Isolation DC / DC conversion circuit and driving method of full-bridge switch unit

Abstract

The invention provides an isolated DC / DC conversion circuit and a driving method of a full-bridge switch unit, and relates to the field of power supplies, a controller is used for outputting switch control signals for controlling a first switch tube to a fourth switch tube in the full-bridge switch unit, the duty ratio of the switch control signal of the first switch tube is alternated by D1 and D2 within a period of time, and the duty ratio of the switch control signal of the second switch tube is alternated by D2; the duty ratio of the switching control signal of the fourth switching tube is alternated by D2 and D1, and the phase difference between the fourth switching tube and the switching control signal of the first switching tube is 180 degrees; a switch control signal of the second switch tube is complementary to a switch control signal of the first switch tube, and a switch control signal of the third switch tube is complementary to a switch control signal of the fourth switch tube. Therefore, the first to fourth switch tubes can be uniform in heat and have the same junction temperature, the working environment temperature of the isolated DC / DC converter can be improved, and the reliability and efficiency of the isolated DC / DC converter can be improved.

Description

Technical Field

[0001] The present application relates to the field of power supply, and in particular to a driving method of an isolated DC / DC conversion circuit and a full-bridge switch unit. Background Art

[0002] Isolated DC-DC converters are used in many situations because they can achieve isolation between the input and output ends and can use the high turns ratio of the transformer to achieve a large transformation ratio between the output voltage and the input voltage.

[0003] Especially when the isolated DC-DC converter is implemented as a resonant converter, it can achieve soft switching within the full load range, thereby reducing switching losses, improving converter efficiency, reducing volume, and increasing power density, and thus being more widely used.

[0004] We know that for isolated DC / DC converters (such as resonant converters), variable frequency control can be used, that is, controlling the operating frequency of the switching tube in the isolated DC / DC converter; duty cycle control under fixed frequency can also be used.

[0005] With the development of power supply technology, we hope that the converter will have higher efficiency, better stability and wider application range.

[0006] However, existing isolated DC-DC converters have problems of inconsistent heating of switch tubes in the switch unit and inconsistent junction temperature, which limits the operating ambient temperature of the isolated DC-DC converter. Summary of the invention

[0007] The present application provides an isolated DC / DC conversion circuit, comprising: a full-bridge switch unit, comprising a first switch bridge arm formed by connecting a first switch tube and a second switch tube in series, a second switch bridge arm formed by connecting a third switch tube and a fourth switch tube in series, the first switch bridge arm being connected in parallel with the second switch bridge arm; a first winding of a transformer, wherein a first end of the first winding is connected to a common node of the first switch tube and the second switch tube, and a second end of the first winding is connected to a common node of the third switch tube and the fourth switch tube; a controller, for outputting a switch control signal for controlling the first switch tube to the fourth switch tube, wherein within a period of time, the duty cycle of the switch control signal of the first switch tube alternates between D1 and D2, the duty cycle of the switch control signal of the fourth switch tube alternates between D2 and D1, and the phase difference with the switch control signal of the first switch tube is 180°; the switch control signal of the second switch tube is complementary to the switch control signal of the first switch tube, and the switch control signal of the third switch tube is complementary to the switch control signal of the fourth switch tube.

[0008] Furthermore, the duty cycle D2 is equal to 1-D1.

[0009] Furthermore, during a period of time, the duty cycle D1 is greater than 0.5 and less than 1.

[0010] Furthermore, the conduction period of the fourth switch tube is located in the middle of the conduction period of the first switch tube.

[0011] Furthermore, the turn-off period of the third switch tube is located in the middle of the turn-off period of the second switch tube.

[0012] Furthermore, during a first time period within a period of time, the switch control signals of the first switch tube and the third switch tube are at a high level, and the switch control signals of the second switch tube and the fourth switch tube are at a low level; during a second time period within a period of time, the switch control signals of the first switch tube and the fourth switch tube are at a high level, and the switch control signals of the second switch tube and the third switch tube are at a low level; during a third time period within a period of time, the switch control signals of the first switch tube and the third switch tube are at a high level, and the switch control signals of the second switch tube and the fourth switch tube are at a low level; during a fourth time period within a period of time, the switch control signals of the second switch tube and the third switch tube are at a high level, and the switch control signals of the first switch tube and the fourth switch tube are at a low level. level; during a fifth time period within a period of time, the switch control signals of the second switch tube and the fourth switch tube are high level, and the switch control signals of the first switch tube and the third switch tube are low level; during a sixth time period within a period of time, the switch control signals of the first switch tube and the fourth switch tube are high level, and the switch control signals of the second switch tube and the third switch tube are low level; during a seventh time period within a period of time, the switch control signals of the second switch tube and the fourth switch tube are high level, and the switch control signals of the first switch tube and the third switch tube are low level; during an eighth time period within a period of time, the switch control signals of the second switch tube and the third switch tube are high level, and the switch control signals of the first switch tube and the fourth switch tube are low level.

[0013] Furthermore, within the period of time, the sum of the current stresses of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, and the body diodes of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube in two switching cycles are the same, and the switching states are exactly the same.

[0014] Furthermore, the length of the first time period is equal to the length of the third time period, and the length of the fifth time period is equal to the length of the seventh time period.

[0015] Furthermore, within two switching cycles, the current stresses of the first switching tube to the fourth switching tube are consistent.

[0016] Furthermore, it also includes: a first switch unit, including at least one switch tube, connected to the first voltage end and the second winding of the transformer, for realizing power conversion.

[0017] Furthermore, the full-bridge switch unit is also used to connect to a second voltage terminal, and the isolated DC / DC conversion circuit is used to convert the electric energy of the first voltage terminal into the electric energy of the second voltage terminal, or the isolated DC / DC conversion circuit is used to convert the electric energy of the second voltage terminal into the electric energy of the first voltage terminal.

[0018] Furthermore, the first switch unit is a full-bridge topology or a half-bridge topology.

[0019] The present application also proposes a driving method for a full-bridge switch unit, wherein the full-bridge switch unit includes a first switch bridge arm formed by a first switch tube and a second switch tube connected in series, a second switch bridge arm formed by a third switch tube and a fourth switch tube connected in series, the first switch bridge arm and the second switch bridge arm are connected in parallel, a common node of the first switch tube and the second switch tube is used to connect a first end of a first winding of a transformer, and a common node of the third switch tube and the fourth switch tube is used to connect a second end of the first winding, comprising: during a first time period within a period of time, driving the first switch tube and the third switch tube to be in a conducting state, and driving the second switch tube and the fourth switch tube to be in an off state; during a second time period within a period of time, driving the first switch tube and the fourth switch tube to be in a conducting state, and driving the second switch tube and the third switch tube to be in an off state; during a third time period within a period of time, driving the first switch tube and the third switch tube to be in a conducting state, The second switch tube and the fourth switch tube are driven to be in the off state; during a fourth time period within a period of time, the second switch tube and the third switch tube are driven to be in the on state, and the first switch tube and the fourth switch tube are driven to be in the off state; during a fifth time period within a period of time, the second switch tube and the fourth switch tube are driven to be in the on state, and the first switch tube and the third switch tube are driven to be in the off state; during a sixth time period within a period of time, the first switch tube and the fourth switch tube are driven to be in the on state, and the second switch tube and the third switch tube are driven to be in the off state; during a seventh time period within a period of time, the second switch tube and the fourth switch tube are driven to be in the on state, and the first switch tube and the third switch tube are driven to be in the off state; during an eighth time period within a period of time, the second switch tube and the third switch tube are driven to be in the on state, and the first switch tube and the fourth switch tube are driven to be in the off state.

[0020] Furthermore, the length of the first time period is equal to the length of the third time period, and the length of the fifth time period is equal to the length of the seventh time period.

[0021] Furthermore, within two switching cycles, the current stresses of the first switching tube to the fourth switching tube are consistent.

[0022] 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

[0023] 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:

[0024] Figure 1 A typical isolated DC / DC conversion circuit schematic is shown;

[0025] Figure 2 A schematic diagram of an isolated DC / DC conversion circuit according to an embodiment of the present application is shown;

[0026] Figure 3 Shows Figure 2 A schematic diagram of operating waveforms of an isolated DC / DC converter in one embodiment over a period of time;

[0027] Figure 4 Shows Figure 2 A schematic diagram of the isolated DC / DC converter in the embodiment of the present invention when operating in the first state;

[0028] Figure 5 Shows Figure 2 A schematic diagram of the isolated DC / DC converter in the embodiment of the present invention when operating in the second state;

[0029] Figure 6 Shows Figure 2 A schematic diagram of the isolated DC / DC converter in FIG. 1 operating in the third state;

[0030] Figure 7 Shows Figure 2 A schematic diagram of the isolated DC / DC converter in FIG. 1 operating in a fourth state;

[0031] Figure 8 Shows Figure 2 A schematic diagram of the isolated DC / DC converter in FIG. 1 operating in the fifth state;

[0032] Fig. 9 Shows Figure 2 A schematic diagram of the isolated DC / DC converter in FIG. 1 operating in the sixth state;

[0033] Fig.10 Shows Figure 2 A schematic diagram of the isolated DC / DC converter in FIG. 1 operating in the seventh state;

[0034] Fig.11 Shows Figure 2 A schematic diagram of the isolated DC / DC converter in FIG. 1 operating in the eighth state;

[0035] Fig.12 Shows Figure 2 FIG. 1 is a schematic diagram of operating waveforms of an isolated DC / DC converter in one embodiment.

[0036] 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

[0037] 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.

[0038] See also Figure 1 A typical isolated DC / DC conversion circuit schematic diagram is shown. The isolated DC / DC converter includes a first switch unit 110, a transformer T and a full-bridge switch unit 120. The transformer T includes a second winding L2 and a first winding L1; the first switch unit 110 is connected between the first voltage terminal V1 and the second winding L2, and the first voltage terminal V1 is used to receive or output a voltage; the full-bridge switch unit 120 is connected between the first winding L1 and the second voltage terminal V2, and the second voltage terminal V2 is used to output or receive a voltage accordingly.

[0039] like Figure 1 As shown, the full-bridge switch unit 120 includes a first switch bridge arm formed by connecting the first switch tube Q1 and the second switch tube Q2 in series, and a second switch bridge arm formed by connecting the third switch tube Q3 and the fourth switch tube Q4 in series. The first switch bridge arm is connected in parallel with the second switch bridge arm to form a second voltage terminal V2. The first end of the first winding L1 is connected to the common node C of the first switch tube Q1 and the second switch tube Q2, and the second end of the first winding L1 is connected to the common node D of the third switch tube Q3 and the fourth switch tube Q4. The first switch tube Q1 and the second switch tube Q2 can be respectively referred to as the upper tube and the lower tube of the first switch bridge arm, the third switch tube Q3 and the fourth switch tube Q4 can be respectively referred to as the upper tube and the lower tube of the second switch bridge arm, the first switch tube Q1 and the fourth switch tube Q4 are referred to as a pair of tubes, and the second switch tube Q2 and the third switch tube Q3 are referred to as a pair of tubes.

[0040] like Figure 1 As shown, the first switch unit 110 includes at least one switch tube for realizing power conversion. In practical applications, it can be implemented as any applicable switch unit, such as a full-bridge switch unit, a half-bridge switch unit, etc. And in practical applications, the isolated DC / DC converter can work in a unidirectional power flow mode, such as for realizing the conversion of the electric energy of the first voltage terminal V1 into the electric energy of the second voltage terminal V2, then the full-bridge switch unit 120 is the secondary switch unit. The isolated DC / DC converter can work in a reverse power flow mode, such as for realizing the conversion of the electric energy of the second voltage terminal V2 into the electric energy of the first voltage terminal V1, then the full-bridge switch unit 120 is the primary switch unit. The isolated DC / DC converter can also work in a bidirectional power flow mode.

[0041] like Figure 1 As shown, the isolated DC / DC converter may further include a resonant cavity 140, and the resonant cavity 140 is connected between the first switch unit 110 and the second winding L2. However, the present application does not limit this, and it may also be connected between the full-bridge switch unit 120 and the first winding L1. As long as the isolated DC / DC converter can be implemented as a resonant converter to achieve soft switching. Figure 1 As shown, the resonant cavity 140 includes a resonant inductor Lr and a resonant capacitor Cr connected in series, but the specific structure of the resonant cavity 140 is not limited in the present application.

[0042] The isolated DC / DC converter further includes a controller 200 for outputting switch control signals for controlling the switch tubes in the first switch unit 110 and the full-bridge switch unit 120 , so that the isolated DC / DC converter realizes power conversion.

[0043] For the full-bridge switch unit 120, there are two existing control modes, namely, phase-shift control mode and asymmetric wave control mode. Specifically, for the phase-shift control mode, the upper and lower tubes of the two bridge arms are driven to maintain a 50% duty cycle, and the two bridge arms are phase-shifted to achieve a three-level conversion of the voltage between the common node C and the common node D of the two bridge arms. However, the phase-shift control mode has an advanced bridge arm and a lagging bridge arm, which will cause the current stress and switch state of the switch tubes on the two bridge arms to be different, and the thermal unevenness of the switch tubes in the full-bridge switch unit 120, in which the junction temperature of two of the switch tubes will be very high, that is, the junction temperature is different. For the asymmetric wave control mode, the phase difference of 180° is maintained between the bridge arms, and the voltage three-level conversion between the common node C and the common node D of the two bridge arms is achieved by using unequal duty cycles of the tubes. In this way, the upper and lower tubes of the two bridge arms are divided into narrow wave tubes and wide wave tubes. The current stress and switch state of the narrow wave tube and the wide wave tube are different, which will also cause thermal unevenness of the upper and lower tubes, and the junction temperature of two of the switch tubes will be very high, that is, the junction temperature is different. This not only affects the reliability and efficiency of the isolated DC / DC converter, but also limits the operating ambient temperature of the isolated DC / DC converter.

[0044] Based on this, an embodiment of the present application is to propose an isolated DC / DC conversion circuit, which can be referred to Figure 2 , which includes the above-mentioned full-bridge switch unit 120 and the first winding L1 of the transformer, and the connection relationship between them is the same as Figure 1 The controller is used to output the switch control signal for controlling the first switch tube Q1 to the fourth switch tube Q4. Specifically, within a period of time, the duty cycle of the switch control signal of the first switch tube Q1 alternates between D1 and D2, and the duty cycle of the switch control signal of the fourth switch tube Q4 alternates between D2 and D1, and the phase difference with the switch control signal of the first switch tube Q1 is 180°, wherein D1 is greater than D2; the switch control signal of the second switch tube Q2 is complementary to the switch control signal of the first switch tube Q1, and the switch control signal of the third switch tube Q3 is complementary to the switch control signal of the fourth switch tube Q4.

[0045] See also Figure 3 shown Figure 2 A schematic diagram of the working waveform of the isolated DC / DC converter in one embodiment over a period of time, and please refer to FIG. Figure 2 .like Figure 3 As shown, VCD is the voltage between the common node C and the common node D, DrQ1 to DrQ4 are driving signals of the first switch tube Q1 to the fourth switch tube Q4, IQ1 to IQ4 are currents flowing through the first switch tube Q1 to the fourth switch tube Q4, IDQ1 to IDQ4 are currents flowing through the body diodes of the first switch tube Q1 to the fourth switch tube Q4, and T is the switching period.

[0046] like Figure 3As shown, in one embodiment, the duty cycle D2 is equal to 1-D1.

[0047] In actual implementation, the duty cycle is calculated according to the closed-loop control. In one embodiment, within a period of time, the duty cycle D1 is greater than 0.5 and less than 1, and D2 is greater than 0 and less than 0.5. At this time, the first switch tube Q1 is alternately driven by a large wave drive signal and a small wave drive signal, and the fourth switch tube Q4 is alternately driven by a small wave drive signal and a large wave drive signal, and the switch control signals of the second switch tube Q2 and the third switch tube Q3 are respectively obtained by complementing the switch control signal of the first switch tube Q1 and the switch control signal of the fourth switch tube Q4.

[0048] In one embodiment, the on period of the fourth switch tube Q4 is located in the middle of the on period of the first switch tube Q1, and the off period of the third switch tube Q3 is located in the middle of the off period of the second switch tube Q2, so as to improve the consistency of the junction temperature of the four switch tubes.

[0049] For details, please refer to Figure 3 In the first time period td1 (from time t1 to time t2) within a period of time, the switch control signals of the first switch tube Q1 and the third switch tube Q3 are high level, and the switch control signals of the second switch tube Q2 and the fourth switch tube Q4 are low level, then the first switch tube Q1 and the third switch tube Q3 are turned on, and the second switch tube Q2 and the fourth switch tube Q4 are turned off. Figure 4 The schematic diagram of the isolated DC / DC converter shown in FIG. 1 is when operating in the first state. The current flows from the first winding L1, the body diode of the first switch tube Q1, the third switch tube Q3, and then back to the first winding L1, short-circuiting the common node C and the common node D. Then, the VCD voltage is zero, and the current flowing through the body diode of the first switch tube Q1 and the third switch tube Q3 are equal, gradually increasing from zero, and the current flowing through the second switch tube Q2 and the fourth switch tube Q4 and their body diodes is zero.

[0050] To continue, see Figure 3 In the second time period td2 (from time t2 to time t3) within a period of time, the switch control signals of the first switch tube Q1 and the fourth switch tube Q4 are at a high level, and the switch control signals of the second switch tube Q2 and the third switch tube Q3 are at a low level, then the first switch tube Q1 and the fourth switch tube Q4 are turned on, and the second switch tube Q2 and the third switch tube Q3 are turned off. Figure 5The schematic diagram of the isolated DC / DC converter shown in FIG. 1 is when the current flows from the first winding L1, the body diode of the first switch tube Q1, the body diode of the fourth switch tube Q4, and then back to the first winding L1. The VCD voltage is positive, and the current flowing through the body diode of the first switch tube Q1 and the body diode of the fourth switch tube Q4 are equal, which is the current gradually decreasing from the current at the end of the first time period td1 to zero. The current flowing through the second switch tube Q2 and the third switch tube Q3 and their body diodes is zero.

[0051] To continue, see Figure 3 In the third time period td3 (from time t3 to time t4) within a period of time, the switch control signals of the first switch tube Q1 and the third switch tube Q3 are at a high level, and the switch control signals of the second switch tube Q2 and the fourth switch tube Q4 are at a low level, then the first switch tube Q1 and the third switch tube Q3 are turned on, and the second switch tube Q2 and the fourth switch tube Q4 are turned off. Figure 6 The schematic diagram of the isolated DC / DC converter shown in FIG. 1 is when the isolated DC / DC converter operates in the third state. The current flows from the first winding L1, the body diode of the third switch tube Q3, the first switch tube Q1, and then back to the first winding L1, short-circuiting the common node C and the common node D. Then, the VCD voltage is zero, and the current flowing through the body diode of the third switch tube Q3 is equal to that of the first switch tube Q1, gradually increasing from zero. The current flowing through the second switch tube Q2 and the fourth switch tube Q4 and their body diodes is zero.

[0052] To continue, see Figure 3 In a fourth time period td4 (from time t4 to time t5) within a period of time, the switch control signals of the second switch tube Q2 and the third switch tube Q3 are at a high level, and the switch control signals of the first switch tube Q1 and the fourth switch tube Q4 are at a low level, then the second switch tube Q2 and the third switch tube Q3 are turned on, and the first switch tube Q1 and the fourth switch tube Q4 are turned off. Figure 7 The schematic diagram of the isolated DC / DC converter shown in FIG. 1 is when operating in the fourth state. The current flows from the first winding L1, the body diode of the third switch tube Q3, the body diode of the second switch tube Q2, and then returns to the first winding L1. The VCD voltage is negative. The current flowing through the body diode of the third switch tube Q3 and the body diode of the second switch tube Q2 are equal. The current gradually decreases from the current at the end of the third time period td3 to zero. The current flowing through the first switch tube Q1 and the fourth switch tube Q4 and their body diodes is zero.

[0053] To continue, see Figure 3In the fifth time period td5 (from time t5 to time t6) within a period of time, the switch control signals of the second switch tube Q2 and the fourth switch tube Q4 are at a high level, and the switch control signals of the first switch tube Q1 and the third switch tube Q3 are at a low level, then the second switch tube Q2 and the fourth switch tube Q4 are turned on, and the first switch tube Q1 and the third switch tube Q3 are turned off. Figure 8 The schematic diagram of the isolated DC / DC converter shown in FIG. 1 is when operating in the fifth state. The current flows from the first winding L1, the second switch tube Q2, the body diode of the fourth switch tube Q4, and then returns to the first winding L1, short-circuiting the common node C and the common node D. Then, the VCD voltage is zero, and the currents flowing through the body diodes of the second switch tube Q2 and the fourth switch tube Q4 are equal and gradually increase from zero. The currents flowing through the first switch tube Q1 and the third switch tube Q3 and their body diodes are zero.

[0054] To continue, see Figure 3 In the sixth time period td6 (from time t6 to time t7) within a period of time, the switch control signals of the first switch tube Q1 and the fourth switch tube Q4 are at a high level, and the switch control signals of the second switch tube Q2 and the third switch tube Q3 are at a low level, then the first switch tube Q1 and the fourth switch tube Q4 are turned on, and the second switch tube Q2 and the third switch tube Q3 are turned off. Fig. 9 The isolated DC / DC converter shown is a schematic diagram of operating in the sixth state. The current flows from the first winding L1, the body diode of the first switch tube Q1, the body diode of the fourth switch tube Q4, and then returns to the first winding L1. The VCD voltage is positive. The current flowing through the body diode of the first switch tube Q1 and the body diode of the fourth switch tube Q4 are equal. The current gradually decreases to zero from the current at the end of the fifth time period td5. The current flowing through the second switch tube Q2 and the third switch tube Q3 and their body diodes is zero.

[0055] To continue, see Figure 3 In the seventh time period td7 (from time t7 to time t8) within a period of time, the switch control signals of the second switch tube Q2 and the fourth switch tube Q4 are at a high level, and the switch control signals of the first switch tube Q1 and the third switch tube Q3 are at a low level, then the second switch tube Q2 and the fourth switch tube Q4 are turned on, and the first switch tube Q1 and the third switch tube Q3 are turned off. Fig.10 The schematic diagram of the isolated DC / DC converter shown in FIG. 1 is when operating in the seventh state. The current flows from the first winding L1, the fourth switch tube Q4, the body diode of the second switch tube Q2, and then returns to the first winding L1, short-circuiting the common node C and the common node D. Then, the VCD voltage is zero, and the current flowing through the body diode of the second switch tube Q2 and the fourth switch tube Q4 are equal, gradually increasing from zero, and the current flowing through the first switch tube Q1 and the third switch tube Q3 and their body diodes is zero.

[0056] To continue, see Figure 3 In the eighth time period td8 (from time t8 to time t9) within a period of time, the switch control signals of the second switch tube Q2 and the third switch tube Q3 are at a high level, and the switch control signals of the first switch tube Q1 and the fourth switch tube Q4 are at a low level, then the second switch tube Q2 and the third switch tube Q3 are turned on, and the first switch tube Q1 and the fourth switch tube Q4 are turned off. Fig.11 The schematic diagram of the isolated DC / DC converter shown in FIG. 1 is when the current flows from the first winding L1, the body diode of the third switch tube Q3, the body diode of the second switch tube Q2, and then back to the first winding L1. The VCD voltage is negative, and the current flowing through the body diode of the second switch tube Q2 and the body diode of the third switch tube Q3 are equal. The current gradually decreases to zero from the end of the seventh time period td7, and the current flowing through the first switch tube Q1 and the fourth switch tube Q4 and their body diodes is zero.

[0057] During at least a period of time, every two switching cycles 2T, the working modes from the first time period td1 to the eighth time period td8 within the above two switching cycles 2T are sequentially repeated.

[0058] In practical applications, the current on the second winding L2 can be coupled to the first winding L1 through the magnetic coupling of the transformer to form a current flowing through the first winding L1, and the current flowing through the first winding L1 can also be formed through the magnetic coupling of the transformer. Figure 1 The current in the second winding L2.

[0059] from Figure 3 It can be seen that the first time period td1 to the eighth time period td8 constitute two switching cycles 2T, that is, the sum of the current stresses of the first switch tube Q1 to the fourth switch tube Q4 and their body diodes is the same within the two switching cycles 2T, and the switch states are exactly the same, so the first switch tube Q1 to the fourth switch tube Q4 can be heated evenly and have the same junction temperature, which can not only improve the operating ambient temperature of the isolated DC / DC converter, but also improve its reliability and efficiency. And within two switching cycles 2T, the first switch tube Q1 to the fourth switch tube Q4 can be heated evenly and have the same junction temperature, so it also has the advantage of fast heating speed. And from the above description, it can be seen that there is no need to exchange the leading arm and the lagging arm like phase shift control, so the present application also has the advantage of simple control.

[0060] In practical applications, the duty cycle of the switch control signal is the ratio of the high level time in a switching cycle to the switching cycle. Figure 3It can be seen that the duty cycle of the switch control signal of the first switch tube Q1 alternates between D1 and D2, and the duty cycle of the switch control signal of the fourth switch tube Q4 of the pair of tubes alternates between D2 and D1, and is 180° out of phase with the switch control signal of the first switch tube Q1. When D1 is greater than 0.5, it works within the above period of time, and is an alternating output of a large wave drive signal and a small wave drive signal. In addition, the switch control signal of the second switch tube Q2 is complementary to the switch control signal of the first switch tube Q1, and the switch control signal of the third switch tube Q3 is complementary to the switch control signal of the fourth switch tube Q4.

[0061] In actual control, please refer to Fig.12 shown Figure 2 The working waveform diagram of the isolated DC / DC converter in one embodiment is as follows: within time tp1, the duty cycle D2 obtained according to the closed-loop control is equal to 0.5, and the duty cycle D1 is also equal to 0.5 at this time, and the length of time when the VCD voltage is zero is zero, that is, the length of time of the first time period td1, the third time period td3, the fifth time period td5 and the seventh time period td7 mentioned above is zero. The driving waveform of the above "a period of time" can be referred to Fig.12 Of course, the present application does not limit the number of cycles within time tp1 and time tp2. Fig.12 For schematic purposes only.

[0062] And if Figure 3 As shown, during the above-mentioned “period of time”, the voltage VCD between the common node C and the common node D is also converted into three levels.

[0063] When the duty cycle D2 and the duty cycle D1 are both equal to 0.5, Fig.12 It can be seen that during this time tp2, the duty ratios of the first switch tube Q1 to the fourth switch tube Q4 are all equal. At this time, the current stress of the first switch tube Q1 to the fourth switch tube Q4 is also consistent, and the junction temperature is consistent. In this way, the current stress of the first switch tube Q1 to the fourth switch tube Q4 is consistent, and the junction temperature is consistent during the entire working process of the isolated DC / DC conversion circuit.

[0064] More specifically, Figure 3 As shown, the length of the first time period td1 is equal to the length of the third time period td3, and the length of the fifth time period td5 is equal to the length of the seventh time period td7.

[0065] Furthermore, the lengths of the second time period td2, the fourth time period td4, the sixth time period td6 and the eighth time period td8 may be made equal.

[0066] The present application also proposes a driving method for a full-bridge switch unit, wherein the full-bridge switch unit can refer to Figure 2 The full-bridge switch unit 120 shown in the figure includes a first switch bridge arm formed by connecting a first switch tube Q1 and a second switch tube Q2 in series, and a second switch bridge arm formed by connecting a third switch tube Q3 and a fourth switch tube Q4 in series. The first switch bridge arm is connected in parallel with the second switch bridge arm. The common node of the first switch tube Q1 and the second switch tube Q2 is used to connect a first end of a first winding L1 of a transformer, and the common node of the third switch tube Q3 and the fourth switch tube Q4 is used to connect a second end of the first winding L1. Figures 3 to 12 And a description thereof, the driving method includes:

[0067] During a first time period td1 within a period of time, the first switch tube Q1 and the third switch tube Q3 are driven to be in an on state, and the second switch tube Q2 and the fourth switch tube Q4 are driven to be in an off state;

[0068] During a second time period td2 within a period of time, the first switch tube Q1 and the fourth switch tube Q4 are driven to be in an on state, and the second switch tube Q2 and the third switch tube Q3 are driven to be in an off state;

[0069] During a third time period td3 within a period of time, the first switch tube Q1 and the third switch tube Q3 are driven to be in an on state, and the second switch tube Q2 and the fourth switch tube Q4 are driven to be in an off state;

[0070] In a fourth time period td4 within a period of time, the second switch tube Q2 and the third switch tube Q3 are driven to be in an on state, and the first switch tube Q1 and the fourth switch tube Q4 are driven to be in an off state;

[0071] In a fifth time period td5 within the period of time, the second switch tube Q2 and the fourth switch tube Q4 are driven to be in the on state, and the first switch tube Q1 and the third switch tube Q3 are driven to be in the off state;

[0072] In a sixth time period td6 within the period of time, the first switch tube Q1 and the fourth switch tube Q4 are driven to be in the on state, and the second switch tube Q2 and the third switch tube Q3 are driven to be in the off state;

[0073] In a seventh time period td7 within a period of time, the second switch tube Q2 and the fourth switch tube Q4 are driven to be in the on state, and the first switch tube Q1 and the third switch tube Q3 are driven to be in the off state;

[0074] In an eighth time period td8 within the period of time, the second switch tube Q2 and the third switch tube Q3 are driven to be in the on state, and the first switch tube Q1 and the fourth switch tube Q4 are driven to be in the off state.

[0075] As can be seen from the above description, the period of time is the time when the sum of the lengths of the first time period td1 to the third time period td3 is greater than the length of the sixth time period td6, that is, the first switch tube Q1 and the fourth switch tube Q4 are alternately driven by a large wave and a small wave. As can be seen from the above description, within two switching cycles 2T, the current stress of the first switch tube Q1 to the fourth switch tube Q4 is consistent.

[0076] As can be seen from the above description, in the process of controlling the full-bridge switch unit, according to the closed-loop control, the duty cycle of the first switch tube Q1 may also be equal to 0.5, then at this time, the duty cycles of the first switch tube Q1 to the fourth switch tube Q4 are all equal to . At this time, the current stress of the first switch tube Q1 to the fourth switch tube Q4 is also consistent.

[0077] Please refer to Figure 3 In one embodiment, the length of the first time period td1 is equal to the length of the third time period td3, and the length of the fifth time period td5 is equal to the length of the seventh time period td7.

[0078] Its principles and advantages are the same as those described in the above-mentioned isolated DC / DC conversion circuit, and will not be repeated here.

[0079] From the above description, we can see that Figure 2 The full-bridge switch unit and the control method thereof can be applied to a primary circuit of an isolated DC / DC conversion circuit, and can also be applied to a secondary circuit of an isolated DC / DC conversion circuit.

[0080] The isolated DC / DC conversion circuit and the driving method of the full-bridge switch unit of the present application can be applied to electric vehicles.

[0081] 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.

[0082] 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. An isolated DC / DC conversion circuit, characterized in that: include: A full-bridge switch unit, comprising a first switch bridge arm formed by connecting a first switch tube and a second switch tube in series, a second switch bridge arm formed by connecting a third switch tube and a fourth switch tube in series, and the first switch bridge arm and the second switch bridge arm are connected in parallel; a first winding of a transformer, wherein a first end of the first winding is connected to a common node of the first switch tube and the second switch tube, and a second end of the first winding is connected to a common node of the third switch tube and the fourth switch tube; A controller is used to output a switch control signal to control the first switch tube to the fourth switch tube, wherein within a period of time The duty cycle of the switch control signal of the first switch tube alternates between D1 and D2, and the duty cycle of the switch control signal of the fourth switch tube alternates between D2 and D1, and is 180° out of phase with the switch control signal of the first switch tube; The switch control signal of the second switch tube is complementary to the switch control signal of the first switch tube, and the switch control signal of the third switch tube is complementary to the switch control signal of the fourth switch tube.

2. The isolated DC / DC conversion circuit according to claim 1, characterized in that: The duty cycle D2 is equal to 1-D1.

3. The isolated DC / DC conversion circuit according to claim 2, characterized in that: During a period of time, the duty cycle D1 is greater than 0.5 and less than 1.

4. The isolated DC / DC conversion circuit according to claim 3, characterized in that: The on-time period of the fourth switch tube is located in the middle of the on-time period of the first switch tube.

5. The isolated DC / DC conversion circuit according to claim 4, characterized in that: The turn-off period of the third switch tube is located in the middle of the turn-off period of the second switch tube.

6. The isolated DC / DC conversion circuit according to any one of claims 1 to 5, characterized in that: During the period of time, the sum of current stresses of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, and the body diodes of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube in two switching cycles are the same, and the switching states are exactly the same.

7. The isolated DC / DC conversion circuit according to claim 1, characterized in that: Also includes: The first switch unit includes at least one switch tube connected to the first voltage end and the second winding of the transformer for realizing power conversion.

8. The isolated DC / DC conversion circuit according to claim 7, characterized in that: The full-bridge switch unit is also used to connect to a second voltage terminal, and the isolated DC / DC conversion circuit is used to convert the electric energy of the first voltage terminal into the electric energy of the second voltage terminal, or the isolated DC / DC conversion circuit is used to convert the electric energy of the second voltage terminal into the electric energy of the first voltage terminal.

9. The isolated DC / DC conversion circuit according to claim 7, characterized in that: The first switch unit is a full-bridge topology or a half-bridge topology.

10. A driving method for a full-bridge switch unit, wherein the full-bridge switch unit comprises a first switch bridge arm formed by connecting a first switch tube and a second switch tube in series, a second switch bridge arm formed by connecting a third switch tube and a fourth switch tube in series, the first switch bridge arm is connected in parallel with the second switch bridge arm, a common node of the first switch tube and the second switch tube is used to connect a first end of a first winding of a transformer, and a common node of the third switch tube and the fourth switch tube is used to connect a second end of the first winding, characterized in that: include: During a first time period within a period of time, driving the first switch tube and the third switch tube to be in an on state, and driving the second switch tube and the fourth switch tube to be in an off state; During a second time period within a period of time, driving the first switch tube and the fourth switch tube to be in an on state, and driving the second switch tube and the third switch tube to be in an off state; During a third time period within a period of time, driving the first switch tube and the third switch tube to be in an on state, and driving the second switch tube and the fourth switch tube to be in an off state; During a fourth time period within a period of time, the second switch tube and the third switch tube are driven to be in an on state, and the first switch tube and the fourth switch tube are driven to be in an off state; During a fifth time period within a period of time, the second switch tube and the fourth switch tube are driven to be in an on state, and the first switch tube and the third switch tube are driven to be in an off state; During a sixth time period within a period of time, the first switch tube and the fourth switch tube are driven to be in an on state, and the second switch tube and the third switch tube are driven to be in an off state; During a seventh time period within a period of time, the second switch tube and the fourth switch tube are driven to be in an on state, and the first switch tube and the third switch tube are driven to be in an off state; During an eighth time period within a period of time, the second switch tube and the third switch tube are driven to be in an on state, and the first switch tube and the fourth switch tube are driven to be in an off state.

11. The driving method of the full-bridge switch unit according to claim 10, characterized in that: The length of the first time period is equal to the length of the third time period, and the length of the fifth time period is equal to the length of the seventh time period.

12. The driving method of the full-bridge switch unit according to claim 10, characterized in that: In two switching cycles, the current stresses of the first switching tube to the fourth switching tube are consistent.

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