Method for improving transient response speed of two-stage voltage regulator module by using parallel single-stage bypass chopper

Abstract

The invention relates to a method for improving the transient response speed of a two-stage voltage regulator module by using a parallel single-stage bypass chopper, and a system comprises a two-stage main converter and a parallel single-stage bypass chopper auxiliary circuit, wherein the two-stage main converter is composed of a DCX, a multi-phase staggered Buck, an input capacitor, an intermediate bus capacitor and an output capacitor; wherein the auxiliary circuit comprises a first switching device Sa1, a second switching device Sa2 and an inductor La; by applying the technical scheme, the optimization effect can be further improved on the basis of not changing the hardware structure and the control method of the main converter.

Description

Technical Field

[0001] The present invention relates to the technical field, and in particular to a method for improving the transient response speed of a two-stage voltage regulator module by using a parallel single-stage bypass chopper. Background Art

[0002] The explosive growth of data and computing brought about by artificial intelligence, 5G technology and cloud computing has promoted the rapid development of data center power supplies. As the direct power supply unit of the data center power supply, the 48V:1V two-stage voltage regulator (VRM) provides power conversion with a large step-down ratio and large output current for power-consuming devices such as GPUs, CPUs and ASICs. While the demand for power capacity and power density is gradually increasing, rapid and reliable transient response is also the main challenge it currently faces.

[0003] Figure 1 The figure shows a schematic diagram of a two-stage VRM architecture. The first stage can be implemented as an LLC-DCX fixed gain converter, and the second stage can be implemented as a multi-phase interleaved Buck. In order to achieve a smooth voltage output and reduce the output voltage ripple, the output inductance of the multi-phase interleaved Buck converter should be increased; on the contrary, in order to achieve a rapid transient response, so that the output voltage can avoid large undershoot and overshoot when the load suddenly increases or decreases and quickly recover to a steady state, the output inductance of the multi-phase interleaved Buck converter should be reduced. Therefore, there is a contradiction between the optimization of steady-state performance and the optimization of transient performance in the design of VRM.

[0004] The main converter is designed with steady state as the priority goal, and the auxiliary circuit is connected to the output of the Buck converter. When the output voltage undershoots and overshoots occur, current is injected and extracted respectively, which can reduce the overshoot amplitude, so that the VRM can show good performance in both steady state and transient state. The currently published implementation methods are as follows Figure 2 shown. Figure 2 (a) Build an active electronic capacitor connected at the output, Figure 2 (b) uses an auxiliary Buck in parallel with the second-stage DC / DC converter.

[0005] The problems with the above implementation method are: (1) The auxiliary Buck is connected in parallel with the second-stage DC / DC main circuit Buck, and its ability to optimize the transient response of the main circuit Buck is limited; (2) The number of electronic capacitor auxiliary circuit components is large and the control is complex. Summary of the invention

[0006] In view of this, the object of the present invention is to provide a method for improving the transient response speed of a two-stage voltage regulator module by using a parallel single-stage bypass chopper, which can further improve the optimization effect without changing the hardware structure and control method of the main converter.

[0007] To achieve the above object, the present invention adopts the following technical solution: a method for improving the transient response speed of a two-stage voltage regulator module by using a parallel single-stage bypass chopper, the system comprises a two-stage main converter composed of a DCX, a multi-phase interleaved Buck, an input capacitor, an intermediate bus capacitor and an output capacitor, and a parallel single-stage bypass chopper auxiliary circuit, wherein the auxiliary circuit comprises a first switch device S a1 , the second switching device S a2 and an inductor L a ; The state determination method is carried out by using multi-threshold comparison weighting. The comparison variables include the instantaneous value of the output voltage. u o and the differential value d u o / d t , output current i o The differential value d i o / d t and the output capacitor current i c The differential value d i c / d t , the load surge comparison thresholds of the corresponding variables are u th1 , u th1 '、 i oth1 'and i cth1 ', the load reduction comparison thresholds are u th2 , u th2 '、 i oth2 'and i cth2 ', the corresponding weights are p 1~ p 4. The judgment variable is p The load sudden increase and load sudden decrease comparison thresholds of the judgment variable are p th1 and p th1 .

[0008] In a preferred embodiment, when the load is stable, that is, the output current variation amplitude is much smaller than the variation amplitude allowed by the system power capacity, or the output voltage undershoot and overshoot amplitude caused by the variation speed is much smaller than the output voltage amplitude, only the main converter completes the power conversion, and the first switching device S a1 , the second switching device Sa2 In the off state, the inductor L a No current.

[0009] In a preferred embodiment, when a sudden load increase of the system is detected, the first switch device S a1 First, the first switching device S a1 The drive signal controls the conduction of the inductor L a The current rises rapidly, and the auxiliary circuit injects current into the load side; this lasts for a period of time until t2, and the first switch device S a1 Turn off, the second switch device S a2 Conductivity, Inductor L a The current starts to decrease, and the auxiliary circuit continues to inject current into the load side; at t3, the inductor L a The current decreases to 0, and the second switching device S a2 Turn off; inductor L a The current changes from 0 to 0, which is called an operation cycle of the auxiliary circuit. In a load surge event, the first switching device S a1 , the second switching device S a2 The drive signal pulse appears only once, or multiple times periodically or nonlinearly with respect to time to flexibly control the inductor L a Inductor current slope.

[0010] In a preferred embodiment, when a sudden load drop of the system is detected, the second switch device S a2 First, the second switching device S a2 The drive signal controls the conduction of the inductor L a The current rises in the reverse direction, and the auxiliary circuit draws current from the load side; this lasts for a period of time until t5, and the second switching device S a2 Turn off, the first switch device S a1 Conductivity, Inductor L a The current starts to decrease, and the auxiliary circuit continues to draw current from the load side; at t6, the inductor L a The current decreases to 0, and the first switching device S a1 In a load dump event, the first switch device S a1 , the second switching device S a2 The drive signal pulse appears only once, or multiple times periodically or nonlinearly with respect to time to flexibly control the inductor L aInductor current slope.

[0011] Compared with the prior art, the present invention has the following beneficial effects: (1) Compatible with various control strategies of the main converter The method can further improve the optimization effect without changing the hardware structure and control method of the main converter. The control loop of the main converter and the control loop of the auxiliary circuit can be decoupled from each other. Any main converter control optimization strategy for transient response speed can be implemented on the main converter of this solution, and the auxiliary circuit can further improve the transient response speed on this basis. Since the auxiliary circuit does not operate when the load is stable, it has almost no effect on the system conversion efficiency.

[0012] (2) Using the high voltage difference of the two-stage structure to achieve a rapid increase in injection current Compared with electronic capacitors or parallel Buck auxiliary circuits connected in parallel on the second-stage DC / DC converter, when dealing with output voltage undershoot caused by a sudden load increase, this solution uses a higher voltage difference before and after the two-stage main converter to achieve a faster compensation current, which can more significantly reduce the output voltage undershoot amplitude and show better performance in the high-power VRM field.

[0013] (3) Various detection methods and flexible control methods The state judgment method using multi-threshold comparison weighting can be implemented by digital processor sampling or by analog circuit; the number of comparison variables can be increased or decreased to minimize logical operations while ensuring reliable state judgment. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the architecture of a two-stage VRM in the prior art; Figure 2 Two transient optimization implementation methods in the prior art, wherein (a) is a schematic diagram of building an active electronic capacitor connected to the output end, and (b) is a schematic diagram of using an auxiliary Buck in parallel with the second-stage DC / DC converter; Figure 3 A schematic diagram of the system configuration of a preferred embodiment of the present invention; Figure 4 A schematic diagram of main control and circuit waveforms of a preferred embodiment of the present invention; Figure 5 The circuit time-sharing equivalent schematic diagram of the preferred embodiment of the present invention, wherein (a) is Figure 4 The equivalent schematic diagram in the time periods t0-t1, t3-t4, and t7-t8 of Figure 4 The equivalent schematic diagram in the time period t1-t2 of (c) is Figure 4 The equivalent schematic diagram during the time period t2-t3; Figure 6 A state determination flow chart of a preferred embodiment of the present invention; Figure 7 The simulation results of the scheme without auxiliary circuit and the present scheme of the preferred embodiment of the present invention are shown in FIG. 1 , wherein (a) is the simulation result of the scheme without auxiliary circuit, and (b) is the simulation result of the present invention. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0016] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0017] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application; as used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations.

[0018] refer to Figure 3-7 The system structure of a method for improving the transient response speed of a two-stage voltage regulator module by using a parallel single-stage bypass chopper proposed in the present invention comprises a two-stage main converter composed of a DCX, a multi-phase interleaved Buck, an input capacitor, an intermediate bus capacitor and an output capacitor, and a parallel single-stage bypass chopper auxiliary circuit, wherein the auxiliary circuit comprises a first switch device S a1 , the second switching device S a2 and an inductor L a One implementation principle of this method is as follows: (1) A feasible multi-threshold comparison weighting method can be used to determine the state. The comparison variables include the instantaneous value of the output voltage. u o and the differential value d u o / d t , output current i o The differential value d i o / d t and the output capacitor current i c The differential value d i c / d t, the load surge comparison thresholds of the corresponding variables are u th1 , u th1 '、 i oth1 'and i cth1 ', the load reduction comparison thresholds are u th2 , u th2 '、 i oth2 'and i cth2 ', the corresponding weights are p 1~ p 4. The judgment variable is p The load sudden increase and load sudden decrease comparison thresholds of the judgment variable are p th1 and p th1 .according to Figure 5 The load state is determined as shown in the flow chart, and the values ​​of the above thresholds and weights are determined according to the circuit hardware parameters and power capacity.

[0019] (2) When the load is stable, that is, the output current change amplitude is much smaller than the change amplitude allowed by the system power capacity, or the output voltage undershoot and overshoot amplitude caused by the change speed is much smaller than the output voltage amplitude, the power conversion is completed only by the main converter, and the first switching device S a1 , the second switching device S a2 In the off state, the inductor L a There is no current in the Figure 4 In the time periods t0-t1, t3-t4, t7-t8, corresponding Figure 5 (a) Equivalent schematic diagram.

[0020] (3) When a sudden load increase is detected in the system, Figure 4 At time t1, the first switching device S a1 First, the first switching device S a1 The drive signal controls the conduction of the inductor L a The current rises rapidly, and the auxiliary circuit injects current into the load side; this lasts for a period of time until t2, and the first switch device S a1 Turn off, the second switch device S a2 Conductivity, Inductor L a The current starts to decrease, and the auxiliary circuit continues to inject current into the load side; at t3, the inductor L aThe current decreases to 0, and the second switching device S a2 Turn off; inductor L a The current changes from 0 to 0, which is called an operation cycle of the auxiliary circuit; the time period t1-t2 corresponds to Figure 5 (b), corresponding to the time period t2-t3 Figure 5 (c). In a load surge event, the first switching device S a1 and the second switching device S a2 The drive signal pulse can appear only once, or multiple times periodically or nonlinearly with respect to time to flexibly control the inductor. L a Inductor current slope.

[0021] (4) When a sudden load reduction is detected in the system, Figure 4 At time t4, the second switching device S a2 First, the second switching device S a2 The drive signal controls the conduction of the inductor L a The current rises in the reverse direction, and the auxiliary circuit draws current from the load side; this lasts for a period of time until t5, and the second switching device S a2 Turn off, the first switch device S a1 Conductivity, Inductor L a The current starts to decrease, and the auxiliary circuit continues to draw current from the load side; at t6, the inductor L a The current decreases to 0, and the first switching device S a1 The time period t4-t5 corresponds to Figure 5 (c), corresponding to the time period t5-t6 Figure 5 (b). In a load dump event, the first switching device S a1 and the second switching device S a2 The drive signal pulse can appear only once, or multiple times periodically or nonlinearly with respect to time to flexibly control the inductor. L a Inductor current slope.

[0022] In summary, the method of using a parallel single-stage bypass chopper to improve the transient response speed of a two-stage voltage regulator module described in the present invention controls the first switch device S through circuit sampling detection and multi-threshold comparison weighted logic judgment. a1 and the second switching device S a2 The turning on and off of the auxiliary circuit enables the auxiliary circuit to inject or extract current to the load side, thereby improving the transient response speed of the traditional two-stage VRM.

[0023] Taking a load sudden increase event as an example, the specific implementation process of the solution of the present invention is introduced in combination with a simulation waveform diagram. Figure 7 (a) is the simulation result without auxiliary circuit. Figure 7 (b) is the simulation result of this solution. The circuit is in steady-state operation before 2.05ms, with an output current of 500A. At 2.05ms, the load suddenly doubles, and the target steady-state current should be 1000A.

[0024] exist Figure 7 In (a), when a load surge event occurs, the output voltage drops sharply to about 0.5V, recovers to 0.8V after about 20us, and returns to normal after about 70us, and the system returns to steady state.

[0025] exist Figure 7 In (b), when a load surge event occurs, the first switching device S a1 and the second switching device S a2 Alternating conduction, inductor L a A rapidly rising current appears on the output terminal and slowly decreases to 0 in a sawtooth shape. The current is injected into the output terminal, and the output voltage returns to normal after about 70us within the range of a valley value not less than 0.8V, and the system returns to a steady state.

[0026] Comparing the two solutions, the solution proposed in the present invention can significantly reduce the output voltage undershoot behavior when the load changes suddenly, and effectively avoid the undervoltage state below 0.8V for 20us.

Claims

1. A method for improving the transient response speed of a two-stage voltage regulator module using a parallel single-stage bypass chopper, characterized in that: The system consists of a two-stage main converter consisting of DCX, multi-phase interleaved Buck, input capacitor, intermediate bus capacitor and output capacitor, and a parallel single-stage bypass chopper auxiliary circuit, wherein the auxiliary circuit includes a first switching device S a1 , the second switching device S a2 and an inductor L a ; The state determination method is carried out by using multi-threshold comparison weighting. The comparison variables include the instantaneous value of the output voltage. u o and the differential value d u o / d t , output current i o The differential value d i o / d t and the output capacitor current i c The differential value d i c / d t , the load surge comparison thresholds of the corresponding variables are u th1 , u th1 '、 i oth1 'and i cth1 ', the load reduction comparison thresholds are u th2 , u th2 '、 i oth2 'and i cth2 ', the corresponding weights are p 1~ p 4. The judgment variable is p The load sudden increase and load sudden decrease comparison thresholds of the judgment variable are p th1 and p th1 .

2. The method for improving the transient response speed of a two-stage voltage regulator module by using a parallel single-stage bypass chopper according to claim 1, characterized in that: When the load is stable, that is, the output current change amplitude is much smaller than the change amplitude allowed by the system power capacity, or the output voltage undershoot and overshoot amplitude caused by the change speed is much smaller than the output voltage amplitude, only the main converter completes the power conversion, and the first switching device S a1 , the second switching device S a2 In the off state, the inductor L a No current.

3. The method for improving the transient response speed of a two-stage voltage regulator module by using a parallel single-stage bypass chopper according to claim 1, characterized in that: When a sudden load increase is detected in the system, the first switch device S a1 First, the first switching device S a1 The drive signal controls the conduction of the inductor L a The current rises rapidly, and the auxiliary circuit injects current into the load side; this lasts for a period of time until t2, and the first switch device S a1 Turn off, the second switch device S a2 Conductivity, Inductor L a The current starts to decrease, and the auxiliary circuit continues to inject current into the load side; at t3, the inductor L a The current decreases to 0, and the second switch device S a2 Shut down; Inductors L a The current changes from 0 to 0, which is called an operation cycle of the auxiliary circuit. In a load surge event, the first switching device S a1 , the second switching device S a2 The drive signal pulse appears only once, or appears multiple times periodically or nonlinearly with respect to time to flexibly control the inductor L a Inductor current slope.

4. The method for improving the transient response speed of a two-stage voltage regulator module by using a parallel single-stage bypass chopper according to claim 1, characterized in that: When a sudden load drop is detected in the system, the second switch device S a2 First, the second switching device S a2 The drive signal controls the conduction of the inductor L a The current rises in the reverse direction, and the auxiliary circuit draws current from the load side; this lasts for a period of time until t5, and the second switching device S a2 Turn off, the first switch device S a1 Conductivity, Inductor L a The current starts to decrease, and the auxiliary circuit continues to draw current from the load side; at t6, the inductor L a The current decreases to 0, and the first switching device S a1 In a load dump event, the first switch device S a1 , the second switching device S a2 The drive signal pulse appears only once, or appears multiple times periodically or nonlinearly with respect to time to flexibly control the inductor L a Inductor current slope.

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