KR102614055B1 - DC-DC Converter with Flying Capacitor And Method for Compensating Voltage of Flying Capacitor therefor - Google Patents

Abstract

A DC-DC converter with a flying capacitor and a flying capacitor voltage compensation method therefor are disclosed.
According to one aspect of the present disclosure, a buck converter unit that steps down or bypasses the input power; and a boost converter unit that boosts or bypasses the power applied from the buck converter unit and outputs the buck converter unit and the boost converter unit, each including a flying capacitor and one inductor. Provides a direct current-direct current converter characterized by sharing.

Description

DC-DC Converter with Flying Capacitor And Method for Compensating Voltage of Flying Capacitor therefor}

The present disclosure relates to a direct current-direct current converter having a flying capacitor and a flying capacitor voltage compensation method therefor.

The content described in this section simply provides background information about the present invention and does not constitute prior art.

1A and 1B are circuit diagrams schematically showing a conventional three-level flying capacitor DC-DC converter. In a 3-level flying capacitor DC-DC converter, the voltage between both ends of the flying capacitor (C _FL or C _FH ) is controlled to be half of the input voltage (V _L ) or output voltage (V _H ). This has the effect of reducing inductor current ripple and output voltage ripple. In addition, the voltage applied to both ends of the switch is half of the input voltage (V _L ) or output voltage (V _H ), so the input voltage (V _L ) or output voltage (V _H ) is twice as high as the voltage that the switch can withstand. There is an advantage in being able to use .

Meanwhile, the DC-DC converter 10 shown in FIG. 1A is a buck converter, a step-down converter, and can be used only under the condition that the output voltage (V _O ) is lower than the input voltage (V _L ). . In addition, the DC-DC converter 12 shown in FIG. 1B is a boost converter, which is a step-up converter, and can be used only under the condition that the output voltage (V _H ) is higher than the input voltage ( _VO ). do.

That is, the conventional buck converter 10 and boost converter 12 require a wide input voltage range and a wide output voltage range, so they have the disadvantage of being difficult to use when the output voltage is both greater or less than the input voltage.

The main purpose of the present disclosure is to provide a DC-DC converter capable of both step-up and step-down operations depending on the required input voltage range and output voltage range while using a flying capacitor, and a flying capacitor voltage compensation method for the same.

Furthermore, the main purpose of the present disclosure is to provide a DC-DC converter that can be driven efficiently by minimizing switching while maintaining the voltage across the flying capacitor constant, and a flying capacitor voltage compensation method therefor.

Furthermore, the main purpose of the present disclosure is to provide a DC-DC converter capable of maintaining the voltage across the flying capacitor constant even if there is an offset in the current measurement value, and a flying capacitor voltage compensation method for the same.

According to one aspect of the present disclosure, a buck converter unit that steps down or bypasses the input power; and a boost converter unit that boosts or bypasses the power applied from the buck converter unit and outputs the buck converter unit and the boost converter unit, each including a flying capacitor and one inductor. Provides a direct current-direct current converter characterized by sharing.

According to another aspect of the present disclosure, there is provided a method of compensating the flying capacitor voltage of a converter that includes a flying capacitor, a plurality of switches, and an inductor and is driven to bypass an input voltage, based on a preselected first compensation mode. , a first switching process of selectively switching some of the plurality of switches to form a path for charging or discharging the flying capacitor; and determining whether to maintain the first compensation mode based on the amount of change in voltage of the flying capacitor.

As described above, according to the embodiment of the present disclosure, both step-up and step-down operations are possible depending on the required input voltage range and output voltage range while using a flying capacitor.

Furthermore, according to an embodiment of the present disclosure, efficient driving is possible by minimizing switching, and the voltage across the flying capacitor can be kept constant.

Furthermore, according to an embodiment of the present disclosure, the voltage across the flying capacitor can be kept constant even if there is an offset in the current measurement value.

1A and 1B are circuit diagrams schematically showing a conventional 3-level flying capacitor DC-DC converter.
Figure 2 is a schematic configuration diagram of a DC-DC converter according to an embodiment of the present disclosure.
3A and 3B are exemplary diagrams for explaining the bypass state of the buck converter unit and the boost converter unit according to an embodiment of the present disclosure.
4A and 4B are exemplary diagrams for explaining the voltage compensation mode of the buck flying capacitor according to an embodiment of the present disclosure.
5A and 5B are exemplary diagrams for explaining a voltage compensation mode of a boost flying capacitor according to an embodiment of the present disclosure.
Figure 6 is a block diagram schematically showing a control unit according to an embodiment of the present disclosure.
7A and 7B are flowcharts showing a flying capacitor voltage compensation method according to an embodiment of the present disclosure.
Figure 8 is an exemplary diagram showing an operation waveform according to flying capacitor voltage compensation according to an embodiment of the present disclosure.

Hereinafter, some embodiments of the present disclosure will be described in detail through illustrative drawings. When adding reference numerals to components in each drawing, it should be noted that identical components are given the same reference numerals as much as possible even if they are shown in different drawings. Additionally, in describing the present disclosure, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present disclosure, the detailed description will be omitted.

Additionally, in describing the components of the present disclosure, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the nature, sequence, or order of the component is not limited by the term. Throughout the specification, when a part is said to 'include' or 'have' a certain component, this means that it does not exclude other components but may further include other components, unless specifically stated to the contrary. . In addition, ‘…’ stated in the specification. Terms such as 'unit' and 'module' refer to a unit that processes at least one function or operation, and may be implemented as hardware, software, or a combination of hardware and software.

Figure 2 is a schematic configuration diagram of a DC-DC converter according to an embodiment of the present disclosure.

As shown in FIG. 2, a direct current-direct current converter (dc-dc converter, 20) according to an embodiment of the present disclosure includes an input unit 200, a buck converter unit 210, a boost converter unit 220, and an output unit. It includes all or part of 230 and control unit 240.

The buck converter unit 210 according to an embodiment of the present disclosure can step down or bypass the voltage input from the input unit 200 and transmit it to the boost converter unit 220, and the boost converter unit 220 The voltage transmitted from the buck converter unit 210 may be boosted or bypassed and transmitted to the output unit 230.

To this end, the buck converter unit 210 and the boost converter unit 220 may include a plurality of switches, inductors, and flying capacitors. Here, each of the plurality of switches may be implemented as a transistor.

The buck converter unit 210 and the boost converter unit 220 may be configured to share one inductor (L _B ). Accordingly, the DC-DC converter 20 according to an embodiment of the present disclosure can save one inductor and two capacitors compared to a structure that simply combines the conventional buck converter 10 and boost converter 12.

Hereinafter, when it is necessary to distinguish between the buck converter unit 210 and the boost converter unit 220, the switch and the flying capacitor included in the buck converter unit 210 are referred to as the buck switch and the buck flying capacitor, and the boost converter unit ( The switch and flying capacitor included in 220) are referred to as the boost switch and boost flying capacitor.

The buck converter unit 210 may include first to fourth buck switches (S _L1 to S _L4 ), a buck flying capacitor (C _FL ), and an inductor (L _B ).

The first to fourth buck switches (S _L1 to S _L4 ) are connected in series with each other, and the buck flying capacitor (C _FL ) is a series connection circuit of the second buck switch (S _L2 ) and the third buck switch (S _L3 ). It can be configured to be connected in parallel.

Specifically, one end of the first buck switch (S _L1 ) is connected to one end of the input unit 200, and the other end is connected to one end of the buck flying capacitor (C _FL ). One end of the second buck switch (S _L2 ) is connected to the contact point of the first buck switch (S _L1 ) and the buck flying capacitor (C _FL ), and the other end is connected to one end of the inductor (L _B ). One end of the third buck switch (S _L3 ) is connected to the contact point of the second buck switch (S _L2 ) and the inductor (L _B ), and the other end is connected to the other end of the buck flying capacitor (C _FL ). One end of the fourth buck switch (S _L4 ) is connected to the contact point of the third buck switch (S _L3 ) and the buck flying capacitor (C _FL ), and the other end is connected to the other end of the input unit 200.

The boost converter unit 220 may include first to fourth boost switches (S _H1 to S _H4 ), a boost flying capacitor (C _FH ), and an inductor (L _B ).

The first to fourth boost switches (S _H1 to S _H4 ) are connected in series with each other, and the boost flying capacitor (C _FH ) is a series connection circuit of the second boost switch (S _H2 ) and the third boost switch (S _H3 ). It can be configured to be connected in parallel.

Specifically, one end of the first boost switch (S _H1 ) is connected to one end of the output unit 230, and the other end is connected to one end of the boost flying capacitor (C _FH ). One end of the second boost switch (S _H2 ) is connected to the contact point of the first boost switch (S _H1 ) and the boost flying capacitor (C _FH ), and the other end is connected to the other end of the inductor (L _B ). One end of the third boost switch (S _H3 ) is connected to the contact point of the second boost switch (S _H2 ) and the inductor (L _B ), and the other end is connected to the other end of the boost flying capacitor (C _FH ). One end of the fourth boost switch (S _H4 ) is connected to the contact point of the third boost switch (S _H3 ) and the boost flying capacitor (C _FH ), and the other end is connected to the other end of the output unit 230.

The control unit 240 provides control signals (Q L1 to Q L4 ) and first to fourth buck switches (S _L1 to S _L4 ) that turn on or off the first to fourth buck switches (S _L1 to S _L4 ), respectively. Generates control signals (Q _H1 to Q _H4 ) that conduct or block the boost switches (S _H1 to S _H4 ), respectively.

The control unit 240 may switch the first and fourth buck switches (S _L1 and S _L4 ) complementary to each other, and switch the second and third buck switches (S _L2 and S _L3 ) in a complementary manner. . The control unit 240 may switch the first and fourth buck switches (S _L1 and S _L4 ) and the second and third buck switches (S _L2 and S _L3 ) so that they have a phase difference of 180 degrees.

Likewise, the control unit 240 switches the first and fourth boost switches (S _H1 and SH _H4 ) complementary to each other, and switches the second and third boost switches (S _H2 and SH _H3 ) complementary to each other. can do. The control unit 240 may switch the first and fourth boost switches (S _H1 and S _H4 ) and the second and third boost switches (S _H2 and S _H3 ) to have a phase difference of 180 degrees.

Through the above structure, the DC-DC converter 20 according to an embodiment of the present disclosure satisfies the voltage transfer ratio of Equation 1.

Here, V _L is the input voltage, V _H is the output voltage, D _L is the duty ratio of the buck converter unit 210, and D _H is the duty ratio of the boost converter unit 220.

According to an embodiment of the present disclosure, the duty ratio (D _L ) of the buck converter unit 210 and/or the duty ratio of the boost converter unit ₂₂₀ according to the conditions of the input voltage (V _L ) and the output voltage (V H ). By adjusting (D _H ), the DC-DC converter 20 can be operated in a step-up mode or a step-down mode. At this time, it may be inefficient to periodically switch both the buck converter unit 210 and the boost converter unit 220 to boost or step down the input voltage (VL) to the output voltage (VH). Therefore, the DC-DC converter 20 according to an embodiment of the present disclosure is one of the buck converter unit 210 and the boost converter unit 220 according to the conditions of the input voltage (V _L ) and output voltage (V _H ). You can bypass one and switch only the others.

3A and 3B are exemplary diagrams for explaining the bypass state of the buck converter unit and the boost converter unit according to an embodiment of the present disclosure.

According to an embodiment of the present disclosure, when the required output voltage (V _H ) is greater than the input voltage (V _L ), that is, when the DC-DC converter 20 is operated in a boost mode, the buck converter unit 210 By bypassing , the input voltage (V _L ) can be transmitted to the boost converter unit 220. To this end, some of the first to fourth buck switches (S _L1 to S _L4 ) may be selectively switched.

To be described in more detail with reference to FIG. 3A, in the boost mode, the control unit 240 turns on the first buck switch (S _L1 ) and the second buck switch (S _L2 ) and turns on the third buck switch (S _L3 ) And the fourth buck switch (S _L4 ) is turned off, so that the input voltage (V _L ) can be transmitted to the boost converter unit 220. In other words, in the boost mode, the duty ratio (D _L ) of the buck converter unit 210 is set to 1, and thus the DC-DC converter 20 satisfies the voltage transfer ratio of Equation 2.

Likewise, when the required output voltage (V _H ) is smaller than the input voltage (V _L ), that is, when the DC-DC converter 20 is operated in step-down mode, the boost converter unit 220 is bypassed, thereby converting the buck converter. The voltage applied from the unit 210 may be transmitted to the output unit 230. To this end, some of the first to fourth boost switches S _H1 to S _H4 may be selectively switched.

To be described in more detail with reference to FIG. 3B, in the step-down mode, the control unit 240 turns on the first boost switch (S _H1 ) and the second boost switch (S _H2 ), and turns on the third boost switch (S H3) and the fourth boost switch (S _H3 ). By turning off the boost switch (S _H4 ), the voltage applied from the buck converter unit 220 can be transmitted to the output unit 230. In other words, in the step-down mode, the duty ratio (D _H ) of the boost converter unit 220 is set to 0, and thus the DC-DC converter 20 satisfies the voltage transfer ratio of Equation 3.

Meanwhile, for normal operation of the buck converter unit 210 including the buck flying capacitor (C _FL ), the voltage (V _FL ) across the buck flying capacitor must be maintained at half of the input voltage (V _L ). Likewise, for normal operation of the boost converter unit 220 including the boost flying capacitor (C _FH ), the voltage (V _FH ) across the boost flying capacitor must be maintained at half of the output voltage (V _H ).

However, as shown by the dotted line in FIGS. 3A and 3B, the flying capacitor (C _FL or C _FH ) on the bypassed side of the buck converter unit 210 and the boost converter unit 220 has a path that can control the voltage. (path) is not formed, but rather, discharge of the flying capacitor (C _FL or C _FH ) occurs due to the parasitic resistance component of the circuit.

Hereinafter, the voltage (V FL or V _{FH ) across the flying capacitor on the bypassed side of the buck converter unit 210 and the boost converter unit 220 is set to half of the input voltage (V L )} or output voltage (V _{H )} . Let us explain how to compensate for the flying capacitor voltage by controlling it so that it can be maintained.

Meanwhile, the switching operation of the non-bypassed side of the buck converter unit 210 and the boost converter unit 220, that is, the boost converter unit 220 when operating in the step-up mode and the buck converter unit 210 when operating in the step-down mode, and Since the flying capacitor voltage compensation method is the same or similar to the switching operation and flying capacitor voltage compensation method of the conventional boost converter 10 and buck converter 12, detailed description thereof will be omitted.

4A and 4B are exemplary diagrams for explaining the voltage compensation mode of the buck flying capacitor according to an embodiment of the present disclosure.

According to an embodiment of the present disclosure, by selectively turning on or turning off some of the first to fourth buck switches (S _L1 to S _L4 ) of the buck converter unit 210 that are in a bypass state, the buck flying capacitor (C) A path that can charge or discharge _FL ) can be formed.

Figure 4a shows the 'top compensation mode' in which the switches located at the top of the contact formed with the buck flying capacitor (C _FL ) among the first to fourth buck switches (S _L1 to S _L4 ) are turned on. To this end, the second buck switch (S _L2 ) may be turned off and the third buck switch (S _L3 ) may be turned on from the bypass state.

Figure 4b shows a 'bottom compensation mode' in which the switches located at the bottom of the contact formed with the buck flying capacitor (C _FL ) among the first to fourth buck switches (S _L1 to S _L4 ) are turned on. To this end, the first buck switch (S _L1 ) may be turned off and the fourth buck switch (S _L4 ) may be turned on from the bypass state.

The buck flying capacitor (C _FL ) is charged or discharged depending on the compensation mode and direction of the inductor current (I _L ). For example, in the top compensation mode, when the inductor current (I _L ) flows in the direction of the boost converter unit 220, the buck flying capacitor (C _FL ) is charged, and the inductor current flows in the direction of the buck converter unit 210. In this case, the buck flying capacitor (C _FL ) is discharged. Likewise, in the bottom compensation mode, when the inductor current (I _L ) flows in the direction of the boost converter unit 220, the buck flying capacitor (C _FL ) is discharged, and when the inductor current flows in the direction of the buck converter unit 210, the buck flying capacitor (C FL ) is discharged. The buck flying capacitor (C _FL ) is charged.

In other words, the compensation mode that defines the switching state of the first to fourth buck switches (S _L1 to S _L4 ) will be determined according to the charging and discharging conditions of the buck flying capacitor (C _FL ) and the direction of the inductor current (I _L ). You can. When the case where the inductor current (I _L ) flows in the direction of the buck converter unit 210 is defined as the positive direction, the compensation modes for charging, discharging or maintaining the voltage of the buck capacitor (C _FL ) are summarized in Table 1. .

buck capacitor C _FL charge/discharge condition charge Discharge Maintenance (natural defense) inductor current
I _L (+) top reward bottom reward No compensation
(Bypass) (-) bottom reward top reward

Here, the uncompensated mode maintains the switching state of the first to fourth buck switches (S _L1 to S _L4 ) in the bypass state of FIG. 3A, and the buck flying capacitor (C _FL ) is affected by the parasitic resistance of the circuit, etc. is discharged naturally.

5A and 5B are exemplary diagrams for explaining a voltage compensation mode of a boost flying capacitor according to an embodiment of the present disclosure.

According to an embodiment of the present disclosure, by selectively turning on or turning off some of the first to fourth boost switches (S _H1 to S _H4 ) of the boost converter unit 220 that are in a bypass state, the boost flying capacitor (C) _FH ) can form a path that can charge or discharge.

Figure 5a shows the 'top compensation mode' in which the switches located at the top of the contact formed with the boost flying capacitor (C _FH ) among the first to fourth boost switches (S _H1 to S _H4 ) are turned on. To this end, the second boost switch (S _H2 ) may be turned off and the third boost switch (S _H3 ) may be turned on from the bypass state.

Figure 5b shows a 'bottom compensation mode' in which switches located at the bottom of the contact formed with the boost flying capacitor (C _FH ) among the first to fourth boost switches (S _H1 to S _H4 ) are turned on. To this end, the first boost switch (S _H1 ) may be turned off and the fourth boost switch (S _H4 ) may be turned on from the bypass state.

The boost flying capacitor (C _FH ) is charged or discharged depending on the compensation mode and the direction of the inductor current (I _L ). For example, in the top compensation mode, when the inductor current (I _L ) flows in the direction of the boost converter unit 220, the boost flying capacitor (C _FH ) is discharged, and the inductor current flows in the direction of the buck converter unit 210. In this case, the boost flying capacitor (C _FH ) is charged. Similarly, in the bottom compensation mode, when the inductor current (I _L ) flows in the direction of the boost converter unit 220, the boost flying capacitor (C _FH ) is charged, and when the inductor current flows in the direction of the buck converter unit 210, the boost flying capacitor (C FH ) is charged. The boost flying capacitor (C _FH ) is discharged.

In other words, the compensation mode that defines the switching state of the first to fourth boost switches (S _H1 to S _H4 ) will be determined according to the charging and discharging conditions of the boost flying capacitor (C _FH ) and the direction of the inductor current ( _IL ). You can. When the case where the inductor current (I _L ) flows in the direction of the buck converter unit 210 is defined as the positive direction, the compensation modes for charging, discharging or maintaining the voltage of the boost capacitor (C _FH ) are summarized in Table 2. .

boost capacitor C _F.H. charge/discharge condition charge Discharge Maintenance (natural defense) inductor current
I _L (+) bottom reward top reward No compensation
(Bypass) (-) top reward bottom reward

Here, the non-compensation mode maintains the switching state of the first to fourth boost switches (S _H1 to S _H4 ) in the bypass state of FIG. 3B, and the boost flying capacitor (C _FH ) is operated by the parasitic resistance of the circuit, etc. is discharged naturally.

As described above, since the compensation mode for charging or discharging the flying capacitor (C _FL or C _FH ) varies depending on the direction of the inductor current (I _L ), it is important to accurately measure the inductor current (I _L ). However, it is realistically difficult to accurately measure the inductor current (I _L ). In particular, during light load or no-load operation of the DC-DC converter 20, if the directions of the actual current (I _L ) and the measured current (I _{L_m} ) flowing in the inductor are different due to the offset of the current sensor, the compensation mode is activated. If chosen incorrectly, the voltage across the flying capacitor (V _FL or V _FH ) cannot be kept constant.

To solve this problem, in the present disclosure, even if there is an offset between the actual current (I _L ) flowing in the inductor and the measured current (I _{L_m} ), the voltage across the flying capacitor (V _FL or V _FH ) can be kept constant. suggest a method

Figure 6 is a block diagram schematically showing a control unit according to an embodiment of the present disclosure.

As shown in FIG. 6, the control unit 240 according to an embodiment of the present disclosure includes all or part of a charge/discharge determination unit 600, a compensation mode selection unit 610, and a control signal generation unit 620. . Not all components shown in FIG. 6 are essential components, and some components included in the control unit 240 may be added, changed, or deleted in other embodiments. That is, in the case of FIG. 6, when the control unit 240 according to an embodiment of the present disclosure operates in the boosting mode, the voltage across the buck flying capacitor (V _FL ) is maintained at half of the input voltage (V _L ). The first to fourth buck switches (S _L1 to S _L4 ) are controlled to control at least one of them, or to maintain the voltage across the boost flying capacitor (V _FH ) at half of the output voltage (V _H ) when operating in step-down mode. Components for controlling at least one of the boost switches (S _H1 to S _H4 ) are illustratively shown, and the control unit 240 includes more or fewer components or different components than those shown to implement other functions. It should be recognized that it may have a configuration of . For example, the control unit 240 may further include components for controlling switches of the boost converter unit 220 when operating in a step-up mode and the buck converter unit 210 when operating in a step-down mode.

The charge/discharge determination unit 600 determines charge/discharge conditions based on the voltage (V _FL ) across the buck flying capacitor or the voltage (V _FH ) across the boost flying capacitor. Here, the charging/discharging conditions may be determined as one of charging, discharging, and maintaining. Depending on the embodiment, when discharging the flying capacitor (C _FL or C _FH ) using only natural discharge, the charging and discharging conditions may be determined as either charging or maintaining.

When the DC-DC converter 20 operates in the boost mode, the charge/discharge determination unit 600 may determine charge/discharge conditions based on the voltage (V _FL ) across the buck flying capacitor. Likewise, when the DC-DC converter 20 operates in the step-down mode, the charge/discharge determination unit 600 may determine charge/discharge conditions based on the voltage (V _FH ) across the boost flying capacitor.

For example, when the voltage (V _FL or V _FH ) across the flying capacitor is less than or equal to a preset first threshold voltage, the charge/discharge determination unit 600 may determine the charge/discharge condition to be 'charge'. Here, the preset first threshold voltage is sufficient to justify charging the flying capacitor (C _FL or C _FH ) for normal operation of the circuit when the voltage (V _FL or V _FH ) across the flying capacitor is below the corresponding voltage. It refers to the reference voltage and can be set to a value less than half of the input voltage (V _L ) or output voltage (V _H ), but is not limited to this and can be set variably.

When the voltage (V _FL or V _FH ) across the flying capacitor is greater than or equal to a preset second threshold voltage, the charge/discharge determination unit 600 may determine the charge/discharge condition to be 'discharge'. Here, the preset second threshold voltage refers to a reference voltage that has sufficient justification for discharging the flying capacitor (C _FL or C _FH ) when the voltage across the flying capacitor (V _FL or V _FH ) is higher than the corresponding voltage, It may be set to a value of more than half of the input voltage (V _L ) or output voltage (V _H ), but is not limited to this and may be set variably.

When the voltage (V _FL or V _FH ) across the flying capacitor is greater than the preset first threshold voltage and less than the preset second threshold voltage, the charge/discharge decision unit 600 may determine the charge/discharge condition to be 'maintained'. . According to embodiments, when discharging the flying capacitor (C _FL or C _FH ) using only natural discharge, the charge/discharge determination unit 600 determines that the voltage (V _FL or V _FH ) across the flying capacitor is set to a preset value. 1 If it is greater than the threshold voltage, the charging/discharging condition can be determined to be 'maintained'.

The compensation mode selection unit 610 determines the compensation mode based on the charging and discharging conditions and the inductor measurement current (I _{L_m} ).

The operation of the compensation mode selection unit 610 is largely performed when the size of the inductor measurement current (I _{L_m} ) is greater than or equal to the preset threshold current (I _SAT ) and when the size of the inductor measurement current (I _{L_m} ) is greater than or equal to the preset threshold current (I _SAT) . ) can be classified into cases that are smaller than ). Here, the preset threshold current (I _SAT ) is the minimum value at which the offset of the current sensor can be ignored, and can be set variably depending on the implementation.

First, if the size of the inductor measurement current (I _{L_m} ) is greater than the preset threshold current (I _SAT ), that is, if the size of the inductor measurement current (I _{L_m} ) is large enough to not be affected by the offset, the inductor It can be ensured that the directions of the actual flowing current (I _L ) and the inductor measurement current (I _{L_m} ) match. Therefore, the compensation mode selection unit 610 assumes that the direction of the current (I _L ) actually flowing in the inductor is in the same direction as the inductor measurement current (I _{L_m} ), and as shown in Table 1 or Table 2, the charging and discharging conditions and the inductor You can select a compensation mode according to the direction of the current (I _L ).

On the other hand, if the size of the inductor measurement current (I _{L_m} ) is smaller than the preset threshold current (I _SAT ), it is guaranteed that the direction of the current (I _L ) actually flowing in the inductor and the inductor measurement current (I _{L_m} ) match. I can't. Even in this case, in order to compensate for the voltage of the flying capacitor (C _FL or C _FH ), the compensation mode selection unit 610 selects the compensation mode based on the direction of the inductor measurement current (I _{L_m} ) or the inductor measurement current. It can be determined whether to select the compensation mode based on the reverse direction of the current (I _{L_m} ).

In the present disclosure, 'compensation polarity' can be used to define a reference direction for selecting a compensation mode. For example, when the compensation polarity is a positive value, the compensation mode selection unit 610 may select the compensation mode based on the direction of the inductor measurement current (I _{L_m} ). On the other hand, when the compensation polarity is a negative value, the compensation mode selection unit 610 may select the compensation mode based on the reverse direction of the inductor measurement current (I _{L_m} ).

The compensation mode selection unit 610 determines whether to maintain the preselected compensation mode during the next compensation or to change the compensation mode based on the amount of change in the voltage (V _FL or V _FH ) across the flying capacitor during the _preset time (T SET). You can decide whether to choose it again.

Here, the amount of change in the voltage across the flying capacitor (V _FL or V _FH ) is the voltage across the flying capacitor before changing the switching state (V _FL or V _FH ) and the preset time (T It can mean the difference between the voltage (V _FL or V _FH ) across the flying capacitor after _SET ) has passed. The preset time (T _SET ) is a period for performing voltage compensation across the flying capacitor in the bypass state, and is the operating frequency of the DC-DC converter 20 or the voltage (V) across the flying capacitor during charging, discharging and/or natural discharge. It can be set variably by considering the amount of change in _FL or V _FH ).

The compensation mode selection unit 610 determines whether the preselected compensation mode meets the charging and discharging conditions based on the amount of change in the voltage (V _FL or V _FH ) across the flying capacitor. If it is determined that it does not meet the charging and discharging conditions, the compensation mode selector 610 switches the compensation mode again. You can choose.

The compensation mode selection unit 610 determines whether the preselected compensation mode meets the charge and discharge conditions based on whether the flying capacitor (C _FL or C _FH ) is charged or discharged according to the charge and discharge conditions by the preselected compensation mode. can do.

For example, when the charging/discharging condition is charging, the compensation mode selection unit 610 may determine whether the flying capacitor (C _FL or C _FH ) is charged by the pre-selected compensation mode. The compensation mode selection unit 610 maintains the preselected compensation mode when it is determined that the flying capacitor (C _FL or C _FH ) is charged, and when it is determined that the flying capacitor (C _FL or C _FH ) is not charged, the inductor measurement Based on the current (I _{L_m} ), the compensation mode that causes the flying capacitor (C _FL or C _FH ) to be discharged can be selected again.

Similarly, when the charge/discharge condition is discharge, the compensation mode selection unit 610 may determine whether the flying capacitor (C _FL or C _FH ) is discharged by the pre-selected compensation mode. The compensation mode selection unit 610 maintains the preselected compensation mode when it is determined that the flying capacitor (C _FL or C _FH ) is discharged, and when it is determined that the flying capacitor (C _FL or C _FH ) is not discharged, the inductor measurement is performed. Based on the current (I _{L_m} ), the compensation mode that allows the flying capacitor (C _FL or C _FH ) to be charged can be selected again.

In order to re-select the compensation mode that meets the charging and discharging conditions, the compensation mode selection unit 610 may change the reference direction for selecting the compensation mode. For example, when the reference direction of the pre-selected compensation mode is the direction of the inductor measurement current (I _{L_m} ), the compensation mode selection unit 610 selects a compensation mode suitable for the charging and discharging conditions based on the reverse direction of the inductor measurement current (I _{L_m} ). You can reselect. Similarly, when the reference direction of the preselected compensation mode is the reverse direction of the inductor measurement current (I _{L_m} ), the compensation mode selection unit 610 selects a compensation mode suitable for the charging and discharging conditions based on the direction of the inductor measurement current (I _{L_m} ). You can reselect.

The specific operation of the compensation mode selection unit 610 will be described later with reference to FIGS. 7A, 7B, and 8.

The control signal generator 620 generates control signals (Q _L1 to Q _L4 ) and/or first to selectively turn on or turn off the first to fourth buck switches (S _L1 to S _L4 ) according to the selected compensation mode. To generate control signals (Q _H1 to Q _H4 ) that selectively turn on or turn off the fourth boost switches (S _H1 to S _H4 ).

For example, when the upper compensation mode is selected during the step-up mode operation of the DC-DC converter 20, the control signal generator 620 maintains the existing switching state of the first and fourth buck switches (S _L1 and S _L4 ). The second buck switch (S _L2 ) is turned off and the third buck switch (S _L3 ) is turned on, thereby generating control signals (Q _L1 to Q _L4 ). Conversely, when the lower compensation mode is selected during the step-up mode operation of the DC-DC converter 20, the control signal generator 620 maintains the existing switching state of the second and third buck switches (S _L2 and S _L3 ). And, the first buck switch (S _L1 ) is turned off and the fourth buck switch (S _L4 ) is turned on, thereby generating control signals (Q _L1 to Q _L4 ).

Likewise, when the upper compensation mode is selected during the step-down mode operation of the DC-DC converter 20, the control signal generator 620 maintains the existing switching state of the first and fourth boost switches S _H1 and S _H4 , the second boost switch (S _H2 ) is turned off, and the third boost switch (S _H3 ) can generate control signals (Q _H1 to Q _H4 ) that are turned on. Conversely, when the lower compensation mode is selected during the step-down mode operation of the DC-DC converter 20, the control signal generator 620 maintains the existing switching state of the second and third buck switches (S _H2 and S _H3 ). And, the first boost switch (S _H1 ) can be turned off and the fourth boost switch (S _H4 ) can generate control signals (Q _H1 to Q _H4 ) that are turned on.

7A and 7B are flowcharts showing a flying capacitor voltage compensation method according to an embodiment of the present disclosure.

FIGS. 7A and 7B illustrate a process of compensating the voltage (V _FL ) across the buck flying capacitor when the DC-DC converter 20 operates in a boost mode, but the present disclosure is not limited thereto. That is, the compensation method of FIGS. 7A and 7B can be similarly extended to the process of compensating the voltage (V _FH ) across the boost flying capacitor when the DC-DC converter 20 is operated in step-down mode.

The compensation mode selection unit 610 checks whether a preset time (T _SET ) has elapsed after compensating the flying capacitor voltage (S700). Depending on the embodiment, the compensation mode selection unit 610 may be provided with a timer (not shown) and may increase the timer value until it becomes the same as the timer value corresponding to the preset time (S702).

When the preset time (T _SET ) has elapsed, the compensation mode selection unit 610 checks whether the size of the inductor measurement current (I _{L_m} ) is smaller than the preset threshold current (I _SAT ) (S704).

When the size of the inductor measurement current (I _{L_m} ) is greater than or equal to the preset threshold current (I _SAT ), the compensation mode selection unit 610 determines the charging/discharging condition (Flag _char ) based on the direction of the inductor measurement current (I _{L_m} ). Select compensation mode (Comp) (S706).

When the size of the inductor measurement current (I _{L_m} ) is smaller than the preset threshold current (I _SAT ), the compensation mode selection unit 610 calculates the amount of change (V _comp ) in the voltage across the flying capacitor (V _FL ) (S710) . The amount of change (V _comp ) in the voltage across the flying capacitor (V _FL ) is the current voltage across the flying capacitor (V _FL ) and the voltage across the flying capacitor (V _buff ) can be defined as the difference between Accordingly, the amount of change (V _comp ) in the voltage across the flying capacitor (V _FL ) includes the charging or discharging of the flying capacitor (C _FL ) by the preselected compensation mode, and the flying capacitor (C _FL ) for a preset time (T _SET ). )'s natural discharge can be reflected.

The compensation mode selection unit 610 checks the charging and discharging conditions (Flag _char ) (S720 and S722).

When the charging/discharging condition is charging, the compensation mode selection unit 610 selects a preselected voltage based on whether the amount of change (V _comp ) in the voltage across the flying capacitor (V _FL ) is less than the preset first comparison voltage (-V _SET ). It is possible to determine whether to maintain the compensation mode (S730). The preset first comparison voltage (-V _SET ) is a value for determining whether the flying capacitor (C _FL ) has been charged by the preselected compensation mode, and the flying capacitor (C _FL ) during the preset time (T _SET ) It can be set considering natural discharge.

When the charge/discharge condition is discharge, the compensation mode selection unit 610 selects the preselected compensation based on whether the amount of change (V _comp ) in the voltage across the flying capacitor (V _FL ) is greater than the preset second comparison voltage (V _SET ). It is possible to determine whether to maintain the mode (S732). The preset second comparison voltage (V _SET ) is a value for determining whether the flying capacitor (C _FL ) is discharged by the preselected compensation mode, and is the value of the flying capacitor (C _FL ) during the preset time (T _SET ). It can be set considering natural discharge. Meanwhile, in FIG. 7A, the first comparison voltage and the second comparison voltage are shown as having the same absolute value. However, this is only an example, and the first comparison voltage and the second comparison voltage may be set independently.

If the charging/discharging condition is charging and the amount of change (V _comp ) in the voltage (V _FL ) across the flying capacitor is higher than the preset first comparison voltage (-V _SET ), the flying capacitor (C _FL ) is charged according to the pre-selected compensation mode. Therefore, the compensation mode selection unit 610 maintains the pre-selected compensation mode (S736). Similarly, when the charging/discharging condition is discharge and the change amount (V _comp ) in the voltage (V _FL ) across the flying capacitor is less than or equal to the preset second comparison voltage (VSET), the flying capacitor (C _FL ) is discharged by the pre-selected compensation mode. Therefore, the compensation mode selection unit 610 maintains the pre-selected compensation mode (S742). At this time, the compensation polarity may be determined to be '0' (S734).

If the charging/discharging condition is charging and the change in voltage (V _FL ) across the flying capacitor (V _comp ) is smaller than the preset first comparison voltage (-V _SET ), the flying capacitor (C _FL ) is Since the battery is discharged, reselect compensation mode. Likewise, if the charging/discharging condition is discharge and the change in voltage (V _FL ) across the flying capacitor (V _comp ) is greater than the preset second comparison voltage (V _SET ), the flying capacitor (C _FL ) is charged by the pre-selected compensation mode. Since has been charged, reselect compensation mode.

To this end, the compensation mode selection unit 610 may change the compensation polarity (S740 to S747) and reselect the compensation mode based on the changed compensation polarity (S750 to S758). At this time, the compensation mode selection unit 610 selects the compensation mode based on the positive direction of the inductor measurement current (I _{L_m} ) when the changed compensation polarity has a positive value, and when the changed compensation polarity has a negative value, the inductor measurement current Compensation mode can be selected based on the reverse direction of (I _{L_m} ). Here, selecting the compensation mode based on the reverse direction of the inductor measurement current (I _{L_m} ) means selecting the remaining compensation modes other than the compensation mode selected based on the forward direction of the inductor measurement current (I _{L_m} ) among the upper compensation mode and the lower compensation mode. It can mean making a choice.

At this time, the absolute value of the compensation polarity may be determined based on charging and discharging conditions. For example, if the charge/discharge condition is charging, the absolute value of the compensation polarity can be set to '1' (S741 and S742), and if the charge/discharge condition is discharge, the absolute value of the compensation polarity can be set to '2' (S746 and S742). S748).

Meanwhile, when the charging and discharging conditions are changed, the compensation mode selection unit 610 can set the compensation polarity to have a positive value (S742 and S747). Accordingly, the compensation mode selection unit 610 may select the compensation mode based on the forward direction of the inductor measurement current (I _{L_m} ) when selecting the first compensation mode after changing the charging and discharging conditions.

When the charging/discharging condition is charging and the changed compensation polarity is a positive value (i.e., 1), the compensation mode selection unit 610 selects the upper compensation mode when the value of the inductor measurement current (I _{L_m} ) is greater than 0, and performs the inductor measurement. If the value of the current (I _{L_m} ) is less than 0, the lower compensation mode is selected (S754 to S756).

On the other hand, when the charging/discharging condition is charging and the changed compensation polarity is a negative value (i.e., -1), the compensation mode selection unit 610 selects the lower compensation mode when the value of the inductor measurement current (I _{L_m} ) is greater than 0 and , if the value of the inductor measurement current (I _{L_m} ) is less than 0, select the upper compensation mode (S750 to S754).

When the charging/discharging condition is discharge and the changed compensation polarity is a positive value (i.e., 2), the compensation mode selection unit 610 selects the lower compensation mode when the value of the inductor measurement current (I _{L_m} ) is greater than 0, and inductor measurement If the value of the current (I _{L_m} ) is less than 0, the upper compensation mode is selected (S750 to S754).

On the other hand, when the charge/discharge condition is discharge and the changed compensation polarity is a negative value (i.e., -2), the compensation mode selection unit 610 selects the upper compensation mode when the value of the inductor measurement current (I _{L_m} ) is greater than 0. , if the value of the inductor measurement current (I _{L_m} ) is less than 0, select the lower compensation mode (S754 to S756).

Meanwhile, if the charge/discharge condition is maintained, the compensation mode selection unit 610 selects the non-compensation mode (S760).

The compensation mode selection unit 610 initializes the timer value and stores the voltage across the flying capacitor (V _FL ), compensation mode (Comp), and compensation polarity (Pole) (S770).

The control signal generator 620 generates a control signal that selectively turns on or off some of the switches based on the selected compensation mode (S780). When the upper compensation mode or lower compensation mode is selected, the flying capacitor (C _FL ) is charged or discharged. Thereafter, the control signal generator 620 may generate a control signal to selectively turn on or off some of the switches so that the buck converter 110 returns to the bypass state.

Processes S700 to S780 shown in FIGS. 7A and 7B may be performed repeatedly. Accordingly, one compensation mode among top compensation (Top_Comp), bottom compensation (Bot_Comp), and no compensation (No_Comp) can be selected at a preset time (T _SET ) interval, and switching according to the selected compensation mode can be performed. there is.

In FIGS. 7A and 7B, each process is described as being sequentially executed, but this is merely an illustrative explanation of the technical idea of an embodiment of the present disclosure. In other words, a person of ordinary skill in the technical field to which an embodiment of the present disclosure pertains may change the order shown in FIGS. 7A and 7B or perform one of the processes without departing from the essential characteristics of the embodiment of the present disclosure. Since various modifications and variations can be applied by executing one or more processes in parallel, FIGS. 7A and 7B are not limited to the time series order.

Figure 8 is an exemplary diagram showing an operation waveform according to flying capacitor voltage compensation according to an embodiment of the present disclosure.

Figure 8 shows the actual (or ideal) voltage 800 and measured voltage 810 of the buck flying capacitor, half of the input voltage 820, compensation mode 830, and inductor current 840.

The charging and discharging conditions are determined based on the measured voltage 810 of the buck flying capacitor and half of the input voltage 820.

Under charging conditions, the compensation mode 830 is determined at every preset time (T _SET ), and accordingly, the buck flying capacitor (C _FL ) is charged or discharged at every preset time (T _SET ). After the buck flying capacitor is charged or discharged, the buck converter unit 210 is switched to a bypass state (uncompensated mode), and the switching state is maintained before the next compensation is made, that is, until a preset time (T _SET ) elapses. maintain. At this time, the buck flying capacitor (C _FL ) is naturally discharged due to parasitic resistance components of the circuit.

The DC-DC converter 20 according to an embodiment of the present disclosure may determine whether the preselected compensation mode is suitable for the current charging and discharging conditions based on the amount of change in the measured voltage 810 of the buck flying capacitor. As shown in FIG. 8, the measured voltage 810 of the buck flying capacitor may appear as filtering applied to the actual voltage 800.

Figure 8 shows that, at the beginning of compensation mode selection, the buck flying capacitor (C _FL ) was actually charged by the upper compensation mode, but the measured voltage 810 of the buck flying capacitor tended to decrease, so the next compensation mode was lower compensation mode. Shows the case where the mode is changed. Accordingly, the lower compensation mode and the upper compensation mode are alternately selected. However, after a certain period of time, when the buck flying capacitor (C _FL ) is charged by the upper compensation mode, the measured voltage 810 of the buck flying capacitor tends to increase, and finally, a compensation mode suitable for the charging conditions (i.e. You can go to the compensation mode at the top.

Various implementations of the systems and techniques described herein may include digital electronic circuits, integrated circuits, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), computer hardware, firmware, software, and/or these. It can be realized through combination. These various implementations may include being implemented as one or more computer programs executable on a programmable system. The programmable system includes at least one programmable processor (which may be a special purpose processor) coupled to receive data and instructions from and transmit data and instructions to a storage system, at least one input device, and at least one output device. or may be a general-purpose processor). Computer programs (also known as programs, software, software applications or code) contain instructions for a programmable processor and are stored on a "computer-readable recording medium."

Computer-readable recording media include all types of recording devices that store data that can be read by a computer system. These computer-readable recording media are non-volatile or non-transitory such as ROM, CD-ROM, magnetic tape, floppy disk, memory card, hard disk, magneto-optical disk, and storage device. It may be a medium, and may further include a transitory medium such as a data transmission medium. Additionally, the computer-readable recording medium may be distributed in a computer system connected to a network, and computer-readable code may be stored and executed in a distributed manner.

Various implementations of the systems and techniques described herein can be implemented by a programmable computer. Here, the computer includes a programmable processor, a data storage system (including volatile memory, non-volatile memory, or another type of storage system, or a combination thereof), and at least one communication interface. For example, a programmable computer may be one of a server, network device, set-top box, embedded device, computer expansion module, personal computer, laptop, personal data assistant (PDA), cloud computing system, or mobile device.

The above description is merely an illustrative explanation of the technical idea of the present embodiment, and those skilled in the art will be able to make various modifications and variations without departing from the essential characteristics of the present embodiment. Accordingly, the present embodiments are not intended to limit the technical idea of the present embodiment, but rather to explain it, and the scope of the technical idea of the present embodiment is not limited by these examples. The scope of protection of this embodiment should be interpreted in accordance with the claims below, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of rights of this embodiment.

20: DC-DC converter
200: input unit 210: buck converter unit
220: Boost converter unit 230: Output unit
240: Control unit 600: Charge/discharge decision unit
610: Compensation selection unit 620: Control signal generation unit

Claims (16)

A buck converter unit that steps down or bypasses the input voltage;
A boost converter unit that boosts or bypasses the voltage applied from the buck converter unit and outputs it; and
A control unit that controls the target converter unit, which is one of the buck converter unit and the boost converter unit, to be selectively bypassed,
The buck converter unit and the boost converter unit, respectively,
A first switch, a second switch, a third switch, and a fourth switch connected in series; and
It includes a flying capacitor connected in parallel to the series connection circuit of the second switch and the third switch,
The buck converter unit and the boost converter unit share one inductor,
The control unit,
A non-compensation mode for maintaining the target converter unit in a bypass state, and an upper stage for compensating the voltage of the flying capacitor (hereinafter, target flying capacitor) of the target converter unit by turning on the first switch and the third switch of the target converter unit. Among the plurality of switches of the target converter unit to operate in the first compensation mode selected from among the compensation mode and the lower compensation mode in which the voltage of the target flying capacitor is compensated by turning on the second switch and the fourth switch of the target converter unit. A direct current-direct current converter characterized by selectively switching some parts and determining whether to maintain the first compensation mode based on the amount of voltage change of the target flying capacitor. delete delete According to paragraph 1,
The target converter unit,
A DC-DC converter, characterized in that it operates in a bypass state when the first switch and the second switch of the target converter unit are turned on and the third switch and the fourth switch are turned off. . delete delete According to paragraph 1,
The control unit,
If it is determined that the voltage change of the target flying capacitor due to the first compensation mode does not meet the charging and discharging conditions of the flying capacitor, the uncompensated mode, the upper compensation mode, and the lower compensation mode are used using the measured current of the inductor. A DC-DC converter characterized by selecting a second compensation mode among compensation modes. In clause 7,
The control unit,
If it is determined that the first compensation mode is not maintained,
When the first compensation mode is selected based on the forward direction of the measured current of the inductor, selecting a second compensation mode that satisfies the charging and discharging conditions of the flying capacitor based on the reverse direction of the measured current of the inductor;
When the first compensation mode is selected based on the reverse direction of the measured current of the inductor, the second compensation mode that satisfies the charging and discharging conditions of the flying capacitor is selected based on the forward direction of the measured current of the inductor. DC-DC converter. The flying capacitor of the converter is driven to bypass the applied voltage, including first to fourth switches connected in series, an inductor, and a flying capacitor connected in parallel to the series connection circuit of the second switch and the third switch. As a method of compensating for voltage,
An upper compensation mode in which the voltage of the flying capacitor is compensated by turning on the first switch and the third switch, and the voltage of the flying capacitor is compensated by turning on the second switch and the fourth switch. A first switching process of selectively switching some of the first to fourth switches to form a path for charging or discharging the flying capacitor, based on a first compensation mode selected from among the lower compensation modes; and
A process of determining whether to maintain the first compensation mode based on the amount of change in voltage of the flying capacitor.
A flying capacitor voltage compensation method comprising: According to clause 9,
The amount of change in the flying capacitor voltage is,
A flying capacitor voltage compensation method, characterized in that calculated based on the voltage of the flying capacitor after a preset time has elapsed from the first switching process and the voltage of the flying capacitor before the first switching process. According to clause 9,
The above judgment process is,
A flying capacitor voltage compensation method characterized by determining whether to maintain the first compensation mode based on whether the flying capacitor is charged or discharged by the first switching process. According to clause 11,
In the determining process, when it is determined that the flying capacitor is charged, it is determined to maintain the first compensation mode,
When it is determined that the flying capacitor is not charged, a process of selecting a second compensation mode that allows the flying capacitor to be charged from among the upper compensation mode and the lower compensation mode based on the measured current of the inductor.
A flying capacitor voltage compensation method further comprising: According to clause 11,
In the determining process, when it is determined that the flying capacitor is discharged, it is determined to maintain the first compensation mode,
When it is determined that the flying capacitor is not discharged, a process of selecting a second compensation mode that causes the flying capacitor to discharge from among the upper compensation mode and the lower compensation mode based on the measured current of the inductor.
A flying capacitor voltage compensation method further comprising: According to claim 12 or 13,
The process of selecting the second compensation mode is,
When the first compensation mode is selected based on the forward direction of the measured current of the inductor, selecting a second compensation mode that satisfies the charging and discharging conditions of the flying capacitor based on the reverse direction of the measured current of the inductor;
When the first compensation mode is selected based on the reverse direction of the measured current of the inductor, the second compensation mode that satisfies the charging and discharging conditions of the flying capacitor is selected based on the forward direction of the measured current of the inductor. Flying capacitor voltage compensation method. According to claim 12 or 13,
The process of selecting the second compensation mode is,
If the charging and discharging conditions of the flying capacitor in the first switching process and the charging and discharging conditions of the flying capacitor in the process of selecting the second compensation mode do not match, based on the forward direction of the measured current of the inductor A flying capacitor voltage compensation method characterized by selecting a second compensation mode that satisfies the charging and discharging conditions of the flying capacitor. According to claim 12 or 13,
After the first switching process,
Further comprising a second switching process of selectively switching some of the first to fourth switches so that the converter bypasses the applied voltage,
After the process of selecting the second compensation mode,
A third switching process of selectively switching some of the first to fourth switches to form a path for charging or discharging the flying capacitor, based on the selected second compensation mode.
A flying capacitor voltage compensation method further comprising:

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