Control method for bridge resonant converter and bridge resonant converter

Abstract

Provided in the present application are a control method for a bridge resonant converter and a bridge resonant converter. The method comprises: receiving an input voltage and an output voltage of a bridge resonant converter, and, on the basis of the input voltage and the output voltage, computing the gain of the bridge resonant converter; judging whether the gain is greater than or equal to 1, and when the gain is greater than or equal to 1 or the gain is smaller than 1, using different setting modes to set lengths of a first time Ta and a second time Tb, wherein within the first time Ta, the voltage difference between two terminals of a transformer winding on the output end side of the bridge resonant converter is zero, and the second time Tb is the delay turn-off time of a switch transistor inside a bridge unit on the output end side relative to a switch transistor inside a bridge unit on the input end side that operates synchronously therewith. By only using the two sampling voltages of input voltage and output voltage necessary for controlling bridge resonant converters, the time control with zero voltage difference between two terminals can be achieved without additional sampling circuits, and the control is simple.

Description

Control method of bridge resonant converter and bridge resonant converter Technical Field

[0001] The present application relates to the field of power supply, and in particular to a control method of a bridge resonant converter and a bridge resonant converter. Background Art

[0002] The bridge resonant converter is an extremely attractive isolated DC-DC converter. Since it can achieve soft switching within the full load range, it can reduce switching losses, improve converter efficiency, reduce size, and increase power density, and is therefore widely used in various fields.

[0003] Bridge resonant converters typically employ variable frequency control, controlling the operating frequency of the switches within the bridge resonant converter. This presents a challenge in applications with wide input voltage ranges or output voltage ranges. This is because a wide input voltage range or output voltage range increases the switching frequency range of the bridge resonant converter. Therefore, increasing the switching frequency range that the controller can provide and the switching frequency range that the switches within the bridge resonant converter can withstand requires higher-performance controllers or switching devices, which undoubtedly increases the cost of the bridge resonant converter. Furthermore, a wider switching frequency range can cause devices to operate at their limits, resulting in poorer device performance. For example, this can cause greater interference with other devices, leading to poor converter reliability. This also increases device losses, reducing converter efficiency.

[0004] With the development of technology and market demand for diversified products, bridge resonant converters with a wide input voltage range or a wide output voltage range are needed and expected.

[0005] Therefore, providing a control method for a bridge resonant converter to obtain a high-efficiency and high-reliability bridge resonant converter has become a research focus in the industry.

[0006] Summary of the Invention

[0007] The present application provides a control method for a bridge resonant converter, wherein the bridge resonant converter includes: a first bridge unit, a transformer, a second bridge unit, and a resonant unit, wherein one end of the first bridge unit is connected to the first winding of the transformer, and the other end is used to receive or output a first voltage; one end of the second bridge unit is connected to the second winding of the transformer, and the other end is used to output or receive a second voltage accordingly; the resonant unit is connected between the first bridge unit and the first winding or between the second bridge unit and the second winding, and performs the following steps: S1: receiving an input voltage and an output voltage of the bridge resonant converter, and calculating a gain of the bridge resonant converter based on the input voltage and the output voltage; S2: determining whether the gain is greater than or equal to 1, and setting the lengths of a first time Ta and a second time Tb in different manners when the gain is greater than or equal to 1 and when the gain is less than 1, wherein during the first time Ta, the voltage difference between the two terminals of the transformer winding on the output side of the bridge resonant converter is zero, and the second time Tb is the delayed turn-off time of the switch tube in the bridge unit on the output side relative to the switch tube in the bridge unit on the input side operating synchronously with the output side.

[0008] Furthermore, when the gain in step S2 is greater than or equal to 1 and when the gain is less than 1, different setting methods are used to set the lengths of the first time Ta and the second time Tb, including: S21: determine whether the gain is greater than or equal to 1, if so, enter step S22, if not, enter step S23; S22: configure time parameters A and B according to the first relationship; S23: configure time parameters A and B according to the second relationship; S24: obtain the first time Ta and the second time Tb according to the time parameters A and B.

[0009] Furthermore, in the first relational expression, the time parameter A is related to the gain and the time parameter B, and the time parameter B is a constant; in the second relational expression, the time parameter A is a constant, and the time parameter B is related to the gain.

[0010] Furthermore, step S24 is: receiving the conduction time Ts of the switch tube in the bridge unit as the input end within half a switching cycle, as well as time parameters A and B, and obtaining the first time Ta and the second time Tb respectively according to the relationship Ta=A*Ts and Tb=B*Ts.

[0011] Furthermore, the following steps are performed: S31: receiving an output sampling signal from the bridge resonant converter and a reference signal corresponding to the output sampling signal, and calculating an error signal between the output sampling signal and the reference signal; and S32: obtaining the on-time Ts according to the error signal.

[0012] Furthermore, step S4 is also performed: outputting a switch drive signal for controlling the switch tube in the bridge resonant converter, wherein at the first time Ta, the switch tube in the bridge unit on the side where the output end of the bridge resonant converter is located operates so that the voltage difference between the two terminals of the transformer winding on the side where the output end is located is zero.

[0013] Furthermore, each half switching cycle of the bridge resonant converter includes the first time.

[0014] The present application also provides a bridge resonant converter using the above control method, comprising: the first voltage is an input voltage; the second voltage is an output voltage; the first bridge unit is configured as a half-bridge topology, and the two ends of the first winding are respectively connected to the common node of the two bridge arms in the half-bridge topology;

[0015] The second bridge unit is configured as a full-bridge topology, and the two ends of the second winding are respectively connected to the common node of the two switch bridge arms in the full-bridge topology; a controller executes the above control method.

[0016] Furthermore, within the first time Ta, the switch control signal output by the controller controls the two lower tubes of the full-bridge topology to be turned on at the same time or the two upper tubes to be turned on at the same time.

[0017] The present application also provides a bidirectional bridge resonant converter adopting the above-mentioned control method, including: the first bridge unit is configured as a full-bridge topology, and the two ends of the first winding are respectively connected to the common node of the two switching bridge arms in the first bridge unit; the second bridge unit is configured as a full-bridge topology, and the two ends of the second winding are respectively connected to the common node of the two switching bridge arms in the second bridge unit, and the bidirectional bridge resonant converter is used to convert the first voltage into the second voltage, or convert the second voltage into the first voltage; a controller executes the above-mentioned control method.

[0018] Furthermore, when the bidirectional bridge resonant converter is used to convert the first voltage into the second voltage, within the first time Ta, the switch control signal output by the controller controls the two lower tubes of the second bridge unit to be turned on at the same time or the two upper tubes to be turned on at the same time; when the bidirectional bridge resonant converter is used to convert the second voltage into the first voltage, within the first time Ta, the switch control signal output by the controller controls the two lower tubes of the first bridge unit to be turned on at the same time or the two upper tubes to be turned on at the same time.

[0019] The present application also provides a bridge resonant converter adopting the above-mentioned control method, including: the first voltage is the input voltage; the second voltage is the output voltage; the first bridge unit is configured as a half-bridge topology, and the two ends of the first winding are respectively connected to the common node of the two bridge arms in the half-bridge topology; the second bridge unit is configured as a three-level half-bridge topology, and the three-level half-bridge topology includes: a switch bridge arm formed by a first switch tube, a second switch tube, a third switch tube and a fourth switch tube connected in series; a capacitor bridge arm formed by a third capacitor and a fourth capacitor connected in series, and the capacitor bridge arm is connected in parallel with the switch bridge arm; a flying capacitor, and the flying capacitor is connected between the common node of the first switch tube and the second switch tube and the common node of the third switch tube and the fourth switch tube, wherein the two ends of the second winding are respectively connected to the common node of the second switch tube and the third switch tube and the common node of the capacitor bridge arm; a controller, which executes the above-mentioned control method.

[0020] Furthermore, within the first time Ta, the switch control signal output by the controller controls the second switch tube and the fourth switch tube to be turned on at the same time or the first switch tube and the third switch tube to be turned on at the same time.

[0021] The present application also provides a bidirectional bridge resonant converter adopting the above-mentioned control method, including: the first bridge unit is configured as a full-bridge topology, and the two ends of the first winding are respectively connected to the common node of the two switch bridge arms in the full-bridge topology; the second bridge unit is configured as a three-level half-bridge topology, and the three-level half-bridge topology includes: a switch bridge arm formed by a first switch tube, a second switch tube, a third switch tube and a fourth switch tube connected in series; a capacitor bridge arm formed by a first capacitor and a second capacitor connected in series, and the capacitor bridge arm is connected in parallel with the switch bridge arm; a flying capacitor, and the flying capacitor is connected between the common node of the first switch tube and the second switch tube and the common node of the third switch tube and the fourth switch tube, wherein the two ends of the second winding are respectively connected to the common node of the second switch tube and the third switch tube and the common node of the capacitor bridge arm; a controller, which executes the above-mentioned control method.

[0022] Furthermore, when the bidirectional bridge resonant converter is used to convert the first voltage into the second voltage, within the first time Ta, the switch control signal output by the controller controls the second switch tube and the fourth switch tube to be turned on at the same time or the first switch tube and the third switch tube to be turned on at the same time; when the bidirectional bridge resonant converter is used to convert the second voltage into the first voltage, within the first time Ta, the switch control signal output by the controller controls the two lower tubes of the first bridge unit to be turned on at the same time or the two upper tubes to be turned on at the same time.

[0023] The features and technical advantages of the present disclosure have been summarized quite broadly 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 form the subject matter of the claims of the present disclosure. It will be appreciated by those skilled in the art that the concepts and specific embodiments disclosed herein may be readily used as a basis for modifying or designing other structures or processes for achieving the same purposes 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

[0024] 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:

[0025] FIG1 shows a schematic block diagram of a bridge resonant converter according to an embodiment of the present application;

[0026] FIG2 shows a control flow chart of a bridge resonant converter according to an embodiment of the present application;

[0027] FIG3 shows a schematic diagram of operating waveforms of the output current io and the resonant current ir of the bridge resonant converter in FIG1 according to an embodiment of the present application;

[0028] FIG4 shows a control flow chart of a bridge resonant converter according to an embodiment of the present application;

[0029] FIG5 shows a schematic diagram of a bidirectional bridge resonant converter circuit according to an embodiment of the present application;

[0030] FIG6 shows a schematic diagram of operating waveforms of the bidirectional bridge resonant converter in FIG5 according to an embodiment of the present application;

[0031] FIG7 shows a schematic diagram of a bridge resonant converter circuit according to an embodiment of the present application;

[0032] FIG8 shows a schematic diagram of a bridge resonant converter circuit according to an embodiment of the present application;

[0033] FIG9 shows a schematic diagram of a bidirectional bridge resonant converter circuit according to an embodiment of the present application.

[0034] Corresponding symbols in the different figures generally refer to corresponding parts unless otherwise indicated. These figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale. DETAILED DESCRIPTION

[0035] The following is a clear and complete description of the technical solutions in this application in conjunction with the accompanying drawings. Obviously, the embodiments described 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 making any creative efforts are within the scope of protection of this application.

[0036] Please refer to the block diagram of a bridge resonant converter according to an embodiment of the present application shown in FIG1 . The bridge resonant converter includes: a first bridge unit 110, a transformer 130, a second bridge unit 120, and a resonant unit 140. One end of the first bridge unit 110 is connected to the first winding Lp of the transformer 130, and the other end is used to receive or output a first voltage V1; one end of the second bridge unit 120 is connected to the second winding Ls of the transformer 130, and the other end is used to output or receive a second voltage V2 accordingly; the resonant unit 140 is connected between the first bridge unit 110 and the first winding Lp or between the second bridge unit 120 and the second winding Ls.

[0037] As shown in FIG1 , the resonant unit 140 is configured as an LC series resonant unit formed by connecting a resonant inductor Lr and a resonant capacitor Cr in series. As shown in FIG1 , the LC series resonant unit is connected between the first bridge unit 110 and the first winding Lp. In practical applications, the LC series resonant unit can also be connected between the second bridge unit 120 and the second winding Ls. Of course, the resonant unit 140 can also have other structures, such as an LLC resonant unit, where the resonant capacitor Cr shares the capacitance of the bridge arm of the bridge unit, etc., as long as a resonant cavity is formed between the first bridge unit 110 and the first winding Lp or between the second bridge unit 120 and the second winding Ls.

[0038] The bridge resonant converter shown in Figure 1 typically employs variable frequency control. As we know, variable frequency control uses a sampling-based feedback loop to control the switching frequency of the switches. At the corresponding switching frequency, each switch operates with a duty cycle slightly less than 50%, and the upper and lower switches in the same bridge arm operate alternately with a dead zone in between. At least one switch in the second bridge unit 120 operates synchronously with at least one switch in the first bridge unit 110.

[0039] For the bridge resonant converter shown in Figure 1, when it is configured as a unidirectional bridge resonant converter, used to convert the first voltage V1 into the second voltage V2, we call the first bridge unit 110 the bridge unit on the input side, the first winding Lp is the transformer winding on the input side, and the first voltage V1 can be called the input voltage; the second bridge unit 120 is the bridge unit on the output side, the second winding Ls is the transformer winding on the output side, and the second voltage V2 can be called the output voltage.

[0040] The bridge resonant converter shown in FIG1 , when configured as a bidirectional bridge resonant converter, can be used to convert a first voltage V1 into a second voltage V2, and can also be used to convert the second voltage V2 into the first voltage V1. When operating to convert the first voltage V1 into the second voltage V2, the first bridge unit 110 is referred to as the bridge unit on the input side, the first winding Lp is the transformer winding on the input side, and the first voltage V1 is referred to as the input voltage; the second bridge unit 120 is the bridge unit on the output side, the second winding Ls is the transformer winding on the output side, and the second voltage V2 is referred to as the output voltage. When it works to convert the second voltage V2 into the first voltage V1, we call the second bridge unit 120 the bridge unit on the input side, the second winding Ls is the transformer winding on the input side, and the second voltage V2 can be called the input voltage; the first bridge unit 110 is the bridge unit on the output side, the first winding Lp is the transformer winding on the output side, and the first voltage V1 can be called the output voltage.

[0041] Furthermore, as shown in FIG1 , the bridge resonant converter further includes a controller 200 for controlling the bridge resonant converter. The controller 200 performs the following control method. For details, please refer to the control flow chart of the bridge resonant converter shown in FIG2 . The controller 200 performs the following steps: S1: receiving an input voltage and an output voltage of the bridge resonant converter, and calculating a gain M of the bridge resonant converter according to the input voltage and the output voltage;

[0042] S2: Determine whether the gain M is greater than or equal to 1. When the gain M is greater than or equal to 1 and when the gain is less than 1, different setting methods are used to set the lengths of the first time Ta and the second time Tb. During the first time Ta, the voltage difference between the two terminals of the transformer winding on the side where the output end of the bridge resonant converter is located is zero. The second time Tb is the delayed shutdown time of the switch tube in the bridge unit on the side where the output end is located relative to the switch tube in the bridge unit on the side where the input end is located that works synchronously with it.

[0043] Please refer to FIG3 for a schematic diagram of the operating waveforms of the output current io and resonant current ir of the bridge resonant converter in FIG1 . As shown in FIG3 , during the first time Ta, when the bridge resonant converter is turned on, if the voltage difference between the two terminals of the transformer winding on the side where the output terminal of the bridge resonant converter is located is zero, the output current io of the bridge resonant converter is zero. During this period, the resonant current ir in the resonant unit 140 will gradually increase at a relatively high rate. As shown in FIG3 , energy is stored in the resonant circuit. After the first time Ta, the energy in the resonant circuit can be released, forming a boost stage. This can achieve voltage regulation within a certain range and reduce the switching frequency range. In particular, for bridge resonant converters with a wide input voltage range or a wide output voltage range, the resonant current ir can be increased when the input voltage is relatively low, thereby achieving a gain of the resonant unit greater than one, achieving a boost stage, and reducing the switching frequency range.

[0044] As described above, the present invention controls the bridge resonant converter solely based on the gain M between the output voltage and the input voltage, ensuring that the voltage difference between the two terminals of the transformer winding on the output side is zero. The output voltage Vo and the input voltage Vin are the sampling signals necessary for controlling the bridge resonant converter. This means that the present invention can be implemented using the existing controller of the bridge resonant converter based on the existing output and input voltage sampling signals, without requiring the addition of a new sampling circuit.

[0045] Furthermore, no additional sampling is required, and the adverse effects of sampling delay and sampling error on the control are avoided, making the control more accurate and improving the reliability of the bridge resonant converter.

[0046] Furthermore, to improve the efficiency of the bridge resonant converter, it is desirable to achieve ZCS (zero current switching) in the second bridge unit 120 of the bridge resonant converter. The present application controls the delay in shutting off the switch in the bridge unit on the output side relative to the switch in the bridge unit on the input side, which operates synchronously with it, for a second time Tb. As shown in FIG3 , during this second time Tb, the output current can cross zero and reverse, after which the switch in the bridge unit on the output side is shut off. This allows the switch in the bridge unit on the output side to achieve ZCS, thereby improving the efficiency of the bridge resonant converter.

[0047] In order to make the bridge resonant converter have the above-mentioned first time Ta boost phase, and also make the switch tube in the bridge unit on the side where the output end of the bridge resonant converter is located achieve ZCS, that is, to have the above-mentioned second time Tb. Then the ideal operating waveform of the bridge resonant converter is shown in Figure 3. In order to make the operating waveform of the bridge resonant converter as shown in Figure 3, based on the operating waveform of Figure 3, it is found through research that the first time Ta and the second time Tb are related to the gain of the bridge resonant converter. Specifically, when the gain of the bridge resonant converter is greater than 1 and when it is less than 1, the length setting method of the first time Ta and the second time Tb should be different. That is, it is necessary to implement different setting methods for setting the length of the first time Ta and the second time Tb when the gain is greater than or equal to 1 and when the gain is less than 1.

[0048] More specifically, referring to the control flow chart of the bridge resonant converter shown in FIG4 , as shown in FIG4 , in step S2, when the gain is greater than or equal to 1 and when the gain is less than 1, different setting methods are used to set the lengths of the first time Ta and the second time Tb. More specifically, the process includes: S21: determining whether the gain is greater than or equal to 1; if so, proceeding to step S22; if not, proceeding to step S23; S22: configuring time parameters A and B according to a first relationship; S23: configuring time parameters A and B according to a second relationship; S24: obtaining the first time Ta and the second time Tb based on the time parameters A and B. That is, different setting methods are used to set the time parameters A and B when the gain is greater than or equal to 1 and when the gain is less than 1, and thus, different setting methods are used to set the first time Ta and the second time Tb.

[0049] Specifically, in one embodiment, in the first equation, B = b1 + k1. b1 is a constant, typically ranging from 0.01 to 0.05. This application does not limit the specific value of b1, which depends on the specific circuit of the bridge resonant converter. k1 is a correction factor used to modify the value of B. This correction factor can be adjusted based on the parameters of the components within the bridge resonant converter, or after the bridge resonant converter is designed, it can be modified through multiple experiments to obtain a correction factor suitable for the bridge resonant converter. That is, in the first equation, the time parameter B is a constant.

[0050] Specifically, in one embodiment, in the first relationship, A = (M-1) / M + 2*B + k2, where k2 is a correction factor used to correct the value of A. This correction factor can be adjusted based on the parameters of the components within the bridge resonant converter, or it can be modified after the bridge resonant converter is designed and then corrected based on multiple experiments to obtain a correction factor suitable for the bridge resonant converter. That is, in the first relationship, the time parameter A is related to the gain M and the time parameter B of the bridge resonant converter.

[0051] Specifically, in one embodiment, in the second relationship, B = (1-M) / 2 + k3. Similarly, k3 is a correction factor used to correct the value of B. This correction factor can be adjusted based on the parameters of the components within the bridge resonant converter. Alternatively, after the bridge resonant converter is designed, the correction factor k3 can be modified based on multiple experiments to obtain a suitable correction factor for the bridge resonant converter. That is, in the second relationship, the time parameter B is related to the gain M of the bridge resonant converter.

[0052] Specifically, in one embodiment, in the second equation, A = b2 + k4. b2 is a constant, typically close to zero. Of course, this application does not limit the specific value of b2, which depends on the specific circuit of the bridge resonant converter. k4 is a correction factor used to correct the value of A. This correction factor can be adjusted based on the parameters of the components within the bridge resonant converter, or after the bridge resonant converter is designed, it can be modified through multiple experiments to obtain a correction factor suitable for the bridge resonant converter. That is, in the second equation, the time parameter A is a constant.

[0053] More specifically, as shown in FIG4 , step S24 further receives the on-time Ts of the switch tube in the bridge unit as the input end within a half switching cycle. More specifically, in one embodiment, step S24 includes receiving the on-time Ts of the switch tube in the bridge unit as the input end within a half switching cycle, as well as time parameters A and B, and obtaining the first time Ta and the second time Tb according to the relationship Ta=A*Ts and Tb=B*Ts, respectively.

[0054] More specifically, as shown in FIG4 , the controller 200 further performs the following steps: S31: receiving the output sampling signal Sc from the bridge resonant converter and a reference signal Sref corresponding to the output sampling signal Sc, and calculating an error signal ΔS between the output sampling signal Sc and the reference signal Sref; and S32: obtaining the on-time Ts based on the error signal ΔS. In a specific implementation, step S31 is implemented by the error calculation unit, and step S32 is implemented by the PID operation unit.

[0055] More specifically, the output sampling signal Sc can be any signal representing the output signal of the bridge resonant converter, such as an output voltage signal, an output current signal, or an output power signal. The corresponding reference signal Sref can be a voltage reference signal, a current reference signal, or a power reference signal. Any signal can be used as long as the on-time Ts can be obtained based on the sampling signal Sc and the reference signal Sref.

[0056] Furthermore, the controller 200 also executes step S4: outputting a switch drive signal to control the switch tube in the bridge resonant converter, wherein at the first time Ta, the switch in the bridge unit on the side where the output end of the bridge resonant converter is located works so that the voltage difference between the two terminals of the transformer winding on the side where the output end is located is zero.

[0057] Furthermore, as shown in FIG3 , each half switching cycle of the bridge resonant converter includes the first time Ta.

[0058] The specific working method of the bidirectional bridge resonant converter shown in FIG5 is explained below. Please refer to the circuit diagram of the bidirectional bridge resonant converter using the control method described above in the present application shown in FIG5 .

[0059] As shown in Figure 5, both the first bridge unit 110 and the second bridge unit 120 are configured as a full-bridge topology. The first bridge unit 110 includes a first switching arm formed by a first switching transistor Q1 and a second switching transistor Q2 connected in series, and a second switching arm formed by a third switching transistor Q3 and a fourth switching transistor Q4 connected in series. The first switching arm and the second switching arm are connected in parallel. The two ends of the first winding Lp are respectively connected to the common node of the first switching arm and the second switching arm via a resonant unit 140. In other words, the two ends of the first winding Lp are respectively connected to the common node of the two switching arms in the first bridge unit 110. The second bridge unit 120 includes a third switching arm formed by a fifth switching transistor Q5 and a sixth switching transistor Q6 connected in series, and a fourth switching arm formed by a seventh switching transistor Q7 and an eighth switching transistor Q8 connected in series. The third switching arm and the fourth switching arm are connected in parallel. The two ends of the second winding Ls are respectively connected to the common node of the third switch bridge arm and the fourth switch bridge arm, that is, the two ends of the second winding Ls are respectively connected to the common node of the two switch bridge arms in the second bridge unit 120.

[0060] For the bidirectional bridge resonant converter shown in Figure 5, since the first bridge unit 110 and the second bridge unit 120 are both configured as a full-bridge topology, they can be used to convert the first voltage V1 into the second voltage V2, or convert the second voltage V2 into the first voltage V1, that is, to realize the function of a bidirectional converter.

[0061] In a specific implementation, when the bidirectional bridge resonant converter is used to convert the first voltage V1 to the second voltage V2, during the first time Ta, the controller 200 outputs a switch control signal according to the aforementioned control method, controlling the two lower transistors (the sixth switch Q6 and the eighth switch Q8) or the two upper transistors (the fifth switch Q5 and the seventh switch Q7) of the second bridge unit 120 (the bridge unit on the output side) to be simultaneously turned on. This short-circuits the two terminals of the transformer winding Ls on the output side, resulting in a zero voltage difference between the two terminals.

[0062] When the bidirectional bridge resonant converter is used to convert the second voltage V2 to the first voltage V1, during the first time Ta, the controller 200 outputs a switch control signal according to the aforementioned control method, controlling the two lower transistors (the second switch Q2 and the fourth switch Q4) or the two upper transistors (the first switch Q1 and the third switch Q3) of the first bridge unit 110 to be simultaneously turned on. This short-circuits the two terminals of the transformer winding Lp on the output side, resulting in a zero voltage difference between the two terminals.

[0063] More specifically, in actual operation, the bidirectional bridge resonant converter can also operate in other modes. For details, see FIG6 , which illustrates the operating waveform diagram of the bidirectional bridge resonant converter in FIG5 , and can be combined with FIG3 . It should be noted that controller 200 outputs switching drive signals for controlling the first through eighth switching transistors Q1 through Q8 according to the aforementioned control method. As is known, in variable frequency control, a sampling-based feedback loop controls the switching frequency of the switching transistors, with each switching transistor operating at a duty cycle slightly less than 50% at the corresponding switching frequency.

[0064] For the full-bridge resonant converter shown in FIG5 , the upper and lower transistors in the same bridge arm of the same bridge unit operate in a complementary manner with a dead zone in between. The pairs of transistors in the two bridge arms of the same bridge unit operate in a synchronous manner, with one pair of transistors in the two bridge units operating synchronously. As shown in FIG6 , the first switch Q1 and the fourth switch Q4 in the first bridge unit 110 operate synchronously, while also operating synchronously with the fifth switch Q5 and the eighth switch Q8 in the second bridge unit 120. The third switch Q3 and the second switch Q2 in the first bridge unit 110 operate synchronously, while also operating synchronously with the seventh switch Q7 and the sixth switch Q6 in the second bridge unit 120. The third switch Q3 and the fourth switch Q4 in the first bridge unit 110 operate in a complementary manner with a dead zone in between, while the first switch Q1 and the second switch Q2 operate in a complementary manner with a dead zone in between. The fifth switch Q5 and the sixth switch Q6 in the second bridge unit 120 operate in a complementary manner with a dead zone in between, and the seventh switch Q7 and the eighth switch Q8 operate in a complementary manner with a dead zone in between.

[0065] For the full-bridge resonant converter shown in FIG5 , according to the control method of the present application, during the period when the transistors in the bridge unit on the input side are turned on, before the switches operating synchronously with the switches in the bridge unit on the output side are controlled to be turned on simultaneously, the time during which the two lower switches or the two upper switches in the bridge unit on the output side are turned on is increased. For the full-bridge resonant converter shown in FIG5 , when the second bridge unit 120 is on the output side, the time during which the sixth switch Q6 and the eighth switch Q8 are turned on simultaneously, or the time during which the fifth switch Q5 and the seventh switch Q7 are turned on simultaneously, is increased. When the first bridge unit 110 is on the output side, the time during which the second switch Q2 and the fourth switch Q4 are turned on simultaneously, or the time during which the third switch Q3 and the first switch Q1 are turned on simultaneously, is increased.

[0066] Specifically, referring to FIG6 , during the half switching cycle from time t1 to time t4, the first switch Q1 and the fourth switch Q4 (a pair of switches) in the first bridge unit 110 serving as the input end are turned on. Furthermore, from time t1 to time t3, the sixth switch Q6 is controlled to be turned on (i.e., the on-time of the sixth switch Q6 is extended to time t3). Furthermore, at time t2, the eighth switch Q8 is controlled to be turned on. From time t2 to time t3, the sixth switch Q6 and the eighth switch Q8 (the two lower switches in the second bridge unit 120) are simultaneously turned on, short-circuiting the two terminals of the second winding Ls. The voltage difference between the two terminals is zero, and the output current io of the bridge resonant converter is zero. During this period, the resonant current ir in the resonant unit 140 gradually increases at a relatively high rate, as shown in FIG6 . Energy is stored in the resonant circuit, and the energy in the resonant circuit can be released after the first time Ta, forming a boost stage. This allows voltage regulation within a certain range and reduces the switching frequency range. Furthermore, at time t3, the sixth switch Q6 is controlled to be turned off, the fifth switch Q5 is controlled to be turned on until the end of the half switching cycle at time t4, and the eighth switch Q8 is also controlled to be turned on until the end of the half switching cycle at time t4. Thus, the fifth switch Q5 and the eighth switch Q8 (a pair of switches) in the second bridge unit 120 and the first switch Q1 and the fourth switch Q4 (a pair of switches) in the first bridge unit 110 form synchronously operating switches. Therefore, during the period when the pair of switches (the first switch Q1 and the fourth switch Q4) in the bridge unit on the input side (the first bridge unit 110) is turned on, before the synchronously operating switches (the fifth switch Q5 and the eighth switch Q8) in the bridge unit on the output side (the second bridge unit 120) are controlled to be turned on simultaneously, the time during which the two lower switches (the sixth switch Q6 and the eighth switch Q8) in the bridge unit on the output side (the second bridge unit 120) are simultaneously turned on is increased.

[0067] Furthermore, as shown in FIG6 , at time t4, the first switch Q1 and the fourth switch Q4 in the first bridge unit 110 are controlled to be turned off, while the fifth switch Q5 and the eighth switch Q8 in the second bridge unit 120 operating synchronously therewith remain in the on state until time t5, where time t5 is later than time t4 by the second time Tb. Therefore, from time t4 to time t5, the synchronously operating fifth switch Q5 and the eighth switch Q8 are delayed in turning off by the second time Tb relative to the first switch Q1 and the fourth switch Q4. During this second time Tb, the output current crosses zero and reverses, and the switches in the bridge unit on the output side are then turned off. This allows the switches in the bridge unit on the output side to achieve zero current switching (ZCS), thereby improving the efficiency of the bridge resonant converter. This constitutes the first half of the switching cycle.

[0068] During the second half of the switching cycle, the second and third switches Q2, Q3 within the first bridge unit 110 operate synchronously with the sixth and seventh switches Q6, Q7 within the second bridge unit 120. The eighth switch Q8 is delayed in conduction to coincide with the subsequent conduction of the sixth switch Q6, forming a first time Ta within the second half of the cycle. The synchronously operating sixth and seventh switches Q6, Q7, are turned off a second time Tb later than the second and third switches Q2, Q3. This allows the switches within the bridge units on the output side to achieve zero-current switching (ZCS) operation, thereby improving the efficiency of the bridge resonant converter. This constitutes the first half of the switching cycle. Its operating sequence is similar to that of the first half and will not be further described here.

[0069] Specifically, a dead time may be included between the switching actions of the alternately turned-on switching tubes in the first bridge unit 110, and a dead time may be included between the switching actions of the alternately turned-on switching tubes in the second bridge unit 120 to ensure reliable operation of the bridge resonant converter. Please note that the above description ignores the dead time.

[0070] Figure 6 shows both lower transistors operating simultaneously to achieve zero voltage difference between the two terminals of the transformer winding on the output side. In practical applications, both upper transistors can also operate simultaneously to achieve zero voltage difference between the two terminals of the transformer winding on the output side. Again, using Figure 6 as an example, in the first half of the switching cycle, the seventh switch Q7 can be controlled to remain on until time t3, thereby forming the first time Ta in the second half of the switching cycle with the fifth switch Q5 that subsequently turns on. This constitutes the first half of the switching cycle.

[0071] In the second half of the switching cycle, the fifth switch Q5 is turned on with a delay to form a first time Ta in the second half of the switching cycle with the seventh switch Q7 that is turned on later, thus forming the first half of the switching cycle.

[0072] The above explanation of the principle is made by taking the bidirectional bridge resonant converter operating to convert the first voltage V1 into the second voltage V2 as an example.

[0073] In actual operation, when the bidirectional bridge resonant converter operates to convert the second voltage V2 into the first voltage V1, its control principle is the same as described above and will not be repeated here. The only difference is that the first bridge unit 110 serves as the output side and the second bridge unit 120 serves as the input side.

[0074] The present application also provides a bridge resonant converter, please refer to the circuit diagram of the bridge resonant converter using the control method of the present application shown in Figure 7. The first bridge unit 110 is configured as a half-bridge topology. The primary side bridge unit 110 includes a first switch bridge arm formed by a first switch tube Q1 and a second switch tube Q2 connected in series, and a first capacitor bridge arm formed by a first capacitor C1 and a second capacitor C2 connected in series. The first switch bridge arm is connected in parallel with the first capacitor bridge arm to receive a first voltage V1, and the two ends of the primary side winding Lp are respectively connected to the common node of the first switch tube Q1 and the second switch tube Q2 in the first switch bridge arm and the common node of the first capacitor C1 and the second capacitor C2 in the first capacitor bridge arm.

[0075] Similar to FIG5 , the second bridge unit 120 is configured in a full-bridge topology. The second bridge unit 120 includes a third switch arm formed by a fifth switch tube Q5 and a sixth switch tube Q6 connected in series, and a fourth switch arm formed by a seventh switch tube Q7 and an eighth switch tube Q8 connected in series. The third switch arm and the fourth switch arm are connected in parallel to output a second voltage V2. The two ends of the second winding Ls are respectively connected to the common node of the third switch arm and the fourth switch arm. That is, the two ends of the second winding Ls are respectively connected to the common node of the two switch arms in the second bridge unit 120.

[0076] The bridge resonant converter shown in FIG7 is used to convert a first voltage V1 into a second voltage V2. The first bridge unit 110 is the bridge unit on the input side, and the second bridge unit 120 is the bridge unit on the output side. The first switch Q1 in the first bridge unit 110 operates synchronously with the fifth switch Q5 and the eighth switch Q8 in the second bridge unit 120. The second switch Q2 in the first bridge unit 110 operates synchronously with the seventh switch Q7 and the sixth switch Q6 in the second bridge unit 120. The first switch Q1 and the second switch Q2 in the first bridge unit 110 operate in a complementary manner with a dead zone in between. The fifth switch Q5 and the sixth switch Q6 in the second bridge unit 120 operate in a complementary manner with a dead zone in between. The seventh switch Q7 and the eighth switch Q8 also operate in a complementary manner with a dead zone in between.

[0077] 5 , the same timing is used to increase the time during which the sixth switch tube Q6 and the eighth switch tube Q8 are turned on simultaneously, or the time during which the fifth switch tube Q5 and the seventh switch tube Q7 are turned on simultaneously, and the switch tubes in the second bridge unit 120 working synchronously are delayed in turning off for the second time Tb relative to the switch tubes in the first bridge unit 110, thereby achieving the same function as that of FIG5 when operating for converting the first voltage V1 into the second voltage V2.

[0078] The present application also provides a bridge resonant converter, and the circuit diagram of the bridge resonant converter using the control method of the present application is shown in Figure 8. Similar to Figure 7, the first bridge unit 110 is configured as a half-bridge topology.

[0079] The second bridge unit 120 is configured as a three-level half-bridge topology, including: a switch bridge arm formed by a first switch tube S1, a second switch tube S2, a third switch tube S3 and a fourth switch tube S4 connected in series; a capacitor bridge arm formed by a third capacitor C3 and a fourth capacitor C4 connected in series, the capacitor bridge arm being connected in parallel with the switch bridge arm; a flying capacitor Cf1, the flying capacitor Cf1 being connected between a common node of the first switch tube S1 and the second switch tube S2 and a common node of the third switch tube S3 and the fourth switch tube S4, wherein the two ends of the second winding Ls are respectively connected to the common node of the second switch tube S2 and the third switch tube S3 and the common node of the capacitor bridge arm.

[0080] The bridge resonant converter shown in FIG8 is used to convert a first voltage V1 into a second voltage V2 , wherein the first bridge unit 110 is a bridge unit at the input end, and the second bridge unit 120 is a bridge unit at the output end.

[0081] The first switch Q1 in the first bridge unit 110 operates synchronously with the first and second switches S1 and S2 in the second bridge unit 120. The second switch Q2 in the first bridge unit 110 operates synchronously with the third and fourth switches S3 and S4 in the second bridge unit 120.

[0082] By increasing the first time Ta during which the second switch tube S2 and the fourth switch tube S4 are turned on simultaneously, or the first switch tube S1 and the third switch tube S3 are turned on simultaneously, and delaying the turn-off of the switch tubes in the second bridge unit 120 working synchronously by a second time Tb relative to the switch tubes in the first bridge unit 110, the same function as that of FIG5 for converting the first voltage V1 into the second voltage V2 is achieved.

[0083] The present application also provides a bidirectional bridge resonant converter. Please refer to FIG9 for a circuit diagram of a bidirectional bridge resonant converter using the control method of the present application. Similar to FIG5 , the first bridge unit 110 is configured as a full-bridge topology. Similar to FIG8 , the second bridge unit 120 is configured as a three-level half-bridge topology. It can be used to convert the first voltage V1 into the second voltage V2, or convert the second voltage V2 into the first voltage V1, thereby realizing the function of a bidirectional converter.

[0084] When the bidirectional bridge resonant converter is used to convert the first voltage into the second voltage, the first switch S1 and the second switch S2 in the second bridge unit 120 operate synchronously with the second switch Q2 and the third switch Q3 in the first bridge unit 110. The third switch S3 and the fourth switch S4 in the second bridge unit 120 operate synchronously with the first switch Q1 and the fourth switch Q4 in the first bridge unit 110.

[0085] The first time Ta during which the second switch tube S2 and the fourth switch tube S4 are turned on simultaneously, or the first switch tube S1 and the third switch tube S3 are turned on simultaneously, and the second time Tb during which the switch tube in the second bridge unit 120 working synchronously is turned off later than the switch tube in the first bridge unit 110 is increased.

[0086] When the bidirectional bridge resonant converter is used to convert the second voltage into the first voltage, a first time Ta during which the second switch tube Q2 and the fourth switch tube Q4 are simultaneously turned on, or a first time Ta during which the first switch tube Q1 and the third switch tube Q3 are simultaneously turned on, and a second time Tb during which the switch tube in the second bridge unit 120 working synchronously is delayed in turning off relative to the switch tube in the first bridge unit 110 is increased.

[0087] The controller 200 is a digital controller such as a DSP, MCU, etc. The control method is implemented by programming the controller 200, and the present application does not require the addition of a detection circuit. Therefore, the solution of the present application does not require the modification of the hardware circuit, is low in cost, and is simple to operate.

[0088] In practical applications, when the bridge unit is a full-bridge topology, a capacitor Cb can be added between the transformer and the full-bridge topology, as shown in Figure 9, to avoid the problem of transformer saturation caused by transformer bias magnetization due to circuit parameter errors when the bridge unit of the full-bridge topology works as an excitation source.

[0089] Furthermore, according to the above description, the bridge resonant converter of the present application determines the time when the voltage difference between the transformer winding terminals is zero based on the real-time sampled input voltage, output voltage and output sampling signal, so the control timeliness is good, thereby improving the performance of the bridge resonant converter.

[0090] 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.

[0091] In addition, the processes, machines, manufacture, compositions of matter, devices, methods, and steps described in the specification of this application are merely specific embodiments. As one of ordinary skill in the art will readily appreciate from the disclosure herein, processes, machines, manufacture, compositions of matter, means, methods, or steps that perform substantially the same functions currently exist or will later be developed or that achieve substantially the same results as the corresponding embodiments described herein can be utilized in accordance with the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, devices, methods, or steps.

Claims

1. A control method for a bridge resonant converter, wherein the bridge resonant converter comprises: A first bridge unit, a transformer, a second bridge unit and a resonance unit, wherein one end of the first bridge unit is connected to the first winding of the transformer, and the other end is used to receive or output a first voltage; one end of the second bridge unit is connected to the second winding of the transformer, and the other end is used to output or receive a second voltage accordingly; the resonance unit is connected between the first bridge unit and the first winding or between the second bridge unit and the second winding, characterized in that: S1: receiving an input voltage and an output voltage of the bridge resonant converter, and calculating a gain of the bridge resonant converter according to the input voltage and the output voltage; S2: Determine whether the gain is greater than or equal to 1. When the gain is greater than or equal to 1 and when the gain is less than 1, different setting methods are used to set the length of the first time Ta and the second time Tb. During the first time Ta, the voltage difference between the two terminals of the transformer winding on the side where the output end of the bridge resonant converter is located is zero. The second time Tb is the delayed turn-off time of the switch tube in the bridge unit on the side where the output end is located relative to the switch tube in the bridge unit on the side where the input end working synchronously is located.

2. The control method of the bridge resonant converter according to claim 1, characterized in that: When the gain in step S2 is greater than or equal to 1 and when the gain is less than 1, different setting methods are used to set the lengths of the first time Ta and the second time Tb, including: S21: Determine whether the gain is greater than or equal to 1, if yes, proceed to step S22, if no, proceed to step S23; S22: configuring time parameters A and B according to the first relational expression; S23: configuring time parameters A and B according to the second relational expression; S24: Obtain the first time Ta and the second time Tb according to the time parameters A and B.

3. The control method of the bridge resonant converter according to claim 2, characterized in that: In the first relational expression, the time parameter A is related to the gain and the time parameter B, and the time parameter B is a constant; in the second relational expression, the time parameter A is a constant, and the time parameter B is related to the gain.

4. The control method of the bridge resonant converter according to claim 2 or 3, characterized in that: Step S24 is: receiving the on-time Ts of the switch tube in the bridge unit as the input end within half a switching cycle, and time parameters A and B, and obtaining the first time Ta and the second time Tb respectively according to the relationship Ta=A*Ts and Tb=B*Ts.

5. The control method of the bridge resonant converter according to claim 4, characterized in that: Also execute: S31: receiving an output sampling signal from a bridge resonant converter and a reference signal corresponding to the output sampling signal, and calculating an error signal between the output sampling signal and the reference signal; and S32: Obtain the on-time Ts according to the error signal.

6. The control method of the bridge resonant converter according to claim 1 or 5, characterized in that: Step S4 is also executed: outputting a switch driving signal for controlling the switch tube in the bridge resonant converter, wherein at the first time Ta, the switch tube in the bridge unit on the side where the output end of the bridge resonant converter is located works so that the voltage difference between the two terminals of the transformer winding on the side where the output end is located is zero.

7. The control method of the bridge resonant converter according to claim 1, characterized in that: The first time is included in each half switching cycle of the bridge resonant converter.

8. A bridge resonant converter using the control method of the bridge resonant converter according to claim 1, characterized in that: include: The first voltage is an input voltage; The second voltage is an output voltage; The first bridge unit is configured as a half-bridge topology, and two ends of the first winding are respectively connected to common nodes of two bridge arms in the half-bridge topology; The second bridge unit is configured as a full-bridge topology, and two ends of the second winding are respectively connected to common nodes of two switch bridge arms in the full-bridge topology; A controller, executing the control method according to claim 1.

9. The bridge resonant converter according to claim 8, characterized in that: During the first time Ta, the switch control signal output by the controller controls the two lower tubes of the full-bridge topology to be turned on at the same time or the two upper tubes to be turned on at the same time.

10. A bidirectional bridge resonant converter using the control method of the bridge resonant converter according to claim 1, characterized in that: include: The first bridge unit is configured as a full-bridge topology, and two ends of the first winding are respectively connected to common nodes of two switch bridge arms in the first bridge unit; The second bridge unit is configured as a full-bridge topology, the two ends of the second winding are respectively connected to the common node of the two switch bridge arms in the second bridge unit, and the bidirectional bridge resonant converter is used to convert the first voltage into the second voltage, or convert the second voltage into the first voltage; A controller, executing the control method according to claim 1.

11. The bidirectional bridge resonant converter according to claim 10, characterized in that: When the bidirectional bridge resonant converter is used to convert the first voltage into the second voltage, within the first time Ta, the switch control signal output by the controller controls so that the two lower tubes of the second bridge unit are turned on at the same time or the two upper tubes are turned on at the same time; When the bidirectional bridge resonant converter is used to convert the second voltage into the first voltage, within the first time Ta, the switch control signal output by the controller controls the two lower tubes of the first bridge unit to be turned on at the same time or the two upper tubes to be turned on at the same time.

12. A bridge resonant converter using the control method of the bridge resonant converter according to claim 1, characterized in that: include: The first voltage is an input voltage; The second voltage is an output voltage; The first bridge unit is configured as a half-bridge topology, and two ends of the first winding are respectively connected to common nodes of two bridge arms in the half-bridge topology; The second bridge unit is configured as a three-level half-bridge topology, and the three-level half-bridge topology includes: A switch bridge arm formed by a first switch tube, a second switch tube, a third switch tube and a fourth switch tube connected in series; A capacitance bridge arm formed by a third capacitor and a fourth capacitor connected in series, wherein the capacitance bridge arm is connected in parallel with the switch bridge arm; A flying capacitor is connected between a common node of the first switch tube and the second switch tube and a common node of the third switch tube and the fourth switch tube, wherein Two ends of the second winding are respectively connected to a common node of the second switch tube and the third switch tube and a common node of the capacitor bridge arm; A controller, executing the control method according to claim 1.

13. The bridge resonant converter according to claim 12, characterized in that: During the first time Ta, the switch control signal output by the controller controls the second switch tube and the fourth switch tube to be turned on at the same time or the first switch tube and the third switch tube to be turned on at the same time.

14. A bidirectional bridge resonant converter using the control method of the bridge resonant converter according to claim 1, characterized in that: include: The first bridge unit is configured as a full-bridge topology, and two ends of the first winding are respectively connected to common nodes of two switch bridge arms in the full-bridge topology; The second bridge unit is configured as a three-level half-bridge topology, and the three-level half-bridge topology includes: A switch bridge arm formed by a first switch tube, a second switch tube, a third switch tube and a fourth switch tube connected in series; A capacitance bridge arm formed by a first capacitor and a second capacitor connected in series, the capacitance bridge arm being connected in parallel with the switch bridge arm; A flying capacitor is connected between a common node of the first switch tube and the second switch tube and a common node of the third switch tube and the fourth switch tube, wherein Two ends of the second winding are respectively connected to a common node of the second switch tube and the third switch tube and a common node of the capacitor bridge arm; A controller, executing the control method according to claim 1.

15. The bidirectional bridge resonant converter according to claim 14, characterized in that: When the bidirectional bridge resonant converter is used to convert the first voltage into the second voltage, within the first time Ta, the switch control signal output by the controller controls the second switch tube and the fourth switch tube to be turned on at the same time or the first switch tube and the third switch tube to be turned on at the same time; When the bidirectional bridge resonant converter is used to convert the second voltage into the first voltage, within the first time Ta, the switch control signal output by the controller controls the two lower tubes of the first bridge unit to be turned on at the same time or the two upper tubes to be turned on at the same time.

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