Multi-isolation output expansion circuit of auto-excitation type Buck converter and auto-excitation type Buck converter

Abstract

The invention relates to the technical field of power electronics, and discloses a multi-isolation output expansion circuit of an auto-excitation type Buck converter and the auto-excitation type Buck converter, and the multi-isolation output expansion circuit comprises a first switch tube which is connected in parallel with two ends of a fly-wheel diode; the multi-winding transformer comprises a primary winding, a first secondary winding and a plurality of second secondary windings, the primary winding is configured as an output filter inductor of the self-excited Buck converter, the first secondary winding is configured as a driving winding of the first switching tube, and the second secondary windings are configured as an isolation output end of the self-excited Buck converter; and the first capacitor is configured to form a reverse follow current channel with the first switching tube under the condition that the energy storage of the multi-winding transformer is insufficient, so as to provide energy for the multi-winding transformer. According to the invention, a plurality of isolated output ports are easy to expand, and the voltage of the isolated output ports is stabilized, so that the load regulation rate of the converter is improved.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a multi-isolation output expansion circuit of a self-excited Buck converter and a self-excited Buck converter. Background Art

[0002] A self-excited converter is a switching power supply that does not require an external clock signal and can achieve an oscillation function through the circuit's own components. Its circuit is simple and low-cost, so it is often used in low-power switching power supplies, especially bipolar self-excited buck converters, which are widely used in the field of power electronics.

[0003] In a multi-output system that requires independent regulation, it is often necessary to set up multiple isolated voltage outputs. However, in the relevant technology, the bipolar self-excited Buck converter usually has only one output port. Therefore, the output expansion of the self-excited Buck converter is relatively difficult, and converters with multiple output ports generally have the problem of low load regulation rate, which limits their application in low-power multi-output scenarios. Summary of the invention

[0004] The present application provides a multi-isolated output expansion circuit of a self-excited Buck converter and a self-excited Buck converter, which solves the technical problems that the output expansion of the current self-excited Buck converter is difficult and the load regulation rate is generally low. The present application adopts a multi-winding transformer to replace the output filter inductor of the converter, and provides a reverse freewheeling channel for the primary current of the multi-winding transformer, thereby achieving the technical effect of facilitating the expansion of multiple isolated output ports while stabilizing the voltage of the isolated output ports, thereby optimizing the load regulation rate of the converter.

[0005] In order to achieve the above objectives, the main technical solutions adopted in this application include:

[0006] In a first aspect, an embodiment of the present application provides a multi-isolated output expansion circuit of a self-excited Buck converter, wherein the self-excited Buck converter includes a freewheeling diode, and the multi-isolated output expansion circuit includes:

[0007] A first switch tube, wherein the first switch tube is connected in parallel to two ends of the freewheeling diode;

[0008] A multi-winding transformer, the multi-winding transformer comprising a primary winding, a first secondary winding and a plurality of second secondary windings, wherein the primary winding is configured as an output filter inductor of the self-excited Buck converter, the first secondary winding is configured as a drive winding of the first switch tube, and the second secondary winding is configured as an isolated output terminal of the self-excited Buck converter;

[0009] A first capacitor, wherein the first capacitor is configured to form a reverse freewheeling channel with the first switch tube when the multi-winding transformer has insufficient energy storage, so as to provide energy to the multi-winding transformer.

[0010] The multi-isolated output expansion circuit proposed in the embodiment of the present application expands the single output end of the traditional self-excited Buck converter into a multi-output topology with multiple isolated output ends by connecting the first switch tube in parallel at both ends of the freewheeling diode and using a multi-winding transformer. And the first capacitor and the first switch tube together form a reverse freewheeling channel, using the first secondary winding to drive the conduction and shutdown of the first switch tube, and the other multiple secondary windings provide isolated outputs, so that the first capacitor can be used to achieve energy replenishment when the primary winding energy storage is insufficient, so as to stabilize the output voltage of the self-excited Buck converter, thereby avoiding the risk of output voltage drop caused by insufficient energy storage of the multi-winding transformer T. Therefore, the embodiment of the present application realizes the flexible expansion of multiple isolated output ports through the configuration of the multi-winding transformer, thereby meeting the diversified application requirements, and provides a reverse freewheeling path through the first switch tube, when the primary winding energy storage is insufficient, the isolated output end can be quickly replenished with energy, effectively avoiding voltage fluctuations, greatly improving the system adaptability of the self-excited Buck converter and optimizing the load regulation rate, especially in low-power multi-isolated output applications. It has significant advantages.

[0011] Optionally, in some embodiments of the present application, the first switch tube is an NPN transistor, the collector of the first switch tube is connected to the cathode of the freewheeling diode and the same-name end of the primary winding, the emitter of the first switch tube is connected to the anode of the freewheeling diode and grounded, and the base of the first switch tube is connected to the opposite-name end of the first secondary winding.

[0012] The embodiment of the present application forms a reverse freewheeling channel relative to the conduction current direction of the freewheeling diode through the connection relationship between the first switch tube and the freewheeling diode and the primary winding, so as to utilize the conduction characteristics of the first switch tube to quickly provide a reverse freewheeling path when the multi-winding transformer has insufficient energy storage, thereby achieving stable support for the isolated output terminal voltage. In addition, the embodiment of the present application utilizes the first secondary winding of the multi-winding transformer as the drive winding of the first switch tube, which simplifies the design of the drive circuit, avoids additional control circuits, improves the overall system efficiency and reduces hardware costs.

[0013] Optionally, in some embodiments of the present application, when the multi-winding transformer has insufficient energy storage, the direction of the induced current flowing through the primary winding is from the opposite-name end to the same-name end.

[0014] Optionally, in some embodiments of the present application, the first end of the first capacitor is connected to the opposite end of the primary winding, and the second end of the first capacitor is grounded.

[0015] The embodiment of the present application uses a connection structure between the first capacitor and the primary winding, so that when the energy stored in the primary winding cannot meet the output demand, the energy stored in the first capacitor can be quickly released, thereby effectively avoiding output voltage fluctuations, thereby ensuring the stability of the voltage at the multi-isolated output end, and effectively improving the load regulation rate of the self-excited Buck converter.

[0016] Optionally, in some embodiments of the present application, the isolated output terminal further includes:

[0017] A rectifier diode, wherein an anode of the rectifier diode is connected to a corresponding opposite-name end of the second secondary winding;

[0018] A second capacitor, wherein a first end of the second capacitor is connected to the cathode of the rectifier diode, and a second end of the second capacitor is connected to the corresponding same-name end of the second secondary winding.

[0019] The embodiment of the present application combines the rectification and filtering functions by setting a rectifier diode and a second capacitor at the isolated output end, thereby providing a stable DC voltage for each isolated output end, thereby improving the voltage output quality of the extended isolated output end.

[0020] Optionally, in some embodiments of the present application, the same-name end of the first secondary winding and the same-name end of the second secondary winding are both grounded and isolated from each other.

[0021] Optionally, in some embodiments of the present application, the two ends of the first capacitor are configured as the main output ends of the self-excited Buck converter, and the main loop output voltage of the main output end is determined according to the input voltage and the duty cycle of the main switch tube of the self-excited Buck converter.

[0022] In the embodiment of the present application, the main output end of the self-excited Buck converter is arranged at both ends of the first capacitor, so that the first capacitor not only works in conjunction with the primary winding of the multi-winding transformer to provide a reverse freewheeling path for energy, but also can filter the main output voltage, thereby simplifying the circuit structure while improving the load regulation rate.

[0023] Optionally, in some embodiments of the present application, the output voltage of the isolated output terminal is determined according to the main loop output voltage, the primary-to-secondary winding turns ratio, and the conduction voltage of the rectifier diode in the isolated output terminal.

[0024] In a second aspect, an embodiment of the present application provides a self-excited Buck converter, wherein the self-excited Buck converter comprises:

[0025] Main switch tube;

[0026] Freewheeling diode;

[0027] And the multi-isolation output expansion circuit according to the above embodiment.

[0028] The self-excited Buck converter proposed in the embodiment of the present application expands the single output end of the traditional self-excited Buck converter into a multi-output topology with multiple isolated output ends through a multi-isolated output expansion circuit, and the multi-isolated output expansion circuit also constitutes a reverse freewheeling channel, thereby stabilizing the output voltage of the self-excited Buck converter. Therefore, the embodiment of the present application realizes the flexible expansion of multiple isolated output ports through the configuration of a multi-winding transformer, thereby meeting diverse application requirements, and can quickly replenish energy to the isolated output end, effectively avoiding voltage fluctuations, greatly improving the system adaptability of the self-excited Buck converter and optimizing the load regulation rate, especially in low-power multi-isolated output applications, which has significant advantages.

[0029] Optionally, in some embodiments of the present application, the self-excited Buck converter further includes a drive circuit, and the drive circuit is configured to drive the main switch tube to be turned on and off to supply energy to the multi-winding transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 A schematic diagram of the structure of a multi-isolation output expansion circuit of a self-excited Buck converter proposed in an embodiment of the present application;

[0032] Figure 2 A schematic diagram of the structure of a self-excited Buck converter proposed in one embodiment of the present application;

[0033] Figure 3 A schematic diagram of the structure of a driving circuit proposed in an embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0035] Low-power self-excited Buck converters are widely used in auxiliary power supply design in the field of power electronics due to their simple structure, low cost, wide applicable voltage range, high efficiency, etc. Taking the bipolar self-excited Buck converter as an example, it adopts the basic topology of the main switch tube, freewheeling diode and output filter inductor, and controls the duty cycle of the main switch tube to achieve efficient DC voltage reduction.

[0036] In some application scenarios, more complex power electronic systems usually have multiple voltage output terminals, especially in some power electronic systems that require electrical isolation, such as multi-channel power supply or complex control circuits, the voltage requirements of different isolated output terminals are often different. However, the traditional self-excited Buck converter usually has only a single output port, which limits its application in scenarios that require multiple isolated voltage outputs. Therefore, in the related art, it is generally necessary to set up multiple self-excited Buck converters and corresponding control circuits, which not only increases the complexity of the circuit structure, but also the setting of the output port is relatively fixed, which makes it difficult to flexibly adjust the number of output ports required to adapt to different application scenarios.

[0037] In addition, in some other application scenarios, after expanding multiple isolated output ports, the energy dependence of each isolated output port on the output filter inductor is enhanced, and the efficiency of energy distribution directly affects the load regulation rate, resulting in poor output voltage stability.

[0038] In the embodiment of the present application, a multi-isolated output expansion circuit 100 of a self-excited Buck converter is provided, which is generally applicable to most self-excited Buck converters and can be applied to various low-power scenarios requiring multi-isolated voltage outputs such as power electronic systems and auxiliary power supply fields. Figure 1 As shown, the self-excited Buck converter 10 includes a main switch tube Q1 and a freewheeling diode D1, and the multi-isolated output expansion circuit 100 includes a first switch tube Q2, a multi-winding transformer T and a first capacitor C o1 ;

[0039] The first switch tube Q2 is connected in parallel to both ends of the freewheeling diode D1, and the multi-winding transformer T includes a primary winding n1, a first secondary winding n2, and a plurality of second secondary windings n k (k=2,…,s), wherein the primary winding n1 is configured as the output filter inductor of the self-excited Buck converter, the first secondary winding n2 is configured as the driving winding of the first switch tube Q2, and the second secondary winding n k (k=2,…,s) is configured as the isolated output terminal of the self-excited Buck converter; the first capacitor C o1It is configured to form a reverse freewheeling channel with the first switch tube Q2 to provide energy to the multi-winding transformer T when the multi-winding transformer T has insufficient energy storage.

[0040] The multi-isolated output expansion circuit 100 proposed in the embodiment of the present application uses the primary winding n1 of the multi-winding transformer T to replace the output filter inductor of the converter, and uses the second secondary winding n k (k=2,…,s) realizes the expansion of the isolated output terminal. k The setting method of (k=2,…,s) is simple, and the number of the second secondary windings can be flexibly increased or decreased according to the number of isolated output ports, so that the isolated output ports are easy to expand. In addition, the embodiment of the present application enhances the independence between the isolated output ports through the multi-isolated output expansion circuit 100, utilizes the isolation characteristics of the transformer group, avoids the interference of the abnormality of a single output port to other ports, and effectively improves the anti-interference ability and operation stability of the overall system.

[0041] The multi-isolated output expansion circuit 100 proposed in the embodiment of the present application expands the single output end of the traditional self-excited Buck converter into a multi-output topology structure with multiple isolated output ends by connecting the first switch tube Q2 in parallel at both ends of the freewheeling diode D2 and using a multi-winding transformer T. And the first capacitor C o1 Together with the first switch tube Q2, a reverse freewheeling channel is formed. The first secondary winding n2 is used to drive the first switch tube Q2 to be turned on and off, while the other multiple secondary windings n k (k=2,…,s) provides an isolated output, so that when the energy storage of the primary winding n1 is insufficient, the first capacitor Co1 can be used to supplement energy to stabilize the output voltage of the self-excited Buck converter, thereby avoiding the risk of output voltage drop caused by insufficient energy storage of the multi-winding transformer T. Therefore, the embodiment of the present application realizes the flexible expansion of multiple isolated output ports through the configuration of the multi-winding transformer T, thereby meeting diverse application requirements, and provides a reverse freewheeling path through the first switch tube Q2. When the energy storage of the primary winding n1 is insufficient, the energy of the isolated output terminal can be quickly supplemented, effectively avoiding voltage fluctuations, greatly improving the system adaptability and load regulation rate of the self-excited Buck converter, especially in low-power multi-isolated output applications. It has significant advantages.

[0042] In some embodiments of the present application, Figure 1 As shown, the first switch tube Q2 is an NPN transistor, the collector of the first switch tube Q2 is connected to the cathode of the freewheeling diode D1 and the same-name end of the primary winding n1, the emitter of the first switch tube Q2 is connected to the anode of the freewheeling diode D1 and grounded, and the base of the first switch tube Q2 is connected to the opposite-name end Q of the first secondary winding n2. 2b .

[0043] Furthermore, the base of the first switch tube Q2 and the opposite-name terminal Q 2b A protective resistor R is connected between b .

[0044] The multi-isolated output expansion circuit 100 utilizes the first switch tube Q2 to provide a reverse freewheeling channel for the primary current of the multi-winding transformer T, and the multi-winding transformer T not only plays the role of the output filter inductor of the converter, but is also used to drive the conduction of the first switch tube Q2 to form a reverse freewheeling channel. Therefore, the multi-isolated output expansion circuit 100 proposed in the embodiment of the present application utilizes the coordinated design of the multi-winding transformer T and the first switch tube Q2, and can realize the multi-isolated output function without adding an independent transformer or control device.

[0045] Therefore, the embodiment of the present application forms a reverse freewheeling channel relative to the conduction current direction of the freewheeling diode D1 through the connection relationship between the first switch tube Q2, the freewheeling diode D1 and the primary winding n1, so as to utilize the conduction characteristics of the first switch tube Q2 to quickly provide a reverse freewheeling path when the multi-winding transformer T has insufficient energy storage, thereby achieving stable support for the isolated output voltage.

[0046] In addition, the base of the first switch tube Q2 is connected to the opposite end of the first secondary winding n2. Therefore, the embodiment of the present application uses the first secondary winding n2 of the multi-winding transformer T as the driving winding of the first switch tube Q2, which simplifies the design of the driving circuit, significantly reduces hardware resources and circuit complexity, reduces system costs, and avoids additional control circuits. It can simplify production and maintenance work, thereby improving the overall system efficiency and reducing maintenance costs.

[0047] Specifically, when the main switch Q1 is turned on, the input power supply V in To the primary winding n1 of the multi-winding transformer T and the load R o1 When the main switch Q1 is turned off, the primary winding n1 of the multi-winding transformer T is subjected to a positive voltage on the right and a negative voltage on the left. The primary current I p The direction is from the same-name end to the opposite-name end, the first switch tube Q2 and the secondary diode D k (k=2,…,s) is turned on, and the energy stored in the multi-winding transformer T is transferred to the isolated output end.

[0048] It should be noted that when the primary winding n1 of the multi-winding transformer T has sufficient energy storage, the first switch tube Q2 will still be triggered to turn on by the transformer, but at this time the energy required by the secondary winding is only provided by the primary winding, not by the first capacitor C. o1 supply.

[0049] When the energy stored in the primary winding n1 of the multi-winding transformer T is sufficient to maintain the energy required by the isolated output port, that is, the primary current I p When the direction is from the same-name terminal to the opposite-name terminal, the primary current I p The current is only freewheeling through diode D1.

[0050] In some embodiments of the present application, when the primary winding n1 of the multi-winding transformer T has insufficient energy storage, the primary current I flowing through the primary winding n1 is p Therefore, in the embodiment of the present application, when the energy of the primary winding n1 cannot maintain the energy required by the isolated output port, the energy of the isolated output port will be supplied by the first capacitor C o1 Provided, at this time the primary current I of the multi-winding transformer p After the current drops to zero, the current direction will reverse. At this time, the opposite-name end of the first secondary winding n2 generates a high level to drive the first switch tube Q2 to turn on, thereby forming a reverse freewheeling channel by using the conduction of the first switch tube Q2 to realize the first capacitor C o1 The primary winding n1 is charged, thereby effectively avoiding voltage fluctuation at the isolated output end and improving the load regulation rate.

[0051] Furthermore, in some embodiments of the present application, the same-name end of the first secondary winding n2 and the second secondary winding n k The same-name terminals of (k=3,…,s) are all grounded and isolated from each other.

[0052] In some embodiments of the present application, Figure 1 As shown, the first capacitor C O1 The first end of the capacitor C O1 The second end is grounded.

[0053] In this embodiment of the present application, the first capacitor C O1 The connection structure with the primary winding n1 can be used to store energy through the first capacitor C when the energy stored in the primary winding n1 cannot meet the output demand. O1 The energy storage is quickly released, which effectively avoids output voltage fluctuations, thereby ensuring the stability of the multi-isolation output voltage, thereby effectively improving the load regulation rate of the self-excited Buck converter. O1 At the same time, as a converter output filter capacitor, it can use the energy stored in the filtering process to compensate the energy of the primary winding n1, thereby improving the energy utilization efficiency to a certain extent and helping to improve energy saving.

[0054] Further, in some embodiments of the present application, Figure 1 As shown, the isolated output end also includes a rectifier diode D k(k=2,…,s) and the second capacitor C k (k=2,…,s), where the rectifier diode D k The anode of (k=2,…,s) is connected to the corresponding second secondary winding n k (k=3,…,s) opposite end, the second capacitor C k The first end of (k=2,…,s) is connected to the rectifier diode D k (k=2,…,s) cathode, second capacitor C k The second end of (k=2,…,s) is connected to the corresponding second secondary winding n k (k=3,…,s) with the same name.

[0055] In the embodiment of the present application, a rectifier diode D is arranged at the isolated output end. k (k=2,…,s) and the second capacitor C k (k=2,…,s), the rectification and filtering functions are combined to provide a stable DC voltage for each isolated output terminal, thereby improving the voltage output quality of the extended isolated output terminal.

[0056] Specifically, the rectifier diode D k (k=2,…,s) can effectively block the reverse flow of current and ensure the unidirectionality of energy transmission. The second capacitor C k (k=2,…,s) plays the role of energy storage and voltage fluctuation smoothing, further improving the load regulation rate and stability of the isolated output port.

[0057] In some embodiments of the present application, the first capacitor C O1 The two ends of the self-excited Buck converter are configured as the main output terminals, and the main circuit output voltage V o1 According to the input voltage V in The duty cycle of the main switch tube Q1 determines the output voltage V ok (k=2,…,s) According to the main circuit output voltage V o1 , the primary-to-secondary winding turns ratio and the conduction voltage of the rectifier diode in the isolated output end.

[0058] Specifically, the main circuit output voltage of the main output terminal is determined according to the following formula (1):

[0059] V o1 =DV in Formula (1)

[0060] Where D is the duty cycle of the main switch Q1.

[0061] The output voltage of the isolated output terminal is determined according to the following formula (2):

[0062]

[0063] Where V os is the output voltage of the isolated output terminal, N s is the second secondary winding n s N1 is the number of turns of the primary winding n1, V fs is the rectifier diode D s The on-state voltage.

[0064] Therefore, in the embodiment of the present application, the first capacitor C O1 It not only cooperates with the primary winding n1 of the multi-winding transformer T to provide a reverse freewheeling path for energy, but also can filter the main output voltage, thereby optimizing the load regulation rate and simplifying the circuit structure.

[0065] Accordingly, the embodiment of the present application provides a self-excited Buck converter 10, comprising:

[0066] Main switch tube Q1;

[0067] Freewheeling diode D2;

[0068] And the multi-isolated output expansion circuit 100 according to the above embodiment.

[0069] The specific configuration of each of the above modules and units and further functional description are the same as those of the above corresponding embodiments and will not be repeated here.

[0070] The self-excited Buck converter 10 proposed in the embodiment of the present application expands the single output end of the traditional self-excited Buck converter 10 into a multi-output topology with multiple isolated output ends through the multi-isolated output expansion circuit 100, and the multi-isolated output expansion circuit 100 also constitutes a reverse freewheeling channel, thereby being able to stabilize the output voltage of the self-excited Buck converter 10. Therefore, the embodiment of the present application realizes the flexible expansion of multiple isolated output ports through the configuration of the multi-isolated output expansion circuit 100, thereby meeting diverse application requirements, and can quickly replenish energy to the isolated output end, effectively avoiding voltage fluctuations, greatly improving the system adaptability and load regulation rate of the self-excited Buck converter 10, especially having significant advantages in low-power multi-isolated output applications.

[0071] In some embodiments of the present application, the self-excited multi-winding transformer 10 further includes a driving circuit 200, and the driving circuit 200 is configured to drive the main switch tube Q1 to be turned on and off to supply energy to the multi-winding transformer T. When the main switch tube Q1 is turned on, the primary winding n1 of the multi-winding transformer T is charged, and when the main switch tube Q1 is turned off, the primary winding n1 of the multi-winding transformer T is discharged.

[0072] The multi-isolated output expansion circuit 100 proposed in the embodiment of the present application is universal and can be applied to the output end of a self-excited buck converter to expand the self-excited buck converter into a converter with multiple isolated output ports and good load regulation rate.

[0073] Figure 2 A self-excited buck converter 10 using the multi-isolated output expansion circuit 100 is shown. Figure 3 As shown, the multi-isolation output expansion circuit 100 is replaced Figure 2 The output filter inductor L1 in.

[0074] In some embodiments of the present application, Figure 2 and Figure 3 As shown, the driving circuit 200 includes: a second switch tube Q3, a third capacitor C f1 , the fourth capacitor C f2 And voltage zener diode ZD;

[0075] The base of the second switch tube Q3 is connected to the positive input terminal of the self-excited Buck converter via the first resistor R1, the collector of the second switch tube Q3 is connected to the base of the main switch tube Q1 via the second resistor R2, and the emitter of the second switch tube Q3 is connected to the opposite end of the primary winding n1;

[0076] The third capacitor C f1 The first end of the third capacitor C f1 The second end of is connected to the collector of the first switch tube;

[0077] The fourth capacitor C f2 The first end of the fourth capacitor C is connected to the base of the second switch tube Q3. f2 The second end is connected to the negative input end of the self-excited Buck converter;

[0078] The cathode of the voltage stabilizing diode ZD is connected to the base of the second switch tube Q3, and the anode of the voltage stabilizing diode ZD is connected to the negative input terminal of the self-excited Buck converter.

[0079] Among them, the switching frequency is mainly determined by the transformer excitation inductance and the third capacitor C f1 Determine the excitation inductance and the third capacitor C f1 The larger the value, the lower the switching frequency of the circuit. The voltage regulator diode ZD determines the control accuracy of the output voltage. The third capacitor C f1 Helps determine the operating frequency of the circuit, the fourth capacitor C f2Ensure that the base potential of the second switch tube Q3 rises slowly, improving the stability of the converter circuit. When the primary current of the multi-winding transformer T is reversed, the first switch tube Q2 is responsible for providing a current path to ensure the regulation rate of the isolated output voltage. When the main switch tube Q1 is turned on and the freewheeling diode D1 and the first switch tube Q2 are turned off, Vin provides energy to the load Ro1 and stores part of the energy in the transformer. When the main switch tube Q1 is turned off and D1 and the first switch tube Q2 are turned on, the energy is stored in the multi-winding transformer T and the output capacitor C o1 The energy in the circuit is transferred to the isolated output port.

[0080] exist Figure 2 and Figure 3 In the power-on startup phase of the self-excited buck converter circuit shown, the second switch tube Q3 is turned on through the first resistor R1 and enters the saturation state, and the main switch tube Q1 is turned on through the second resistor R2 and the third resistor R3, the input power starts to supply power to the load, and the output voltage starts to rise slowly. At this time, the primary current of the transformer changes little, and the secondary induced voltage can be ignored. When the output voltage rises to a value exceeding the voltage regulator value U ZD After the Q3 emitter junction voltage drop UQ3be, the voltage zener diode ZD starts to work, and the base voltage of the second switch tube Q3 is clamped. When the output voltage continues to increase, the voltage difference between the base and the emitter of the second switch tube Q3 becomes smaller, and the second switch tube Q3 exits the saturation state. The main switch tube Q1 starts to turn off, and the primary current Ip of the transformer decreases rapidly. The two ends of the primary side of the transformer induce an induced voltage with a negative left and a positive right. The induced voltage is transmitted through the third capacitor C f1 Introduced into the base of the second switch tube Q3, accelerating the second switch tube Q3 and the main switch tube Q1 to turn off, the conduction of the freewheeling diode D1 will make the third capacitor C f1 The potential at the right end drops rapidly, which also helps the feedback. After the main switch tube Q1 is turned off, the current Ip flows through the freewheeling diode D1. At this time, the primary winding n1 is subjected to the voltage of positive on the right and negative on the left. The first switch tube Q2 and the secondary diodes D2 to D s Conducting, isolated output voltage V o2 To V os When the Ip current drops to zero, Ip flows in the reverse direction through the first switch tube Q2. When the output voltage Vo is less than the voltage regulator value U ZD The emitter junction voltage drop U Q3be Afterwards, the second switch tube Q3 and the main switch tube Q1 are turned on again, and the above process is repeated until the primary excitation inductance of the multi-winding transformer reaches volt-second balance and the first capacitor C o1 And the second capacitor C o2 ,…,C os The load-second balance is reached, and the converter circuit enters a steady state.

[0081] Furthermore, in the steady-state operation stage of the circuit, its working state is the same as the startup stage. It should be noted that at the moment when the second switch tube Q3 and the main switch tube Q1 are turned off, the primary winding n1 of the multi-winding transformer bears the output voltage with positive on the right and negative on the left. At this time, the first switch tube Q2 and the secondary diodes D2...Ds are turned on, and the energy stored in the transformer is transferred to the isolated output end. When the energy stored in the multi-winding transformer T is sufficient to maintain the energy required by the isolated output port, that is, when the direction of the primary current Ip of the multi-winding transformer T remains unchanged, the primary current Ip only flows through the freewheeling diode D1; when the energy stored in the multi-winding transformer T cannot maintain the energy required by the isolated output port, the energy of the isolated output port will be supplied by the first capacitor C o1 At this time, the primary current ip of the multi-winding transformer T drops to zero and then reverses, and the primary current Ip is reversed through the first switch tube Q2.

[0082] It should be noted that the multi-isolated output expansion circuit proposed in the embodiment of the present application is universal and is not limited to application in Figure 2 and Figure 3 In the self-excited Buck converter shown.

[0083] For the convenience of description, the above device is described in various units according to their functions. Of course, when implementing the present application, the functions of each unit can be implemented in the same or multiple software and / or hardware.

[0084] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0085] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0086] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

[0087] Although the embodiments of the present application have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A multi-isolation output expansion circuit of a self-excited Buck converter, characterized in that: The self-excited Buck converter includes a freewheeling diode, and the multi-isolated output expansion circuit includes: A first switch tube, wherein the first switch tube is connected in parallel to two ends of the freewheeling diode; A multi-winding transformer, the multi-winding transformer comprising a primary winding, a first secondary winding and a plurality of second secondary windings, wherein the primary winding is configured as an output filter inductor of the self-excited Buck converter, the first secondary winding is configured as a drive winding of the first switch tube, and the second secondary winding is configured as an isolated output terminal of the self-excited Buck converter; A first capacitor, wherein the first capacitor is configured to form a reverse freewheeling channel with the first switch tube when the multi-winding transformer has insufficient energy storage, so as to provide energy to the multi-winding transformer.

2. The multi-isolation output expansion circuit according to claim 1, characterized in that: The first switch tube is an NPN type transistor, the collector of the first switch tube is connected to the cathode of the freewheeling diode and the same-name end of the primary winding, the emitter of the first switch tube is connected to the anode of the freewheeling diode and grounded, and the base of the first switch tube is connected to the opposite-name end of the first secondary winding.

3. The multi-isolation output expansion circuit according to claim 1, characterized in that: When the multi-winding transformer has insufficient energy storage, the direction of the induced current flowing through the primary winding is from the opposite-name end to the same-name end.

4. The multi-isolation output expansion circuit according to claim 1, characterized in that: A first end of the first capacitor is connected to the opposite end of the primary winding, and a second end of the first capacitor is grounded.

5. The multi-isolation output expansion circuit according to claim 1, characterized in that: The isolated output terminal also includes: A rectifier diode, wherein an anode of the rectifier diode is connected to a corresponding opposite-name end of the second secondary winding; A second capacitor, wherein a first end of the second capacitor is connected to the cathode of the rectifier diode, and a second end of the second capacitor is connected to the corresponding same-name end of the second secondary winding.

6. The multi-isolation output expansion circuit according to claim 1, characterized in that: The same-name end of the first secondary winding and the same-name end of the second secondary winding are both grounded and isolated from each other.

7. The multi-isolation output expansion circuit according to claim 1, characterized in that: The two ends of the first capacitor are configured as the main output ends of the self-excited Buck converter, and the main loop output voltage of the main output end is determined according to the input voltage and the duty cycle of the main switch tube of the self-excited Buck converter.

8. The multi-isolation output expansion circuit according to claim 7, characterized in that: The output voltage of the isolated output terminal is determined according to the output voltage of the main circuit, the turns ratio of the primary winding to the secondary winding, and the conduction voltage of the rectifier diode in the isolated output terminal.

9. A self-excited Buck converter, characterized in that: The self-excited Buck converter comprises: Main switch tube; Freewheeling diode; And the multi-isolation output expansion circuit according to claims 1-8 above.

10. The self-excited Buck converter according to claim 9, characterized in that: The self-excited Buck converter also includes a driving circuit, which is configured to drive the main switch tube to be turned on and off to supply energy to the multi-winding transformer.

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