Voltage converter

Abstract

The present application provides a voltage converter capable of obtaining a low-ripple and stable output voltage. The voltage converter includes: a capacitive voltage conversion circuit section that inputs an input voltage and converts the input voltage into an output voltage to output the output voltage; an output capacitor; an inductor connected in series between the capacitive voltage conversion circuit section and the output capacitor; a voltage detection section; and a control section. The capacitive voltage conversion circuit section includes a plurality of switches, at least one flying capacitor, and an intermediate capacitor provided at an output section. The voltage detection section detects a voltage of a node that is a connection point of the intermediate capacitor and the inductor, and the control section controls the switches based on a comparison between a detection result of the voltage detection and a threshold value, so that the switches are switched back and forth between at least two states.

Description

Technical Field

[0001] This invention relates to a voltage converter having a capacitive voltage conversion circuit. Background Technology

[0002] Voltage converters equipped with capacitive voltage conversion circuits, such as switched capacitor circuits or charge pump circuits, eliminate the need for inductive components like transformers, making miniaturization easier. Therefore, they can be considered suitable power supply devices for small, low-power applications.

[0003] Capacitive voltage converter circuits come in a variety of structures. Representative structures include the Dickson type and the series-parallel type. Other structures include the ladder type and the Fibonacci type. A capacitor network circuit, containing multiple capacitors and multiple switches, is controlled to switch back and forth between at least two connection states, thereby stepping down or boosting the input voltage to produce the output.

[0004] Patent Document 1 discloses a voltage converter that includes a capacitive voltage conversion circuit. The voltage converter described in Patent Document 1 is a charge pump circuit with an inductor connected between a typical charge pump circuit and an output capacitor.

[0005] The DC-DC converter in Patent Document 1 switches at a frequency above the resonant frequency determined by the capacitor of the capacitive power converter, the capacitor of the LC circuit, and the inductor, thereby reducing losses and improving voltage conversion efficiency.

[0006] Prior art literature

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 6521187

[0009] In a typical charge pump circuit where the inductor shown in Patent Document 1 is absent, charge is moved by switching the connection state between flying capacitors using a resistive switch. This forms a C-R-C circuit, and the current moving between the flying capacitors creates a large peak. Therefore, approximately half of the total energy moving between the flying capacitors is lost.

[0010] On the other hand, in the voltage converter described in Patent Document 1, by providing an inductor and satisfying the resonance condition formed therein, the loss associated with the charge movement is greatly reduced, and high-efficiency conversion can be achieved.

[0011] In the voltage converter described in Patent Document 1, the same resonant frequency is formed in the first connection state and the second connection state, so that a more stable resonant condition can be obtained, and the voltage conversion efficiency can be improved by operating at a switching frequency exceeding the resonant frequency.

[0012] In the voltage converter described in Patent Document 1, the voltage is transformed by switching the connection state of the flying capacitor using a switch, thus generating ripple in the output voltage. The output capacitor smooths this ripple. Therefore, it is important that the capacitance of the output capacitor is greater than the capacitance of the flying capacitor that generates the ripple voltage.

[0013] The intermediate capacitor stabilizes the voltage preceding the inductor; therefore, increasing the capacitance of the intermediate capacitor can suppress its ripple voltage. On the other hand, if the capacitance of the intermediate capacitor is larger than that of the flying capacitor, the voltage conversion efficiency decreases. This is because the insertion of an inductor suppresses the charging current ripple from the flying capacitor to the output capacitor. Therefore, if the capacitance of the intermediate capacitor is increased, a large current flows through it, making the inclusion of an inductor pointless. Therefore, the capacitance of the intermediate capacitor should be smaller than that of the flying capacitor. This allows for a moderate amount of ripple without reducing voltage conversion efficiency. Summary of the Invention

[0014] The problem that the invention aims to solve

[0015] Therefore, the object of the present invention is to provide a voltage converter that can obtain a low ripple and stable output voltage.

[0016] Technical solutions for solving the problem

[0017] (A) The voltage converter of the present invention includes: a capacitive voltage conversion circuit section for receiving an input voltage and converting the input voltage into an output voltage for output; an output capacitor; an inductor connected in series between the capacitive voltage conversion circuit section and the output capacitor; a voltage detection section; and a control section. Furthermore, the capacitive voltage conversion circuit section includes a plurality of switches, at least one flying capacitor, and an intermediate capacitor disposed in the output section. The voltage detection section detects the voltage at a node that serves as the connection point between the intermediate capacitor and the inductor. The control section controls the switches based on a comparison between the voltage at the node and a threshold voltage, causing the switches to switch back and forth between at least two states.

[0018] (B) The voltage converter of the present invention comprises: a plurality of capacitive voltage conversion circuit sections for receiving an input voltage and converting the input voltage to output; a common output capacitor; inductors connected in series between the plurality of capacitive voltage conversion circuit sections and the output capacitor; and a voltage detection section and a control section provided for each of the capacitive voltage conversion circuit sections. Furthermore, each capacitive voltage conversion circuit section includes a plurality of switches, at least one flying capacitor, and an intermediate capacitor provided in the output section. The plurality of voltage detection sections respectively detect the voltage at a node that serves as the connection point between the intermediate capacitor and the inductor. The control section provided for each of the capacitive voltage conversion circuit sections controls the switches provided for each of the capacitive voltage conversion circuit sections based on a comparison between the detection results of the voltage detection sections and a threshold, causing the switches to switch back and forth between at least two states.

[0019] Invention Effects

[0020] According to the present invention, a voltage converter capable of obtaining a low ripple and stable output voltage can be constructed. Attached Figure Description

[0021] Figure 1 This is a block diagram of the voltage converter 1 according to the first embodiment.

[0022] Figure 2 This is an example of a circuit diagram for voltage converter 1.

[0023] Figure 3 (A) is Figure 2 The circuit shown is the circuit diagram for the first connection state Φ1. Figure 3 (B) is in Figure 3 The circuit diagram shown in (A) is for a circuit where the power supply impedance is high and C10 >> C11. Figure 3 (C) is in Figure 3 The circuit diagram shown in (A) is the circuit diagram with sufficiently low power supply impedance.

[0024] Figure 4 It is Figure 3 (B) or Figure 3 The circuit diagram shown in (C) is a further synthesized circuit diagram.

[0025] Figure 5 This is a waveform diagram showing the relationship between the resonant frequency Fh, the switching period T, and the switching current Is in voltage converter 1.

[0026] Figure 6 It is a waveform diagram showing the relationship between the resonant frequency, switching period, and switching current in a voltage converter.

[0027] Figure 7 (A) Figure 7 (B) Figure 7 (C) Figure 7 (D) Figure 7 (E) is a timing diagram illustrating an example of the relationship between the periods of the first connection state Φ1 and the second connection state Φ2 in voltage converter 1.

[0028] Figure 8 The waveforms are of the voltage Vx at node Nx, which is the connection point between intermediate capacitor Cx and inductor Lx in voltage converter 1, and the voltage waveform of the comparison object.

[0029] Figure 9 This is a circuit diagram of the voltage converter 2 according to the second embodiment.

[0030] Figure 10 This is a block diagram of the voltage converter 3 according to the third embodiment.

[0031] Figure 11 This is a block diagram of the voltage converter according to the fourth embodiment.

[0032] Figure 12 This is a block diagram of another voltage converter involved in the fourth embodiment.

[0033] Figure 13 This is a block diagram of the voltage converter according to the fifth embodiment.

[0034] Figure 14 (A) is a waveform diagram showing the relationship between the voltage Vx at node Nx and the threshold voltage Vth. Figure 14 (B) is a waveform diagram showing the relationship between the output voltage Vout and the threshold voltage in the case where the output voltage Vout is detected and fed back as in conventional voltage converters.

[0035] Figure 15 This is a waveform diagram of a voltage converter where the threshold voltage Vth changes in the opposite direction to the change in node voltage Vx over time, starting from the inversion of the comparison result between the node voltage Vx and the threshold voltage Vth.

[0036] Explanation of reference numerals in the attached figures

[0037] C10, C11, C12: Flying capacitors;

[0038] CIN: Composite capacitor;

[0039] COUT: Capacitor;

[0040] Cout: Output capacitor;

[0041] Cx: Intermediate capacitor;

[0042] Ih: Resonant current;

[0043] Iin: Input current;

[0044] Iout: Output current;

[0045] Is: Switching current;

[0046] Lx: Inductor;

[0047] Nx: Node;

[0048] Q11: Rectifier switching element;

[0049] Q12: Converter switching components;

[0050] RL: Load;

[0051] S111, S112, S113, S114, S115, S116, S117: Switching elements;

[0052] S121, S122, S123, S124, S125, S126, S127: Switching elements;

[0053] Th: Resonance period;

[0054] TN: On-time;

[0055] Vin: Input voltage;

[0056] Vout: Output voltage;

[0057] Vth: Threshold voltage;

[0058] Vx: Voltage at the node;

[0059] 1, 1A, 1B, 1C: Voltage converters;

[0060] 2, 3: Voltage converter;

[0061] 9, 10: Capacitive voltage conversion circuit section;

[0062] 11: First capacitive voltage conversion circuit;

[0063] 12: Second capacitive voltage conversion circuit;

[0064] 13: Voltage detection unit;

[0065] 13A: Reference voltage generation circuit;

[0066] 13B: Comparator circuit;

[0067] 17: Control Department;

[0068] 20: LC circuit;

[0069] 30: Inductive buck converter;

[0070] 31: Driver;

[0071] 101: Input terminal;

[0072] 201: Output terminal. Detailed Implementation

[0073] The following describes various methods of implementing the present invention with reference to the figures and several specific examples. In each figure, the same reference numerals are used to label the same parts. For ease of explanation and understanding, the embodiments are shown in multiple ways, but partial substitutions or combinations of the structures shown in different embodiments are possible. From the second embodiment onwards, descriptions of matters common to the first embodiment are omitted, and only the differences are described. In particular, the same effects based on the same structure will not be mentioned repeatedly in each embodiment.

[0074] Implementation Method 1

[0075] Figure 1 This is a block diagram of the voltage converter 1 according to the first embodiment. The voltage converter 1 includes: a capacitive voltage conversion circuit section 10, which receives an input voltage Vin and converts the input voltage Vin into an output voltage Vout for output; an output capacitor Cout; an inductor Lx connected in series between the capacitive voltage conversion circuit section 10 and the output capacitor Cout; an intermediate capacitor Cx disposed at the output section of the capacitive voltage conversion circuit section 10; a voltage detection section 13; and a control section 17.

[0076] The voltage detection unit 13 detects the voltage Vx at node Nx, which is the connection point of the intermediate capacitor Cx and the inductor Lx. The inductor Lx and the output capacitor Cout constitute the LC circuit 20. The output capacitor Cout corresponds to the "output capacitor" in this invention. Furthermore, the inductor Lx corresponds to the "inductor" in this invention.

[0077] Voltage converter 1 steps down the input voltage Vin of the input power supply connected to input terminal 101 to an output voltage Vout and supplies it to the load RL. Input current Iin is input to voltage converter 1, and output current Iout is output to the load RL.

[0078] Figure 2This is an example of a circuit diagram for voltage converter 1. The capacitive voltage conversion circuit section 10 includes a first capacitive voltage conversion circuit 11 and a second capacitive voltage conversion circuit 12 connected in parallel. The first capacitive voltage conversion circuit 11 and the second capacitive voltage conversion circuit 12 have the same structure. The first capacitive voltage conversion circuit 11 is equipped with multiple flying capacitors C10, C11, C12, an intermediate capacitor Cx, and multiple switching elements S111, S112, S113, S114, S115, S116, and S117. The second capacitive voltage conversion circuit 12 is equipped with multiple flying capacitors C10, C11, C12, an intermediate capacitor Cx, and multiple switching elements S121, S122, S123, S124, S125, S126, and S127.

[0079] The capacitive voltage conversion circuit section 10 is configured by mounting integrated circuits, surface-mount components, and other devices onto a circuit board. The inductor Lx and the output capacitor Cout are, for example, separate surface-mount components mounted on the circuit board. The flyback capacitors C10, C11, C12, the intermediate capacitor Cx, and the output capacitor Cout are, for example, ceramic capacitors mounted on the circuit board. In this structure, the use of large-capacitance ceramic capacitors makes it easier to reduce the mounting area.

[0080] The control unit 17 performs interleaved control on the first capacitive voltage conversion circuit 11 and the second capacitive voltage conversion circuit 12. Figure 2 In the example shown, the first connection state Φ1 is defined as when switch elements S111, S114, S115, S116, S122, S123, and S127 are in the ON state and switch elements S112, S113, S117, S121, S124, S125, and S126 are in the OFF state. Furthermore, the second connection state Φ2 is defined as when switch elements S111, S114, S115, S116, S122, S123, and S127 are in the OFF state and switch elements S112, S113, S117, S121, S124, S125, and S126 are in the ON state.

[0081] Alternatively, all switching elements can be set to the off state, thereby establishing a third connection state to avoid unwanted power consumption caused by useless currents such as through current. This third state can be used as an intermediate state when transitioning from the first connection state to the second connection state or from the second connection state to the first connection state. In this embodiment, the third connection state is omitted for the sake of simplicity.

[0082] Figure 3 (A) is Figure 2 The circuit shown is the circuit diagram for the first connection state Φ1.

[0083] Figure 3 (B) is a circuit diagram for the following situation, namely, in Figure 3 In the circuit shown in (A), the power supply has a high impedance (with a value that cannot be ignored), and when the capacitances of capacitors C10 and C11 are represented by C10 and C11 respectively, it is not C10 >> C11.

[0084] Figure 3 (C) is in Figure 3 The circuit diagram shown in (A) illustrates the case where the impedance of the power supply is sufficiently low. Furthermore, Figure 3 (C) is also the circuit diagram when the capacitance of capacitor C10 is sufficiently large compared to the capacitance of capacitor C11 (C10 >> C11). That is, even if the impedance of the power source is a non-negligible value, if C10 >> C11, then capacitor C10 makes the impedance of the power source practically invisible; therefore, this state can be equivalently represented by... Figure 3 The circuit shown in (C) is used to represent this.

[0085] In addition, Figure 3 (B) Figure 3 In (C), the on-resistance RON of each switching element is assumed to be a value that can be ignored.

[0086] Figure 4 It is Figure 3 (B) or Figure 3 The circuit diagram shown in (C) is a further synthesis of the circuit diagram. Like in this... Figure 4 As indicated, by Figure 1 The capacitive voltage conversion circuit 10 and the LC circuit 20 shown constitute an LC resonant circuit. This LC resonant circuit has a combined capacitor CIN at the input terminal of the inductor Lx and a capacitor COUT, primarily based on capacitor Cout, at the output terminal of the inductor Lx. A resonant current Ih flows through this LC resonant circuit.

[0087] When the power supply impedance is high and the capacitance of capacitor C10 is small (not C10 >> C11), that is, when it is equivalent to passing through... Figure 3 In the case of (B), the capacitance Cin of the composite capacitor CIN can be expressed by the following mathematical formula 1.

[0088] [Mathematical Expression 1]

[0089]

[0090] Furthermore, in the case of an ideal power supply with sufficiently low impedance, or in the case where even if the impedance of the power supply is a non-negligible value but C10 >> C11, that is, in the case where the equivalent circuit can pass through... Figure 3When represented by (C), the capacitance Cin of the composite capacitor CIN can be expressed by the following mathematical formula 2.

[0091] [Mathematical Expression 2]

[0092]

[0093] also, Figure 4 The resonant frequency Fh of the resonant circuit shown can be obtained by the following mathematical formula 3.

[0094] [Mathematical Expression 3]

[0095]

[0096] Furthermore, for ease of understanding, the first capacitive voltage conversion circuit 11 and the second capacitive voltage conversion circuit 12 are represented as separate circuits, but the capacitors connected in parallel (double-connected capacitors) can be composed of a single capacitor. For example, capacitors C10, C10, Cx, and Cx can each be individually represented. Similarly, switches in a double-connection configuration can be shared. This reduces the number of components.

[0097] Figure 5 This is a waveform diagram showing the relationship between the resonant frequency Fh, the switching period T, and the switching current Is in voltage converter 1. Here, the sum of the period T1 of the first connection state Φ1 and the period T2 of the second connection state Φ2 is taken as the switching period T.

[0098] The switching frequency Fs is the reciprocal of the switching period T. Without considering the blanking time required to turn off all switches, T = T1 + T2, and Fs = 1 / T holds true. For simplicity, this explanation will be provided under these conditions. Figure 5 The switching current Is in the figure simulates the current waveform flowing through the switching element S111. Here, the direction toward the output is set to positive.

[0099] When power is transferred from the capacitive voltage conversion circuit section 10 to the capacitive or resistive load RL, the resonant frequency Fh becomes very high compared to the switching frequency Fs (Fh >> Fs), such as Figure 5 As shown, a very large peak current is generated, thus increasing losses. On the other hand, if an inductor Lx is connected to the output terminal 201, inductive properties occur, and the resonant frequency Fh becomes slightly higher than the switching frequency Fs (Fh > Fs), as... Figure 5 As shown, the switching current Is oscillates to the negative polarity during this period. Furthermore, if the inductance of inductor Lx is increased, the resonant frequency Fh becomes lower than the switching frequency Fs (Fh < Fs), as... Figure 5As shown, the switching current Is shifts at a very small value during the period when no negative current is generated.

[0100] The output current of the capacitive voltage converter circuit section 10 is the total current flowing through each switch, and is calculated based on the average value of this total current. Regarding... Figure 5 Under the three conditions, when the total output current of voltage converter 1 is Iout, the average current value of the waveforms showing the current of switching element S111 is approximately one-sixth of Iout. Therefore, in Figure 5 When the current waveform oscillates negatively, meaning that a reverse current flows, an equal positive current needs to be added during the period T1 of the first connection state Φ1. Therefore, the absolute value of the current flowing through the switch increases, the heat loss of the switch also increases, and as a result, the efficiency decreases.

[0101] According to the circuit structure of this embodiment, the current caused by the LC resonance phenomenon can be effectively identified by observing the current flowing through the inductor. An example of its waveform is shown below. Figure 6 .exist Figure 6 In the above, the average current value of each waveform is equal to the output current of the voltage converter. On the other hand, based on the relationship between the resonant frequency Fh and the switching frequency Fs, and... Figure 5 Similarly, each waveform has a different shape and wave height value.

[0102] Regarding the resonant period Th, which is the reciprocal of the resonant frequency Fh, especially under the condition that T1 during the first connection state Φ1 is greater than half of the resonant period Th (Th / 2), the current flows in the opposite direction within a certain interval. In this structure, there are two connection states for power transmission, therefore, the period T1 of the first connection state Φ1 must satisfy the condition that T1 < Th / 2, which is less than half of the resonant period Th (Th / 2), the reciprocal of the resonant frequency Fh. Furthermore, the period T2 of the second connection state Φ2 must satisfy the condition that T2 < Th / 2, which is less than half of the resonant period Th (Th / 2), the reciprocal of the resonant frequency Fh. However, this is not the case in non-connection states such as dead time.

[0103] As described above, when the resonant frequency Fh is higher than the switching frequency Fs, the current through the switching element increases due to both reverse and forward currents, leading to increased losses. The heat loss PLS of the switching element is obtained by integrating the value of the switch's on-resistance RON multiplied by the square of the current Is flowing through the switching element over time. In other words, simply reducing current peaks using filters is not sufficient. Increased losses may occur due to the presence of inductors or parasitic inductance. By appropriately controlling the on-time of the switching element based on the estimation of the resonant frequency Fh according to this embodiment, voltage conversion efficiency can be improved.

[0104] Therefore, in this embodiment, the control unit 17 is configured to switch at a switching frequency Fs that is higher than or equal to the resonant frequency Fh determined by the capacitor of the capacitive voltage converter circuit 10, the capacitor of the LC circuit 20, and the inductor. In other words, it switches at a switching period Th / 2 or less, where the conduction period TN is half of the resonant period Th. Here, N is an integer representing the connection state of the capacitive voltage converter circuit; in this example, TN is T1 or T2.

[0105] When the switching frequency Fs is lower than the resonant frequency Fh, a reverse current flows, which in turn carries an equal forward current, resulting in a decrease in voltage conversion efficiency. When the switching frequency Fs is higher than the resonant frequency Fh, no reverse current flows, thus improving voltage conversion efficiency. If we also consider the time axis, we can say that as long as the switching period T is shorter than half of the resonant period Th, the efficiency can be maximized.

[0106] Figure 7 (A) Figure 7 (B) Figure 7 (C) Figure 7 (D) Figure 7 (E) is a timing diagram illustrating an example of the relationship between the periods of the first connection state Φ1 and the second connection state Φ2 in voltage converter 1. Figure 7 Example (A) is as follows: the duration of the first connection state Φ1 is equal to the duration of the second connection state Φ2, and the switching period T is the sum of the durations T1 and T2 of the first connection state Φ1 and the second connection state Φ2. That is, the duty cycle of the switch is 0.5. In this case, the switching frequency Fs is higher than the resonant frequency Fh. On the other hand, as... Figure 7 (B) Figure 7 (C) Figure 7 As shown in (D), it is also possible to insert blank times such as dead time, thereby making the conduction duty cycle less than 50%. In this case, as mentioned earlier, the switching period T is shorter than half of the resonant period Th.

[0107] The method of improving efficiency by varying the switching frequency according to the load conditions of the voltage converter is widely used in inductive switching regulators. In this embodiment, for example, under low load conditions, reducing the switching frequency can also reduce the losses involved in switching drive and improve efficiency. Even in such cases, it is important to maintain the switching period and resonant period in the aforementioned relationship.

[0108] In addition to the methods mentioned above, there are the following methods, namely, like Figure 7 As in (E), the duration of the first connection state Φ1 and the duration of the second connection state Φ2 are lengthened respectively, thereby keeping the duty cycle of the switch constant at 0.5 and lengthening the switching period. This control method can be implemented within a range that maintains the relationship between the switching frequency Fs and the resonant frequency Fh.

[0109] Figure 8 The waveform of voltage Vx in the diagram is the waveform of the voltage Vx at node Nx, which serves as the connection point between the intermediate capacitor Cx and the inductor Lx in voltage converter 1. Figure 8 In the middle, the waveform of voltage Vout1 is... Figure 1 The waveform of the output voltage Vout in the voltage converter 1 shown is given without the inductor Lx. Furthermore, in... Figure 8 In the middle, the waveform of voltage Vout2 is... Figure 1 The waveform of the output voltage Vout in the voltage converter 1 shown is given when the inductor Lx and the output capacitor Cout are present.

[0110] Without the inductor Lx, the voltage ripple of the output voltage Vout (the waveform of voltage Vout1) is small. Therefore, if the output voltage Vout is used as feedback information and switching is performed by comparing it with a threshold, stable feedback operation cannot be achieved.

[0111] When the voltage detection unit 13 detects the output voltage Vout after it has been smoothed by the output capacitor Cout, the voltage ripple is small, as shown in the waveform of voltage Vout2. Therefore, if the output voltage Vout is used as feedback information and switching is performed by comparing it with a threshold, stable feedback operation cannot be achieved. In particular, the voltage ripple is even smaller in the region where the output current is small, making the feedback operation even more unstable.

[0112] In contrast, in this embodiment, the voltage ripple of the voltage Vx at node Nx, which is the connection point between the intermediate capacitor Cx and the inductor Lx, is very large. Therefore, if the voltage Vx at node Nx, which is the connection point between the intermediate capacitor Cx and the inductor Lx, is used as feedback information and switching is performed by comparing it with a threshold, a very stable feedback operation can be achieved.

[0113] Furthermore, the amplitude of voltage Vx is proportional to the load current. Regarding feedback control, when the voltage Vx at node Nx drops by a specified value (e.g., 100mV), feedback control is applied, thereby raising the voltage Vx at node Nx, which serves as the connection point between the intermediate capacitor Cx and the inductor Lx. The larger the load current, the faster the current is drawn in, thus the current decreases more rapidly, and the output voltage Vout rises more quickly. In other words, the switching frequency increases. Conversely, when the load current is small, the switching frequency decreases.

[0114] Figure 1 The control unit 17 shown switches the switch at a frequency set according to a condition including the highest and lowest frequencies of the switching frequency. Furthermore, the lowest frequency is set to a frequency lower than the resonant frequency determined by at least one flying capacitor, intermediate capacitor Cx, inductor Lx, and output capacitor Cout. This is because, when the output current is less than a certain threshold, the proportion of losses generated when driving the switching element increases compared to the losses generated by the current flowing through the circuit in the opposite direction. In other words, under this condition, efficiency is better when the switch is driven at a frequency lower than the resonant frequency. Moreover, the lowest frequency is set to a frequency higher than the audible frequency. Therefore, the generation of audible noise caused by switching at an audible frequency can be suppressed.

[0115] also, Figure 1 The control unit 17 shown switches the switch at a frequency set according to conditions including the highest and lowest frequencies of the switching frequency. Furthermore, the highest frequency is set to a frequency higher than that of at least one flying capacitor, intermediate capacitor Cx, inductor Lx, and output capacitor C. o The frequency determined by ut is higher than the resonant frequency. This is because, when the output current exceeds a certain threshold, the losses caused by the current flowing through the circuit in the opposite direction become proportional to the losses generated when driving the switching element. In other words, under this condition, efficiency is better when the switch is driven at a frequency higher than the resonant frequency. Furthermore, the highest frequency is set to a frequency lower than the upper limit of the frequency at which the switch can be driven. As a result, switching becomes possible within the frequency band at which the switch can be driven.

[0116] Implementation Method 2

[0117] In the second embodiment, a voltage converter that partially shares the structure of a flying capacitor and a switch is illustrated.

[0118] Figure 9This is a circuit diagram of the voltage converter 2 according to the second embodiment. The voltage converter 2 is configured such that, instead of being entirely dual-structured, it is partially dual-structured and operates in an alternating manner. If compared with... Figure 2 In comparison, it becomes clear that the flying capacitor C10 is shared by the first capacitive voltage conversion circuit 11 and the second capacitive voltage conversion circuit 12. The intermediate capacitor Cx is also shared by the first capacitive voltage conversion circuit 11 and the second capacitive voltage conversion circuit 12. Switching elements S112, S114, S115, and S117 generate positive and negative pulses; therefore, by resetting the connection order of these switching elements, shared access can be achieved.

[0119] Third Implementation Method

[0120] In the third embodiment, a voltage converter equipped with an inductive converter is illustrated.

[0121] Figure 10 This is a block diagram of the voltage converter 3 according to the third embodiment. In this embodiment, the inductive buck converter 30 is connected to the stage following the capacitive voltage conversion circuit section 10. The LC circuit 20 is composed of the inductor Lx included in the inductive buck converter 30 and the output capacitor Cout.

[0122] The inductive buck converter 30 includes a rectifier switch element Q11, a commutation switch element Q12, an inductor Lx, a capacitor Cout, and a driver 31. The rectifier switch element Q11 is a p-type MOSFET. The commutation switch element Q12 is an n-type MOSFET. The driver 31 alternately switches the rectifier switch element Q11 and the commutation switch element Q12. Alternatively, the buck converter 30 can be configured with multiple circuits and connected in parallel for interleaved operation.

[0123] Implementation Method 4

[0124] In the fourth embodiment, a voltage converter having multiple capacitive voltage conversion circuit sections and a main part having multiple capacitive voltage conversion circuit sections are illustrated.

[0125] Figure 11 This is a block diagram of a voltage converter according to the fourth embodiment. The voltage converter includes three voltage converters 1A, 1B, and 1C. Each of the voltage converters 1A, 1B, and 1C includes a capacitive voltage conversion circuit section 10, a voltage detection section 13, a control section 17, an inductor Lx, and an output capacitor Cout.

[0126] The inputs of the three capacitive voltage converter circuit sections 10 are connected in parallel, and the input terminal 101 of the input voltage Vin is common. Furthermore, the output capacitor Cout is connected in parallel, and the output terminal 201 of the output voltage Vout is common.

[0127] In this way, even when multiple voltage converters 1A, 1B, and 1C are connected in parallel, the voltage detection unit 13 of voltage converter 1A detects the voltage of the intermediate capacitor Cx at the output of the capacitive voltage conversion circuit section 10 of voltage converter 1A. Similarly, the voltage detection unit 13 of voltage converter 1B detects the voltage of the intermediate capacitor Cx at the output of the capacitive voltage conversion circuit section 10 of voltage converter 1B, and the voltage detection unit 13 of voltage converter 1C detects the voltage of the intermediate capacitor Cx at the output of the capacitive voltage conversion circuit section 10 of voltage converter 1C.

[0128] Here, assuming each voltage converter switches its state based on a comparison between its output voltage Vout and a threshold voltage, and that the threshold voltage has an error for each voltage converter, only the voltage converter with the higher threshold voltage compared to the output voltage Vout will operate. In other words, in conventional structures, because a common output voltage Vout with low ripple is detected, the load rate of the voltage converter with the higher threshold voltage increases, disrupting the balance among multiple voltage converters. While switching operations at the same frequency are possible without a misalignment in the comparison mechanism, this is impractical when individually configured voltage converters are arranged in parallel. Furthermore, if the capacitance of each capacitor in a capacitive voltage converter circuit deviates, the charge transfer capability will also deviate, resulting in deviations in the output current between the voltage converters.

[0129] On the other hand, according to this embodiment, instead of detecting the common output voltage Vout, the voltage Vx at the node where the intermediate capacitor Cx and inductor Lx of each voltage converter are connected is detected and fed back (to control the switching of the capacitive voltage conversion circuit section 10). Therefore, each converter operating in parallel operates in a balanced and good manner. That is, in this embodiment, each voltage converter 1A, 1B, and 1C is separated by the inductor Lx, and the voltage Vx decreases at a rate determined by the discharge rate, which is determined by the flying capacitor, intermediate capacitor Cx, and resistance component of the switch of each voltage converter 1A, 1B, and 1C. Therefore, based on the ripple voltage corresponding to the characteristics of each of the parallel-connected voltage converters 1A, 1B, and 1C, each can operate at an optimal operating frequency corresponding to its own load. As a result, even if there are capacitance deviations and voltage conversion capability differences among the capacitors of each voltage converter in parallel operation, a balance of losses and heat can be achieved at each operating frequency.

[0130] Figure 12 This is a block diagram of another voltage converter according to this embodiment. The voltage converter includes: three capacitive voltage conversion circuit sections 10, which receive an input voltage Vin and convert the input voltage Vin to output a voltage; a single (common) output capacitor Cout; inductors Lx, connected in series between the three capacitive voltage conversion circuit sections 10 and the output capacitor Cout; and a voltage detection section 13 and a control section 17, provided for each capacitive voltage conversion circuit section 10.

[0131] The capacitive voltage conversion circuit 10 includes multiple switches, at least one flying capacitor, and an intermediate capacitor Cx disposed in the output section. The voltage detection unit 13 detects the voltage at the node that serves as the connection point between the intermediate capacitor Cx and the inductor Lx.

[0132] The control unit 17 provided in each capacitive voltage conversion circuit section 10 controls the switch provided in each capacitive voltage conversion circuit section 10 based on the detection result of the voltage detection unit 13 and the comparison with the threshold, so that the switch switches back and forth between at least two states.

[0133] exist Figure 12 In the case of the voltage converter with the structure shown, instead of detecting the common output voltage Vout, the voltage Vx at the node where the intermediate capacitor Cx and inductor Lx of each voltage converter are connected is detected and fed back (the switch of the capacitive voltage conversion circuit section 10 is switched), thus achieving the same result as... Figure 11The voltage converter shown has the same effect. That is to say, even if there are capacitance deviations and differences in voltage conversion capabilities among the capacitors of each voltage converter in parallel operation, a balance of losses and heat can be achieved at each operating frequency.

[0134] Although Figure 11 as well as Figure 12 The voltage converter shown is an example of one with three capacitive voltage conversion circuit sections 10, but the number of capacitive voltage conversion circuit sections 10 is not limited to this. Furthermore, when an even number of capacitive voltage conversion circuit sections 10 are provided, a unique effect is achieved as long as the structure shown below is used. That is, an even number of capacitive voltage conversion circuit sections 10 are connected in parallel, the input terminal 101 of the input voltage is made common, the output terminal 201 of the output voltage is made common, and the capacitive voltage conversion circuit sections 10 are configured to have at least a first connection state and a second connection state depending on the connection state of the multiple switches. The first resonant frequency determined by the intermediate capacitor, output capacitor, and inductor of the capacitive voltage conversion circuit section 10 in the first connection state and the second resonant frequency determined by the intermediate capacitor, output capacitor, and inductor of the capacitive voltage conversion circuit section 10 in the second connection state are set to be equal. This suppresses the heating and time-dependent degradation caused by the capacitive voltage conversion circuit with the output current biased to one side.

[0135] Fifth Implementation Method

[0136] In the fifth embodiment, the threshold and voltage V are determined according to the following function. x An example of a voltage converter used to control a capacitive voltage conversion circuit is given, where the function takes the node voltage Vx, which is the connection point of the intermediate capacitor Cx and the inductor Lx, and the input voltage Vin as variables.

[0137] Figure 13 This is a block diagram of a voltage converter according to the fifth embodiment. The voltage converter includes: a capacitive voltage conversion circuit 9 that receives an input voltage Vin and converts the input voltage Vin into an output voltage Vout for output; an intermediate capacitor Cx; an output capacitor Cout; an inductor Lx connected in series between the capacitive voltage conversion circuit 9 and the output capacitor Cout; a voltage detection unit 13; and a control unit 17.

[0138] The voltage detection unit 13 includes a reference voltage generation circuit 13A and a comparator circuit 13B. The reference voltage generation circuit 13A outputs a threshold voltage Vth(t) based on the known buck or boost ratio 1 / DIVN of the capacitive voltage conversion circuit unit 9, the ideal output voltage calculated from the input voltage, Vtd as the deviation limit relative to the ideal, and the ramp voltage vs(t) controlled to decrease over time as a threshold. Furthermore, the reference voltage generation circuit 13A outputs a voltage Vxp after applying a given processing to the voltage Vx at node Nx. Alternatively, the voltage Vx at node Nx can be directly output as voltage Vxp.

[0139] The comparator circuit 13B compares the high-low relationship between the threshold voltage Vth and the aforementioned voltage Vxp. The control unit 17 switches the capacitive voltage conversion circuit 9 based on the output of the comparator circuit 13B.

[0140] Figure 14 (A) is a waveform diagram showing the relationship between the voltage Vx at node Nx and the threshold voltage Vth. Figure 14 (B) is a waveform diagram showing the relationship between the output voltage Vout and the threshold voltage Vth in the case where the output voltage Vout is detected and fed back as in conventional voltage converters.

[0141] Here, if 1 / DIVN represents the ratio of the output voltage Vout to the input voltage Vin based on the capacitive voltage conversion circuit section 9, and Vr represents the maximum value of the drop voltage of the output voltage based on the output current, then the threshold voltage Vth can be determined by Vth = Vin / DIVN - Vr. Figure 14 (A) Figure 14 In the example shown in (B), 1 / DIVN = 1 / 3. Furthermore, in Figure 14 (A) Figure 14 In (B), AV(Vout) is the average value of the output voltage Vout.

[0142] Like in Figure 14 As indicated by (B), when the output voltage Vout is detected and fed back as in conventional voltage converters, the ripple of the output voltage increases, and consequently the average voltage of the output voltage Vout decreases.

[0143] In contrast, in this embodiment, such as Figure 14 As shown in (A), by detecting the voltage Vx of node Nx, it is possible to suppress the drop in output voltage Vout while ensuring sufficient noise margin.

[0144] exist Figure 13In the circuit, the reference voltage generation circuit 13A outputs a threshold voltage Vth(t) based on the input voltage Vin, the known buck ratio or boost ratio 1 / DIVN of the capacitive voltage conversion circuit section 9, the deviation limit Vtd, and the ramp voltage vs(t). This threshold voltage Vth(t) can be expressed, for example, by the following mathematical formula 4.

[0145] [Mathematical Expression 4]

[0146] Vth(t) = Vin / DIVN - Vtd + vs(t)

[0147] Therefore, we can obtain the following: Figure 15 The waveform shown. Figure 15 This is a waveform diagram of a voltage converter where the threshold voltage Vth changes in the opposite direction to the change in node voltage Vx over time, starting from the inversion of the comparison result between the node voltage Vx and the threshold voltage Vth.

[0148] The voltage detection unit detects the voltage Vx at the node and determines the threshold voltage Vth, such that... Figure 15 As shown, starting from the inversion of the comparison result between the node voltage Vx and the threshold voltage Vth, the threshold voltage Vth changes in the opposite direction (slope) to the change direction (slope) of the node voltage Vx over time.

[0149] According to this structure, the cross angle between the node voltage Vx and the threshold voltage Vth becomes larger, thus improving the noise tolerance.

[0150] The state where the ramp voltage vs(t) = 0 corresponds to the implementation shown above. The ideal voltage Vout (without load) is Vth = Vin / DIVN. The aforementioned value of 100mV corresponds to Vtd in [Mathematical Equation 4], Vtd = 100mV. Furthermore, in the example above, vs(t) is 0, therefore Vth(t) = Vin / DIVN - 100mV.

[0151] The slope vs(t) is optional. Figure 15 This is an example of vs(t)≠0.

[0152] The above is one example. The voltage detection unit 13 can also generate a detection signal by applying a gain to both the input voltage Vin and the feedback voltage Vx and comparing them. In order to speed up the detection, it can also be configured to apply a slope to the feedback voltage Vx side instead of the threshold voltage Vth.

[0153] Other implementation methods

[0154] In each embodiment, an example of connecting two Dixon-type circuits in parallel and driving them alternately is described, but a single series-parallel charge pump circuit can also be used. Furthermore, in addition to single-phase and two-phase circuits, multiphase capacitive voltage converter circuits can also be constructed.

[0155] In the voltage converters shown in the above embodiments, for the sake of simplicity, an example was described where one inductor and one capacitor constitute the LC circuit 20 were each configured. However, multiple inductors and multiple capacitors may also be used. Furthermore, although an example of a capacitive voltage conversion circuit section 10 including a circuit board with mounted chip components was described, some or all of the capacitors constituting the capacitive voltage conversion circuit section 10 may be integrated into a multilayer substrate.

[0156] Finally, the present invention is not limited to the embodiments described above. Modifications and alterations can be appropriately made by those skilled in the art. The scope of the invention is not shown by the embodiments described above, but by the claims. Furthermore, the scope of the invention includes modifications and alterations from the embodiments within the scope equivalent to the claims.

Claims

1. A voltage converter, comprising: The capacitive voltage conversion circuit receives an input voltage and converts it into an output voltage for output. Output capacitor; An inductor is connected in series between the capacitive voltage conversion circuit and the output capacitor; Voltage detection unit; as well as Control Department The capacitive voltage conversion circuit includes multiple switches, at least one flying capacitor, and an intermediate capacitor disposed in the output section. The voltage detection unit detects the voltage at the node that serves as the connection point between the intermediate capacitor and the inductor. The control unit controls the switch based on a comparison between the voltage of the node and a threshold voltage, causing the switch to switch back and forth between at least two states. The capacitance of the intermediate capacitor is less than the capacitance of the flying capacitor, and the capacitance of the flying capacitor is less than the capacitance of the output capacitor.

2. A voltage converter, comprising: The capacitive voltage conversion circuit receives an input voltage and converts it into an output voltage for output. Output capacitor; An inductor is connected in series between the capacitive voltage conversion circuit and the output capacitor; Voltage detection unit; as well as Control Department The capacitive voltage conversion circuit includes multiple switches, at least one flying capacitor, and an intermediate capacitor disposed in the output section. The voltage detection unit detects the voltage at the node that serves as the connection point between the intermediate capacitor and the inductor. The control unit controls the switch based on a comparison between the voltage of the node and a threshold voltage, causing the switch to switch back and forth between at least two states. The threshold voltage changes in the opposite direction to the voltage change of the node as time passes, starting from the reversal of the comparison result between the detection result of the voltage detection unit and the threshold.

3. The voltage converter according to claim 1 or 2, wherein, The control unit controls the switch at a frequency set according to conditions including the highest and lowest frequencies. The minimum frequency is set to a frequency lower than the resonant frequency determined by the at least one flying capacitor, the intermediate capacitor, the inductor, and the output capacitor.

4. The voltage converter according to claim 3, wherein, The threshold voltage is set to drive at a frequency lower than the resonant frequency under low load.

5. The voltage converter according to claim 1 or 2, wherein, The control unit controls the switch at a frequency set according to conditions including the highest and lowest frequencies. The highest frequency is set to a frequency higher than the resonant frequency determined by the at least one flying capacitor, the intermediate capacitor, the inductor, and the output capacitor.

6. The voltage converter according to claim 1 or 2, wherein, The voltage detection unit detects a voltage related to the difference between the voltage at the node and the input voltage.

7. The voltage converter according to claim 1 or 2, wherein, There are multiple capacitive voltage conversion circuits and multiple inductors. The inputs of the multiple capacitive voltage conversion circuits are connected in parallel, and the outputs of the multiple inductors are connected in parallel.

8. The voltage converter according to claim 7, wherein, There are an even number of capacitive voltage conversion circuit sections, which are connected in parallel. The input terminals of the input voltage are common, and the output terminals of the output voltage are common. Each capacitive voltage conversion circuit section has at least a first connection state and a second connection state depending on the connection state of the plurality of switches. The first resonant frequency determined by the intermediate capacitor, the output capacitor, and the inductor of the capacitive voltage conversion circuit in the first connection state is equal to the second resonant frequency determined by the intermediate capacitor, the output capacitor, and the inductor of the capacitive voltage conversion circuit in the second connection state.

9. A voltage converter, comprising: Multiple capacitive voltage conversion circuits are used to input an input voltage and convert the input voltage into an output voltage for output. Common output capacitor; Multiple inductors are connected in series between the multiple capacitive voltage conversion circuit sections and the output capacitor; and A voltage detection unit and a control unit are provided for each of the capacitive voltage conversion circuits. The capacitive voltage conversion circuit includes multiple switches, at least one flying capacitor, and an intermediate capacitor disposed in the output section. The multiple voltage detection sections respectively detect the voltage at the node that serves as the connection point between the intermediate capacitor and the inductor. The control unit provided in each of the capacitive voltage conversion circuit sections controls the switches provided in each of the capacitive voltage conversion circuit sections based on the detection result of the voltage detection unit and a comparison with a threshold, so that the switches switch back and forth between at least two states. The capacitance of the intermediate capacitor is less than the capacitance of the flying capacitor, and the capacitance of the flying capacitor is less than the capacitance of the output capacitor.

10. The voltage converter according to claim 9, wherein, There are an even number of capacitive voltage conversion circuit sections, which are connected in parallel. The input terminals of the input voltage are common, and the output terminals of the output voltage are common. Each capacitive voltage conversion circuit section has at least a first connection state and a second connection state depending on the connection state of the plurality of switches. The first resonant frequency determined by the intermediate capacitor, the output capacitor, and the inductor of the capacitive voltage conversion circuit in the first connection state is equal to the second resonant frequency determined by the intermediate capacitor, the output capacitor, and the inductor of the capacitive voltage conversion circuit in the second connection state.

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