A power supply starting circuit and BUCK structure power supply

Abstract

The present application provides a power startup circuit and a BUCK structure power supply, wherein the power startup circuit is applied to a BUCK structure power supply, and comprises: a switching power supply module, which adjusts and outputs a first voltage according to an input bus voltage; a voltage stabilizing module, which is connected to the switching power supply module and outputs a second voltage based on the first voltage through voltage stabilization; and a voltage dividing module, which is connected to the voltage stabilizing module and divides the second voltage to output a first startup voltage, so that the BUCK structure power supply starts working according to the first startup voltage. The present application solves the startup problem of the BUCK structure power supply through a circuit with a simple structure and low cost.

Description

Technical Field

[0001] The present application belongs to the technical field of power supply design, and relates to a starting circuit, and in particular to a power supply starting circuit and a BUCK structure power supply. Background Art

[0002] With the continuous advancement of electronic systems, electronic and electrical equipment occupy an increasingly important position in daily life. At the same time, the harmonic pollution caused to the power grid is also increasing. Power Factor Correction (PFC) technology is an effective way to improve the power factor of electronic equipment, reduce harmonic distortion, reduce power grid pollution, and improve energy utilization. Therefore, the PFC technology of power supply chips has become one of the focuses of attention and research in the current electronics field.

[0003] Among them, active power factor correction (APFC) technology can not only improve power factor and reduce total harmonic distortion, but also is widely used due to its advantages such as large input voltage range, simple structure and high efficiency. Modern PFC technology is different from power factor compensation. It targets non-sinusoidal current waveform distortion. The AC line current tracks the instantaneous change trajectory of the voltage waveform. The current and voltage remain in phase, and the system is purely resistive. Therefore, the startup circuit design of the PFC power supply is crucial. Summary of the invention

[0004] The present application provides a power supply startup circuit and a BUCK structure power supply, which are used to solve the startup circuit design problem of a PFC power supply.

[0005] In a first aspect, the present application provides a power startup circuit, which is applied to a BUCK structure power supply, and the circuit includes: a switching power supply module, which adjusts and outputs a first voltage according to an input bus voltage; a voltage stabilizing module, which is connected to the switching power supply module and outputs a second voltage based on the first voltage through stabilization; and a voltage dividing module, which is connected to the voltage stabilizing module and divides the second voltage to output a first startup voltage, so that the BUCK structure power supply starts working according to the first startup voltage.

[0006] In an implementation of the first aspect, the switching power supply module includes a switch driving chip and a first charging capacitor; a voltage input pin of the switch driving chip is connected to the first charging capacitor, and in response to the bus voltage reaching the minimum starting voltage of the switch driving chip, an internal high-voltage starting circuit of the switch driving chip charges the first charging capacitor connected to the voltage input pin through the bus voltage input terminal; in response to the voltage of the first charging capacitor reaching the starting threshold of the switch driving chip, an internal control circuit of the switch driving chip starts working.

[0007] In an implementation of the first aspect, the switching power supply module further includes a freewheeling diode, a feedback diode and a second charging capacitor; the anode of the freewheeling diode is connected to the negative electrode of the bus, the cathode is connected to the ground pin of the switch driver chip, the anode of the feedback diode is connected to the output end of the first voltage, and the cathode is connected to the positive electrode of the second charging capacitor; in response to the internal control circuit of the switch driver chip starting to work, during the conduction period of the freewheeling diode, the output voltage of the switch driver chip charges the second charging capacitor through the feedback diode, so that the voltage of the second charging capacitor is equal to the output voltage of the switch driver chip.

[0008] In an implementation of the first aspect, the switching power supply module also includes a first voltage-dividing resistor and a second voltage-dividing resistor; one end of the first voltage-dividing resistor is connected to the cathode of the feedback diode, and the other end is connected to one end of the second voltage-dividing resistor, the connection point of the first voltage-dividing resistor and the second voltage-dividing resistor is connected to the feedback end of the switch driving chip, and the other end of the second voltage-dividing resistor is connected to the negative electrode of the second charging capacitor; the voltage of the voltage-dividing point of the first voltage-dividing resistor and the second voltage-dividing resistor is compared with the internal reference voltage of the feedback end of the switch driving chip, and the error signal generated by the comparison is amplified inside the switch driving chip to determine the peak current and the switching frequency to adjust the output voltage.

[0009] In an implementation of the first aspect, the voltage stabilizing module includes a recovery diode and a voltage stabilizing chip; the anode of the recovery diode is connected to the output end of the switching power supply module, the cathode of the recovery diode is connected to the input end of the voltage stabilizing chip, and the output end of the voltage stabilizing chip outputs the second voltage.

[0010] In an implementation of the first aspect, the voltage divider module includes a third voltage divider resistor, a fourth voltage divider resistor and a voltage follower; one end of the third voltage divider resistor inputs the second voltage, and the other end is connected to one end of the fourth voltage divider resistor, the other end of the fourth voltage divider resistor is connected to the negative pole of the bus, and one end of the fourth voltage divider resistor is also connected to the voltage follower, and the voltage follower outputs the first startup voltage of the BUCK structure power supply.

[0011] In an implementation manner of the first aspect, the voltage divider module further includes a first diode; an anode of the first diode is connected to an output end of the voltage follower, and a cathode of the first diode outputs the first starting voltage.

[0012] In an implementation of the first aspect, the circuit further includes: a differential amplifier module; the differential amplifier module is connected to the BUCK structure power supply, scales down the voltage output by the BUCK structure power supply, and outputs a second startup voltage.

[0013] In an implementation manner of the first aspect, the differential amplification module includes a differential amplifier and a second diode; an anode of the second diode is connected to an output end of the differential amplifier, and a cathode outputs the second starting voltage.

[0014] In a second aspect, the present application provides a BUCK structure power supply, the power supply comprising: the power supply starting circuit.

[0015] As described above, the power startup circuit and BUCK structure power supply described in this application have the following beneficial effects:

[0016] The power startup circuit designed in the present application is applied to a BUCK structure power supply, including: a switching power supply module, which adjusts and outputs a first voltage according to the input bus voltage; a voltage stabilizing module, which is connected to the switching power supply module and outputs a second voltage based on the first voltage; a voltage dividing module, which is connected to the voltage stabilizing module and divides the second voltage to output a first startup voltage, so that the BUCK structure power supply starts working according to the first startup voltage. The present application solves the startup problem of the BUCK structure power supply through a circuit with a simple structure and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Shown is a schematic diagram of the structural connection of the power startup circuit described in an embodiment of the present application.

[0018] Figure 2 Shown is a circuit structure diagram of a switching power supply module of a power startup circuit described in an embodiment of the present application.

[0019] Figure 3 Shown is a circuit structure diagram of a voltage regulator module of a power startup circuit described in an embodiment of the present application.

[0020] Figure 4 Shown is a circuit structure diagram of a voltage divider module of a power startup circuit described in an embodiment of the present application.

[0021] Figure 5 Shown is another structural connection schematic diagram of the power startup circuit described in an embodiment of the present application.

[0022] Figure 6 Shown is a circuit structure diagram of a differential amplifier module of a power startup circuit described in an embodiment of the present application.

[0023] Figure 7Shown is a circuit diagram of the BUCK structure power supply described in an embodiment of the present application.

[0024] Component number description

[0025] 1 Power start circuit

[0026] 11 Switching power supply module

[0027] 12 Voltage regulator module

[0028] 13 Voltage divider module

[0029] 14 Differential amplifier module DETAILED DESCRIPTION

[0030] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application 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 application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0031] It should be noted that the illustrations provided in the following embodiments are only used to illustrate the basic concept of the present application in a schematic manner, and therefore the illustrations only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0032] The technical solutions in the embodiments of the present application will be described in detail below in conjunction with the drawings in the embodiments of the present application.

[0033] See also Figure 1 , which is a schematic diagram showing the structural connection of the power startup circuit described in the embodiment of the present application. Figure 1 As shown, this embodiment provides a power startup circuit 1 applied to a BUCK structure power supply, including: a switching power supply module 11, a voltage stabilizing module 12 and a voltage dividing module 13.

[0034] The switching power supply module 11 adjusts and outputs a first voltage according to an input bus voltage.

[0035] The voltage stabilizing module 12 is connected to the switching power supply module 11 and outputs a second voltage by stabilizing the first voltage.

[0036] The voltage dividing module 13 is connected to the voltage stabilizing module 12, divides the second voltage, and outputs a first starting voltage, so that the BUCK structure power supply starts to work according to the first starting voltage.

[0037] In one embodiment, the switching power supply module includes a switch driving chip and a first charging capacitor.

[0038] The voltage input pin of the switch driving chip is connected to the first charging capacitor. In response to the bus voltage reaching the minimum starting voltage of the switch driving chip, the internal high-voltage starting circuit of the switch driving chip charges the first charging capacitor connected to the voltage input pin through the bus voltage input terminal; in response to the voltage of the first charging capacitor reaching the starting threshold of the switch driving chip, the internal control circuit of the switch driving chip starts to work.

[0039] See also Figure 2 , which shows a circuit structure diagram of a switch power module of a power startup circuit according to an embodiment of the present application. Figure 2 As shown, the switching power supply module 11 includes a switch driving chip U4 and a first charging capacitor C26. The voltage input pin VCC of the switch driving chip U4 is connected to the first charging capacitor C26. In response to the bus voltage (+) reaching the minimum starting voltage of the switch driving chip U4, the internal high-voltage starting circuit of the switch driving chip U4 charges the first charging capacitor C26 connected to the voltage input pin VCC through the bus voltage input terminal DRAIN; in response to the voltage of the first charging capacitor C26 reaching the starting threshold of the switch driving chip U4, the internal control circuit of the switch driving chip U4 starts to work.

[0040] In one embodiment, the switching power supply module also includes a freewheeling diode, a feedback diode and a second charging capacitor; the anode of the freewheeling diode is connected to the negative electrode of the bus, and the cathode is connected to the ground pin of the switch driver chip; the anode of the feedback diode is connected to the output end of the first voltage, and the cathode is connected to the positive electrode of the second charging capacitor.

[0041] In response to the internal control circuit of the switch driver chip starting to work, during the conduction period of the freewheeling diode, the output voltage of the switch driver chip charges the second charging capacitor through the feedback diode, so that the voltage of the second charging capacitor is equal to the output voltage of the switch driver chip.

[0042] like Figure 2As shown, the switch power supply module 11 also includes a flyback diode D16, a feedback diode D17 and a second charging capacitor E27; the anode of the flyback diode D16 is connected to the negative electrode of the busbar, and the cathode is connected to the ground pin of the switch driver chip U4; the anode of the feedback diode D17 is connected to the output end 18.7V of the first voltage, and the cathode is connected to the positive electrode of the second charging capacitor E27. In response to the internal control circuit of the switch driver chip U4 starting to work, during the conduction period of the flyback diode D16, the output voltage of the switch driver chip U4 charges the second charging capacitor E27 through the feedback diode D17, so that the voltage of the second charging capacitor E27 is equal to the output voltage of the switch driver chip U4.

[0043] In one embodiment, the switching power supply module also includes a first voltage-dividing resistor and a second voltage-dividing resistor; one end of the first voltage-dividing resistor is connected to the cathode of the feedback diode, and the other end is connected to one end of the second voltage-dividing resistor, the connection point between the first voltage-dividing resistor and the second voltage-dividing resistor is connected to the feedback end of the switch driving chip, and the other end of the second voltage-dividing resistor is connected to the negative electrode of the second charging capacitor.

[0044] The voltage at the dividing point of the first dividing resistor and the second dividing resistor is compared with the internal reference voltage at the feedback end of the switch driver chip. The error signal generated by the comparison is amplified inside the switch driver chip to determine the peak current and the switching frequency to adjust the output voltage.

[0045] like Figure 2 As shown, the switching power supply module 11 also includes a first voltage-dividing resistor R60 and a second voltage-dividing resistor R57; one end of the first voltage-dividing resistor R60 is connected to the cathode of the feedback diode D17, and the other end is connected to one end of the second voltage-dividing resistor R57, the connection point between the first voltage-dividing resistor R60 and the second voltage-dividing resistor R57 is connected to the feedback terminal FB of the switch driver chip, and the other end of the second voltage-dividing resistor R57 is connected to the negative electrode of the second charging capacitor E27. The voltage at the voltage-dividing point between the first voltage-dividing resistor R60 and the second voltage-dividing resistor R57 is compared with the internal reference voltage of the feedback terminal FB of the switch driver chip U4, and the error signal generated by the comparison is amplified by the switch driver chip U4 to determine the peak current and the switching frequency, so as to adjust the output voltage.

[0046] Specifically, chip U4 uses BPA8504D chip as non-isolated BUCK. BPA8504D is a high-performance, highly integrated, low standby power consumption switch driver chip. The chip integrates a 650V power switch, a high-voltage self-powered circuit, a current sampling circuit, and a wealth of protection functions. After the system is powered on, the bus voltage rises. When the bus voltage reaches the minimum starting voltage of 40V, the internal high-voltage startup circuit charges the VCC terminal capacitor C26 through the DRAIN terminal. When the voltage of the VCC terminal capacitor C26 reaches the chip startup threshold (6.4V), the internal control circuit of the chip starts to work. During the conduction of the freewheeling diode D16, the output voltage charges the feedback capacitor E27 through the feedback diode D17, so that the feedback capacitor E27 is equal to the output voltage. After the voltage is divided by the external voltage-dividing resistors R57 and R60, it is compared with the internal reference voltage. The error signal generated is amplified and controls the peak current and switching frequency. The output voltage Vout is thereby adjusted. The resistor R57 is 1K and the resistor R60 is 10K, so the output voltage is adjusted to 1.7*(R57+R60) / R57=18.7V.

[0047] It should be noted that BPA8504D is only one implementation of the switching power supply module of the present application. Other switch driver chips such as LA4291 that can withstand high voltage input and can step down the voltage are all within the scope of protection of the present application.

[0048] In one embodiment, the voltage stabilizing module includes a recovery diode and a voltage stabilizing chip.

[0049] The anode of the recovery diode is connected to the output end of the switching power supply module, the cathode of the recovery diode is connected to the input end of the voltage stabilizing chip, and the output end of the voltage stabilizing chip outputs the second voltage.

[0050] See also Figure 3 , which is a circuit structure diagram of a voltage regulator module of a power startup circuit according to an embodiment of the present application. Figure 3 As shown, the voltage stabilizing module 12 includes a recovery diode D18 and a voltage stabilizing chip U5. The anode of the recovery diode D18 is connected to the output end of the switching power supply module 11, the cathode of the recovery diode D18 is connected to the input end of the voltage stabilizing chip U5, and the output end of the voltage stabilizing chip U5 outputs the second voltage 15V.

[0051] Specifically, the 18.7V voltage is sent to the MC7815 chip after passing through the D18 ultra-fast recovery diode. The MC7815 is a three-terminal voltage regulator chip. The output current can exceed 1A. The output voltage is 15V.

[0052] It should be noted that MC7815 is only one implementation of the voltage stabilizing module of the present application. Other voltage stabilizing chips such as ME7815 and BL7815, which have an output voltage of 15V and an output current greater than 1A, are all within the scope of protection of the present application.

[0053] In one embodiment, the voltage dividing module includes a third voltage dividing resistor, a fourth voltage dividing resistor and a voltage follower.

[0054] One end of the third voltage-dividing resistor inputs the second voltage, and the other end is connected to one end of the fourth voltage-dividing resistor, the other end of the fourth voltage-dividing resistor is connected to the negative electrode of the bus, and one end of the fourth voltage-dividing resistor is also connected to the voltage follower, and the voltage follower outputs the first startup voltage of the BUCK structure power supply.

[0055] See also Figure 4 , which is a circuit structure diagram of a voltage divider module of a power startup circuit according to an embodiment of the present application. Figure 4 As shown, the voltage divider module 13 includes a third voltage divider resistor R32, a fourth voltage divider resistor R56 and a voltage follower U1B. One end of the third voltage divider resistor R32 inputs the second voltage 15V, and the other end is connected to one end of the fourth voltage divider resistor R56, the other end of the fourth voltage divider resistor R56 is connected to the bus negative electrode (-), one end of the fourth voltage divider resistor R56 is also connected to the voltage follower U1B, and the voltage follower U1B outputs the first startup voltage VSENSE_A of the BUCK structure power supply.

[0056] In one embodiment, the voltage dividing module further includes a first diode.

[0057] The anode of the first diode is connected to the output end of the voltage follower, and the cathode outputs the first starting voltage.

[0058] like Figure 4 As shown, the voltage dividing module 13 further includes a first diode D15. The anode of the first diode D15 is connected to the output end of the voltage follower U1B, and the cathode outputs the first start-up voltage VSENSE_A.

[0059] Specifically, the 15V voltage is divided by R32 and R56 to obtain 0.79V. After passing through the voltage follower built by SGM8270, VSENSE_A outputs a voltage of 0.79V. 0.79V is greater than 0.75V, so that the PFC power supply chip UC28070 starts to work.

[0060] See also Figure 5 , which is another structural connection diagram of the power startup circuit described in the embodiment of the present application. Figure 5As shown, the circuit further includes: a differential amplifier module 14.

[0061] The differential amplifier module 15 is connected to the BUCK structure power supply, scales down the voltage output by the BUCK structure power supply, and outputs a second starting voltage.

[0062] In one embodiment, the differential amplifier module includes a differential amplifier and a second diode.

[0063] The anode of the second diode is connected to the output end of the differential amplifier, and the cathode of the second diode outputs the second starting voltage.

[0064] See also Figure 6 , which is a circuit structure diagram of a differential amplifier module of a power startup circuit according to an embodiment of the present application. Figure 6 As shown, the differential amplifier module 14 includes a differential amplifier U1A and a second diode D14. The anode of the second diode D14 is connected to the output end of the differential amplifier U1A, and the cathode outputs the second start-up voltage VSENSE_B.

[0065] Specifically, the PFC power supply output voltage is 75V. 75V is converted to 3.2V by the differential amplifier circuit built by SGM8270. The output voltage of VSENSE_A rises from 0.79V to 3.2V. In order to distinguish it from 0.79V of VSENSE_A, 3.2V is named as the second startup voltage VSENSE_B, and the UC28070 chip circuit continues to work normally. The outputs of the voltage follower and the differential amplifier circuit will not affect each other. Because of the presence of D14 and D15 diodes, the diodes have unidirectional conductivity.

[0066] It should be noted that SGM8270 is only one of the implementations of the voltage follower and differential amplifier of the present application. Other operational amplifier chips such as TP1242, LTA8062, etc. that can be powered by a single power supply and are designed with a rail-to-rail structure are all within the scope of protection of the present application.

[0067] The present application also provides a BUCK structure power supply, which includes: the above-mentioned power supply starting circuit.

[0068] The power startup circuit includes: a switching power supply module, which adjusts and outputs a first voltage according to an input bus voltage; a voltage stabilizing module, which is connected to the switching power supply module and outputs a second voltage based on the first voltage through voltage stabilization; and a voltage dividing module, which is connected to the voltage stabilizing module and divides the second voltage to output a first startup voltage, so that the BUCK structure power supply starts working according to the first startup voltage.

[0069] like Figure 2As shown, the switching power supply module 11 includes a switch driving chip U4 and a first charging capacitor C26. The voltage input pin VCC of the switch driving chip U4 is connected to the first charging capacitor C26. In response to the bus voltage (+) reaching the minimum starting voltage of the switch driving chip U4, the internal high-voltage starting circuit of the switch driving chip U4 charges the first charging capacitor C26 connected to the voltage input pin VCC through the bus voltage input terminal DRAIN; in response to the voltage of the first charging capacitor C26 reaching the starting threshold of the switch driving chip U4, the internal control circuit of the switch driving chip U4 starts to work.

[0070] like Figure 2 As shown, the switch power supply module 11 also includes a flyback diode D16, a feedback diode D17 and a second charging capacitor E27; the anode of the flyback diode D16 is connected to the negative electrode of the busbar, and the cathode is connected to the ground pin of the switch driver chip U4; the anode of the feedback diode D17 is connected to the output end 18.7V of the first voltage, and the cathode is connected to the positive electrode of the second charging capacitor E27. In response to the internal control circuit of the switch driver chip U4 starting to work, during the conduction period of the flyback diode D16, the output voltage of the switch driver chip U4 charges the second charging capacitor E27 through the feedback diode D17, so that the voltage of the second charging capacitor E27 is equal to the output voltage of the switch driver chip U4.

[0071] like Figure 2 As shown, the switching power supply module 11 also includes a first voltage-dividing resistor R60 and a second voltage-dividing resistor R57; one end of the first voltage-dividing resistor R60 is connected to the cathode of the feedback diode D17, and the other end is connected to one end of the second voltage-dividing resistor R57, the connection point between the first voltage-dividing resistor R60 and the second voltage-dividing resistor R57 is connected to the feedback terminal FB of the switch driver chip, and the other end of the second voltage-dividing resistor R57 is connected to the negative electrode of the second charging capacitor E27. The voltage at the voltage-dividing point between the first voltage-dividing resistor R60 and the second voltage-dividing resistor R57 is compared with the internal reference voltage of the feedback terminal FB of the switch driver chip U4, and the error signal generated by the comparison is amplified by the switch driver chip U4 to determine the peak current and the switching frequency, so as to adjust the output voltage.

[0072] like Figure 3 As shown, the voltage stabilizing module 12 includes a recovery diode D18 and a voltage stabilizing chip U5. The anode of the recovery diode D18 is connected to the output end of the switching power supply module 11, the cathode of the recovery diode D18 is connected to the input end of the voltage stabilizing chip U5, and the output end of the voltage stabilizing chip U5 outputs the second voltage 15V.

[0073] like Figure 4 As shown, the voltage divider module 13 includes a third voltage divider resistor R32, a fourth voltage divider resistor R56 and a voltage follower U1B. One end of the third voltage divider resistor R32 inputs the second voltage 15V, and the other end is connected to one end of the fourth voltage divider resistor R56, the other end of the fourth voltage divider resistor R56 is connected to the bus negative electrode (-), one end of the fourth voltage divider resistor R56 is also connected to the voltage follower U1B, and the voltage follower U1B outputs the first startup voltage VSENSE_A of the BUCK structure power supply.

[0074] like Figure 4 As shown, the voltage dividing module 13 further includes a first diode D15. The anode of the first diode D15 is connected to the output end of the voltage follower U1B, and the cathode outputs the first start-up voltage VSENSE_A.

[0075] like Figure 5 As shown, the circuit further includes: a differential amplifier module 14. The differential amplifier module 15 is connected to the BUCK structure power supply, scales down the voltage output by the BUCK structure power supply, and outputs a second starting voltage.

[0076] like Figure 6 As shown, the differential amplifier module 14 includes a differential amplifier U1A and a second diode D14. The anode of the second diode D14 is connected to the output end of the differential amplifier U1A, and the cathode outputs the second start-up voltage VSENSE_B.

[0077] See also Figure 7 , which shows the circuit structure diagram of the BUCK structure power supply described in the embodiment of the present application. Figure 7As shown, specifically, the BUCK structure power supply is a BUCK type PFC power supply, and the PFC power supply chip U8 can be UCC28070. In addition to the 4th pin of UCC28070, namely the VSENSE pin, which is connected to the power supply startup circuit of this application, the peripheral circuits of other pins of UCC28070 can be designed according to the circuit connection method such as the chip data manual. This application designs a BUCK type interleaved PFC power supply through UCC28070. UCC28070 is an advanced power factor correction device that integrates two interleaved PWMs working at 180° anti-phase. Because the input voltage, such as the mains, is a periodically changing value, the range of the mains is about -311-311V, and after full-wave rectification, the range is from 0 to 311, and the output is a basically stable DC voltage. If BUCK is used as a PFC power supply, when the input voltage is less than the output, it is impossible to let the current flow from the input end to the output end, and the power factor cannot be close to 1. Moreover, the startup circuit is not easy to make and the cost is high. Therefore, the mainstream in the market is still BOOST PFC. However, the loss of BOOST PFC is greater than that of BUCK PFC. BUCK PFC still has a lot of room for development. UCC28070 is usually used as a BOOST PFC power supply. At present, there is no BUCK PFC power supply made of UCC28070 on the market. The startup circuit is a very important part of the BUCK PFC power supply. Without the startup circuit, the BUCK PFC power supply cannot work. In actual applications, the 4th pin of UCC28070, the VSENSE pin, must reach a voltage of 0.75V or above before the PFC function starts to work. Therefore, the BUCK structure power supply composed of UCC28070 in this application must first output a voltage of more than 0.75V through the startup circuit to enable UCC28070 to work normally.

[0078] Specifically, combined Figure 4 , 15V voltage is divided by R32 and R56 to get 0.79V. After passing through the voltage follower built by SGM8270, VSENSE_A outputs 0.79V voltage to the 4th pin of UCC28070, which is VSENSE pin. 0.79V is greater than 0.75V, and UC28070 chip starts to work.

[0079] Furthermore, the output voltage of the BUCK structure PFC power supply is 75V. 75V is converted to 3.2V through the differential amplifier circuit built by SGM8270. The output voltage of VSENSE_A rises from 0.79V to 3.2V. In order to distinguish it from the 0.79V of VSENSE_A, 3.2V is named the second startup voltage VSENSE_B. VSENSE_B outputs 3.2V voltage to the 4th pin of UCC28070, namely the VSENSE pin. 3.2V is greater than 0.75V, and the circuit continues to work normally. Because of the presence of D14 and D15 diodes, the diodes have unidirectional conductivity. The outputs of the voltage follower and the differential amplifier circuit will not affect each other.

[0080] It should be noted that UCC28070 is only one of the implementations of this application to illustrate the implementation principle of the power startup circuit applied to the BUCK structure power supply. Other chip solutions such as NCP1632A, R2A20114BFP, etc. have similar functions to UCC28070 and can implement the power startup circuit of this application and the BUCK structure power supply principle are all within the scope of protection of this application.

[0081] It should be noted that Figures 2 to 4 and Figure 6 , Figure 7 The resistors and capacitors involved in the invention can determine different numbers of capacitors and resistors based on output power, resistor power, and cost, while keeping the implementation principle of the power startup circuit and the BUCK structure power supply of the present application unchanged.

[0082] In the several embodiments provided in the present application, it should be understood that the disclosed circuits can be implemented in other ways. For example, the circuit embodiments described above are only schematic, for example, the division of modules / units is only a logical function division, and there may be other division methods in actual implementation, such as multiple modules or units can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or modules or units, which can be electrical, mechanical or other forms.

[0083] The modules / units described as separate components may or may not be physically separated, and the components displayed as modules / units may or may not be physical modules, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules / units may be selected according to actual needs to achieve the purpose of the embodiments of the present application. For example, the functional modules / units in the various embodiments of the present application may be integrated into one processing module, or each module / unit may exist physically separately, or two or more modules / units may be integrated into one module / unit.

[0084] The above embodiments are merely illustrative of the principles and effects of the present application and are not intended to limit the present application. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present application shall still be covered by the claims of the present application.

Claims

1. A power startup circuit, characterized in that: Applied to a BUCK structure power supply, the circuit includes: A switching power supply module adjusts and outputs a first voltage according to an input bus voltage; A voltage stabilizing module, connected to the switching power supply module, and stabilizing and outputting a second voltage based on the first voltage; The voltage dividing module is connected to the voltage stabilizing module, divides the second voltage, and outputs a first starting voltage, so that the BUCK structure power supply starts to work according to the first starting voltage.

2. The circuit according to claim 1, characterized in that The switching power supply module includes a switch driving chip and a first charging capacitor; The voltage input pin of the switch driving chip is connected to the first charging capacitor, and in response to the bus voltage reaching the minimum starting voltage of the switch driving chip, the internal high-voltage starting circuit of the switch driving chip charges the first charging capacitor connected to the voltage input pin through the bus voltage input terminal; In response to the voltage of the first charging capacitor reaching a start-up threshold of the switch driving chip, an internal control circuit of the switch driving chip starts to operate.

3. The circuit according to claim 2, characterized in that The switching power supply module further includes a freewheeling diode, a feedback diode and a second charging capacitor; the anode of the freewheeling diode is connected to the negative electrode of the busbar, the cathode is connected to the ground pin of the switch driving chip, the anode of the feedback diode is connected to the output end of the first voltage, and the cathode is connected to the positive electrode of the second charging capacitor; In response to the internal control circuit of the switch driver chip starting to work, during the conduction period of the freewheeling diode, the output voltage of the switch driver chip charges the second charging capacitor through the feedback diode, so that the voltage of the second charging capacitor is equal to the output voltage of the switch driver chip.

4. The circuit according to claim 3, characterized in that The switching power supply module further includes a first voltage-dividing resistor and a second voltage-dividing resistor; one end of the first voltage-dividing resistor is connected to the cathode of the feedback diode, and the other end is connected to one end of the second voltage-dividing resistor, the connection point between the first voltage-dividing resistor and the second voltage-dividing resistor is connected to the feedback end of the switch driving chip, and the other end of the second voltage-dividing resistor is connected to the negative electrode of the second charging capacitor; The voltage at the dividing point of the first dividing resistor and the second dividing resistor is compared with the internal reference voltage at the feedback end of the switch driver chip. The error signal generated by the comparison is amplified inside the switch driver chip to determine the peak current and the switching frequency to adjust the output voltage.

5. The circuit according to claim 1, characterized in that The voltage stabilizing module includes a recovery diode and a voltage stabilizing chip; The anode of the recovery diode is connected to the output end of the switching power supply module, the cathode of the recovery diode is connected to the input end of the voltage stabilizing chip, and the output end of the voltage stabilizing chip outputs the second voltage.

6. The circuit according to claim 1, characterized in that The voltage dividing module includes a third voltage dividing resistor, a fourth voltage dividing resistor and a voltage follower; One end of the third voltage-dividing resistor inputs the second voltage, and the other end is connected to one end of the fourth voltage-dividing resistor, the other end of the fourth voltage-dividing resistor is connected to the negative electrode of the bus, and one end of the fourth voltage-dividing resistor is also connected to the voltage follower, and the voltage follower outputs the first startup voltage of the BUCK structure power supply.

7. The circuit according to claim 6, characterized in that The voltage dividing module also includes a first diode; The anode of the first diode is connected to the output end of the voltage follower, and the cathode outputs the first starting voltage.

8. The circuit according to claim 1, characterized in that The circuit further comprises: a differential amplification module; The differential amplifier module is connected to the BUCK structure power supply, scales down the voltage output by the BUCK structure power supply, and outputs a second starting voltage.

9. The circuit according to claim 8, characterized in that The differential amplifier module includes a differential amplifier and a second diode; The anode of the second diode is connected to the output end of the differential amplifier, and the cathode of the second diode outputs the second starting voltage.

10. A BUCK structure power supply, characterized in that: The power supply comprises: the circuit according to any one of claims 1 to 9.

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