Switching power supply

Abstract

The invention discloses a switching power supply which comprises an anti-surge unit, an input end comprises a surge switch unit and a power switch device which are connected in parallel, a first connection point and a second connection point are formed, and the surge switch unit comprises a thermistor and a surge switch device which are connected in series; the power factor correction unit is electrically connected with the second connection point; the control unit is electrically connected with the power switch device and the surge switch device. The first connection point is electrically connected with the live wire input end of the switching power supply, and the power factor correction unit is electrically connected with the zero line input end of the switching power supply, or the first connection point is electrically connected with the zero line input end, and the power factor correction unit is electrically connected with the live wire input end; in the initial stage of starting of the switching power supply, the power switching device and the surge switching device are both switched off; in the first stage, the input side voltage is normal, and the control unit controls the surge switching device to be closed; in the second stage, voltages at two ends of the power switching device are smaller than preset voltages, the power switching device is controlled to be closed, and the switching power supply is normally started to work.

Description

Technical Field

[0001] The present application relates to the technical field of electronic circuits, and in particular to a switching power supply. Background Art

[0002] A switching power supply is a power supply device that converts AC to DC. It has the characteristics of high efficiency, small size, light weight, and good stability. It switches the input voltage into a pulse signal through the switching action of the switching tube and uses a high frequency, and converts it into a DC voltage output through a rectifier and filtering circuit.

[0003] When the switching power supply is turned on, the large electrolytic capacitor storing energy on the primary side is in a short-circuit state, and the resistance is approximately zero. As a result, at the moment the power supply is turned on, the main circuit will generate a startup surge current of tens or hundreds of amperes. For this reason, the prior art usually uses a thermistor and a power relay in parallel to suppress the startup surge current, but this method has an obvious defect: if the input power supply mistakenly connects a single phase to a three-phase, or external factors cause the input side voltage peak to be severely distorted, due to the presence of the thermistor, the input side and the inside of the switching power supply cannot be disconnected, resulting in damage to the components in the switching power supply. Summary of the invention

[0004] In view of the deficiencies in the prior art, an embodiment of the present application provides a switching power supply, aiming to solve the technical problems of high failure rate and poor reliability during the startup process of the switching power supply.

[0005] In order to solve the above problems, an embodiment of the present application provides a switching power supply, which includes:

[0006] An anti-surge unit, comprising a surge switch unit and a power switch device connected in parallel, wherein the surge switch unit comprises a thermistor and a surge switch device connected in series, and the connections between the surge switch unit and the power switch device form a first connection point and a second connection point respectively;

[0007] a power factor correction unit, wherein a first input terminal of the power factor correction unit is electrically connected to the second connection point;

[0008] A control unit, electrically connected to the power switch device and the surge switch device respectively;

[0009] Wherein, the first connection point is electrically connected to the live input terminal of the switching power supply, and the second input terminal of the power factor correction unit is electrically connected to the neutral input terminal of the switching power supply, or the first connection point is electrically connected to the neutral input terminal of the switching power supply, and the second input terminal of the power factor correction unit is electrically connected to the live input terminal of the switching power supply;

[0010] In the initial stage of starting up the switching power supply, the power switch device and the surge switch device are both disconnected; in the first stage of starting up the switching power supply, the input side voltage of the switching power supply is normal, and the control unit controls the surge switch device to close; in the second stage of starting up the switching power supply, the voltage across the power switch device is less than a preset voltage, and the control unit controls the power switch device to close.

[0011] Furthermore, in the switching power supply, a voltage acquisition unit is also included;

[0012] The input end of the voltage acquisition unit is electrically connected to the live line input end and the neutral line input end respectively, and the output end of the voltage acquisition unit is electrically connected to the input end of the control unit;

[0013] The voltage acquisition unit is used to collect voltages from the live line input terminal and the neutral line input terminal, and input the collected voltage signals into the control unit. The control unit controls the on and off of the power switch device and the surge switch device according to the voltage signals.

[0014] Furthermore, in the switching power supply, the voltage acquisition unit includes a differential voltage acquisition unit and a voltage bias unit;

[0015] Wherein, the differential voltage acquisition unit is electrically connected to the live line input terminal, the neutral line input terminal and the voltage bias unit respectively, and the voltage bias unit is electrically connected to the control unit;

[0016] The differential voltage acquisition unit is used to perform a difference operation on the voltage signals collected at the live line input end and the neutral line input end, and the voltage bias unit is used to bias the voltage difference signal after the difference operation and input it into the control unit, so that the control unit can control the on and off of the surge switch device.

[0017] Furthermore, in the switching power supply, the differential voltage acquisition unit includes a first operational amplifier;

[0018] Among them, the first operational amplifier includes a first input terminal, a second input terminal and a first output terminal; the first input terminal of the first operational amplifier is electrically connected to the neutral line input terminal, the second input terminal of the first operational amplifier is electrically connected to the live line input terminal, and the first output terminal of the first operational amplifier is electrically connected to the voltage bias unit.

[0019] Furthermore, in the switching power supply, the differential voltage acquisition unit further comprises: a first resistor, a second resistor, a first filtering unit, a second filtering unit, a third filtering unit and a first feedback unit;

[0020] Wherein, one end of the first resistor is electrically connected to the live wire input end, and the other end of the first resistor is electrically connected to the second input end of the first operational amplifier;

[0021] One end of the second resistor is electrically connected to the zero line input terminal, and the other end of the second resistor is electrically connected to the first input terminal of the first operational amplifier;

[0022] One end of the first filter unit is disposed between the first resistor and the second input end of the first operational amplifier and is electrically connected to the second input end of the first operational amplifier, and the other end of the first filter unit is grounded;

[0023] One end of the second filtering unit is electrically connected to the first power supply end of the first operational amplifier, and the other end of the second filtering unit is grounded;

[0024] One end of the third filtering unit is electrically connected to the second power supply end of the first operational amplifier, and the other end of the third filtering unit is grounded to the first filtering unit;

[0025] One end of the first feedback unit is disposed between the second resistor and the first input end of the first operational amplifier and is electrically connected to the first input end of the first operational amplifier, and the other end of the first feedback unit is electrically connected to the first output end of the first operational amplifier.

[0026] Furthermore, in the switching power supply, the voltage bias unit includes a second operational amplifier, a third resistor, a fourth filtering unit and a second feedback unit;

[0027] Wherein, the second operational amplifier comprises a third input terminal, a fourth input terminal and a second output terminal;

[0028] The third input terminal of the second operational amplifier is connected to the reference voltage and is grounded through the fourth filtering unit;

[0029] The fourth input terminal of the second operational amplifier is electrically connected to the differential voltage acquisition unit through the third resistor;

[0030] The second output terminal of the second operational amplifier is electrically connected to the control unit;

[0031] One end of the second feedback unit is electrically connected to the fourth input end of the second operational amplifier, and the other end of the second feedback unit is electrically connected to the second output end of the second operational amplifier.

[0032] Furthermore, in the switching power supply, the reference voltage is a voltage obtained by dividing the power supply voltage of the control unit.

[0033] Furthermore, in the switching power supply, the voltage acquisition unit further includes an anti-saturation unit;

[0034] The anti-saturation unit is electrically connected to the second output terminal of the second operational amplifier and the control unit respectively, and the anti-saturation unit is used to prevent the second operational amplifier from being saturated.

[0035] Furthermore, in the switching power supply, the anti-saturation unit includes a first diode and a second diode;

[0036] The anode of the first diode is electrically connected to the second output terminal of the second operational amplifier, the signal input terminal of the control unit, and the cathode of the second diode respectively, and the anode of the second diode is shared with the ground terminal of the control unit.

[0037] Furthermore, in the switching power supply, a rectifier unit and a common-mode inductor are also included;

[0038] Wherein, the rectifier unit includes a first end, a second end, a third end and a fourth end, and the common mode inductor includes a fifth end, a sixth end, a seventh end and an eighth end;

[0039] The first end of the rectifier unit is electrically connected to the power factor correction unit to form a third connection point, the second end of the rectifier unit is electrically connected to the eighth end of the common-mode inductor, the third end of the rectifier unit is electrically connected to the second connection point, the third connection point is grounded with the fourth end of the rectifier unit through a storage capacitor, the fifth end of the common-mode inductor is electrically connected to the neutral line input end, the sixth end of the common-mode inductor is electrically connected to the live line input end, and the seventh end of the common-mode inductor is electrically connected to the first connection point.

[0040] In the switching power supply provided by the embodiment of the present application, in the initial stage of starting up the switching power supply, the power switching device and the surge switching device are in a disconnected state, thereby ensuring that the input side is completely disconnected from the inside of the switching power supply at the moment the switching power supply is turned on, thereby avoiding damage to components in the switching power supply; when the input side voltage is normal, the surge switching device is controlled to close by the control unit to pre-charge the BUS capacitor in the power factor correction unit; when the voltage across the power switching device is less than the preset voltage, the BUS capacitor is pre-charged at this time, and the power switching device is controlled to close by the control unit, thereby realizing normal startup of the switching power supply, improving the reliability of the startup of the switching power supply, reducing the failure rate of the switching power supply, and broadening the application scenarios of the switching power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 A schematic block diagram of a switching power supply provided in an embodiment of the present application;

[0043] Figure 2 Another schematic block diagram of a switching power supply provided in an embodiment of the present application;

[0044] Figure 3 Another schematic block diagram of a switching power supply provided in an embodiment of the present application;

[0045] Figure 4 A circuit diagram of a switching power supply provided in an embodiment of the present application;

[0046] Figure 5 A voltage waveform diagram sampled at the zero line input terminal of the switching power supply under an ideal state provided in an embodiment of the present application;

[0047] Figure 6 A voltage waveform diagram sampled at the live input terminal and the neutral input terminal of the switching power supply in the actual state provided by the embodiment of the present application;

[0048] Figure 7 An improved voltage waveform diagram provided in an embodiment of the present application;

[0049] Figure 8 Another schematic block diagram of a switching power supply provided in an embodiment of the present application;

[0050] Fig. 9 Another circuit diagram of a switching power supply provided in an embodiment of the present application;

[0051] Fig.10 Another improved sampled voltage waveform diagram provided in an embodiment of the present application;

[0052] Fig.11 Another improved voltage waveform diagram provided by the embodiment of the present application

[0053] Fig.12 A circuit diagram of a voltage acquisition unit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0055] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0056] It should also be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0057] It should be further understood that the term “and / or” used in the specification and appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0058] See also Figure 1 and Figure 2 , Figure 1 A schematic block diagram of a switching power supply provided in an embodiment of the present application, Figure 2 Another schematic block diagram of a switching power supply provided in an embodiment of the present application.

[0059] like Figure 1 and Figure 2 As shown, a switching power supply comprises:

[0060] The surge protection unit 10 comprises a surge switch unit 102 and a power switch device 101 connected in parallel, wherein the surge switch unit 102 comprises a thermistor 1021 and a surge switch device 1022 connected in series, and the connection between the surge switch unit 102 and the power switch device 101 forms a first connection point a and a second connection point b respectively;

[0061] A power factor correction unit 20, wherein a first input terminal of the power factor correction unit is electrically connected to a second connection point b;

[0062] The control unit 30 is electrically connected to the power switch device 101 and the surge switch device 1022 respectively;

[0063] Wherein, the first connection point a is electrically connected to the live input terminal N of the switching power supply, and the second input terminal of the power factor correction unit 20 is electrically connected to the neutral input terminal L of the switching power supply, or the first connection point a is electrically connected to the neutral input terminal L of the switching power supply, and the second input terminal of the power factor correction unit 20 is electrically connected to the live input terminal N of the switching power supply;

[0064] In the initial stage of starting up the switching power supply, the power switch device 101 and the surge switch device 1022 are both disconnected; in the first stage of starting up the switching power supply, the input side voltage of the switching power supply is normal, and the control unit 30 controls the surge switch device 1022 to close; in the second stage of starting up the switching power supply, the voltage across the power switch device 101 is less than the preset voltage, and the control unit 30 controls the power switch device 101 to close.

[0065] In the present application, the surge protection unit 10 may be provided in Figure 1 The live input terminal N of the switching power supply shown in the figure can also be set as Figure 2 At the neutral line input terminal N of the switching power supply shown, the switching power supply can be applied to a single-phase input grid or a three-phase input grid.

[0066] For example, when the switching power supply is applied to a three-phase input power grid, its normal input wiring method is the first live wire-neutral wire, the second live wire-neutral wire, and the third live wire-neutral wire. It may be mistakenly connected into a double live wire connection, such as the first live wire-the second live wire, the second live wire-the third live wire, and the first live wire-the third live wire. At this time, the voltage on the input side will reach 380Vac, which will cause the peak value of the input side voltage to reach 380×1.414=537.3Vdc. Since the BUS capacitor in the power factor correction unit 20 usually has a withstand voltage of 450Vdc, if 537.3Vdc is directly loaded onto the 450Vdc BUS capacitor, it will cause the BUS capacitor to bulge and be damaged.

[0067] To this end, the surge protection unit 10 provided in the present application is formed by connecting the thermistor 1021 and the surge switch device 1022 in series and then in parallel with the power switch device 101, ensuring that before the switching power supply is powered on, the surge switch device 1022 and the power switch device 101 are both in a disconnected state, and the input side of the switching power supply is completely disconnected from the inside of the switching power supply. This not only prevents the BUS capacitor in the power factor correction unit 20 from bulging and being damaged due to excessive input side voltage in the event of a wiring error, but also avoids damage to the internal components of the switching power supply by surge current; at the same time, when the input side voltage of the switching power supply is In the normal state, that is, the first stage of starting the switching power supply, the control unit 30 can control the surge switch device 1022 to close to pre-charge the BUS capacitor in the power factor correction unit 20, thereby preventing the input side voltage from exceeding the set normal range and damaging the BUS capacitor. The voltage on the BUS capacitor accumulates over time and slowly increases until the voltage across the power switching device 101 is lower than the preset voltage, such as 30V, and it can be confirmed that the BUS capacitor pre-charging is completed. At this time, the control unit 30 can control the power switching device 101 to close, thereby realizing normal startup of the switching power supply.

[0068] Among them, the surge protection unit 10 is mainly used to suppress the surge current generated by the startup of the high-power switching power supply. The surge switch device 1022 can be a surge relay, and the power switch device 101 can be a power relay. The surge switch device 1022 and the power switch device 101 can also be other switch devices, which can be selected according to the actual application, and this application does not make specific limitations.

[0069] The power factor correction (PFC) unit 20 is used to change the input characteristics of the switching power supply, so that the current output by the power supply is more stable, to prevent the input power supply from collapsing or overloading, and to improve the power transmission efficiency of the power supply. The power factor correction unit 20 can be a bridgeless PFC or a bridge PFC, which can be selected according to the actual application, and this application does not make specific limitations.

[0070] The control unit 30 is mainly used to control the on and off of the surge switch device 1022 and the power switch device 101 in the surge protection unit 10 of the present application, so as to realize the normal startup and operation of the switching power supply; the control unit 30 can be realized by a circuit composed of control chips such as the main control DSP (Digital Signal Processing) chip and the MCU (Microcontroller Unit) chip in the switching power supply, which can be selected according to the actual application and is not specifically limited in the present application.

[0071] In addition, the switching power supply provided by the present application may include at least one main circuit and at least one auxiliary circuit; wherein the main circuit includes a first AC input terminal, a first relay unit, a first PFC unit, an auxiliary power supply and a first output terminal, the first relay unit is arranged between the first AC input terminal and the first PFC unit, the input terminal of the auxiliary power supply is arranged between the first AC input terminal and the first relay unit, and the first PFC unit is arranged between the first relay unit and the first output terminal; the auxiliary circuit includes a second AC input terminal, a second relay unit, a second PFC unit and a second output terminal, the second relay unit is arranged between the second AC input terminal and the second PFC unit, and the second PFC unit is arranged between the second relay unit and the second output terminal. Specifically, the first PFC unit and the second PFC unit each output power and work independently, the first relay unit and the second relay unit can both adopt the surge protection unit 10 provided by the present application, and the output terminals VCC and VDD of the auxiliary power supply can power the MOS tubes, MCU chips, etc. in the main circuit and the auxiliary circuit. Each main circuit and each auxiliary circuit has at least one power output terminal.

[0072] In the switching power supply provided in the embodiment of the present application, in the initial stage of starting up the switching power supply, the power switch device 101 and the surge switch device 1022 are in the disconnected state, ensuring that the input side is completely disconnected from the inside of the switching power supply at the moment the switching power supply is turned on, thereby avoiding damage to components in the switching power supply; when the input side voltage is normal, the surge switch device 1022 is controlled to be closed by the control unit 30 to pre-charge the BUS capacitor in the power factor correction unit 20; when the voltage across the power switch device 101 is less than the preset voltage, the BUS capacitor is pre-charged at this time, and the power switch device 101 can be controlled to be closed by the control unit 30, thereby realizing normal startup of the switching power supply, thereby improving the reliability of the startup of the switching power supply, reducing the failure rate of the switching power supply, and broadening the application scenarios of the switching power supply.

[0073] In some embodiments, Figure 3 As shown, the switching power supply also includes a voltage acquisition unit 40; wherein, the input end of the voltage acquisition unit 40 is electrically connected to the live wire input terminal N and the neutral wire input terminal L respectively, and the output end of the voltage acquisition unit 40 is electrically connected to the input end of the control unit 30. The voltage acquisition unit 40 is used to collect voltages from the live wire input terminal N and the neutral wire input terminal L, and input the collected voltage signal into the control unit 30. The control unit 30 controls the on and off of the power switch device 101 and the surge switch device 1022 according to the voltage signal.

[0074] In this embodiment, the voltage acquisition unit 40 is used to collect the voltage signal on the live input terminal N and the neutral input terminal L of the switching power supply. The control unit 30 performs an algorithm operation based on the voltage signal to determine whether the voltage on the input side of the switching power supply is normal after the switching power supply is turned on. If it is normal, the control unit 30 can control the surge switch device 1022 to close, and then pre-charge the BUS capacitor in the power factor correction unit 20; if the voltage is too high, the control unit 30 does not need to control the surge switch device 1022 to close, so as to avoid the voltage on the input side of the switching power supply being too high and damaging the BUS capacitor in the power factor correction unit 20, and protect the internal components of the power supply from being damaged by the high voltage breakdown on the input side, thereby improving the reliability of the power supply. At the same time, the control unit 30 can also determine whether the voltage across the power switch device 101 is lower than the preset voltage based on the voltage signal collected by the voltage acquisition unit 40, and then determine whether the BUS capacitor is pre-charged, thereby controlling the power switch device 101 to close, and realizing the normal startup of the switching power supply, thereby avoiding the ticking and bouncing phenomenon of the relay due to the problem of inaccurate input voltage sampling on the input side of the switching power supply.

[0075] In some embodiments, Figure 4 As shown, the control unit 30 adopts a main control DSP chip, and the voltage acquisition unit 40 is implemented by a sampling resistor to collect voltage at the live input terminal N and the neutral input terminal L. The voltage acquisition unit 40 includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a capacitor C2, a capacitor C3, a diode D1, a diode D2, a transient voltage suppression diode TVS1, and a transient voltage suppression diode TVS2.

[0076] Among them, one end of the resistor R1, the resistor R2, and the resistor R3 after being connected in series is electrically connected to the neutral line input terminal L, and the other end of the series connection is connected to one end of the transient voltage suppression diode TVS1, and is electrically connected to the pin DSP-L of the main control DSP chip through the resistor R7 and the resistor R8 in sequence; the other end of the transient voltage suppression diode TVS1, the positive electrode of the diode D1, one end of the resistor R9 and one end of the capacitor C2 are all grounded; the negative electrode of the diode D1 and the other end of the resistor R9 are electrically connected between the resistor R7 and the resistor R8; the other end of the capacitor C2 is electrically connected between the resistor R8 and the pin DSP-L of the main control DSP chip.

[0077] At the same time, one end of the resistor R4, the resistor R5, and the resistor R6 connected in series is electrically connected to the live wire input terminal N, and the other end of the series connection is connected to one end of the transient voltage suppression diode TVS2, and is electrically connected to the pin DSP-N of the main control DSP chip through the resistor R10 and the resistor R11 in sequence; the other end of the transient voltage suppression diode TVS2, one end of the resistor R12, and one end of the capacitor C3 are all grounded; the cathode of the diode D2 and the other end of the resistor R12 are electrically connected between the resistor R10 and the resistor R11; the other end of the capacitor C3 is electrically connected between the resistor R11 and the pin DSP-N of the main control DSP chip.

[0078] This application adopts Figure 4 In the process of voltage acquisition unit 40 collecting voltage at live input terminal N and neutral input terminal L of the switching power supply, after the switching power supply is turned on, the surge switch device 1022 and the power switch device 101 are both in the disconnected state. At this time, there is no loop in the positive half-cycle voltage on the neutral input terminal L, and the voltage acquisition unit 40 can only collect the steamed bun wave voltage signal of the negative half-cycle on the live input terminal N. In an ideal state, the sampling voltage waveform between the live input terminal N and the power ground PGND is as follows Figure 5 However, the voltage acquisition unit 40 can actually acquire voltage signals between the live input terminal N and the power ground PGND and between the neutral input terminal L and the power ground PGND. The voltage waveforms acquired are shown in FIG. Figure 6 As shown, Figure 6 Among them, CH1 is the voltage waveform curve between the neutral line input terminal L and the power ground PGND, and CH2 is the voltage waveform curve between the live line input terminal N and the power ground PGND.

[0079] When the voltage acquisition unit 40 acquires Figure 6 When the voltage waveform curve is shown, due to Figure 6 The voltage waveform curve in the circuit fluctuates, causing the signal actually calculated by the main control DSP chip to control the on and off of the surge switch device 1022 to be unstable, which in turn leads to unclear judgment conditions for whether the main control DSP chip controls the closing of the surge relay, causing the surge relay to switch back and forth between opening and closing, and the external manifestation is that the surge relay keeps making "click", "click", and "click" sounds.

[0080] The specific cause of the above fault is: when the control surge relay is disconnected, the voltage at the live wire input terminal N passes through resistors R4, R5, R6, R10, and R12 to the power ground PGND. Due to the large resistance of the voltage divider resistor, the loop current is small. At the same time, there are parasitic parameters in the power supply part, and the ground wire will form a loop leakage current during the oscilloscope test, which leads to an unbalanced current flowing back to the neutral wire input terminal L, resulting in sampling abnormality in the voltage acquisition unit 40.

[0081] Therefore, it is analyzed that the input source at the live input terminal N and the neutral input terminal L usually does not change suddenly, so we try to calculate the difference of the instantaneous voltage at the live input terminal N and the neutral input terminal L on the input end, and then get the following: Figure 7 The voltage waveform shown in the figure, Figure 7 Among them, CH1 is the voltage waveform curve between the neutral input terminal L and the power ground PGND, CH2 is the voltage waveform curve between the live input terminal N and the power ground PGND, CH3 is the voltage waveform curve at the input source, and M is the voltage waveform curve after the difference operation between CH1 and CH2. At this time, the RMS (root mean square) value read from the oscilloscope is 89.5V, and the actual input value after the difference operation is 90Vac. It can be seen that the value after the difference operation is close to the actual RMS value read from the oscilloscope. Therefore, this application adopts Figure 4 As shown in the switching power supply diagram, in the first stage of starting up the switching power supply, a control signal for controlling the closing of the surge switch device 1022 can be directly generated by a software algorithm, thereby avoiding failures during the startup of the switching power supply.

[0082] In some embodiments, the switching power supply further includes a bias unit, which is disposed between the differential voltage acquisition unit 40 and the control unit 30. The bias unit is used to bias the voltage obtained by the differential voltage acquisition unit 40 according to the voltage difference between the two ends of the input side of the switching power supply, so as to facilitate the control unit 30 to accurately calculate and obtain the voltage between the two ends of the input side of the switching power supply, thereby enabling the control unit 30 to generate a control signal for controlling the closing of the surge switch device 1022, thereby avoiding failures during the startup of the switching power supply.

[0083] In some embodiments, Figure 8 As shown, the voltage acquisition unit 40 includes a differential voltage acquisition unit 401 and a voltage bias unit 402; wherein the differential voltage acquisition unit 401 is electrically connected to the live input terminal N, the neutral input terminal L and the voltage bias unit 402 respectively, and the voltage bias unit 402 is electrically connected to the control unit 30; the differential voltage acquisition unit 401 is used to perform a difference operation on the collected voltage signals on the live input terminal N and the neutral input terminal L, and the voltage bias unit 402 is used to bias the voltage difference signal after the difference operation and input it into the control unit 30, so as to enable the control unit 30 to control the on and off of the surge switch device 1022.

[0084] Specifically, if the voltage acquisition unit 40 uses a sampling resistor to realize voltage acquisition on the live input terminal N and the neutral input terminal L, and performs differential operation through a software algorithm, then when the voltage between the neutral input terminal L and the power ground PGND is a negative voltage (negative half cycle), since the main control DSP chip cannot read the negative voltage value, the main control DSP chip cannot directly use the voltage output at both ends of the pin DSP-N and the pin DSP-L to perform differential operation. Therefore, this embodiment sets a differential voltage acquisition unit 401 and a voltage bias unit 402 in the voltage acquisition unit 40, and the differential voltage acquisition unit 401 is used to perform differential operation on the voltage signal collected on the live input terminal N and the neutral input terminal L, and the voltage bias unit 402 is used to bias the voltage difference signal after the differential operation, thereby ensuring that the signal input to the main control DSP chip is a positive value, thereby ensuring that the main control DSP chip can perform detection calculations, thereby generating a control signal for controlling the closing of the surge switch device 1022, and avoiding failures during the startup of the switching power supply.

[0085] In some embodiments, Fig. 9 As shown, the differential voltage acquisition unit 401 includes a first operational amplifier U1; wherein the first operational amplifier U1 includes a first input terminal, a second input terminal and a first output terminal; the first input terminal of the first operational amplifier U1 is electrically connected to the neutral line input terminal L, the second input terminal of the first operational amplifier U1 is electrically connected to the live line input terminal N, and the first output terminal of the first operational amplifier U1 is electrically connected to the voltage bias unit 402.

[0086] Further, the differential voltage acquisition unit 401 also includes a first resistor, a second resistor, a first filtering unit, a second filtering unit, a third filtering unit and a first feedback unit; wherein, one end of the first resistor is electrically connected to the live line input terminal N, and the other end of the first resistor is electrically connected to the second input terminal of the first operational amplifier U1; one end of the second resistor is electrically connected to the neutral line input terminal L, and the other end of the second resistor is electrically connected to the first input terminal of the first operational amplifier U1; one end of the first filtering unit is arranged between the first resistor and the second input terminal of the first operational amplifier U1, and is electrically connected to the second input terminal of the first operational amplifier U1, and the other end of the first filtering unit is grounded; one end of the second filtering unit is electrically connected to the first power supply terminal of the first operational amplifier U1, and the other end of the second filtering unit is grounded; one end of the third filtering unit is electrically connected to the second power supply terminal of the first operational amplifier U1, and the other end of the third filtering unit is grounded with the first filtering unit; one end of the first feedback unit is arranged between the second resistor and the first input terminal of the first operational amplifier U1, and is electrically connected to the first input terminal of the first operational amplifier U1, and the other end of the first feedback unit is electrically connected to the first output terminal of the first operational amplifier U1.

[0087] Among them, the first resistor and the second resistor play a role of voltage division in the differential voltage acquisition unit 401, the first filter unit, the second filter unit, and the third filter unit play a role of filtering in the differential voltage acquisition unit 401, and the first feedback unit plays a role of negative feedback in the differential voltage acquisition unit 401.

[0088] Please continue reading Fig. 9 , the voltage bias unit 402 includes a second operational amplifier U2, a third resistor, a fourth filter unit and a second feedback unit; wherein the second operational amplifier U2 includes a third input terminal, a fourth input terminal and a second output terminal; the third input terminal of the second operational amplifier U2 is connected to the reference voltage and is grounded through the fourth filter unit; the fourth input terminal of the second operational amplifier U2 is electrically connected to the differential voltage acquisition unit through the third resistor; the second output terminal of the second operational amplifier U2 is electrically connected to the control unit; one end of the second feedback unit is electrically connected to the fourth input terminal of the second operational amplifier U2, and the other end of the second feedback unit is electrically connected to the second output terminal of the second operational amplifier U2. Specifically, the third resistor plays a voltage dividing role in the voltage bias unit 402, the fourth filter unit plays a filtering role in the voltage bias unit 402, and the second feedback unit plays a negative feedback role in the voltage bias unit 402.

[0089] exist Fig. 9 In the illustrated embodiment, the first input terminal of the first operational amplifier U1 is the non-inverting input terminal of the first operational amplifier U1, the second input terminal of the first operational amplifier U1 is the inverting input terminal of the first operational amplifier U1, the third input terminal of the second operational amplifier U2 is the non-inverting input terminal of the second operational amplifier U2, and the fourth input terminal of the second operational amplifier U2 is the inverting input terminal of the second operational amplifier U2. The control unit 30 can be implemented by an MCU chip. Mainly considering the high resistance situation, the first operational amplifier U1 is used in the differential voltage acquisition unit 401. Through the characteristics of the operational amplifier and the use of dual power supplies to power the first operational amplifier U1, the first operational amplifier U1 can perform a difference operation on the voltage collected between the neutral input terminal L and the power ground PGND and the voltage collected between the live input terminal N and the power ground PGND, and then use the voltage bias unit 402 (such as the second operational amplifier U2) to perform bias processing, thereby ensuring that the signal input to the main control DSP chip is positive, thereby ensuring that the main control DSP chip can perform detection calculations, thereby generating a control signal to control the closure of the surge switch device 1022, and avoiding failures during the startup of the switching power supply.

[0090] The voltage bias unit 402 uses a second operational amplifier U2, and the reference voltage is a voltage obtained by dividing the power supply voltage of the control unit 30. For example, the reference voltage can be divided by 3:1 using the power supply voltage of the MCU chip.

[0091] exist Fig. 9 In the specific embodiment shown, the first resistor includes resistor R1, resistor R2, resistor R3, resistor R7 and resistor R8, the second resistor includes resistor R4, resistor R5, resistor R6 and resistor R9, the first filtering unit includes capacitor C2 and resistor R12, the second filtering unit includes capacitor C5, the third filtering unit includes capacitor C3, the first feedback unit includes resistor R11 and capacitor C4, the first power supply terminal of the first operational amplifier U1 is the power supply terminal +VCC, and the second power supply terminal of the first operational amplifier U1 is the power supply terminal -VCC.

[0092] Among them, one end of the resistor R1, the resistor R2, the resistor R3, the resistor R7, and the resistor R8 after being connected in series is electrically connected to the neutral line input terminal L, and the other end of the series connection is electrically connected to the first input terminal of the first operational amplifier U1; one end of the resistor R4, the resistor R5, the resistor R6, the resistor R9, and the resistor R10 after being connected in series is electrically connected to the live line input terminal N, and the other end of the series connection is electrically connected to the second input terminal of the first operational amplifier U1; one end of the capacitor C2 and the resistor R12 after being connected in parallel is electrically connected between the resistor R8 and the first input terminal of the first operational amplifier U1, and the other end of the parallel connection is connected to the power ground PGND; the power supply terminal +VCC of the first operational amplifier U1 is connected to the power ground PGND through the capacitor C5, and the power supply terminal -VCC of the first operational amplifier U1 is connected to the power ground PGND through the capacitor C3; one end of the resistor R11 and the capacitor C4 after being connected in parallel is electrically connected between the resistor R10 and the second input terminal of the first operational amplifier U1, and the other end of the parallel connection is electrically connected to the first output terminal of the first operational amplifier U1.

[0093] Further, in Fig. 9 In the specific embodiment shown, the third resistor includes a resistor R13, the second feedback unit includes a resistor R14, and the fourth filtering unit includes a resistor R15 and a capacitor C6. Among them, one end of the resistor R13 and the resistor R14 connected in series is electrically connected to the first output end of the first operational amplifier U1, and the other end of the series connection is electrically connected to the second output end of the second operational amplifier U2, the third input end of the second operational amplifier U2 is connected to the reference voltage, one end of the resistor R15 and the capacitor C6 connected in parallel is electrically connected between the reference voltage and the third input end of the second operational amplifier U2, and the other end of the parallel connection is connected to the power ground PGND; the fourth input end of the second operational amplifier U2 is electrically connected between the resistor R13 and the resistor R14, and the second output end of the second operational amplifier U2 is electrically connected to the pin MCU-ADC-INPUT of the MCU chip.

[0094] In this embodiment, the principle of virtual short and virtual open of the operational amplifier is used to Fig. 9 The circuit diagram shown is calculated as follows:

[0095] The op amp gain formula is:

[0096]

[0097] Wherein, U1 is the voltage outputted from the first output terminal of the first operational amplifier U1, U2 is the voltage outputted from the second output terminal of the second operational amplifier U2, V REF is the reference voltage.

[0098] When resistor R13 is equal to resistor R14, the simplified gain formula is:

[0099] U2=2V REF -U1

[0100] When the reference voltage is divided by 3:1 using the MCU chip supply voltage, V REF =3.3V×1 / 4=0.825Vdc, which makes U2=0.825×2-U1=1.65Vdc-U1.

[0101] The MCU chip can sample and calculate the reference voltage and the second output end of the second operational amplifier U2 input to the pin U1 of MCU-ADC-INPUT to obtain the voltage at the input source, thereby obtaining a signal for controlling the on and off of the surge switch device 1022.

[0102] This application adopts Fig. 9 The circuit diagram shown in Fig.10 The voltage waveform shown is used for verification. Fig.10 Among them, CH1 is the voltage waveform curve between the neutral line input terminal L and the power ground PGND, CH2 is the voltage waveform curve between the live line input terminal N and the power ground PGND, CH3 is the voltage waveform curve at the input source, M is the voltage waveform curve after the difference operation of CH1 and CH2, and CH4 is the voltage waveform curve output at the first output terminal of the first operational amplifier U1.

[0103] After the MCU chip performs sampling calculations, the voltage at the input source input to the oscilloscope is 69.5Vac. The oscilloscope performs difference calculations and the RMS (root mean square) value of the voltage at the input source is 69.12Vac. The RMS (root mean square) value output by the second operational amplifier U2 is 193mVac. At this time, the RMS (root mean square) value of the voltage at the input source can be inferred to be: Vin = ((510K*3+10K) / 4.3K) × 0.193 = 69.12Vac, which is equal to the RMS value calculated by the oscilloscope.

[0104] from Fig.10It can be seen that the voltage waveform curve outputted at the first output terminal of the first operational amplifier U1 is substantially the same as the voltage waveform curve at the input source, and the two are only reduced in proportion. Fig. 9 The circuit diagram shown in the figure can be found in the waveform diagram Fig.11 . Fig.11 Among them, CH1 is the voltage waveform curve between the neutral input terminal L and the power ground PGND, CH3 is the voltage waveform curve at the input source, CH4 is the voltage waveform curve output at the first output terminal of the first operational amplifier U1, CH5 is the voltage waveform curve output at the second output terminal of the second operational amplifier U2, and CH5 is the average value of the voltage output at the second output terminal of the second operational amplifier U2, which is 1.65V. Therefore, the average value of the voltage output at the second output terminal of the second operational amplifier U2 is 1.65V and the formula U2 = 2V REF -U1 corresponds to the output voltage of the op amp, and 1.65V is set as the lift level of the op amp. The detection signal input to the MCU chip can fluctuate at 1.65V, and the MCU chip can calculate 1.65V as the zero-crossing reference value.

[0105] In some embodiments, Fig.12 As shown, the voltage acquisition unit 40 also includes an anti-saturation unit; wherein the anti-saturation unit is electrically connected to the second output terminal of the second operational amplifier U2 and the control unit 30 respectively, and the anti-saturation unit is used to prevent the second operational amplifier U2 from saturation.

[0106] exist Fig.12 In the illustrated embodiment, the differential voltage acquisition unit 401 further includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a capacitor C2, a capacitor C3, a capacitor C4 and a capacitor C5, and the first operational amplifier U1 further includes a power supply terminal +VCC and a power supply terminal -VCC.

[0107] Among them, one end of the resistor R1, the resistor R2, the resistor R3, and the resistor R7 after being connected in series is electrically connected to the neutral line input terminal L, and the other end of the series connection is electrically connected to the first input terminal of the first operational amplifier U1; one end of the resistor R4, the resistor R5, the resistor R6, and the resistor R8 after being connected in series is electrically connected to the live line input terminal N, and the other end of the series connection is electrically connected to the second input terminal of the first operational amplifier U1; one end of the capacitor C2 and the resistor R10 after being connected in parallel is electrically connected between the resistor R7 and the first input terminal of the first operational amplifier U1, and the other end of the parallel connection is connected to the power ground PGND; the power supply terminal +VCC of the first operational amplifier U1 is connected to the power supply ground PGND through the capacitor C5, and the power supply terminal -VCC of the first operational amplifier U1 is connected to the power supply ground PGND through the capacitor C3; one end of the resistor R9 and the capacitor C4 after being connected in parallel is electrically connected between the resistor R8 and the second input terminal of the first operational amplifier U1, and the other end of the parallel connection is electrically connected to the first output terminal of the first operational amplifier U1.

[0108] The voltage bias unit 402 further includes a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a capacitor C6 and a capacitor C6. The resistor R11 is arranged between the first output terminal of the first operational amplifier U1 and the second output terminal of the second operational amplifier U2, the third input terminal of the second operational amplifier U2 is connected to the reference voltage, and is electrically connected to the pin 3-3VCPA of the MCU chip through the resistor R12, one end of the resistor R13 connected in parallel with the capacitor C6 is electrically connected between the pin 3-3VCPA and the third input terminal of the second operational amplifier U2, the reference voltage is arranged between the pin 3-3VCPA and the resistor R13, and the other end of the resistor R13 connected in parallel with the capacitor C6 is connected to the power ground PGND; the fourth input terminal of the second operational amplifier U2 is electrically connected to the second output terminal of the second operational amplifier U2 through the resistor R14, and the second output terminal of the second operational amplifier U2 is electrically connected to the pin MCU-ADC-INPUT of the MCU chip through the resistor R15.

[0109] exist Fig.12 In the illustrated embodiment, the anti-saturation unit includes a first diode CD1 and a second diode CD2; wherein the anode of the first diode CD1 is electrically connected to the second output terminal of the second operational amplifier U2, the signal input terminal of the control unit 30, and the cathode of the second diode CD2, respectively, and the anode of the second diode CD2 is shared with the ground terminal 30 of the control unit.

[0110] Specifically, the first diode CD1 and the second diode CD2 are both Schottky diodes, the anode of the first diode CD1 and the cathode of the second diode CD2 are electrically connected between the resistor R15 and the pin MCU-ADC-INPUT of the MCU chip, the cathode of the first diode CD1 is electrically connected to the pin 3-3VCPA of the MCU chip, the anode of the second diode CD2 and one end of the capacitor C7 are connected to the power ground PGND, and the other end of the capacitor C7 is electrically connected between the resistor R15 and the pin MCU-ADC-INPUT of the MCU chip. The cathode of the first diode CD1 can also be connected to the working voltage provided by other circuits.

[0111] In some embodiments, Figure 4 as well as Fig. 9 As shown, it also includes a rectifier unit 50 and a common-mode inductor LF1; wherein the rectifier unit 50 includes a first terminal c, a second terminal d, a third terminal e and a fourth terminal f, and the common-mode inductor LF1 includes a fifth terminal g, a sixth terminal h, a seventh terminal i and an eighth terminal j; the first terminal c of the rectifier unit 50 is electrically connected to the input terminal of the power factor correction unit 20 and forms a third connection point, the second terminal d of the rectifier unit 50 is electrically connected to the eighth terminal j of the common-mode inductor LF1, the third terminal e of the rectifier unit 50 is electrically connected to the second connection point b, the third connection point is grounded with the fourth terminal f of the rectifier unit 50 through a storage capacitor C1, the fifth terminal g of the common-mode inductor LF1 is electrically connected to the neutral line input terminal L, the sixth terminal h of the common-mode inductor LF1 is electrically connected to the live line input terminal N, and the seventh terminal i of the common-mode inductor LF1 is electrically connected to the first connection point a.

[0112] In this embodiment, the surge protection unit 10 includes a thermistor RT1, a thermistor RT2, a power relay RLY1 and a surge relay RLY2. The thermistor RT1, the thermistor RT2 and the surge relay RLY2 are connected in series and then connected in parallel with the surge relay RLY2. The rectifier unit 50 includes four diodes to form a full-bridge rectifier circuit. The thermistor RT1 and the thermistor RT2 can be negative temperature coefficient thermistors (NTC) or other types of thermistors.

[0113] The switching power supply provided in the embodiment of the present application adopts a surge protection unit composed of a thermistor and a surge relay connected in series and then in parallel with a power relay, so that the input side of the switching power supply and the internal power circuit of the switching power supply can be completely disconnected, which can effectively solve the problem of excessive voltage on the input side or peak distortion of the power grid, and avoid the risk of damaging the power supply. It can be applied to more severe usage scenarios, broadens the usage scenarios of the switching power supply, reduces the failure rate of the switching power supply, and effectively provides the reliability of starting the switching power supply.

[0114] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A switching power supply, characterized in that: include: An anti-surge unit, comprising a surge switch unit and a power switch device connected in parallel, wherein the surge switch unit comprises a thermistor and a surge switch device connected in series, and the connections between the surge switch unit and the power switch device form a first connection point and a second connection point respectively; a power factor correction unit, wherein a first input terminal of the power factor correction unit is electrically connected to the second connection point; A control unit, electrically connected to the power switch device and the surge switch device respectively; Wherein, the first connection point is electrically connected to the live input terminal of the switching power supply, and the second input terminal of the power factor correction unit is electrically connected to the neutral input terminal of the switching power supply, or the first connection point is electrically connected to the neutral input terminal of the switching power supply, and the second input terminal of the power factor correction unit is electrically connected to the live input terminal of the switching power supply; In the initial stage of starting up the switching power supply, the power switch device and the surge switch device are both disconnected; in the first stage of starting up the switching power supply, the input side voltage of the switching power supply is normal, and the control unit controls the surge switch device to close; in the second stage of starting up the switching power supply, the voltage across the power switch device is less than a preset voltage, and the control unit controls the power switch device to close.

2. The switching power supply according to claim 1, characterized in that: Also includes a voltage acquisition unit; The input end of the voltage acquisition unit is electrically connected to the live line input end and the neutral line input end respectively, and the output end of the voltage acquisition unit is electrically connected to the input end of the control unit; The voltage acquisition unit is used to collect voltages from the live line input terminal and the neutral line input terminal, and input the collected voltage signals into the control unit. The control unit controls the on and off of the power switch device and the surge switch device according to the voltage signals.

3. The switching power supply according to claim 2, characterized in that: The voltage acquisition unit includes a differential voltage acquisition unit and a voltage bias unit; Wherein, the differential voltage acquisition unit is electrically connected to the live line input terminal, the neutral line input terminal and the voltage bias unit respectively, and the voltage bias unit is electrically connected to the control unit; The differential voltage acquisition unit is used to perform a difference operation on the voltage signals collected at the live line input end and the neutral line input end, and the voltage bias unit is used to bias the voltage difference signal after the difference operation and input it into the control unit, so that the control unit can control the on and off of the surge switch device.

4. The switching power supply according to claim 3, characterized in that: The differential voltage acquisition unit includes a first operational amplifier; Among them, the first operational amplifier includes a first input terminal, a second input terminal and a first output terminal; the first input terminal of the first operational amplifier is electrically connected to the neutral line input terminal, the second input terminal of the first operational amplifier is electrically connected to the live line input terminal, and the first output terminal of the first operational amplifier is electrically connected to the voltage bias unit.

5. The switching power supply according to claim 4, characterized in that: The differential voltage acquisition unit further includes: a first resistor, a second resistor, a first filtering unit, a second filtering unit, a third filtering unit and a first feedback unit; the first operational amplifier further includes a first power supply terminal and a second power supply terminal; Wherein, one end of the first resistor is electrically connected to the live wire input end, and the other end of the first resistor is electrically connected to the second input end of the first operational amplifier; One end of the second resistor is electrically connected to the zero line input terminal, and the other end of the second resistor is electrically connected to the first input terminal of the first operational amplifier; One end of the first filter unit is disposed between the first resistor and the second input end of the first operational amplifier and is electrically connected to the second input end of the first operational amplifier, and the other end of the first filter unit is grounded; One end of the second filtering unit is electrically connected to the first power supply end of the first operational amplifier, and the other end of the second filtering unit is grounded; One end of the third filtering unit is electrically connected to the second power supply end of the first operational amplifier, and the other end of the third filtering unit is grounded to the first filtering unit; One end of the first feedback unit is disposed between the second resistor and the first input end of the first operational amplifier and is electrically connected to the first input end of the first operational amplifier, and the other end of the first feedback unit is electrically connected to the first output end of the first operational amplifier.

6. The switching power supply according to claim 3, characterized in that: The voltage bias unit includes a second operational amplifier, a third resistor, a fourth filtering unit and a second feedback unit; Wherein, the second operational amplifier comprises a third input terminal, a fourth input terminal and a second output terminal; The third input terminal of the second operational amplifier is connected to the reference voltage and is grounded through the fourth filtering unit; The fourth input terminal of the second operational amplifier is electrically connected to the differential voltage acquisition unit through the third resistor; The second output terminal of the second operational amplifier is electrically connected to the control unit; One end of the second feedback unit is electrically connected to the fourth input end of the second operational amplifier, and the other end of the second feedback unit is electrically connected to the second output end of the second operational amplifier.

7. The switching power supply according to claim 6, characterized in that: The reference voltage is a voltage obtained by dividing the power supply voltage of the control unit.

8. The switching power supply according to claim 6, characterized in that: The voltage acquisition unit also includes an anti-saturation unit; The anti-saturation unit is electrically connected to the second output terminal of the second operational amplifier and the control unit respectively, and the anti-saturation unit is used to prevent the second operational amplifier from being saturated.

9. The switching power supply according to claim 8, characterized in that: The anti-saturation unit includes a first diode and a second diode; The anode of the first diode is electrically connected to the second output terminal of the second operational amplifier, the signal input terminal of the control unit, and the cathode of the second diode respectively, and the anode of the second diode shares a common ground with the ground terminal of the control unit.

10. The switching power supply according to any one of claims 1 to 9, characterized in that: It also includes a rectifier unit and a common-mode inductor; Wherein, the rectifier unit includes a first end, a second end, a third end and a fourth end, and the common mode inductor includes a fifth end, a sixth end, a seventh end and an eighth end; The first end of the rectifier unit is electrically connected to the power factor correction unit to form a third connection point, the second end of the rectifier unit is electrically connected to the eighth end of the common-mode inductor, the third end of the rectifier unit is electrically connected to the second connection point, the third connection point is grounded with the fourth end of the rectifier unit through a storage capacitor, the fifth end of the common-mode inductor is electrically connected to the neutral line input end, the sixth end of the common-mode inductor is electrically connected to the live line input end, and the seventh end of the common-mode inductor is electrically connected to the first connection point.

Images