Auxiliary power supply circuit and power conversion circuit

Abstract

The invention provides an auxiliary power supply circuit and a power conversion circuit, and the circuit comprises a bus output circuit which comprises a plurality of bus capacitors which are connected in series; the power conversion device comprises a transformer, a plurality of primary input circuits arranged on the primary side of the transformer and a secondary output circuit arranged on the secondary side of the transformer, and each bus capacitor is connected with one primary input circuit in series; the detection control circuit is respectively connected with the secondary output circuit and the primary input circuit; the detection control circuit detects the output voltage of the secondary output circuit and controls the energy storage time of the primary input circuit according to the output voltage of the secondary output circuit and the target voltage so as to control the voltage output size of the secondary output circuit; and the primary input circuits corresponding to the plurality of bus capacitors equalize the voltages of the plurality of bus capacitors respectively in an energy storage state and an energy release state. According to the invention, the energy of the high-voltage capacitor is transmitted to the low-voltage capacitor, and rapid voltage sharing of the bus capacitor can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of voltage balancing, and in particular to an auxiliary power supply circuit and a power conversion circuit. Background Art

[0002] In many power conversions nowadays, the bus voltage is relatively high, and the bus capacitor’s withstand voltage is generally increased by connecting capacitors in series. However, due to the difference in internal resistance and capacity of the series capacitors, voltage imbalance will occur between the two capacitors during the charging and discharging process. In severe cases, one of the bus capacitors may be damaged by overvoltage. However, the existing bus capacitor equalization auxiliary power supply is based on the assumption that the load is large enough and the bus capacitor is not very large, and that it can quickly achieve bus capacitor equalization. If the load of the auxiliary source is small and the bus capacitor capacity is large, this equalization method will be much slower and difficult to apply to situations with high requirements for equalization. Summary of the invention

[0003] The main purpose of the present invention is to provide an auxiliary power supply circuit and a power conversion circuit, aiming to achieve the effect of voltage balancing of series bus capacitors.

[0004] To this end, the present invention proposes an auxiliary power supply circuit, which includes: a bus output circuit, including a plurality of bus capacitors connected in series; a power conversion device, including a transformer, a plurality of primary input circuits arranged on the primary side of the transformer and connected one-to-one with the plurality of bus capacitors respectively, and a secondary output circuit arranged on the secondary side of the transformer; a detection control circuit, wherein the detection control circuit is respectively connected to the secondary output circuit and the primary input circuit; the detection control circuit is used to detect the output voltage of the secondary output circuit, and control the energy storage time of the primary input circuit according to the output voltage of the secondary output circuit and the target voltage, so as to control the voltage output size of the secondary output circuit; the primary input circuit corresponding to the plurality of bus capacitors is used to equalize the voltages of the plurality of bus capacitors in an energy storage state / energy release state.

[0005] In one embodiment, the detection control circuit is further used to detect the peak current of the primary input circuit, and calculate the peak current threshold flowing through the primary input circuit based on the difference between the output voltage and the target voltage, and control the primary input circuit to release energy when the peak current of the primary input circuit is greater than or equal to the peak current threshold, and control the primary input circuit to store energy when the peak current is less than the peak current threshold.

[0006] In one embodiment, the primary input circuit includes a primary winding, a switching device and a leakage inductor, and the primary winding, the switching device and the leakage inductor are connected in series at both ends of a bus capacitor; the switching device is connected to the detection control circuit; the detection control circuit is respectively connected to the secondary output circuit and the switching device; the detection control circuit is used to detect the voltage of the secondary output circuit, and calculate the peak current threshold flowing through the switching device according to the difference between the voltage of the secondary output circuit and the target voltage, and control the switching device to turn off when the peak current of the switching device is greater than or equal to the peak current threshold, and control the switching device to turn on when the peak current is less than the peak current threshold; the switching device drives the primary winding to store energy / release energy based on the control of the detection control circuit.

[0007] In one embodiment, the primary input circuit further includes a resistor, and the resistor, the primary winding, the switch device and the leakage inductance are connected in series to two ends of the bus capacitor.

[0008] In one embodiment, the leakage inductance is an equivalent leakage inductance formed by coupling the primary input circuit and the secondary output circuit, and the resistance is an equivalent resistance formed by the primary input circuit.

[0009] In one embodiment, the detection control circuit includes: an outer voltage loop, the outer voltage loop includes: a voltage detection circuit, the voltage detection circuit is connected to the secondary output circuit; the voltage detection circuit is used to detect the output voltage of the secondary output circuit; a controller, the controller is connected to the voltage detection circuit; the controller is used to output a voltage reference signal according to the difference between the output voltage of the secondary output circuit and the target voltage; wherein the voltage reference signal is used to indicate the peak current threshold flowing through the switching device; an inner current loop, the inner current loop includes: a current detection circuit, the current detection circuit is connected in series with the switching device; the current detection circuit is used to detect the peak current flowing through the switching device and output a corresponding current detection signal; a comparator, the comparator is respectively connected to the controller and the current detection circuit; the comparator outputs a result signal based on the voltage reference signal and the current detection signal; a driver, the driver is respectively connected to the comparator and the switching device; the driver is used to drive the switching device to be turned on / off according to the result signal.

[0010] In one embodiment, the plurality of bus capacitors connected in series include a first bus capacitor and a second bus capacitor; the primary input circuit includes a first primary input circuit and a second primary input circuit, the first primary input circuit is connected to the second primary input circuit, the first bus capacitor is connected in series to the first primary input circuit, and the second bus capacitor is connected in series to the second primary input circuit.

[0011] In one embodiment, the first primary input circuit includes a first primary winding, a first switching device, a first resistor and a first leakage inductor, and the first primary winding, the first switching device, the first resistor and the first leakage inductor are connected in series at both ends of the first bus capacitor; the first switching device is connected to the detection control circuit; the second primary input circuit includes a second primary winding, a second switching device, a second resistor and a second leakage inductor, and the second primary winding, the second switching device, the second resistor and the second leakage inductor are connected in series at both ends of the second bus capacitor; the second switching device is connected to the detection control circuit; wherein the connection points between the first primary input circuit and the second primary input circuit are respectively connected to the first switching device, the first bus capacitor, the second bus capacitor and the second resistor.

[0012] In one embodiment, the detection control circuit is connected to the first switch device, the second switch device and the secondary output circuit respectively; the detection control circuit is used to detect the output voltage of the secondary output circuit and the first current flowing through the first switch device and the second current of the second switch device, and determine the total peak current threshold flowing through the first switch device and the second switch device according to the difference between the voltage of the secondary output circuit and the target voltage, and control the first switch device and the second switch device to be synchronously turned off when the sum of the first current and the second current is greater than or equal to the total peak current threshold, and control the first switch device and the second switch device to be synchronously turned on when the sum of the first current and the second current is less than the total peak current threshold; the first switch device drives the first primary winding to store energy / release energy based on the control of the detection control circuit; the second switch device drives the second primary winding to store energy / release energy based on the control of the detection control circuit.

[0013] The present invention provides a power conversion circuit, which includes a main power supply circuit and the auxiliary power supply circuit, wherein the main power supply circuit is connected to the auxiliary power supply circuit.

[0014] The present invention proposes an auxiliary power supply circuit and a power conversion circuit, wherein the auxiliary power supply circuit comprises: a bus output circuit, comprising a plurality of bus capacitors connected in series; a power conversion device, comprising a transformer, a plurality of primary input circuits arranged on the primary side of the transformer and connected one-to-one with the plurality of bus capacitors, and a secondary output circuit arranged on the secondary side of the transformer; a detection control circuit, wherein the detection control circuit is connected to the secondary output circuit and the primary input circuit respectively; the detection control circuit detects the output voltage of the secondary output circuit, and controls the energy storage time of the primary input circuit according to the output voltage of the secondary output circuit and the target voltage, so as to control the voltage output size of the secondary output circuit; the primary input circuits corresponding to the plurality of bus capacitors, respectively, in the energy storage state and the energy release state, balance the voltages of the plurality of bus capacitors. The present invention transfers the energy of the high voltage capacitor to the low voltage capacitor, and can realize the rapid voltage balancing of the bus capacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0016] Figure 1 A circuit flow chart of an auxiliary power supply circuit of the present invention;

[0017] Figure 2 It is a schematic diagram of a busbar capacitor voltage-sharing auxiliary source circuit in the prior art;

[0018] Figure 3 A circuit structure diagram of an auxiliary power supply circuit of the present invention;

[0019] Figure 4 This is a schematic diagram of the improved bus capacitor voltage-sharing auxiliary source circuit of the present invention;

[0020] Figure 5 This is a schematic diagram of the excitation current path of the improved voltage-sharing auxiliary source of the present invention;

[0021] Figure 6 This is a schematic diagram of the discharge current path of the improved voltage-balanced auxiliary source of the present invention;

[0022] Figure 7 It is a control schematic diagram of the detection control circuit of the present invention;

[0023] Figure 8 Schematic diagram of the switching logic timing of the switch device of the present invention.

[0024] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0025] 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 only 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.

[0026] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0027] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0029] In many power conversion applications, the bus voltage is often high. In order to improve the voltage resistance of the bus capacitor, the capacitor is usually connected in series. However, due to the difference in internal resistance and capacity, the series capacitor will have voltage imbalance during the charging and discharging process, which may cause one of the bus capacitors to be damaged by overvoltage in severe cases. The existing solution is to set two primary windings on the auxiliary source, corresponding to the upper and lower bus capacitors respectively, and use the function of the primary diode to make the auxiliary winding corresponding to the high-voltage bus capacitor "top off" the other bus winding when the switch tube is turned on, and provide energy to the auxiliary source at the same time, so as to achieve bus capacitor voltage balancing by increasing the energy consumption of the high-voltage bus capacitor. However, this existing voltage balancing method has limitations. It can only achieve voltage balancing quickly when the load is large enough and the bus capacitor is not very large. If the load of the auxiliary source is small and the bus capacitor capacity is large, the voltage balancing speed will be very slow, which is difficult to meet the occasions with high voltage balancing requirements.

[0030] To this end, the present invention proposes an auxiliary power supply circuit, referring to Figure 1 , the auxiliary power supply circuit comprises:

[0031] A bus output circuit, comprising a plurality of bus capacitors 10 connected in series;

[0032] The power conversion device comprises a transformer, a plurality of primary input circuits 20 arranged on the primary side of the transformer and connected to a plurality of bus capacitors 10 in one-to-one correspondence, and a secondary output circuit 30 arranged on the secondary side of the transformer, wherein each bus capacitor is connected in series with a primary input circuit 20;

[0033] A detection control circuit 40, the detection control circuit 40 is connected to the secondary output circuit 30 and the primary input circuit 20 respectively; the detection control circuit 40 is used to detect the output voltage of the secondary output circuit 30, and control the energy storage time of the primary input circuit 20 according to the output voltage of the secondary output circuit 30 and the target voltage, so as to control the voltage output size of the secondary output circuit 30;

[0034] The primary input circuit 20 corresponding to the plurality of bus capacitors C0 balances the voltages of the plurality of bus capacitors C0 in an energy storage state / energy release state.

[0035] It is understandable that due to the difference in internal resistance and capacity, capacitors in series will have voltage imbalance during the charge and discharge process. Figure 2In the circuit diagram of the bus capacitor C0 voltage equalization auxiliary source of the prior art, the diode of the prior solution will hinder the energy transmission between the bus capacitors C0, and the energy transmission between the bus capacitors C0 cannot be realized. The only way to achieve voltage equalization of the bus capacitor C0 is to increase the energy consumption of the high-voltage bus capacitor C0 by providing energy to the auxiliary source. It can be seen that the existing solution has a single way to achieve voltage equalization. If the load of the auxiliary source is small and the capacity of the bus capacitor C0 is large, the speed of the existing solution to achieve voltage equalization will be slow, and it is difficult to apply to occasions with high voltage requirements. The purpose of the present invention is to propose an auxiliary power supply circuit in view of the application limitations of the above-mentioned existing bus capacitor C0 voltage equalization technology. When there is a voltage difference between the two bus capacitors C0, the energy balance between the two bus capacitors C0 is achieved through the auxiliary power supply circuit. Through the characteristics of the forward transformer, the energy of the high-voltage capacitor is transferred to the low-voltage capacitor in a suitable manner. It can achieve rapid voltage equalization of the bus capacitor C0, and even when the capacity of the bus capacitor C0 is large or the load of the auxiliary source is small, the bus series capacitor voltage equalization can still be quickly achieved.

[0036] In this embodiment, each bus capacitor C0 is connected in series with a primary input circuit 20. When the multiple primary input circuits 20 are working, when the switch tube in the primary input circuit 20 is turned on, the primary input circuit 20 is in an energy storage state. Since the primary input circuit 20 of this embodiment does not have a diode, it will not hinder the energy transmission between the bus capacitors C0, so the primary input circuit 20 can realize voltage balancing of multiple bus capacitors C0 in the energy storage state. When the switch tube in the primary input circuit 20 is turned off, the primary input circuit 20 is in an energy release state, and the secondary output circuit 30 receives the energy released by the primary input circuit 20, thereby realizing energy transfer. This process also increases the energy consumption of the high-voltage bus capacitor C0, thereby realizing voltage balancing of multiple bus capacitors C0 in the energy release state. The secondary output circuit 30 couples, rectifies and filters the energy transmitted from the primary input circuit 20 and outputs a stable DC voltage. In practical applications, the detection control circuit 40 compares the output voltage of the detected secondary output circuit 30 with the preset target voltage. If the output voltage is lower than the target voltage, the detection control circuit 40 will increase the on-time of the switch tube in the primary input circuit 20, thereby increasing the energy storage time of the primary input circuit 20, increasing the peak current of the primary input circuit 20, and more energy can be transferred to the secondary output circuit 30, thereby increasing the output voltage. Conversely, if the output voltage is higher than the target voltage, the detection control circuit 40 will reduce the on-time of the switch tube in the primary input circuit 20, thereby reducing the energy storage time of the primary input circuit 20, reducing the peak current of the primary input circuit 20, reducing the energy transferred to the secondary output circuit 30, and reducing the output voltage. In this way, the output voltage stabilization effect is achieved.

[0037] It should be noted that the power conversion device is composed of a primary input circuit 20 and a secondary output circuit 30. In theory, all magnetic fluxes in an ideal transformer can be fully coupled between the primary input circuit 20 and the secondary output circuit 30. However, leakage inductance Lr0 will be formed in an actual transformer. When the primary input circuit 20 corresponding to multiple bus capacitors C0 is in an energy storage state, due to the presence of leakage inductance Lr0, the voltage difference of multiple bus capacitors C0 mainly acts on the leakage inductance Lr0, and the interaction between each primary input circuit 20 through leakage inductance Lr0 can achieve the effect of voltage balancing of multiple bus capacitors C0. Compared with the existing auxiliary power supply with series bus voltage balancing, the circuit architecture of this embodiment lacks a diode on the primary side. Since the diode will hinder the energy exchange between the bus capacitors C0, this embodiment can not only ensure the normal output of the auxiliary source, but also in the state of excitation energy storage / energy output of the power conversion device, that is, the primary input circuit 20 is in the energy storage state / energy release state, the voltage of multiple bus capacitors C0 is balanced, thereby improving the voltage balancing speed of the bus capacitor C0.

[0038] The present invention proposes an auxiliary power supply circuit, which includes: a bus output circuit, including multiple bus capacitors C0 connected in series; a power conversion device, including a primary input circuit 20 and a secondary output circuit 30, each bus capacitor C0 is connected in series with a primary input circuit 20; a detection control circuit 40, the detection control circuit 40 is connected to the secondary output circuit 30 and the primary input circuit 20 respectively; the detection control circuit 40 is used to detect the output voltage of the secondary output circuit 30, and control the energy storage time of the primary input circuit 20 according to the output voltage of the secondary output circuit 30 and the target voltage, so as to control the voltage output size of the secondary output circuit 30; the primary input circuit 20 corresponding to the multiple bus capacitors C0, respectively, in the energy storage state and the energy release state, balances the voltages of the multiple bus capacitors C0. In this way, the present invention, through the characteristics of the forward transformer, can transfer the energy of the high-voltage capacitor to the low-voltage capacitor through the primary input circuit 20, thereby realizing rapid voltage equalization among multiple bus capacitors C0, and even when the capacity of the bus capacitor C0 is large or the auxiliary source load is very small, rapid voltage equalization of the bus series capacitors can still be realized.

[0039] In one embodiment, referring to Figure 1 The detection control circuit 40 is also used to detect the peak current of the primary input circuit 20, and calculate the peak current threshold flowing through the primary input circuit 20 based on the difference between the output voltage and the target voltage. When the peak current of the primary input circuit 20 is greater than or equal to the peak current threshold, the primary input circuit 20 is controlled to release energy; when the peak current is less than the peak current threshold, the primary input circuit 20 is controlled to store energy.

[0040] It is understandable that when the power conversion device operates in the forward state, Figure 3 , due to the voltage difference between the multiple bus capacitors C0 connected in series, the current rise rate and magnitude can only be limited by the leakage inductance Lr0 and the resistor R0 parasitic on the primary input circuit 20. Excessive peak current will cause overcurrent damage to the switch tube in the primary input circuit 20 and cause the output voltage to be unstable. Therefore, in this embodiment, the peak current threshold flowing through the primary input circuit 20 can be calculated based on the difference between the output voltage and the target voltage, thereby realizing dynamic control of the peak current threshold of the primary input circuit 20. When it is detected that the peak current of the primary input circuit 20 is less than the peak current threshold, the primary input circuit 20 is controlled to store energy, that is, the switch tube of the primary input circuit 20 is controlled to be turned on, and the peak current rises at this time. When it is detected that the peak current of the primary input circuit 20 is greater than or equal to the peak current threshold, the primary input circuit 20 is controlled to release energy, that is, the switch tube of the primary input circuit 20 is controlled to be turned off, thereby limiting the rise of the peak current. In this way, this embodiment can limit the rising rate and size of the current by controlling the shutdown of the switch tube of the primary input circuit 20. Since the peak current threshold is calculated by the difference between the output voltage and the target voltage, the peak current size of the primary input circuit 20 can be controlled to be within a relatively stable range, maintaining the output voltage near the target voltage, thereby improving the stability of the circuit.

[0041] In one embodiment, referring to Figure 3 The primary input circuit 20 includes a primary winding N0, a switch device Q0 and a leakage inductor Lr0, wherein the primary winding N0, the switch device Q0 and the leakage inductor Lr0 are connected in series to two ends of a bus capacitor C0; the switch device Q0 is connected to a detection control circuit 40;

[0042] The detection control circuit 40 is connected to the secondary output circuit 30 and the switch device Q0 respectively; the detection control circuit 40 is used to detect the voltage of the secondary output circuit 30, and calculate the peak current threshold flowing through the switch device Q0 according to the difference between the voltage of the secondary output circuit 30 and the target voltage, and control the switch device Q0 to be turned off when the peak current of the switch device Q0 is greater than or equal to the peak current threshold, and control the switch device Q0 to be turned on when the peak current is less than the peak current threshold;

[0043] The switching device Q0 drives the primary winding 20 to store energy / release energy based on the control of the detection control circuit 40 .

[0044] It can be understood that in this embodiment, both ends of each bus capacitor C0 are connected in series with a primary winding N0, a switch device Q0 and a leakage inductor Lr0, and the detection control circuit 40 is connected to the output end of the controlled end of the switch device Q0, for controlling the on and off of the switch device Q0, and for collecting the peak current of the switch device Q0. In practical applications, when the system starts, the detection control circuit 40 first detects the output voltage of the secondary output circuit 30, and calculates the peak current threshold flowing through the switch device Q0 according to the difference between the voltage of the secondary output circuit 30 and the target voltage. When the peak current of the switch device Q0 is greater than or equal to the peak current threshold, the switch device Q0 is controlled to be turned off to limit the rise of the peak current. When the peak current is less than the peak current threshold, the switch device Q0 is controlled to be turned on to control the peak current to continue to rise. During operation, the detection control circuit 40 continuously detects the output voltage of the secondary output circuit 30 and the peak current flowing through the switch device Q0, so that the peak current of the switch device Q0 is stabilized near the calculated peak current threshold, achieving the effect of stabilizing the output voltage and limiting the excessive peak current, thereby improving the stability and safety of the circuit. Among them, under the control of the detection control circuit 40, the switch device Q0 drives the primary winding N0 to store energy when turned on, and transfers the energy to the secondary output circuit 30 through transformer coupling when turned off, thereby realizing the conversion and output of electric energy. When the switch device Q0 is in a synchronous conduction state, due to the absence of the obstruction of the diode and the existence of the leakage inductance Lr0, energy can be transferred between multiple bus capacitors C0, and voltage balancing can be achieved.

[0045] In one embodiment, referring to Figure 3 The primary input circuit 20 further includes a resistor R0. The resistor R0, the primary winding N0, the switch device Q0 and the leakage inductor Lr0 are connected in series to two ends of a bus capacitor C0.

[0046] It should be noted that in the process of synchronous energy storage in the primary input circuit 20, the switch device Q0 therein is synchronously turned on. If there is a voltage difference between multiple bus capacitors C0, the leakage inductance Lr0 can be used as the main path for the voltage difference to act. Since there is no diode, the energy of the high-voltage bus capacitor C0 will be transferred to the low-voltage bus capacitor C0, thereby achieving voltage balancing. Among them, the resistor R0 can limit the current in the circuit from being too large. The primary winding N0 can store energy / release energy under the drive of the switch device Q0.

[0047] In one embodiment (not shown in the figure), the leakage inductance is an equivalent leakage inductance formed by coupling the primary input circuit and the secondary output circuit, and the resistance is an equivalent resistance formed by the primary input circuit.

[0048] It can be understood that in this embodiment, the leakage inductance is formed due to the incomplete coupling of the primary winding in the primary input circuit and the secondary winding in the secondary output circuit, such as the winding gap, the influence of the insulating material and the uneven distribution of the windings, which lead to the incomplete coupling of part of the magnetic flux; the resistance is composed of the wire resistance in the primary input circuit, the on-resistance of the switching device and the equivalent series resistance of other components. Due to the presence of the diode in the primary input circuit of the existing scheme, the energy conversion between the bus capacitors is hindered, and the bus capacitors cannot be equalized. In this embodiment, the diode is removed, and the energy transfer between the bus capacitors can be realized through the equivalent leakage inductance and the equivalent resistance, and the current change rate and peak current during energy transfer can be limited.

[0049] In one embodiment, referring to Figure 7 , the detection control circuit 40 includes:

[0050] Outer voltage loop, the outer voltage loop includes:

[0051] A voltage detection circuit 41, the voltage detection circuit 41 is connected to the secondary output circuit 30; the voltage detection circuit 41 is used to detect the output voltage of the secondary output circuit 30;

[0052] A controller 42, the controller 42 is connected to the voltage detection circuit 41; the controller 42 is used to output a voltage reference signal according to the difference between the output voltage of the secondary output circuit 30 and the target voltage; wherein the voltage reference signal is used to indicate a peak current threshold value flowing through the switch device Q0;

[0053] Inner current loop, the inner current loop includes:

[0054] A current detection circuit 45, the current detection circuit 45 is connected in series with the switch device Q0; the current detection circuit 45 is used to detect the peak current flowing through the switch device Q0 and output a corresponding current detection signal;

[0055] A comparator 43, the comparator 43 is connected to the controller 42 and the current detection circuit 45 respectively; the comparator 43 outputs a result signal based on the voltage reference signal and the current detection signal;

[0056] The driver 44 is connected to the comparator 43 and the switch device Q0 respectively; the driver 44 is used to drive the switch device Q0 to be turned on / off according to the result signal.

[0057] It can be understood that in this embodiment, the voltage detection circuit 41 is connected to the secondary output circuit 30, and its voltage is monitored in real time and transmitted to the controller 42. It should be noted that the controller 42 can be specifically a PI (proportional-integral) controller, and the difference between the output voltage of the secondary output circuit 30 and the target voltage can be input into the PI controller, and the PI controller generates an adjustment signal, which is a voltage reference signal for indicating the peak current threshold value flowing through the switch device Q0. The comparator 43 compares the signal with the current detection signal output by the current detection circuit 45, and the driver 44 drives the switch device to turn on / off according to the comparison result. For example, if the output voltage is lower than the target voltage, the PI controller outputs a voltage reference signal for indicating a larger peak current threshold value. At this time, the peak current of the switch device Q0 is less than the peak current threshold value, and the switch device Q0 is turned on, and the peak current of the switch device Q0 continues to rise, and the output voltage also increases accordingly. If the output voltage is higher than the target voltage, the PI controller outputs a voltage reference signal indicating a smaller peak current threshold. At this time, the peak current of the switch device Q0 is greater than the peak current threshold, and the comparator flips to drive the switch device Q0 to turn off. The peak current of the switch device Q0 decreases, and the output voltage decreases accordingly. In this way, the present embodiment can achieve a stable output of the output voltage and can limit the peak current from being too large, thereby improving the stability and safety of the circuit.

[0058] In one embodiment, referring to Figure 4 , the plurality of bus capacitors connected in series include a first bus capacitor C1 and a second bus capacitor C2;

[0059] The primary input circuit 20 includes a first primary input circuit 21 and a second primary input circuit 22, the first primary input circuit 21 is connected to the second primary input circuit 22, the first bus capacitor C1 is connected in series to the first primary input circuit 21, and the second bus capacitor C2 is connected in series to the second primary input circuit 22. In addition, the secondary output circuit 30 includes a secondary winding N3, a third diode D3 and an output capacitor C3, and the connection point between the output capacitor C3 and the ground terminal is connected to the voltage detection circuit 41 in the detection control circuit 40;

[0060] In one embodiment, the first primary input circuit 21 includes a first primary winding Lm, a first switch device Q8, a first resistor R2 and a first leakage inductor Lr1, and the first primary winding Lm, the first switch device Q8, the first resistor R2 and the first leakage inductor Lr1 are connected in series at both ends of the first bus capacitor C1; the first switch device Q8 is connected to the detection control circuit;

[0061] The second primary input circuit 22 includes a second primary winding N2, a second switch device Q9, a second resistor R3 and a second leakage inductor Lr2. The second primary winding N2, the second switch device Q9, the second resistor R3 and the second leakage inductor Lr2 are connected in series to both ends of the second bus capacitor C2; the second switch device Q9 is connected to the detection control circuit;

[0062] The connection point between the first primary input circuit 21 and the second primary input circuit 22 is connected to the first switch device, the first bus capacitor C1, the second bus capacitor C2 and the second resistor R3 respectively.

[0063] The detection control circuit is respectively connected to the first switch device Q8, the second switch device Q9 and the secondary output circuit 30;

[0064] a detection control circuit, for detecting an output voltage of the secondary output circuit 30 and a first current flowing through the first switch device Q8 and a second current flowing through the second switch device Q9, and determining a total peak current threshold flowing through the first switch device Q8 and the second switch device Q9 according to a difference between the voltage of the secondary output circuit 30 and a target voltage, and controlling the first switch device Q8 and the second switch device Q9 to be synchronously turned off when the sum of the first current and the second current is greater than or equal to the total peak current threshold, and controlling the first switch device Q8 and the second switch device Q9 to be synchronously turned on when the sum of the first current and the second current is less than the total peak current threshold;

[0065] The first switch device Q8 drives the first primary winding Lm to store energy / release energy based on the control of the detection control circuit; the second switch device Q9 drives the second primary winding N2 to store energy / release energy based on the control of the detection control circuit.

[0066] It is understandable that, combined with Figure 7 and Figure 8In this embodiment, the voltage detection circuit 41 in the detection control circuit is connected to the output capacitor in the secondary output circuit 30 to detect the voltage of the output capacitor in the secondary output circuit 30 in real time. When the circuit is working, the detection control circuit continuously monitors the output voltage of the secondary output circuit. At the same time, the first current flowing through the first switch device Q8 and the second current flowing through the second switch device Q9 are monitored. The detected secondary output voltage is compared with the preset target voltage to obtain an error signal. The error signal is processed using a PI controller to generate a voltage reference signal for indicating a total peak current threshold, which determines the maximum current allowed to flow. When the sum of the first current and the second current is less than the total peak current threshold, that is, when the actual total current is less than the total peak current threshold, the detection control circuit sends a signal to keep the first switch device Q8 and the second switch device Q9 in a synchronous conduction state. At this time, the current continues to flow into the first primary winding Lm and the second primary winding N2, and the peak current rises to achieve energy storage. When the sum of the first current and the second current is greater than or equal to the total peak current threshold, that is, when the actual total current is greater than or equal to the total peak current threshold, the detection control circuit sends a signal to keep the first switch device Q8 and the second switch device Q9 in a synchronous off state, and at this time, the energy stored in the first primary winding Lm and the second primary winding N2 is output through the secondary winding. In this way, the output voltage of the secondary output circuit can be maintained stable near the target voltage.

[0067] It should be noted that if the voltage of the first bus capacitor C1 is greater than the voltage of the second bus capacitor C2, please refer to Figure 5 When the first primary input circuit 21 and the second primary input circuit 22 are in the energy storage state, the first leakage inductance Lr1, the second leakage inductance Lr2, the first resistor R2 and the second resistor R3 can achieve the voltage balancing effect of the first bus capacitor C1 and the second bus capacitor C2. Since no diode is provided, the energy of the first capacitor C1 can be directly transferred to the second capacitor C2. When the first primary input circuit 21 and the second primary input circuit 22 are in the energy release state, please refer to Figure 6 , the energy consumption of the first capacitor C1 is higher than that of the first capacitor C2, and the voltage balancing effect of the first bus capacitor C1 and the second bus capacitor C2 can also be achieved. In this way, the first bus capacitor C1 and the second bus capacitor C2 can be quickly balanced.

[0068] Based on the above embodiments, refer to Figure 5, during the process of synchronous energy storage of the first primary input circuit 21 and the second primary input circuit 22, the first switch tube Q8 and the second switch tube Q9 are turned on at the same time. Assuming that the voltage V1 of the bus capacitor C1 is higher than the voltage V2 of the bus capacitor C2, the inductance of the first primary winding is limited and is Lm, the first primary winding is represented by the symbol of Lm, and the first primary winding Lm is connected in parallel with the winding N1 of the ideal transformer. At this time, because the number of turns of the winding N1 and the winding N2 are the same, the voltage of V2 converted to the winding N1 of the ideal transformer is still V2, then the additional voltage difference V1-V2 corresponding to the winding N1 of the ideal transformer will act on the first leakage inductance Lr1 and the second resistor R2. Then the circuit current I1 is I1≈(V1-V2) / Lr1. Since the first switch tube Q8 and the second switch tube Q9 are turned on, the current flowing through the first primary winding Lm and the second primary winding N2 is basically 0, the second resistor R2 is equivalent to the equivalent impedance of the line, and R2 has a low impedance. Therefore, the voltage difference V1-V2 mainly acts on the first leakage inductor Lr1 and excites the first leakage inductor Lr1. At the same time, V2 acts on the first primary winding Lm and excites it. The excitation current I2 generated at this time is: I2=V2 / Lm. The difference current I3 between I1 and I2 is the charging current from the high-voltage bus capacitor to the low-voltage bus capacitor. The difference current I3 is also a key factor in achieving rapid voltage equalization of the high-voltage difference between the two bus capacitors. By accurately calculating I3, the speed and efficiency of the voltage equalization process can be evaluated. If the value of I3 is large, it means that the energy is transferred faster from the high-voltage capacitor to the low-voltage capacitor, and the voltage equalization process will be faster; conversely, if the value of I3 is small, the voltage equalization speed may be slower.

[0069] In addition, refer to Figure 6 , when the first primary input circuit 21 and the second primary input circuit 22 release energy synchronously, the first switch tube Q8 and the second switch tube Q9 are turned off at the same time, and the excitation process of the first primary winding Lm ends. At this time, the current I2 stored in the first primary winding Lm is converted to the N3 winding through the secondary winding N3 to charge the output capacitor through the turns ratio relationship of the winding N1 of the ideal transformer, and the charging current (I2*N1) / N3 is, thereby ensuring the stability of the output voltage.

[0070] The present invention also proposes a power conversion circuit, which includes a main power supply circuit and an auxiliary power supply circuit. The specific setting of the auxiliary power supply circuit refers to the above-mentioned embodiment. Since this power conversion circuit adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here one by one.

[0071] The above are only optional embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. An auxiliary power supply circuit, characterized in that: The auxiliary power supply circuit comprises: A bus output circuit includes a plurality of bus capacitors connected in series; A power conversion device, comprising a transformer, a plurality of primary input circuits arranged on the primary side of the transformer and connected to the plurality of bus capacitors in one-to-one correspondence, and a secondary output circuit arranged on the secondary side of the transformer; a detection control circuit, the detection control circuit being connected to the secondary output circuit and the primary input circuit respectively; the detection control circuit being used to detect the output voltage of the secondary output circuit, and to control the energy storage time of the primary input circuit according to the output voltage of the secondary output circuit and the target voltage, so as to control the voltage output size of the secondary output circuit; The primary input circuit corresponding to the plurality of bus capacitors is used to balance the voltages of the plurality of bus capacitors in an energy storage state / energy release state.

2. The auxiliary power supply circuit according to claim 1, characterized in that: The detection control circuit is also used to detect the peak current of the primary input circuit, and calculate the peak current threshold flowing through the primary input circuit based on the difference between the output voltage and the target voltage, and control the primary input circuit to release energy when the peak current of the primary input circuit is greater than or equal to the peak current threshold, and control the primary input circuit to store energy when the peak current is less than the peak current threshold.

3. The auxiliary power supply circuit according to claim 2, characterized in that: The primary input circuit includes a primary winding, a switch device and a leakage inductor, wherein the primary winding, the switch device and the leakage inductor are connected in series to two ends of a bus capacitor; the switch device is connected to the detection control circuit; The detection control circuit is connected to the secondary output circuit and the switch device respectively; The detection control circuit is used to detect the voltage of the secondary output circuit, and calculate the peak current threshold flowing through the switch device according to the difference between the voltage of the secondary output circuit and the target voltage, and control the switch device to be turned off when the peak current of the switch device is greater than or equal to the peak current threshold, and control the switch device to be turned on when the peak current is less than the peak current threshold; The switch device drives the primary winding to store energy / release energy based on the control of the detection control circuit.

4. The auxiliary power supply circuit according to claim 3, characterized in that: The primary input circuit also includes a resistor, and the resistor, the primary winding, the switch device and the leakage inductance are connected in series to two ends of the bus capacitor.

5. The auxiliary power supply circuit according to claim 4, characterized in that: The leakage inductance is an equivalent leakage inductance formed by coupling the primary input circuit and the secondary output circuit, and the resistance is an equivalent resistance formed by the primary input circuit.

6. The auxiliary power supply circuit as claimed in claim 3, characterized in that: The detection control circuit comprises: An outer voltage loop, the outer voltage loop comprising: A voltage detection circuit, the voltage detection circuit is connected to the secondary output circuit; the voltage detection circuit is used to detect the output voltage of the secondary output circuit; a controller connected to the voltage detection circuit; the controller is used to output a voltage reference signal according to a difference between an output voltage of the secondary output circuit and a target voltage; wherein the voltage reference signal is used to indicate a peak current threshold value flowing through the switching device; An inner current loop, the inner current loop comprising: a current detection circuit, the current detection circuit being connected in series with the switch device; the current detection circuit being used to detect a peak current flowing through the switch device and output a corresponding current detection signal; A comparator, the comparator being connected to the controller and the current detection circuit respectively; the comparator outputting a result signal based on the voltage reference signal and the current detection signal; A driver is connected to the comparator and the switch device respectively; the driver is used to drive the switch device to be turned on / off according to the result signal.

7. The auxiliary power supply circuit according to claim 1, characterized in that: The plurality of bus capacitors connected in series include a first bus capacitor and a second bus capacitor; The primary input circuit includes a first primary input circuit and a second primary input circuit, the first primary input circuit is connected to the second primary input circuit, the first bus capacitor is connected in series to the first primary input circuit, and the second bus capacitor is connected in series to the second primary input circuit.

8. The auxiliary power supply circuit according to claim 7, characterized in that: The first primary input circuit comprises a first primary winding, a first switch device, a first resistor and a first leakage inductor, wherein the first primary winding, the first switch device, the first resistor and the first leakage inductor are connected in series at two ends of the first bus capacitor; the first switch device is connected to the detection control circuit; The second primary input circuit comprises a second primary winding, a second switch device, a second resistor and a second leakage inductor, wherein the second primary winding, the second switch device, the second resistor and the second leakage inductor are connected in series at both ends of the second bus capacitor; the second switch device is connected to the detection control circuit; The connection point between the first primary input circuit and the second primary input circuit is respectively connected to the first switch device, the first bus capacitor, the second bus capacitor and the second resistor.

9. The auxiliary power supply circuit according to claim 8, characterized in that: The detection control circuit is respectively connected to the first switch device, the second switch device and the secondary output circuit; The detection control circuit is used to detect the output voltage of the secondary output circuit and the first current flowing through the first switch device and the second current flowing through the second switch device, and determine the total peak current threshold flowing through the first switch device and the second switch device according to the difference between the voltage of the secondary output circuit and the target voltage, and control the first switch device and the second switch device to be synchronously turned off when the sum of the first current and the second current is greater than or equal to the total peak current threshold, and control the first switch device and the second switch device to be synchronously turned on when the sum of the first current and the second current is less than the total peak current threshold; The first switch device drives the first primary winding to store energy / release energy based on the control of the detection control circuit; The second switch device drives the second primary winding to store energy / release energy based on the control of the detection control circuit.

10. A power conversion circuit, characterized in that: The power conversion circuit includes a main power supply circuit and an auxiliary power supply circuit as described in any one of claims 1 to 9, and the main power supply circuit and the auxiliary power supply circuit are connected.

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