DCDC converter and electronic device

Abstract

The invention provides a DC-DC converter which can appropriately adjust the charge of a capacitor with a simple structure. A DC-DC converter (10) is provided with: an output capacitor (Cout); and a first flying capacitor (Cfly1) that accumulates a charge having a voltage that is twice the voltage of the output capacitor (Cout) at the time of startup. In addition, the DC-DC converter is provided with a second flying capacitor (Cfly2) that accumulates charges having a voltage equal to the voltage of the output capacitor at the time of startup. The DC-DC converter is provided with a control circuit (100) that detects the voltage of the output capacitor and controls the charging and discharging of the first flying capacitor (Cfly1). The control circuit (100) discharges the first flying capacitor before startup, and after the discharge, charges the first flying capacitor (Cfly1) such that the voltage of the first flying capacitor becomes twice the voltage of the output capacitor.

Description

Technical Field

[0001] This disclosure relates to DC-DC converters and electronic devices. Background Technology

[0002] Previously, technologies related to DC-DC converters using switched capacitors have been proposed. Non-Patent Document 1 discloses an Always-Dual-Path Hybrid (ADPH) DC-DC converter. The DC-DC converter disclosed in Non-Patent Document 1 reduces inductor current and conduction losses by supplying output current through two paths: one from an inductor and the other from a first capacitor and the other from a second capacitor.

[0003] Non-Patent Literature 1: Katsuhiro Hatacetal, “48V-to-12V Always-Dual-Path Hybrid DC-DC Converter for Inductor Current Reduction”, 2022 IEEE Energy Conversion Congress and Exposition (ECCE), October 2022

[0004] The DC-DC converter disclosed in Non-Patent Document 1 requires the first and second capacitors to accumulate a predetermined charge before startup. Therefore, in the DC-DC converter disclosed in Non-Patent Document 1, charging and discharging sections for controlling the charge are required for the first and second capacitors respectively, which increases the circuit size or cost. Summary of the Invention

[0005] This disclosure was made in view of the problems inherent in the prior art. Moreover, the object of this disclosure is to provide a DC-DC converter that can appropriately adjust the charge of a capacitor with a simple structure.

[0006] The DC-DC converter disclosed herein converts a DC voltage from an input power supply into a specified output voltage. The DC-DC converter includes: an output capacitor that supplies output current to a load device; a first flying capacitor that stores charge via the input power supply, storing a charge equal to twice the voltage of the output capacitor upon startup; a second flying capacitor that stores charge via the input power supply, storing a charge equal to the voltage of the output capacitor upon startup; and a control circuit that detects the voltage of the output capacitor and controls the charging and discharging of the first flying capacitor. The control circuit discharges the first flying capacitor before startup and charges it after startup so that its voltage becomes twice the voltage of the output capacitor.

[0007] Another aspect of the electronic device disclosed herein includes: the aforementioned DC-DC converter; an input power supply connected to the input terminal of the DC-DC converter; and a load device connected to the output terminal of the DC-DC converter.

[0008] According to this disclosure, it is possible to provide a DC-DC converter that can appropriately adjust the charge of a capacitor with a simple structure. Attached Figure Description

[0009] Figure 1 This is a diagram showing the structure of the DC-DC converter according to the first embodiment.

[0010] Figure 2 This is a diagram used to illustrate the operation of a DC-DC converter.

[0011] Figure 3 This is a diagram used to illustrate the operation of a DC-DC converter.

[0012] Figure 4 This is a diagram used to illustrate the operation of a DC-DC converter.

[0013] Figure 5 This is a diagram used to illustrate the operation of a DC-DC converter.

[0014] Figure 6 This is a diagram showing the structure of a comparative example of a DC-DC converter.

[0015] Figure 7A This is a diagram used to illustrate the operation of a comparative example of a DC-DC converter.

[0016] Figure 7B This is a diagram used to illustrate the operation of a comparative example of a DC-DC converter.

[0017] Figure 8This is a diagram showing the structure of the DC-DC converter according to the first embodiment.

[0018] Figure 9 This is a diagram illustrating the operation of the DC-DC converter according to the first embodiment.

[0019] Figure 10 This is a diagram illustrating the operation of the DC-DC converter according to the first embodiment.

[0020] Figure 11 This is an equivalent circuit used to illustrate the operation of the DC-DC converter in the first embodiment.

[0021] Figure 12A This is a waveform diagram used to illustrate the operation of a comparative example of a DC-DC converter.

[0022] Figure 12B This is a waveform diagram used to illustrate the operation of the DC-DC converter in the first embodiment.

[0023] Figure 13 This is a diagram showing the structure of the DC-DC converter according to the second embodiment.

[0024] Figure 14 This is a diagram illustrating the operation of the DC-DC converter according to the second embodiment.

[0025] Figure 15 This is a diagram illustrating the operation of the DC-DC converter according to the second embodiment.

[0026] Figure 16 This is an equivalent circuit used to illustrate the operation of the DC-DC converter in the second embodiment.

[0027] Label Explanation

[0028] 10, 11: DC-DC converter;

[0029] 100: Control circuit;

[0030] 110: Judgment Department;

[0031] 120: V_Cout detection unit;

[0032] 130: Discharge section;

[0033] 140: Charging unit;

[0034] 150: V_Cfly1 detection department;

[0035] Cfly1: First flying capacitor;

[0036] Cfly2: Second flying capacitor;

[0037] Cfly3: Third flying capacitor;

[0038] Cout: Output capacitor;

[0039] L: Inductor;

[0040] Vin: Input terminal;

[0041] Vout: Output terminal;

[0042] GND: Ground;

[0043] Q1: First switch;

[0044] Q2: Second switch;

[0045] Q3: Third switch;

[0046] Q4: The fourth switch;

[0047] Q5: The fifth switch;

[0048] Q6: The sixth switch;

[0049] Q7: The seventh switch;

[0050] Q8: The eighth switch. Detailed Implementation

[0051] Hereinafter, several embodiments of the DC-DC converters 10 and 11 of this disclosure will be described in detail with reference to the accompanying drawings. Identical or equivalent parts of the DC-DC converters 10 and 11 in each embodiment will be labeled with the same reference numerals and their descriptions will be omitted.

[0052] (Structure of DC-DC converter 10)

[0053] Figure 1 This diagram illustrates the structure of the DC-DC converter 10 according to the first embodiment. The DC-DC converter 10 is a DC-DC converter that converts the DC voltage of the input power supply into a specified output voltage. The DC-DC converter 10 of the first embodiment is an Always-Dual-Path Hybrid (ADPH) DC-DC converter. An ADPH converter is a hybrid DC-DC converter that combines a buck converter using an inductor L and a switched capacitor.

[0054] like Figure 1 As shown, the ADPH converter has a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, and a sixth switch Q6 as multiple switching elements.

[0055] In addition, the ADPH converter uses one inductor L and two flying capacitors (first flying capacitor Cfly1 and second flying capacitor Cfly2) to achieve power conversion.

[0056] Figure 2 This is a diagram used to illustrate the operation of an ADPH type DC-DC converter. For example... Figure 2 As shown, the DC-DC converter 10 turns the group of first switch Q1, third switch Q3 and fifth switch Q5 and the group of second switch Q2, fourth switch Q4 and sixth switch Q6 on / off in opposite phase timing.

[0057] When the duty cycle of the first switch Q1, the third switch Q3, and the fifth switch Q5 is 50%, an output voltage of 1 / 4 of the input voltage is obtained. For example, if the input voltage is 48V, an output voltage of 12V is obtained. As described above, the ADPH converter can obtain the desired output voltage based on the duty cycle.

[0058] For example, in an ADPH converter, under the operating condition where power conversion is performed correctly, the capacitor voltages of the first flying capacitor Cfly1, the second flying capacitor Cfly2, and the output capacitor Cout are related by the following equation (1). Here, voltage V_Cfly1 is the voltage of the first flying capacitor Cfly1. Furthermore, voltage V_Cfly2 is the voltage of the second flying capacitor Cfly2. Furthermore, voltage V_Cout is the voltage of the output capacitor Cout.

[0059] [Formula 1]

[0060] V_Cfly1: V_Cfly2: V_Cout=2: 1: 1 ··· (1)

[0061] For example, when the output voltage Vout = 12V, the voltage V_Cfly1 = 24V and the voltage V_Cfly2 = 12V. Conversely, when the output voltage Vout = 4V, the voltage V_Cfly1 = 8V and the voltage V_Cfly2 = 4V.

[0062] The relationship between the voltages of the capacitors in the ADPH converter is expressed by the above equation (1). The ADPH converter also needs to start from this voltage ratio (2∶1∶1) during startup. That is, the ADPH converter needs to be adjusted to this voltage ratio (initial charging, pre-charging) before startup.

[0063] For example, if the voltage V_Cout of the output capacitor Cout is 4V before startup, set the voltages of the first flying capacitor Cfly1 and the second flying capacitor Cfly2 to V_Cfly1 = 8V and V_Cfly2 = 4V before startup. Alternatively, if the voltage V_Cout is 0V before startup, set the voltages of the first flying capacitor Cfly1 and the second flying capacitor Cfly2 to V_Cfly1 = 0V and V_Cfly2 = 0V before startup.

[0064] If the system starts up with different voltage ratios, a rapid movement of charge occurs between the three capacitors to make the voltage ratio 2:1:1, which will result in a large inrush current.

[0065] Figure 3 , Figure 4 as well as Figure 5 This is a diagram used to illustrate the operation of the DC-DC converter 10, and also a diagram used to illustrate the problem points of the ADPH circuit.

[0066] For example, when the capacitor voltages of the first flying capacitor Cfly1, the second flying capacitor Cfly2, and the output capacitor Cout are all zero, the system can start without problems because the voltage ratio condition (2:1:1) is met.

[0067] However, in actual circuits, even if all switches from Q1 to Q6 are open, the resistance between switches D and S is not infinitely large when open. Therefore, as... Figure 3 As shown, leakage current will be generated. Through this leakage current, such as... Figure 4 As shown, the first flying capacitor Cfly1, the second flying capacitor Cfly2, and / or the output capacitor Cout are charged.

[0068] Furthermore, there is a situation where the first flying capacitor Cfly1, the second flying capacitor Cfly2, and / or the output capacitor Cout are charged due to leakage current from FET drive circuits such as the high-side driver. Additionally, there is natural discharge based on the parasitic parallel impedance of each capacitor.

[0069] Therefore, the amount of charging and discharging varies depending on circuit conditions and time. Thus, even if the initial condition is set to 0V, the voltages V_Cfly1, V_Cfly2, and V_Cout become uncertain.

[0070] Furthermore, the case where the started ADPH converter is stopped will be explained. The output voltage V_Cout decreases after stopping, but the amount of decrease depends primarily on the load resistance RL of the load device. Additionally, regarding voltages V_Cfly1 and V_Cfly2, as mentioned above, they vary depending on factors such as charging and natural discharging based on leakage current. Therefore, the conditions that cause voltages V_Cfly1, V_Cfly2, and / or V_Cout to stop are also uncertain.

[0071] That is, the voltages V_Cfly1, V_Cfly2, and V_Cout before startup vary due to various factors, therefore... Figure 5 As shown, this will cause a deviation from the voltage ratio condition (2:1:1). Therefore, control is needed to stabilize voltages V_Cfly1, V_Cfly2, and V_Cout at the voltage ratio condition (2:1:1).

[0072] As mentioned above, the ADPH converter requires pre-charging of the three capacitors before startup so that the voltage V_Cfly1:V_Cfly2:V_Cout = 2:1:1.

[0073] However, it is undesirable to adjust the voltage of the output capacitor Cout. Since the output capacitor Cout is connected to the load device, adjusting the voltage of the output capacitor Cout (e.g., discharging it) will cause a change in the input voltage of the load device.

[0074] Depending on the load device, there are situations where even when stopped, a sharp drop in input voltage can cause malfunctions or other adverse conditions. Furthermore, since the output capacitor Cout generally has a large capacitance value, a large-scale discharge circuit is required to discharge this capacitor.

[0075] Therefore, in order to adjust the voltage ratio of each capacitor, it is preferable not to control the output capacitor Cout, but to adjust the voltage of the first flying capacitor Cfly1 and / or the second flying capacitor Cfly2.

[0076] For example, if the initial voltage V_Cout = 0V, pre-charging to voltages V_Cfly1 = 0V and V_Cfly2 = 0V satisfies the voltage ratio condition. Alternatively, if the initial voltage V_Cout = 4V, pre-charging to voltages V_Cfly1 = 8V and V_Cfly2 = 4V satisfies the voltage ratio condition.

[0077] Thus, in order to adjust the voltage ratio of each capacitor, the system needs to precharge the voltage of the first flying capacitor Cfly1 and the second flying capacitor Cfly2 before startup.

[0078] Figure 6 This is a diagram showing the structure of a comparative example of a DC-DC converter. Additionally, Figure 7A and Figure 7B This is a diagram used to illustrate the operation of a comparative example of a DC-DC converter.

[0079] like Figure 6 As shown, the DC-DC converter, as a comparative example, includes circuitry for controlling the charging and discharging of both the first flying capacitor Cfly1 and the second flying capacitor Cfly2.

[0080] right Figure 6 The operation of the comparative example shown will be explained. First, the voltage V_Cout of the output capacitor Cout is detected by the V_Cout detection unit. Next, the voltage V_Cfly1 of the first flying capacitor Cfly1 is detected by the V_Cfly1 detection unit. Furthermore, if the determination unit determines that V_Cfly1 is greater than twice the voltage V_Cout, the discharge unit 130 discharges the first flying capacitor Cfly1 to make it equal to twice the voltage V_Cout. Figure 7A ).

[0081] On the other hand, in the determination unit, when it is determined that the voltage V_Cfly1 is less than twice the voltage V_Cout, the charging unit 140 charges the first flying capacitor Cfly1 in a manner equal to twice the voltage V_Cout.

[0082] Furthermore, the voltage V_Cfly2 is detected by the V_Cfly2 detection section of the second flying capacitor Cfly2. In the determination section of the second flying capacitor Cfly2, it is determined whether the voltage V_Cfly2 is greater than the voltage V_Cout. If it is determined that the voltage V_Cfly2 is greater than the voltage V_Cout, the discharge section of the second flying capacitor Cfly2 discharges the second flying capacitor Cfly2 to make it equal to the voltage V_Cout. Figure 7B ).

[0083] On the other hand, when the determination unit of the second flying capacitor Cfly2 determines that the voltage V_Cfly2 is less than the voltage V_Cout, the charging unit of the second flying capacitor Cfly2 charges the second flying capacitor Cfly2 to make it equal to the voltage V_Cout. After that, the oscillation of the ADPH converter begins (the ADPH converter begins to output).

[0084] Thus, in Figure 6 , Figure 7A as well as Figure 7B In the comparative example shown, a determination section, a discharge section, and a charging section are respectively provided for the first flying capacitor Cfly1 and the second flying capacitor Cfly2. Therefore, the increase in circuit size or cost becomes a problem.

[0085] The DC-DC converters 10 and 11 of this embodiment realize DC-DC converters that do not have a charging section or a discharging section relative to the second flying capacitor Cfly2, and can appropriately adjust the charge of the capacitor with a simple structure.

[0086] (First Implementation)

[0087] Figure 8 This is a diagram showing the structure of the DC-DC converter 10 according to the first embodiment. The DC-DC converter 10 is configured to include an output capacitor Cout that supplies output current to a load device, a first flying capacitor Cfly1, a second flying capacitor Cfly2, an inductor L, and a control circuit 100.

[0088] In addition, the DC-DC converter 10 has multiple switching elements, including a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, and a sixth switch Q6.

[0089] The first switch Q1, the second switch Q2, and the third switch Q3 are connected in series between the input terminal Vin and the output terminal Vout of the input power supply. Furthermore, a series circuit consisting of the first flying capacitor Cfly1 and the fourth switch Q4 is connected between the connection point of the first switch Q1 and the second switch Q2 and ground GND. Additionally, a series circuit consisting of the second flying capacitor Cfly2 and the fifth switch Q5 is connected between the connection point of the second switch Q2 and the third switch Q3 and ground GND. Furthermore, a sixth switch Q6 is connected between the connection point of the second flying capacitor Cfly2 and the fifth switch Q5 and the output terminal Vout. Additionally, the output capacitor Cout is connected between the output terminal Vout and ground GND. Finally, an inductor L is connected between the connection point of the first flying capacitor Cfly1 and the fourth switch Q4 and the output terminal Vout.

[0090] The first flying capacitor Cfly1 is a flying capacitor that stores charge through the input power supply. Furthermore, upon startup, the first flying capacitor Cfly1 stores a charge equal to twice the voltage of the output capacitor Cout.

[0091] The second flying capacitor Cfly2 is a flying capacitor that accumulates charge through the input power supply. During startup, it accumulates a charge equal to the voltage of the output capacitor Cout.

[0092] The control circuit 100 includes a determination unit 110 for determining the discharge and charging of the first flying capacitor Cfly1, and a V_Cout detection unit 120 for detecting the voltage V_Cout of the output capacitor Cout. Furthermore, the control circuit 100 includes a discharge unit 130 and a charging unit 140 for the first flying capacitor Cfly1. Additionally, the control circuit 100 includes a V_Cfly1 detection unit 150 for detecting the voltage V_Cfly1 of the first flying capacitor Cfly1. The control circuit 100 detects the voltage V_Cout of the output capacitor Cout and controls the charging and discharging of the first flying capacitor Cfly1.

[0093] The control circuit 100 of the DC-DC converter 10 in the first embodiment differs from the one described above in that it does not include a charging section and a discharging section for the second flying capacitor Cfly2. Figure 6 The DC-DC converters shown in the comparative examples are different.

[0094] Figure 9 and Figure 10 This diagram illustrates the operation of the DC-DC converter 10 according to the first embodiment. Before startup, with the input terminal Vin in the applied state and all switching elements open, the detection of the voltage V_Cout of the output capacitor Cout begins. Figure 9 (1) to (5)). Next, the first flying capacitor Cfly1 is discharged ( Figure 9 (2)). In Figure 10 The diagram illustrates a short circuit caused by resistance.

[0095] Then, the voltage V_Cfly1 of the first flying capacitor Cfly1 becomes 0V. Figure 9 (3)). During the discharge of the first flying capacitor Cfly1, all switches Q1 to Q6 are open, but the body diode, such as Figure 10 The current flows as shown by the dashed arrow. If the forward voltage drop Vf of the body diode is ignored, the equivalent circuit in this state is... Figure 11 express.

[0096] Specifically, in the DC-DC converter 10 in the first state mode, when all multiple switching elements are open before startup, the first flying capacitor Cfly1 is connected in series with the output capacitor Cout. Furthermore, in the DC-DC converter 10, when all multiple switching elements are open, the second flying capacitor Cfly2 is connected in parallel with the output capacitor Cout. That is, in the DC-DC converter 10, when all multiple switching elements are open before startup, it is possible to... Figure 11 The equivalent circuit shown is illustrated.

[0097] exist Figure 11In the equivalent circuit shown, if the first flying capacitor Cfly1 is discharged, the voltage of the second flying capacitor Cfly2 becomes equal to that of the output capacitor Cout, thus achieving a state where V_Cfly2:V_Cout=1:1.

[0098] After the first flying capacitor Cfly1 discharges, the charging unit 140 begins to charge the first flying capacitor Cfly1. Figure 9 (4)). Charging ends when the voltage V_Cfly1 detected by the V_Cfly1 detection unit 150 is equal to twice the voltage V_Cout. Figure 9 (5)). Then, oscillation begins in the ADPH converter ( Figure 9 (6), the ADPH converter begins to output.

[0099] Figure 12A This is a waveform diagram used to illustrate the operation of a comparative example of a DC-DC converter. Additionally, Figure 12B This is a waveform diagram used to illustrate the operation of the DC-DC converter 10 according to the first embodiment. For example... Figure 12A As shown, in the comparative example DC-DC converter, a large inrush current flows through the second flying capacitor Cfly2 during startup. Therefore, the comparative example DC-DC converter poses a possibility of damage to components such as capacitors. Furthermore, the comparative example DC-DC converter presents a risk of uncontrolled large current flow. Therefore, countermeasures are needed for the commercialization of ADPH products.

[0100] like Figure 12B As shown, the DC-DC converter 10 of the first embodiment can suppress the generation of surge current. That is, the DC-DC converter 10 of the first embodiment can be implemented with a simple structure that does not use a discharge section and a charging section for the second flying capacitor Cfly2, and the charge of the capacitor can be appropriately adjusted so that surge current is not generated.

[0101] In addition, Figure 9 In (5), experiments were also conducted where charging was terminated when the voltage V_Cfly1 was 2.2 times and 1.8 times that of the voltage V_Cout, rather than twice the voltage V_Cout. Figure 12B In comparison, the inrush current during startup increases (not shown), but it can be confirmed that it is to a degree that is not a practical problem. Preferably, the startup voltage V_Cfly1 is exactly twice the startup voltage V_Cout, but there are also cases where, according to the design specifications of the DC-DC converter, even if there is a certain degree of voltage difference, it can be determined that there is no practical problem.

[0102] (Second Implementation)

[0103] As described above, a specific implementation has been given, but the above implementation is illustrative and does not limit the implementation. For example, in the above implementation, a configuration in which the DC-DC converter 10 of this embodiment is applied to an ADPH converter is illustrated. Here, regarding the DC-DC converter 10, an example of an application to a structure different from the first embodiment will be further described, concerning a structure different from the first embodiment.

[0104] Figure 13 This is a diagram showing the structure of the DC-DC converter 11 according to the second embodiment. Figure 13 The structure shown illustrates the structure of a so-called Dickson-type switched-capacitor converter.

[0105] The DC-DC converter 11 of the second embodiment includes a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, a sixth switch Q6, a seventh switch Q7, and an eighth switch Q8 as multiple switching elements.

[0106] like Figure 13 As shown, in the DC-DC converter 11 of the second embodiment, the first switch Q1, the second switch Q2, the third switch Q3 and the fourth switch Q4 are connected in series between the input terminal Vin of the input power supply and the output terminal Vout.

[0107] In addition, a series circuit consisting of the first flying capacitor Cfly1 and the seventh switch Q7 is connected between the connection point of the second switch Q2 and the third switch Q3 and the ground GND.

[0108] In addition, a series circuit consisting of the second flying capacitor Cfly2 and the eighth switch Q8 is connected between the connection point of the third switch Q3 and the fourth switch Q4 and the ground GND.

[0109] In addition, the fifth switch Q5 is connected between the connection point of the second flying capacitor Cfly2 and the eighth switch Q8 and the output terminal Vout.

[0110] In addition, the sixth switch Q6 is connected between the connection point of the first flying capacitor Cfly1 and the seventh switch Q7 and the output terminal Vout.

[0111] The output capacitor Cout is connected between the output terminal Vout and ground GND. Furthermore, the DC-DC converter 11 of the second embodiment includes a third flying capacitor Cfly3 between the connection point of the first switch Q1 and the second switch Q2, and the connection point of the fifth switch Q5 and the sixth switch Q6. Additionally, in Figure 13The example shown illustrates a structure with a third flying capacitor Cfly3, but it could also be a structure with additional flying capacitors, such as a fourth or fifth flying capacitor.

[0112] Figure 14 This diagram illustrates the operation of the DC-DC converter 11 according to the second embodiment. The DC-DC converter 11 switches the group of first switch Q1, third switch Q3, fifth switch Q5, and seventh switch Q7 with the group of second switch Q2, fourth switch Q4, sixth switch Q6, and eighth switch Q8 in opposite phase and with a 50% duty cycle. Therefore, the DC-DC converter 11 of the second embodiment operates as a converter with a step-down ratio of 1 / 4. Figure 13 and Figure 14 In the example shown, when Vin = 48V, Vout = 12V.

[0113] like Figure 13 and Figure 14 As shown, the DC-DC converter 11 of the second embodiment uses three flying capacitors: a first flying capacitor Cfly1, a second flying capacitor Cfly2, and a third flying capacitor Cfly3.

[0114] For example, when Vin = 48V and Vout = 12V, the voltages of the flying capacitors are as follows: the first flying capacitor Cfly1 = 24V, the second flying capacitor Cfly2 = 12V, and the third flying capacitor Cfly3 = 36V.

[0115] When the power conversion is performed correctly, the capacitor voltages of the first flying capacitor Cfly1, the second flying capacitor Cfly2, the third flying capacitor Cfly3, and the output capacitor Cout are as shown in equation (2).

[0116] [Equation 2]

[0117] V_Cfly3: V_Cfly1: V_Cfly2: V_Cout=3: 2: 1: 1 ··· (2)

[0118] Similar to the ADPH converter in the first embodiment, the Dixon type in the second embodiment also requires startup from this voltage ratio (3:2:1:1).

[0119] Figure 15 This diagram illustrates the operation of the DC-DC converter 11 according to the second embodiment. Before the DC-DC converter 11 is started (Vin applied state, all switches off state), if the first flying capacitor Cfly1 is discharged, the voltage V_Cfly1 of the first flying capacitor Cfly1 becomes 0V.

[0120] At this time, all switches from Q1 to Q8 are open, but the body diode of the switching element is still open. Figure 15 As shown by the dashed arrow, current flows. If the forward voltage drop Vf of the body diode is ignored, the equivalent circuit in this case is... Figure 16 The circuit structure is represented.

[0121] according to Figure 16 In the equivalent circuit shown, if the first flying capacitor Cfly1 is discharged, the voltage V_Cfly2 of the second flying capacitor Cfly2 is equal to the voltage V_Cout of the output capacitor Cout. Therefore, in the DC-DC converter 11 of the second embodiment, no special charging circuit or the like is needed for pre-charging the second flying capacitor Cfly2.

[0122] That is, the DC-DC converter 11 of the second embodiment does not need to be provided with a charging section and a discharging section for controlling the charge of the second flying capacitor Cfly2, thereby reducing the circuit size and cost.

[0123] (Other implementation methods)

[0124] The embodiments have been described in detail with reference to the accompanying drawings, but these embodiments are not limited to the contents described in the above embodiments. Furthermore, the constituent elements described above include elements that are readily conceived by those skilled in the art, as well as substantially the same elements. Moreover, the structures described above can be appropriately combined. Additionally, various omissions, substitutions, or modifications to the structure can be made without departing from the spirit of the embodiments.

[0125] The features of the DC-DC converter 10 are described below.

[0126] The first type of DC-DC converters 10 and 11 converts the DC voltage of the input power supply into a specified output voltage. The DC-DC converters 10 and 11 include an output capacitor Cout that supplies output current to a load device. Additionally, the DC-DC converters 10 and 11 include a first flying capacitor Cfly1, which accumulates charge through the input power supply, accumulating a charge equal to twice the voltage of the output capacitor Cout upon startup. Furthermore, the DC-DC converters 10 and 11 include a second flying capacitor Cfly2, which accumulates charge through the input power supply, accumulating a charge equal to the voltage of the output capacitor Cout upon startup. The DC-DC converters 10 and 11 also include a control circuit 100 that detects the voltage of the output capacitor Cout and controls the charging and discharging of the first flying capacitor Cfly1. Moreover, the control circuit 100 discharges the first flying capacitor Cfly1 before startup. Furthermore, the control circuit 100 charges the first flying capacitor Cfly1 after it discharges, such that the voltage of the first flying capacitor Cfly1 is twice the voltage of the output capacitor Cout.

[0127] According to this structure, DC-DC converters 10 and 11 do not have charging and discharging sections for the second flying capacitor Cfly2, and the charge of the capacitor can be appropriately adjusted with a simple structure. Therefore, DC-DC converters 10 and 11 can be implemented with reduced circuit size and cost.

[0128] The second type of DC-DC converters 10 and 11 can also have multiple switching elements. Alternatively, DC-DC converters 10 and 11 can also be represented by the equivalent circuit shown below. In this equivalent circuit, with all multiple switching elements disconnected before startup, the first flying capacitor Cfly1 is connected in series with the output capacitor Cout, and the second flying capacitor Cfly2 is connected in parallel with the output capacitor Cout.

[0129] With this structure, DC-DC converters 10 and 11 can make the voltage V_Cfly2 of the second flying capacitor Cfly2 match the voltage V_Cout of the output capacitor Cout without providing charging and discharging sections for the second flying capacitor Cfly2. Therefore, DC-DC converters 10 and 11 can appropriately adjust the charge of the capacitor with a simple structure, which can be achieved while reducing circuit size and cost.

[0130] The third-mode DC-DC converter 10 may also include a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, and a sixth switch Q6 as multiple switching elements. Furthermore, the first switch Q1, the second switch Q2, and the third switch Q3 of the DC-DC converter 10 may be connected in series between the input terminal Vin of the input power supply and the output terminal Vout. Additionally, the series circuit of the DC-DC converter 10 consisting of the first flying capacitor Cfly1 and the fourth switch Q4 may be connected between the connection point of the first switch Q1 and the second switch Q2 and ground GND. Similarly, the series circuit of the DC-DC converter 10 consisting of the second flying capacitor Cfly2 and the fifth switch Q5 may be connected between the connection point of the second switch Q2 and the third switch Q3 and ground GND. Furthermore, the sixth switch Q6 of the DC-DC converter 10 may be connected between the connection point of the second flying capacitor Cfly2 and the fifth switch Q5 and the output terminal Vout. Finally, the output capacitor Cout of the DC-DC converter 10 may be connected between the output terminal Vout and ground GND. Furthermore, the DC-DC converter 10 may also have an inductor L between the connection point of the first flying capacitor Cfly1 and the fourth switch Q4 and the output terminal Vout.

[0131] According to this structure, the DC-DC converter 10 does not require a charging section and a discharging section in the ADPH converter to control the charge of the second flying capacitor Cfly2, which can reduce the circuit size and cost.

[0132] The fourth type of DC-DC converter 11 may also include a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, a sixth switch Q6, a seventh switch Q7, and an eighth switch Q8 as multiple switching elements. Furthermore, the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 of the DC-DC converter 11 may also be connected in series between the input terminal Vin of the input power supply and the output terminal Vout. Additionally, the series circuit of the DC-DC converter 11 consisting of the first flying capacitor Cfly1 and the seventh switch Q7 may also be connected between the connection point of the second switch Q2 and the third switch Q3 and ground GND. Furthermore, the series circuit of the DC-DC converter 11 consisting of the second flying capacitor Cfly2 and the eighth switch Q8 may also be connected between the connection point of the third switch Q3 and the fourth switch Q4 and ground GND. Additionally, the fifth switch Q5 of the DC-DC converter 11 may also be connected between the connection point of the second flying capacitor Cfly2 and the eighth switch Q8 and the output terminal Vout. Additionally, the sixth switch Q6 of the DC-DC converter 11 can also be connected between the connection point of the first flying capacitor Cfly1 and the seventh switch Q7 and the output terminal Vout. Furthermore, the output capacitor Cout of the DC-DC converter 11 can also be connected between the output terminal Vout and ground GND. Moreover, the DC-DC converter 11 may also include a third flying capacitor Cfly3 between the connection point of the first switch Q1 and the second switch Q2, and between the connection point of the fifth switch Q5 and the sixth switch Q6.

[0133] According to this structure, the DC-DC converter 11 does not require the charging and discharging sections for controlling the charge of the second flying capacitor Cfly2, which is present in the Dixon-type switched capacitor converter, thus reducing the circuit size and cost.

[0134] The electronic device of the fifth type includes: the DC-DC converters 10 and 11 described above; an input power supply connected to the input terminal Vin of the DC-DC converters 10 and 11; and a load device connected to the output terminal Vout of the DC-DC converters 10 and 11.

[0135] According to this structure, the electronic device can appropriately adjust the charge of the capacitor with a simple structure without setting up charging and discharging sections for the second flying capacitor Cfly2 of the applied DC-DC converters 10 and 11. Therefore, the electronic device can be implemented with reduced circuit size and cost.

Claims

1. A DC-DC converter that converts a DC voltage from an input power supply into a specified output voltage, wherein, The DC-DC converter has the following features: The output capacitor supplies output current to the load device; The first flying capacitor is a flying capacitor that stores charge through the input power supply, and stores a charge at twice the voltage of the output capacitor when it is started. The second flying capacitor is a flying capacitor that stores charge through the input power supply, and stores charge at a voltage equal to that of the output capacitor when it is started. as well as The control circuit detects the voltage of the output capacitor and controls the charging and discharging of the first flying capacitor. Before starting, the control circuit discharges the first flying capacitor. After the first flying capacitor is discharged, it charges the first flying capacitor so that the voltage of the first flying capacitor is twice the voltage of the output capacitor.

2. The DC-DC converter according to claim 1, wherein, The DC-DC converter has multiple switching elements. With all the switching elements disconnected before startup, the DC-DC converter is represented by the following equivalent circuit: the first flying capacitor is connected in series with the output capacitor, and the second flying capacitor is connected in parallel with the output capacitor.

3. The DC-DC converter according to claim 2, wherein, The DC-DC converter includes a first switch, a second switch, a third switch, a fourth switch, a fifth switch, and a sixth switch as multiple switching elements. The first switch, the second switch, and the third switch are connected in series between the input terminal and the output terminal of the input power supply. A series circuit consisting of the first flying capacitor and the fourth switch is connected between the connection point of the first switch and the second switch and ground. A series circuit consisting of the second flying capacitor and the fifth switch is connected between the connection point of the second switch and the third switch and the ground. The sixth switch is connected between the connection point of the second flying capacitor and the fifth switch and the output terminal. The output capacitor is connected between the output terminal and the ground. The DC-DC converter also includes an inductor between the connection point of the first flying capacitor and the fourth switch and the output terminal.

4. The DC-DC converter according to claim 2, wherein, The DC-DC converter includes a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, and an eighth switch as multiple switching elements. The first switch, the second switch, the third switch, and the fourth switch are connected in series between the input terminal and the output terminal of the input power supply. The series circuit consisting of the first flying capacitor and the seventh switch is connected between the connection point of the second switch and the third switch and ground. A series circuit consisting of the second flying capacitor and the eighth switch is connected between the connection point of the third and fourth switches and the ground. The fifth switch is connected between the connection point of the second flying capacitor and the eighth switch and the output terminal. The sixth switch is connected between the connection point of the first flying capacitor and the seventh switch and the output terminal. The output capacitor is connected between the output terminal and the ground. The DC-DC converter also includes a third flying capacitor between the connection point of the first and second switches and the connection point of the fifth and sixth switches.

5. An electronic device, wherein, The electronic device includes: The DC-DC converter according to any one of claims 1 to 4; The input power supply is connected to the input terminal of the DC-DC converter; and The load device is connected to the output terminal of the DC-DC converter.

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