Switching power supply with coupled buck conversion processing stage
By introducing a coupled buck conversion processing stage into the switching power supply, the problem of low insulation of the power supply under high input voltage is solved, achieving lower isolation voltage and simplified insulation requirements.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PHOENIX CONTACT GMBH & CO KG
- Filing Date
- 2019-11-18
- Publication Date
- 2026-04-10
AI Technical Summary
Existing power supplies struggle to meet low insulation requirements under high input voltage conditions, especially in terms of electrical safety standards within isolated areas.
Two coupled buck converter processing stages are introduced into the switching power supply. By connecting buck converters to the positive and negative input voltages respectively and winding their coils on the same magnetic core, the two buck converters are jointly controlled by a control signal to achieve symmetrical voltage drop and reduce isolation voltage.
It effectively reduces the isolation voltage over the isolation distance, and can meet electrical safety specifications regardless of the grounding method, simplifying insulation requirements.
Smart Images
Figure CN121841102A_ABST
Abstract
Description
[0001] This application is a divisional application of patent application No. 201980080601.9, filed on November 18, 2019, entitled "Switching power supply with coupled step-down conversion processing stages". TECHNICAL FIELD
[0002] The present invention relates to an electrically isolated switching power supply with two coupled step-down conversion processing stages for reducing the insulation requirements between input voltage and output voltage. BACKGROUND
[0003] In safety-isolated areas, power supplies have the task of adapting the voltage to the respective application. Depending on the different applications, the input voltage in the hazardous area can be above a certain voltage limit. For example, the supply voltage of an industrial control cabinet is generally a hazardous 120 V AC or 230 V AC touch voltage or a low voltage of up to 1000 V AC / 1500 V DC. For this reason, one must comply with the electrical safety requirements in terms of insulation distance, insulating material or contact protection. The electrical consumers in the control cabinet, such as controllers (SPS), sensors or actuators, are supplied with a safe extra-low voltage (SELV) that allows touching, so that no special requirements have to be carried out in terms of electrical safety of the electrical consumer or its wiring.
[0004] The power supply therefore also has the task of separating the hazardous touch input voltage from the usable output voltage.
[0005] For this purpose, there are normative requirements for the minimum electrical clearance and creepage distance (LuK) in the power supply for the respective application in order to achieve the separation of the hazardous touch input voltage from the usable output voltage. For example, the basic requirements for electrical clearance and creepage distance are specified in the IEC-60664 series of standards "Insulation Coordination for Electrical Devices in Low-Voltage Systems". In addition, there are also specific product standards depending on the specific product and application, such as: IEC-62109 "Safety of inverters for use with photovoltaic power systems"; IEC-60950 "Information technology equipment - Safety"; IEC-61010 "Safety requirements for electrical measuring, control and laboratory equipment"; IEC-62368 "Audio / video, information and communication technology equipment - Part 1 : general requirements".
[0006] Figure 1 Basic circuit diagram for the isolation of the electrically isolated power supply 100, which shows the isolation voltage V IS1 , V IS2 , V IS3 , with closed switches S1 and S2 and input voltage V IN and output voltage VOUT One-point grounding each. The highest voltage is generally the isolated distance I S1 … I S5 The maximum input voltage V IN measured later
[0007] Figure 2 is the basic circuit diagram of the isolation method of the electrically isolated switching power supply 200. The isolation requirement mainly comes from the transformer Tr1 and the feedback element, i.e. the optocoupler OC1 for output variable error control. The output variable can be the output voltage or the output current, and can also be multiple output voltages if necessary.
[0008] In the figure, the rectification and smoothing processing of the switching power supply on the input side using an alternating voltage source is not shown, and only the DC / DC converter, which is actually an electrically isolated converter, is shown. The basic circuit diagram is independent of the function of the DC / DC converter. The DC / DC converter can be realized according to known basic circuit principles. For example, it can use a flyback converter, a forward converter, a half-bridge converter, a full-bridge converter, or a resonant converter. In the case of high input voltage, the basic circuit concept of a double-transistor converter or a series form of the above-mentioned concept converter is also used. The control principle of the circuit breaker S3 can be, for example, hard switching using pulse width modulation (PWM), or resonant switching using frequency modulation (PFM).
[0009] Likewise, regardless of the technology used, the power switch S3 can be implemented as a power switch that can be turned on and off as needed, and can use, for example, MOSFET, bipolar transistor, IGBT, GAN-FET, or SiC-FET.
[0010] Figure 3a and Figure 3b is the basic circuit diagram of the reference potential of the primary side control element and the optocoupler OC1 of the electrically isolated switching power supply 300a, 300b. The primary side control element and the feedback optocoupler OC1 of the circuit breaker S3 generally take the negative input voltage -V IN as the reference potential. In this way, the power switch S3 can be directly controlled.
[0011] In practice, the optocoupler OC1 can be implemented as an optocoupler as well as a magnetic coupler.
[0012] The above isolation voltage comes from the maximum input voltage. For example, if the supply voltage is a direct current voltage, it is grounded to +V IN or -V IN . If the output voltage is a low voltage, either +V OUT or -V OUT can be considered as ground. The isolated voltage is V IS1 and VIS2 the isolation distance of the transformer Tr1 when -V IN is applied to the ground. Since the optocoupler OC1 is most relevant to -V IN , the highest isolation voltage V IN will occur when +V IS3 is considered as ground. The isolation voltage V IS2 will be much lower than the input voltage V IN , but depending on the principle of the switching power supply, the peak value can be much higher than V IN .
[0013] When the switching power supply is to be used as a general power supply, it can be grounded both to the positive input voltage and to the negative input voltage. The various grounding options that exist place very high demands on the isolation conditions on the isolation distance. SUMMARY
[0014] It is therefore an object of the present invention to provide a switching power supply with lower insulation requirements.
[0015] By extending the basic circuit concept, the insulation requirements on the isolation distance can be reduced substantially. Irrespective of how the input voltage and the output voltage are grounded, the isolation voltage of the components on the isolation distance should be reduced.
[0016] This object is achieved by having the features according to the independent claims. Various advantageous embodiments are the technical solutions of the dependent claims, the description and the drawings.
[0017] The basic concept of the invention is that a step-down converter is connected upstream of the electrical isolated DC / DC converter at both the positive input voltage and the negative input voltage. The voltage drops V 11 and V 12 occur on the two step-down conversion processing stages (see Figure 4 ), so that the isolation voltage on the isolation distance V IS1 is reduced irrespective of the grounding. By combining or coupling the coils of the two step-down conversion processing stages with each other and winding them on a ferrite core, the advantage is achieved that the two step-down converters are automatically symmetrical and that the tolerances between the coils become insignificant. Therefore, the breakers of the two step-down converters must be controlled simultaneously.
[0018] According to a first aspect, the above object is achieved by a switching power supply comprising an input circuit supplied by an input voltage, an output circuit connected to the input circuit and configured to provide an output voltage, and an isolation element arranged between the input circuit and the output circuit, the isolation element being designed to comply with predetermined safety requirements related to the isolation between the input voltage and the output voltage, wherein the input circuit comprises two coupled step-down conversion stages, a first step-down conversion stage at a positive input voltage and a second step-down conversion stage at a negative input voltage being connected upstream of the isolation element.
[0019] The switching power supply achieves the technical advantage that the voltage drops occurring in the two step-down conversion stages cause a reduction in the isolation voltage over the isolation distance, regardless of the grounding.
[0020] In an advantageous embodiment of the switching power supply, the two step-down conversion stages are configured to cause a voltage drop of the input voltage, thereby reducing the isolation voltage of the isolation element.
[0021] In this way, the switching power supply achieves the technical advantage that the specified safety requirements related to the isolation between the input voltage and the output voltage can be fulfilled more easily, i.e. the requirements on the isolation element can be reduced.
[0022] In an advantageous embodiment of the switching power supply, each of the two step-down conversion stages comprises a coil, the two coils being wound on the same magnetic core.
[0023] In this way, the switching power supply achieves the technical advantage that the two step-down conversion stages are automatically symmetrical and that tolerances between the coils become negligible.
[0024] In an advantageous embodiment of the switching power supply, each of the two step-down conversion stages comprises a power switch, a freewheeling diode and a coil coupled via the same magnetic core. The freewheeling diode can also be implemented as a power switch.
[0025] The similarity in the structure of the two step-down conversion stages achieves the technical advantage that the voltage drops occurring in the two step-down conversion stages are identical and that the insulation requirements of the isolation element can always be reduced by a corresponding amount.
[0026] In an advantageous embodiment of the switching power supply, the two step-down conversion stages can be controlled jointly by a control signal.
[0027] The joint control of the two step-down conversion stages achieves the technical advantage that the voltage drops occurring in the two step-down conversion stages are identical and that the insulation requirements of the isolation element can always be reduced by a corresponding amount.
[0028] In an advantageous embodiment of the switching power supply, the input circuit comprises a pulse emitter or driver circuit for adjusting the control signals of the two step-down conversion stages to the reference potential of the two power switches.
[0029] In an advantageous embodiment of the switching power supply, the input circuit comprises a control circuit for generating the control signals, the reference potential of the control circuit being connected to the central tap between the two step-down conversion stages.
[0030] In this way, the technical advantage is achieved that the input voltage of the control circuit is halved, that is, the isolation voltage is reduced by approximately half, regardless of the grounding.
[0031] In an advantageous embodiment of the switching power supply, the two step-down conversion stages are connected to each other at the input side by means of two input capacitors connected in series, the central tap of the two input capacitors constituting the central tap of the two step-down conversion stages.
[0032] The input voltage is halved by means of the step-down converter, wherein the capacitors smooth the alternating component.
[0033] In an advantageous embodiment of the switching power supply, the two input capacitors are connected in series between the positive input voltage and the negative input voltage.
[0034] In this way, the technical advantage is achieved that the two input capacitors function as a voltage divider, the center tap being easily accessible for manipulation.
[0035] In an advantageous embodiment of the switching power supply, the two step-down conversion stages are connected to each other at the output side by means of a single output capacitor.
[0036] In this way, the technical advantage is achieved that the step-down conversion stages are easier to implement since the output side does not require a center tap.
[0037] In an advantageous embodiment of the switching power supply, the galvanic isolation element comprises a transformer which can be controlled by the control circuit via the power switches.
[0038] The technical advantage achieved by the control circuit with the reference potential connected to the center tap between the two step-down conversion stages controlling the transformer is that the isolation voltage of the transformer is reduced to half the positive input voltage when grounded to the positive input voltage.
[0039] In an advantageous embodiment of the switching power supply, the input circuit comprises a transformer connected between the control circuit and the power switches, the transformer electrically isolating the control circuit from the power switches.
[0040] The control signals are adjusted by the transformer to the reference potential of the breakers.
[0041] In an advantageous embodiment of the switching power supply, the galvanic isolation element comprises a feedback element for regulating the input circuit, in particular an opto-coupler or a magnetic coupler. The opto-coupler is controlled by the secondary side regulator 202 (see Fig. 2). Figure 2
[0042] The output of the feedback element in the primary side controller circuit and its reference potential are connected to the center tap between the two buck conversion stages. In this way, the technical advantage is achieved that the isolation voltage of the feedback element is reduced by approximately half.
[0043] In an advantageous embodiment of the switching power supply, the switching power supply is grounded to a positive input voltage or to a negative input voltage.
[0044] According to a second aspect, the invention relates to a method for reducing the insulation requirements of a switching power supply, the switching power supply comprising an input circuit supplied by an input voltage, an output circuit connected to the input circuit and for providing an output voltage, and a galvanic isolation element arranged between the input circuit and the output circuit, the galvanic isolation element being designed to comply with preset safety requirements related to the isolation between the input voltage and the output voltage, the method comprising the step of switching two coupled buck conversion stages in the input circuit of the switching power supply, wherein a first buck conversion stage at a positive input voltage and a second buck conversion stage at a negative input voltage are connected upstream of the galvanic isolation element.
[0045] The technical advantage achieved by the method is that the voltage drops occurring in the two buck conversion stages cause a reduction in the isolation voltage over the isolation distance, i.e. the isolation voltage of the galvanic isolation element, regardless of the grounding.
[0046] According to a third aspect, the above object is achieved by a computer program having a program code for performing the above method when the program code is executed by a computer. The power supply control can be implemented both in analog and in digital form. BRIEF DESCRIPTION OF DRAWINGS
[0047] In the following, further exemplary embodiments are described with reference to the accompanying drawings. In the drawings:
[0048] Figure 1 Basic circuit diagram for the insulation of an electrically isolated power supply 100;
[0049] Figure 2 Basic circuit diagram for the insulation of an electrically isolated switching power supply 200;
[0050] Figure 3a / Figure 3b / Figure 3c Reference potential circuit for primary side controller and optocoupler OC1 in electrically isolated switching power supply 300a, 300b and buck converter 300c
[0051] Figure 4 Basic circuit diagram for switching power supply 400 with lower isolation requirements according to an embodiment
[0052] Figure 5 Basic circuit diagram for switching power supply 500 with reduced optocoupler voltage load by adjusting the primary side controller reference potential according to an embodiment
[0053] Figure 6 Basic circuit diagram for switching power supply 600 with coupled buck conversion processing stage according to an embodiment
[0054] Figure 7 Schematic diagram for method 700 to reduce isolation requirements for switching power supplies according to an embodiment DETAILED DESCRIPTION
[0055] The switching power supplies described below include a buck converter with a coupled buck conversion processing stage.
[0056] Figure 3c A buck converter, hereinafter "buck converter" or "buck regulator", is a switched-mode DC / DC converter with an output voltage V OUT that is always lower than the input voltage V IN .
[0057] The buck converter includes a switch S, which is connected in series with a diode D between a positive input voltage +V IN and a negative input voltage -V IN . Furthermore, the switch S is connected in series with a coil L between the positive input voltage +V IN and a positive output voltage +V OUT . A capacitor C is connected between the positive output voltage +V OUT and a negative output voltage -V OUT . The switch S, typically a transistor, is regularly turned on and off by a controller, typically several hundred to several million times per second, to transfer electrical energy from the voltage source V IN connected on the input side to a load connected on the output side. The buck converter includes two energy storage elements, namely the coil L and the capacitor C, which enable power supply when the switch is off. The inductance of the coil L isolates the higher input voltage from the load. The output variable can be set by controlling the on and off times of the switch S. This control is typically performed by a regulator to maintain the output voltage or current at a target value.
[0058] When the switch is on, the load current flows through the coil and the consumer, while the diode D is off. When the switch is off, the energy stored in the coil is dissipated: the current continues to flow through the consumer, while at the same time, the current also flows through the diode D, and the current flows out of the capacitor C.
[0059] The coil L and the capacitor C form a second-order low-pass filter. By filtering the DC component from the square-wave voltage, the voltage reduction is effectively achieved. The voltage of the DC component that is left can be set by means of the pulse duty factor.
[0060] Figure 4 Basic circuit diagram of a switch mode power supply 400 according to an embodiment with lower insulation requirements.
[0061] The switch mode power supply 400 comprises an input circuit 401 for supplying an input voltage V IN , an output circuit 402 connected to the input circuit 401 for supplying an output voltage V OUT , and an isolation element 103 arranged between the input circuit 401 and the output circuit 402, which is designed to comply with preset safety requirements related to the isolation between the input voltage V IN and the output voltage V OUT . The input circuit 401 comprises two coupled voltage reduction conversion stages 403, wherein a first voltage reduction conversion stage 404 at a positive input voltage +V IN and a second voltage reduction conversion stage 405 at a negative input voltage -V IN are connected upstream of the isolation element 103.
[0062] The two voltage reduction conversion stages 403 cause a voltage reduction of the input voltage V IN , thereby reducing the isolation voltage V IS1 , V IS2 , V IS3 over the isolation element 103.
[0063] The isolation element 103 comprises a transformer Trl, which decouples the power supply path 406 of the input circuit 401 from the output circuit 402 of the switch mode power supply 400. The isolation voltage V IS1 and V IS2 is reduced over the transformer Trl between the input circuit 401 and the output circuit 402. The isolation element 103 further comprises an opto-coupler OC1, which decouples a controller 407 of the input circuit 401 from the output circuit 402 of the switch mode power supply 400. The isolation voltage V IS3 between the input circuit 401 and the output circuit 402 is reduced over the opto-coupler OC1.
[0064] The voltage reductions V11 and V 12 such that the isolation voltage on the isolation distance V IS1 is reduced by approximately half, regardless of the grounding mode. By combining or coupling the coils of the two step-down conversion stages 404, 405 with each other and winding them on a ferrite core, the advantage is achieved that the two step-down conversion stages 404, 405 automatically achieve symmetry and that tolerances between the coils become insignificant. In order to achieve this, it is necessary to cause the power switches of the two step-down converters 404, 405 to be activated simultaneously.
[0065] The reference potential of the controller 407 of the input circuit 401 is connected to the center tap 409 between the two step-down conversion stages 404, 405. In this way, the isolation voltage V IS3 is halved, so that the input voltage is reduced by approximately half V IN / 2.
[0066] Figure 5 Basic circuit diagram of a switching power supply 500 according to an embodiment for reducing the voltage load of the optocoupler by adjusting the reference potential of the primary-side controller. The two step-down conversion stages within the switching power supply 500 are not shown in the diagram, which is used only to simplify the explanation of the principle of the adjustment of the reference potential of the primary-side controller.
[0067] The controller of the input circuit 501 is connected to the midpoint 509 between the two step-down conversion stages, which corresponds to the center tap of the two input capacitors Cll and C12, and not to the negative input voltage potential -V IN , so that the input voltage V IN is halved to V IN / 2, and the isolation voltage V IS3 is reduced by approximately half, regardless of the grounding mode.
[0068] Figure 6 Basic circuit diagram of a switching power supply 600 according to an embodiment with coupled step-down conversion stages.
[0069] The switching power supply 600 comprises an input circuit 601 supplied by an input voltage V IN , an output circuit 602 connected to the input circuit 601 and for providing an output voltage V OUT , and a galvanic isolation element 103 arranged between the input circuit 601 and the output circuit 602, which is designed to comply with the preset safety requirements related to the isolation between the input voltage V IN and the output voltage VO UT . The galvanic isolation element 103 corresponds to the combination Figure 4The input circuit 601 comprises two coupled step-down conversion stages 603, wherein a first step-down conversion stage at the positive input voltage +V IN and a second step-down conversion stage at the negative input voltage -V IN are coupled to the DC blocking element 103 upstream.
[0070] The two step-down conversion stages cause a voltage drop of the input voltage V IN and thus a reduction of the isolation voltage V IS1 , V IS2 , V IS3 .
[0071] The two step-down conversion stages 603 each comprise a winding L11, which windings are wound on the same magnetic core. The two step-down conversion stages 603 each comprise a power switch S11, S12, a freewheeling diode D11, D12 and the winding L11, which is coupled due to being wound on the same magnetic core. The two step-down conversion stages 603 are jointly controllable by means of a control signal 604. The input circuit 601 comprises a pulse transformer Tr11 or, as an alternative, a drive circuit (not shown) for adjusting the control signal 604 of the two step-down conversion stages 603 to the reference potential of the two power switches S11, S12.
[0072] The input circuit 601 comprises a control circuit 201 for generating the control signal 604. The reference potential 605 of the control circuit 201 is connected to the center tap 606 between the two step-down conversion stages 603. The two step-down conversion stages 603 are connected to one another on the input side via two series-connected input capacitors C11, C12, the center tap 606 of which constitutes the center tap 606 between the two step-down conversion stages 603. The two input capacitors C11, C12 are connected in series between the positive input voltage +V IN and the negative input voltage -V IN . Furthermore, the two step-down conversion stages 603 are connected to one another on the output side via a single output capacitor C13.
[0073] The transformer Tr1 of the DC blocking element 103 can be controlled by means of the control circuit 201 via a circuit breaker S3.
[0074] The input circuit 601 comprises a transformer Tr2 connected between the control circuit 201 and the power switch S3 or a drive stage (not shown) for adjusting the control circuit 201 to the reference potential of the power switch S3.
[0075] The DC blocking element 103 further comprises a feedback element OC1 for adjusting the input circuit 601, which element can be embodied as an opto-coupler OC1 (as shown in Figure 6 ) or a magnetic coupler.Figure 6 (Not shown). This feedback element can be controlled by the adjustment element 202 on the secondary side.
[0076] The 600 switching power supply can be grounded to the positive input voltage +V. IN Or negative input voltage -V IN .
[0077] Figure 6 The diagram illustrates an embodiment of a switching power supply 600, which includes two coupled buck converter stages 603 upstream. Each buck converter stage 603 consists of a circuit breaker S11 or S12 that can be switched on and off as needed, a freewheeling diode D11 or D12, and a coupling coil L11. The freewheeling diode can also be any circuit breaker capable of switching on and off. The output coil of the buck converter 603 is wound on a magnetic core. The buck converter stage 603 can also be signal-activated. A control signal 604 can be adjusted via a pulse transformer Tr11 to the reference potentials of the two power switches S11 and S12. Alternatively, it can be activated via a drive circuit (…). Figure 6 Adjustments are made for (not shown).
[0078] The shared coil and controller ensure that the voltage drops V11 and V12 on the two buck conversion processing stages 603 are the same, and that the insulation requirement V of transformer Tr1 can always be reduced by either voltage drop V11 or V12. IS1 and V IS2 The voltage drop mentioned here depends on the grounding method on the input side. This also reduces the voltage load, especially the voltage load of the power semiconductor devices in the downstream switching power supply.
[0079] Grounded to +V on the input side IN When the primary-side controller 201 or the controller is normally connected to -V IN At that time, the isolation voltage V of the feedback element or optocoupler OC1 IS3 Same as the maximum input voltage VIN. This is achieved by transforming the reference voltage of the primary-side controller 201 to the voltage V at the center tap 606 between the two buck converters 603. IN / 2, grounded at +V IN In this case, the isolation voltage V IS3 Divide into V IN / 2.
[0080] In practice, the optocoupler OC1 can be implemented as both an optocoupler and a magnetic coupler.
[0081] exist Figure 6 In the case of switching power supply 600, the two buck converter circuits 603 require only one control signal 604, which can be output to power switches S11 and S12, for example, via pulse transformer Tr11 with two output windings.
[0082] One advantage of the switching power supply 600 is that the isolation voltage of the downstream galvanic isolation element 103 is reduced.
[0083] The V IN / 2 at the midpoint 606 of the two buck circuits (buck conversion processing stages 603) can be used to reduce the isolation voltage, in particular the isolation voltage of the regulator and the feedback optocoupler OC1.
[0084] Another advantage is that only one capacitor C13 is used on the output side, instead of two capacitors.
[0085] Furthermore, the present application has a greater tolerance when there is a certain degree of difference in the switching time of the semiconductor switches. For example, if the turn-on time of the switch S11 is earlier, then the current flows through the two coils L11, C13 or Tr1, D12 and C12 to the mains connection. According to L = N2x AL, the multiplication of the number of turns N of the coil will cause the inductance to increase in a quadratic manner. When using the same capacitor, the time constant t = LxC becomes four times.
[0086] The present application is particularly suitable for switching power supplies with a high input voltage (e.g. 1500 V DC) and a high insulation requirement due to the undefined grounding.
[0087] Figure 7 Schematic diagram of a method 700 for reducing the insulation requirement of a switching power supply according to an embodiment.
[0088] As described above in connection with Figures 4 to 6 the switching power supply can be the switching power supply 400, 500, 600. In particular, the switching power supply comprises an input circuit 401 supplied with an input voltage V IN an output circuit 402 connected to the input circuit 401 and configured to provide an output voltage V OUT and a galvanic isolation element 103 arranged between the input circuit 401 and the output circuit 402, the galvanic isolation element 103 being designed to comply with a predetermined safety requirement related to the isolation between the input voltage V IN and the output voltage V OUT .
[0089] The method 700 comprises the step of switching 701 two coupled buck conversion processing stages 403 in the input circuit 401 of the switching power supply 400, 500, 600, wherein a first buck conversion processing stage 404 at a positive input voltage +V IN and a second buck conversion processing stage 405 at a negative input voltage -V IN are connected upstream of the galvanic isolation element 103.
Claims
1. A switching power supply (400, 500, 600), characterized in that, include: From the input voltage (V) IN ) Input circuit for power supply (401); Connected to the input circuit and used to provide the output voltage (V) OUT The output circuit (402); and A DC blocking element (103) is disposed between the input circuit (401) and the output circuit (402), wherein the DC blocking element (103) is designed to comply with the input voltage (V). IN ) and the output voltage (V OUT Pre-defined security requirements related to isolation between them. The input circuit (401) includes two coupled buck converter stages (403), wherein the positive input voltage (+V) IN The first buck converter stage (404) at the negative input voltage (-V) and the negative input voltage (-V) IN The second step-down conversion processing stage (405) at the location is connected upstream of the DC blocking element (103).
2. The switching power supply (400, 500, 600) according to claim 1, characterized in that, The two buck conversion processing stages (403) are used to make the input voltage (V IN A voltage drop occurs, thereby reducing the isolation voltage (V) of the DC blocking element (103). IS1 V IS2 V IS3 ).
3. The switching power supply (600) according to claim 1 or 2, characterized in that, Each of the two buck conversion processing stages (603) includes a coil (L11), wherein the two coils are wound on the same magnetic core.
4. The switching power supply (600) according to claim 3, characterized in that, Each of the two buck conversion processing stages (603) includes a power switch (S11, S12), a freewheeling diode (D11, D12), and a coil (L11) coupled to the same magnetic core.
5. The switching power supply (600) according to claim 4, characterized in that, The two buck conversion processing stages (603) can be jointly controlled by the control signal (604).
6. The switching power supply (600) according to claim 5, characterized in that, The input circuit (601) includes a pulse transformer (Tr11) or drive circuit for adjusting the control signal (604) of the two buck conversion processing stages (603) to the reference potential of the two power switches (S11, S12).
7. The switching power supply (600) according to claim 5 or 6, characterized in that, The input circuit (601) includes a control circuit (201) for generating the control signal (604). The reference potential (605) of the control circuit (201) is connected to the central tap (606) between the two buck conversion processing stages (603).
8. The switching power supply (600) according to claim 7, characterized in that, The two buck converter stages (603) are coupled to each other on the input side by two input capacitors (C11, C12) connected in series, wherein the central tap (606) of the two input capacitors constitutes the central tap (606) of the two buck converter stages (603).
9. The switching power supply (600) according to claim 8, characterized in that, The two input capacitors (C11, C12) are at the positive input voltage (+V) IN ) and the negative input voltage (-V IN ) are connected in series.
10. The switching power supply (600) according to any one of claims 7 to 9, characterized in that, The two buck conversion processing stages (603) are coupled to each other on the output side via a single output capacitor (C13).
11. The switching power supply (600) according to any one of claims 7 to 10, characterized in that, The DC blocking element (103) includes a transformer (Tr1) that can be controlled by the control circuit (201) via a power switch (S3).
12. The switching power supply (600) according to claim 11, characterized in that, The input circuit (601) includes a transformer (Tr2) connected between the control circuit (201) and the power switch (S3), wherein the transformer electrically isolates the control circuit (201) from the power switch (S3).
13. The switching power supply (600) according to any one of claims 7 to 12, characterized in that, The DC blocking element (103) includes a feedback element (OC1) for regulating the input circuit (601), particularly an optocoupler (OC1) or a magnetic coupler that can be controlled by a secondary-side regulator (202).
14. The switching power supply (400, 500, 600) according to any one of the preceding claims, characterized in that, The switching power supply is grounded to the positive input voltage (+V). IN ) or the negative input voltage (-V IN ).
15. A method (700) for reducing the insulation requirements of switching power supplies (400, 500, 600), characterized in that, The switching power supply includes: a power supply consisting of an input voltage (V) IN An input circuit (401) powered by the input circuit; connected to the input circuit and used to provide an output voltage (V OUT The output circuit (402) of the input circuit (401) and the output circuit (402); and a DC blocking element (103) disposed between the input circuit (401) and the output circuit (402), wherein the DC blocking element (103) is designed to comply with the input voltage (V). IN ) and the output voltage (V OUT The method includes the following steps: (The method addresses the pre-defined security requirements related to isolation between the two entities.) The two phase-coupled buck conversion processing stages (403) within the input circuit (401) of the switching power supply (400, 500, 600) are switched (701), wherein the positive input voltage (+V) IN The first buck converter stage (404) at the negative input voltage (-V) and the negative input voltage (-V) IN The second step-down conversion processing stage (405) at the location is connected upstream of the DC blocking element (103).