Auxiliary power supply and starting control circuit thereof

Abstract

The invention discloses an auxiliary power supply and a starting control circuit thereof. The starting control circuit comprises a current limiting circuit, a starting circuit, a voltage stabilizing circuit, a second MOS tube, a first capacitor and a first diode. The input end of the current limiting circuit inputs bus voltage, and the output end of the current limiting circuit is connected with the input end of the voltage stabilizing circuit and the grid electrode of the second MOS tube; the source electrode of the second MOS tube is connected with the anode of the first diode, and the cathode of the first diode is connected with the input end of the starting circuit. The output end of the starting circuit is connected with one end of the first capacitor; the output end of the voltage stabilizing circuit and the other end of the first capacitor are grounded. The input end of the starting circuit is not directly connected with a battery bus and does not need to bear bus voltage. The voltage of the input end of the starting circuit is stable and does not change along with the input voltage, and the difficulty of the design and component type selection of the starting circuit can be greatly reduced. The problems of high power consumption and serious heating of the starting circuit are solved, and the capacitive load carrying capacity of the auxiliary power supply can be further improved.

Description

Technical Field

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

[0002] With the development of the energy storage industry, battery capacity is getting larger and larger, and the supply voltage is gradually increasing. Currently, the 800V system is being promoted and applied, and the battery system may adopt a 1200V system or even a 1500V system in the future. As an indispensable component, the auxiliary power supply usually takes power directly from the high-voltage end of the battery at the input end, and after PWM control and transformer conversion, it outputs low voltage to power each circuit unit.

[0003] The application of auxiliary power supply for energy storage system has the following characteristics: 1. High input voltage, usually up to 1000V; 2. Wide input voltage range, usually input transformation ratio greater than 5:1, that is, 200~1000V or wider input voltage range. This application feature will bring great challenges to the design of such auxiliary power supply.

[0004] The control part of the low-power auxiliary power supply consists of a PWM controller and a starting circuit, such as Figure 1 As shown. When the power supply starts, the startup circuit first charges the VDD capacitor after reducing the bus voltage and limiting the current. When the PWM controller power supply voltage reaches the startup threshold, the MOS tube switch is controlled. After the main power is working normally, the auxiliary winding supplies power to the PWM controller, and then the startup circuit stops working. In general, in controllers with a high degree of integration, the startup circuit, PWM controller, and MOS tube are integrated into one chip, and the input end of the startup circuit is connected to the drain of the MOS tube to save the pins of the chip, such as Figure 2 In essence Figure 2 The startup circuit and Figure 1 They are the same, the input ends of the starting circuit are all connected to the bus high voltage.

[0005] The startup circuit is generally composed of resistors in series or constant current sources. When the input end is connected to the bus high voltage, when it is applied to high voltage input, in order to meet the design specifications of the resistor withstand voltage, the startup circuit composed of resistors in series has a large number of resistors in series, resulting in a large board area. When applied to a wide range of voltage input, the resistance value of the resistor is difficult to compromise. In order to ensure that the low-voltage input can start normally, the resistance value should be small. However, the loss of the resistor will be very large when the high-voltage input is applied. In addition, the startup circuit composed of resistors in series will continue to consume power. Even if the auxiliary winding can supply power to the startup circuit normally, the resistor in the startup circuit will continue to consume power. The startup circuit composed of a constant current source can make the output current of the startup circuit more consistent within the input high and low voltage range, and can reduce the loss of the startup circuit under high voltage input to a certain extent, but the lower loss is limited. For example, when the input voltage is 800V and the startup current is 1mA, the startup loss is as high as 800mW. In order to ensure the reliability of withstand voltage, the constant current source solution will still have a relatively large package, resulting in a relatively large board area. The problem of large losses in the starting circuit will also reduce the capacitive load carrying capacity of the power supply. This is because the larger the capacitive load, the longer it takes to establish the power output and auxiliary power supply, so the starting circuit needs to work longer, which leads to the risk of overheating and damage to the starting circuit. Summary of the invention

[0006] The purpose of the present invention is to provide an auxiliary power supply and a starting control circuit thereof, which can solve the problems of large starting circuit loss and large starting chip size caused by connecting the input end of the starting circuit to the battery bus in the prior art.

[0007] The objective of the present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a startup control circuit for an auxiliary power supply, wherein a first embodiment thereof comprises a current limiting circuit, a startup circuit, a voltage stabilizing circuit, a second MOS transistor TR2, a first capacitor C1 and a first diode D1; a bus voltage is input to an input end of the current limiting circuit, and an output end of the current limiting circuit is respectively connected to an input end of the voltage stabilizing circuit and a gate of the second MOS transistor TR2; a source of the second MOS transistor TR2 is connected to an anode of the first diode D1, and a cathode of the first diode D1 is connected to an input end of the startup circuit; an output end of the startup circuit is connected to one end of the first capacitor C1; and an output end of the voltage stabilizing circuit and the other end of the first capacitor C1 are grounded.

[0008] Another embodiment of the startup control circuit includes a current limiting circuit, a startup circuit, a voltage stabilizing circuit, a second MOS transistor TR2, a first capacitor C1 and a first diode D1; the input end of the current limiting circuit inputs the bus voltage, and the output end of the current limiting circuit is respectively connected to the input end of the voltage stabilizing circuit, the gate of the second MOS transistor TR2 and the output end of the startup circuit; the source of the second MOS transistor TR2 is connected to the anode of the first diode D1, and the cathode of the first diode D1 is respectively connected to the input end of the startup circuit and one end of the first capacitor C1; the output end of the voltage stabilizing circuit and the other end of the first capacitor C1 are grounded.

[0009] Furthermore, the startup control circuit also includes a PWM controller and a first MOS transistor TR1, the input end of the PWM controller is connected to the output end of the startup circuit, the output end of the PWM controller is connected to the gate of the first MOS transistor TR1, the drain of the first MOS transistor TR1 is connected to the source of the second MOS transistor TR2, and the source of the first MOS transistor TR1 is grounded.

[0010] Furthermore, the current limiting circuit is one of the following: It includes a first resistor R1, wherein two ends of the first resistor R1 are respectively an input end and an output end of the current limiting circuit; or It includes two or more resistors connected in series, and the two ends of the two or more resistors connected in series are the input end and the output end of the current limiting circuit respectively; or It includes a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a first resistor R1 and a second resistor R2; one end of the fourth capacitor C4 is connected to one end of the first resistor R1 and serves as an input end of the current limiting circuit; the other end of the fourth capacitor C4 is respectively connected to the other end of the first resistor R1, one end of the second capacitor C2 and one end of the second resistor R2; the other end of the second resistor R2 is connected to one end of the third capacitor C3 and serves as an output end of the current limiting circuit; the other end of the second capacitor C2 and the other end of the third capacitor C3 are grounded.

[0011] Furthermore, the starting circuit is one of the following: A third resistor R3 is included, and two ends of the third resistor R3 are respectively used as an input end and an output end of the start-up circuit; or It includes a constant current source U1, the input end of the constant current source U1 is used as the input end of the start-up circuit, and the output end of the constant current source U1 is used as the output end of the start-up circuit; or The invention comprises a linear step-down circuit, wherein the input end of the linear step-down circuit is used as the input end of the starting circuit, and the output end of the linear step-down circuit is used as the output end of the starting circuit.

[0012] Furthermore, the first MOS transistor TR1, the PWM controller and the start-up circuit can be integrated into a control chip.

[0013] Furthermore, the voltage stabilizing circuit is one of the following: A capacitor is included, and the two ends of the capacitor are used as the input end and the output end of the voltage stabilizing circuit respectively; or A voltage regulator diode is included, wherein the cathode of the voltage regulator diode serves as the input end of the voltage regulator circuit, and the anode of the voltage regulator diode serves as the output end of the voltage regulator circuit; or The invention comprises a parallel circuit of a capacitor and a voltage stabilizing diode, wherein one end of the capacitor and the cathode of the voltage stabilizing diode serve as the input end of the voltage stabilizing circuit, and the other end of the capacitor and the anode of the voltage stabilizing diode serve as the output end of the voltage stabilizing circuit.

[0014] The present invention also provides an auxiliary power supply, including the above-mentioned starting control circuit, a transformer T1 and an output rectifier circuit. The input end of the current limiting circuit is connected to one end of the primary main winding of the transformer T1 and serves as the input end of the auxiliary power supply. The drain of the second MOS tube TR2 is connected to the other end of the primary main winding of the transformer T1. The input end of the rectifier circuit is connected to the two ends of the secondary winding of the transformer T1, and the output end of the rectifier circuit serves as a power supply end to power other devices. The transformer T1 also includes an auxiliary winding. One end of the auxiliary winding is grounded, and the other end of the auxiliary winding is connected to the anode of the second diode D2. When the starting control circuit is the first embodiment, the cathode of the second diode D2 is connected to the input end of the PWM controller. When the starting control circuit is the second embodiment, the cathode of the second diode D2 is connected to the input end of the starting circuit or the input end of the PWM controller.

[0015] In the auxiliary power supply and its starting control circuit of the present invention, the input end of the starting circuit is not directly connected to the battery busbar, and the busbar high voltage is mainly borne by the MOS tube TR2, so most of the starting loss is transferred to the MOS tube TR2. The MOS tube TR2 itself is a power MOS with fast heat dissipation, thereby solving the problem of serious heating of the starting circuit in high-voltage input applications, and further improving the capacitive load carrying capacity of the auxiliary power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is one of the auxiliary power supply circuit diagrams in the prior art.

[0017] Figure 2 This is the second auxiliary power supply circuit diagram of the prior art.

[0018] Figure 3 This is a block diagram of a first embodiment of the auxiliary power supply and its startup control circuit of the present invention.

[0019] Figure 4 This is a block diagram of a second embodiment of the auxiliary power supply and its startup control circuit of the present invention.

[0020] Figure 5 The present invention is a block diagram of a resistor used as an auxiliary power supply for a current limiting circuit and a startup control circuit thereof.

[0021] Figure 6 This is a circuit schematic diagram of a second embodiment of the current limiting circuit of the present invention.

[0022] Figure 7 The resistor of the present invention is used as an auxiliary power supply of a starting circuit and a block diagram of a starting control circuit thereof.

[0023] Figure 8 The constant current source of the present invention is used as an auxiliary power supply of a startup circuit and a block diagram of a startup control circuit thereof.

[0024] Fig. 9 The linear voltage regulator of the present invention is used as an auxiliary power supply of a startup circuit and a block diagram of a startup control circuit thereof. DETAILED DESCRIPTION

[0025] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0026] The following describes the embodiments of the present disclosure through specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present disclosure.

[0027] The first embodiment of the auxiliary power startup control circuit of the present invention is as follows: Figure 3 As shown, it includes a current limiting circuit, a starting circuit, a voltage stabilizing circuit, a second MOS tube TR2, a first capacitor C1 and a first diode D1. The input end of the current limiting circuit is connected to the busbar of the battery and the input voltage VIN, and the output end of the current limiting circuit is respectively connected to the input end of the voltage stabilizing circuit and the gate of the second MOS tube TR2. The source of the second MOS tube TR2 is connected to the anode of the first diode D1, and the cathode of the first diode D1 is connected to the input end of the starting circuit. The output end of the starting circuit is connected to one end of the first capacitor C1. The output end of the voltage stabilizing circuit and the other end of the first capacitor C1 are grounded. The voltage stabilizing circuit is used to stabilize the input voltage of the starting circuit at a set value.

[0028] Furthermore, the startup control circuit also includes a PWM controller and a first MOS transistor TR1, the input end of the PWM controller is connected to the output end of the startup circuit, the output end of the PWM controller is connected to the gate of the first MOS transistor TR1, the drain of the first MOS transistor TR1 is connected to the source of the second MOS transistor TR2, and the source of the first MOS transistor TR1 is grounded. The PWM controller and the first MOS transistor TR1 are in the off state during the startup process and do not participate in the work, so they are not necessary technical features of the startup control circuit.

[0029] Figure 3 The working principle is: when VIN is powered on in the startup phase, the voltage at point A gradually rises. When the gate voltage of the second MOS tube TR2 reaches the turn-on threshold V TH_ON When the second MOS tube TR2 is turned on, the current of the startup circuit is small, generally <10mA, and the saturation current of the main power MOS tube TR2 in actual applications is generally >1A. Therefore, the relationship between the voltage at point A and the voltage at point B is approximately as follows: (1) It can be seen from the above formula that the voltage of point B is mainly controlled by the voltage of point A, that is, the voltage of point B is set by controlling the voltage of point A by setting the parameters of the voltage stabilizing circuit. The voltage of capacitor C1 controls whether the PWM controller works. When the voltage on capacitor C1 does not reach the working threshold of PWM control, the PWM controller has not worked yet, no driving signal is issued, and the first MOS tube TR1 is in a closed state and does not participate in the work. In practical applications, the drain of the second MOS tube TR2 is connected to the other end of the primary main winding of the external transformer T1, and the input voltage VIN is input to one end of the primary main winding of the transformer T1. The input voltage VIN charges the first capacitor C1 through the transformer main winding → the second MOS tube TR2 → the first diode D1 → the start-up circuit. In general, the voltage drop between the start-up circuit and the first diode D1 is small, so the voltage at point B is approximately equal to the voltage of the first capacitor C1. In engineering applications, the voltage of the first capacitor C1 is generally <30V. Therefore, most of the voltage drops to the second MOS tube TR2. The second MOS tube TR2 is a power MOS tube and can withstand large losses. Therefore, the beneficial technical effect of the present invention compared with the prior art is reflected: the loss of the startup circuit is transferred to the second MOS transistor TR2.

[0030] When the voltage of the first capacitor C1 reaches the working threshold of the PWM controller, the PWM controller sends a driving signal to control the first MOS tube TR1 to be turned on, and the main power circuit composed of the first MOS tube TR1 and the second MOS tube TR2 starts to work. The primary side of the transformer T1 has a set of auxiliary windings, one end of the auxiliary winding is grounded, and the other end is connected to the anode of the second diode D2, and the cathode of the second diode D2 is connected to the input end of the PWM controller. After the main power circuit starts to work, the current on the auxiliary winding passes through the second diode D2 to supply power to the PWM controller. The auxiliary winding voltage is set relatively high, so that the first diode D1 is reversely cut off, and the path from the second MOS tube TR2→the first diode D1→the start-up circuit is cut off, and the PWM controller is completely powered by the auxiliary winding.

[0031] A second embodiment of the auxiliary power startup control circuit of the present invention is as follows: Figure 4 As shown, it includes a current limiting circuit, a start-up circuit, a voltage stabilizing circuit, a second MOS tube TR2, a first capacitor C1 and a first diode D1. The connection relationship is slightly different from that of the first embodiment. The input end of the current limiting circuit is connected to the busbar of the battery and the input voltage VIN, and the output end of the current limiting circuit is respectively connected to the input end of the voltage stabilizing circuit, the gate of the second MOS tube TR2 and the output end of the start-up circuit. The source of the second MOS tube TR2 is connected to the anode of the first diode D1, and the cathode of the first diode D1 is respectively connected to the input end of the start-up circuit and one end of the first capacitor C1. The output end of the voltage stabilizing circuit and the other end of the first capacitor C1 are grounded.

[0032] Furthermore, the startup control circuit also includes a PWM controller and a first MOS transistor TR1, the input end of the PWM controller is connected to the output end of the startup circuit, the output end of the PWM controller is connected to the gate of the first MOS transistor TR1, the drain of the first MOS transistor TR1 is connected to the source of the second MOS transistor TR2, and the source of the first MOS transistor TR1 is grounded. The PWM controller and the first MOS transistor TR1 are in the off state during the startup process and do not participate in the work, so they are not necessary technical features of the startup control circuit.

[0033] Figure 4 The working principle is: when VIN is powered on in the startup phase, the voltage at point A gradually rises. When the gate voltage of the second MOS tube TR2 reaches the turn-on threshold V TH_ON When the second MOS tube TR2 is turned on, the current of the startup circuit is small, generally <10mA, and the saturation current of the main power MOS tube TR2 in actual applications is generally >1A. Therefore, the relationship between the voltage at point A and the voltage at point B is approximately as follows: (2) And the voltage drop of diode D1 is very small, so the voltage V on capacitor C1 DD Approximately equal to VB . The voltage of capacitor C1 controls whether the PWM controller works. When the voltage on capacitor C1 does not reach the working threshold of PWM control, the input voltage of the PWM controller has not reached its working threshold, so the PWM controller has not worked yet, no driving signal is issued, and the first MOS tube TR1 is in a closed state and does not participate in the work. Similar to the first embodiment, the drain of the second MOS tube TR2 is connected to the other end of the primary main winding of the external transformer T1, and the input voltage VIN is input to one end of the primary main winding of the transformer T1. The input voltage VIN charges the first capacitor C1 through the transformer main winding → the second MOS tube TR2 → the first diode D1. The source voltage of the second MOS tube TR2 is approximately equal to the voltage of the first capacitor C1.

[0034] After the voltage of capacitor C1 reaches the working threshold of the PWM controller, the PWM controller sends a driving signal to control the first MOS tube TR1 to be turned on, and the main power circuit composed of the first MOS tube TR1 and the second MOS tube TR2 starts to work, and the auxiliary winding voltage starts to build up. During the period when the auxiliary winding voltage is built up, the PWM controller is mainly powered by capacitor C1 through the starting circuit, and its power supply loop is capacitor C1→starting circuit→PWM controller. When the auxiliary winding voltage is built up, the PWM controller is mainly powered by the auxiliary winding, and its power supply loop is auxiliary winding→second diode D2→starting circuit→PWM controller. The starting circuit is preferably a linear regulator, because the voltage of the auxiliary winding may be unstable due to the load transformer, output voltage changes, etc., and the voltage finally supplied to the PWM controller is stable after voltage stabilization by the starting circuit.

[0035] Optionally, the voltage of the auxiliary winding can directly power the PWM controller, that is, the cathode of the second diode D2 is directly connected to the input end of the PWM controller, and its power supply loop is auxiliary winding->second diode D2->PWM controller.

[0036] Furthermore, the first MOS transistor TR1, the PWM controller, and the startup circuit can be integrated into a control chip. The technical solution of the present invention can make the integration of the first MOS transistor TR1, the PWM controller, and the startup circuit very easy to realize, and has very high practical value.

[0037] Compared with the starting circuit in the background art, the input end of the starting circuit of the present invention does not need to bear the bus voltage of the battery, and the device that actually bears the bus voltage is the main power MOS tube. The starting circuit does not need to bear high voltage, and the voltage V SIt is stable and will not change with the input voltage VIN, so its design difficulty will be greatly reduced, and the power consumption will decrease in proportion to the voltage at the input end of the startup circuit, making it easier to integrate with the PWM controller and MOS tube TR1, reducing the actual layout area of ​​the entire control circuit. IN ×I VDD , but the startup circuit part is approximately (V B -V DD )×I VDD The rest of the losses are in the main power MOS tube TR2. Generally, the package of the main power MOS tube is larger and has better heat dissipation performance, and may bear greater losses. Therefore, when carrying a larger capacitive load, the heat generation of the startup circuit is also within an acceptable range, thereby improving the capacitive load carrying capacity of the power supply.

[0038] Further, based on the two embodiments of the startup control circuit of the present invention, the current limiting circuit includes a first resistor R1, and the two ends of the first resistor R1 are respectively the input end and the output end of the current limiting circuit. Its function is to limit the current of the voltage stabilizing circuit. In the case of a high input voltage, the current limiting circuit can also be composed of more than two resistors in series. The current limiting circuit formed by multiple resistors in series will occupy a relatively large area. Figure 5 FIG. 1 is a circuit schematic diagram of the first resistor R1 applied to the second embodiment of the auxiliary power startup control circuit. The first resistor R1 is also applicable to the second embodiment of the auxiliary power startup control circuit, and its working principle and role in the startup control circuit are the same, so they are not repeated. The several circuit structures of the startup circuit below are also applicable to the two embodiments of the startup control circuit.

[0039] Furthermore, the current limiting circuit can also be Figure 6 As shown, it includes a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a first resistor R1 and a second resistor R2. One end of the fourth capacitor C4 is connected to one end of the first resistor R1 and serves as the input end of the current limiting circuit. The other end of the fourth capacitor C4 is respectively connected to the other end of the first resistor R1, one end of the second capacitor C2 and one end of the second resistor R2. The other end of the second resistor R2 is connected to one end of the third capacitor C3 and serves as the output end of the current limiting circuit. The other end of the second capacitor C2 and the other end of the third capacitor C3 are grounded.

[0040] The fourth capacitor C4 and the second capacitor C2 are bus capacitors, and the two ends of the series connection are the input voltage (i.e., the bus voltage of the battery). Common large capacitors generally have a withstand voltage value of <500V. Therefore, in applications with an input voltage of >800V, more than two bus capacitors are connected in series, and a resistor is connected in parallel at both ends of the bus capacitor for capacitor voltage balancing, such as Figure 6The third capacitor C3 is used to make the voltage across the second voltage stabilizing diode DZ2 more stable when the power supply is working normally.

[0041] Further, based on the two embodiments of the startup control circuit of the present invention, the startup circuit includes a third resistor R3. Two ends of the third resistor R3 serve as an input end and an output end of the startup circuit respectively. Figure 7 The diagram shows the application of the third resistor R3 in the second embodiment of the auxiliary power supply startup control circuit of the present invention.

[0042] The first diode D1 in this circuit is used to prevent backflow. If there is no first diode D1, when the first MOS transistor TR1 is turned on, the current on the first capacitor C1 will flow from the first MOS transistor TR1 to the ground, causing the VDD voltage to drop. The third resistor R3 is used to limit the current value charged to the first capacitor C1 to prevent excessive transient charging current from causing interference and unpredictable risks.

[0043] Further, based on the two embodiments of the startup control circuit of the present invention, the startup circuit includes a constant current source U1. Figure 8 The second embodiment of the auxiliary power startup control circuit of the present invention is shown in which the constant current source U1 is applied. The input end of the constant current source U1 is used as the input end of the startup circuit, and the output end of the constant current source U1 is used as the output end of the startup circuit. Due to the use of resistor current limiting, in the process of charging the first capacitor C1, the higher the voltage, the smaller the charging current. In this embodiment, the first capacitor C1 is charged by a constant current source, and the charging current is constant, which is not affected by the VDD voltage and is more convenient to use.

[0044] Further, based on the two embodiments of the startup control circuit of the present invention, the startup circuit includes a linear regulator. Fig. 9 The figure shows the application of the linear regulator to the second embodiment of the auxiliary power startup control circuit of the present invention. The input end of the linear regulator is used as the input end of the startup circuit, and the output end of the linear regulator is used as the output end of the startup circuit. The startup circuit adopts the linear regulator, which can further control the output voltage V DD The linear voltage regulator can be implemented in any way in the prior art, and the present invention does not limit the specific form of the linear step-down circuit.

[0045] Further, based on the two embodiments of the startup control circuit of the present invention, the voltage stabilizing circuit can be a capacitor, a voltage stabilizing diode, or a parallel connection of the two: The two ends of the capacitor serve as the input and output of the voltage stabilizing circuit respectively; or The cathode of the voltage stabilizing diode serves as the input terminal of the voltage stabilizing circuit, and the anode of the voltage stabilizing diode serves as the output terminal of the voltage stabilizing circuit; or One end of the capacitor and the cathode of the voltage stabilizing diode serve as the input end of the voltage stabilizing circuit, and the other end of the capacitor and the anode of the voltage stabilizing diode serve as the output end of the voltage stabilizing circuit.

[0046] The present invention also provides an auxiliary power supply, including the above-mentioned starting control circuit, a transformer T1 and an output rectifier circuit. The input end of the current limiting circuit is connected to one end of the primary main winding of the transformer T1 and serves as the input end of the auxiliary power supply. The drain of the second MOS tube TR2 is connected to the other end of the primary main winding of the transformer T1. The input end of the rectifier circuit is connected to the two ends of the secondary winding of the transformer T1, and the output end of the rectifier circuit serves as a power supply end to power other devices. The transformer T1 also includes an auxiliary winding. One end of the auxiliary winding is grounded, and the other end of the auxiliary winding is connected to the anode of the second diode D2. When the starting control circuit is the first embodiment, the cathode of the second diode D2 is connected to the input end of the PWM controller. When the starting control circuit is the second embodiment, the cathode of the second diode D2 is connected to the input end of the starting circuit. The working principle of the auxiliary power supply has been described together with the description of the starting control circuit, and will not be repeated here.

[0047] The above is only for explaining the implementation mode of the present invention and is not intended to limit the present invention. For those skilled in the art, any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention without creative work should be included in the protection scope of the present invention.

Claims

1. A startup control circuit of an auxiliary power supply, characterized in that: The invention comprises a current limiting circuit, a starting circuit, a voltage stabilizing circuit, a second MOS tube (TR2), a first capacitor (C1) and a first diode (D1); the input end of the current limiting circuit inputs a bus voltage, and the output end of the current limiting circuit is respectively connected to the input end of the voltage stabilizing circuit and the gate of the second MOS tube (TR2); the source of the second MOS tube (TR2) is connected to the anode of the first diode (D1), and the cathode of the first diode (D1) is connected to the input end of the starting circuit; the output end of the starting circuit is connected to one end of the first capacitor (C1); the output end of the voltage stabilizing circuit and the other end of the first capacitor (C1) are grounded.

2. A startup control circuit of the auxiliary power supply, characterized in that: The invention comprises a current limiting circuit, a starting circuit, a voltage stabilizing circuit, a second MOS tube (TR2), a first capacitor (C1) and a first diode (D1); the input end of the current limiting circuit inputs a bus voltage, and the output end of the current limiting circuit is respectively connected to the input end of the voltage stabilizing circuit, the gate of the second MOS tube (TR2) and the output end of the starting circuit; the source of the second MOS tube (TR2) is connected to the anode of the first diode (D1), and the cathode of the first diode (D1) is respectively connected to the input end of the starting circuit and one end of the first capacitor (C1); the output end of the voltage stabilizing circuit and the other end of the first capacitor (C1) are grounded.

3. The startup control circuit according to claim 1 or 2, characterized in that: It also includes a PWM controller and a first MOS tube (TR1), wherein the input end of the PWM controller is connected to the output end of the start-up circuit, the output end of the PWM controller is connected to the gate of the first MOS tube (TR1), the drain of the first MOS tube (TR1) is connected to the source of the second MOS tube (TR2), and the source of the first MOS tube (TR1) is grounded.

4. The startup control circuit according to claim 1 or 2, characterized in that: The current limiting circuit is one of the following: comprising a first resistor (R1), wherein two ends of the first resistor (R1) are respectively an input end and an output end of a current limiting circuit; or It includes two or more resistors connected in series, and the two ends of the two or more resistors connected in series are the input end and the output end of the current limiting circuit respectively; or The invention comprises a second capacitor (C2), a third capacitor (C3), a fourth capacitor (C4), a first resistor (R1) and a second resistor (R2); one end of the fourth capacitor (C4) is connected to one end of the first resistor (R1) and serves as an input end of a current limiting circuit; the other end of the fourth capacitor (C4) is respectively connected to the other end of the first resistor (R1), one end of the second capacitor (C2) and one end of the second resistor (R2); the other end of the second resistor (R2) is connected to one end of the third capacitor (C3) and serves as an output end of the current limiting circuit; the other end of the second capacitor (C2) and the other end of the third capacitor (C3) are grounded.

5. The startup control circuit according to claim 1 or 2, characterized in that: The starting circuit is one of the following: comprising a third resistor (R3), wherein two ends of the third resistor (R3) serve as an input end and an output end of the start-up circuit respectively; or comprising a constant current source (U1), wherein the input end of the constant current source (U1) serves as the input end of the start-up circuit, and the output end of the constant current source (U1) serves as the output end of the start-up circuit; or The invention comprises a linear step-down circuit, wherein the input end of the linear step-down circuit is used as the input end of the starting circuit, and the output end of the linear step-down circuit is used as the output end of the starting circuit.

6. The startup control circuit according to claim 3, characterized in that: The first MOS tube (TR1), the PWM controller and the start-up circuit can be integrated into a control chip.

7. The startup control circuit according to claim 1 or 2, characterized in that: The voltage stabilization circuit is one of the following: A capacitor is included, and the two ends of the capacitor are used as the input end and the output end of the voltage stabilizing circuit respectively; or A voltage regulator diode is included, wherein the cathode of the voltage regulator diode serves as the input end of the voltage regulator circuit, and the anode of the voltage regulator diode serves as the output end of the voltage regulator circuit; or The invention comprises a parallel circuit of a capacitor and a voltage stabilizing diode, wherein one end of the capacitor and the cathode of the voltage stabilizing diode serve as the input end of the voltage stabilizing circuit, and the other end of the capacitor and the anode of the voltage stabilizing diode serve as the output end of the voltage stabilizing circuit.

8. An auxiliary power supply, comprising a transformer and an output rectifier circuit, characterized in that: It also includes the starting control circuit as claimed in claim 1; the input end of the current limiting circuit is connected to one end of the primary main winding of the transformer and serves as the input end of the auxiliary power supply; the drain of the second MOS tube (TR2) is connected to the other end of the primary main winding of the transformer; the input end of the rectifier circuit is connected to the two ends of the secondary winding of the transformer, and the output end of the rectifier circuit serves as the power supply end to power other devices; the transformer also includes an auxiliary winding, one end of the auxiliary winding is grounded, the other end of the auxiliary winding is connected to the anode of the second diode (D2), and the cathode of the second diode (D2) is connected to the input end of the PWM controller.

9. An auxiliary power supply, comprising a transformer and an output rectifier circuit, characterized in that: It also includes the starting control circuit as claimed in claim 2; the input end of the current limiting circuit is connected to one end of the primary main winding of the transformer and serves as the input end of the auxiliary power supply; the drain of the second MOS tube (TR2) is connected to the other end of the primary main winding of the transformer; the input end of the rectifier circuit is connected to the two ends of the secondary winding of the transformer, and the output end of the rectifier circuit serves as the power supply end to power other devices; the transformer also includes an auxiliary winding, one end of the auxiliary winding is grounded, the other end of the auxiliary winding is connected to the anode of the second diode (D2), and the cathode of the second diode (D2) is connected to the input end of the starting circuit or the input end of the PWM controller.

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