Hard switch isolation DC / DC converter and electric vehicle

Abstract

The present application proposes a hard-switch isolated DC / DC conversion device and an electric vehicle, which relate to the field of power supply. For the hard-switch isolated DC / DC converter, the switch control signal of the switch tube in the primary switch unit and the secondary switch unit is controlled by the controller output, and the duty cycle of the switch control signal is adjustable, wherein when the first set condition is met, the switch control signal output by the controller causes the switch tube in the secondary switch unit to overlap and conduct for the first time with the switch tube in the primary switch unit, and the secondary winding is short-circuited during the first time. In this way, without changing the hardware circuit, the design requirement of high gain under low input can be achieved, and the hard-switch isolated DC / DC converter can meet the rated output voltage requirement within the full range of input voltage, which is better compatible with the increasingly wide high input voltage range of DC / DC converters required by current vehicle manufacturers, and at the same time improves the reliability of the hard-switch isolated DC / DC converter.

Description

Technical Field

[0001] The present application relates to the field of power supplies, in particular to a hard-switch isolated DC / DC converter and an electric vehicle. Background Art

[0002] With the development of science and technology and society, new energy vehicles have been widely used and their share is increasing.

[0003] Electric vehicles often include a high-voltage battery, which draws power from the power grid and stores the energy in the high-voltage battery, which becomes the source of power in the electric vehicle. The on-board DC-DC converter is used to convert the energy of the high-voltage battery of the electric vehicle into low-voltage battery energy, such as 12V, to power the loads in the new energy vehicle.

[0004] One type of vehicle-mounted DC-DC converter is Figure 1 The isolated DC-DC converter 100 shown in the figure has a full-bridge circuit on the primary side and a synchronous rectification circuit on the secondary side. Figure 1 As shown, the full-bridge circuit includes a first switch bridge arm formed by a first switch tube S1 and a second switch tube S2 connected in series, and a second switch bridge arm formed by a third switch tube S3 and a fourth switch tube S4 connected in series, the first switch bridge arm and the second switch bridge arm are connected in parallel to form a terminal for receiving an input voltage Vin; the transformer includes a primary winding Lp and a secondary winding Ls, and the transformer is a transformer with a center tap on the secondary winding; the synchronous rectification circuit includes a first synchronous rectification switch tube SR1 and a second synchronous rectification switch tube SR2, the first synchronous rectification switch tube SR1 and the second synchronous rectification switch tube SR2 are respectively connected between the first end and the second end of the secondary winding Ls and the ground end, and the center tap of the secondary winding Ls and the ground end form a terminal for outputting an output voltage Vout.

[0005] At present, the input voltage Vin of the vehicle-mounted DC-DC converter is increasingly required to be between 200V and 500V, or between 500V and 1000V, and the output voltage Vout is usually between 12V and 16V, that is, the vehicle-mounted DC-DC converter has a wide input voltage range, which brings many problems to the design of the vehicle-mounted DC-DC converter. In addition, in order to meet the large ratio of the vehicle-mounted DC-DC converter, a transformer with a high turns ratio is usually used.

[0006] Specifically, for Figure 1As shown in the vehicle-mounted DC-DC converter, we know that the relationship between its input voltage Vin and output voltage Vout is: (Vin / N)*2*D=Vout, where D is the duty cycle of the switch tube in the full-bridge circuit, and N is the turns ratio between the primary winding Lp and the secondary winding Ls of the transformer. It has the following problems: when the turns ratio of the transformer is selected to be small, so that when the input voltage Vin is small, such as for an input voltage of 200V to 500V, when the input voltage Vin is 200V, it can meet the requirements of the rated output voltage, such as meeting the output voltage requirement of 16V, but when the input voltage Vin increases to 500V, under this small turns ratio, the output voltage Vout will be raised very high, which will far exceed the requirements of the rated output voltage, and at the same time bring too much stress to the secondary synchronous rectification switch tube. On the contrary, when the transformer turns ratio is selected to be larger, when the input voltage VIN is larger, such as for an input voltage of 200V to 500V, when the input voltage Vin is 500V, it can meet the rated output voltage requirement, such as meeting the output voltage of 16V, but when the input voltage Vin is reduced to 200V, under this larger turns ratio, the output voltage Vout will not meet the rated output voltage requirement. The above problems make the current on-board DC-DC converter difficult to design, with poor reliability and low efficiency.

[0007] Based on this, there are currently Figure 2 Another vehicle-mounted DC-DC converter shown in FIG. 1 adopts a two-stage structure. Figure 1 The input side of the vehicle-mounted DC-DC converter 100 shown in the figure is added with a first-stage boost conversion circuit 300. The boost conversion circuit 300 works when the input voltage Vin is small to raise the input voltage of the vehicle-mounted DC-DC converter 100. The boost conversion circuit 300 does not work when the input voltage Vin is large. Figure 1 However, this undoubtedly increases the size and cost of the vehicle-mounted DC-DC converter and reduces its efficiency, which is contrary to the market trend of high efficiency, low cost and miniaturization. Summary of the invention

[0008] The present application provides a hard switch isolated DC / DC converter device, comprising:

[0009] Hard-switching isolated DC / DC converters, including:

[0010] A transformer, including a primary winding and a secondary winding;

[0011] A primary switch unit, one end of which is connected to the primary winding of the transformer via an inductor, and the other end of which is used to receive an input voltage;

[0012] A secondary switch unit, one end of which is connected to the secondary winding of the transformer, and the other end of which is used to output an output voltage;

[0013] The controller is used to output a switch control signal for controlling the switch tubes in the primary switch unit and the secondary switch unit, and the duty cycle of the switch control signal is adjustable. When a first set condition is met, the switch control signal output by the controller causes the switch tube in the secondary switch unit to overlap with the switch tube in the primary switch unit for a first time, and the secondary winding is short-circuited during the first time.

[0014] Furthermore, when the first set condition is met, the switch control signal output by the controller causes the switch tube in the secondary switch unit to delay turning off until the switch tube in the secondary switch unit overlaps with the switch in the primary switch unit for a first time.

[0015] Furthermore, the first setting condition is that the input voltage is less than the input voltage setting value, and the maximum output voltage provided by the hard-switch isolated DC / DC converter is less than the rated output voltage value.

[0016] Furthermore, the controller executes:

[0017] S1: receiving the input voltage;

[0018] S2: Determine whether the input voltage is less than the input voltage setting value, if so, proceed to step S3, if not, proceed to step S7;

[0019] S3: Calculate the maximum output voltage Vomax1 provided by the hard-switch isolated DC / DC converter according to the input voltage, the turns ratio n of the transformer and the maximum duty cycle Dmax of the switch tube in the primary switch unit;

[0020] S4: Determine whether Vomax1 is less than the rated output voltage value Vod, if so, proceed to step S5, if not, proceed to step S7, wherein step S7 is the controller controlling the hard switch isolated DC / DC converter to operate in a normal working mode;

[0021] S5: Obtaining the first time by looking up a table according to the input voltage;

[0022] S6: Delay turning off the switch tube in the secondary switch unit until the switch tube in the secondary switch unit overlaps with the switch in the primary switch unit for a first turn-on time.

[0023] Furthermore, the first setting condition is: the input voltage is less than the input voltage setting value, and the output voltage is less than the rated output voltage value.

[0024] Furthermore, the controller executes:

[0025] S1: receiving the input voltage and the output voltage;

[0026] S2: Determine whether the input voltage is less than the input voltage setting value, if so, proceed to step S3, if not, proceed to step S6;

[0027] S3: Determine whether the output voltage is less than the rated output voltage value Vod, if so, proceed to step S4, if not, proceed to step S6, wherein step S6 is the controller controlling the hard switch isolated DC / DC converter to operate in a normal working mode;

[0028] S4: Obtaining the first time by looking up a table according to the input voltage;

[0029] S5: Delay turning off the switch tube in the secondary switch unit until the switch tube in the secondary switch unit overlaps with the switch in the primary switch unit for a first turn-on time.

[0030] Furthermore, the table is a table of the relationship between the input voltage and the first time.

[0031] Furthermore, the length of the first time decreases as the input voltage increases.

[0032] Furthermore, the inductor is used to store energy during the first time.

[0033] Furthermore, the primary switch unit includes a first switch bridge arm and a second switch bridge arm, the first switch bridge arm includes a first switch tube and a second switch tube connected in series, the second switch bridge arm includes a third switch tube and a fourth switch tube connected in series, and the first switch bridge arm is connected in parallel with the second switch bridge arm to form a terminal for receiving an input voltage;

[0034] The transformer is a secondary winding with a center tap transformer;

[0035] The secondary switch unit includes a first synchronous rectifier switch tube and a second synchronous rectifier switch tube, the first synchronous rectifier switch tube and the second synchronous rectifier switch tube are respectively connected between the first end and the second end of the secondary winding and the ground end, and the center tap of the secondary winding and the ground end form a terminal for outputting an output voltage;

[0036] When the first set condition is met, the switch control signal output by the controller causes the first synchronous rectification switch tube to overlap with the first switch tube and the fourth switch tube for the first time, and the second synchronous rectification switch tube to overlap with the second switch tube and the third switch tube for the first time.

[0037] Furthermore, when the first set condition is met, the switch control signal output by the controller causes the first synchronous rectifier switch tube to delay shutdown until it overlaps with the first switch tube and the fourth switch tube for the first time, and the second synchronous rectifier switch tube to delay shutdown until it overlaps with the second switch tube and the third switch tube for the first time.

[0038] Furthermore, in the normal operation mode, the controller calculates the duty cycle of the switch control signal according to the input voltage, the desired output voltage and the transformer turns ratio, and outputs the switch control signal according to the calculated duty cycle of the switch control signal.

[0039] The present application also proposes an electric vehicle, comprising: the hard switch isolation DC / DC converter device

[0040] The features and technical advantages of the present disclosure have been summarized quite extensively above so that the detailed description disclosed below may be better understood. Additional features and advantages of the present disclosure will be described below, which constitute the subject matter of the claims of the present disclosure. It will be appreciated by those skilled in the art that the disclosed concepts and specific embodiments may be easily used as a basis for modifying or designing other structures or processes for achieving the same purpose of the present disclosure. It will also be appreciated by those skilled in the art that such equivalent structures do not depart from the spirit and scope of the present disclosure as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description in conjunction with the accompanying drawings, in which:

[0042] Figure 1 A schematic diagram of a vehicle-mounted DC-DC converter circuit is shown;

[0043] Figure 2 Another schematic diagram of a vehicle-mounted DC-DC converter circuit is shown;

[0044] Figure 3 A schematic diagram of a hard switch isolated DC / DC converter device according to an embodiment of the present application is shown;

[0045] Figure 4 A control flow chart of an embodiment of the present application is shown;

[0046] Figure 5 A control flow chart of another embodiment of the present application is shown;

[0047] Figure 6 A schematic diagram showing the relationship between the input voltage, the rated output voltage and the working mode of a specific embodiment of the present application is shown;

[0048] Figure 7 A schematic diagram of a hard switch isolated DC / DC converter device according to a specific embodiment of the present application is shown;

[0049] Figure 8 Shows Figure 7 Schematic diagram of working waveform of hard switch isolated DC / DC converter;

[0050] Fig. 9 Shows Figure 7 A structural schematic diagram of the hard-switching isolated DC / DC converter in the embodiment of the present invention when the hard-switching isolated DC / DC converter operates in the first mode;

[0051] Fig.10 Shows Figure 7 A structural diagram of the hard-switching isolated DC / DC converter in the embodiment of the present invention when operating in the second mode;

[0052] Fig.11 Shows Figure 7 A structural diagram of the hard-switching isolated DC / DC converter in FIG. 1 when operating in the third mode;

[0053] Fig.12 Shows Figure 7 Schematic diagram of the structure of the hard-switching isolated DC / DC converter operating in the fourth mode.

[0054] Unless otherwise indicated, corresponding parts and symbols in the different figures generally refer to corresponding parts. These figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale. DETAILED DESCRIPTION

[0055] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0056] See also Figure 3 Schematic diagram of a hard switch isolated DC / DC converter device according to an embodiment of the present application is shown. Figure 3 As shown, the hard-switch isolated DC / DC conversion device includes a hard-switch isolated DC / DC converter 100 and a controller 200 .

[0057] like Figure 3 As shown, the hard-switched isolated DC / DC converter 100 includes a transformer 130, including a primary winding Lp and a secondary winding Ls; a primary switch unit 110, one end of which is connected to the primary winding Lp of the transformer 130 through an inductor Lk, and the other end is used to receive an input voltage Vin; a secondary switch unit 120, one end of which is connected to the secondary winding Ls of the transformer, and the other end is used to output an output voltage Vout.

[0058] in this way, Figure 3 The hard-switching isolated DC / DC converter 100 in the embodiment is used to convert the input voltage Vin into the output voltage Vout, wherein the relationship between the input voltage Vin and the output voltage Vout is:

[0059] (Vin / N)*2*D=Vout, where D is the duty cycle of the switch tube in the primary switch unit 110, and N is the turns ratio between the primary winding Lp and the secondary winding Ls of the transformer.

[0060] and, Figure 3 The input voltage Vin of the hard-switched isolated DC / DC converter 100 has a wide range, such as 200V to 500V, or 500V to 1000V. The output voltage Vout is used to power the load in the new energy vehicle, which can be between 12V and 16V.

[0061] For isolated DC / DC converters, variable frequency control can be used, and the switch tube in the isolated DC / DC converter is realized as a soft switch; duty cycle control under fixed frequency can also be used, and the switch tube in the isolated DC / DC converter is realized as a hard switch, that is, a hard-switched isolated DC / DC converter is formed. Hard-switched isolated DC / DC converters have become the first choice for many applications due to their many advantages such as simple control and high reliability.

[0062] like Figure 3 As shown, the controller 200 is used to output a switch control signal for controlling the switch tubes in the primary switch unit 110 and the secondary switch unit 120, and the duty cycle of the switch control signal is adjustable. When a first set condition is met, the switch control signal output by the controller 200 causes the switch tube in the secondary switch unit to overlap with the switch tube in the primary switch unit for a first time, and the secondary winding Ls is short-circuited during the first time.

[0063] Specifically, the first setting condition is: under the current input voltage Vin, the output voltage Vout that the hard-switch isolated DC / DC converter 100 can provide is less than the rated output voltage. We know that once the hard-switch isolated DC / DC converter is designed, the switch devices and transformers therein cannot be changed during the application process. In order to improve the reliability of the hard-switch isolated DC / DC converter 100, the transformer designed in this application satisfies that when the input voltage Vin is the maximum value, the output voltage Vout will not exceed the stress range of the switch tube in the secondary switch unit. However, this results in that when the input voltage Vin is small, the output voltage Vout cannot meet the rated output voltage requirement. Based on this, when the first setting condition is met, the switch control signal output by the controller 200 provided in this application causes the switch tube in the secondary switch unit to overlap with the switch tube in the primary switch unit for the first time, and the secondary winding Ls is short-circuited during the first time. Since the secondary winding Ls is short-circuited during the first time, the inductor Lk stores energy through the switch tube in the turned-on primary switch unit, and releases the energy in the subsequent stage to form a step-up conversion stage, which can increase the gain of the hard-switch isolated DC / DC converter 100, and make the output voltage Vout of the hard-switch isolated DC / DC converter 100 still meet the rated output voltage requirement under the first setting condition. In this way, without changing the hardware circuit, the design requirement of high gain under low input can be achieved, and the hard-switch isolated DC / DC converter 100 can meet the rated output voltage requirement within the full range of input voltage, which is better compatible with the increasingly wide high input voltage range of DC / DC converters currently required by vehicle manufacturers, and at the same time improves the reliability of the hard-switch isolated DC / DC converter 100.

[0064] In a specific implementation, the inductor Lk is only used to store energy in the first time and release energy in the subsequent stage. Its inductance value can meet the needs of storing and releasing energy at the microhenry level. Specifically, it can be about ten microhenries. In a specific implementation, the inductor Lk can be implemented as an independent magnetic component, or it can be implemented as integrated in the transformer 130, and specifically it can be the leakage inductance of the transformer 130.

[0065] like Figure 3 In the embodiment, the inductor Lk is connected between the primary switch unit 110 and the first end of the primary winding Lp. Of course, the inductor Lk can also be connected between the primary switch unit 110 and the second end of the primary winding Lp. As long as the energy storage loop and the discharge loop can be formed.

[0066] In a specific embodiment, the first setting condition is: the input voltage Vin is less than the input voltage setting value Vind, and the maximum output voltage Vomax provided by the hard-switch isolated DC / DC converter is less than the rated output voltage value Vod. That is, for the designed hard-switch isolated DC / DC converter 100, under the current input voltage Vin, the maximum output voltage Vomax that the hard-switch isolated DC / DC converter can provide still cannot reach the rated output voltage value Vod, and cannot meet the working requirements of the load. Therefore, at this time, it is necessary to increase the gain of the hard-switch isolated DC / DC converter 100 to increase its output voltage so that it meets the requirements of the rated output voltage value Vod.

[0067] For specific implementation, please refer to Figure 4 In the control flow chart of an embodiment of the present application shown, the controller 200 executes: S1: receiving the input voltage Vin;

[0068] S2: Determine whether the input voltage Vin is less than the input voltage setting value Vind, if so, proceed to step S3, if not, proceed to step S7;

[0069] S3: Calculate the maximum output voltage Vomax1 provided by the hard-switch isolated DC / DC converter according to the input voltage Vin, the turns ratio n of the transformer and the maximum duty cycle Dmax of the switch tube in the primary switch unit;

[0070] S4: Determine whether Vomax1 is less than the rated output voltage value Vod. If so, proceed to step S5. If not, proceed to step S7. Step S7 is for the controller to control the hard switch DC / DC conversion to work in the normal working mode.

[0071] S5: Obtaining a first time td by looking up a table according to the input voltage Vin;

[0072] S6: Delay turning off the switch tube in the secondary switch unit 120 until the switch tube in the secondary switch unit overlaps with the switch in the primary switch unit for a first time td.

[0073] As described above, when the input voltage Vin is less than the input voltage setting value V1d, and the maximum output voltage Vomax provided by the hard-switch isolated DC / DC converter is less than the rated output voltage value Vod, the hard-switch isolated DC / DC converter 100 forms a step-up conversion stage, thereby increasing the gain of the hard-switch isolated DC / DC converter 100 and further increasing the output voltage of the hard-switch isolated DC / DC converter 100.

[0074] In a specific embodiment, the first setting condition is: the input voltage Vin is less than the input voltage setting value Vind, and the output voltage Vout is less than the rated output voltage value Vod. That is, for the designed hard-switch isolated DC / DC converter 100, by detecting the input voltage Vin and the output voltage Vout of the hard-switch isolated DC / DC converter 100, if the input voltage Vin is less than the input voltage setting value Vind, and the output voltage Vout is less than the rated output voltage value Vod, it means that the hard-switch isolated DC / DC converter 100 cannot meet the working requirements of the load, so at this time, it is necessary to increase the gain of the hard-switch isolated DC / DC converter 100 to increase its output voltage so that it meets the requirements of the rated output voltage value Vod.

[0075] For specific implementation, please refer to Figure 5 As shown in the control flow chart of another embodiment of the present application, the controller 200 executes:

[0076] S1: receiving the input voltage Vin and the output voltage Vout;

[0077] S2: Determine whether the input voltage Vin is less than the input voltage setting value Vind, if so, proceed to step S3, if not, proceed to step S6;

[0078] S3: Determine whether the output voltage Vout is less than the rated output voltage value Vod, if so, proceed to step S4, if not, proceed to step S6, wherein step S6 is the controller controlling the hard switch DC / DC conversion to work in the normal working mode;

[0079] S4: Obtain the first time td by looking up a table according to the input voltage Vin;

[0080] S5: Delay turning off the switch in the secondary switch unit 120 until the switch in the secondary switch unit overlaps with the switch in the primary switch unit for a first time td.

[0081] As described above, when the input voltage Vin is less than the input voltage setting value V1d, and the output voltage Vout is less than the rated output voltage value Vod, the hard-switch isolated DC / DC converter 100 is controlled to form a step-up conversion stage, thereby increasing the gain of the hard-switch isolated DC / DC converter 100, thereby increasing the output voltage of the hard-switch isolated DC / DC converter 100.

[0082] See also Figure 6 The relationship between the input voltage, rated output voltage and working mode is shown in FIG. Figure 6As shown, when the input voltage Vin is small, if the rated output voltage value Vod is also small, the hard switch isolated DC / DC converter 100 can be controlled to work in the normal working mode, and the output voltage requirement can still be met; when the input voltage Vin is large, no matter the rated output voltage value Vod is large or small, the hard switch isolated DC / DC converter 100 can be controlled to work in the normal working mode, and the output voltage requirement can still be met; and only when the input voltage Vin is small and the rated output voltage value Vod is large, if the hard switch isolated DC / DC converter 100 is still controlled to work in the normal working mode, the output voltage requirement cannot be met, then at this time, the hard switch isolated DC / DC converter 100 is controlled to form the above-mentioned boost conversion stage, and the gain of the hard switch isolated DC / DC converter 100 is raised in this stage.

[0083] In actual implementation, the table is a table of the relationship between the input voltage Vin and the first time td. Specifically, the controller 200 determines whether the first setting condition is met according to the detection signal, and if so, the controller 200 obtains the first time td by looking up the table according to the current input voltage Vin.

[0084] In actual implementation, the table is obtained by performing an open-loop test on the hard-switch isolated DC / DC converter, that is, under different input voltages Vin, first times td of different sizes are applied to detect the output voltage Vout of the hard-switch isolated DC / DC converter, and when the output voltage Vout meets the rated output voltage value Vod, the input voltage Vin and the corresponding first time td are recorded, and a relationship table between the input voltage Vin and the first time td of the hard-switch isolated DC / DC converter is obtained through a limited number of experiments.

[0085] Furthermore, in the table, the length of the first time td decreases as the input voltage Vin increases. When the input voltage Vin is smaller, the output voltage Vout that the hard-switch isolated DC / DC converter 100 can provide is smaller, and the gain that needs to be raised is more. At this time, the gain of the boost stage can be increased by increasing the length of the first time td and increasing the energy storage time of the inductor Lk, thereby increasing the gain of the hard-switch isolated DC / DC converter 100.

[0086] In a specific embodiment, the hard-switched isolated DC / DC converter 100 is implemented as Figure 7 In a specific embodiment shown in FIG. 1 , the primary switch unit 110 is implemented as a full-bridge circuit, and the secondary switch unit 120 adopts a synchronous rectification circuit. For details, please refer to FIG. Figure 7The primary switch unit 110 includes a first switch bridge arm formed by a first switch tube S1 and a second switch tube S2 connected in series, and a second switch bridge arm formed by a third switch tube S3 and a fourth switch tube S4 connected in series, and the first switch bridge arm is connected in parallel with the second switch bridge arm to form a terminal for receiving an input voltage Vin. Specifically, the primary side may also include an input capacitor Cin, and the input capacitor Cin is connected in parallel with the first switch bridge arm and the second switch bridge arm. The transformer includes a primary winding Lp and a secondary winding Ls, and the transformer is a transformer with a center tap N on the secondary winding. The secondary switch unit 120 includes a first synchronous rectifier switch tube SR1 and a second synchronous rectifier switch tube SR2, and the first synchronous rectifier switch tube SR1 and the second synchronous rectifier switch tube SR2 are respectively connected between the first end and the second end of the secondary winding Ls and the ground end, and the center tap N of the secondary winding Ls and the ground end form a terminal for outputting the output voltage Vout. Specifically, the secondary side may further include an output filter unit, the output filter unit includes an output filter inductor L1 and an output capacitor Cout, the output capacitor Cout is connected in parallel with the output terminal, and the output filter inductor L1 is connected between the positive output terminal and the center tap N.

[0087] When the first setting condition is met, the switch control signal output by the controller 200 causes the first synchronous rectification switch tube SR1 to overlap with the first switch tube S1 and the fourth switch tube S4 for the first time td, and the second synchronous rectification switch tube SR2 to overlap with the second switch tube S2 and the third switch tube S3 for the first time.

[0088] See also Figure 8 shown Figure 7 The working waveform diagram of the hard switch isolation DC / DC converter in FIG. Figure 8 As shown, when the first switch tube S1 and the fourth switch tube S4 are turned on, the body diode of the second synchronous rectification switch tube SR2 is turned on synchronously, or the second synchronous rectification switch tube SR2 is turned on synchronously. If the first synchronous rectification switch tube SR1 is also turned on at this time, the body diodes of the first synchronous rectification switch tube SR1 and the second synchronous rectification switch tube SR2 are turned on at the same time to short-circuit the secondary winding Ls of the transformer, as shown in FIG. Figure 8 In the first time td from time t0 to time t1 in the figure, the first switch tube S1 and the fourth switch tube S4 are turned on to store energy in the inductor Lk. Similarly, when the second switch tube S2 and the third switch tube S3 are turned on, the body diode of the first synchronous rectification switch tube SR1 is turned on synchronously, or the first synchronous rectification switch tube SR1 is turned on synchronously. If the second synchronous rectification switch tube SR2 is also turned on at this time, the body diodes of the second synchronous rectification switch tube SR2 and the first synchronous rectification switch tube SR1 are turned on at the same time to short-circuit the secondary winding Ls of the transformer, as shown in FIG. Figure 8During the first time td from time t2 to time t3, the second switch tube S2 and the third switch tube S3 are turned on to store energy in the inductor Lk.

[0089] In normal operation, when the first switch tube S1 and the fourth switch tube S4 are turned off, the second synchronous rectifier switch tube SR2 is also turned off, but the switch control signal output by the controller of the present application causes the second synchronous rectifier switch tube SR2 to delay turning off until it overlaps with the second switch tube S2 and the third switch tube S3 and turns on for the first time td between time t2 and time t3. Similarly, in normal operation, when the second switch tube S2 and the third switch tube S3 are turned off, the first synchronous rectifier switch tube SR1 is also turned off, but the switch control signal output by the controller of the present application causes the first synchronous rectifier switch tube SR1 to delay turning off until it overlaps with the first switch tube S1 and the fourth switch tube S4 and turns on for the first time td between time t0 and time t1. For details, please refer to Figure 8 .

[0090] That is, when the first setting condition is met, the controller 200 increases the duty cycle of the switch control signal controlling the switch tube in the secondary switch unit 120 until the switch in the primary switch unit 110 overlaps with the switch on for the first time td.

[0091] For specific implementation, please refer to Fig. 9 shown Figure 7 The hard-switching isolated DC / DC converter in FIG. 1 is a schematic diagram of the structure of the hard-switching isolated DC / DC converter working in the first mode. Figure 8 Between the time to and the time t11 in the figure, the first switch tube S1 and the fourth switch tube S4 are turned on synchronously with the second synchronous rectifier switch tube SR2 to realize the conversion from the primary side to the secondary side until the time t11. At the time t11, the first switch tube S1 and the fourth switch tube S4 are turned off, but the second synchronous rectifier switch tube SR2 continues to be turned on. After a dead time, please refer to Fig.10 shown Figure 7 The hard switch isolated DC / DC converter in FIG. 1 is a structural diagram of the hard switch isolated DC / DC converter working in the second mode. At time t2, the second switch tube S2 and the third switch tube S3 are turned on, and the body diode of the first synchronous rectifier switch tube SR1 is turned on synchronously, or the first synchronous rectifier switch tube SR1 is controlled to be turned on synchronously. Since the second synchronous rectifier switch tube SR2 is still turned on at this time, the second synchronous rectifier switch tube SR2 and the first synchronous rectifier switch tube SR1 are turned on at the same time to short-circuit the secondary winding Ls until time t3. Please refer to Fig.11 shown Figure 7The structural diagram of the hard-switched isolated DC / DC converter in FIG. 1 is a schematic diagram of the structure of the hard-switched isolated DC / DC converter working in the third mode. When the second synchronous rectifier switch SR2 is turned off at time t3, the second switch S2 and the third switch S3 are turned on at the same time as the first synchronous rectifier switch SR1, realizing the conversion from the primary side to the secondary side until time t12. When the second switch S2 and the third switch S3 are turned off at time t12, the first synchronous rectifier switch SR1 is still turned on. After the dead time, at time t4, the first switch S1 and the fourth switch S4 are turned on, and the body diode of the second synchronous rectifier switch SR2 is turned on, or the second synchronous rectifier switch SR2 is turned on, forming a stage of short-circuiting the secondary winding Ls until time t5. Please refer to FIG. 1 for details. Fig.12 shown Figure 7 The hard switch isolated DC / DC converter in FIG. 1 is a schematic diagram of the structure of the hard switch isolated DC / DC converter working in the fourth mode. Then enter Fig. 9 The first mode shown is cycled in this way to form a change in the boost phase.

[0092] The diode connected in parallel with the first synchronous rectification switch tube SR1 or the diode connected in parallel with the second synchronous rectification switch tube SR2 may be a body diode of the first synchronous rectification switch tube SR1 or the second synchronous rectification switch tube SR2, or an additional parallel diode.

[0093] The controller 200 mentioned above can be implemented as a digital controller, such as DSP, MCU, etc. The control method mentioned above is implemented by programming the controller 200, so the solution of the present application does not need to change the hardware circuit, has low cost and simple operation.

[0094] In the normal working mode, the controller 200 calculates the duty cycle of the switch control signal according to the input voltage, the desired output voltage and the transformer turns ratio, and outputs the switch control signal according to the calculated duty cycle of the switch control signal. That is, the switch control signal of the hard-switched isolated DC / DC converter 100 is controlled by the closed-loop control loop output. Specifically, the first switch tube S1 and the second switch tube S2 work synchronously with the second synchronous rectifier switch tube SR2, the third switch tube S3 and the fourth switch tube S4 work synchronously with the first synchronous rectifier switch tube SR1, and the first switch tube S1 and the second switch tube S2 work alternately with the third switch tube S3 and the fourth switch tube S4, and there is a dead zone in between. That is, the above-mentioned first time td does not exist.

[0095] The present application also proposes an electric vehicle, which adopts the hard switch isolation DC / DC converter described above, and its advantages are the same as those described above, which will not be repeated here.

[0096] Although the embodiments of the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims.

[0097] In addition, the processes, machines, manufactures, material compositions, devices, methods, and steps described in the specification of the present application are only specific embodiments. As those of ordinary skill in the art will readily appreciate from the disclosure of the present disclosure, processes, machines, manufactures, material compositions, means, methods, or steps that perform substantially the same functions currently exist or will be developed in the future or achieve substantially the same results as the corresponding embodiments described herein that can be used according to the present disclosure. Therefore, the appended claims are intended to include such processes, machines, manufactures, material compositions, devices, methods, or steps within their scope.

Claims

1. A hard-switch isolated DC / DC converter, characterized in that: include: Hard-switching isolated DC / DC converters, including: A transformer, including a primary winding and a secondary winding; A primary switch unit, one end of which is connected to the primary winding of the transformer via an inductor, and the other end of which is used to receive an input voltage; A secondary switch unit, one end of which is connected to the secondary winding of the transformer, and the other end of which is used to output an output voltage; A controller is used to output a switch control signal for controlling the switch tubes in the primary switch unit and the secondary switch unit, wherein the duty cycle of the switch control signal is adjustable, wherein when a first setting condition is met, the switch control signal output by the controller causes the switch tube in the secondary switch unit to overlap with the switch tube in the primary switch unit for a first conduction time, and the secondary winding is short-circuited during the first time, wherein The first setting condition is: the input voltage is less than the input voltage setting value, the maximum output voltage provided by the hard switch isolated DC / DC converter is less than the rated output voltage value, or the input voltage is less than the input voltage setting value, and the output voltage is less than the rated output voltage value; The length of the first time decreases as the input voltage increases.

2. The hard switch isolated DC / DC converter according to claim 1, characterized in that: When the first set condition is met, the switch control signal output by the controller causes the switch tube in the secondary switch unit to delay turning off until the switch tube in the secondary switch unit overlaps with the switch in the primary switch unit for a first time.

3. The hard switch isolated DC / DC converter according to claim 1, characterized in that: The controller executes: S1: receiving the input voltage; S2: Determine whether the input voltage is less than the input voltage setting value, if so, proceed to step S3, if not, proceed to step S7; S3: Calculate the maximum output voltage Vomax1 provided by the hard-switch isolated DC / DC converter according to the input voltage, the turns ratio n of the transformer and the maximum duty cycle Dmax of the switch tube in the primary switch unit; S4: Determine whether Vomax1 is less than the rated output voltage value Vod, if so, proceed to step S5, if not, proceed to step S7, wherein step S7 is the controller controlling the hard switch isolated DC / DC converter to operate in a normal working mode; S5: Obtaining the first time by looking up a table according to the input voltage; S6: Delay turning off the switch tube in the secondary switch unit until the switch tube in the secondary switch unit overlaps with the switch in the primary switch unit for a first turn-on time.

4. The hard switch isolated DC / DC converter according to claim 1, characterized in that: The controller executes: S1: receiving the input voltage and the output voltage; S2: Determine whether the input voltage is less than the input voltage setting value, if so, proceed to step S3, if not, proceed to step S6; S3: Determine whether the output voltage is less than the rated output voltage value Vod, if so, proceed to step S4, if not, proceed to step S6, wherein step S6 is the controller controlling the hard switch isolated DC / DC converter to operate in a normal working mode; S4: Obtaining the first time by looking up a table according to the input voltage; S5: Delay turning off the switch tube in the secondary switch unit until the switch tube in the secondary switch unit overlaps with the switch in the primary switch unit for a first turn-on time.

5. The hard switch isolated DC / DC converter according to claim 3 or 4, characterized in that: The table is a table of the relationship between the input voltage and the first time.

6. The hard switch isolated DC / DC converter according to claim 1, characterized in that: The inductor is used to store energy during the first time.

7. The hard-switch isolated DC / DC converter according to claim 1, characterized in that: The primary switch unit includes a first switch bridge arm and a second switch bridge arm, the first switch bridge arm includes a first switch tube and a second switch tube connected in series, the second switch bridge arm includes a third switch tube and a fourth switch tube connected in series, and the first switch bridge arm is connected in parallel with the second switch bridge arm to form a terminal for receiving an input voltage; The transformer is a secondary winding with a center tap transformer; The secondary switch unit includes a first synchronous rectifier switch tube and a second synchronous rectifier switch tube, the first synchronous rectifier switch tube and the second synchronous rectifier switch tube are respectively connected between the first end and the second end of the secondary winding and the ground end, and the center tap of the secondary winding and the ground end form a terminal for outputting an output voltage; When the first set condition is met, the switch control signal output by the controller causes the first synchronous rectification switch tube to overlap with the first switch tube and the fourth switch tube for the first time, and the second synchronous rectification switch tube to overlap with the second switch tube and the third switch tube for the first time.

8. The hard switch isolated DC / DC converter according to claim 7, characterized in that: When the first set condition is met, the switch control signal output by the controller causes the first synchronous rectifier switch tube to delay shutdown until it overlaps with the first switch tube and the fourth switch tube for the first time, and the second synchronous rectifier switch tube to delay shutdown until it overlaps with the second switch tube and the third switch tube for the first time.

9. The hard switch isolated DC / DC converter according to claim 3 or 4, characterized in that: In the normal operating mode, the controller calculates the duty cycle of the switch control signal according to the input voltage, the desired output voltage and the transformer turns ratio, and outputs the switch control signal according to the calculated duty cycle of the switch control signal.

10. An electric vehicle, characterized in that: A hard-switch isolated DC / DC converter device according to claim 1 is used.

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