CN117526712A

CN117526712A - DC-DC converter and DC-DC converter

Info

Publication number: CN117526712A
Application number: CN202210928121.7A
Authority: CN
Inventors: 冷阳; 张晋颖; 刘静丽; 刘雁开
Original assignee: Great Wall Power Technology Co ltd
Current assignee: Great Wall Power Technology Co ltd
Priority date: 2022-08-03
Filing date: 2022-08-03
Publication date: 2024-02-06

Abstract

The invention provides a DC-DC converter and a DC-DC conversion device, which relate to the field of power sources and comprise a first switching unit, a second switching unit and a third switching unit, wherein the first switching unit comprises a first switching tube and a fourth switching tube which are sequentially connected in series between an input voltage positive end and a first node; the second switching unit comprises a sixth switching tube, a seventh switching tube, a fifth switching tube and an eighth switching tube which are sequentially connected in series between the output inductor and the negative end of the input voltage; the primary winding of the transformer is connected between the common node of the first switching tube and the fourth switching tube and the common node of the second switching tube and the third switching tube; the secondary winding of the transformer is connected between the common node of the sixth switching tube and the seventh switching tube and the common node of the fifth switching tube and the eighth switching tube; and the second end of the output inductor is connected with the first end of the output capacitor, wherein the first node and the second node are connected with the second switch unit, so that the efficiency of the power converter is greatly improved, and the volume and the cost of the power converter are reduced.

Description

DC-DC converter and DC-DC converter

Technical Field

The invention relates to the field of power supplies, in particular to a DC-DC converter and a DC-DC conversion device.

Background

Services supported by data centers are now necessary for society and there are more and more services supported by them. Therefore, with the development of technology, the energy consumption of the data center will increase.

In order to meet the high-efficiency requirement of the system, the on-board power supply mode of the server starts to change from a 12V bus to a 40V-60V bus, namely, the voltage of the 40V-60V bus is changed to 12V on the server board. There are two schemes for the current 40V-60V to 12V conversion.

The first solution is to use an isolated converter, such as a full bridge converter. It uses a transformer to step down and provide physical isolation to meet safety requirements. In this topology, because of the physical isolation of the primary and secondary sides of the transformer, both the primary and secondary sides have respective references to ground. In order to realize the conversion from the high voltage at the primary side to the low voltage at the secondary side, the number of windings at the primary side is relatively large, and the primary side current does not flow through the secondary side, so that the secondary side alternating current is large, which increases the coil loss of the whole transformer. This approach affects continued improvement in efficiency and increases the cost of the product (e.g., circuit board).

The second approach is to use a non-isolated converter, such as a Buck converter. In order to reduce losses and increase the efficiency of the system, primary and secondary side isolation is eliminated. However, under the condition that the input voltage is 40V-60V and the output voltage is 12V, the duty ratio of the switching tube is very small in the traditional Buck circuit, which can lead to the fact that the effective value of the switching tube current is large, the Buck circuit cannot work at the optimal efficiency point, and the efficiency cannot be continuously improved.

Therefore, there is a strong need in the industry for a new solution to boost the efficiency of 40V-60V bus voltage to 12V conversion.

Disclosure of Invention

The present invention proposes a DC-DC conversion device comprising: a DC-DC converter comprising: the first switching unit comprises a first switching tube and a fourth switching tube which are sequentially connected in series between the positive end of the input voltage and a first node, and a second switching tube and a third switching tube which are sequentially connected in series between the positive end of the input voltage and a second node; the second switching unit comprises a sixth switching tube and a seventh switching tube which are sequentially connected in series between the first end of the output inductor and the negative end of the input voltage, and a fifth switching tube and an eighth switching tube which are sequentially connected in series between the first end of the output inductor and the negative end of the input voltage; the primary winding of the transformer has a first end connected with the common node of the first switching tube and the fourth switching tube and a second end connected with the common node of the second switching tube and the third switching tube; the first end of the secondary winding of the transformer is connected with a common node of the sixth switching tube and the seventh switching tube, and the second end of the secondary winding of the transformer is connected with a common node of the fifth switching tube and the eighth switching tube; the second end of the output inductor is used for being connected with the first end of the output capacitor; the controller is configured to receive a sampling signal from the DC-DC converter, so as to output a switching control signal to control the DC-DC converter to sequentially operate in a first operation mode, a second operation mode, a third operation mode and a second operation mode in one switching period, wherein in the first operation mode, the first switching tube, the third switching tube, the fifth switching tube and the seventh switching tube are conducted, and the second switching tube, the fourth switching tube, the sixth switching tube and the eighth switching tube are turned off; in the second working mode, the first switching tube to the fourth switching tube are turned off, and the fifth switching tube to the eighth switching tube are turned on; in a third working mode, the second switching tube, the fourth switching tube, the sixth switching tube and the eighth switching tube are conducted, the first switching tube, the third switching tube, the fifth switching tube and the seventh switching tube are turned off, wherein the first node and the second node are connected with the second switching unit and the primary and secondary windings of the transformer to couple, so that current flowing through the primary winding of the transformer and current flowing through the secondary winding of the transformer flow to a load connected with an output capacitor.

Further, the second end of the primary winding of the transformer is coupled to the homonymous end of the first end of the secondary winding of the transformer.

Further, a first end of the primary winding of the transformer is coupled to a second end of the secondary winding of the transformer.

Further, the turn ratio of the primary winding of the transformer to the secondary winding of the transformer is 2:1.

Furthermore, the primary winding of the transformer adopts two turns, and the secondary winding of the transformer adopts one turn.

Further, the current flowing through the secondary winding of the transformer is 2/3Io, where Io is the current flowing to the load connected to the output capacitor.

Further, the second end of the output capacitor is connected with the negative end of the input voltage.

Further, the first node is connected with the common node of the sixth switching tube and the seventh switching tube, and the second node is connected with the common node of the fifth switching tube and the eighth switching tube.

Further, the first node and the second node are both connected to a common node of the fifth switching tube and the sixth switching tube.

The present application also provides a DC-DC converter comprising: the first switching unit comprises a first switching tube and a fourth switching tube which are sequentially connected in series between the positive end of the input voltage and a first node, and a second switching tube and a third switching tube which are sequentially connected in series between the positive end of the input voltage and a second node; the second switching unit comprises a sixth switching tube and a seventh switching tube which are sequentially connected in series between the first end of the output inductor and the negative end of the input voltage, and a fifth switching tube and an eighth switching tube which are sequentially connected in series between the first end of the output inductor and the negative end of the input voltage; the primary winding of the transformer has a first end connected with the common node of the first switching tube and the fourth switching tube and a second end connected with the common node of the second switching tube and the third switching tube; the first end of the secondary winding of the transformer is connected with a common node of the sixth switching tube and the seventh switching tube, and the second end of the secondary winding of the transformer is connected with a common node of the fifth switching tube and the eighth switching tube; and the second end of the output inductor is used for being connected with the first end of the output capacitor, wherein the first node and the second node are connected with the second switch unit and the primary and secondary windings of the transformer to be coupled, so that currents flowing through the primary winding of the transformer and the secondary winding of the transformer flow to a load connected with the output capacitor.

Drawings

Fig. 1 is a schematic diagram of a DC-DC converter according to an embodiment of the invention.

Fig. 2 is a schematic diagram of a DC-DC converter according to a first embodiment of the present invention.

Fig. 3 is a schematic diagram of a DC-DC converter according to a second embodiment of the present invention.

Fig. 4 is a schematic diagram illustrating a current flow when the DC-DC converter of the first embodiment is operated in the first operation mode.

Fig. 5 is a schematic diagram of an operational waveform of a DC-DC converter.

Fig. 6 is a schematic diagram illustrating a current flow when the DC-DC converter of the second embodiment is operated in the first operation mode.

Fig. 7 is a schematic diagram of a current flow when the DC-DC converter of the first embodiment is operated in the second operation mode.

Fig. 8 is a schematic diagram illustrating a current flow when the DC-DC converter of the second embodiment is operated in the second operation mode.

Fig. 9 is a schematic diagram illustrating a current flow when the DC-DC converter of the first embodiment is operated in the third operation mode.

Fig. 10 is a schematic diagram illustrating a current flow when the DC-DC converter of the second embodiment is operated in the third operation mode.

Fig. 11 is a schematic diagram of a typical full-bridge inverter circuit.

Detailed Description

The following description of the embodiments of the present invention will be made more apparent and fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In one embodiment of the present invention, a DC-DC converter is provided. Specifically, referring to fig. 1, a schematic diagram of a DC-DC converter according to an embodiment of the present invention includes:

the DC-DC converter 100 includes:

the first switching unit 110 includes a first switching tube S1 and a fourth switching tube S4 sequentially connected in series between the input voltage positive terminal vin+ and the first node M, and a second switching tube S2 and a third switching tube S3 sequentially connected in series between the input voltage positive terminal vin+ and the second node N;

the second switching unit 120 includes a sixth switching tube S6 and a seventh switching tube S7 sequentially connected in series between the first end of the output inductor Lo and the negative input voltage terminal Vin-, and a fifth switching tube S5 and an eighth switching tube S8 sequentially connected in series between the first end of the output inductor Lo and the negative input voltage terminal Vin-;

the primary winding Np of the transformer is connected with a common node of the first switching tube S1 and the fourth switching tube S4 at a first end and connected with a common node of the second switching tube S2 and the third switching tube S3 at a second end;

the transformer secondary winding Ns is connected with a common node of a sixth switching tube S6 and a seventh switching tube S7 at a first end and connected with a common node of a fifth switching tube S5 and an eighth switching tube S8 at a second end;

the second end of the output inductor Lo is used for being connected with the first end of the output capacitor Co;

the controller 300 is configured to receive a sampling signal from the DC-DC converter 100, and to output a switching control signal to control the DC-DC converter 100 to sequentially operate in a first operation mode, a second operation mode, a third operation mode and a second operation mode in one switching period, wherein in the first operation mode, the first switching tube S1, the third switching tube S3, the fifth switching tube S5 and the seventh switching tube S7 are turned on, and the second switching tube S2, the fourth switching tube S4, the sixth switching tube S6 and the eighth switching tube S8 are turned off; in the second working mode, the first switching tube S1 to the fourth switching tube S4 are turned off, and the fifth switching tube S5 to the eighth switching tube S8 are turned on; in the third working mode, the second switching tube S2, the fourth switching tube S4, the sixth switching tube S6 and the eighth switching tube S8 are conducted, the first switching tube S1, the third switching tube S3, the fifth switching tube S5 and the seventh switching tube S7 are disconnected,

the first node M and the second node N are connected to the second switching unit 120 and the primary winding and the secondary winding of the transformer are coupled, so that the current flowing through the primary winding Np of the transformer flows to the load Rload connected to the output capacitor Co, and the current flowing through the secondary winding Ns of the transformer also flows to the load connected to the output capacitor Co.

In an embodiment, referring to the schematic diagram of the DC-DC converter in an embodiment of the invention shown in fig. 2, the first node M is connected to the common node of the sixth switching tube S6 and the seventh switching tube S7, and the second node N is connected to the common node of the fifth switching tube S5 and the eighth switching tube S8.

In an embodiment, referring to a schematic diagram of a DC-DC converter in another embodiment of the invention shown in fig. 3, the first node M and the second node N are both connected to a common node of the fifth switching tube S5 and the sixth switching tube S6.

Fig. 1 exemplifies a DC-DC converter 100 shown in fig. 2. Of course, it may also be the DC-DC converter 200 shown in fig. 3.

In one embodiment, the second end of the primary winding Np of the transformer is coupled with the first end of the secondary winding Ns of the transformer at the same name, as shown in fig. 2 and 3. In another embodiment, a first end of the primary winding Np of the transformer is homonymous to a second end of the secondary winding Ns of the transformer. As long as the coupling is such that the current flowing through the primary winding Np of the transformer and the secondary winding Ns of the transformer is equalized to the load connected to the output capacitor Co.

The turn ratio of the primary winding Np of the transformer to the secondary winding Ns of the transformer is n1: n2. Specifically, in one embodiment, for a transformation of 40V-60V input to 12V output, that is, an input voltage received between the positive terminal vin+ of the input voltage and the negative terminal Vin-of the input voltage is between 40V-60V, the output voltage Vo formed across the output capacitor Co is 12V, and n1:n2=2:1 is selected, and the principle thereof will be described later. That is, the primary winding Np of the transformer may take two turns and the secondary winding Ns of the transformer may take one turn. Of course, other numbers of turns may be used for the primary winding Np and the secondary winding Ns of the transformer, as long as the relationship n1:n2=2:1 is satisfied. The 40V, 60V, and 12V described above may have certain errors, which are common in power converters, as long as the errors are within acceptable limits.

Specifically, referring to fig. 4, a schematic diagram of a current flow when the control DC-DC converter 100 in fig. 1 operates in a first operation mode is shown. Please refer to the schematic diagram of the operation waveforms of the DC-DC converter shown in fig. 5. Specifically, the duty ratio D is a ratio of on time to the switching period of the switching tube, and the DC-DC converter 100 operates in the first operation mode, and the controller 300 turns on the first switching tube S1, the third switching tube S3, the fifth switching tube S5, and the seventh switching tube S7 according to the switching control signals B and a_inverse output by the sampling signals, and turns off the second switching tube S2, the fourth switching tube S4, the sixth switching tube S6, and the eighth switching tube S8 according to the switching control signals a and b_inverse output by the sampling signals. When the input voltage Vin is applied to the transformer winding Np and the transformer secondary winding Ns, and when n1:n2=2:1, the voltage on the transformer secondary winding Ns is 1/3Vin, that is, the voltage drop on the transformer secondary winding Ns can be realized to be 1/3Vin by two turns of the transformer primary winding Np by one turn of the transformer secondary winding Ns.

With continued reference to fig. 4, the primary current Ip (also referred to as an input current) flows from the positive input voltage terminal vin+ through the first switch tube S1, the primary winding Np, the third switch tube S3, the fifth switch tube S5 and the output inductor Lo, and then flows to the load connected to the output capacitor Co, and returns to the negative input voltage terminal Vin-, and the primary current Ip gradually increases, as shown in fig. 5. Meanwhile, according to the basic principle of the transformer, the primary current Ip flowing through the primary winding Np of the transformer induces a secondary current Is in the secondary winding Ns of the transformer, if is=2χip according to the relationship between the primary winding Np of the transformer and the secondary winding Ns of the transformer, it Is known that the secondary current Is sequentially flows through the conducted fifth switching tube S5, the output inductor Lo, and the load connected to the output capacitor Co according to the coupling relationship between the primary winding Np of the transformer and the secondary winding Ns of the transformer, and then returns to the secondary winding Ns of the transformer through the conducted seventh switching tube S7. From the above analysis, in the first operation mode, the primary winding Np of the transformer flows through a current of 1/3ILo, the secondary winding Ns of the transformer flows through a current of 2/3ILo, and ILo is the current flowing through the output inductor Lo. And, the current of the primary winding Np of the transformer and the secondary winding Ns of the transformer flows through the output inductance Lo to the load. At this time, the output inductor Lo is excited.

When the control DC-DC converter in fig. 1 is the DC-DC converter 200 shown in fig. 3. Referring to fig. 6, when the DC-DC converter 200 operates in the first operation mode, a current flow is schematically shown, and a primary current Ip flows from the positive end vin+ of the input voltage through the first switch tube S1, the primary winding Np of the transformer, the third switch tube S3 and the output inductor Lo, then flows to the load connected to the output capacitor Co, and returns to the negative end Vin-, where the same primary current Ip gradually increases, as shown in fig. 5. As in fig. 4, according to the basic principle of the transformer, the secondary current is=2xip induced by the secondary winding Ns of the transformer, and according to the coupling relationship of the primary and secondary windings of the transformer, it can be known that the secondary current Is flows sequentially through the turned-on fifth switching tube S5, the output inductor Lo, and the load connected to the output capacitor Co, and then returns to the secondary winding Ns of the transformer through the turned-on seventh switching tube S7. Similarly, in the first mode of operation, the primary winding Np of the transformer is supplied with 1/3ILo, the secondary winding Ns of the transformer is supplied with 2/3ILo, and ILo is supplied with the output inductor Lo. The current of the primary winding Np of the transformer and the secondary winding Ns of the transformer flows through the output inductance Lo to the load. At this time, the output inductor Lo is excited.

Next, please refer to fig. 7, which illustrates a schematic diagram of a current flow when the DC-DC converter shown in fig. 1 is operated in the second operation mode, and fig. 5. At times t2 to t3, that is, in the time period dts+td to Ts/2-td (where td is the dead time of the switching tube driving, here, the time between t1 to t 2), the DC-DC converter 100 operates in the second operation mode, the controller 300 turns off the first switching tube S1 to the fourth switching tube S4 according to the switching control signals a and B output by the sampling signals being at low level, and the controller 300 turns on the fifth switching tube S5 to the sixth switching tube S8 according to the switching control signals b_inverse and a_inverse output by the sampling signals being at high level. The primary current Ip and the secondary current Is are both zero, the output inductor Lo freewheels through the conducted eighth switching tube S8 and the conducted fifth switching tube S5 to form a first freewheeling current ILo1, the output inductor Lo freewheels through the conducted seventh switching tube S7 and the conducted sixth switching tube S6 to form a second freewheeling current ILo2, and the first freewheeling current ILo1 and the second freewheeling current ILo2 jointly form the freewheeling current ILo of the output inductor Lo. As shown in fig. 5, the primary current Ip and the secondary current Is are both zero. As shown in fig. 5, the freewheel current ILo gradually decreases during the freewheel phase of the output inductance Lo.

When the control DC-DC converter in fig. 1 is the DC-DC converter 200 shown in fig. 3. Referring to fig. 8, a schematic diagram of current flow when the DC-DC converter 200 operates in the second operation mode is shown, which is the same as the current flow when the DC-DC converter 100 operates in the second operation mode shown in fig. 7, and the principle thereof is the same and will not be described herein.

Next, please refer to fig. 9, which illustrates a current flow diagram of the DC-DC converter of fig. 1 in a third operation mode, and fig. 5. At time t4 to time t5, that is, in a period from Ts/2 to (1/2+D) Ts, the DC-DC converter 100 operates in the third operation mode, the controller 300 turns on the second switching tube S2, the fourth switching tube S4, the sixth switching tube S6 and the eighth switching tube S8 according to the switching control signals B and a_inverse output by the sampling signals, and the controller 300 turns off the first switching tube S1, the third switching tube S3, the fifth switching tube S5 and the seventh switching tube S7 according to the switching control signals a and b_inverse output by the sampling signals. The voltage drop across the secondary winding Ns of the transformer is Vin1/3 as in the first mode of operation, except that the voltages across the primary winding Np and the secondary winding Ns of the transformer are reversed with respect to those in the first mode of operation.

With continued reference to fig. 9, the primary current Ip flows from the positive input voltage terminal vin+ through the turned-on second switching tube S2, the primary winding Np of the transformer, the turned-on fourth switching tube S4, the turned-on sixth switching tube S6 and the output inductor Lo in sequence, then flows to the load connected to the output capacitor Co, returns to the negative input voltage terminal Vin-, and gradually increases, as shown in fig. 5, except that the primary current Ip in the third operation mode is opposite to the primary current Ip in the first operation mode. Meanwhile, according to the basic principle of the transformer, the primary current Ip flowing through the primary winding Np of the transformer induces a secondary current Is in the secondary winding Ns of the transformer, if is=2χip according to the relationship between the primary winding Np of the transformer and the secondary winding Ns of the transformer, it Is known that the secondary current Is sequentially flows through the conducted sixth switching tube S6, the output inductor Lo, and the load connected to the output capacitor Co according to the coupling relationship between the primary winding Np of the transformer and the secondary winding Ns of the transformer, and then returns to the secondary winding Ns of the transformer through the conducted eighth switching tube S8. From the above analysis, in the third operation mode, the current flowing through the primary winding Np of the transformer is 1/3ILo, and the current flowing through the secondary winding Ns of the transformer is 2/3ILo. The current of the primary winding Np of the transformer and the secondary winding Ns of the transformer flows through the output inductance Lo to the load. At this time, the output inductor Lo is excited again.

When the control DC-DC converter in fig. 1 is the DC-DC converter 200 shown in fig. 3. Referring to fig. 10, when the DC-DC converter 200 operates in the third mode, the current flows to the schematic diagram, and the primary current Ip flows from the positive end vin+ of the input voltage through the second switch tube S2, the primary winding Np of the transformer, the fourth switch tube S4 and the output inductor Lo, then flows to the load connected to the output capacitor Co, and returns to the negative end Vin-, where the same primary current Ip gradually increases, as shown in fig. 5. As in fig. 9, according to the basic principle of the transformer, the secondary current is=2xip induced by the secondary winding Ns of the transformer, and according to the coupling relation of the primary and secondary windings of the transformer, it can be known that the secondary current Is flows sequentially through the conducted sixth switching tube S6, the output inductor Lo, and the load connected to the output capacitor Co, and then returns to the secondary winding Ns of the transformer through the conducted eighth switching tube S8. Similarly, in the third mode of operation, the primary winding Np of the transformer is supplied with 1/3ILo, the secondary winding Ns of the transformer is supplied with 2/3ILo, and ILo is supplied with the output inductor Lo. The current of the primary winding Np of the transformer and the secondary winding Ns of the transformer flows through the output inductance Lo to the load. At this time, the output inductor Lo is excited.

Next, at the time t6 to t7, i.e., (1/2+D) ts+td to Ts-td, the DC-DC converter 100 operates again in the second operation mode (td is still the dead time of the switching tube driving). Please refer to the above description, and detailed descriptions thereof are omitted. The DC-DC converter 200 also operates again in the second mode of operation.

As described above, in the first operation mode and the third operation mode, the output inductor Lo is excited, the current flowing through the primary winding Np of the transformer flows to the load Rload connected to the output capacitor Co, and the current flowing through the secondary winding Ns of the transformer also flows to the load connected to the output capacitor Co. In the second mode of operation, the output inductor Lo freewheels with the primary current Ip and the secondary current Is being zero.

In this way, the DC-DC converter 100 or 200 sequentially operates in the first, second, third, and second operation modes in one switching period Ts, and thus cyclically operates to convert the input voltage Vin into the output voltage Vo.

In one embodiment, the second terminal of the output capacitor Co is connected to the negative input voltage terminal Vin-, so that the primary current Ip can flow from the positive input voltage terminal vin+ to the load and back to the negative input voltage terminal Vin-. More specifically, the second terminal of the output capacitor Co is directly connected to the negative input voltage terminal Vin-.

As can be seen from the above analysis of the operation modes of the DC-DC converter 100 and the DC-DC converter 200, the primary current Ip and the secondary current Is are equalized to the output inductor, and the load Rload Is supplied. The primary side current Ip, the secondary side current Is and the current ILo flowing through the output inductor Lo are uniformly expressed according to the output current Io, and the expression of ILo Is: ilo=io; the expression of Ip is: ip=1/3 ilo=io/3; is has the expression: is=2/3 ilo=2/3 Io.

For the first solution mentioned in the prior art, an isolated converter, such as a full bridge converter, is used. Referring to fig. 11, a schematic circuit diagram of a typical full-bridge converter includes a primary side switch unit, a transformer T and a rectifying unit, wherein the transformer T physically isolates primary and secondary sides, so that both the primary and secondary sides have their own ground references, such as GND1 and GND2. In order to realize the conversion from high voltage at the primary side to low voltage at the secondary side, the number of turns of the primary side is relatively large, three turns of the primary side winding Np are needed to be selected for the conversion from 40V-60V input to 12V output, and one turn of the secondary side winding Ns is needed, namely the ratio of the primary side to the secondary side turns is 3:1 can be put into practice

The voltage drop across the secondary winding Ns of the transformer is now Vin1/3 and the 40V-60V input is converted to a 12V output in combination with the control of the switching tube. In the DC-DC converter 100 of the present invention, the voltage drop on the secondary winding Ns of the transformer is 1/3Vin by two turns of the primary winding Np of the transformer and one turn of the secondary winding Ns of the transformer, and the input of 40V-60V is converted into the output of 12V by combining the control of the switching tube. That is, compared to a conventional full-bridge converter, the DC-DC converter 100 of the present application can reduce the number of turns of the primary winding Np from three turns to two turns, and can realize the function of reducing the voltage using fewer winding turns. Transformers are the largest size devices in power converters, which have been an obstacle to the miniaturization of the converters. The DC-DC converter 100 and the DC-DC converter 200 of the present application can achieve a reduction in the number of winding turns, thereby significantly reducing the volume of the transformer, thereby reducing the volume of the entire converter, and meeting the market demand for miniaturization. And the fewer winding turns can also reduce the loss and cost of the winding.

Referring to fig. 11 again, the primary current Ip of the existing full-bridge converter does not flow to the load, resulting in a larger secondary current, specifically, the output current Io flowing to the load needs to flow through the secondary winding Ns, that Is, the secondary current is=io, but is=2/3 Io in the present application, so, compared with the existing full-bridge converter, the DC-DC converter 100 and the DC-DC converter 200 of the present application reduce the current flowing through the secondary winding Ns to 2/3Io, which greatly reduces the winding loss of the transformer, further reduces the heat dissipation pressure, so that the volume of the transformer can be further reduced, the power density of the power converter Is raised, and great convenience Is brought to the design of the power converter.

That is, the DC-DC converter 100 and the DC-DC converter 200 of the present application can reduce the number of primary winding turns and the effective value of secondary winding current, thereby greatly increasing the power converter efficiency and reducing the power converter volume and cost.

The above-described conversion of 40V-60V input to 12V output is illustrative of the advantages of the DC-DC converter of the present application, and for 40V-60V input to 12V output conversion, in combination with duty cycle control of the switches in the converter, the transformer needs to drop the voltage to 1/3Vin. According to the analysis, the existing full-bridge converter needs to select three turns of the primary winding Np and one turn of the secondary winding Ns; the DC-DC converter 100 of the present application requires only two turns of the primary winding Np and only one turn of the secondary winding Ns. Of course, the application only takes the transformation from 40V-60V input to 12V output as an example, and for other levels of voltage transformation, the principle and effect are the same, but the number of turns of the transformer can be different according to the actual input voltage and the actual output voltage, which is not described herein again.

For the second solution mentioned in the prior art, a non-isolated converter is used, such as a Buck converter, where the output voltage and the input voltage have the following relationship: vo=vin×d (D is the duty cycle of the switching tube), for a 40V-60V input to 12V output conversion, the duty cycle of the switching tube will be small, and the Buck circuit cannot operate at the optimal efficiency point. As can be seen from the above analysis, the DC-DC converter 100 or 200 of the present application has the following relationship between the output voltage and the input voltage: vo=1/3 vin×2d, the duty cycle of the switching tube can be increased due to the voltage-reducing effect of the transformer, so that the Buck circuit can work at a better efficiency point.

In one embodiment of the present application, the primary winding Np of the transformer, the secondary winding Ns of the transformer and the output inductor Lo are integrated into one magnetic element, thereby further improving the power density of the DC-DC converter.

In an embodiment of the present application, the dead time td of the switching tube driving can be optimized according to the load current and the input/output voltage, so as to realize the optimized design of the DC-DC converter efficiency.

In one embodiment of the present application, the DC-DC converter 100 and the DC-DC converter 200 further include an input capacitor Cin connected between the positive input voltage terminal vin+ and the negative input voltage terminal Vin-.

In an embodiment of the present application, the sampling signal may be one or more of an input voltage, an output voltage, an input current, an output current, a duty cycle, etc. of the DC-DC converter 100 and the DC-DC converter 200. As long as it is a signal reflecting the states of the DC-DC converter 100 and the DC-DC converter 200.

The controller 300 of the present application may be a digital controller, such as a DSP; or may be an analog controller.

In an embodiment of the present application, a DC-DC converter is also provided. Specifically, referring to the DC-DC converter 100 shown in fig. 2 and the DC-DC converter 200 shown in fig. 3, the structure, the working principle and the advantages thereof are the same, and are not described herein again.

In an embodiment of the present invention, the switching tubes (the first switching tube S1 to the sixth switching tube S6) are all implemented by including a single switching tube, and in practical application, each switching tube may include a plurality of switching tubes connected in series and/or in parallel.

In an embodiment of the present invention, the switching transistors (the first switching transistor S1 to the sixth switching transistor S6) may be metal oxide semiconductor field effect transistors, bipolar junction transistors, superjunction transistors, insulated gate bipolar transistors, gallium nitride based power devices, and/or the like. The device which can receive a switch control signal to turn on or off can be used in the industry.

In an embodiment of the present invention, as shown in fig. 2, the switching transistors are MOSFETs (metal oxide semiconductor field effect transistors) and each include a source electrode, a drain electrode and a gate electrode. The drains of the first switching tube Q1 and the second switching tube Q2 are connected to the positive input voltage terminal vin+, the source of the first switching tube Q1 is connected to the drain of the fourth switching tube Q4, the source of the second switching tube Q2 is connected to the drain of the third switching tube Q3, the source of the fourth switching tube Q4 is connected to the first node M, the source of the third switching tube Q3 is connected to the second node N, the drains of the fifth switching tube Q5 and the sixth switching tube Q6 are connected to the output inductor Lo, the source of the fifth switching tube Q5 is connected to the drain of the eighth switching tube Q8, the source of the sixth switching tube Q6 is connected to the drain of the seventh switching tube Q7, the sources of the seventh switching tube Q7 and the eighth switching tube Q8 are connected to the negative input voltage terminal Vin-, and the first node M is connected to the source of the sixth switching tube Q6 and the drain of the seventh switching tube Q7. The gates of the first to eighth switching transistors Q1 to Q8 receive the switching control signal A, B, A _inverse or b_inverse output from the controller 300. Specifically, the gates of the first switching tube Q1 and the third switching tube Q3 receive the switching control signal a; the grid electrodes of the second switching tube Q2 and the fourth switching tube Q4 receive a switching control signal B; the gates of the fifth switching tube Q5 and the seventh switching tube Q7 receive a switch control signal B_Inverse; the gates of the sixth and eighth switching transistors Q6 and Q8 receive the switching control signal a_inverse. That is, the switching control signals a_inverse received by the sixth switching tube Q6 and the eighth switching tube Q8 are inverted to the switching control signals a received by the first switching tube Q1 and the third switching tube Q3; the switching control signals b_inverse received by the fifth switching tube Q5 and the seventh switching tube Q7 are inverted with respect to the switching control signals B received by the second switching tube Q2 and the fourth switching tube Q4. And there is a dead time td between the switch control signal a_inverse and the switch control signal a, and there is a dead time td between the switch control signal b_inverse and the switch control signal B.

In an embodiment of the present invention, as shown in fig. 3, the switching transistors are MOSFETs (metal oxide semiconductor field effect transistors) and each include a source electrode, a drain electrode and a gate electrode. The drain electrodes of the first switching tube Q1 and the second switching tube Q2 are connected with an input voltage positive end vin+, the source electrode of the first switching tube Q1 is connected with the drain electrode of the fourth switching tube Q4, the source electrode of the second switching tube Q2 is connected with the drain electrode of the third switching tube Q3, the source electrode of the fourth switching tube Q4 is connected with the first node M, the source electrode of the third switching tube Q3 is connected with the second node N, the first node M and the second node N are both connected with the drain electrode of the fifth switching tube Q5 and the drain electrode of the sixth switching tube Q6, the drain electrode of the fifth switching tube Q5 and the drain electrode of the sixth switching tube Q6 are also connected with the first end of the output inductor Lo, the source electrode of the fifth switching tube Q5 is connected with the drain electrode of the eighth switching tube Q8, the source electrode of the sixth switching tube Q6 is connected with the drain electrode of the seventh switching tube Q7, and the source electrodes of the seventh switching tube Q7 and the eighth switching tube Q8 are connected with the input voltage negative end Vin-. The switching control signals A, B, A _inverse or b_inverse received by the gates of the first to eighth switching transistors Q1 to Q8 are the same as the switching transistors corresponding to the DC-DC converter 100 of fig. 2, and are not described herein.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims

1. A DC-DC conversion device, comprising:

a DC-DC converter comprising:

the first switching unit comprises a first switching tube and a fourth switching tube which are sequentially connected in series between the positive end of the input voltage and a first node, and a second switching tube and a third switching tube which are sequentially connected in series between the positive end of the input voltage and a second node;

the second switching unit comprises a sixth switching tube and a seventh switching tube which are sequentially connected in series between the first end of the output inductor and the negative end of the input voltage, and a fifth switching tube and an eighth switching tube which are sequentially connected in series between the first end of the output inductor and the negative end of the input voltage;

the primary winding of the transformer has a first end connected with the common node of the first switching tube and the fourth switching tube and a second end connected with the common node of the second switching tube and the third switching tube;

the first end of the secondary winding of the transformer is connected with a common node of the sixth switching tube and the seventh switching tube, and the second end of the secondary winding of the transformer is connected with a common node of the fifth switching tube and the eighth switching tube;

the second end of the output inductor is used for being connected with the first end of the output capacitor;

the controller is configured to receive a sampling signal from the DC-DC converter, so as to output a switching control signal to control the DC-DC converter to sequentially operate in a first operation mode, a second operation mode, a third operation mode and a second operation mode in one switching period, wherein in the first operation mode, the first switching tube, the third switching tube, the fifth switching tube and the seventh switching tube are conducted, and the second switching tube, the fourth switching tube, the sixth switching tube and the eighth switching tube are turned off; in the second working mode, the first switching tube to the fourth switching tube are turned off, and the fifth switching tube to the eighth switching tube are turned on; in the third working mode, the second switching tube, the fourth switching tube, the sixth switching tube and the eighth switching tube are conducted, the first switching tube, the third switching tube, the fifth switching tube and the seventh switching tube are turned off,

the first node and the second node are connected with the second switch unit and the primary winding and the secondary winding of the transformer are coupled, so that current flowing through the primary winding of the transformer and current flowing through the secondary winding of the transformer flow to a load connected with an output capacitor.

2. A DC-DC converter as claimed in claim 1, characterized in that the second end of the primary winding of the transformer is coupled to the same name end of the first end of the secondary winding of the transformer.

3. A DC-DC converter as claimed in claim 1, characterized in that a first end of the primary winding of the transformer is coupled to a second end of the secondary winding of the transformer.

4. A DC-DC converter according to claim 1, characterized in that the turn ratio of the primary winding of the transformer to the secondary winding of the transformer is 2:1.

5. A DC-DC converter according to claim 1 or 4, characterized in that the primary winding of the transformer has two turns and the secondary winding of the transformer has one turn.

6. A DC-DC converter according to claim 4 or 5, wherein the current flowing through the secondary winding of the transformer is 2/3Io. Where Io is the current flowing to the load connected to the output capacitor.

7. A DC-DC converter as claimed in claim 1, characterized in that the second terminal of the output capacitor is connected to the negative terminal of the input voltage.

8. A DC-DC converter according to claim 1, characterized in that the first node is connected to a common node of the sixth switching tube and the seventh switching tube, and the second node is connected to a common node of the fifth switching tube and the eighth switching tube.

9. A DC-DC converter according to claim 1, characterized in that the first node and the second node are both connected to a common node of the fifth switching tube and the sixth switching tube.

10. A DC-DC converter, comprising:

an output inductor, the second end of which is used for connecting with the first end of the output capacitor,

the first node and the second node are connected with the second switch unit and the primary winding and the secondary winding of the transformer in a coupling way, so that current flowing through the primary winding of the transformer and the secondary winding of the transformer flows to a load connected with an output capacitor.

11. A DC-DC converter according to claim 10, characterized in that the first node connects the common node of the sixth switching tube and the seventh switching tube and the second node connects the common node of the fifth switching tube and the eighth switching tube.

12. A DC-DC converter according to claim 10, wherein the first node and the second node are both connected to a common node of the fifth switching tube and the sixth switching tube.

13. A DC-DC converter according to claim 10 wherein the second end of the primary winding of the transformer is coupled to the same name end of the first end of the secondary winding of the transformer.

14. A DC-DC converter according to claim 10 wherein a first end of the primary winding of the transformer is homonymous to a second end of the secondary winding of the transformer.

15. A DC-DC converter according to claim 10, characterized in that the primary winding of the transformer takes two turns and the secondary winding of the transformer takes one turn.