Switched capacitor converter based on auxiliary circuit

Abstract

The invention relates to a switched capacitor converter, and belongs to the technical field of power supply. The invention aims to solve the problems that the no-load voltage transformation ratio of a switched capacitor circuit is fixed, the output voltage of a converter cannot be stable when a current-stage bus or a load fluctuates, a data center load point has the characteristics of large load fluctuation and fast current change, and the response capability of the switched capacitor converter is difficult to achieve. The invention further provides a switched capacitor converter based on the auxiliary circuit.

Description

Technical Field

[0001] The invention relates to a switched capacitor converter, belonging to the technical field of power supply. Background Art

[0002] In the data center power supply system, a two-stage structure consisting of a 48V-12V bus converter and a 12V-1V load point converter is widely used to complete power conversion. However, the two-stage structure system is large in size, and there will be high transmission losses on the 12V power bus when the load point current is large. Therefore, with the continuous increase in power consumption in data centers, the single-stage structure has more advantages than the two-stage structure. The use of a switched capacitor circuit can achieve single-stage power conversion. The switched capacitor circuit does not require a transformer, but uses capacitor elements for energy conversion. Thanks to the significantly higher energy density of capacitive elements than magnetic elements, the switched capacitor converter can achieve higher power density, and the switched capacitor circuit can achieve a higher voltage ratio while keeping the voltage stress of passive components and power switches small, thereby achieving high-efficiency power conversion. These characteristics make the switched capacitor circuit suitable for use in the low-voltage and high-current scenario of the data center power supply system. However, when the switched capacitor topology is applied to the data center power supply system, there are still the following problems:

[0003] (1) The no-load voltage ratio of the switched capacitor circuit is fixed. When the upstream bus or load fluctuates, the converter output voltage cannot be stabilized.

[0004] (2) The load points in data centers have the characteristics of large load fluctuations and rapid current changes, and the response capability of the switched capacitor converter is difficult to achieve. Summary of the invention

[0005] The present invention aims to solve the problem that the no-load voltage transformation ratio of the switched capacitor circuit is fixed, and when the upstream bus or load fluctuates, the output voltage of the converter cannot be stabilized, and the load points in the data center have the characteristics of large load fluctuations and rapid current changes, and the response capability of the switched capacitor converter is difficult to achieve. A switched capacitor converter based on an auxiliary circuit is proposed.

[0006] The technical solution adopted by the present invention to solve the above problems is: the present invention includes a switch tube M1, a switch tube M2, a switch tube M3, a switch tube M4, a switch tube M5, a switch tube M6, a switch tube M7, a switch tube M9, an inductor L1, an inductor L2, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C6 and a high-frequency auxiliary voltage regulation circuit;

[0007] The switch tube M1, the switch tube M2, the switch tube M3, the switch tube M4, the switch tube M5, the switch tube M6, the switch tube M7, the switch tube M9, the inductor L1, the inductor L2, the capacitor C1, the capacitor C2, the capacitor C3, the capacitor C4, the capacitor C5 and the capacitor C6 form a main switch capacitor topology circuit, wherein the switch tube M1, the switch tube M2, the switch tube M3, the switch tube M4, the switch tube M5, the switch tube M6 and the inductor L2 are connected in series in sequence, the switch tube M7 is connected in series with the inductor L2, the switch tube M9 is connected in series with the inductor L1, the capacitor C1 is located between the switch tube M1 and the switch tube M2, the capacitor C2 is located between the switch tube M2 and the switch tube M3, the capacitor C3 is located between the switch tube M3 and the switch tube M4, the capacitor C4 is located between the switch tube M4 and the switch tube M5, and the capacitor C5 is located between the switch tube M5 and the switch tube M6;

[0008] The high frequency auxiliary voltage regulation circuit is connected with the main switch capacitor topology.

[0009] Furthermore, the high-frequency auxiliary voltage regulation circuit includes a switch tube M 11 , switch tube M 12 , switch tube M 13 , capacitor C7 and inductor L3;

[0010] Switching tube M 13 , switch tube M 11 , inductor L3 and switch tube M 12 The capacitor C7 is connected in series with the switch tube M 11 With switch tube M 13 Between the switch tube M 13 Switches synchronously with switch tube M7.

[0011] Furthermore, the switch tube M7 and the switch tube M9 are synchronous rectifier tubes.

[0012] The beneficial effects of the present invention are as follows: the converter designed by the present invention can realize 48V / 1V step-down conversion, and the rated output power is 35W, that is, in steady state, the converter input voltage is 48V, the output voltage is 1V, and the auxiliary voltage regulation circuit outputs an average power of 0 in steady state, so the average output current of the auxiliary circuit is 0A; the present invention increases the step-down ratio of the 6:1 switch capacitor topology to 48:1 while using two fewer switch tubes, further improving the power density of the converter. By changing the control timing of the switch tube, the new topology incorporates the device reuse Buck circuit, and the Buck circuit transformation ratio is 8:1, working near its optimal transformation ratio; in order to improve the dynamic response speed of the converter and ensure that the output voltage can remain stable when the input or load fluctuates, the present invention adds a high-frequency auxiliary voltage regulation circuit to the new switch capacitor topology. The high-frequency auxiliary voltage regulation circuit provides power to the load in transient state, and its output average power is 0 in steady state. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a circuit diagram of a 6:1 switched capacitor topology;

[0014] Figure 2 This is the schematic diagram of the redesigned switched capacitor topology circuit;

[0015] Figure 3 It is a circuit diagram of a 48:1 switched capacitor converter based on an auxiliary circuit;

[0016] Figure 4 It is a schematic diagram of the simulation results of the high-frequency voltage regulation circuit;

[0017] Figure 5 is a schematic diagram of transient simulation results;

[0018] Figure 6 It is the control block diagram of the high frequency auxiliary voltage regulation circuit;

[0019] Figure 7 It is the main circuit control block diagram. DETAILED DESCRIPTION

[0020] Specific implementation method 1: Figure 3 As shown, a switched capacitor converter based on an auxiliary circuit includes a switch tube M1, a switch tube M2, a switch tube M3, a switch tube M4, a switch tube M5, a switch tube M6, a switch tube M7, a switch tube M9, an inductor L1, an inductor L2, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C6 and a high-frequency auxiliary voltage regulation circuit;

[0021] The switch tube M1, the switch tube M2, the switch tube M3, the switch tube M4, the switch tube M5, the switch tube M6, the switch tube M7, the switch tube M9, the inductor L1, the inductor L2, the capacitor C1, the capacitor C2, the capacitor C3, the capacitor C4, the capacitor C5 and the capacitor C6 form a main switch capacitor topology circuit, wherein the switch tube M1, the switch tube M2, the switch tube M3, the switch tube M4, the switch tube M5, the switch tube M6 and the inductor L2 are connected in series in sequence, the switch tube M7 is connected in series with the inductor L2, the switch tube M9 is connected in series with the inductor L1, the capacitor C1 is located between the switch tube M1 and the switch tube M2, the capacitor C2 is located between the switch tube M2 and the switch tube M3, the capacitor C3 is located between the switch tube M3 and the switch tube M4, the capacitor C4 is located between the switch tube M4 and the switch tube M5, and the capacitor C5 is located between the switch tube M5 and the switch tube M6;

[0022] The high frequency auxiliary voltage regulation circuit is connected with the main switch capacitor topology.

[0023] The high-frequency auxiliary voltage regulation circuit includes a switch tube M 11 , switch tube M 12 , switch tube M 13, capacitor C7 and inductor L3;

[0024] Switching tube M 13 , switch tube M 11 , inductor L3 and switch tube M 12 The capacitor C7 is connected in series with the switch tube M 11 With switch tube M 13 Between the switch tube M 13 Switches synchronously with switch tube M7.

[0025] Among them, the switch tube M7 and the switch tube M9 are synchronous rectifier tubes.

[0026] like Figure 3 As shown, for the main circuit part, the present invention can determine the parameters of each passive component in the main circuit according to the voltage gain of 48:1, and determine that the operating frequencies of the switch tubes M1-M7 and the switch tube M9 are all 166kHz under the rated working state. The specific design values ​​of the main circuit component parameters are shown in Table 1.

[0027] Table 1 Main circuit device parameters

[0028]

[0029]

[0030] For high frequency auxiliary voltage regulation circuit, such as Figure 3 As shown, the present invention sets the switch on time of the high-frequency auxiliary voltage regulation circuit to 60ns. According to the control block diagram and input and output indicators, the relevant design parameters of the high-frequency auxiliary voltage regulation circuit are shown in Table 2.

[0031] Table 2 High frequency auxiliary voltage regulation circuit device parameters

[0032] element parameter <![CDATA[Capacitor C7]]> 9μF <![CDATA[Inductor L3]]> 120nH

[0033] Since the auxiliary voltage regulation circuit has a high operating frequency and in order to achieve the ability to track load changes faster, the present invention adopts constant on-time control for the auxiliary voltage regulation circuit, and relies on the current ripple value of the output capacitor to control the shutdown of the auxiliary voltage regulation circuit, using voltage and current dual-loop control. The schematic diagram of the closed-loop control unit of this part of the circuit is shown in Figure 6 As shown. The sampled output voltage signal and output current signal are passed through the PI control link and the output switch tube M is calculated. 11 and M 12 The control signal of the auxiliary voltage regulation circuit can thus realize the voltage regulation function.

[0034] The present invention adopts current control for the switch capacitor main circuit. When the average power transmitted by the auxiliary circuit is not 0 in a plurality of consecutive cycles, the main circuit participates in the regulation. The schematic diagram of the closed-loop control unit of this part of the circuit is shown in FIG. Figure 7 The average current signal is sampled, compared with the triangular carrier signal through the PI control link, and then the corresponding PWM signal is output to control the switch tubes M1-M7, M9, M 13 The on and off.

[0035] How it works

[0036] like Figure 1 The figure shows a 6:1 switched capacitor topology, which has two operating modes. The duty cycle of the switch tube in each mode is 50%. To achieve a 48:1 transformation ratio, the common output point of the two modes is extracted and used as the input point of the Buck circuit;

[0037] like Figure 2 As shown, considering that the four switches in the topology are operated in the Buck circuit switching mode, the switch tubes M8 and M 10 It is changed to an inductor. At the same time, since the C5 branch is independent during operation, in order to ensure the symmetry of the inductor current, the inductor at the switch tube M8 is placed before the output port and after the C5 branch, and the reconstructed switch capacitor topology is obtained;

[0038] In the topology, the switch tubes M7 and M9 are used as synchronous rectifier tubes, working in Buck mode, with a Buck transformation ratio of 8:1, working near its optimal transformation ratio. The step-down ratio of the main topology is 48:1, and the main topology completes steady-state power conversion. In order to ensure the stability of the output when the input and load fluctuate, a high-frequency auxiliary voltage regulation circuit is added to the main topology. The auxiliary circuit participates in power conversion in transient state, and the average power of the auxiliary circuit is 0 in steady state. The auxiliary voltage regulation circuit selects the Buck circuit, and any flying capacitor in the main topology can be used as the input of the auxiliary voltage regulation circuit. Considering the voltage stress and efficiency issues, the last-stage flying capacitor C5 is used as the input source of the auxiliary voltage regulation circuit to charge the capacitor C7 of the auxiliary circuit.

[0039] Since the negative electrode of capacitor C5 is floating when working, in order to ensure that C7 is charged, it is necessary to add a switch tube M. 13 , which switches synchronously with the switch tube M7 to ensure that the reference potential is equal when C5 charges C7. 13 During the conduction period, part of the power can be directly transmitted through the auxiliary circuit. The final topology is as follows Figure 3 shown.

[0040] For the auxiliary voltage regulation circuit, its operating frequency is higher than that of the main topology, reaching the MHz level, and in order to achieve the ability to track load changes faster, constant on-time control is preferably used. Because the ripple voltage in the feedback loop is not enough to ensure that it is in phase with the inductor current when the output capacitor is a low-ESR ceramic capacitor, stable control cannot be achieved, so the current ripple value of the output capacitor is relied on to control the shutdown of the auxiliary voltage regulation circuit. Finally, the auxiliary voltage regulation circuit adopts voltage and current dual-loop control. The outer loop is the voltage loop, which is taken from the output voltage; the inner loop is the current loop, which is taken from the inflow current of the output capacitor.

[0041] Since the auxiliary circuit has a low input capacitor output power, it can only track the sudden change of the load in a transient state to ensure voltage stability within a certain period of time, and the main circuit still needs to have steady-state regulation capabilities. When the average power transmitted by the auxiliary circuit is not 0 in multiple consecutive cycles, the main circuit needs to participate in the regulation. The main circuit uses average current control, and changes the duty cycle of the main topology switch tube by sampling and judging the average output current of the auxiliary circuit.

[0042] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A switched capacitor converter based on an auxiliary circuit, characterized in that: It includes a switch tube M1, a switch tube M2, a switch tube M3, a switch tube M4, a switch tube M5, a switch tube M6, a switch tube M7, a switch tube M9, an inductor L1, an inductor L2, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C6 and a high-frequency auxiliary voltage regulation circuit; The switch tube M1, the switch tube M2, the switch tube M3, the switch tube M4, the switch tube M5, the switch tube M6, the switch tube M7, the switch tube M9, the inductor L1, the inductor L2, the capacitor C1, the capacitor C2, the capacitor C3, the capacitor C4, the capacitor C5 and the capacitor C6 form a main switch capacitor topology circuit, wherein the switch tube M1, the switch tube M2, the switch tube M3, the switch tube M4, the switch tube M5, the switch tube M6 and the inductor L2 are connected in series in sequence, the switch tube M7 is connected in series with the inductor L2, the switch tube M9 is connected in series with the inductor L1, the capacitor C1 is located between the switch tube M1 and the switch tube M2, the capacitor C2 is located between the switch tube M2 and the switch tube M3, the capacitor C3 is located between the switch tube M3 and the switch tube M4, the capacitor C4 is located between the switch tube M4 and the switch tube M5, and the capacitor C5 is located between the switch tube M5 and the switch tube M6; The high frequency auxiliary voltage regulation circuit is connected with the main switch capacitor topology.

2. A switched capacitor converter based on an auxiliary circuit according to claim 1, characterized in that: The high-frequency auxiliary voltage regulation circuit includes a switch tube M 11 , switch tube M 12 , switch tube M 13 , capacitor C7 and inductor L3; Switching tube M 13 , switch tube M 11 , inductor L3 and switch tube M 12 The capacitor C7 is connected in series with the switch tube M 11 With switch tube M 13 Between the switch tube M 13 Switches synchronously with switch tube M7.

3. The switch capacitor converter based on the auxiliary circuit according to claim 1, characterized in that: The switch tube M7 and the switch tube M9 are synchronous rectifier tubes.

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