100 , wherein the first input end In 1 has the first input voltage Vin 1 and the first output end O 1 has the first output voltage Vo 1 . The first DC converter 100 is electrically coupled to the first energy storing element Csc 1 .

In step 902 , the second input current Iin 2 is received by the second input end In 2 of the second DC converter 102 to generate the second output current Io 2 at the second output end O 2 of the second DC converter 102 , wherein the second input end In 2 has the second input voltage Vin 2 and the second output end O 2 has the second output voltage Vo 2 . The second DC converter 102 is electrically coupled to the second energy storing element Csc 2 .

In step 903 , the voltage difference adjusting signal Vdiff is generated by the voltage difference adjusting unit 104 which is electrically coupled to the first DC converter 100 and the second DC converter 102 . For example, Vdiff may be equal or corresponding to Vsc 1 minus Vsc 2 for the second converter in FIG. 1 .

In step 904 , the first control signal Icon 1 is generated to control the first DC converter 100 by the first control unit 106 . For example, Icon 1 may be equal or corresponding to Iref minus Io 1 .

In step 905 , the second control signal Icon 2 is generated by the second control unit 108 to control the second DC converter 102 according to the voltage difference adjusting signal Vdiff. For example, Vref may be equal to Vdiff plus Vin/2, and Icon 2 may be equal to or corresponding to Vin 2 minus Vref.

Although the present invention has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.

It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims.