DC / DC converters, electronic modules, and electronic equipment.

Abstract

To provide a DC / DC converter capable of reducing ripple noise on an output voltage regardless of the magnitude of load current.SOLUTION: A DC / DC converter includes a plurality of channels each of which includes a switching circuit and an inductor, an output line whose one end is connected to other ends of the inductors in the plurality of channels and whose other end is connected to a load, and a controller, the plurality of channels include a first to a third channels, inductors on the first and the second channels have a larger inductance value than the inductor on the third channel, the controller controls a switching circuit so that only the first channel operates if current flowing the load is first current, and controls the switching circuit so that the first and the second channels operate with the same phase and the third channel operates with phase different from the first and the second channels if the current flowing the load is second current larger than the first current.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present invention relates to a DC / DC converter, an electronic module, and an electronic device.

Background Art

[0002] Patent Document 1 describes a technique for improving the efficiency in a multi-phase DC / DC converter in a light load state. In the technique described in Patent Document 1, the inductance of the inductor of the single channel is set to a value different from the inductance of the inductors of the other channels so that high efficiency can be obtained in the lightest load state where only a single channel becomes active.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technique described in Patent Document 1, there is a problem that the ripple noise in the output voltage increases in a state where a plurality of channels of the multi-phase DC / DC converter operate and the load current flowing through the load is large.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a DC / DC converter capable of reducing the ripple noise in the output voltage regardless of the magnitude of the load current.

Means for Solving the Problems

[0006] According to one aspect of the present invention, the present invention comprises an input line to which a DC voltage is supplied, a plurality of channels each including a switching circuit and an inductor, one end of the inductor connected to the input line via the switching circuit, an output line to which the other ends of the inductors of the plurality of channels are connected to one end and a load connected to the other end, and a controller for controlling the switching circuits of the plurality of channels, wherein the plurality of channels include at least a first channel, a second channel, and a third channel, and the inductors of the first and second channels are larger than the inductor of the third channel. A DC / DC converter is provided, characterized in that, when the current flowing through the load is a first current, the controller controls the switching circuits of the first to third channels so that only the first channel operates and the second and third channels are stopped, and when the current flowing through the load is a second current which is larger than the first current, the controller controls the switching circuits of the first to third channels so that the first and second channels operate in phase and the third channel operates in phase different from the first and second channels. [Effects of the Invention]

[0007] According to the present invention, ripple noise in the output voltage can be reduced regardless of the magnitude of the load current. [Brief explanation of the drawing]

[0008] [Figure 1A] This is a circuit diagram showing the circuit of a DC / DC converter according to a first embodiment of the present invention. [Figure 1B] This figure shows an example of the operating waveform of a DC / DC converter according to the first embodiment of the present invention. [Figure 1C] This figure shows an example of the operating waveform of a DC / DC converter according to the first embodiment of the present invention. [Figure 1D] This figure shows an example of the operating waveform of a DC / DC converter according to the first embodiment of the present invention. [Figure 2] This is a circuit diagram showing the circuit of a DC / DC converter according to a second embodiment of the present invention. [Figure 3A] This is a circuit diagram showing the circuitry of a DC / DC converter in a comparative configuration. [Figure 3B] This figure shows examples of DC / DC converter operating waveforms in different configurations. [Figure 3C] This figure shows examples of DC / DC converter operating waveforms in different configurations. [Figure 3D] This figure shows examples of DC / DC converter operating waveforms in different configurations. [Figure 3E] This figure shows examples of DC / DC converter operating waveforms in different configurations. [Figure 3F] This figure shows examples of DC / DC converter operating waveforms in different configurations. [Figure 4A] This is a circuit diagram showing the circuit of a DC / DC converter according to a third embodiment of the present invention. [Figure 4B] This figure shows an example of the operating waveform of a DC / DC converter according to the third embodiment of the present invention. [Figure 4C] This figure shows an example of the operating waveform of a DC / DC converter according to the third embodiment of the present invention. [Figure 4D] This figure shows an example of the operating waveform of a DC / DC converter according to the third embodiment of the present invention. [Figure 4E] This figure shows an example of the operating waveform of a DC / DC converter according to the third embodiment of the present invention. [Figure 4F] This figure shows an example of the operating waveform of a DC / DC converter according to the third embodiment of the present invention. [Figure 5A] This figure shows an example of the operating waveform of a DC / DC converter according to the fourth embodiment of the present invention. [Figure 5B] This figure shows an example of the operating waveform of a DC / DC converter according to the fourth embodiment of the present invention. [Figure 5C] This figure shows an example of the operating waveform of a DC / DC converter according to the fourth embodiment of the present invention. [Figure 5D] FIG. is a diagram showing an example of an operation waveform of a DC / DC converter according to a fourth embodiment of the present invention. [Figure 5E] FIG. is a diagram showing an example of an operation waveform of a DC / DC converter according to a fourth embodiment of the present invention. [Figure 6A] FIG. is a cross-sectional view showing a digital camera as an example of an electronic device according to a fifth embodiment of the present invention. [Figure 6B] FIG. is a perspective view showing a processing module in a digital camera which is an imaging device as an example of an electronic device according to a fifth embodiment of the present invention. [Figure 6C] FIG. is a cross-sectional view showing a processing module in a digital camera which is an imaging device as an example of an electronic device according to a fifth embodiment of the present invention. [Figure 7A] FIG. is a circuit diagram showing a circuit of a general multi-phase DC / DC converter. [Figure 7B] FIG. is a circuit diagram showing a circuit of a multi-phase DC / DC converter described in Patent Document 1. [Figure 7C] FIG. is a diagram showing an operation waveform of a general multi-phase DC / DC converter when only a single channel operates. [Figure 7D] FIG. is a diagram showing an operation waveform of a general multi-phase DC / DC converter when only a single channel operates. [Figure 7E] FIG. is a diagram showing an operation waveform of a general multi-phase DC / DC converter when only a single channel operates. [Figure 7F] FIG. is a diagram showing an operation waveform of the multi-phase DC / DC converter described in Patent Document 1 when only a single channel operates. [Figure 7G] FIG. is a diagram showing an operation waveform of the multi-phase DC / DC converter described in Patent Document 1 when only a single channel operates. [Figure 7H] FIG. is a diagram showing an operation waveform of the multi-phase DC / DC converter described in Patent Document 1 when only a single channel operates. [Figure 7I]This figure shows the operating waveform of a typical multi-phase DC / DC converter when multiple channels are in operation. [Figure 7J] This figure shows the operating waveform of a typical multi-phase DC / DC converter when multiple channels are in operation. [Figure 7K] This figure shows the operating waveform of a typical multi-phase DC / DC converter when multiple channels are in operation. [Figure 7L] This figure shows the operating waveform of the multiphase DC / DC converter described in Patent Document 1 when multiple channels are in operation. [Figure 7M] This figure shows the operating waveform of the multiphase DC / DC converter described in Patent Document 1 when multiple channels are in operation. [Figure 7N] This figure shows the operating waveform of the multiphase DC / DC converter described in Patent Document 1 when multiple channels are in operation. [Modes for carrying out the invention]

[0009] [Reference technology] Electronic modules mounted in electronic devices consist of a printed circuit board, a semiconductor device mounted on the printed circuit board, and a power supply circuit that supplies power to the semiconductor device. In recent years, the amount of current required for the operation of semiconductor devices has increased due to the increase in the amount of data processed per unit time. Therefore, DC / DC converters, which do not experience a significant increase in losses even when the current increases, are used as power supply circuits. While DC / DC converters are highly efficient, ripple noise is superimposed on the output voltage due to the switching operation that controls the magnitude of the output current and output voltage. Due to advances in semiconductor technology and the increasing demand for lower power consumption, the operating voltage of semiconductor devices is steadily decreasing. Along with this decrease in voltage, the allowable noise level set to avoid malfunctions of semiconductor devices is also decreasing, so DC / DC converters are required to be both highly efficient and to reduce ripple noise.

[0010] Among semiconductor devices, CPUs (Central Processing Units), GPUs (Graphics Processing Units), and DSPs (Digital Signal Processors) exhibit a significant decrease in operating current, reaching near-zero levels in standby mode, while conversely, their operating current increases dramatically in operation mode depending on the amount of data being processed. In other words, the output current (load current) of a DC / DC converter fluctuates greatly, ranging from a few mA to several A. To accommodate this large dynamic range of load current, multi-phase DC / DC converters, such as those described in Patent Document 1, are used, which consist of multiple DC / DC converters connected in parallel. This multi-phase DC / DC converter operates only one DC / DC converter when the load (such as a CPU) is in standby mode, and operates all DC / DC converters in full operation mode, thereby accommodating increases and decreases in current. In the standby mode of a semiconductor device, only one DC / DC converter operates, which has the advantage of minimizing switching losses. Furthermore, in the full operation mode, where all DC / DC converters are operating, the phases of each converter are shifted, causing their ripple noises to cancel each other out, thus reducing the total ripple noise.

[0011] However, when a semiconductor device is in standby mode, or when only a single DC / DC converter is operating, this cancellation effect is absent, resulting in a problem where ripple noise is greater than during full operation. Therefore, Patent Document 1 discloses a technique that can reduce ripple noise even when only a single DC / DC converter is operating, such as in standby mode. Specifically, Patent Document 1 reduces ripple noise by setting the inductance value of only the output inductor component of the DC / DC converter operating in the standby state of the semiconductor device to a large value, thereby reducing the amplitude of the current generated during switching operation.

[0012] As reference technology, a general multiphase DC / DC converter and the multiphase DC / DC converter described in Patent Document 1 will be explained using Figures 7A to 7H.

[0013] Figure 7A is a circuit diagram showing an example of a typical multi-phase DC / DC converter circuit. The example shown in Figure 7A is a two-phase circuit. As shown in Figure 7A, the DC / DC converter 60A, which is a typical multi-phase DC / DC converter, has switching circuits 602A and 603A, inductors 604A and 605A, a capacitor 606A, and a controller 608A. The DC / DC converter 60A also has an input line 621A and an output line 622A.

[0014] Input line 621A is a wire that receives a DC voltage from input voltage source 601A. Input voltage source 601A is connected to one end of input line 621A. Input voltage source 601A supplies a DC voltage to input line 621A. The input voltage source 601A is not particularly limited, but for example, it may be a power source that supplies a DC voltage converted from AC power supplied from a commercial power source, or it may be a battery. Switching circuits 602A and 603A are connected in parallel to the other end of input line 621A via wiring.

[0015] Switching circuits 602A and 603A are each composed of a CMOS (Complementary Metal Oxide Semiconductor) inverter having a P-type MOS (Metal Oxide Semiconductor) transistor Tr1 and an N-type MOS transistor Tr2, respectively. In both switching circuits 602A and 603A, the source of the P-type MOS transistor Tr1 is connected to the other end of the input line 621A via wiring. The source of the N-type MOS transistor Tr2 is connected to the reference potential 609A, which is ground potential, via wiring. Furthermore, the gates of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 are connected to the controller 608A via wiring. In switching circuit 602A, the drains of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 are connected in common and connected to one end of the inductor 604A via wiring as the output terminal. In switching circuit 603A, the drains of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 are connected in common and connected to one end of the inductor 605A via wiring as the output terminal.

[0016] Controller 608A is a control unit that controls the switching operation of switching circuits 602A and 603A to switch them on and off. Controller 608A controls the switching operation by controlling the voltage supplied to the gate of the P-type MOS transistor Tr1 and the gate of the N-type MOS transistor Tr2 of switching circuits 602A and 603A.

[0017] Inductors 604A and 605A are inductors with the same inductance value L. The other ends of inductor 604A and inductor 605A are connected in common via wiring to one end of output line 622A. In Figure 7A, the current 610A indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 604A to one end of output line 622A. The current 611A indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 605A to one end of output line 622A.

[0018] Output line 622A is a wiring that supplies a DC voltage to a load 607A, such as a semiconductor device. The other end of output line 622A is connected to the load 607A. Capacitor 606A is connected between output line 622A and the reference potential 609A via wiring. In Figure 7A, the current 612A indicated by the arrow represents the current generated in output line 622A before capacitor 606A.

[0019] The DC / DC converter 60A switches the power supplied from the input voltage source 601A to the input line 621A on and off by the switching operation of switching circuits 602A and 603A and sends it to the subsequent inductors 604A and 605A. Furthermore, the DC / DC converter 60A smooths the power sent to inductors 604A and 605A with capacitor 606A and supplies a desired constant voltage to the load 607A. At this time, the controller 608A controls the timing of the switching operation of switching circuits 602A and 603A. Here, the switching circuit 602A and inductor 604A constitute a single DC / DC converter unit. The switching circuit 603A and inductor 605A also constitute a single DC / DC converter unit. Each of these units is called a channel. The DC / DC converter 60A has two channels: a first channel consisting of a switching circuit 602A and an inductor 604A, and a second channel consisting of a switching circuit 603A and an inductor 605A. The switching circuits 602A and 603A in each channel operate at the same switching frequency, which is typically several MHz.

[0020] On the other hand, Figure 7B is a circuit diagram showing the circuit of a multiphase DC / DC converter described in Patent Document 1. As shown in Figure 7B, the DC / DC converter 60B, which is a multiphase DC / DC converter described in Patent Document 1, has a configuration corresponding to the DC / DC converter 60A shown in Figure 7A. In Figure 7B, the components corresponding to those shown in Figure 7A are indicated by changing the alphabet in the notation from A to B. The DC / DC converter 60B differs from the DC / DC converter 60A in that the inductor 604B has an inductance value L′ that is larger than the inductance value L of the inductor 605B.

[0021] Next, the current and voltage waveforms in DC / DC converters 60A and 60B when only one channel is operating, such as when the semiconductor device (the load) is in standby mode, will be explained using Figures 7C to 7H. Figures 7C, 7D, and 7E show the waveforms of the currents 610A and 611A of inductors 604A and 605A, the current 612A before capacitor 606A, and the voltage of the load 607A, respectively, in DC / DC converter 60A shown in Figure 7A. Figures 7F, 7G, and 7H show the waveforms of the currents 610B and 611B of inductors 604B and 605B, the current 612B before capacitor 606B, and the voltage of the load 607B, respectively, in DC / DC converter 60B shown in Figure 7B. Here, the circuit simulator PSpice from Cadence Design Systems was used for the current and voltage waveform analysis. For the waveform analysis, the circuit conditions were as follows: the input voltage sources 601A and 601B had a voltage of 3V, the inductance values ​​L were 0.1μH and L′ were 0.2μH, and the switching frequency was 4MHz. Furthermore, for the waveform analysis, the first channel was operated as a single channel.

[0022] As can be seen in Figures 7C and 7F, comparing the currents 610A and 610B of the first channel, the amplitude of current 610B, which has a larger inductance value, is smaller than that of current 610A. In this case, since only one channel is operating, current 610A remains as current 612A, and current 610B remains as current 612B. In these cases, in DC / DC converter 60A, the ripple voltage, including ripple noise, is generated at the load 607A as the product of current 612A and the impedance of capacitor 606A. Similarly, in DC / DC converter 60B, the ripple voltage, including ripple noise, is generated at the load 607B as the product of current 612B and the impedance of capacitor 606B. The amplitude of the ripple voltage in DC / DC converter 60B is 16.9mV, as shown in Figure 7H, which is approximately half the amplitude of the ripple voltage of 33.6mV shown in Figure 7E.

[0023] Next, the current and voltage waveforms in DC / DC converters 60A and 60B when multiple channels are operating, such as when the semiconductor device is in full operation, will be explained using Figures 7I to 7N. Figures 7I, 7J, and 7K show the waveforms of the currents 610A and 611A of inductors 604A and 605A, the current 612A before capacitor 606A, and the voltage of load 607A in DC / DC converter 60A shown in Figure 7A, respectively. Figures 7L, 7M, and 7N show the waveforms of the currents 610B and 611B of inductors 604B and 605B, the current 612B before capacitor 606B, and the voltage of load 607B in DC / DC converter 60B shown in Figure 7B, respectively. The current and voltage waveform analysis was performed under the same conditions as above, except that the first and second channels were operated.

[0024] As can be seen in Figures 7I, 7J, and 7K, in the DC / DC converter 60A, a typical multiphase DC / DC converter shown in Figure 7A, currents 610A and 611A flow with the same amplitude and a phase difference of 180 degrees. Therefore, due to the cancellation effect of the individual currents 610A and 611A, the combined current 612A has a small amplitude, as shown in Figure 7J. As a result, the voltage across the load 607A has a small amplitude, as shown in Figure 7K.

[0025] On the other hand, as can be seen in Figure 7L, in the case of DC / DC converter 60B, which is a multiphase DC / DC converter described in Patent Document 1 shown in Figure 7B, the amplitudes of currents 610B and 611B are different. Therefore, the cancellation effect of currents 610B and 611B is reduced, and as shown in Figure 7M, the amplitude of the combined current 612B is increased. As a result, as shown in Figure 7N, the ripple voltage appearing at load 607B is increased.

[0026] Thus, in general multi-phase DC / DC converters and the multi-phase DC / DC converter described in Patent Document 1, it has been difficult to reduce ripple noise in the output voltage regardless of the magnitude of the load current. In contrast, the DC / DC converters according to the first to fourth embodiments of the present invention can reduce ripple noise in the output voltage regardless of the magnitude of the load current. The DC / DC converters according to each embodiment will be described below. Note that the DC / DC converters according to each embodiment are multi-phase DC / DC converters.

[0027] [First Embodiment] A DC / DC converter 10 according to the first embodiment of the present invention will be described with reference to Figures 1A to 1D. For the purposes of this description, Figures 7L and 7N, which show the current and voltage waveforms of the DC / DC converter 60B, a multi-phase DC / DC converter described in Patent Document 1 shown in Figure 7B, will be used for comparison.

[0028] First, the configuration of the DC / DC converter 10 according to this embodiment will be explained using Figure 1A. Figure 1A is a circuit diagram showing the circuit of the DC / DC converter 10 according to this embodiment. The DC / DC converter 10 according to this embodiment is a two-phase DC / DC converter.

[0029] As shown in Figure 1A, the DC / DC converter 10 according to this embodiment includes switching circuits 102, 103, and 104, inductors 105, 106, and 107, a capacitor 108, and a controller 110. The DC / DC converter 10 also has an input line 121 and an output line 122.

[0030] Input line 121 is a wire to which a DC voltage is supplied from input voltage source 101. The input voltage source 101 is connected to one end of input line 121. The input voltage source 101 supplies a DC voltage to input line 121. The input voltage source 101 is not particularly limited, but for example, it may be a power source that supplies a DC voltage converted from AC power supplied from a commercial power source, or it may be a battery. Switching circuits 102, 103, and 104 are connected in parallel to the other end of input line 121 via wiring.

[0031] Switching circuits 102, 103, and 104 are each composed of a CMOS inverter having a P-type MOS transistor Tr1 and an N-type MOS transistor Tr2. In each of switching circuits 102, 103, and 104, the source of the P-type MOS transistor Tr1 is connected to the other end of the input line 121 via wiring. The source of the N-type MOS transistor Tr2 is connected to a reference potential 111, which is ground potential, via wiring. Furthermore, the gates of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 are connected to the controller 110 via wiring. In switching circuit 102, the drains of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 are connected in common and connected to one end of the inductor 105 via wiring as output terminals. In switching circuit 103, the drains of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 are connected in common and connected to one end of the inductor 106 via wiring as output terminals. The drains of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 of the switching circuit 104 are connected in common and connected to one end of the inductor 107 via wiring as output terminals. Note that the switching circuits 102, 103, and 104 are not limited to those composed of CMOS inverters and may take other configurations.

[0032] The controller 110 is a control unit that controls the switching operation of the switching circuits 102, 103, and 104 to switch them on and off. The controller 110 controls the switching operation by controlling the voltage supplied to the gate of the P-type MOS transistor Tr1 and the gate of the N-type MOS transistor Tr2 of the switching circuits 102, 103, and 104.

[0033] Inductors 105, 106, and 107 each have inductance values ​​L1, L2, and L3, respectively. Here, inductance values ​​L1 and L2 are greater than inductance value L3. Inductance values ​​L1 and L2 may be the same or different from each other. The other ends of inductor 105, inductor 106, and inductor 107 are connected in common via wiring to one end of output line 122. In Figure 1A, the current 112 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 105 to one end of output line 122. The current 113 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 106 to one end of output line 122. The current 114 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 107 to one end of output line 122.

[0034] Output line 122 is a wiring that supplies a DC voltage to a load 109, such as a semiconductor device. The other end of output line 122 is connected to the load 109. A capacitor 108 is connected between output line 122 and the reference potential 111 via wiring. In Figure 1A, the current 115 indicated by the arrow represents the current generated in output line 122 before capacitor 108.

[0035] The DC / DC converter 10 switches the power supplied from the input voltage source 101 to the input line 121 on and off by the switching operation of switching circuits 102, 103, and 104 and sends it to the subsequent inductors 105, 106, and 107. Furthermore, the DC / DC converter 10 smooths the power sent to the inductors 105, 106, and 107 with a capacitor 108 and supplies a desired constant voltage to the load 109. At this time, the controller 110 controls the timing of the switching operation of switching circuits 102, 103, and 104.

[0036] The switching circuit 102 and inductor 105 constitute a first channel, which is a component unit that functions as a DC / DC converter. The switching circuit 103 and inductor 106 constitute a second channel, which is a component unit that functions as a DC / DC converter. The switching circuit 104 and inductor 107 constitute a third channel, which is a component unit that functions as a DC / DC converter. The DC / DC converter 10 has three channels: the first channel, the second channel, and the third channel.

[0037] When the load 109 is in a standby state or under light load conditions, only the first channel, which consists of the switching circuit 102 and the inductor 105, operates in the DC / DC converter 10. Under light load conditions, a first current flows through the load 109 as the load current, depending on the state of the load 109. Under light load conditions, the controller 110 controls the switching circuits 102, 103, and 104 so that only the first channel operates and the second and third channels are stopped.

[0038] On the other hand, in the case of a heavy load, such as when the load 109 is in a fully operational state, all channels of the DC / DC converter 10—the first channel, the second channel, and the third channel—operate. In the case of a heavy load, a second current, which is larger than the first current, flows through the load 109 depending on the state of the load 109. Specifically, in this case, the first channel, composed of the switching circuit 102 and inductor 105, and the second channel, composed of the switching circuit 103 and inductor 106, operate in phase. In contrast, the third channel, composed of the switching circuit 104 and inductor 107, operates with a phase difference of 180 degrees relative to the first and second channels. In the case of a heavy load, the controller 110 controls the switching circuits 102, 103, and 104 so that the first and second channels operate in phase, and the third channel operates with a phase difference of 180 degrees relative to the first and second channels.

[0039] It is preferable that the inductance value L1 of the first channel inductor 105, the inductance value L2 of the second channel inductor 106, and the inductance value L3 of the third channel inductor 107 satisfy the following equation (1). L3=(L1×L2) / (L1+L2)...Equation (1)

[0040] By satisfying equation (1) with inductance values ​​L1, L2, and L3, ripple noise can be more effectively reduced under heavy load conditions due to the cancellation effect between currents, as will be described later.

[0041] Next, the currents in each part of the DC / DC converter 10 according to this embodiment shown in Figure 1A, and the voltage of the load 109 will be explained using Figures 1B, 1C, and 1D. Figures 1B, 1C, and 1D show examples of the operating waveforms of the DC / DC converter 10 shown in Figure 1A. Figures 1B, 1C, and 1D show the waveforms of the currents 112, 113, and 114 of the inductors 105, 106, and 107 of each channel, the current 115 before the capacitor 108, and the voltage of the load 109 in the DC / DC converter 10. The waveforms shown in Figures 1B, 1C, and 1D are waveforms under heavy load conditions, such as when the load 109 is in full operation. Here, the circuit simulator PSpice from Cadence Design Systems was used for the waveform analysis of the current and voltage. For the waveform analysis circuit conditions, the input voltage source 101 was set to 3V, the inductance values ​​of inductors 105 and 106 were L1=L2=0.2μH, the inductance value L3 of inductor 107 was 0.1μH, and the switching frequency was 4MHz.

[0042] In the DC / DC converter 10, under heavy load conditions, switching circuits 102 and 103 operate synchronously, while switching circuit 104 operates with a phase difference of 180 degrees from switching circuits 102 and 103.

[0043] As shown in Figure 1B, currents 112 and 113 have waveforms with half the amplitude and a 180-degree phase difference compared to current 114. In Figure 1B, currents 112 and 113 overlap. Therefore, the combined current of currents 112 and 113 has the same amplitude as current 114 and a 180-degree phase difference. As a result of the cancellation effect between the currents, as shown in Figure 1C, current 115 has a smaller amplitude than the conventional current 612B shown in Figure 7M. Consequently, in this embodiment, ripple noise at the voltage of load 109 is reduced not only under light load conditions but also under heavy load conditions. While the ripple noise of the conventional DC / DC converter 60B shown in Figure 7N is 28.1mV, in this embodiment, as shown in Figure 1D, the ripple noise is reduced to 23.8mV. According to this embodiment, it is possible to reduce ripple noise under heavy load conditions without compromising the ripple noise reduction effect under light load conditions compared to the conventional method.

[0044] In this embodiment, under light load conditions, such as when the load 109 is in standby mode, the large inductance value of the inductor 105 keeps the current amplitude small, thereby reducing ripple noise. On the other hand, under heavy load conditions, such as when the load 109 is in full operation, the first and second channels operate synchronously. As a result, the amplitude of the combined current of the first and second channels becomes close to, or equal to, the amplitude of the current of the third channel, which operates in a different phase from the first and second channels. Therefore, under heavy load conditions, ripple noise can be reduced by the cancellation effect of the currents. Thus, according to this embodiment, ripple noise in the output voltage can be reduced regardless of the magnitude of the load current. In the waveform analysis described above, the inductances L1 and L2 were assumed to be the same value, but even if L1 and L2 have different values, ripple noise can be reduced as long as both are greater than L3. Also, since ripple noise under light load conditions can be reduced if the value of L1 is greater than the value of L2, it is preferable that the value of L1 is greater than the value of L2.

[0045] [Second Embodiment] A DC / DC converter 20 according to a second embodiment of the present invention will be described with reference to Figure 2. Figure 2 is a circuit diagram showing the circuit of the DC / DC converter 20 according to this embodiment.

[0046] As shown in Figure 2, the DC / DC converter 20 according to this embodiment includes switching circuits 202, 203, and 204, inductors 205, 206, 207, 208, and 209, a capacitor 210, and a controller 212. The DC / DC converter 20 also has an input line 221 and an output line 222.

[0047] Input line 221 is a wire that receives a DC voltage from input voltage source 201. Input voltage source 201 is connected to one end of input line 221. Input voltage source 201 is the same as input voltage source 101. Switching circuits 202, 203, and 204 are connected in parallel to the other end of input line 221 via wiring.

[0048] Switching circuits 202, 203, and 204 are constructed using CMOS inverters, similar to switching circuits 102, 103, and 104. In each of switching circuits 202, 203, and 204, the source of the P-type MOS transistor Tr1 is connected to the other end of the input line 221 via wiring. The source of the N-type MOS transistor Tr2 is connected to the reference potential 213, which is ground potential, via wiring. Furthermore, the gates of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 are connected to the controller 212 via wiring. In switching circuit 202, the drains of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 are connected in common and connected to one end of the inductor 205 via wiring as output terminals. In switching circuit 203, the drains of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 are connected in common and connected to one end of the inductor 207 via wiring as output terminals. The drains of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 of the switching circuit 204 are connected in common and connected to one end of the inductor 209 via wiring as the output terminals. Note that the switching circuits 202, 203, and 204 are not limited to those composed of CMOS inverters and may take other configurations.

[0049] The controller 212 is a control unit that controls the switching operation of the switching circuits 202, 203, and 204 to switch them on and off. The controller 212 controls the switching operation by controlling the voltage supplied to the gate of the P-type MOS transistor Tr1 and the gate of the N-type MOS transistor Tr2 of the switching circuits 202, 203, and 204.

[0050] Inductors 205, 206, 207, 208, and 209 have the same inductance value L. One end of inductor 206 is connected to the other end of inductor 205. One end of inductor 208 is connected to the other end of inductor 207. The other ends of inductor 206, inductor 208, and inductor 209 are connected in common via wiring to one end of output line 222. In Figure 2, the current 214 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 206 to one end of output line 222. The current 215 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 208 to one end of output line 222. The current 216 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 209 to one end of output line 222.

[0051] Output line 222 is a wiring that supplies a DC voltage to a load 211, such as a semiconductor device. The other end of output line 222 is connected to the load 211. A capacitor 210 is connected between output line 222 and reference potential 213 via wiring. In Figure 2, the current 217 indicated by the arrow represents the current generated in output line 222 before capacitor 210.

[0052] The DC / DC converter 20 switches the power supplied from the input voltage source 201 to the input line 221 on and off by the switching operation of switching circuits 202, 203, and 204, and sends it to the subsequent inductors 205, 206, 207, 208, and 209. Furthermore, the DC / DC converter 20 smooths the power sent to the inductors 205, 206, 207, 208, and 209 with a capacitor 210, and supplies a desired constant voltage to the load 211. At this time, the controller 212 controls the timing of the switching operation of switching circuits 202, 203, and 204.

[0053] Switching circuit 202 and inductors 205, 206 constitute a first channel, which is a component unit that functions as a DC / DC converter. Switching circuit 203 and inductors 207, 208 constitute a second channel, which is a component unit that functions as a DC / DC converter. Switching circuit 204 and inductor 209 constitute a third channel, which is a component unit that functions as a DC / DC converter. The DC / DC converter 20 has three channels: the first channel, the second channel, and the third channel.

[0054] In the DC / DC converter 20 according to this embodiment, the inductor 105 in the DC / DC converter 10 according to the first embodiment shown in Figure 1A is replaced with two inductors 205 and 206, and the inductor 106 is replaced with two inductors 207 and 208. In addition, in this embodiment, inductors 205, 206, 207, 208, and 209 all have the same inductance value L. For example, if L = 0.1 μH, the operating waveform of the DC / DC converter 20 according to this embodiment will be the same as the operating waveform shown in Figures 1B and 1C. That is, in this embodiment as well, the same ripple noise reduction effect as in the first embodiment can be obtained.

[0055] Thus, in this embodiment, the inductors 205 and 206 of the first channel are two identical inductors connected in series with the inductor 209 of the third channel. Similarly, the inductors 207 and 208 of the second channel are two identical inductors connected in series with the inductor 209 of the third channel.

[0056] Furthermore, this embodiment has the advantage that when inductors 205, 206, 207, 208, and 209 are constructed from components, they can be constructed from the same component. Generally, there is a limited lineup of inductor components with integer multiples of their values. In this embodiment, by connecting two inductor components with the same inductance value in series to double the value, it becomes easy to precisely match the amplitude of the combined current of the first and second channels with the amplitude of the current of the third channel.

[0057] Furthermore, the inductors for the first channel and the second channel may each consist of multiple inductors, not limited to two identical inductors, connected in series with the inductor 209 of the third channel. Even in this case, the effect of reducing ripple noise can still be obtained.

[0058] [Third Embodiment] Before describing the DC / DC converter 40 according to the third embodiment of the present invention, a comparative DC / DC converter 30, which is compared with the DC / DC converter 40 according to the third embodiment, will be described using Figures 3A to 3F. Figure 3A is a circuit diagram showing the circuit of the comparative DC / DC converter 30. The comparative DC / DC converter 30 is a 4-channel multi-phase DC / DC converter. Figures 3B to 3F are diagrams showing examples of operating waveforms of the comparative DC / DC converter 30.

[0059] As shown in Figure 3A, the DC / DC converter 30 in the comparative configuration includes switching circuits 302, 303, 304, and 305, inductors 306, 307, 308, and 309, a capacitor 310, and a controller 312. The DC / DC converter 30 also has an input line 321 and an output line 322.

[0060] Switching circuits 302, 303, 304, and 305 are constructed using CMOS inverters, similar to switching circuits 102, 103, and 104. In each of switching circuits 302, 303, 304, and 305, the source of the P-type MOS transistor Tr1 is connected to the other end of the input line 321 via wiring. The source of the N-type MOS transistor Tr2 is connected to the reference potential 313, which is ground potential, via wiring. Furthermore, the gates of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 are connected to the controller 312 via wiring. In addition, the drains of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 in switching circuit 302 are connected in common and connected to one end of the inductor 306 via wiring as output terminals. In switching circuit 303, the drains of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 are connected in common and connected to one end of the inductor 307 via wiring as output terminals. The drains of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 of switching circuit 304 are connected in common and connected to one end of inductor 308 via wiring as output terminals. The drains of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 of switching circuit 305 are connected in common and connected to one end of inductor 309 via wiring as output terminals.

[0061] The controller 312 is a control unit that controls the switching operation of the switching circuits 302, 303, 304, and 305 to switch them on and off. The controller 312 controls the switching operation by controlling the voltage supplied to the gate of the P-type MOS transistor Tr1 and the gate of the N-type MOS transistor Tr2 of the switching circuits 302, 303, 304, and 305.

[0062] Inductor 306 has an inductance value L'. Inductors 307, 308, and 309 each have an inductance value L that is smaller than the inductance value L'. The other ends of inductor 306, inductor 307, inductor 308, and inductor 309 are commonly connected via wiring to one end of output line 322. In Figure 3A, the current 314 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 306 to one end of output line 322. The current 315 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 307 to one end of output line 322. The current 316 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 308 to one end of output line 322. The current 317 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 309 to one end of output line 322.

[0063] Output line 322 is a wiring that supplies a DC voltage to a load 311, such as a semiconductor device. The other end of output line 322 is connected to the load 311. A capacitor 310 is connected between output line 322 and reference potential 313 via wiring. In Figure 3A, the current 318 indicated by the arrow represents the current generated in output line 322 before capacitor 310.

[0064] The DC / DC converter 30 switches the power supplied from the input voltage source 301 to the input line 321 on and off by the switching operation of switching circuits 302, 303, 304, and 305, and sends it to the subsequent inductors 306, 307, 308, and 309. Furthermore, the DC / DC converter 30 smooths the power sent to the inductors 306, 307, 308, and 309 with a capacitor 310 and supplies a desired constant voltage to the load 311. At this time, the controller 312 controls the timing of the switching operation of switching circuits 302, 303, 304, and 305.

[0065] Switching circuit 302 and inductor 306 constitute a first channel, which is a component unit that functions as a DC / DC converter. Switching circuit 303 and inductor 307 constitute a second channel, which is a component unit that functions as a DC / DC converter. Switching circuit 304 and inductor 308 constitute a third channel, which is a component unit that functions as a DC / DC converter. Switching circuit 305 and inductor 309 constitute a fourth channel, which is a component unit that functions as a DC / DC converter. The DC / DC converter 30 has four channels: the first channel, the second channel, the third channel, and the fourth channel.

[0066] When the load 311 is in a standby state or under light load conditions, only the first channel of the DC / DC converter 30, which consists of the switching circuit 302 and the inductor 306 having a large inductance value L', operates. At this time, the other channels are stopped. Under light load conditions, a first current flows through the load 311 as the load current, depending on the state of the load 311. Under light load conditions, the controller 312 controls the switching circuits 302, 303, 304, and 305 so that only the first channel operates and the second, third, and fourth channels are stopped.

[0067] On the other hand, under heavy load conditions, such as when load 311 is in full operation, all channels of the first, second, third, and fourth channels of the DC / DC converter 30 operate. However, in this case, each channel operates with a 90-degree phase difference. Under heavy load conditions, a second current, which is larger than the first current, flows through load 311 as the load current, depending on the state of load 311. Under heavy load conditions, the controller 312 controls the switching circuits 302, 303, 304, and 305 so that the first, second, third, and fourth channels operate with a 90-degree phase difference.

[0068] Next, the currents in each part of the DC / DC converter 30 and the voltage of the load 311 in the comparative configuration shown in Figure 3A will be explained using Figures 3B, 3C, 3D, 3E, and 3F. Figures 3B, 3C, 3D, 3E, and 3F show examples of the operating waveforms of the DC / DC converter 30 shown in Figure 3A. Here, the circuit simulator PSpice from Cadence Design Systems was used for the waveform analysis of the current and voltage. The circuit conditions for the waveform analysis were as follows: the voltage of the input voltage source 301 was 3V, the inductance value L' of the inductor 306 was 0.2μH, the inductance values ​​L of the inductors 307, 308, and 309 were 0.1μH, and the switching frequency was 4MHz.

[0069] Figures 3B and 3C show the waveforms of current 318 and the voltage of load 311 when only the first channel is operating under light load conditions, respectively. Figures 3D, 3E, and 3F show the waveforms of currents 314, 315, 316, 317, current 318, and the voltage of load 311 when all four channels are operating under heavy load conditions, respectively.

[0070] As can be seen in Figure 3D, under heavy load, although the phase difference between currents 314, 315, 316, and 317 is 90 degrees, only current 314 of inductor 306, which has a larger inductance value than the other inductors 307, 308, and 309, has a smaller amplitude. Therefore, as shown in Figure 3E, current 318, which is the combined current of currents 314, 315, 316, and 317, has a waveform with little cancellation effect. As a result, as shown in Figure 3F, the ripple noise at the voltage of load 311 was 22.1mV.

[0071] Next, a DC / DC converter 40 according to a third embodiment of the present invention will be described with reference to Figures 4A to 4F. Figure 4A is a circuit diagram showing the circuit of the DC / DC converter 40 according to this embodiment. Figures 4B to 4F are diagrams showing examples of operating waveforms of the DC / DC converter 40 according to this embodiment.

[0072] As shown in Figure 4A, the DC / DC converter 40 according to this embodiment includes switching circuits 402, 403, 404, 405, and 406, inductors 407, 408, 409, 410, and 411, a capacitor 412, and a controller 414. The DC / DC converter 40 also has an input line 431 and an output line 432.

[0073] Input line 431 is a wire that receives a DC voltage from input voltage source 401. Input voltage source 401 is connected to one end of input line 431. Input voltage source 401 is the same as input voltage source 101. Switching circuits 402, 403, 404, 405, and 406 are connected in parallel to the other end of input line 431 via wiring.

[0074] Switching circuits 402, 403, 404, 405, and 406 are composed of CMOS inverters, similar to switching circuits 102, 103, and 104. In each of switching circuits 402, 403, 404, 405, and 406, the source of the P-type MOS transistor Tr1 is connected to the other end of the input line 431 via wiring. The source of the N-type MOS transistor Tr2 is connected to the reference potential 415, which is ground potential, via wiring. Furthermore, the gates of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 are connected to the controller 414 via wiring. In addition, the drains of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 in switching circuit 402 are connected in common and connected to one end of the inductor 407 via wiring as output terminals. In switching circuit 403, the drains of the P-type MOS transistor Tr1 and the N-type MOS transistor Tr2 are connected in common and connected to one end of the inductor 408 via wiring as output terminals. The drains of the P-type MOS transistor Tr1 and N-type MOS transistor Tr2 of switching circuit 404 are connected in common and, as output terminals, are connected via wiring to one end of inductor 409. The drains of the P-type MOS transistor Tr1 and N-type MOS transistor Tr2 of switching circuit 405 are connected in common and, as output terminals, are connected via wiring to one end of inductor 410. The drains of the P-type MOS transistor Tr1 and N-type MOS transistor Tr2 of switching circuit 406 are connected in common and, as output terminals, are connected via wiring to one end of inductor 411. Note that switching circuits 402, 403, 404, 405, and 406 are not limited to those composed of CMOS inverters and may take other configurations.

[0075] Controller 414 is a control unit that controls the switching operation of switching circuits 402, 403, 404, 405, and 406 to switch them on and off. Controller 414 controls the switching operation by controlling the voltage supplied to the gate of the P-type MOS transistor Tr1 and the gate of the N-type MOS transistor Tr2 of switching circuits 402, 403, 404, 405, and 406.

[0076] Inductor 407 has an inductance value L1. Inductor 408 has an inductance value L2. Inductors 409, 410, and 411 each have the same inductance value L3. Inductance value L3 is smaller than inductance values ​​L1 and L2. Inductance values ​​L1 and L2 may be the same or different. The other end of inductor 407, the other end of inductor 408, the other end of inductor 409, the other end of inductor 410, and the other end of inductor 411 are connected in common via wiring to one end of output line 432. In Figure 4A, the current 416 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 407 to one end of output line 432. The current 417 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 408 to one end of output line 432. The current 418 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 409 to one end of output line 432. The current 419 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 410 to one end of output line 432. The current 420 indicated by the arrow represents the current generated in the wiring connecting the other end of inductor 411 to one end of output line 432.

[0077] Output line 432 is a wiring that supplies a DC voltage to a load 413, such as a semiconductor device. The other end of output line 432 is connected to the load 413. A capacitor 412 is connected between output line 432 and the reference potential 415 via wiring. In Figure 4A, the current 421 indicated by the arrow represents the current generated in output line 432 before capacitor 412.

[0078] The DC / DC converter 40 switches the power supplied from the input voltage source 401 to the input line 431 on and off by the switching operation of switching circuits 402, 403, 404, 405, and 406, and sends it to the subsequent inductors 407, 408, 409, 410, and 411. Furthermore, the DC / DC converter 40 smooths the power sent to the inductors 407, 408, 409, 410, and 411 with a capacitor 412, and supplies a desired constant voltage to the load 413. At this time, the controller 414 controls the timing of the switching operation of switching circuits 402, 403, 404, 405, and 406.

[0079] Switching circuit 402 and inductor 407 constitute a first channel, which is a component unit that functions as a DC / DC converter. Switching circuit 403 and inductor 408 constitute a second channel, which is a component unit that functions as a DC / DC converter. Switching circuit 404 and inductor 409 constitute a third channel, which is a component unit that functions as a DC / DC converter. Switching circuit 405 and inductor 410 constitute a fourth channel, which is a component unit that functions as a DC / DC converter. Switching circuit 406 and inductor 411 constitute a fifth channel, which is a component unit that functions as a DC / DC converter. The DC / DC converter 40 has five channels: the first channel, the second channel, the third channel, the fourth channel, and the fifth channel.

[0080] When the load 413 is in a standby state or under light load conditions, only the first channel of the DC / DC converter 40, which consists of the switching circuit 402 and the inductor 407 having a large inductance value L1, operates. At this time, the other channels are stopped. Under light load conditions, a first current flows through the load 413 as the load current, depending on the state of the load 413. Under light load conditions, the controller 414 controls the switching circuits 402, 403, 404, 405, and 406 so that only the first channel operates and the second, third, fourth, and fifth channels are stopped.

[0081] On the other hand, under heavy load conditions, such as when load 413 is in full operation, all channels of the DC / DC converter 40—the first, second, third, fourth, and fifth channels—operate. However, in this case, the first channel and the second channel, which consists of the switching circuit 403 and the inductor 408 having a large inductance value L2, operate in phase with each other. Meanwhile, the other channels, from the third to the fifth, operate with a phase difference of 90 degrees from the phase in which the first and second channels operate. Under heavy load conditions, a second current, larger than the first current, flows through load 413 as the load current, depending on the state of load 413. Under heavy load conditions, the controller 414 controls the switching circuits 402 and 403 so that the first and second channels operate in phase with each other. Furthermore, in this case, the controller 414 controls the switching circuits 404, 405, and 406 so that the third, fourth, and fifth channels operate with a phase shift of 90 degrees from the phase in which the first and second channels operate.

[0082] It is preferable that the inductance value L1 of the inductor 407 of the first channel, the inductance value L2 of the inductor 408 of the second channel, and the inductance values ​​L3 of the inductors 409, 410, and 411 of the third to fifth channels satisfy the following equation (2). L3=(L1×L2) / (L1+L2)...Equation (2)

[0083] By satisfying equation (2) with inductance values ​​L1, L2, and L3, ripple noise can be more effectively reduced under heavy load conditions due to the cancellation effect between currents, as will be described later.

[0084] Next, the currents in each part of the DC / DC converter 40 according to this embodiment shown in Figure 4A, and the voltage of the load 413 will be explained using Figures 4B, 4C, 4D, 4E, and 4F. Figures 4B, 4C, 4D, 4E, and 4F show examples of the operating waveforms of the DC / DC converter 40 shown in Figure 4A. Here, the circuit simulator PSpice from Cadence Design Systems was used for the waveform analysis of the current and voltage. As circuit conditions for waveform analysis, the voltage of the input voltage source 401 was set to 3V, the inductance values ​​L1 and L2 of inductors 407 and 408 were both 0.2μH, the inductance value L3 of inductors 409, 410, and 411 was 0.1μH, and the switching frequency was 4MHz.

[0085] Figures 4B and 4C show the waveforms of current 421 and the voltage of load 413 when only the first channel is operating under light load conditions, respectively. Figures 4D, 4E, and 4F show the waveforms of currents 416, 417, 418, 419, 420, current 421, and the voltage of load 413 when all five channels are operating under heavy load conditions, respectively.

[0086] When all five channels are operating under heavy load conditions, such as when load 413 is in full operation, currents 416 and 417 have waveforms with half the amplitude compared to currents 418, 419, and 420, as shown in Figure 4D. In Figure 4D, currents 416 and 417 overlap. Therefore, the combined current of currents 416 and 417 has the same amplitude as currents 418, 419, and 420, and the ripple noise is reduced due to the cancellation effect between the currents. Compared to the ripple noise of 22.1mV for the DC / DC converter 30 in the comparative configuration shown in Figure 3F, the ripple noise of the DC / DC converter 40 according to this embodiment is reduced to 13mV, as shown in Figure 4F.

[0087] Furthermore, when only the first channel is operating under light load, the ripple noise amplitude of the DC / DC converter 40 according to this embodiment is 17.1mV, as shown in Figure 4C. This result is the same as the result shown in Figure 3C for the DC / DC converter 30 in the comparative configuration.

[0088] Thus, according to this embodiment, ripple noise in the output voltage can be reduced regardless of the magnitude of the load current.

[0089] In this embodiment, the DC / DC converter 40 has been described as having fourth and fifth channels, each containing an inductor 410, 411 with the same inductance value as the third channel's inductor 409, but it is not limited to this. The DC / DC converter 40 can have N channels (N is an integer of 1 or more), each containing an inductor with the same inductance value as the third channel's inductor 409. The configuration of the N channels is the same as that of the fourth channel. In this case, the controller 414 controls the switching circuits of the first, second, and third channels as well as the N channels. As a result, under heavy load conditions, the controller 414 controls the switching circuits of each channel so that the third channel and the N channels operate with a phase shift of 360 / (N+2) degrees from the phase in which the first and second channels operate.

[0090] Furthermore, in this embodiment as well, similar to the second embodiment, the inductors for the first channel and the second channel may each consist of multiple inductors identical to the inductor for the third channel connected in series.

[0091] [Fourth Embodiment] A DC / DC converter according to a fourth embodiment of the present invention will be described with reference to Figures 5A to 5E. Figures 5A to 5E show the operating waveforms of the DC / DC converter according to this embodiment.

[0092] The configuration of the DC / DC converter according to this embodiment is the same as the configuration of the DC / DC converter 40 according to the third embodiment shown in Figure 4A. In this embodiment, a case where the circuit conditions differ from those of the fourth embodiment will be described.

[0093] Figures 5A, 5B, 5C, 5D, and 5E show the operating waveforms of the DC / DC converter 40 shown in Figure 4A, under the following circuit conditions. Here, the circuit simulator PSpice from Cadence Design Systems was used for the waveform analysis of the current and voltage. The circuit conditions for the waveform analysis were as follows: the voltage of the input voltage source 401 was 3V, the inductance value L1 of inductor 407 was 0.47μH, the inductance value L2 of inductor 408 was 0.13μH, and the inductance values ​​L3 of inductors 409, 410, and 411 were 0.1μH. The switching frequency was set to 4MHz.

[0094] Thus, in this embodiment, the inductor 407 of the first channel has a larger inductance value than the inductor 408 of the second channel.

[0095] Figures 5A and 5B show the waveforms of current 421 and load 413 voltage when only the first channel is operating under light load, respectively. Compared to the third embodiment shown in Figures 4B and 4C, in this embodiment, the ripple noise amplitude is reduced from 17.1mV to 7.4mV, as shown in Figure 5B, due to the effect of increasing the inductance value L1 of the first channel inductor from 0.2μH to 0.47μH.

[0096] On the other hand, Figures 5C, 5D, and 5E show the voltages of currents 416, 417, 418, 419, 420, current 421, and load 413, respectively, when all five channels are operating under heavy load. As shown in Figure 5C, currents 416 and 417 have different amplitudes but are in phase, but when their amplitudes are added together, they have the same amplitude as currents 418, 419, and 420. Therefore, the combined current of currents 416 and 417 and the other currents 418, 419, and 420 have the same amplitude with a 90-degree phase difference. As a result, due to the cancellation effect of the currents, current 421, which is the combined current of currents 416, 417, 418, 419, and 420, is reduced, as shown in Figure 5D. Consequently, the amplitude of the ripple noise in this embodiment is approximately the same as that of the third embodiment, which is 13mV, as shown in Figure 4F, but is 12.4mV, as shown in Figure 5E.

[0097] Thus, in this embodiment, ripple noise under light load conditions can be further reduced compared to the third embodiment.

[0098] In this embodiment as well, similar to the second embodiment, the inductors for the first channel and the second channel may each consist of multiple inductors identical to the inductor for the third channel, connected in series.

[0099] [Fifth Embodiment] An electronic device according to a fifth embodiment of the present invention will be described with reference to Figures 6A to 6C. Figure 6A is a cross-sectional view showing a digital camera 500, which is an imaging device as an example of an electronic device according to this embodiment. Figures 6B and 6C are a perspective view and a cross-sectional view showing a processing module 504 included in the digital camera 500, respectively. In this embodiment, a digital camera 500, which is an electronic device including any of the DC / DC converters 10, 20, and 40 according to the first to fourth embodiments described above, will be described.

[0100] As shown in Figure 6A, the digital camera 500, which is an imaging device as an example of the electronic equipment according to this embodiment, is, for example, a lens-interchangeable digital camera and has a camera body 501. A lens barrel (lens unit) 502 including a lens is detachably attached to the camera body 501. Note that the digital camera 500 is not limited to a lens-interchangeable type, and may be, for example, a lens-integrated type.

[0101] The camera body 501 comprises a housing 503, a processing module 504 which is a printed circuit board, and a sensor module 505 which is a printed circuit board. The processing module 504 and the sensor module 505 are located inside the housing 503. The processing module 504 and the sensor module 505 are electrically connected to each other via a cable 506. The processing module 504 and the sensor module 505 are examples of semiconductor modules, which are electronic modules.

[0102] The sensor module 505 includes an image sensor 5051, which is an image sensor, and a printed circuit board 5052. The image sensor 5051 is mounted on the printed circuit board 5052. The image sensor 5051 is, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device) image sensor. The image sensor 5051 has the function of converting light incident on it via the lens unit 502 into an electrical signal.

[0103] As shown in Figures 6B and 6C, the processing module 504 includes a semiconductor device 5041, which is, for example, an ASIC (Application Specific Integrated Circuit), a power supply circuit 5042, and a printed circuit board 5043. The semiconductor device 5041 and the power supply circuit 5042 are mounted on the printed circuit board 5043. The printed circuit board 5043 is, for example, a rigid substrate and is the component on which the semiconductor device 5041 and the power supply circuit 5042 are mounted. The semiconductor device 5041 is, for example, a digital signal processor and has the function of acquiring electrical signals from an image sensor 5051 and performing processing to correct the acquired electrical signals to generate image data. The power supply circuit 5042 is composed of one of the DC / DC converters 10, 20, or 40 according to the first to fourth embodiments. The power supply circuit 5042 converts a DC voltage supplied from a battery (not shown) to a predetermined voltage value and supplies it to the semiconductor device 5041.

[0104] In this embodiment, a digital camera 500 was described as an electronic device, but it is not limited to this. Any electronic device including any of the DC / DC converters 10, 20, or 40 can be a digital camera or any other electronic device.

[0105] This embodiment includes the following configuration. (Composition 1) An input line to which a DC voltage is supplied, Each channel includes a switching circuit and an inductor, and one end of the inductor is connected to the input line via the switching circuit, The other end of the inductor of the plurality of channels is connected to one end, and the load is connected to the output line at the other end, It includes a controller that controls the switching circuits of the plurality of channels, The aforementioned plurality of channels include at least a first channel, a second channel, and a third channel. The inductors of the first and second channels have a larger inductance value than the inductor of the third channel. When the current flowing through the load is the first current, the controller controls the switching circuits of the first to third channels such that only the first channel operates and the second and third channels are shut down. A DC / DC converter characterized in that, when the current flowing through the load is a second current that is larger than the first current, the controller controls the switching circuits of the first to third channels such that the first and second channels operate in the same phase and the third channel operates in a different phase from the first and second channels. (Configuration 2) The DC / DC converter according to configuration 1, characterized in that, when the current flowing through the load is a second current that is larger than the first current, the controller controls the switching circuits of the first to third channels so that the third channel operates with a phase difference of 180 degrees relative to the first and second channels. (Composition 3) The DC / DC converter according to configuration 1 or 2, characterized in that the inductance value L1 of the inductor of the first channel, the inductance value L2 of the inductor of the second channel, and the inductance value L3 of the inductor of the third channel satisfy the following equation (1). L3 = (L1 × L2) / (L1 + L2) ... (1) (Composition 4) The aforementioned multiple channels further include N channels (where N is an integer greater than or equal to 1), The DC / DC converter according to configuration 1, characterized in that the inductors of the N channels each have the same inductance value as the inductor of the third channel. (Composition 5) The DC / DC converter according to configuration 4, characterized in that, when the current flowing through the load is a second current that is larger than the first current, the controller controls the switching circuits of the first to third channels and the switching circuits of the N channels such that the first and second channels operate in phase, and the third channel and the N channels operate with a phase difference of 360 / (N+2) degrees from the phase in which the first and second channels operate. (Composition 6) The DC / DC converter according to configuration 4 or 5, characterized in that the inductance value L1 of the inductor of the first channel, the inductance value L2 of the inductor of the second channel, and the inductance value L3 of the inductor of the third channel satisfy the following equation (2). L3 = (L1 × L2) / (L1 + L2) ... (2) (Composition 7) The DC / DC converter according to any one of configurations 1, 2, and 4 to 6, characterized in that the inductor of the first channel has a larger inductance value than the inductor of the second channel. (Composition 8) The DC / DC converter according to any one of configurations 1 to 7, characterized in that the inductors of the first and second channels are each multiple inductors identical to the inductor of the third inductor, connected in series. (Composition 9) Components and A DC / DC converter according to any one of configurations 1 to 8 mounted on the aforementioned member and An electronic module characterized by having the following features. (Composition 10) The casing and The electronic module described in configuration 9, which is arranged inside the housing An electronic device characterized by having the following features. [Explanation of symbols]

[0106] 10, 20, 30, 40... DC / DC converters 101, 201, 301, 401, 601A, 601B... Input voltage sources 102, 103, 104, 202, 203, 204, 302, 303, 304, 305, 402, 403, 404, 405, 406, 602A, 603A, 602B, 603B... Switching circuits 105, 106, 107, 205, 206, 207, 208, 209, 306, 307, 308, 309, 407, 408, 409, 410, 411, 604A, 605A, 604B, 605B... Inductors 108, 210, 310, 412, 606A, 606B... Capacitors 109, 211, 311, 413, 607A, 607B...Load 110, 212, 312, 414, 608A, 608B... controllers 121, 221, 321, 431, 621A, 621B... Input lines 122, 222, 322, 432, 622A, 622B...output line

Claims

1. An input line to which a DC voltage is supplied, Each channel includes a switching circuit and an inductor, and one end of the inductor is connected to the input line via the switching circuit, The other end of the inductor of the plurality of channels is connected to one end, and the load is connected to the output line at the other end, It includes a controller that controls the switching circuits of the plurality of channels, The plurality of channels include at least a first channel, a second channel, and a third channel. The inductor of the first channel and the inductor of the second channel have larger inductance values ​​than the inductor of the third channel. When the current flowing through the load is the first current, the controller controls the switching circuits of the first channel, the second channel and the third channel so that only the first channel operates and the second channel and the third channel are stopped. A DC / DC converter characterized in that, when the current flowing through the load is a second current that is larger than the first current, the controller controls the switching circuits of the first channel, the second channel, and the third channel so that the first channel and the second channel operate in the same phase, and the third channel operates in a different phase from the first channel and the second channel.

2. The DC / DC converter according to claim 1, characterized in that the inductance value L1 of the inductor of the first channel, the inductance value L2 of the inductor of the second channel, and the inductance value L3 of the inductor of the third channel satisfy the following formula (1). L3=(L1×L2) / (L1+L2)...(1)

3. The DC / DC converter according to claim 1 or 2, characterized in that the inductor of the first channel has an inductance value that is larger than or equal to that of the inductor of the second channel.

4. The DC / DC converter according to claim 1 or 2, wherein, when the current flowing through the load is a second current that is greater than the first current, the controller controls the switching circuits of the first channel, the second channel and the third channel so that the third channel operates with a phase difference of 180 degrees relative to the first channel and the second channel.

5. The aforementioned plurality of channels further include N channels (where N is an integer greater than or equal to 1), The DC / DC converter according to claim 1 or 2, characterized in that each of the N inductors in the N channels has the same inductance value as the inductor in the third channel.

6. The DC / DC converter according to claim 5, characterized in that, when the current flowing through the load is a second current that is larger than the first current, the controller controls the switching circuits of the first channel, the second channel and the third channel and the N channels so that the first channel and the second channel operate in phase, and the third channel and the N channels operate with a phase difference of 360 / (N+2) degrees from the phase in which the first channel and the second channel operate.

7. The DC / DC converter according to claim 5, characterized in that the inductance value L1 of the inductor of the first channel, the inductance value L2 of the inductor of the second channel, and the inductance value L3 of the inductor of the third channel satisfy the following equation (2). L3=(L1×L2) / (L1+L2)...(2)

8. The DC / DC converter according to claim 6, characterized in that the inductance value L1 of the inductor of the first channel, the inductance value L2 of the inductor of the second channel, and the inductance value L3 of the inductor of the third channel satisfy the following formula (2). L3=(L1×L2) / (L1+L2)...(2)

9. The DC / DC converter according to claim 5, characterized in that the inductor of the first channel has a larger inductance value than the inductor of the second channel.

10. The DC / DC converter according to claim 1 or 2, characterized in that the inductors of the first channel and the second channel are each multiple inductors identical to the inductor of the third channel, connected in series.

11. The DC / DC converter according to claim 1 or 2, characterized in that the switching circuit is composed of a CMOS inverter.

12. Components and The DC / DC converter according to claim 1 or 2 mounted on the aforementioned member and An electronic module characterized by having the following features.

13. A printed circuit board and A semiconductor device mounted on the aforementioned printed circuit board, A power supply circuit mounted on the aforementioned printed circuit board and supplying a DC voltage to the aforementioned semiconductor device, It has, The electronic module is characterized in that the power supply circuit is composed of a DC / DC converter as described in claim 1 or 2.

14. The semiconductor device is a digital signal processor, The electronic module according to claim 13.

15. The casing and The electronic module according to claim 12, disposed inside the housing An electronic device characterized by having the following features.

16. Housing and The electronic module according to claim 13, disposed inside the housing An electronic device characterized by having the following features.

17. The electronic device according to claim 16, characterized in that it has a sensor module including an image sensor.

18. The electronic device according to claim 17, characterized in that the semiconductor device acquires an electrical signal from the image sensor and performs a process to correct the acquired electrical signal to generate image data.

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