A resonant DC / DC converter, system, control method and controller
By controlling the resonant DC/DC converter to limit the voltage of the resonant capacitor under the closed-circuit state, the problem of random oscillation of the resonant cavity is solved, and the stable operation of the switching transistor and the reduction of losses are achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SUNGROW POWER SUPPLY CO LTD
- Filing Date
- 2026-03-31
- Publication Date
- 2026-06-16
AI Technical Summary
When the switching transistor is turned off, the resonant capacitor may store a lot of energy in the resonant DC/DC converter, causing the resonant cavity to oscillate randomly, which affects the stability of the operation when the switching transistor is turned on next time.
When the resonant current of the resonant cavity is zero under the closed-circuit state by the controller, the voltage on the resonant capacitor is less than the threshold voltage, which limits the voltage on the resonant capacitor, thereby preventing energy from discharging through the anti-parallel diode of the switching transistor, reducing turn-off losses and shortening the oscillation time.
It effectively protects the switching transistor, reduces turn-off losses, shortens oscillation time, ensures that the switching transistor quickly enters a stable working state when it is turned on again, and reduces voltage and current stress.
Smart Images
Figure CN122225855A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of DC-DC conversion technology, specifically to a resonant DC / DC converter, system, control method, and controller. Background Technology
[0002] Resonant DC / DC converters can achieve low-power operation by continuously switching the on / off state of the switching transistors. However, since the turn-off time of the switching transistors is random, the resonant capacitor may store a lot of energy when the switching transistors are turned off, and the resonant current in the resonant cavity may not be zero. This causes the resonant cavity to be in a random oscillation state during the blocking time, which is not conducive to the operation when the switching transistors are turned on again. Summary of the Invention
[0003] In view of this, this application provides a resonant DC / DC converter, system, control method and controller, which facilitates the operation of the switch when it is turned on again by limiting the voltage on the resonant capacitor after the switch is turned off.
[0004] This application provides a resonant DC / DC converter, including: a primary circuit, a resonant cavity, a secondary circuit, and a controller; the first end of the primary circuit is used to connect to a DC source, the second end of the primary circuit is connected to the first end of the resonant cavity, and the second end of the resonant cavity is connected to the secondary circuit; the controller is used to control the converter in a closed-circuit state, such that when the resonant current of the resonant cavity is zero, the voltage on the resonant capacitor of the resonant cavity is less than a threshold voltage.
[0005] One possible implementation is an isolated converter with a resonant capacitor connected to the secondary circuit, which is a half-bridge circuit. In this case, the threshold voltage is half the output voltage of the secondary circuit; or...
[0006] The converter is an isolation converter, with a resonant capacitor connected to the secondary circuit. The secondary circuit is a full-bridge circuit, so the threshold voltage is the output voltage of the secondary circuit; or,
[0007] The converter is an isolated converter, and the resonant capacitor is connected to the primary circuit. The primary circuit is a full-bridge circuit, so the threshold voltage is the voltage of the DC source.
[0008] One possible implementation is a non-isolated converter where both the primary and secondary circuits are full-bridge circuits. In this case, the threshold voltage is the sum of the DC source voltage and the output voltage of the secondary circuit; or...
[0009] When the converter is a non-isolated circuit, with a full-bridge primary circuit and a half-bridge secondary circuit, the threshold voltage is the sum of half the output voltage of the secondary circuit and the voltage of the DC source; or,
[0010] When the converter is a non-isolated circuit, with both the primary and secondary circuits being half-bridge circuits, the threshold voltage is the sum of half the output voltage of the secondary circuit and half the voltage of the DC source.
[0011] In one possible implementation, the controller is also used to control the switching transistor of the converter to turn off when the resonant current of the resonant cavity is zero and the voltage on the resonant capacitor is less than the threshold voltage.
[0012] In one possible implementation, the controller is also used to control the switching transistor of the converter to turn off before the resonant current of the resonant cavity crosses zero. The resonant current freewheels through the anti-parallel diode of the switching transistor of the converter. When the resonant current is zero, the voltage on the resonant capacitor is less than the threshold voltage.
[0013] In one possible implementation, the controller is also used to, during the first switching cycle after the converter's switching transistor is turned off to stop the converter, control the converter to start up again, so that the drive signal of the switching transistor and the drive signal of the switching transistor before the turn-off form a drive signal for a complete switching cycle.
[0014] In one possible implementation, the controller is also used to determine the switching frequency of the converter's switching transistors based on the voltage on the resonant capacitor and the threshold voltage. Based on the switching frequency, the voltage on the resonant capacitor of the resonant cavity is less than the threshold voltage when the converter is in a closed-circuit state and the resonant current of the resonant cavity is zero.
[0015] This application also provides a power conversion system, including the resonant DC / DC converter described above.
[0016] This application also provides a control method for a resonant DC / DC converter, the converter including: a primary circuit, a resonant cavity, and a secondary circuit; the method includes:
[0017] When the control converter is in the closed-circuit state, and the resonant current of the resonant cavity is zero, the voltage on the resonant capacitor of the resonant cavity is less than the threshold voltage.
[0018] One possible implementation is an isolated converter, where the resonant capacitor is connected to the secondary circuit, and the secondary circuit is a half-bridge circuit. In this case, the threshold voltage is half of the output voltage of the secondary circuit; or...
[0019] If the resonant capacitor is connected to the secondary circuit, and the secondary circuit is a full-bridge circuit, then the threshold voltage is the output voltage of the secondary circuit; or,
[0020] If the resonant capacitor is connected to the primary circuit, and the primary circuit is a full-bridge circuit, then the threshold voltage is the voltage of the DC source.
[0021] One possible implementation is a non-isolated converter, where both the primary and secondary circuits are full-bridge circuits, and the threshold voltage is the sum of the DC source voltage and the output voltage of the secondary circuit; or,
[0022] When the primary circuit is a full-bridge circuit and the secondary circuit is a half-bridge circuit, the threshold voltage is the sum of half the output voltage of the secondary circuit and the voltage of the DC source; or,
[0023] When both the primary and secondary circuits are half-bridge circuits, the threshold voltage is the sum of half the output voltage of the secondary circuit and half the voltage of the DC source.
[0024] One possible implementation method further includes: controlling the switching transistor of the converter to turn off when the resonant current of the resonant cavity is zero and the voltage on the resonant capacitor is less than the threshold voltage.
[0025] One possible implementation method further includes: turning off the switch of the control converter before the resonant current of the resonant cavity crosses zero, allowing the resonant current to freewheel through the anti-parallel diode of the switch of the control converter, and when the resonant current is zero, the voltage on the resonant capacitor is less than the threshold voltage of the anti-parallel diode.
[0026] One possible implementation method further includes: during the first switching cycle after the converter is shut down by turning off the switching transistor, the drive signal of the switching transistor and the drive signal of the switching transistor before shutdown form a drive signal for a complete switching cycle.
[0027] This application also provides a controller for performing the methods described above.
[0028] The resonant DC / DC converter provided in this application includes a primary-side circuit, a resonant cavity, a secondary-side circuit, and a controller. The controller controls the resonant DC / DC converter in a closed-circuit state. When the resonant current of the resonant cavity is zero, the voltage across the resonant capacitor of the resonant cavity is less than the threshold voltage, effectively limiting the voltage across the resonant capacitor. This results in very low or no energy on the resonant capacitor, preventing discharge through the anti-parallel diode of the switching transistor. Consequently, it effectively limits the resonant current of the resonant cavity after the switching transistor is turned off, reducing turn-off losses. Furthermore, it shortens the oscillation time when the switching transistor is turned on again, allowing it to quickly enter a stable operating state. This reduces the voltage and current stress on the switching transistor during oscillation, protecting the switching transistor. Attached Figure Description
[0029] Figure 1 A schematic diagram of a resonant DC / DC converter provided in an embodiment of this application;
[0030] Figure 2 A control block diagram of a controller provided in an embodiment of this application;
[0031] Figure 3 A schematic diagram of a first type of isolated resonant DC / DC converter provided in the embodiments of this application;
[0032] Figure 4 A schematic diagram of a second type of isolated resonant DC / DC converter provided in the embodiments of this application;
[0033] Figure 5A A schematic diagram of a third type of isolated resonant DC / DC converter provided in the embodiments of this application;
[0034] Figure 5B A schematic diagram of a fourth type of isolated resonant DC / DC converter provided in the embodiments of this application;
[0035] Figure 6 A schematic diagram of a first type of non-isolated resonant DC / DC converter provided in the embodiments of this application;
[0036] Figure 7 A schematic diagram of a second type of non-isolated resonant DC / DC converter provided in the embodiments of this application;
[0037] Figure 8 A schematic diagram of a third type of non-isolated resonant DC / DC converter provided in the embodiments of this application;
[0038] Figure 9 A schematic diagram illustrating the operation and shutdown of a converter according to an embodiment of this application;
[0039] Figure 10 A schematic diagram of a driving waveform for a switching transistor provided in an embodiment of this application;
[0040] Figure 11 A schematic diagram illustrating the startup process of a converter from shutdown, as provided in an embodiment of this application;
[0041] Figure 12 A flowchart of a converter control method provided in an embodiment of this application;
[0042] Figure 13 This is a schematic diagram of a controller provided in an embodiment of this application. Detailed Implementation
[0043] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.
[0044] The following is combined Figure 1 and Figure 2 This application introduces a resonant DC / DC converter provided in its embodiments. See also... Figure 1This figure is a schematic diagram of a resonant DC / DC converter provided in an embodiment of this application. See also... Figure 2 The figure is a control block diagram of a controller provided in an embodiment of this application.
[0045] Figure 1 The resonant DC / DC converter shown includes: a primary circuit 101, a resonant cavity 102, a secondary circuit 103, and a controller 104.
[0046] In this circuit, the first terminal of the primary-side circuit 101 is connected to a DC source with voltage Vp. The second terminal of the primary-side circuit 101 is connected to the first terminal of the resonant cavity 102, and the second terminal of the resonant cavity 102 is connected to the secondary-side circuit 103. The resonant cavity 102 may include a resonant inductor and a resonant capacitor connected in series. The secondary-side circuit 103 can be connected to a subsequent circuit or a load. Figure 1 Take the connection load as an example.
[0047] The controller 104 is used to control the voltage Vc on the resonant capacitor of the resonant cavity to be less than the threshold voltage Vthr when the resonant current of the resonant cavity is zero in the closed-circuit state of the converter.
[0048] The controller 104 is also used to determine the switching frequency fs of the converter's switching transistor based on the voltage Vc on the resonant capacitor and the threshold voltage Vthr, and to control the voltage on the resonant capacitor of the resonant cavity to be less than the threshold voltage Vthr when the converter is in the closed-circuit state and the resonant current of the resonant cavity is zero, based on the switching frequency fs.
[0049] Figure 2 In the middle, the controller 104 is used to calculate the difference between the preset voltage Vset and the voltage Vc on the resonant capacitor, and input the result of the difference into the proportional-integral (PI) regulator 201. The PI regulator 201 outputs the switching frequency fs of the switching transistor of the converter.
[0050] Time-domain analysis reveals that as the switching frequency fs increases, the single-resonance time shortens, the energy conversion within the resonant cavity decreases, and the absolute value of the voltage Vc across the resonant capacitor shows a monotonically decreasing trend when the resonant current crosses zero. Therefore, from Figure 2As shown in the closed-loop control block diagram, the controller 104 can control the switching frequency fs of the converter based on the voltage Vc on the resonant capacitor and the threshold voltage Vthr. For example, it can make the preset voltage Vset less than the threshold voltage Vthr, thereby controlling the switching frequency fs of the converter to make the voltage Vc on the resonant capacitor less than the threshold voltage Vthr. By limiting the voltage Vc on the resonant capacitor to within the threshold voltage Vthr after the switch is turned off, the resonant capacitor can maintain its own voltage Vc. The resonant capacitor will not discharge through the anti-parallel diode of the switch, effectively limiting the resonant current in the resonant cavity, reducing the stress on the switch, and protecting the switch. The anti-parallel diode can be a parasitic diode of the switch or an external diode. The external diode is generally packaged together with the switch.
[0051] This application does not specifically limit the specific structure of the resonant DC / DC converter or the specific structure of the resonant cavity. The value of the threshold voltage Vthr will differ depending on the converter structure or the resonant cavity structure. Specifically, the converter can include an isolated converter and a non-isolated converter. When the converter is a non-isolated converter, the threshold voltage Vthr is related to the DC source voltage Vp and the output voltage Vs of the secondary circuit 103. When the converter is an isolated converter and the resonant capacitor is connected to the primary circuit 101, the threshold voltage Vthr is related to the DC source voltage Vp. When the converter is an isolation transformer and the resonant capacitor is connected to the secondary circuit 103, the threshold voltage Vthr is related to the output voltage Vs of the secondary circuit 103.
[0052] If the voltage across the resonant capacitor is high after the switch is turned off, the energy in the resonant capacitor will be released, causing oscillation. Furthermore, the number of oscillations is uncertain. This results in an uncertain direction of the resonant current when the switch is turned on again, leading to further oscillation and a slower time to reach stable operation. Therefore, in order to reduce oscillation after the switch is turned off and to quickly reach a stable operating state after the switch is turned on again, this embodiment controls the voltage across the resonant capacitor to be less than a threshold voltage when the switch is blocked.
[0053] The resonant DC / DC converter provided in this application includes a primary-side circuit, a resonant cavity, a secondary-side circuit, and a controller. The controller controls the resonant DC / DC converter in a closed-circuit state. When the resonant current of the resonant cavity is zero, the voltage across the resonant capacitor of the resonant cavity is less than the threshold voltage, effectively limiting the voltage across the resonant capacitor. This results in very low or no energy on the resonant capacitor, preventing discharge through the anti-parallel diode of the switching transistor. Consequently, it effectively limits the resonant current of the resonant cavity after the switching transistor is turned off, reducing turn-off losses. Furthermore, it shortens the oscillation time when the switching transistor is turned on again, allowing it to quickly enter a stable operating state. This reduces the voltage and current stress on the switching transistor during oscillation, protecting the switching transistor.
[0054] The following detailed explanation of the threshold voltage selection principles for converters with different structures, using specific examples, is provided below.
[0055] In one possible implementation, the converter is an isolation converter, the resonant capacitor is connected to the secondary circuit 103, the secondary circuit 103 is a half-bridge circuit, and the threshold voltage Vthr is half of the output voltage Vs of the secondary circuit 103.
[0056] See Figure 3 The figure is a schematic diagram of the first type of isolated resonant DC / DC converter provided in the embodiments of this application.
[0057] Figure 3 In the isolation converter shown, the primary-side circuit 101 is a full-bridge circuit, including a first switch S1 and a second switch S2 connected in series, as well as a third switch S3 and a fourth switch S4 connected in series. The secondary-side circuit 103 is a half-bridge circuit, including a fifth switch S5 and a sixth switch S6 connected in series. The first split capacitor bridge arm SC1 includes a first capacitor C1 and a second capacitor C2 connected in series, and the first split capacitor bridge arm SC1 is connected in parallel at the output terminal of the secondary-side circuit 103.
[0058] The first end of the primary winding of the isolation transformer is connected to the common terminal of the first switch S1 and the second switch S2, and the second end of the primary winding of the isolation transformer is connected to the common terminal of the third switch S3 and the fourth switch S4. The first end of the secondary winding of the isolation transformer is connected to the common terminal of the fifth switch S5 and the sixth switch S6 through the inductor L, and the second end of the secondary winding of the isolation transformer is connected to the common terminal of the first capacitor C1 and the second capacitor C2.
[0059] The resonant inductance of the resonant cavity includes the leakage inductance and inductance L of the isolation transformer, and the resonant capacitance is the equivalent capacitance of the first capacitor C1 and the second capacitor C2 connected in parallel.
[0060] Defining the voltage at the positive output terminal of the secondary circuit 103 as Vs / 2 and the voltage at the negative output terminal of the secondary circuit 103 as -Vs / 2, the absolute value of the voltage Vc across the resonant capacitor can be defined as... This refers to the difference between the voltage across the second capacitor C2 and the output voltage Vs of the half-secondary circuit 103. Those skilled in the art will understand that the absolute value of the voltage Vc across the resonant capacitor can also be defined as | -Vs / 2|, which will not be elaborated here. The voltage across the first capacitor C1, This is the voltage across the second capacitor C2.
[0061] Since the isolation transformer transfers energy through the primary winding and the secondary winding, after the switching tube is turned off, the voltage of the primary circuit 101 of the converter cannot be refracted to the secondary circuit 103. Therefore, when the resonant capacitor is connected to the secondary circuit 103, the structure of the primary circuit 101 will not affect the value of the threshold voltage Vthr. That is, when the primary circuit 101 is a half-bridge circuit, the value of the threshold voltage Vthr is also half of the output voltage Vs of the secondary circuit 103.
[0062] The selection logic of the threshold voltage Vthr will be specifically described below.
[0063] When the switching tube is turned off, taking the fifth switching tube S5 as an example, the voltage at the positive terminal of the anti-parallel diode of the fifth switching tube S5 is the voltage Vc on the resonant capacitor, and the voltage at the negative terminal of the anti-parallel diode of the fifth switching tube S5 is Vs / 2. Therefore, in order to keep the resonant capacitor maintaining its own voltage Vc without discharging through the anti-parallel diode of the fifth switching tube S5, it is necessary to make the voltage at the positive terminal of the anti-parallel diode of the fifth switching tube S5 lower than the voltage at the negative terminal. Since the voltage clamping range provided by the secondary circuit 103 is between +Vs and -Vs, and the voltage on the resonant capacitor may be positive or negative, therefore, when the absolute value of the voltage Vc on the resonant capacitor satisfies < Vs / 2, the resonant capacitor can maintain its own voltage Vc without discharging through the anti-parallel diode of the switching tube. In Figure 3 the converter shown, the threshold voltage Vthr can be selected as Vs / 2.
[0064] The above embodiments introduce the selection principle of the threshold voltage Vthr when the converter is an isolation converter, the resonant capacitor is connected to the secondary circuit 103, and the secondary circuit 103 is a half-bridge circuit. Below, in combination with the accompanying drawings, the selection principle of the threshold voltage Vthr when the secondary circuit 103 is a full-bridge circuit will be introduced.
[0065] In a possible implementation, the converter is an isolation converter, the resonant capacitor is connected to the secondary circuit 103, and the secondary circuit 103 is a full-bridge circuit, then the threshold voltage Vthr is the output voltage Vs of the secondary circuit 103.
[0066] Refer to Figure 4 which is a schematic diagram of the second isolated resonant DC / DC converter provided by the embodiment of the present application.
[0067] Different from Figure 3 is that Figure 4The secondary circuit 103 is a full-bridge circuit, including a fifth switch S5 and a sixth switch S6 connected in series, and a seventh switch S7 and an eighth switch S8 connected in series. The first terminal of the secondary winding of the isolation transformer is connected to the common terminal of the fifth switch S5 and the sixth switch S6 through an inductor L and a capacitor Cd, and the second terminal of the secondary winding of the isolation transformer is connected to the common terminal of the seventh switch S7 and the eighth switch S8. The capacitor Cd is a resonant capacitor.
[0068] Continuing with the example of the fifth switch S5, Figure 4 In the circuit, the voltage across the anode of the anti-parallel diode of the fifth switch S5 is the voltage Vc across the resonant capacitor, and the voltage across the cathode of the anti-parallel diode is the output voltage Vs of the secondary circuit 103. Since the voltage across the resonant capacitor can be either positive or negative, to maintain the resonant capacitor's voltage Vc without discharging through the anti-parallel diode of the fifth switch S5, the voltage across the anode of the anti-parallel diode must be lower than the voltage across the cathode, i.e., |Vc| < Vs. Figure 4 In the converter shown, the threshold voltage Vthr can be selected as Vs. If the voltage across the resonant capacitor is positive and greater than Vs, the voltage across capacitor Cd will discharge through the anti-parallel diodes of the fifth switch S5 and the eighth switch S8. If the voltage across the resonant capacitor is negative and its absolute value is greater than Vs, the voltage across capacitor Cd will discharge through the anti-parallel diodes of the sixth switch S6 and the seventh switch S7.
[0069] above Figure 4 The resonant capacitor described above is connected to the secondary winding of the transformer. Another possible implementation is described below, where the converter is an isolation converter, and the resonant capacitor is connected to the primary circuit. See [link to relevant documentation]. Figure 5A The figure is a schematic diagram of the third type of isolated resonant DC / DC converter provided in the embodiments of this application.
[0070] If the primary-side circuit 101 is a full-bridge circuit, then the threshold voltage Vthr is equal to the DC source voltage Vp. When the converter is an isolated converter and the resonant capacitor is connected to the primary-side circuit 101, the structure of the secondary-side circuit 103 does not affect the value of the threshold voltage Vthr. Figure 4 The difference is that, Figure 5A In the isolated resonant DC / DC converter shown, the first end of the primary winding of the isolation transformer is connected to the common terminal of the first switch S1 and the second switch S2 through a capacitor Cd, and the first end of the secondary winding of the isolation transformer is connected to the common terminal of the fifth switch S5 and the sixth switch S6 through an inductor L.
[0071] The analysis will be conducted using the first switching transistor S1 as an example. Figure 5AIn the converter shown in Figure 5, the voltage across the anode of the anti-parallel diode of the first switching transistor S1 is the voltage Vc across the resonant capacitor, and the voltage across the cathode of the anti-parallel diode is the voltage Vp of the DC source. Since the voltage across the resonant capacitor can be either positive or negative, to maintain the resonant capacitor's voltage Vc and prevent it from discharging through the anti-parallel diode of the first switching transistor S1, the voltage across the anode of the anti-parallel diode must be lower than the voltage across the cathode. Because the voltage clamping range provided by the primary-side circuit 101 is between +Vp and -Vp, we obtain |Vc| < Vp. In the converter shown in Figure 5, the threshold voltage Vthr can be selected as Vp.
[0072] See Figure 5B In another possible implementation, the converter is an isolated converter. The first resonant capacitor Cd1 is connected to the primary circuit 101, and the second resonant capacitor Cd2 is connected to the secondary circuit 103. Both the primary circuit 101 and the secondary circuit 103 are full-bridge circuits. Therefore, the threshold voltage Vthr1 of the first resonant capacitor is the DC source voltage Vp, and the threshold voltage Vthr2 of the second resonant capacitor is the output voltage Vs of the secondary circuit 103. In this embodiment, the selection principles for the threshold voltages of the first and second resonant capacitors are similar to those in the above embodiments and will not be repeated here.
[0073] The above analysis shows that, in the case of an isolated converter, when the resonant capacitor is connected to the secondary circuit and the secondary circuit is a half-bridge circuit, the threshold voltage is half of the output voltage of the secondary circuit; when the resonant capacitor is connected to the secondary circuit and the secondary circuit is a full-bridge circuit, the threshold voltage is the output voltage of the secondary circuit; and when the resonant capacitor is connected to the primary circuit and the primary circuit is a full-bridge circuit, the threshold voltage is the voltage of the DC source. The controller controls the switching frequency of the converter based on the voltage across the resonant capacitor and the threshold voltage. This allows the resonant capacitor to maintain its voltage after the switching transistor is turned off, preventing discharge through the anti-parallel diode of the switching transistor. This limits the resonant current, reduces the stress on the switching transistor, and protects the switching transistor.
[0074] The above embodiments illustrate the selection method of the threshold voltage in an isolated resonant DC / DC converter. The following section provides a detailed explanation of the selection method of the threshold voltage in a non-isolated resonant DC / DC converter.
[0075] In one possible implementation, the converter is a non-isolated circuit. When both the primary-side circuit 101 and the secondary-side circuit 103 are full-bridge circuits, the threshold voltage Vthr is the sum of the DC source voltage Vp and the output voltage Vs of the secondary-side circuit 103.
[0076] See Figure 6, this figure is a schematic diagram of the first non-isolated resonant DC / DC converter provided by an embodiment of the present application.
[0077] Figure 6 Different from Figure 4 is that in the non-isolated converter shown in Figure 6 , the common terminal A of the first switch tube S1 and the second switch tube S2 is connected to the common terminal C of the fifth switch tube S5 and the sixth switch tube S6 through an inductor L and a capacitor Cd, and the common terminal B of the third switch tube S3 and the fourth switch tube S4 is connected to the common terminal D of the seventh switch tube S7 and the eighth switch tube S8. Figure 6 In the resonant cavity 102 of
[0078] In Figure 6 , in the non-isolated converter shown, after the switch tubes are blocked, in the resonant loop jointly composed of the primary circuit 101, the resonant cavity 102 and the secondary circuit 103, the voltage Vp of the DC source, the voltage Vc on the resonant capacitor and the output voltage Vs of the secondary circuit 103 satisfy: Vc = Vp + Vs. Since the voltage clamping range provided by the primary circuit 101 is between +Vp and -Vp, and the voltage clamping range provided by the secondary circuit 103 is between +Vs and -Vs, therefore, in order to make the resonant capacitor maintain its own voltage after the switch tubes are turned off and not discharge through the anti-parallel diodes of the switch tubes, the absolute value of the voltage Vc on the resonant capacitor needs to satisfy <Vp + Vs. In Figure 6 , in the converter shown, the threshold voltage Vthr can be selected as Vp + Vs.
[0079] In a possible implementation, when the converter is a non-isolated circuit, the primary circuit 101 is a full-bridge circuit, and the secondary circuit 103 is a half-bridge circuit, the threshold voltage Vthr is the sum of half of the output voltage Vs of the secondary circuit 103 and the voltage Vp of the DC source.
[0080] Refer to Figure 7 , this figure is a schematic diagram of the second non-isolated resonant DC / DC converter provided by an embodiment of the present application.
[0081] Figure 7 Different from Figure 6 is that in Figure 7In the non-isolated converter shown, the secondary circuit 103 is a half-bridge circuit, including a fifth switch tube S5 and a sixth switch tube S6 connected in series. The first split-capacitor bridge arm SC1 includes a first capacitor C1 and a second capacitor C2 connected in series, and the first split-capacitor bridge arm SC1 is connected in parallel to the output terminal of the secondary circuit 103. The common terminal of the first switch tube S1 and the second switch tube S2 is connected to the common terminal of the fifth switch tube S5 and the sixth switch tube S6 through an inductor L and a capacitor Cd, and the common terminal of the third switch tube S3 and the fourth switch tube S4 is connected to the common terminal of the first capacitor C1 and the second capacitor C2. The resonant capacitor includes the equivalent capacitor after the parallel connection of the first capacitor C1 and the second capacitor C2 and the capacitor Cd.
[0082] As can be seen from Figure 3 the embodiment, the absolute value of the voltage on the equivalent capacitor of the first capacitor C1 and the second capacitor C2 is defined as |U C2 -Vs / 2|. Therefore, Figure 7 in the non-isolated resonant DC / DC converter shown, the absolute value of the voltage Vc on the resonant capacitor is |U Cd +U C2 -Vs / 2|. U Cd is the voltage on the capacitor Cd.
[0083] Taking the midpoint of the output voltage Vs of the secondary circuit 103 as the voltage zero point, in Figure 7 the non-isolated converter shown, after the switch tubes are blocked, in the resonant loop jointly composed of the primary circuit 101, the resonant cavity and the secondary circuit 103, the voltage Vp of the DC source, the voltage Vc on the resonant capacitor and the output voltage Vs of the secondary circuit 103 satisfy: Vc = Vp + Vs / 2.
[0084] Since the voltage clamping range provided by the primary circuit 101 is between +Vp and -Vp, and the voltage clamping range provided by the secondary circuit 103 is between +Vs / 2 and -Vs / 2, therefore, in order to enable the resonant capacitor to maintain its own voltage after the switch tubes are turned off and not discharge through the anti-parallel diodes of the switch tubes, the absolute value of the voltage Vc on the resonant capacitor needs to satisfy <Vp + Vs / 2. In Figure 7 the converter shown, the threshold voltage Vthr can be selected as Vp + Vs / 2.
[0085] In a possible implementation manner, when the converter is a non-isolated circuit and the primary circuit 101 is a half-bridge circuit and the secondary circuit 103 is a half-bridge circuit, the threshold voltage Vthr is the sum of half of the output voltage of the secondary circuit and half of the voltage of the DC source.
[0086] Refer to Figure 8 , this figure is a schematic diagram of the third non-isolated resonant DC / DC converter provided by the embodiment of the present application.
[0087] Figure 8 In the non-isolated converter shown, the primary circuit 101 is a half-bridge circuit, including a first switching transistor S1 and a second switching transistor S2 connected in series; the secondary circuit 103 is a half-bridge circuit, including a fifth switching transistor S5 and a sixth switching transistor S6 connected in series. The first split-capacitor arm SC1 includes a first capacitor C1 and a second capacitor C2 connected in series, and the first split-capacitor arm SC1 is connected in parallel to the input of the primary circuit 101; the second split-capacitor arm SC2 includes a third capacitor C3 and a fourth capacitor C4 connected in series, and the second split-capacitor arm SC2 is connected in parallel to the output of the secondary circuit 103. The common terminal of the first switching transistor S1 and the second switching transistor S2 is connected to the common terminal of the fifth switching transistor S5 and the sixth switching transistor S6 through an inductor L and a capacitor Cd, and the common terminal of the first capacitor C1 and the second capacitor C2 is connected to the common terminal of the third capacitor C3 and the fourth capacitor C4. The resonant capacitor includes the equivalent capacitor of the parallel connection of the capacitor Cd, the first capacitor C1 and the second capacitor C2, and the equivalent capacitor of the parallel connection of the third capacitor C3 and the fourth capacitor C4.
[0088] Similar to the above embodiment, Figure 8 in, the absolute value of the voltage on the equivalent capacitor of the first capacitor C1 and the second capacitor C2 is defined as |U C2 - Vp / 2|, and the absolute value of the voltage on the equivalent capacitor of the third capacitor C3 and the fourth capacitor C4 is defined as |U C4 - Vs / 2|. Therefore, Figure 8 in the non-isolated resonant DC / DC converter shown, the absolute value of the voltage Vc on the resonant capacitor is .
[0089] Since the voltage clamping range provided by the primary circuit 101 is between +Vp / 2 and -Vp / 2, and the voltage clamping range provided by the secondary circuit 103 is between +Vs / 2 and -Vs / 2, therefore, in order to make the resonant capacitor maintain its own voltage after the switching transistor is turned off and not discharge through the anti-parallel diode of the switching transistor, the absolute value of the voltage Vc on the resonant capacitor needs to satisfy < Vp / 2 + Vs / 2. In Figure 8 the converter shown, the threshold voltage Vthr can be selected as Vp / 2 + Vs / 2.
[0090] The above analysis shows that, in the case of a non-isolated converter, when both the primary and secondary circuits are full-bridge circuits, the threshold voltage is the sum of the DC source voltage and the secondary circuit output voltage. When the primary circuit is a full-bridge circuit and the secondary circuit is a half-bridge circuit, the threshold voltage is the sum of the DC source voltage and half of the secondary circuit output voltage. When both the primary and secondary circuits are half-bridge circuits, the threshold voltage is the sum of half of the DC source voltage and half of the secondary circuit output voltage. The controller controls the converter's switching frequency based on the voltage across the resonant capacitor and the threshold voltage. This allows the resonant capacitor to maintain its voltage after the switch is turned off, preventing discharge through the anti-parallel diode of the switch. This limits the resonant current, reduces the stress on the switch, and protects the switch.
[0091] In order to keep the state of the resonant cavity unchanged after the switch is turned off, the controller 104 of the converter provided in this application embodiment is further used to control the switch of the converter to turn off when the resonant current of the resonant cavity is zero and the voltage Vc on the resonant capacitor is less than the threshold voltage Vthr.
[0092] See Figure 9 The figure is a schematic diagram of a converter from operation to shutdown provided in an embodiment of this application.
[0093] Figure 9 by Figure 3 The converter shown is used as an example for explanation. Figure 9 The waveforms, from top to bottom, are: voltage UC1 on the first capacitor C1, voltage UC2 on the second capacitor C2, resonant current IL, driving square wave W1 of the first switch S1, and driving square wave W2 of the second switch S2. When the resonant current crosses zero, the waveforms of each switch are blocked. After the switches are turned off, the voltages UC1 on the first capacitor C1 and UC2 on the second capacitor C2 remain unchanged. Specifically, since the voltage Vc on the resonant capacitor is less than the threshold voltage Vthr, the voltage Vc on the resonant capacitor will not discharge through the anti-parallel diode. Therefore, when the resonant current IL of the resonant cavity is zero, the controller 104 controls the switch of the converter to turn off. The resonant current IL of the resonant cavity will remain zero, and the voltage Vc on the resonant capacitor will remain unchanged. That is, after the switch of the converter is turned off, the state of the resonant cavity remains unchanged.
[0094] In one possible implementation, the controller 104 is also configured to control the switching transistor of the converter to turn off before the resonant current IL of the resonant cavity crosses zero. The resonant current IL freewheels through the anti-parallel diode of the switching transistor of the converter. When the resonant current is zero, the voltage Vc on the resonant capacitor is less than the threshold voltage Vthr.
[0095] See also Figure 6If the resonant current IL of the resonant cavity 102 is in the positive direction from left to right before it crosses zero, and the second switch S2 and the third switch S3 are turned on at this time, then the primary voltage of the resonant cavity 102, i.e., the voltage U between points A and B, is... AB The voltage is negative; the fifth switch S5 and the eighth switch S8 are turned on, and the secondary voltage of the resonant cavity, i.e., the voltage between points C and D, is U. CD If the value is positive, then the switching transistors of the control converter are turned off before the resonant current IL of the resonant cavity 102 crosses zero. Due to the freewheeling effect of the resonant current IL, the current in the primary circuit 101 will continue to flow through the anti-parallel diodes of the second switching transistor S2 and the third switching transistor S3, and the current in the secondary circuit 103 will continue to flow through the anti-parallel diodes of the fifth switching transistor S5 and the eighth switching transistor S8, and continue to flow until zero, which is equivalent to the case where the second switching transistor S2, the third switching transistor S3, the fifth switching transistor S5 and the eighth switching transistor S8 are turned on, until the resonant current is zero.
[0096] Similarly, if the resonant current IL of resonant cavity 102 is in a negative direction from right to left before it crosses zero, and the first switch S1 and the fourth switch S4 are turned on at this time, the primary voltage of resonant cavity 102, i.e., the voltage U between points A and B, is... AB The signal is positive; the sixth switch S6 and the seventh switch S7 are turned on, and the secondary voltage of the resonant cavity 102, i.e., the voltage U between points C and D, is positive. CD The value is negative. Therefore, before the resonant current IL of the resonant cavity 102 crosses zero, the switching transistors of the control converter are turned off. Due to the freewheeling effect of the resonant current IL, the current in the primary circuit 101 will continue to flow through the anti-parallel diodes of the first switching transistor S1 and the fourth switching transistor S4, and the current in the secondary circuit 103 will continue to flow through the anti-parallel diodes of the sixth switching transistor S6 and the seventh switching transistor S7, and continue to flow until zero, which is equivalent to the case where the first switching transistor S1, the fourth switching transistor S4, the sixth switching transistor S6 and the seventh switching transistor S7 are turned on, until the resonant current is zero.
[0097] Therefore, the controller 104 is also used to control the switch of the converter to turn off before the resonant current IL of the resonant cavity 102 crosses zero, so that the resonant current IL of the resonant cavity 102 continues to remain zero after it reaches zero, the voltage Vc on the resonant capacitor is less than the threshold voltage Vthr, and the voltage Vc on the resonant capacitor remains unchanged. That is, after the switch of the converter is turned off, the state of the resonant cavity 102 can remain unchanged.
[0098] The converter provided in this application embodiment allows the controller to turn off the converter's switching transistor when or before the resonant current of the resonant cavity crosses zero, ensuring that the state of the resonant cavity remains unchanged after the switching transistor is turned off. This enables the controller to quickly enter a steady state by controlling the driving waveform of the switching transistor to continue from the driving waveform at the time of turn-off when the switching transistor is turned on again, thereby reducing the stress on the switching transistor and reducing transformer noise.
[0099] In order to make the drive waveform of the switching transistor continue with the drive waveform when it is turned off, in one possible implementation, the controller 104 is also used to form a drive signal of a complete switching cycle with the drive signal of the switching transistor before it is turned off during the first switching cycle after the switching transistor of the converter is turned off and the converter is stopped.
[0100] See Figure 10 The figure is a schematic diagram of the driving waveform of a switching transistor provided in an embodiment of this application.
[0101] Typically, in a resonant DC / DC converter, the driving waveform of each switch is a square wave with a 50% duty cycle. Taking the driving waveform of the first switch S1 as an example, the first switch S1 is turned off at time t1, and W11 is the driving waveform of the last switching cycle before turn-off; it is turned on again at time t2, and W12 is the driving waveform of the first switching cycle after turn-on. To ensure that the driving waveform W12 after turn-on continues the sequence from the driving waveform W11 before turn-off, the combined driving waveform W13 should still maintain a square wave with a 50% duty cycle. This ensures that the resonant cavity state is aligned with the turn-off state after the switch is turned on again, and since the turn-off state is already in a steady state, the switch can quickly enter a steady state after turn-on, thus eliminating transient processes to some extent and reducing the stress on the switch.
[0102] See Figure 11 The figure is a schematic diagram of a converter from shutdown to startup provided in an embodiment of this application.
[0103] Combination Figure 9 and Figure 11 As can be seen, when the converter starts up, the drive signal of the switching transistor is a continuation of the drive signal when the switching transistor is turned off. After the switching transistor is turned on, since the state of the resonant cavity remains unchanged, the converter will quickly enter steady-state operation, thereby reducing the stress on the switching transistor and reducing the noise of the transformer.
[0104] When the resonant current IL of the resonant cavity is turned off before the switching transistor of the converter is turned off, since the resonant current IL will still freewheel to zero through the anti-parallel diode of the switching transistor of the converter, the driving waveform of the switching transistor of the converter should be connected with the equivalent driving waveform when the resonant current IL crosses zero.
[0105] Based on the resonant DC / DC converters provided in the above embodiments, this application also provides a power conversion system. The power conversion system provided in this application includes any of the resonant DC / DC converters provided in the above embodiments. This application does not limit the type of power conversion system.
[0106] Based on the resonant DC / DC converter provided in the above embodiments, this application also provides a control method for the resonant DC / DC converter. The converter includes a primary-side circuit, a resonant cavity, and a secondary-side circuit; a first terminal of the primary-side circuit is connected to a DC source, a second terminal of the primary-side circuit is connected to a first terminal of the resonant cavity, and a second terminal of the resonant cavity is connected to the secondary-side circuit; the resonant cavity includes a resonant inductor and a resonant capacitor connected in series.
[0107] See Figure 12 The figure is a flowchart of a converter control method provided in an embodiment of this application.
[0108] The method includes:
[0109] S121: When the control converter is in the closed-circuit state and the resonant current of the resonant cavity is zero, the voltage on the resonant capacitor of the resonant cavity is less than the threshold voltage.
[0110] When the converter is a non-isolated converter, the threshold voltage is related to the voltage of the DC source and the output voltage of the secondary circuit; when the converter is an isolated converter and the resonant capacitor is connected to the primary circuit, the threshold voltage is related to the voltage of the DC source; when the converter is an isolation transformer and the resonant capacitor is connected to the secondary circuit, the threshold voltage is related to the output voltage of the secondary circuit.
[0111] For example, the controller controls the switching frequency of the converter based on the voltage across the resonant capacitor and the threshold voltage, ensuring that the voltage across the resonant capacitor is less than the threshold voltage after the converter's switching transistors are turned off. The value of the threshold voltage varies depending on the converter's structure.
[0112] The control method for a resonant DC / DC converter provided in this application embodiment controls the resonant DC / DC converter in a closed-loop state. When the resonant current of the resonant cavity is zero, the voltage on the resonant capacitor of the resonant cavity is less than the threshold voltage, effectively limiting the voltage on the resonant capacitor. As a result, the energy on the resonant capacitor is very low or non-existent, thus preventing discharge through the anti-parallel diode of the switching transistor. This effectively limits the resonant current of the resonant cavity after the switching transistor is turned off, reducing turn-off losses. Furthermore, it can shorten the oscillation time when the switching transistor is turned on again, allowing it to enter a stable operating state as quickly as possible. This reduces the voltage and current stress on the switching transistor during oscillation, protecting the switching transistor.
[0113] In one possible implementation, the converter is an isolated converter, with the resonant capacitor connected to the secondary circuit. If the secondary circuit is a half-bridge circuit, the threshold voltage is half of the output voltage of the secondary circuit. If the resonant capacitor is connected to the secondary circuit, and the secondary circuit is a full-bridge circuit, the threshold voltage is the output voltage of the secondary circuit. If the resonant capacitor is connected to the primary circuit, and the primary circuit is a full-bridge circuit, the threshold voltage is the voltage of the DC source.
[0114] In one possible implementation, when the converter is a non-isolated circuit and both the primary and secondary circuits are full-bridge circuits, the threshold voltage is the sum of the DC source voltage and the secondary circuit output voltage; when the primary circuit is a full-bridge circuit and the secondary circuit is a half-bridge circuit, the threshold voltage is the sum of half the secondary circuit output voltage and the DC source voltage; when both the primary and secondary circuits are half-bridge circuits, the threshold voltage is the sum of half the secondary circuit output voltage and half the DC source voltage.
[0115] In one possible implementation, the method further includes: controlling the switching transistor of the converter to turn off when the resonant current of the resonant cavity is zero and the voltage on the resonant capacitor is less than a threshold voltage.
[0116] In one possible implementation, the method further includes: turning off the switch of the converter before the resonant current of the resonant cavity crosses zero, allowing the resonant current to freewheel through the anti-parallel diode of the converter's switch, and when the resonant current is zero, the voltage on the resonant capacitor is less than the threshold voltage.
[0117] In one possible implementation, the method further includes: during the first switching cycle after the converter is shut down by turning off the switching transistor, the drive signal of the switching transistor and the drive signal of the switching transistor before shutdown form a drive signal for a complete switching cycle.
[0118] Based on the resonant DC / DC converter provided in the above embodiments, this application also provides a controller.
[0119] The controller provided in this application embodiment may include software to implement the control methods described above. Alternatively, the controller provided in this application embodiment may include hardware to implement the control methods described above. Or, the controller provided in this application embodiment may include both software and hardware, using a combination of software and hardware to execute the control methods described above.
[0120] In one possible implementation, see Figure 13 The figure is a schematic diagram of a controller provided in an embodiment of this application.
[0121] The controller may include a memory 1041 and a processor 1042. The processor 1042 can be connected to the switching transistors in the converter and can drive the individual switching transistors in the converter. Figure 13 As shown, the memory can be random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (Electronic Programmable ROM), registers, hard disks, removable disks, etc.
[0122] The memory 1041 can store computer instructions. When the computer instructions stored in the memory 1041 are executed by the processor 1042, the processor 1042 can be used to execute the control method of the converter. The memory 1041 can also store data, such as information like the threshold voltage involved in the above embodiments.
[0123] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.
[0124] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A resonant DC / DC converter, characterized in that, include: Primary circuit, resonant cavity, secondary circuit, and controller; The first end of the primary circuit is used to connect to a DC source, the second end of the primary circuit is connected to the first end of the resonant cavity, and the second end of the resonant cavity is connected to the secondary circuit. The controller is used to control the voltage on the resonant capacitor of the resonant cavity to be less than a threshold voltage when the converter is in a closed-circuit state and the resonant current of the resonant cavity is zero.
2. The converter according to claim 1, characterized in that, The converter is an isolation converter, the resonant capacitor is connected to the secondary circuit, and the secondary circuit is a half-bridge circuit. Therefore, the threshold voltage is half the output voltage of the secondary circuit; or... The converter is an isolation converter, the resonant capacitor is connected to the secondary circuit, and the secondary circuit is a full-bridge circuit. Therefore, the threshold voltage is the output voltage of the secondary circuit; or... The converter is an isolation converter, the resonant capacitor is connected to the primary circuit, and the primary circuit is a full-bridge circuit. Therefore, the threshold voltage is the voltage of the DC source.
3. The converter according to claim 1, characterized in that, When the converter is a non-isolated circuit, and both the primary circuit and the secondary circuit are full-bridge circuits, the threshold voltage is the sum of the voltage of the DC source and the output voltage of the secondary circuit. or, When the converter is a non-isolated circuit, the primary-side circuit is a full-bridge circuit, and the secondary-side circuit is a half-bridge circuit, the threshold voltage is the sum of half the output voltage of the secondary-side circuit and the voltage of the DC source; or, When the converter is a non-isolated circuit, the primary-side circuit is a half-bridge circuit, and the secondary-side circuit is a half-bridge circuit, the threshold voltage is the sum of half the output voltage of the secondary-side circuit and half the voltage of the DC source.
4. The converter according to any one of claims 1-3, characterized in that, The controller is further configured to control the switching transistor of the converter to turn off when the resonant current of the resonant cavity is zero and the voltage on the resonant capacitor is less than the threshold voltage.
5. The converter according to any one of claims 1-3, characterized in that, The controller is also configured to control the switching transistor of the converter to turn off before the resonant current of the resonant cavity crosses zero, the resonant current freewheels through the anti-parallel diode of the switching transistor of the converter, and the voltage on the resonant capacitor is less than the threshold voltage when the resonant current is zero.
6. The converter according to any one of claims 1-3, characterized in that, The controller is further configured to, during the first switching cycle after the converter is shut down by turning off its switching transistor, form a driving signal for a complete switching cycle with the driving signal of the switching transistor before it was turned off during the first switching cycle of restarting the converter.
7. The converter according to any one of claims 1-3, characterized in that, The controller is further configured to determine the switching frequency of the converter's switching transistor based on the voltage on the resonant capacitor and the threshold voltage, and control the converter to operate in a closed-loop state, where the resonant current of the resonant cavity is zero, such that the voltage on the resonant capacitor of the resonant cavity is less than the threshold voltage.
8. A power conversion system, characterized in that, Includes the resonant DC / DC converter as described in any one of claims 1-7.
9. A control method for a resonant DC / DC converter, characterized in that, The converter includes: a primary-side circuit, a resonant cavity, and a secondary-side circuit; the method includes: When the converter is in a closed-circuit state and the resonant current of the resonant cavity is zero, the voltage on the resonant capacitor of the resonant cavity is less than the threshold voltage.
10. The method according to claim 9, characterized in that, The converter is an isolation converter, wherein, The resonant capacitor is connected to the secondary circuit, and the secondary circuit is a half-bridge circuit. Therefore, the threshold voltage is half the output voltage of the secondary circuit; or... The resonant capacitor is connected to the secondary circuit, and the secondary circuit is a full-bridge circuit; therefore, the threshold voltage is the output voltage of the secondary circuit; or, The resonant capacitor is connected to the primary circuit, and the primary circuit is a full-bridge circuit. Therefore, the threshold voltage is the voltage of the DC source.
11. The control method according to claim 9, characterized in that, The converter is a non-isolated circuit, wherein, When both the primary-side circuit and the secondary-side circuit are full-bridge circuits, the threshold voltage is the sum of the voltage of the DC source and the output voltage of the secondary-side circuit; or, When the primary-side circuit is a full-bridge circuit and the secondary-side circuit is a half-bridge circuit, the threshold voltage is the sum of half the output voltage of the secondary-side circuit and the voltage of the DC source; or, When the primary circuit is a half-bridge circuit and the secondary circuit is a half-bridge circuit, the threshold voltage is the sum of half the output voltage of the secondary circuit and half the voltage of the DC source.
12. The control method according to any one of claims 9-11, characterized in that, The method further includes: When the resonant current in the resonant cavity is zero and the voltage on the resonant capacitor is less than the threshold voltage, the switching transistor of the converter is controlled to turn off.
13. The control method according to any one of claims 9-11, characterized in that, The method further includes: Before the resonant current of the resonant cavity crosses zero, the switch of the converter is turned off. The resonant current freewheels through the anti-parallel diode of the converter's switch. When the resonant current is zero, the voltage on the resonant capacitor is less than the threshold voltage of the anti-parallel diode.
14. The control method according to any one of claims 9-11, characterized in that, The method further includes: During the first switching cycle after the converter is turned off and shut down, when the converter is restarted, the drive signal of the switch and the drive signal of the switch before the switch was turned off form a drive signal for a complete switching cycle.
15. A controller, characterized in that, The controller is used to perform the method according to any one of claims 9-14.