A diode voltage stress improvement circuit and conversion circuit

Abstract

The present invention relates to a diode voltage stress improvement circuit and a conversion circuit. The diode voltage stress improvement circuit includes an output rectifier circuit, a current sampling circuit, a filter circuit, a comparison circuit, a short-circuit circuit, and an output capacitor. When the inductor current of the filter circuit is in an intermittent state and the current sampling result is a negative value, the filter circuit is short-circuited by the short-circuit circuit. At this time, the output capacitor quickly charges the parasitic capacitance of the diode in the output rectifier circuit through the short-circuit circuit and reaches a steady state. The inductor and the parasitic capacitance of the output diode cannot form an LC oscillation circuit, that is, the inductor voltage and the output capacitor voltage cannot be superimposed on the parasitic capacitance of the output diode. In this way, the maximum voltage stress of the diode of the output rectifier circuit can be reduced, so that the output rectifier circuit can use a diode with a lower withstand voltage, the forward voltage drop is relatively small, and the loss is relatively small, which is conducive to improving the overall efficiency of the power supply.

Description

Technical Field

[0001] The present invention relates to the field of power supply charging, and in particular to a diode voltage stress improvement circuit and a conversion circuit. Background Art

[0002] Currently, a phase-shifted full-bridge plus full-bridge rectifier topology is commonly used for charging new energy vehicles. In practical applications, when the inductor current in the filter circuit is discontinuous, the voltage stress on the output diode is much greater than when the inductor current is continuous. To ensure the reliability of the output diode, a higher voltage diode is often selected to meet the discontinuous inductor current operating conditions. However, a high-voltage diode has a relatively large forward voltage drop, resulting in greater losses and reduced overall power supply efficiency. Summary of the Invention

[0003] An embodiment of the present invention provides a diode voltage stress improvement circuit and a conversion circuit. The embodiment of the present invention invents a diode voltage stress improvement circuit. The filter circuit is short-circuited by a short-circuit circuit when the inductor current of the filter circuit is in a discontinuous state and the current sampling result is a negative value. At this time, the output capacitor quickly charges the parasitic capacitance of the diode in the output rectifier circuit through the short-circuit circuit and reaches a steady state. The parasitic capacitance of the inductor and the output diode cannot form an LC oscillation circuit, that is, the inductor voltage and the output capacitor voltage cannot be superimposed on the parasitic capacitance of the output diode. In this way, the maximum voltage stress of the diode of the output rectifier circuit can be reduced, so that the output rectifier circuit can use a diode with a lower voltage resistance, with a relatively small forward voltage drop and relatively small loss, which is conducive to improving the overall efficiency of the power supply.

[0004] In a first aspect, an embodiment of the present invention provides a diode voltage stress improvement circuit, the diode voltage stress improvement circuit comprising:

[0005] An output rectifier circuit, wherein the output rectifier circuit is respectively connected to the transformer, the current sampling circuit, the filter circuit and the short circuit;

[0006] The current sampling circuit is connected to the comparison circuit and the output capacitor respectively;

[0007] The filter circuit is connected to the short circuit and the output capacitor respectively; when the inductor current of the filter circuit is in a continuous state, the maximum voltage stress of the diode in the output rectifier circuit is a first voltage stress; when the inductor current of the filter circuit is in a discontinuous state, the maximum voltage stress of the diode in the output rectifier circuit is a second voltage stress, and the first voltage stress is equal to the second voltage stress;

[0008] the comparison circuit, the comparison circuit being connected to the short circuit, and the comparison circuit being grounded;

[0009] The short-circuit circuit is connected in series with the filter circuit, and is used to short-circuit the filter circuit when the inductive current of the filter circuit is in a discontinuous state;

[0010] The output capacitor is used to charge the diode in the output rectifier circuit through the short circuit when the inductive current of the filter circuit is in a discontinuous state.

[0011] Optionally, the short circuit includes a first diode and a first switching tube;

[0012] One end of the first diode is connected to the filter circuit and the output rectifier circuit respectively, the other end of the first diode is connected to the first end of the first switch tube, the second end of the first switch tube is connected to the filter circuit and one end of the output capacitor respectively, and the third end of the first switch tube is connected to the comparison circuit.

[0013] Optionally, the filtering circuit includes a first inductor;

[0014] One end of the first inductor is connected to the output rectifier circuit and one end of the first diode respectively, and the other end of the first inductor is connected to the second end of the first switch tube and one end of the output capacitor respectively.

[0015] Optionally, the comparison circuit includes a comparator;

[0016] The out-of-phase input terminal of the comparator is connected to the current sampling circuit, the in-phase input terminal of the comparator is grounded, and the output terminal of the comparator is connected to the third terminal of the first switch tube.

[0017] Optionally, the current sampling circuit includes a shunt, a first end of the shunt is connected to the output rectifier circuit, a second end of the shunt is connected to the second end of the output capacitor, and a third end of the shunt is connected to the out-of-phase input end of the comparator.

[0018] Optionally, when the inductor current of the first inductor is in a continuous state, the current sampling result of the shunt is a positive value;

[0019] When the inductor current of the first inductor is in a discontinuous state and the diode in the output rectifier circuit is not yet fully charged, the current sampling result of the shunt is a negative value;

[0020] When the inductor current of the first inductor is in a discontinuous state and the diode in the output rectifier circuit is finished charging, the current sampling result of the shunt is zero.

[0021] Optionally, when the current sampling result is a positive value, the comparator outputs a first comparison result, and the first switch tube is turned off;

[0022] When the current sampling result is a negative value or zero, the comparator outputs a second comparison result, and the first switch tube is turned on.

[0023] In a second aspect, an embodiment of the present invention provides a conversion circuit, the conversion circuit comprising:

[0024] a voltage source connected to an input capacitor;

[0025] The input capacitor is connected to the primary side conversion circuit;

[0026] The primary side conversion circuit is connected to the transformer;

[0027] the transformer;

[0028] As the aforementioned diode voltage stress improvement circuit, the diode voltage stress improvement circuit is connected to the transformer.

[0029] Optionally, the primary side conversion circuit includes a second switching tube, a third switching tube, a fourth switching tube, a fifth switching tube, a second inductor and a first capacitor;

[0030] One end of the second switching tube is respectively connected to one end of the voltage source, one end of the input capacitor and one end of the fourth switching tube; the other end of the second switching tube is respectively connected to one end of the third switching tube and one end of the second inductor; the other end of the fourth switching tube is respectively connected to one end of the primary winding of the transformer and one end of the fifth switching tube; the other end of the third switching tube is respectively connected to the other end of the voltage source, the other end of the input capacitor and the other end of the fifth switching tube; the other end of the second inductor is connected to one end of the first capacitor; and the other end of the first capacitor is connected to the other end of the primary winding.

[0031] In a third aspect, an embodiment of the present invention provides a power supply, which includes the conversion circuit of the second aspect.

[0032] In a fourth aspect, an embodiment of the present invention provides a charging pile, which includes the conversion circuit of the second aspect.

[0033] The implementation of the embodiments of the present invention has the following beneficial effects:

[0034] It can be seen that the embodiment of the present invention invents a diode voltage stress improvement circuit. When the inductor current of the filter circuit is in a discontinuous state and the current sampling result is a negative value, the filter circuit is short-circuited through the short-circuit circuit. At this time, the output capacitor quickly charges the parasitic capacitance of the diode in the output rectifier circuit through the short-circuit circuit and reaches a steady state. The parasitic capacitance of the inductor and the output diode cannot form an LC oscillation circuit, that is, the inductor voltage and the output capacitor voltage cannot be superimposed on the parasitic capacitance of the output diode. In this way, the maximum voltage stress of the diode of the output rectifier circuit can be reduced, so that the output rectifier circuit can use a diode with a lower voltage resistance, with a relatively small forward voltage drop and relatively small loss, which is beneficial to improving the overall efficiency of the power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 This is a schematic diagram of a diode voltage stress improvement circuit provided in an embodiment of the present application;

[0037] Figure 2 is a circuit diagram of a diode voltage stress improvement circuit provided in an embodiment of the present application;

[0038] Figure 3 The present invention provides a curve diagram of transformer secondary voltage and inductor current;

[0039] Figure 4 A full-bridge rectifier circuit of the first moment mode provided in an embodiment of the present application;

[0040] Figure 5 A full-bridge rectifier circuit in a second moment mode provided in an embodiment of the present application;

[0041] Figure 6 Another curve diagram of transformer secondary voltage and inductor current provided in an embodiment of the present application;

[0042] Figure 7 This is a full-bridge rectifier circuit in the third moment mode provided by an embodiment of the present application;

[0043] Figure 8 This is a full-bridge rectifier circuit of the fourth moment mode provided by an embodiment of the present application;

[0044] Figure 9 This is another curve diagram of transformer secondary voltage and inductor current provided in an embodiment of the present application;

[0045] Figure 10 is a circuit diagram of another diode voltage stress improvement circuit provided in an embodiment of the present application;

[0046] Figure 11 This is a circuit diagram of another diode voltage stress improvement circuit provided in an embodiment of the present application;

[0047] Figure 12 Schematic diagram of a conversion circuit provided in an embodiment of the present application;

[0048] Figure 13 This is a circuit diagram of a voltage source, input capacitor and primary-side conversion circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0049] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0050] The terms "first," "second," "third," and "fourth," etc., in the specification, claims, and drawings of the present invention are used to distinguish between different items, not to describe a specific order. Furthermore, the terms "including," "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements, but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0051] Reference herein to an "embodiment" means that a particular feature, result, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute a separate or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0052] In order to facilitate understanding of the technical solution of this application, the relevant technologies involved in this application are first introduced.

[0053] See Figure 1 , Figure 1 This is a schematic diagram of a diode voltage stress improvement circuit provided in an embodiment of the present application, such as Figure 1As shown, the diode voltage stress improvement circuit 1 includes an output rectification circuit 10, a current sampling circuit 20, a filter circuit 30, a comparison circuit 40, a short circuit 50 and an output capacitor C1.

[0054] The output rectifier circuit 10 is respectively connected to the transformer 60, the current sampling circuit 20, the filter circuit 30 and the short-circuit circuit 50; the current sampling circuit 20 is respectively connected to the comparison circuit 40 and the output capacitor C1; the filter circuit 30 is respectively connected to the short-circuit circuit 50 and the output capacitor C1; the comparison circuit 40 is connected to the short-circuit circuit 50; and the comparison circuit 40 is grounded.

[0055] Among them, when the inductive current of the filter circuit 30 is in a continuous state, the maximum voltage stress of the diode in the output rectifier circuit 10 is a first voltage stress; when the inductive current of the filter circuit 30 is in a discontinuous state, the maximum voltage stress of the diode in the output rectifier circuit 10 is a second voltage stress, and the first voltage stress is equal to the second voltage stress.

[0056] The short-circuit circuit 50 is used to short-circuit the filter circuit 30 when the inductive current of the filter circuit 30 is in a discontinuous state, and the output capacitor C1 is used to charge the diode in the output rectifier circuit 10 through the short-circuit circuit 50 when the inductive current of the filter circuit 30 is in a discontinuous state.

[0057] See also Figure 2 , Figure 2 This is a circuit diagram of a diode voltage stress improvement circuit provided in an embodiment of the present application. The shorting circuit 50 in this embodiment includes a first diode D5 and a first switch Q1. One end of the first diode D5 is connected to the filter circuit 30 and the output rectifier circuit 10, respectively. The other end of the first diode D5 is connected to the first end of the first switch Q1. The second end of the first switch Q1 is connected to the filter circuit 30 and one end of the output capacitor C1, respectively. The third end of the first switch Q1 is connected to the comparison circuit 40. The current is in the forward direction.

[0058] In some embodiments, the filter circuit 30 includes a first inductor L1; one end of the first inductor L1 is respectively connected to the output rectifier circuit 10 and one end of the first diode D5, and the other end of the first inductor L1 is respectively connected to the second end of the first switch tube Q1 and one end of the output capacitor C1.

[0059] In some embodiments, the comparison circuit 40 includes a comparator; the out-of-phase input of the comparator is connected to the current sampling circuit 20, the in-phase input of the comparator is grounded, and the output of the comparator is connected to the third terminal of the first switch tube Q1.

[0060] In some embodiments, the current sampling circuit 20 includes a shunt, a first end of the shunt is connected to the output rectifier circuit, a second end of the shunt is connected to the second end of the output capacitor C1, and a third end of the shunt is connected to the out-of-phase input end of the comparator.

[0061] In addition to the shunt, other current sampling devices may also replace the shunt, such as a sampling resistor, a current transformer, and a Hall current sensor, which are not limited here.

[0062] In some embodiments, when the inductor current of the first inductor L1 is in a continuous state, the current sampling result of the shunt is a positive value;

[0063] When the inductor current of the first inductor L1 is in a discontinuous state and the diode in the output rectifier circuit 10 is not yet fully charged, the current sampling result of the shunt is a negative value;

[0064] When the inductor current of the first inductor L1 is in a discontinuous state and the diode in the output rectifier circuit 10 is finished charging, the current sampling result of the shunt is zero.

[0065] In some embodiments, when the current sampling result is a positive value, the comparator outputs a first comparison result, and the first switch is turned off;

[0066] When the current sampling result is a negative value or zero, the comparator outputs a second comparison result, and the first switch tube is turned on.

[0067] The first comparison result may be 0, and the second comparison output result may be 1.

[0068] In some embodiments, the output rectifier circuit 10 includes a second diode D1, a third diode D2, a fourth diode D3 and a fifth diode D4, one end of the second diode D1 is respectively connected to one end of the first inductor L1 and one end of the third diode D2, the other end of the second diode D1 is respectively connected to one end of the secondary winding of the transformer 60 and one end of the fourth diode D3, the other end of the third diode D2 is respectively connected to the other end of the secondary winding and one end of the fifth diode D4, and the other end of the fifth diode D4 is respectively connected to the other end of the fourth diode D3 and the current sampling circuit 20.

[0069] The output diode voltage stress of the differential-mode inductor (first inductor) in the full-bridge rectifier circuit is higher when the inductor current is discontinuous than when the inductor current is continuous. Figure 3-Figure 5 , Figure 3: This embodiment of the present application provides a curve diagram of transformer secondary voltage and inductor current. Figure 4 This is a full-bridge rectifier circuit of the first moment mode provided by an embodiment of the present application. Figure 5 The embodiment of the present application provides a full-bridge rectifier circuit of the second moment mode. The full-bridge rectifier circuit includes an output rectifier current circuit, a filter circuit and an output capacitor C1. The output rectifier circuit includes a second diode D1, a third diode D2, a fourth diode D3 and a fifth diode D4. The filter circuit includes a first inductor L1. Taking the second diode D1 as an example, when the current of the first inductor L1 is continuous, at the moment t1-t2 mode, that is, the first moment mode, as shown in FIG. Figure 4 As shown, the current flow direction of the full-bridge rectifier circuit is Figure 4 The direction of the arrow in , the mode at time t2-t3, that is, the second mode, such as Figure 5 As shown, the current flow direction of the full-bridge rectifier circuit is Figure 5 The arrows in the figure indicate the direction of the voltage across the transformer. At time t1-t2, the voltage across the transformer is 0V, and the second, third, fourth, and fifth diodes D1, D2, D3, and D4 are all conducting. VD1 = VD2 = VD3 = VD4 = 0V. At time t2, the energy transfer phase begins, and the transformer voltage changes from zero to Vs. The third and fourth diodes D2 and D3 conduct, while the second and fifth diodes D1 and D4 are off. VD2 = 0V, and VD1 = Vs + VD2 = Vs. At this time, the voltage stress on the second diode D1 is the highest.

[0070] Among them, see Figure 6-Figure 8 , Figure 6 This is another curve diagram of transformer secondary voltage and inductor current provided in an embodiment of the present application. Figure 7 This is a full-bridge rectifier circuit of the third moment mode provided by an embodiment of the present application. Figure 8 It is a full-bridge rectifier circuit of the fourth moment mode provided by an embodiment of the present application. Taking the second diode D1 as an example, when the current of the first inductor L1 is intermittent, at the moment t1-t2, the voltage across the transformer is 0V; the second diode D1, the third diode D2, the fourth diode D3, and the fifth diode D4 are all turned on. VD1=VD2=VD3=VD4=0V; at the moment t1-t2, the voltage stress of the second diode D1 is the same as when the current is continuous. At the moment t2-t3, the output capacitor voltage is equal to Vo, and the output capacitor charges the parasitic capacitance of the output diode through the first inductor L1. The first inductor L1 and the parasitic capacitance of the output diode form an LC oscillation circuit. During the oscillation process, the voltage of the first inductor L1 will be superimposed on the output capacitor voltage and act on the parasitic capacitance of the output diode. VD2+VD4=VD1+VD3 will be charged to a maximum of 2Vo, such as Figure 7As shown. At this time, VD1 = VD3 = VD2 = VD4 = Vo, and the secondary voltage of transformer 60 is still equal to 0V. In the modal state at time t3, the current in the first inductor L1 is equal to 0. At time t3-t4, the negative half-cycle energy transfer begins, and the secondary winding of the transformer charges the parasitic capacitance of the second diode D1 through the parasitic capacitance of the third diode D2. The secondary voltage gradually rises from 0V to Vs, VD1 gradually rises from Vo to Vo+Vs / 2, and VD2 gradually decreases from Vo to Vo-Vs / 2. As shown in the modal diagram at time t4. At this time, the voltage stress on the second diode D1 is the highest, which is Vs / 2+Vo. After time t4: the voltage on the parasitic capacitance of the second diode D1, the third diode D2, the fourth diode D3, and the fifth diode D4 transfers energy to the output capacitor through the first inductor L1. VD1 gradually decreases to Vs, and VD2 gradually decreases to 0V. The third diode D2 turns on and enters the energy transfer stage. It can be seen that when the current in the first inductor L1 is continuous, the output diode voltage stress reaches a maximum of Vs. When the current in the first inductor L1 is discontinuous, the output diode voltage stress reaches Vs / 2+Vo. Typically, Vs=Vo / 0.9. When the current in the first inductor L1 is continuous, the output diode voltage stress reaches a maximum of Vs=1.11Vo. When the current in the inductor L1 is discontinuous, the output diode voltage stress reaches Vs / 2+Vo=1.56Vo. In other words, the output diode voltage stress in the discontinuous state is approximately 0.45V higher than that in the continuous state.

[0071] Among them, see Figures 9-11 , Figure 9 This is another curve diagram of transformer secondary voltage and inductor current provided in an embodiment of the present application. Figure 10 This is another diode voltage stress improvement circuit provided by the embodiment of the present application. Figure 11 It is another diode voltage stress improvement circuit provided by the embodiment of the present application. After the full-bridge rectifier circuit introduces the current sampling circuit, the comparison circuit and the short-circuit circuit, a diode voltage stress improvement circuit is formed. The diode voltage stress improvement circuit includes an output rectifier current circuit, a filter circuit, a current sampling circuit, a comparison circuit, a short-circuit circuit and an output capacitor C1. The output rectifier circuit includes a second diode D1, a third diode D2, a fourth diode D3 and a fifth diode D4. The filter circuit includes a first inductor L1, and the short-circuit circuit includes a first switch tube Q1 and a first diode D5. Taking the second diode D1 as an example, when the current of the first inductor L1 is discontinuous, at the time mode of t2, that is, the third time mode, the current flow direction of the diode voltage stress improvement circuit is Figure 10 In the direction of the arrow in the figure, at the moment t3 mode, that is, the fourth moment mode, the current flow direction of the diode voltage stress improvement circuit is Figure 11The direction of the arrow in the figure. At time t1-t2, the current in the first inductor L1 is in the continuous phase, and the voltage across the transformer is 0V. The second diode D1, third diode D2, fourth diode D3, and fifth diode D4 are all conducting, with VD1 = VD2 = VD3 = VD4 = 0V. At time t2-t3, the output capacitor voltage is equal to Vo, and the output capacitor charges the parasitic capacitance of the output diode through the first inductor L1. At this time, the current sampling result is negative, the comparator output is 1, and the first switch Q1 is turned on. The output capacitor charges the parasitic capacitance of the output diode through the first switch Q1 and the first diode D5, as shown in the modal diagram at time t2. Because this charging circuit has no inductive components and low impedance, the parasitic capacitance voltage of a single output diode is charged to half the output voltage in a very short time. In steady state, the voltage VD1 = VD2 = VD3 = VD4 = Vo / 2. At time t3-t4: energy transfer begins in the negative half-cycle, and the secondary winding charges VD1 through VD2, as shown in the modal diagram at time t3. Since Vs > Vo, VD2 can gradually decrease from Vo / 2 to 0V, and the third diode D2 turns on. After the third diode D2 turns on, the voltage across the second diode D1 equals the secondary winding voltage. Eventually, the secondary voltage rises to Vs, and the voltage across the second diode D1 also rises to Vs. As can be seen, when the differential-mode inductor current is discontinuous, the output diode voltage stress reaches a maximum of Vs. When the differential-mode inductor current is continuous, the output diode voltage stress also reaches a maximum of Vs. The output diode voltage stress is the same whether the current in the first inductor L1 is discontinuous or continuous. In fact, compared to the full-bridge rectifier circuit, the diode voltage stress improvement circuit reduces the maximum output diode voltage stress from Vs / 2+Vo=1.56Vo to Vs=1.1Vo, a reduction of 0.45V. This significantly reduces the output diode voltage stress when the current of the first inductor L1 is discontinuous. Therefore, the output diode can be selected with a lower voltage resistance. A diode with a lower voltage resistance has a smaller forward voltage drop VF, lower losses, and higher overall power supply efficiency.

[0072] It can be seen that the diode voltage stress improvement circuit introduces a current sampling circuit, a comparison circuit and a short-circuit circuit on the basis of the full-bridge rectifier circuit, and short-circuits the filter circuit through the short-circuit circuit when the inductor current of the filter circuit is in a discontinuous state and the current sampling result is a negative value. At this time, the output capacitor quickly charges the parasitic capacitance of the diode in the output rectifier circuit through the short-circuit circuit and reaches a steady state. The parasitic capacitance of the inductor and the output diode cannot form an LC oscillation circuit, that is, the inductor voltage and the output capacitor voltage cannot be superimposed on the parasitic capacitance of the output diode. This can reduce the maximum voltage stress of the diode in the output rectifier circuit, so that the output rectifier circuit can use a diode with a lower withstand voltage, which has a relatively small forward voltage drop and relatively small loss, which is beneficial to improving the overall efficiency of the power supply.

[0073] See also Figure 12, Figure 12 This is a schematic diagram of the architecture of a conversion circuit provided in an embodiment of the present application. The conversion circuit includes a voltage source Vi, an input capacitor Ci, a primary-side conversion circuit 70, a transformer 60 and a diode voltage stress improvement circuit 1, wherein the voltage source Vi is connected to the input capacitor Ci, the input capacitor Ci is connected to the primary-side conversion circuit 70, and the diode voltage stress improvement circuit 1 is connected to the transformer 60.

[0074] See also Figure 13 , Figure 13 is a circuit diagram of a voltage source, input capacitor, and primary-side conversion circuit provided in an embodiment of the present application. The primary-side conversion circuit 70 includes a second switch tube Q2, a third switch tube Q3, a fourth switch tube Q4, a fifth switch tube Q5, a second inductor L2, and a first capacitor C2;

[0075] One end of the second switch tube Q2 is respectively connected to one end of the voltage source Vi, one end of the input capacitor Ci, and one end of the fourth switch tube Q4. The other end of the second switch tube Q2 is respectively connected to one end of the third switch tube Q3 and one end of the second inductor L2. The other end of the fourth switch tube Q4 is respectively connected to one end of the primary winding of the transformer 60 and one end of the fifth switch tube Q5. The other end of the third switch tube Q3 is respectively connected to the other end of the voltage source Vi, the other end of the input capacitor Ci, and the other end of the fifth switch tube Q5. The other end of the second inductor L2 is connected to one end of the first capacitor C2, and the other end of the first capacitor C2 is connected to the other end of the primary winding.

[0076] Optionally, the filter circuit 30 includes a first inductor L1; one end of the first inductor L1 is respectively connected to the output rectifier circuit 10 and one end of the first diode D5, and the other end of the first inductor L1 is respectively connected to the second end of the first switch tube Q1 and one end of the output capacitor C1.

[0077] Optionally, the comparison circuit 40 includes a comparator; the out-of-phase input terminal of the comparator is connected to the current sampling circuit 20, the in-phase input terminal of the comparator is grounded, and the output terminal of the comparator is connected to the third terminal of the first switch tube Q1.

[0078] Optionally, the current sampling circuit 20 includes a shunt, a first end of the shunt is connected to the output rectifier circuit, a second end of the shunt is connected to the second end of the output capacitor C1, and a third end of the shunt is connected to the out-of-phase input end of the comparator.

[0079] Optionally, when the inductor current of the first inductor L1 is in a continuous state, the current sampling result of the shunt is a positive value;

[0080] When the inductor current of the first inductor L1 is in a discontinuous state and the diode in the output rectifier circuit 10 is not yet fully charged, the current sampling result of the shunt is a negative value;

[0081] When the inductor current of the first inductor L1 is in a discontinuous state and the diode in the output rectifier circuit 10 is finished charging, the current sampling result of the shunt is zero.

[0082] Optionally, when the current sampling result is a positive value, the comparator outputs a first comparison result, and the first switch tube is turned off;

[0083] When the current sampling result is a negative value or zero, the comparator outputs a second comparison result, and the first switch tube is turned on.

[0084] Optionally, the output rectifier circuit 10 includes a second diode D1, a third diode D2, a fourth diode D3 and a fifth diode D4, one end of the second diode D1 is respectively connected to one end of the first inductor L1 and one end of the third diode D2, the other end of the second diode D1 is respectively connected to one end of the secondary winding of the transformer 60 and one end of the fourth diode D3, the other end of the third diode D2 is respectively connected to the other end of the secondary winding and one end of the fifth diode D4, and the other end of the fifth diode D4 is respectively connected to the other end of the fourth diode D3 and the current sampling circuit 20.

[0085] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0086] In the several embodiments provided in this application, it should be understood that the disclosed devices can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the above-mentioned units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, and the indirect coupling or communication connection of devices or units can be electrical or other forms.

[0087] The units described above as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0088] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0089] If the above-mentioned integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of the present application, or the part that contributes to the existing technology, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a memory and includes a number of instructions for enabling a computer device (which can be a personal computer, server or network device, etc.) to execute all or part of the steps of the above-mentioned methods in each embodiment of the present application. The aforementioned memory includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk, etc. Various media that can store program code.

[0090] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable memory, which may include: a flash drive, a read-only memory, a random access memory, a magnetic disk or an optical disk, etc.

[0091] The above is a detailed introduction to the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of the present application. At the same time, for those skilled in the art, according to the idea of the present application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A diode voltage stress improvement circuit, characterized in that: The diode voltage stress improvement circuit comprises: an output rectifier circuit, wherein an input end of the output rectifier circuit is connected to a secondary winding of a transformer, a first output end of the output rectifier circuit is respectively connected to a filter circuit and a short-circuit circuit, and a second output end of the output rectifier circuit is connected to a current sampling circuit; The current sampling circuit, wherein a first end of the current sampling circuit is connected to the second output end of the output rectifier circuit, a second end of the current sampling circuit is connected to the second end of the output capacitor, and a third end of the current sampling circuit is connected to the comparison circuit; The filter circuit, wherein a first end of the filter circuit is connected to a first output end of the output rectifier circuit, and a second end of the filter circuit is connected to a first end of the output capacitor; when the inductor current of the filter circuit is in a continuous state, a maximum voltage stress of the diode in the output rectifier circuit is a first voltage stress; when the inductor current of the filter circuit is in a discontinuous state, a maximum voltage stress of the diode in the output rectifier circuit is a second voltage stress, and the first voltage stress is equal to the second voltage stress; The comparison circuit, wherein the out-of-phase input terminal of the comparison circuit is connected to the third terminal of the current sampling circuit, the in-phase input terminal of the comparison circuit is grounded, and the output terminal of the comparison circuit is connected to the short circuit; The short-circuit circuit is connected in parallel with the filter circuit, and is used to short-circuit the filter circuit when the inductive current of the filter circuit is in a discontinuous state; The output capacitor is used to charge the diode in the output rectifier circuit through the short circuit when the inductive current of the filter circuit is in a discontinuous state; The short circuit includes a first diode and a first switch tube; The cathode of the first diode is respectively connected to the first end of the filter circuit and the first output end of the output rectifier circuit, the anode of the first diode is connected to the first end of the first switching tube, the second end of the first switching tube is respectively connected to the second end of the filter circuit and the first end of the output capacitor, and the control end of the first switching tube is connected to the output end of the comparison circuit.

2. The diode voltage stress improvement circuit according to claim 1, wherein: The filtering circuit includes a first inductor; One end of the first inductor is connected to the first output end of the output rectifier circuit and the cathode of the first diode respectively, and the other end of the first inductor is connected to the second end of the first switch tube and the first end of the output capacitor respectively.

3. The diode voltage stress improvement circuit according to claim 2, wherein: The comparison circuit includes a comparator; The out-of-phase input terminal of the comparator is connected to the current sampling circuit, the in-phase input terminal of the comparator is grounded, and the output terminal of the comparator is connected to the control terminal of the first switch tube.

4. The diode voltage stress improvement circuit according to claim 3, wherein: The current sampling circuit includes a shunt, a first end of the shunt is connected to the second output end of the output rectifier circuit, a second end of the shunt is connected to the second end of the output capacitor, and a third end of the shunt is connected to the out-of-phase input end of the comparator.

5. The diode voltage stress improvement circuit according to claim 4, characterized in that: When the inductor current of the first inductor is in a continuous state, the current sampling result of the shunt is a positive value; When the inductor current of the first inductor is in a discontinuous state and the diode in the output rectifier circuit is not yet fully charged, the current sampling result of the shunt is a negative value; When the inductor current of the first inductor is in a discontinuous state and the diode in the output rectifier circuit is finished charging, the current sampling result of the shunt is zero.

6. The diode voltage stress improvement circuit according to claim 5, characterized in that: When the current sampling result is a positive value, the comparator outputs a first comparison result, and the first switch tube is turned off; When the current sampling result is a negative value or zero, the comparator outputs a second comparison result, and the first switch tube is turned on.

7. The diode voltage stress improvement circuit according to claim 2, wherein: The output rectifier circuit includes a second diode, a third diode, a fourth diode and a fifth diode, one end of the second diode is respectively connected to one end of the first inductor and one end of the third diode, the other end of the second diode is respectively connected to one end of the secondary winding of the transformer and one end of the fourth diode, the other end of the third diode is respectively connected to the other end of the secondary winding and one end of the fifth diode, and the other end of the fifth diode is respectively connected to the other end of the fourth diode and the current sampling circuit.

8. A conversion circuit, characterized in that: The conversion circuit comprises: a voltage source connected to an input capacitor; The input capacitor is connected to the primary side conversion circuit; The primary side conversion circuit is connected to the primary winding of the transformer; the transformer; The diode voltage stress improvement circuit according to any one of claims 1 to 7, wherein the diode voltage stress improvement circuit is connected to the transformer.

9. The conversion circuit according to claim 8, characterized in that: The primary side conversion circuit includes a second switching tube, a third switching tube, a fourth switching tube, a fifth switching tube, a second inductor and a first capacitor; One end of the second switching tube is respectively connected to one end of the voltage source, one end of the input capacitor and one end of the fourth switching tube; the other end of the second switching tube is respectively connected to one end of the third switching tube and one end of the second inductor; the other end of the fourth switching tube is respectively connected to one end of the primary winding of the transformer and one end of the fifth switching tube; the other end of the third switching tube is respectively connected to the other end of the voltage source, the other end of the input capacitor and the other end of the fifth switching tube; the other end of the second inductor is connected to one end of the first capacitor; and the other end of the first capacitor is connected to the other end of the primary winding.

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