DC-DC converters and electronic equipment

Abstract

This invention provides a DC-DC converter that allows for appropriate adjustment of the capacitor charge with a simple configuration. [Solution] The DC-DC converter 10 includes an output capacitor Cout and a first flying capacitor Cfly1 that stores a charge that, at startup, has a voltage twice that of the output capacitor Cout. The DC-DC converter 10 also includes a second flying capacitor Cfly2 that stores a charge that, at startup, has a voltage equivalent to that of the output capacitor Cout. The DC-DC converter 10 includes 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. The control circuit 100 discharges the first flying capacitor Cfly1 before startup, and after discharge, charges the first flying capacitor Cfly1 so that its voltage becomes approximately twice that of the output capacitor Cout.

Description

Technical Field

[0001] The present disclosure relates to a DC-DC converter and an electronic device.

Background Art

[0002] Conventionally, technologies related to DC-DC converters using switch 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 supplies an output current from two paths of an inductor, a first capacitor, and a second capacitor, thereby reducing the current and conduction loss of the inductor.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the DC-DC converter disclosed in Non-Patent Document 1, it is necessary to accumulate a predetermined charge in the first capacitor and the second capacitor before startup. Therefore, in the DC-DC converter disclosed in Non-Patent Document 1, it is necessary to provide a charging unit and a discharging unit for controlling the charge for each of the first capacitor and the second capacitor, which causes problems such as an increase in circuit scale and cost.

[0005] This disclosure has been made in view of the problems of the prior art. The purpose of this disclosure is to provide a DC-DC converter that can appropriately adjust the charge of a capacitor with a simple configuration. [Means for solving the problem]

[0006] A DC-DC converter according to an embodiment of the present disclosure is a DC-DC converter that converts the DC voltage of an input power supply to a predetermined output voltage, comprising: an output capacitor that supplies output current to a load device; a flying capacitor on which charge is accumulated by the input power supply, the first flying capacitor which accumulates a charge such that the voltage of the output capacitor is twice that of the output capacitor at startup; a flying capacitor on which charge is accumulated by the input power supply, the second flying capacitor which accumulates a charge such that the voltage of the output capacitor is equivalent to that of the output capacitor at startup; and a control circuit that detects the voltage of the output capacitor and controls the charging and discharging of the first flying capacitor, wherein the control circuit discharges the first flying capacitor before startup, and after the discharge of the first flying capacitor, charges the first flying capacitor so that the voltage of the first flying capacitor is approximately twice that of the output capacitor.

[0007] Electronic equipment according to other aspects of this disclosure comprises the above-mentioned 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. [Effects of the Invention]

[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 configuration. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows the configuration of a DC-DC converter according to the first embodiment. [Figure 2] Figure 2 is a diagram illustrating the operation of a DC-DC converter. [Figure 3] Figure 3 is a diagram illustrating the operation of a DC-DC converter. [Figure 4] Figure 4 is a diagram illustrating the operation of a DC-DC converter. [Figure 5] Figure 5 is a diagram illustrating the operation of a DC-DC converter. [Figure 6] Figure 6 shows the configuration of a comparative example of a DC-DC converter. [Figure 7A] Figure 7A is a diagram illustrating the operation of a comparative example of a DC-DC converter. [Figure 7B] Figure 7B is a diagram illustrating the operation of a comparative example of a DC-DC converter. [Figure 8] Figure 8 shows the configuration of a DC-DC converter according to the first embodiment. [Figure 9] Figure 9 is a diagram illustrating the operation of the DC-DC converter according to the first embodiment. [Figure 10] Figure 10 is a diagram illustrating the operation of the DC-DC converter according to the first embodiment. [Figure 11] Figure 11 is an equivalent circuit illustrating the operation of the DC-DC converter according to the first embodiment. [Figure 12A] Figure 12A is a waveform diagram illustrating the operation of a comparative example of a DC-DC converter. [Figure 12B] Figure 12B is a waveform diagram illustrating the operation of the DC-DC converter according to the first embodiment. [Figure 13] Figure 13 shows the configuration of a DC-DC converter according to the second embodiment. [Figure 14] Figure 14 is a diagram illustrating the operation of a DC-DC converter according to the second embodiment. [Figure 15] Figure 15 is a diagram illustrating the operation of a DC-DC converter according to the second embodiment. [Figure 16] Figure 16 is an equivalent circuit illustrating the operation of a DC-DC converter according to the second embodiment.

Mode for Carrying Out the Invention

[0010] Hereinafter, the DCDC converters 10 and 11 according to some embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings of the DCDC converters 10 and 11 according to each embodiment are denoted by the same reference numerals and their description will be omitted.

[0011] (Configuration of DCDC Converter 10) FIG. 1 is a diagram showing the configuration of a DCDC converter 10 according to a first embodiment. The DCDC converter 10 is a DCDC converter that converts the DC voltage of an input power supply into a predetermined output voltage. The DCDC converter 10 according to the first embodiment is an Always-Dual-Path Hybrid (ADPH) DCDC converter. The ADPH converter is a hybrid DCDC converter that combines a buck converter using an inductor L and a switched capacitor.

[0012] As shown in FIG. 1, the ADPH converter includes, as a plurality of switching elements, 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.

[0013] Also, the ADPH converter uses one inductor L and two flying capacitors (a first flying capacitor Cfly1 and a second flying capacitor Cfly2) for power conversion.

[0014] FIG. 2 is a diagram for explaining the operation of an ADPH type DCDC converter. As shown in FIG. 2, in the DCDC converter 10, a set of the first switch Q1, the third switch Q3, and the fifth switch Q5 and a set of the second switch Q2, the fourth switch Q4, and the sixth switch Q6 are turned on and off (switched on and off) in inverse-phase sequences, respectively.

[0015] When the duty cycles of the first switch Q1, the third switch Q3, and the fifth switch Q5 are 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. In this way, the ADPH converter can obtain the desired output voltage depending on the duty cycle.

[0016] For example, in an ADPH converter, when power conversion is functioning correctly, the voltages across 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 across the first flying capacitor Cfly1. Voltage V_Cfly2 is the voltage across the second flying capacitor Cfly2. Furthermore, voltage V_Cout is the voltage across the output capacitor Cout. [Mathematics 1] V_Cfly1:V_Cfly2:V_Cout=2:1:1 ···(1)

[0017] For example, if the output voltage is Vout = 12V, then voltage V_Cfly1 = 24V and voltage V_Cfly2 = 12V. Also, if the output voltage is Vout = 4V, then voltage V_Cfly1 = 8V and voltage V_Cfly2 = 4V.

[0018] The relationship between the capacitor voltages in the ADPH converter is shown in equation (1) above. The ADPH converter must start from this voltage ratio (2:1:1) even at startup. In other words, the ADPH converter must be pre-adjusted to this voltage ratio (initial charge, pre-charge) before starting up.

[0019] For example, if the voltage V_Cout of the output capacitor Cout before startup is 4V, the voltages of the first flying capacitor Cfly1 and the second flying capacitor Cfly2 are set to V_Cfly1=8V and V_Cfly2=4V before startup. Also, if the voltage V_Cout before startup is 0V, the voltages of the first flying capacitor Cfly1 and the second flying capacitor Cfly2 are set to V_Cfly1=0V and V_Cfly2=0V before startup.

[0020] If the system is started with different voltage ratios, a rapid transfer of charge will occur between the three capacitors to achieve a voltage ratio of 2:1:1, resulting in a large surge current.

[0021] Figures 3, 4, and 5 are diagrams illustrating the operation of the DC-DC converter 10 and illustrate the problems of the ADPH circuit.

[0022] For example, if the voltages across the first flying capacitor Cfly1, the second flying capacitor Cfly2, and the output capacitor Cout are all zero, the voltage ratio condition (2:1:1) is met, and the system can start up without any problems.

[0023] However, in an actual circuit, even if all switches Q1 through Q6 are OFF, the resistance between D and S when they are OFF is not infinite, so leakage current occurs as shown in Figure 3. This leakage current charges the first flying capacitor Cfly1, the second flying capacitor Cfly2, and / or the output capacitor Cout, as shown in Figure 4.

[0024] Furthermore, the first flying capacitor Cfly1, the second flying capacitor Cfly2, and / or the output capacitor Cout may be charged by leakage current from FET drive circuits such as high-side drivers. In addition, there is also natural discharge due to the parasitic parallel impedance of each capacitor itself.

[0025] Therefore, since the amount of charge and discharge changes depending on the circuit conditions and time, even if the initial condition is 0V, the voltages V_Cfly1, V_Cfly2, and V_Cout will be undefined.

[0026] Next, we will explain what happens when an ADPH converter that is running is stopped. The output voltage, V_Cout, decreases after stopping, but the amount of decrease mainly depends on the load resistance RL of the load device. Furthermore, as mentioned above, voltages V_Cfly1 and V_Cfly2 change due to factors such as charging due to leakage current and natural discharge. Therefore, voltages V_Cfly1, V_Cfly2, and / or V_Cout remain undefined even when the converter is stopped.

[0027] In other words, the voltages V_Cfly1, V_Cfly2, and V_Cout before startup change due to various factors, and therefore deviate from the voltage ratio condition (2:1:1), as shown in Figure 5. For this reason, control is required to stabilize the voltages V_Cfly1, V_Cfly2, and V_Cout at the voltage ratio condition (2:1:1).

[0028] As mentioned above, the ADPH converter requires the voltages of the three capacitors to be pre-charged before startup so that the ratio of voltages V_Cfly1:V_Cfly2:V_Cout = 2:1:1.

[0029] 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 its voltage (for example, by discharging it) will change the input voltage of the load device.

[0030] Depending on the load device, even when stopped, a sudden drop in input voltage can cause malfunctions such as failures. Furthermore, since the output capacitor Cout generally has a large capacitance value, discharging this capacitance would require a large-scale discharge circuit.

[0031] Therefore, in order to adjust the voltage ratio of each capacitor, it is preferable to adjust the voltages of the two capacitors, the first flying capacitor Cfly1 and / or the second flying capacitor Cfly2, without controlling the output capacitor Cout.

[0032] For example, if the voltage before startup is V_Cout=0V, the voltage ratio condition can be satisfied by precharging to voltages V_Cfly1=0V and V_Cfly2=0V. Also, if the voltage before startup is V_Cout=4V, the voltage ratio condition can be satisfied by precharging to voltages V_Cfly1=8V and V_Cfly2=4V.

[0033] Thus, in order to adjust the voltage ratio of each capacitor, a system is needed to precharge the voltages of the two capacitors, the first flying capacitor Cfly1 and the second flying capacitor Cfly2, before startup.

[0034] Figure 6 shows the configuration of a comparative example of a DC-DC converter. Figures 7A and 7B are diagrams illustrating the operation of the comparative example of a DC-DC converter.

[0035] As shown in Figure 6, the comparative DC-DC converter includes circuits for controlling the charging and discharging of both the first flying capacitor Cfly1 and the second flying capacitor Cfly2.

[0036] The operation of the comparative example shown in Figure 6 will now be explained. First, the V_Cout detection unit detects the voltage V_Cout of the output capacitor Cout. Next, the V_Cfly1 detection unit of the first flying capacitor Cfly1 detects the voltage V_Cfly1. 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 so that the voltage becomes equal to twice the voltage V_Cout (Figure 7A).

[0037] On the other hand, if the determination unit determines that the voltage V_Cfly1 is less than twice the voltage V_Cout, the charging unit 140 charges the first flying capacitor Cfly1 so that the voltage becomes equal to twice the voltage V_Cout.

[0038] Furthermore, the V_Cfly2 detection unit of the second flying capacitor Cfly2 detects the voltage V_Cfly2. The determination unit of the second flying capacitor Cfly2 determines 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 unit of the second flying capacitor Cfly2 discharges the second flying capacitor Cfly2 so that the voltage becomes equal to the voltage V_Cout (Figure 7B).

[0039] On the other hand, if 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 so that the voltage becomes equal to V_Cout. After that, the ADPH converter starts oscillating (ADPH converter output starts).

[0040] Thus, in the comparative examples shown in Figures 6, 7A, and 7B, a determination unit, a discharge unit, and a charging unit are provided for both the first flying capacitor Cfly1 and the second flying capacitor Cfly2, respectively. Therefore, an increase in circuit size and cost becomes a problem.

[0041] The DC-DC converters 10 and 11 according to this embodiment realize a DC-DC converter that can appropriately adjust the charge of the second flying capacitor Cfly2 with a simple configuration, without providing a charging section or a discharging section.

[0042] (First Embodiment) Figure 8 shows the configuration of a DC-DC converter 10 according to the first embodiment. The DC-DC converter 10 includes 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.

[0043] Furthermore, the DC-DC converter 10 includes multiple switching elements, comprising 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.

[0044] 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. The 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 the ground GND. The 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 the ground GND. The 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. The output capacitor Cout is connected between the output terminal Vout and the ground GND. Furthermore, the inductor L is connected between the connection point of the first flying capacitor Cfly1 and the fourth switch Q4 and the output terminal Vout.

[0045] The first flying capacitor Cfly1 is a flying capacitor that accumulates charge due to the input power supply. Furthermore, the first flying capacitor Cfly1 accumulates a charge at startup that is twice the voltage across the output capacitor Cout.

[0046] The second flying capacitor Cfly2 is a flying capacitor that accumulates charge due to the input power supply, and at startup, it accumulates a charge that is equivalent to the voltage across the output capacitor Cout.

[0047] The control circuit 100 includes a determination unit 110 for determining whether to discharge or charge the first flying capacitor Cfly1, and a V_Cout detection unit 120 for detecting the voltage V_Cout of the output capacitor Cout. The control circuit 100 also includes a discharge unit 130 and a charge unit 140 for the first flying capacitor Cfly1. The control circuit 100 also 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.

[0048] The control circuit 100 of the DC-DC converter 10 according to the first embodiment differs from the comparative example DC-DC converter shown in Figure 6 above in that it does not include a charging section and a discharging section for the second flying capacitor Cfly2.

[0049] Figures 9 and 10 illustrate the operation of the DC-DC converter 10 according to the first embodiment. Before startup, with an applied voltage at the input terminal Vin and all switching elements in the OFF state, detection of the voltage V_Cout of the output capacitor Cout is started (Figures 9(1) to (5)). Next, the first flying capacitor Cfly1 is discharged (Figure 9(2)). In Figure 10, this is schematically shown by a short circuit with a resistor.

[0050] Subsequently, the voltage V_Cfly1 across the first flying capacitor Cfly1 becomes 0V (Figure 9 (3)). While the first flying capacitor Cfly1 is discharging, switches Q1 through Q6 are all in the OFF state, but current flows through the body diode as shown by the dashed arrow in Figure 10. Ignoring the forward voltage drop Vf across the body diode, the equivalent circuit in this state is shown in Figure 11.

[0051] Specifically, in the first state configuration, the DC-DC converter 10 has a first flying capacitor Cfly1 connected in series with the output capacitor Cout when all of its switching elements are off before startup. Furthermore, in the DC-DC converter 10, a second flying capacitor Cfly2 is connected in parallel with the output capacitor Cout when all of its switching elements are off. In other words, the DC-DC converter 10 can be represented by the equivalent circuit shown in Figure 11 when all of its switching elements are off before startup.

[0052] In the equivalent circuit shown in Figure 11, when the first flying capacitor Cfly1 is discharged, the voltages of the second flying capacitor Cfly2 and the output capacitor Cout become equal, making it possible to achieve a state where V_Cfly2:V_Cout=1:1.

[0053] After the first flying capacitor Cfly1 has discharged, the charging unit 140 starts charging the first flying capacitor Cfly1 (Figure 9 (4)). Charging ends when the voltage V_Cfly1 detected by the V_Cfly1 detection unit 150 becomes equal to twice the voltage V_Cout (Figure 9 (5)). Subsequently, the ADPH converter starts oscillating (Figure 9 (6), ADPH converter output starts).

[0054] Figure 12A is a waveform diagram illustrating the operation of a comparative example of a DC-DC converter. Figure 12B is a waveform diagram illustrating the operation of the DC-DC converter 10 according to the first embodiment. As shown in Figure 12A, the DC-DC converter in the comparative example experiences a large surge current flowing through the second flying capacitor Cfly2 during startup. Therefore, components such as the capacitor may be damaged in the DC-DC converter in the comparative example. Furthermore, the DC-DC converter in the comparative example poses a risk of uncontrolled large current flow. For this reason, some countermeasures are necessary for the commercialization of ADPH.

[0055] As shown in Figure 12B, the DC-DC converter 10 according to the first embodiment can suppress the generation of surge current. That is, the DC-DC converter 10 according to the first embodiment can be realized with a simple configuration that does not use a discharge section or a charging section for the second flying capacitor Cfly2, and it is possible to appropriately adjust the charge of the capacitor so that a surge current does not occur.

[0056] Furthermore, in Figure 9(5), experiments were also conducted in which charging was terminated when the voltage V_Cfly1 was 2.2 times and 1.8 times the voltage V_Cout, instead of twice the voltage V_Cout. Compared to Figure 12B, the surge current at startup increased (not shown), but it was confirmed that it was within a range that did not pose a practical problem. It is desirable that the startup voltage V_Cfly1 be exactly twice the startup voltage V_Cout, but depending on the design specifications of the DC-DC converter, it may be judged that a certain voltage difference is not a practical problem.

[0057] (Second embodiment) As described above, one specific embodiment has been explained, but the embodiment described above is illustrative and does not limit the embodiments. For example, in the embodiment described above, an example was shown in which the DCDC converter 10 according to this embodiment is applied to an ADPH converter. Here, we will further describe an example in which the DCDC converter 10 is applied to a configuration different from that of an ADPH converter, and a configuration different from that of the first embodiment.

[0058] Figure 13 shows the configuration of the DC-DC converter 11 according to the second embodiment. The configuration shown in Figure 13 represents the configuration of a so-called Dickson-type switched-capacitor converter.

[0059] The DC-DC converter 11 according to the second embodiment includes a plurality of switching elements: 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.

[0060] As shown in Figure 13, in the DC-DC converter 11 according to 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 and the output terminal Vout of the input power supply.

[0061] Furthermore, the series circuit consisting of the first flying capacitor Cfly1 and the seventh switch Q7 is connected between the connection point between the second switch Q2 and the third switch Q3 and the ground GND.

[0062] Furthermore, the series circuit consisting of the second flying capacitor Cfly2 and the eighth switch Q8 is connected between the connection point between the third switch Q3 and the fourth switch Q4 and the ground GND.

[0063] Furthermore, the fifth switch Q5 is connected between the connection point between the second flying capacitor Cfly2 and the eighth switch Q8, and the output terminal Vout.

[0064] Furthermore, the sixth switch Q6 is connected between the connection point between the first flying capacitor Cfly1 and the seventh switch Q7, and the output terminal Vout.

[0065] The output capacitor Cout is connected between the output terminal Vout and ground GND. Furthermore, the DC-DC converter 11 according to 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. In the example shown in Figure 13, a configuration with a third flying capacitor Cfly3 is shown, but a configuration with additional flying capacitors such as a fourth flying capacitor and a fifth flying capacitor may also be used.

[0066] Figure 14 is a diagram illustrating the operation of the DC-DC converter 11 according to the second embodiment. The DC-DC converter 11 switches the set of switches Q1, Q3, Q5, and Q7 and the set of switches Q2, Q4, Q6, and Q8 in opposite phases on and off at a duty cycle of 50%. As a result, the DC-DC converter 11 according to the second embodiment operates as a converter with a step-down ratio of 1 / 4. In the example shown in Figures 13 and 14, when Vin = 48V, Vout = 12V.

[0067] As shown in Figures 13 and 14, the DC-DC converter 11 according to the second embodiment uses three flying capacitors: a first flying capacitor Cfly1, a second flying capacitor Cfly2, and a third flying capacitor Cfly3.

[0068] For example, when Vin = 48V and Vout = 12V, the voltages of each flying capacitor are as follows: 1st flying capacitor Cfly1 = 24V, 2nd flying capacitor Cfly2 = 12V, and 3rd flying capacitor Cfly3 = 36V.

[0069] In an operating state where power conversion is performed correctly, the voltages across the first flying capacitor Cfly1, the second flying capacitor Cfly2, the third flying capacitor Cfly3, and the output capacitor Cout are related as shown in equation (2) below. [Math 2] V_Cfly3:V_Cfly1:V_Cfly2:V_Cout =3:2:1:1 ···(2)

[0070] Similar to the ADPH converter according to the first embodiment, the Dickson type according to the second embodiment also needs to start up from the voltage ratio (3:2:1:1).

[0071] Figure 15 is a diagram illustrating the operation of the DC-DC converter 11 according to the second embodiment. When the first flying capacitor Cfly1 is discharged before the DC-DC converter 11 is started (Vin applied, all switches OFF), the voltage V_Cfly1 of the first flying capacitor Cfly1 becomes 0V.

[0072] At this time, all switches Q1 through Q8 are OFF, but current flows through the body diodes of the switching elements as shown by the dashed arrows in Figure 15. If we ignore the forward voltage drop Vf of the body diodes, the equivalent circuit in this case is represented by the circuit configuration in Figure 16.

[0073] As shown in the equivalent circuit in Figure 16, if the first flying capacitor Cfly1 is discharged, the voltage V_Cfly2 of the second flying capacitor Cfly2 becomes equal to the voltage V_Cout of the output capacitor Cout. Therefore, in the DC-DC converter 11 according to the second embodiment, no special charging circuit for precharging is required for the second flying capacitor Cfly2.

[0074] In other words, the DC-DC converter 11 according to the second embodiment does not require a charging section and a discharging section to control the charge of the second flying capacitor Cfly2, thereby reducing the circuit size and cost.

[0075] (Other embodiments) While embodiments have been described in detail with reference to the drawings, these embodiments are not limited to those described above. Furthermore, the components described above include those easily conceivable by those skilled in the art, and those that are substantially the same. Moreover, the configurations described above can be combined as appropriate. In addition, various omissions, substitutions, or modifications of the configurations can be made without departing from the spirit of the embodiments.

[0076] The features of the DC-DC converter 10 are described below.

[0077] The DC-DC converters 10 and 11 according to the first embodiment are DC-DC converters 10 and 11 that convert the DC voltage of an input power supply to a predetermined output voltage. The DC-DC converters 10 and 11 include an output capacitor Cout that supplies output current to a load device. The DC-DC converters 10 and 11 also include a first flying capacitor Cfly1, which is a flying capacitor that stores charge from the input power supply and stores a charge that, at startup, is twice the voltage of the output capacitor Cout. The DC-DC converters 10 and 11 also include a second flying capacitor Cfly2, which is a flying capacitor that stores charge from the input power supply and stores a charge that, at startup, is equivalent to the voltage of the output capacitor Cout. 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. The control circuit 100 also discharges the first flying capacitor Cfly1 before startup. Furthermore, after the discharge of the first flying capacitor Cfly1, the control circuit 100 charges the first flying capacitor Cfly1 so that its voltage becomes approximately twice the voltage of the output capacitor Cout.

[0078] This configuration allows the DC-DC converters 10 and 11 to appropriately adjust the charge of the second flying capacitor Cfly2 with a simple configuration, without requiring charging or discharging sections for the capacitor. Therefore, the DC-DC converters 10 and 11 can be realized with reduced circuit size and cost.

[0079] The DC-DC converters 10 and 11 according to the second embodiment may include a plurality of switching elements. The DC-DC converters 10 and 11 may also be represented by the equivalent circuit shown below. In this equivalent circuit, when all of the plurality of switching elements are turned off 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.

[0080] With this configuration, the DC-DC converters 10 and 11 can match the voltage V_Cfly2 of the second flying capacitor Cfly2 to the voltage V_Cout of the output capacitor Cout without requiring a charging or discharging section for the second flying capacitor Cfly2. Therefore, the DC-DC converters 10 and 11 can appropriately adjust the capacitor charge with a simple configuration, making it possible to implement this with reduced circuit size and cost.

[0081] The DC-DC converter 10 according to the third embodiment may include a plurality of switching elements: 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. 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 and the output terminal Vout of the input power supply. Also, the series circuit consisting of the first flying capacitor Cfly1 and the fourth switch Q4 of the DC-DC converter 10 may be connected between the connection point between the first switch Q1 and the second switch Q2 and the ground GND. Furthermore, the series circuit consisting of the second flying capacitor Cfly2 and the fifth switch Q5 of the DC-DC converter 10 may be connected between the connection point between the second switch Q2 and the third switch Q3 and the ground GND. Furthermore, the sixth switch Q6 of the DC-DC converter 10 may be connected between the connection point between the second flying capacitor Cfly2 and the fifth switch Q5 and the output terminal Vout. Also, the output capacitor Cout of the DC-DC converter 10 may be connected between the output terminal Vout and ground GND. In addition, the DC-DC converter 10 may include an inductor L between the connection point between the first flying capacitor Cfly1 and the fourth switch Q4 and the output terminal Vout.

[0082] This configuration eliminates the need for charging and discharging sections in the ADPH converter to control the charge of the second flying capacitor Cfly2, thereby reducing circuit size and cost.

[0083] The DC-DC converter 11 according to the fourth embodiment may include a plurality of switching elements: 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. 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 be connected in series between the input terminal Vin and the output terminal Vout of the input power supply. Also, the series circuit consisting of the first flying capacitor Cfly1 and the seventh switch Q7 of the DC-DC converter 11 may be connected between the connection point between the second switch Q2 and the third switch Q3 and the ground GND. Furthermore, the series circuit consisting of the second flying capacitor Cfly2 and the eighth switch Q8 of the DC-DC converter 11 may be connected between the connection point between the third switch Q3 and the fourth switch Q4 and the ground GND. Furthermore, the fifth switch Q5 of the DCDC converter 11 may be connected between the connection point between the second flying capacitor Cfly2 and the eighth switch Q8 and the output terminal Vout. Also, the sixth switch Q6 of the DCDC converter 11 may be connected between the connection point between the first flying capacitor Cfly1 and the seventh switch Q7 and the output terminal Vout. Furthermore, the output capacitor Cout of the DCDC converter 11 may be connected between the output terminal Vout and ground GND. In addition, the DCDC converter 11 may further include a third flying capacitor Cfly3 between the connection point between the first switch Q1 and the second switch Q2 and the connection point between the fifth switch Q5 and the sixth switch Q6.

[0084] This configuration eliminates the need for charging and discharging sections to control the charge of the second flying capacitor Cfly2 in a Dixon-type switched-capacitor converter, thereby reducing circuit size and cost.

[0085] The electronic device according to the fifth embodiment comprises the above-mentioned DC-DC converters 10 and 11, 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.

[0086] This configuration allows electronic devices to appropriately adjust the charge of the second flying capacitor Cfly2 of the applicable DC-DC converters 10 and 11 without requiring charging or discharging sections, resulting in a simpler design. Therefore, electronic devices can be implemented with reduced circuit size and cost. [Explanation of Symbols]

[0087] 10, 11 DC-DC converter 100 control circuits 110 Judgment section 120 V_Cout detection unit 130 Discharge section 140 Live parts 150 V_Cfly1 detection unit Cfly1 First Flying Capacitor Cfly2 Second Flying Capacitor Cfly3 3rd Flying Capacitor Cout output capacitor L Inductor Vin input terminal Vout output terminal GND (Ground) Q1 First switch Q2 Second switch Q3 Third switch Q4 Fourth switch Q5 Fifth switch Q6 Switch 6 Q7 Switch 7 Q8 Switch 8

Claims

1. A DC-DC converter that converts the DC voltage of an input power supply to a predetermined output voltage, An output capacitor that supplies output current to the load device, A flying capacitor in which charge is accumulated by the input power supply, comprising a first flying capacitor that accumulates a charge such that the voltage is twice the voltage of the output capacitor at startup, A flying capacitor that stores charge by the input power supply, comprising a second flying capacitor that stores charge to a voltage equivalent to the voltage of the output capacitor at startup, The system includes 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 after the discharge of the first flying capacitor, charges the first flying capacitor so that its voltage becomes approximately twice the voltage of the output capacitor, in a DC-DC converter.

2. Equipped with multiple switching elements, The DC-DC converter according to claim 1, represented by an equivalent circuit in which, when all of the switching elements are turned off before startup, 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 plurality of switching elements include a first switch, a second switch, a third switch, a fourth switch, a fifth switch, and a sixth switch. 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. The 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. The series circuit consisting of the second flying capacitor and the fifth switch is connected between the connection point between the second switch and the third switch and the ground. The sixth switch is connected between the connection point between the second flying capacitor and the fifth switch and the output terminal. The output capacitor is connected between the output terminal and the ground. Furthermore, the DC-DC converter according to claim 2, further comprising an inductor between the connection point of the first flying capacitor and the fourth switch and the output terminal.

4. The system comprises a plurality of switching elements, including 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. 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. The series circuit consisting of the second flying capacitor and the eighth switch is connected between the connection point of the third switch and the fourth switch and the ground. The fifth switch is connected between the connection point between the second flying capacitor and the eighth switch and the output terminal. The sixth switch is connected between the connection point between 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 according to claim 2, further comprising a third flying capacitor between the connection point of the first switch and the second switch and the connection point of the fifth switch and the sixth switch.

5. A DC-DC converter as described in any one of claims 1 to 4, The input power supply connected to the input terminal of the DCDC converter, The load device connected to the output terminal of the DC-DC converter, Electronic devices equipped with these features.

Images