CN110649822A

CN110649822A - DC/DC converter

Info

Publication number: CN110649822A
Application number: CN201911037899.3A
Authority: CN
Inventors: 仰冬冬; 孙浩; 章进法
Original assignee: Delta Electronics Shanghai Co Ltd
Current assignee: Delta Electronics Shanghai Co Ltd
Priority date: 2019-10-29
Filing date: 2019-10-29
Publication date: 2020-01-03
Also published as: CN111146954A

Abstract

The present disclosure provides a dc/dc converter, and includes a filter circuit, a first side switch circuit, an isolation transformer circuit, a second side switch circuit, and a coupling circuit. The filter circuit is electrically connected with the low-voltage side and comprises a filter capacitor and a filter inductor. The first side switch circuit, the isolation transformation circuit and the second side switch circuit convert the filtered first direct current voltage into a second direct current voltage to a high-voltage side. The coupling circuit is electrically connected to the high-voltage side and comprises a coupling winding and a diode, the coupling winding is electromagnetically coupled with the filter inductor, the diode is electrically connected between the high-voltage side and the coupling winding, when the first side switching circuit is cut off, the coupling winding receives the electric energy stored by the filter inductor through electromagnetic coupling and transmits the electric energy to the high-voltage side through the diode, and the diode blocks the electric energy of the high-voltage side from being transmitted to the low-voltage side.

Description

DC/DC converter

Technical Field

The present disclosure relates to converters, and more particularly, to a dc/dc converter.

Background

In a conventional dc/dc converter, only the electric energy at the high voltage side is converted and outputted to the low voltage side, wherein the dc/dc converter further has a filter circuit electrically connected to the low voltage side for filtering the electric energy outputted from the low voltage side. However, when the electric energy of the dc/dc converter is transmitted from the low voltage side to the high voltage side, the existing mode of the switching circuit of the dc/dc converter electrically connected to the filter circuit is in the off state when the dc/dc converter is in the start-up process or the off process, so that the electric energy stored in the filter inductor in the filter circuit cannot be converted and transmitted through the switching circuit, and is converted into the voltage of the switching element in the dc/dc converter electrically connected to the filter circuit, and thus, a large voltage spike is formed at two ends of the switching element in the dc/dc converter electrically connected to the filter circuit, which is easy to damage.

Therefore, how to develop a dc/dc converter that overcomes the above disadvantages is a urgent need.

Disclosure of Invention

An object of the present disclosure is to provide a dc/dc converter which can make a switching element less vulnerable and can make a high voltage side connected to the dc/dc converter reach a rated power more quickly.

To achieve the above objective, one embodiment of the present disclosure provides a dc/dc converter electrically connected between a low-voltage side and a high-voltage side, and including a filter circuit, a first side switch circuit, an isolation transformer circuit, a second side switch circuit, and a coupling circuit. The filter circuit is electrically connected with the low-voltage side, is used for filtering the first direct-current voltage of the low-voltage side and at least comprises a filter inductor. The first side switch circuit is electrically connected with the filter circuit and used for switching on or off so as to convert the filtered first direct current voltage into a first alternating current voltage. The isolation transformation circuit is electrically connected with the first side switch circuit to convert the first alternating voltage into a second alternating voltage. The second side switch circuit is electrically connected between the isolation transformer circuit and the high-voltage side to convert the second alternating voltage into a second direct voltage to the high-voltage side. The coupling circuit is electrically connected to the high-voltage side and comprises a coupling winding and a first diode, the coupling winding is electromagnetically coupled with the filter inductor, the first diode is electrically connected between the high-voltage side and the coupling winding, the coupling winding receives the electric energy stored on the filter inductor through electromagnetic coupling and transmits the electric energy to the high-voltage side through the first diode, and the first diode is used for blocking the electric energy of the high-voltage side from being transmitted to the low-voltage side through the coupling winding and the filter inductor.

Drawings

Fig. 1 is a schematic block diagram of a dc/dc converter according to a preferred embodiment of the present disclosure.

Fig. 2 is a schematic diagram of a detailed circuit structure of the dc/dc converter shown in fig. 1.

Description of the symbols

LV: low pressure side

HV: high pressure side

1: DC/DC converter

2: filter circuit

21: filter capacitor

211: first end

212: second end

22: filter inductor

221: first end

222: second end

3: first side switch circuit

31: a first switch element

311: first end

312: second end

32: second switch element

321: first end

322: second end

4: switch clamping circuit

41: first switch clamping circuit

411: third switching element

411 a: first end

411 b: second end

412: a first resistor

412 a: first end

412 b: second end

413: second diode

414: a first clamping capacitor

414 a: first end

414 b: second end

42: second switch clamp circuit

421: fourth switching element

421 a: first end

421 b: second end

422: second resistance

422 a: first end

422 b: second end

423: third diode

424: second clamping capacitor

424 a: first end

424 b: second end

5: isolated voltage transformation circuit

51: first-stage winding

52: second-stage winding

6: second side switch circuit

61a, 61 b: fifth switching element

62a, 62 b: sixth switching element

7: coupling circuit

71: coupling winding

72: first diode

Detailed Description

Some exemplary embodiments that incorporate the features and advantages of the present disclosure will be described in detail in the specification which follows. It is to be understood that the disclosure is capable of various modifications in various embodiments without departing from the scope of the disclosure, and that the description and drawings are to be regarded as illustrative in nature, and not as restrictive.

Referring to fig. 1 and fig. 2, fig. 1 is a schematic block diagram of a dc/dc converter according to a preferred embodiment of the present disclosure, and fig. 2 is a schematic detail circuit diagram of the dc/dc converter shown in fig. 1. The dc/dc converter 1 of the present embodiment is electrically connected between the low voltage side LV and the high voltage side HV, wherein the voltage of the low voltage side LV is, but not limited to, between 9-16V, the voltage of the high voltage side HV is, but not limited to, between 200V-500V, and the dc/dc converter 1 of the present embodiment may be a unidirectional converter, that is, the dc/dc converter 1 may convert the electric energy output by the low voltage side LV to provide the electric energy to the high voltage side HV. Preferably, the dc/dc converter 1 of the present embodiment is a bidirectional converter, that is, the dc/dc converter 1 not only can convert the electric energy output from the low voltage side LV and provide the converted electric energy to the high voltage side HV, but also can convert the electric energy output from the high voltage side HV and provide the converted electric energy to the low voltage side LV.

The dc/dc converter 1 of the present embodiment includes a filter circuit 2, a first side switch circuit 3, an isolation transformer circuit 5, a second side switch circuit 6, and a coupling circuit 7.

The filter circuit 2 is electrically connected to the low voltage side LV for filtering a first dc voltage of the low voltage side LV when the dc/dc converter 1 converts the electric energy of the low voltage side LV to provide the converted electric energy to the high voltage side HV, and the filter circuit 2 at least includes a filter inductor 22. In some embodiments, the filter circuit 2 further includes a filter capacitor 21. A first end 211 of the filter capacitor 21 is electrically connected to the positive electrode of the low voltage side LV, and a second end 212 of the filter capacitor 21 is electrically connected to the negative electrode of the low voltage side LV. The first terminal 221 of the filter inductor 22 is electrically connected to the positive pole of the low voltage side LV.

The first side switch circuit 3 is electrically connected to the filter circuit 2 and receives the filtered first dc voltage from the filter circuit 2, and the first side switch circuit 3 can be switched on or off to convert the filtered first dc voltage and output a first ac voltage. The isolation transformer circuit 5 is electrically connected to the first side switch circuit 3, and when the first side switch circuit 3 outputs the first ac voltage, the isolation transformer circuit 5 converts the first ac voltage into the second ac voltage. The second side switch circuit 6 is electrically connected between the isolation transformer circuit 5 and the high voltage side HV, and the second side switch circuit 6 can switch on or off to convert the second ac voltage when the isolation transformer circuit 5 outputs the second ac voltage to output the second dc voltage to the high voltage side HV.

One end of the coupling circuit 7 is electrically connected to the high voltage side HV, and includes a coupling winding 71 and a first diode 72, the coupling winding 71 is electromagnetically coupled to the filter inductor 22 of the filter circuit 2, an anode of the first diode 72 is electrically connected to the coupling winding 71, a cathode of the first diode 72 is electrically connected to the high voltage side HV, when the dc/dc converter 1 is in the startup process or the shutdown process, the first side switch circuit 3 is in the off mode, the coupling winding 71 can receive the electric energy stored in the filter inductor 22 due to the electromagnetic coupling with the filter inductor 22, and transmit the electric energy to the high voltage side HV through the first diode 72, and further, when the dc/dc converter 1 has been in steady-state operation and the first side switch circuit 3 is switched on or off, the first diode 72 is turned off, blocking the power on the high voltage side HV from being transmitted to the low voltage side LV via the coupling winding 71 and the filter inductor 22.

As can be seen from the above, the dc/dc converter 1 of the present disclosure includes the coupling circuit 7, when the dc/dc converter 1 is in the starting process or the shutdown process, the first side switch circuit 3 has the off mode, and the coupling circuit 7 can receive the electric energy stored in the filter inductor 22 through the electromagnetic coupling and transmit the electric energy to the high voltage side HV through the first diode 72, so that the dc/dc converter 1 of the present disclosure can discharge the electric energy stored in the filter circuit 2 to the high voltage side HV during the starting process or the shutdown process, and thus can prevent the two ends of the switch element in the first side switch circuit 3 of the present disclosure from generating voltage spikes and causing damage due to the excessive voltage. In addition, the dc/dc converter 1 of the present disclosure not only can convert the first dc power to the high-voltage side HV via the filter circuit 2, the first side switch circuit, the isolation transformer circuit 5, and the second side switch circuit 6 when the first side switch circuit 3 is turned on, but also can transmit the first dc power to the high-voltage side HV via the coupling winding 71 and the first diode 72 when the first side switch circuit 3 is turned off, so that the high-voltage side HV can reach the rated power more quickly.

The dc/dc converter 1 can also convert the electric energy output by the high voltage side HV to provide the electric energy to the low voltage side LV, that is, when the high voltage side HV outputs a third dc voltage, the second side switch circuit 6 converts the third dc voltage to a third ac voltage, the isolation transformer circuit 5 converts the third ac voltage to a fourth ac voltage, the first side switch circuit 3 converts the fourth ac voltage to a fourth dc voltage, and the filter circuit 2 filters the fourth dc voltage to output the electric energy to the low voltage side LV.

Referring to fig. 1 and fig. 2, the first side switch circuit 3 of the present embodiment includes a first switch element 31 and a second switch element 32, wherein the first switch element 31 and the second switch element 32 may be, but are not limited to, a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), an Insulated Gate Bipolar Transistor (IGBT), a gallium nitride (GaN) device or a silicon carbide (SiC) device, respectively. The first end 311 of the first switch element 31 and the first end 321 of the second switch element 32 are electrically connected to the second end 212 of the filter capacitor 21, and the conducting modes of the first switch element 31 and the second switch element 32 are different in phase by 180 degrees, in addition, when the dc/dc converter 1 is in the starting process, the duty ratios of the first switch element 31 and the second switch element 32 are respectively gradually increased from 0 to 50%, and when the dc/dc converter 1 enters the steady state operation, the duty ratios of the first switch element 31 and the second switch element 32 are greater than or equal to 50%.

The isolation transformer circuit 5 includes a first-stage winding 51 and a second-stage winding 52 that are electromagnetically coupled to each other, the first-stage winding 51 is a center tap structure, a center tap end of the first-stage winding 51 is electrically connected to the second end 222 of the filter inductor 22, a first end of the first-stage winding 51 is electrically connected to the second end 312 of the first switching element 31, and a second end of the first-stage winding 51 is electrically connected to the second end 322 of the second switching element 32.

In some embodiments, the turn ratio between the second stage winding 52 and the first stage winding 51 is greater than or equal to the turn ratio between the coupling winding 71 and the filter inductor 22, and by setting the turn ratio, during the start-up process of the dc/dc converter 1, that is, when the duty ratios of the first switching element 31 and the second switching element 32 gradually increase from 0 to 50%, respectively, the voltage of the high-voltage side HV is less than the voltage of the end of the coupling winding 71 electrically connected with the first diode 72, so that the first diode 72 is turned on, and the electric energy on the coupling winding 71 can be transmitted to the high-voltage side HV. When the dc/dc converter 1 enters a steady state operation, the voltage of the high voltage side HV can be greater than the voltage of the end of the coupling winding 71 electrically connected to the first diode 72, so that the first diode 72 is turned off to block the electric energy of the high voltage side HV from being transmitted to the coupling winding 71.

In this embodiment, the second side switch circuit 6 includes a first bridge arm and a second bridge arm connected in parallel, wherein two ends of the first bridge arm and two ends of the second bridge arm are respectively electrically connected between the positive electrode and the negative electrode of the high voltage side HV. The first arm includes two

fifth switching elements

61a and 61b connected in series, and a center point of the two

fifth switching elements

61a and 61b is electrically connected to the first end of the second winding 52 of the isolated transformer circuit 5. The second bridge arm includes two

sixth switching elements

62a and 62b connected in series, and a center point of the two

sixth switching elements

62a and 62b is electrically connected to the second end of the second-stage winding 52 of the isolation transformer circuit 5.

The dc/dc converter 1 further comprises at least one switch clamp circuit 4, such as a first switch clamp circuit 41 and a second switch clamp circuit 42 shown in fig. 2, for limiting the voltage across the first switch element 31 and the voltage across the second switch element 32, respectively. The first switch clamp circuit 41 is connected in parallel with the first switch element 31, and includes a third switch element 411, a first resistor 412, a second diode 413, and a first clamp capacitor 414. The first end 411a of the third switching element 411 is electrically connected to the first end 311 of the first switching element 31, and the first end 412a of the first resistor 412 is electrically connected to the second end 411b of the third switching element 411. A cathode of the second diode 413 is electrically connected to the first end 411a of the third switching element 411 and the first end 311 of the first switching element 31, and an anode of the second diode 413 is electrically connected to the second end 412b of the first resistor 412. A first end 414a of the first clamping capacitor 414 is electrically connected to the second end 412b of the first resistor 412 and the anode of the second diode 413, and a second end 414b of the first clamping capacitor 414 is electrically connected to the second end 312 of the first switching element 31. The second switch clamping circuit 42 is connected in parallel with the second switch element 32, and includes a fourth switch element 421, a second resistor 422, a third diode 423 and a second clamping capacitor 424, wherein a first end 421a of the fourth switch element 421 is electrically connected to the first end 321 of the second switch element 32, and a first end 422a of the second resistor 422 is electrically connected to a second end 421b of the fourth switch element 421. A cathode of the third diode 423 is electrically connected to the first end 421a of the fourth switching element 421 and the first end 321 of the second switching element 32, and an anode of the third diode 423 is electrically connected to the second end 422b of the second resistor 422. A first terminal 424a of the second clamping capacitor 424 is electrically connected to the second terminal 422b of the second resistor 422 and the cathode of the third diode 423, and a second terminal 424b of the second clamping capacitor 424 is electrically connected to the second terminal 322 of the second switching element 32.

In summary, the dc/dc converter of the present disclosure includes a coupling circuit, and when the dc/dc converter is in a start-up process or a shut-down process, the first side switch circuit has a cut-off mode, and the coupling circuit receives the electric energy stored in the filter inductor through electromagnetic coupling and transmits the electric energy to the high-voltage side through the first diode, so that the dc/dc converter of the present disclosure can discharge the electric energy stored in the filter circuit to the high-voltage side in the start-up process or the shut-down process, and thus can prevent the two ends of the switch element in the first side switch circuit of the present disclosure from generating voltage spikes and being damaged due to an excessive voltage. In addition, the dc/dc converter of the present disclosure can not only transfer the first dc power to the high voltage side through the filter circuit, the first side switch circuit, the isolation transformer circuit and the second side switch circuit when the first side switch circuit is turned on, but also transfer the first dc power to the high voltage side through the coupling winding and the first diode when the first side switch circuit is turned off, so that the high voltage side can more quickly reach the rated power.

Claims

1. A dc/dc converter electrically connected between a low voltage side and a high voltage side, comprising:

the filter circuit is electrically connected with the low-voltage side, is used for filtering a first direct-current voltage of the low-voltage side and at least comprises a filter inductor;

the first side switch circuit is electrically connected with the filter circuit and used for switching on or off so as to convert the filtered first direct current voltage into a first alternating current voltage;

an isolation transformation circuit electrically connected with the first side switch circuit for converting the first alternating voltage into a second alternating voltage;

a second side switch circuit electrically connected between the isolation transformer circuit and the high voltage side for converting the second AC voltage into a second DC voltage to the high voltage side; and

and the coupling winding receives the electric energy stored on the filter inductor through electromagnetic coupling and transmits the electric energy to the high-voltage side through the first diode, and the first diode is used for blocking the electric energy of the high-voltage side from being transmitted to the low-voltage side through the coupling winding and the filter inductor.

2. The dc/dc converter of claim 1, wherein the dc/dc converter is a bi-directional dc/dc converter.

3. The dc/dc converter of claim 1, wherein the voltage on the low side is 9-16V.

4. The DC/DC converter as claimed in claim 1, wherein the voltage at the high voltage side is 200-500V.

5. The DC/DC converter as claimed in claim 1, wherein the first side switch circuit comprises a first switch element and a second switch element, a first end of the first switch element is electrically connected to a second end of a filter capacitor and a first end of the second switch element, and the first switch element and the second switch element are conducted with a phase difference of 180 degrees.

6. The DC/DC converter as claimed in claim 5, wherein the isolated transformer circuit comprises a first winding and a second winding, the first winding is in a center-tapped configuration, a center-tapped end of the first winding is electrically connected to a second end of the filter inductor, a first end of the first winding is electrically connected to a second end of the first switching element, and a second end of the first winding is electrically connected to a second end of the second switching element.

7. The DC/DC converter of claim 6, wherein a turn ratio between the second stage winding and the first stage winding is greater than or equal to a turn ratio between the coupling winding and the filter inductor.

8. The DC/DC converter as claimed in claim 6, wherein the second side switching circuit comprises a first bridge arm and a second bridge arm connected in parallel, the first bridge arm comprises two fifth switching elements connected in series, the center point of the two fifth switching elements is electrically connected to a first end of the second winding, the second bridge arm comprises two sixth switching elements connected in series, the center point of the two sixth switching elements is electrically connected to a second end of the second winding.

9. The DC/DC converter as recited in claim 5, wherein the DC/DC converter further comprises a first switch clamp and a second switch clamp for limiting the voltage across the first switch element and the voltage across the second switch element, respectively.

10. The dc/dc converter as claimed in claim 9, wherein the first switch clamping circuit comprises a third switch element, a first resistor, a second diode and a first clamping capacitor, a first terminal of the third switch element is electrically connected to the first terminal of the first switch element, a first terminal of the first resistor is electrically connected to a second terminal of the third switch element, a cathode of the second diode is electrically connected to the first terminal of the third switch element and the first terminal of the first switch element, an anode of the second diode is electrically connected to a second terminal of the first resistor, a first terminal of the first clamping capacitor is electrically connected to the second terminal of the first resistor and the anode of the second diode, a second terminal of the first clamping capacitor is electrically connected to a second terminal of the first switch element, the second switch clamping circuit comprises a fourth switch element, a first resistor, a second diode and a first clamping capacitor, A second resistor, a third diode and a second clamping capacitor, wherein a first end of the fourth switching element is electrically connected to the first end of the second switching element, a first end of the second resistor is electrically connected to a second end of the fourth switching element, a cathode of the third diode is electrically connected to the first end of the fourth switching element and the first end of the second switching element, an anode of the third diode is electrically connected to a second end of the second resistor, a first end of the second clamping capacitor is electrically connected to the second end of the second resistor and the cathode of the third diode, and a second end of the second clamping capacitor is electrically connected to a second end of the second switching element.