Diode voltage stress improvement circuit and conversion circuit

Abstract

The invention relates to a diode voltage stress improving circuit and a conversion circuit, and the diode voltage stress improving circuit comprises an output rectification circuit, a current sampling circuit, a filter circuit, a comparison circuit, a short circuit and an output capacitor. When the inductive current of the filter circuit is in an interrupted state and the current sampling result is a negative value, the filter circuit is short-circuited through the short-circuit circuit, at the moment, the output capacitor rapidly charges the parasitic capacitor of the diode in the output rectification circuit through the short-circuit circuit and reaches a steady state, and the inductor and the parasitic capacitor of the output diode cannot form an LC oscillation loop. In other words, the inductor voltage and the output capacitor voltage cannot be superposed to act on the parasitic capacitance of the output diode, so that the maximum voltage stress of the diode of the output rectification circuit can be reduced, the output rectification circuit can select the diode with low withstand voltage, the forward voltage drop is relatively small, the loss is relatively small, and the overall efficiency of the power supply is improved.

Description

Technical Field

[0001] The 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] At present, the phase-shifted full-bridge plus full-bridge rectifier is a commonly used topology for charging new energy vehicles. In practical applications, the voltage stress of the output diode when the inductor current in the filter circuit is discontinuous will be much greater than the voltage stress of the output diode when the inductor current is continuous. In order to ensure the reliability of the output diode, a diode with a higher withstand voltage is often selected to meet the discontinuous working condition of the inductor current. However, the forward voltage drop of the diode with a high withstand voltage is relatively large, and the loss is greater, which will reduce the overall efficiency of the power supply. Summary of the invention

[0003] The 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 withstand voltage, the forward voltage drop is relatively small, and the loss is relatively small, which is beneficial 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: An output rectifier circuit, wherein the output rectifier circuit is respectively connected to a transformer, a current sampling circuit, a filter circuit and a short circuit; The current sampling circuit is connected to the comparison circuit and the output capacitor respectively; 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, and 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; The comparison circuit is connected to the short circuit, and the comparison circuit is grounded; 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; The output capacitor is used to charge the diode in the output rectifier circuit through the short circuit when the inductor current of the filter circuit is in a discontinuous state.

[0005] Optionally, the short circuit includes a first diode and a first switch tube; One end of the first diode is respectively connected to the filter circuit and the output rectifier circuit, 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 respectively connected to the filter circuit and one end of the output capacitor, and the third end of the first switch tube is connected to the comparison circuit.

[0006] Optionally, the filtering circuit includes a first inductor; One end of the first inductor is respectively connected to the output rectifier circuit and one end of the first diode, and the other end of the first inductor is respectively connected to the second end of the first switch tube and one end of the output capacitor.

[0007] Optionally, 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 third terminal of the first switch tube.

[0008] 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.

[0009] 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; When the inductor current of the first inductor is in a discontinuous state and the diode in the output rectifier circuit is not 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.

[0010] 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; 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.

[0011] In a second aspect, an embodiment of the present invention provides a conversion circuit, wherein the conversion circuit includes: A voltage source, the voltage source is connected to the input capacitor; The input capacitor is connected to the primary side conversion circuit; The primary side conversion circuit is connected to a transformer; The transformer; As the aforementioned diode voltage stress improvement circuit, the diode voltage stress improvement circuit is connected to the transformer.

[0012] Optionally, the primary side conversion circuit includes a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a second inductor and a first capacitor; One end of the second switch tube is respectively connected to one end of the voltage source, one end of the input capacitor and one end of the fourth switch tube, the other end of the second switch tube is respectively connected to one end of the third switch tube and one end of the second inductor, the other end of the fourth switch tube is respectively connected to one end of the primary winding of the transformer and one end of the fifth switch tube, the other end of the third switch 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 switch 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.

[0013] In a third aspect, an embodiment of the present invention provides a power supply, and the power supply includes the conversion circuit of the second aspect.

[0014] In a fourth aspect, an embodiment of the present invention provides a charging pile, and the charging pile includes the conversion circuit of the second aspect.

[0015] Implementing the embodiments of the present invention has the following beneficial effects: It can be seen that the embodiment of the present invention invents a diode voltage stress improvement circuit, which short-circuits the filter circuit through 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 withstand voltage, and the forward voltage drop is relatively small, and the loss is relatively small, which is beneficial to improving the overall efficiency of the power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0017] Figure 1 A schematic diagram of a diode voltage stress improvement circuit provided in an embodiment of the present application; Figure 2 is a circuit diagram of a diode voltage stress improvement circuit provided in an embodiment of the present application; Figure 3 The embodiment of the present application provides a curve diagram of transformer secondary voltage and inductor current; Figure 4 A full-bridge rectifier circuit in a first moment mode provided in an embodiment of the present application; Figure 5 A full-bridge rectifier circuit in a second moment mode provided in an embodiment of the present application; Figure 6 Another curve diagram of transformer secondary voltage and inductor current provided by an embodiment of the present application; Figure 7 A full-bridge rectifier circuit of the third moment mode provided in an embodiment of the present application; Figure 8 A full-bridge rectifier circuit of the fourth moment mode provided in an embodiment of the present application; Fig. 9 is another curve diagram of transformer secondary voltage and inductor current provided in an embodiment of the present application; Fig.10 is a circuit diagram of another diode voltage stress improvement circuit provided in an embodiment of the present application; Fig.11 is a circuit diagram of another diode voltage stress improvement circuit provided in an embodiment of the present application; Fig.12 is a schematic diagram of the architecture of a conversion circuit provided in an embodiment of the present application; Fig.13 It is a circuit diagram of a voltage source, an input capacitor and a primary side conversion circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] The terms "first", "second", "third" and "fourth" in the specification, claims and drawings of the present invention are used to distinguish different objects rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices.

[0020] Reference to "embodiments" herein means that a particular feature, result, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0021] In order to facilitate understanding of the technical solution of this application, the relevant technologies involved in this application are first introduced.

[0022] See also Figure 1 , Figure 1 The schematic diagram of a diode voltage stress improvement circuit provided in an embodiment of the present application is as follows: Figure 1 As 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.

[0023] Among them, 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 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 50 and the output capacitor C1, the comparison circuit 40 is connected to the short circuit 50, and the comparison circuit 40 is grounded.

[0024] Among them, when the inductor 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 the first voltage stress, and when the inductor 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 the second voltage stress, and the first voltage stress is equal to the second voltage stress.

[0025] The short circuit 50 is used to short the filter circuit 30 when the inductor 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 50 when the inductor current of the filter circuit 30 is in a discontinuous state.

[0026] See also Figure 2 , Figure 2 : is a circuit diagram of a diode voltage stress improvement circuit provided in an embodiment of the present application. The short-circuit circuit 50 of this embodiment includes a first diode D5 and a first switch tube 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 tube Q1, the second end of the first switch tube Q1 is connected to the filter circuit 30 and one end of the output capacitor C1 respectively, and the third end of the first switch tube Q1 is connected to the comparison circuit 40. The current is forward.

[0027] 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.

[0028] In some embodiments, 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.

[0029] 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.

[0030] In addition to the shunt, other current sampling devices may also replace the shunt, such as sampling resistors, current transformers, and Hall current sensors, which are not limited here.

[0031] 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; 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 fully charged, the current sampling result of the shunt is a negative value; 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.

[0032] In some embodiments, 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.

[0033] The first comparison result may be 0, and the second comparison output result may be 1.

[0034] 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.

[0035] Among them, the output diode voltage stress of the differential mode inductor (first inductor) in the full-bridge rectifier circuit in the discontinuous state is higher than the output diode voltage stress of the differential mode inductor in the continuous state. Please refer to Figure 3-Figure 5 , Figure 3 : is a curve diagram of transformer secondary voltage and inductor current provided in an embodiment of the present application, Figure 4 is a full-bridge rectifier circuit of a first moment mode provided in 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 mode of t1-t2, 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 is 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 5The direction of the arrow in the figure. At t1-t2, the voltage across the transformer is 0V, and 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 t2, the energy transfer phase begins, and the transformer voltage changes from zero to Vs; the third diode D2 and the fourth diode D3 are turned on, and the second diode D1 and the fifth diode D4 are turned off. VD2=0V, VD1=Vs+VD2=Vs. At this time, the voltage stress of the second diode D1 is the highest.

[0036] Among them, see Figure 6-Figure 8 , Figure 6 is another curve diagram of transformer secondary voltage and inductor current provided in an embodiment of the present application, Figure 7 A full-bridge rectifier circuit of the third moment mode provided in 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 mode at time t3, the current of 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 mode diagram at time t4. At this time, the voltage stress of 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 is transferred to the output capacitor through the first inductor L1, VD1 gradually decreases to Vs, VD2 gradually decreases to 0V, and the third diode D2 is turned on to enter the energy transfer stage. It can be seen that when the current of the first inductor L1 is continuous, the maximum voltage stress of the output diode is Vs, and when the current of the first inductor L1 is intermittent, the voltage stress of the output diode reaches Vs / 2+Vo. Usually, Vs=Vo / 0.9. When the current of the first inductor L1 is continuous, the maximum voltage stress of the output diode is Vs=1.11Vo. When the inductor current is intermittent, the voltage stress of the output diode can reach Vs / 2+Vo=1.56Vo, that is, the intermittent state will be about 0.45Vo higher than the continuous state.

[0037] Among them, see Figure 9-11 , Fig. 9 is another curve diagram of transformer secondary voltage and inductor current provided in an embodiment of the present application, Fig.10 Another diode voltage stress improvement circuit provided in an embodiment of the present application is Fig.11 It is another diode voltage stress improvement circuit provided in an embodiment of the present application. After the full-bridge rectifier circuit introduces a current sampling circuit, a comparison circuit and a 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 intermittent, in the mode at time t2, that is, the mode at the third time, the current flow direction of the diode voltage stress improvement circuit is Fig.10 In the direction of the arrow in the figure, at the mode at time t3, i.e. the fourth mode, the current flow direction of the diode voltage stress improvement circuit is Fig.11The direction of the arrow in. At t1-t2, the current of the first inductor L1 is in the continuous stage, and 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, and VD1=VD2=VD3=VD4=0V. At 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 result is 1, and the first switch tube Q1 is turned on. The output capacitor charges the parasitic capacitance of the output diode through the first switch tube Q1 and the first diode D5, as shown in the modal diagram at t2. Since the charging circuit has no inductive devices and has a small impedance, the parasitic capacitance voltage of a single output diode is charged to half of the output voltage in a very short time. In steady state, the voltage VD1=VD2=VD3=VD4=Vo / 2. At t3-t4: the negative half-cycle energy transfer begins, and the secondary winding charges VD1 through VD2, as shown in the modal diagram at t3. Since Vs>Vo, VD2 can gradually drop from Vo / 2 to 0V, and the third diode D2 is turned on. After the third diode D2 is turned on, the voltage across the second diode D1 is equal to the secondary winding voltage, and eventually the secondary voltage rises to Vs, and the voltage across the second diode D1 also rises to Vs. It can be seen that when the differential-mode inductor current is discontinuous, the output diode voltage stress is Vs at most. When the differential-mode inductor current is continuous, the output diode voltage stress is also Vs at most. The output diode voltage stress is consistent when the current of the first inductor L1 is in the discontinuous state and the continuous state. In fact, compared with 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, which is reduced by 0.45Vo, and greatly reduces the voltage stress of the output diode when the current of the first inductor L1 is in the intermittent state. Therefore, the output diode can choose a diode with a lower withstand voltage. The forward voltage drop VF of the diode with a lower withstand voltage is smaller, the loss is lower, and the overall efficiency of the power supply will be higher.

[0038] 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 a 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, and the forward voltage drop is relatively small, and the loss is relatively small, which is beneficial to improve the overall efficiency of the power supply.

[0039] See also Fig.12, Fig.12 It is a schematic diagram of the architecture of a conversion circuit provided in an embodiment of the present application, wherein the conversion circuit includes a voltage source Vi, an input capacitor Ci, a primary 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 conversion circuit 70, and the diode voltage stress improvement circuit 1 is connected to the transformer 60.

[0040] See also Fig.13 , Fig.13 is a circuit diagram of a voltage source, an input capacitor and a primary conversion circuit provided in an embodiment of the present application, wherein the primary 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; 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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; 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 fully charged, the current sampling result of the shunt is a negative value; 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.

[0045] 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; 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.

[0046] 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.

[0047] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0048] In the several embodiments provided in the present application, it should be understood that the disclosed device can be implemented in other ways. For example, the device embodiments described above are only schematic, such as the division of the above-mentioned units, which is only a logical function division. There may be other division methods in actual implementation, 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.

[0049] The units described above as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0050] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0051] 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 prior art, 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, including a number of instructions to enable 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, disk or optical disk and other media that can store program codes.

[0052] A person of ordinary skill in the art can 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 can include: a flash drive, a read-only memory, a random access memory, a magnetic disk or an optical disk, etc.

[0053] The embodiments of the present application are introduced in detail above. Specific examples are used in this article 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 general technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method 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 the output rectifier circuit is respectively connected to a transformer, a current sampling circuit, a filter circuit and a short circuit; The current sampling circuit is connected to the comparison circuit and the output capacitor respectively; 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, and 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; The comparison circuit is connected to the short circuit, and the comparison circuit is grounded; 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; The output capacitor is used to charge the diode in the output rectifier circuit through the short circuit when the inductor current of the filter circuit is in a discontinuous state.

2. The diode voltage stress improvement circuit according to claim 1, characterized in that: The short circuit includes a first diode and a first switch tube; One end of the first diode is respectively connected to the filter circuit and the output rectifier circuit, 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 respectively connected to the filter circuit and one end of the output capacitor, and the third end of the first switch tube is connected to the comparison circuit.

3. The diode voltage stress improvement circuit according to claim 2, characterized in that: The filter circuit includes a first inductor; One end of the first inductor is respectively connected to the output rectifier circuit and one end of the first diode, and the other end of the first inductor is respectively connected to the second end of the first switch tube and one end of the output capacitor.

4. The diode voltage stress improvement circuit according to claim 3, characterized in that: 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 third terminal of the first switch tube.

5. The diode voltage stress improvement circuit according to claim 4, characterized in that: The current sampling circuit comprises 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.

6. The diode voltage stress improvement circuit according to claim 5, 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 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.

7. The diode voltage stress improvement circuit according to claim 6, 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.

8. The diode voltage stress improvement circuit according to claim 3, characterized in that: 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.

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

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