阅读说明：本技术 串联级联式开关变压器直流直流变换器及其工作方法 (Series cascade type switch transformer direct current converter and working method thereof ) 是由 龙腾 赵晖 申彦峰 于 2020-04-13 设计创作，主要内容包括：本发明公开了一种串联级联式开关变压器直流直流变换器,包括N个电容以及(N-1)个变换器模块,每一个变换器模块包括一个变压器T<Sub>i</Sub>(i＝2、3,……,N),两个单相全桥单元、两个谐振电容C<Sub>i-r1</Sub>,C<Sub>i-r2</Sub>；所述每个第一单相桥式单元包括4个开关管Q<Sub>i-1</Sub>,Q<Sub>i-2</Sub>,Q<Sub>i-3</Sub>,Q<Sub>i-4</Sub>,所述每个第二单相桥式单元包括4个开关管Q<Sub>i-5</Sub>,Q<Sub>i-6</Sub>,Q<Sub>i-7</Sub>,Q<Sub>i-8</Sub>。本发明实现了零电流软开关和死区时间的零电压软开关,零电流软开关和零电压软开关技术可以显著的减小开关损耗以提高效率,输出电压的纹波非常小,实现4700W/in<Sup>3</Sup>的功率密度,48到12V的转换效率超过99.3％,对48到4V的转换效率达到97.6％。(The invention discloses a series cascade type switch transformer direct current converter which comprises N capacitors and (N-1) converter modules, wherein each converter module comprises a transformer T i (i 2, 3, … …, N), two single-phase full-bridge cells, two resonant capacitors C i‑r1 ，C i‑r2 (ii) a Each first single-phase bridge unit comprises 4 switching tubes Q i‑1 ，Q i‑2 ，Q i‑3 ，Q i‑4 Each second single-phase bridge unit comprises 4 switching tubes Q i‑5 ，Q i‑6 ，Q i‑7 ，Q i‑8 . The invention realizes zero current soft switching and zero voltage soft switching with dead time, the zero current soft switching and zero voltage soft switching technology can obviously reduce switching loss to improve efficiency, the ripple of output voltage is very small, and 4700W/in is realized 3 The conversion efficiency of 48 to 12V exceeds 99.3%, and the conversion efficiency of 48 to 4V reaches 97.6%.)

1. A series-cascade type switch transformer DC-DC converter is characterized by comprising N capacitors and (N-1) converter modules, wherein each converter module comprises a transformer T_i(i 2, 3, … …, N), two single-phase full-bridge cells, two resonant capacitors C_i-r1，C_i-r2(ii) a Each first single-phase bridge unit comprises 4 switching tubes Q_i-1，Q_i-2，Q_i-3，Q_i-4Each second single-phase bridge unit comprises 4 switching tubes Q_i-5，Q_i-6，Q_i-7，Q_i-8Switching tube Q_i-1Drain electrode of the switch tube Q_i-2Source electrode of (1), switching tube Q_i-3Drain electrode of the switch tube Q_i-4Source electrode of (1), switching tube Q_i-5Drain electrode of the switch tube Q_i-6Source electrode of (1), switching tube Q_i-7Drain electrode of the switch tube Q_i-8Source electrode of (1), switching tube Q_i-1And Q_i-2Is connected with a transformer T_iOne end of the primary winding and the other end of the primary winding pass through a resonant capacitor C_i-r1Capacitor connected Q_i-3And Q_i-4The common terminal of (1), the switching tube Q_i-5And Q_i-6Is connected with a transformer T_iOne end of the secondary winding and the other end of the secondary winding pass through a resonant capacitor C_i-r2Connection Q_i-7And Q_i-8Common terminal of (C)_NOne end of and a switching tube Q_N-1And Q_N-3Is connected to the source of C_NAnd the other end of the switch tube Q_N-2And Q_N-4Drain connected, similarly, capacitor C_iOne end of and a switching tube Q_i-1And Q_i-3Is connected to the source of the capacitor C_iAnd the other end of the switch tube Q_i-2And Q_i-4Drain electrode connected to capacitor C₁One terminal of (1) and Q_N-5And Q_N-7Is connected to the source of the capacitor C₁Another end of (1) and Q_N-6And Q_N-8Is connected to the drain electrode of C₁，C₂，……,C_i,……,C_NIn series, i.e. C_iIs connected to one end of C_i+1While the other end of (C) is simultaneously_NOne end of which is connected to an input voltage V_in，C₁And one end of and an output V_oDirectly connecting; the series cascade type switch transformer direct current converter is used for completing voltage conversion of N: 1.

2. The series-cascaded switching transformer direct current-direct current converter according to claim 1, wherein the switching tube is a MOSFET, gallium nitride HEMT.

3. The series-cascaded switching transformer direct current-to-direct current converter according to claim 1, characterized in that a resonant capacitor and a transformer are used as energy transmission devices; the switch tube can be switched to zero voltage or zero current through the resonance of the transformer.

4. The series-cascaded switch transformer direct current-direct current converter according to claim 1, wherein the input voltage is a direct current voltage which can be 48V.

5. The operating method of a series-connected cascaded switch transformer DC/DC converter according to claim 1, wherein the switch tubes are controlled by a control circuit to be turned on and off respectively, and the switch tube Q is controlled by a control circuit to be turned on and off respectively_i-1，Q_i-4，Q_i-5，Q_i-8Are in the same switching state, and the switching tube Q_i-2，Q_i-3，Q_i-6，Q_i-7Is in the same switching state as the switching tube Q_i-1，Q_i-4，Q_i-5，Q_i-8The switch states of (2) are opposite.

6. The method for operating the series-connected cascade switch transformer DC/DC converter according to claim 5, characterized by comprising the following steps:

step a), switching tube Q_i-1，Q_i-4，Q_i-5，Q_i-8Open, switch tube Q_i-2，Q_i-3，Q_i-6，Q_i-7Closed, in the process, the capacitor C_iDischarging, current passing through Q_i-3Resonant capacitor C_i-r1Transformer T_iPrimary winding, Q_i-2(ii) a At the same time, the capacitor C₁Charging, current passing through Q_i-6Transformer T_iSecondary winding and resonant capacitor C_i-r2、Q_i-7In which the energy of the resonance process is stored in a transformer T_iAnd a resonant capacitor C_i-r1And C_i-r2In (1).

Step b), switching tube Q_i-1，Q_i-4，Q_i-5，Q_i-8Closed, switch tube Q_i-2，Q_i-3，Q_i-6，Q_i-7And (4) opening. In the process, the capacitor C_iDischarging, current passing through Q_i-1Transformer T_iPrimary winding, resonant capacitor C_i-r1、Q_i-4(ii) a At the same time, the capacitor C₁Charging, current passing through Q_i-8Resonant capacitor C_i-r2Transformer T_iSecondary winding, Q_i-5In which the energy of the resonance process is stored in a transformer T_iAnd a resonant capacitor C_i-r1And C_i-r2In (1).

Step c), repeating the steps a) and b).

Technical Field

The invention belongs to the technical field of power electronics, and relates to a high-power density converter of a power supply system.

Background

The exponential demand of machine learning algorithms for cloud computing has driven the rapid growth of GPUs in data centers. DC-DC converters with 48V down-conversion to 12V or 4V are generally considered to be GPU's in serversNext generation power supplies to reduce complexity and losses. Suppliers of data center servers and equipment, such as Nvidia, Huawei and IBM, require such converters because this is an essential part of their products. Investors and operators of data centers, such as Google Amazon and Microsoft, have teams that focus on studying 48VDC converters to understand the data center's requirements for such technology. A popular research topic and several recent academic papers (within three years) claim power densities of 1500 to 2500W/in³Efficiency is between 97 and 98 for only 48V to 12V conversion.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a series-connection cascade type switch transformer direct-current converter for improving power density and conversion efficiency.

The technical scheme is as follows:

a series cascade type switch transformer DC converter comprises N capacitors and (N-1) converter modules, each of which comprises a transformer T_i(i 2, 3, … …, N), two single-phase full-bridge cells, two resonant capacitors C_i-r1，C_i-r2(ii) a Each first single-phase bridge unit comprises 4 switching tubes Q_i-1，Q_i-2，Q_i-3，Q_i-4Each second single-phase bridge unit comprises 4 switching tubes Q_i-5，Q_i-6，Q_i-7，Q_i-8Switching tube Q_i-1Drain electrode of the switch tube Q_i-2Source electrode of (1), switching tube Q_i-3Drain electrode of the switch tube Q_i-4Source electrode of (1), switching tube Q_i-5Drain electrode of the switch tube Q_i-6Source electrode of (1), switching tube Q_i-7Drain electrode of the switch tube Q_i-8Source electrode of (1), switching tube Q_i-1And Q_i-2Is connected with a transformer T_iOne end of the primary winding and the other end of the primary winding pass through a resonant capacitor C_i-r1Capacitor connected Q_i-3And Q_i-4The common terminal of (1), the switching tube Q_i-5And Q_i-6Is connected with a transformer T_iOne end of the secondary winding and the other end of the secondary winding pass through a resonant capacitor C_i-r2Connection Q_i-7And Q_i-8Common terminal of (C)_NOne end of and a switching tube Q_N-1And Q_N-3Is connected to the source of C_NAnd the other end of the switch tube Q_N-2And Q_N-4Drain connected, similarly, capacitor C_iOne end of and a switching tube Q_i-1And Q_i-3Is connected to the source of the capacitor C_iAnd the other end of the switch tube Q_i-2And Q_i-4Drain electrode connected to capacitor C₁One terminal of (1) and Q_N-5And Q_N-7Is connected to the source of the capacitor C₁Another end of (1) and Q_N-6And Q_N-8Is connected to the drain electrode of C₁，C₂，……,C_i,……,C_NIn series, i.e. C_iIs connected to one end of C_i+1While the other end of (C) is simultaneously_NOne end of which is connected to an input voltage V_in，C₁And one end of and an output V_oDirectly connecting; the series cascade type switch transformer direct current converter is used for completing voltage conversion of N: 1.

Further, the switching tube is a MOSFET or a gallium nitride HEMT.

Further, a resonance capacitor and a transformer are used as an energy transmission device; the switch tube can be switched to zero voltage or zero current through the resonance of the transformer.

Further, the input voltage is a dc voltage, which may be 48V.

The working method of the series cascade type switch transformer DC converter comprises the steps that the switch tubes are controlled by a control circuit to be respectively switched on and off, and the switch tube Q_i-1，Q_i-4，Q_i-5，Q_i-8Are in the same switching state, and the switching tube Q_i-2，Q_i-3，Q_i-6，Q_i-7Is in the same switching state as the switching tube Q_i-1，Q_i-4，Q_i-5，Q_i-8The switch states of (2) are opposite.

The working method of the series cascade type switch transformer direct current converter comprises the following steps:

step a), switching tube Q_i-1，Q_i-4，Q_i-5，Q_i-8Open, switch tube Q_i-2，Q_i-3，Q_i-6，Q_i-7Closed, in the process, the capacitor C_iDischarging, current passing through Q_i-3Resonant capacitor C_i-r1Transformer T_iPrimary winding, Q_i-2(ii) a At the same time, the capacitor C₁Charging, current passing through Q_i-6Transformer T_iSecondary winding and resonant capacitor C_i-r2、Q_i-7In which the energy of the resonance process is stored in a transformer T_iAnd a resonant capacitor C_i-r1And C _{i -r2}In (1).

Step b), switching tube Q_i-1，Q_i-4，Q_i-5，Q_i-8Closed, switch tube Q_i-2，Q_i-3，Q_i-6，Q_i-7And (4) opening. In the process, the capacitor C_iDischarging, current passing through Q_i-1Transformer T_iPrimary winding, resonant capacitor C_i-r1、Q_i-4(ii) a At the same time, the capacitor C₁Charging, current passing through Q_i-8Resonant capacitor C_i-r2Transformer T_iSecondary winding, Q_i-5In which the energy of the resonance process is stored in a transformer T_iAnd a resonant capacitor C_i-r1And C_i-r2In (1).

Step c), repeating the steps a) and b)

Has the advantages that: efficiency and power density are two primary criteria for 48VDC converters. The 48V to 12V or 4V converter needs to be placed as close to the GPU/CPU as possible to reduce losses. Only high power density, i.e., small size, transducers can be in close proximity to the processor chip. Efficiency needs to be very high to reduce loss costs and thermal influence. The invention realizes 4700W/in³Power density and efficiency of over 99.3% for 48 to 12V conversion and 97.6% for 48 to 4V conversion. The invention realizes zero current switching and zero voltage switching with dead time, the ZCS and ZVS technology can obviously reduce the switching loss to improve the efficiency, and the ripple of the output voltage is very small.

Drawings

FIG. 1 is a diagram of a circuit topology;

FIG. 2 is a current flow path of step a);

FIG. 3 is the current flow path of step b);

FIG. 4 is a diagram showing voltage and current waveforms of the switching tubes in the respective modules;

fig. 5 is a graph of output voltage waveforms:

fig. 6(a) is a fluctuation curve of loss with output power, and fig. 6(b) is a fluctuation curve of efficiency with output power.

Detailed Description

The invention is described in further detail below with reference to the figures and the embodiments.

A series-cascaded switch transformer dc-dc converter as shown in fig. 1 comprises N capacitors and (N-1) converter modules, each converter module comprising a transformer T_i(i 2, 3, … …, N), two single-phase full-bridge cells, two resonant capacitors C_i-r1，C_i-r2(ii) a Each first single-phase bridge unit comprises 4 switching tubes Q_i-1，Q_i-2，Q_i-3，Q_i-4Each second single-phase bridge unit comprises 4 switching tubes Q_i-5，Q_i-6，Q_i-7，Q_i-8Switching tube Q_i-1Drain electrode of the switch tube Q_i-2Source electrode of (1), switching tube Q_i-3Drain electrode of the switch tube Q_i-4Source electrode of (1), switching tube Q_i-5Drain electrode of the switch tube Q_i-6Source electrode of (1), switching tube Q_i-7Drain electrode of the switch tube Q_i-8Source electrode of (1), switching tube Q_i-1And Q_i-2Is connected with a transformer T_iOne end of the primary winding and the other end of the primary winding pass through a resonant capacitor C_i-r1Capacitor connected Q_i-3And Q_i-4The common terminal of (1), the switching tube Q_i-5And Q_i-6Is connected with a transformer T_iOne end of the secondary winding and the other end of the secondary winding pass through a resonant capacitor C_i-r2Connection Q_i-7And Q_i-8Common terminal of (C)_NOne end of and a switching tube Q_N-1And Q_N-3Is connected to the source of C_NAnother end of (1) and a switchTube Q_N-2And Q_N-4Drain connected, similarly, capacitor C_iOne end of and a switching tube Q_i-1And Q_i-3Is connected to the source of the capacitor C_iAnd the other end of the switch tube Q_i-2And Q_i-4Drain electrode connected to capacitor C₁One terminal of (1) and Q_N-5And Q_N-7Is connected to the source of the capacitor C₁Another end of (1) and Q_N-6And Q_N-8Is connected to the drain electrode of C₁，C₂，……,C_i,……,C_NIn series, i.e. C_iIs connected to one end of C_i+1While the other end of (C) is simultaneously_NOne end of which is connected to an input voltage V_in，C₁And one end of and an output V_oDirectly connecting; the series cascade type switch transformer direct current converter is used for completing voltage conversion of N: 1. The switch tube can be MOSFET, gallium nitride HEMT. Using a resonant capacitor and a transformer as an energy transmission device; the switch tube can be switched to zero voltage or zero current through the resonance of the transformer. The input voltage is a DC voltage, which may be 48V.

The working method of the series cascade type switch transformer DC converter is that the switch tubes are controlled by the control circuit to be switched on and off respectively, and the switch tube Q_i-1，Q_i-4，Q_i-5，Q_i-8Are in the same switching state, and the switching tube Q_i-2，Q_i-3，Q_i-6，Q_i-7Is in the same switching state as the switching tube Q_i-1，Q_i-4，Q_i-5，Q_i-8The switch states of (2) are opposite.

The method specifically comprises the following steps:

step a), switching tube Q_i-1，Q_i-4，Q_i-5，Q_i-8Open, switch tube Q_i-2，Q_i-3，Q_i-6，Q_i-7Closed, in the process, the capacitor C_iDischarging, current passing through Q_i-3Resonant capacitor C_i-r1Transformer T_iPrimary winding, Q_i-2(ii) a At the same time, the capacitor C₁Charging, current passing through Q_i-6Transformer T_iSecondary winding and resonant capacitor C_i-r2、Q_i-7. In which the energy of the resonance process is stored in a transformer T_iAnd a resonant capacitor C_i-r1And C_i-r2In (1).

Step b), switching tube Q_i-1，Q_i-4，Q_i-5，Q_i-8Closed, switch tube Q_i-2，Q_i-3，Q_i-6，Q_i-7And (4) opening. In the process, the capacitor C_iDischarging, current passing through Q_i-1Transformer T_iPrimary winding, resonant capacitor C_i-r1、Q_i-4(ii) a At the same time, the capacitor C₁Charging, current passing through Q_i-8Resonant capacitor C_i-r2Transformer T_iSecondary winding, Q_i-5. In which the energy of the resonance process is stored in a transformer T_iAnd a resonant capacitor C_i-r1And C_i-r2In (1).

Step c), repeating the steps a) and b).

Fig. 4 is a simulation result of voltage and current waveforms of each switching tube, where the simulation result shows that the voltage and current of all the switching tubes are equal, which indicates that, from the power perspective, all the modules are connected in parallel, and the transmitted power is the same, the current equalizing effect is good, and the transmission efficiency can reach the highest; the voltage stress of all modules is the same and is only the input voltage V_inThe voltage of the modules is one-fourth of the voltage-sharing module, so that the voltage-sharing effect is good, and the voltage stress of the modules can be greatly reduced; at the moment of switching all the modules, the current is almost zero, which shows that the system can realize zero-voltage switching-on and zero-current switching-off on the basis of the application dead zone, and the switching loss is extremely low.

Fig. 5 is a waveform diagram of the output voltage, and the result shows that the output ripple is very small and the voltage is very stable. Fig. 6(a) is a graph showing the fluctuation of loss with output power, in which the solid line and the broken line are graphs of the loss of two different MOSFETs, respectively, and the conduction loss of internal resistance of 0.9m Ω and 0.6m Ω, respectively. The results show that the maximum loss of the system is less than 7 watts at all powers, and therefore the system has very low heat generation and high reliability. Fig. 6(b) is a graph showing the fluctuation of efficiency with output power, in which the solid line and the broken line are graphs of losses of two different MOSFETs, respectively, having internal resistances of 0.9m Ω and 0.6m Ω conduction losses. The result shows that the peak power of the system is more than 99.5%, the full load efficiency is more than 99%, the efficiency of the system is far beyond the efficiency of the existing industrial products and experimental prototypes in academic circles, and the system has great application value.