Control device and control method for switching device, power supply device, and chip

Abstract

The application discloses a control device and a control method of a switching device, a power supply device and a chip. The control device comprises a first sampling end, a second sampling end, a switch control unit and an overvoltage protection unit. The first sampling end is used for obtaining a first sampling signal reflecting power supply of a load. The second sampling end is used for obtaining a second sampling signal reflecting current flowing through the switching device. The switch control unit is coupled to the first sampling end and the second sampling end, and is used for outputting a driving signal based on the first sampling signal and the second sampling signal to control the switching device to turn on and turn off. The overvoltage protection unit is coupled to the switch control unit and the second sampling end, and is used for outputting a first protection signal to make the switch control unit control the switching device to stop working when it is judged that the power supply of the load is higher than a protection threshold based on the obtained second sampling signal.

Description

Technical Field

[0001] This application relates to the field of control circuit technology, and in particular to a control device and control method for a switching device, a power supply device, and a chip. Background Technology

[0002] A power supply unit is a device used for electrical energy conversion. It can convert the AC power provided by the power grid into DC outputs to power the load. Because it has the advantages of fewer peripheral system components, low cost, simple structure and low standby power consumption, it is widely used in power adapters for various loads.

[0003] In power supply devices, the control device typically controls the switching devices to turn on and off according to the load power supply conditions in order to achieve the required power conversion. If the feedback circuit related to the load power supply malfunctions or the relevant protection circuit inside the control device fails, the control device may control the switching devices to operate for a longer time, causing the load power supply to continuously increase, thereby exceeding the maximum value that the load can withstand and causing damage to the load.

[0004] Therefore, there is an urgent need to propose a control device that can still provide effective protection in the face of the above-mentioned abnormal situations. Summary of the Invention

[0005] In view of the shortcomings of the above-mentioned related technologies, the purpose of this application is to provide a control device and control method for a switching device, a power supply device and a chip.

[0006] To achieve the above and other related objectives, the first aspect of this application discloses a control device for a switching device, comprising: a first sampling terminal for acquiring a first sampling signal reflecting the power supply to a load; a second sampling terminal for acquiring a second sampling signal reflecting the current flowing through the switching device; a switching control unit coupled to the first sampling terminal and the second sampling terminal for outputting a drive signal based on the first and second sampling signals to control the switching device to turn on and off; and an overvoltage protection unit coupled to the switching control unit and the second sampling terminal for outputting a first protection signal when the power supply to the load is higher than a protection threshold based on the acquired second sampling signal, so that the switching control unit controls the switching device to stop working.

[0007] In some embodiments disclosed in the first aspect of this application, the second sampling signal changes in opposite directions to the load power supply.

[0008] In some embodiments disclosed in the first aspect of this application, the overvoltage protection unit is used to detect the second sampling signal during a preset period of time during the conduction of the switching device in order to output the first protection signal.

[0009] The overvoltage protection unit includes: a sampling unit coupled to the second sampling terminal, used to sample the second sampling signal within the preset time period and output it; and a comparison unit coupled to the sampling unit, used to output the first protection signal based on the second sampling signal and an overvoltage threshold signal.

[0010] In some embodiments disclosed in the first aspect of this application, the sampling unit includes: a timing detection circuit coupled to the switch control unit, for timing based on a signal output by the switch control unit to output a sampling pulse within the preset time period; and a transmission circuit coupled to the timing detection circuit, for outputting the second sampling signal during the receipt of the sampling pulse.

[0011] In some embodiments disclosed in the first aspect of this application, the control device further includes: an overvoltage protection unit for preventing accidental overvoltage, coupled to the overvoltage protection unit, for preventing the overvoltage protection unit from erroneously outputting the first protection signal to generate accidental overvoltage protection.

[0012] In some embodiments disclosed in the first aspect of this application, the first sampling terminal is used to couple to an optocoupler, and the anti-false triggering unit includes: an optocoupler detection circuit, coupled to the first sampling terminal, used to detect the first sampling signal based on a first reference signal to output a second protection signal; and a logic circuit, coupled to the overvoltage protection unit and the optocoupler detection circuit, used to output an overvoltage protection signal based on the first protection signal and the second protection signal, so that the switch control unit controls the switching device to stop working based on the overvoltage protection signal.

[0013] In some embodiments disclosed in the first aspect of this application, the overvoltage protection unit includes: a soft-start detection circuit coupled to a soft-start circuit, used to detect the soft-start circuit based on a second reference signal to output a third protection signal; and a logic circuit coupled to the overvoltage protection unit and the soft-start detection circuit, used to output an overvoltage protection signal based on the first protection signal and the third protection signal, so that the switch control unit controls the switching device to stop working based on the overvoltage protection signal.

[0014] In some embodiments disclosed in the first aspect of this application, the switch control unit includes: a conduction detection unit for outputting a conduction signal; a shutdown detection unit coupled to the first sampling terminal for outputting a first shutdown signal based on the first sampling signal and the second sampling signal; and a logic driving unit coupled to the conduction detection unit and the shutdown detection unit for outputting the driving signal based on the conduction signal and the first shutdown signal.

[0015] In some embodiments disclosed in the first aspect of this application, the shutdown detection unit includes: a shutdown reference generation circuit coupled to the first sampling terminal, configured to generate a shutdown reference signal based on the first sampling signal; and a shutdown comparison circuit coupled to the shutdown reference generation circuit, configured to detect the second sampling signal based on the shutdown reference signal to output a first shutdown signal.

[0016] In some embodiments disclosed in the first aspect of this application, the switch control unit further includes: a soft-start unit coupled to the second sampling terminal, for outputting a second shutdown signal based on the second sampling signal; wherein, the logic drive unit outputs the drive signal based on the turn-on signal, the first shutdown signal, and the second shutdown signal.

[0017] In some embodiments disclosed in the first aspect of this application, the soft-start unit includes: a soft-start reference generation circuit, including a capacitor, for generating a soft-start reference signal by charging the capacitor; and a soft-start comparator circuit, coupled to the soft-start reference generation circuit and the second sampling terminal, for detecting the second sampling signal based on the soft-start reference signal to output a second shutdown signal.

[0018] In some embodiments disclosed in the first aspect of this application, the switch control unit further includes a duty cycle adjustment circuit coupled to the logic drive circuit, for outputting a duty cycle adjustment signal to the logic drive circuit to adjust the duty cycle of the drive signal when the conduction duration of the switching device exceeds a duration threshold.

[0019] The second aspect of this application discloses a control chip, which is packaged with any of the control devices disclosed in the first aspect of this application.

[0020] A third aspect of this application discloses a power supply device, comprising a rectifier circuit for receiving an external drive signal to output a rectified signal; a filter circuit coupled to the rectifier circuit for filtering the rectified signal to output a filtered signal; a control device as disclosed in any of the first aspects of this application for outputting a drive signal; a switching device, the control terminal of which is coupled to the control device for turning on or off based on the drive signal; and a power conversion circuit coupled to the switching device and the filter circuit for converting the filtered signal into energy based on the on or off state of the switching device to supply power to a load.

[0021] In some embodiments disclosed in the second aspect of this application, the power supply device further includes: an optocoupler feedback circuit coupled to the power conversion circuit and the control device, for acquiring a first sampling signal reflecting the power supply to the load and sending it to the control device.

[0022] In some embodiments disclosed in the second aspect of this application, the power conversion circuit is configured as a forward power conversion circuit.

[0023] A third aspect of this application discloses a control method for a switching device, comprising the following steps: acquiring a first sampling signal and a second sampling signal, wherein the first sampling signal reflects the load power supply and the second sampling signal reflects the current flowing through the switching device; outputting a drive signal based on the first sampling signal and the second sampling signal to control the switching device to turn on and off; during this period, when it is determined based on the acquired second sampling signal that the load power supply is higher than a protection threshold, outputting a first protection signal to stop the switching device from working.

[0024] In some embodiments disclosed in the third aspect of this application, the second sampling signal changes in opposite directions to the load power supply.

[0025] In some embodiments disclosed in the third aspect of this application, the step of determining that the load power supply is higher than the protection threshold based on the acquired second sampling signal includes: detecting the second sampling signal during a preset period of time during the conduction of the switching device to output the first protection signal.

[0026] In some embodiments disclosed in the third aspect of this application, the control method further includes the step of: preventing the first protection signal from being output erroneously to generate erroneous overvoltage protection.

[0027] In some embodiments disclosed in the third aspect of this application, the step of preventing the erroneous output of the first protection signal to generate erroneous overvoltage protection includes: detecting the first sampling signal based on a first reference signal to output a second protection signal; and outputting an overvoltage protection signal based on the first protection signal and the second protection signal to cause the switching device to stop working.

[0028] In some embodiments disclosed in the third aspect of this application, the step of preventing the erroneous output of the first protection signal to generate erroneous overvoltage protection includes: detecting a soft-start circuit based on a second reference signal to output a third protection signal; and outputting an overvoltage protection signal based on the first protection signal and the third protection signal to cause the switching device to stop working.

[0029] In summary, the control device and method for the switching device, the power supply device, and the chip disclosed in this application utilize the existing circuit structure of the power supply device. By sampling the second sampling signal reflecting the current flowing through the switching device during a preset time period, the load power supply is detected to achieve overvoltage protection. Furthermore, this application is applicable to all control modes of the control device and exhibits high reliability. Additionally, this application includes an overvoltage protection unit to prevent overvoltage from occurring when the load power supply is normally increased under control. Attached Figure Description

[0030] The specific features of the invention involved in this application are shown in the appended claims. The features and advantages of the invention can be better understood by referring to the exemplary embodiments and drawings described in detail below. A brief description of the drawings is as follows:

[0031] Figure 1 The diagram shown is a circuit block diagram of a switching power supply according to one embodiment of this application.

[0032] Figure 2 The diagram shown is a circuit block diagram of a control device according to one embodiment of this application.

[0033] Figure 3 The diagram shown is a circuit block diagram of a switch control unit according to one embodiment of this application.

[0034] Figure 4 The diagram shown is a schematic diagram of the circuit structure of the shutdown detection unit in one embodiment of this application.

[0035] Figure 5 The diagram shown is a circuit block diagram of a switch control unit according to another embodiment of this application.

[0036] Figure 6 The diagram shown is a schematic diagram of the circuit structure of a soft-start unit in one embodiment of this application.

[0037] Figure 7 The diagram shows a waveform of the second sampled signal during the soft-start phase in one embodiment of this application.

[0038] Figure 8 The diagram shown is a circuit block diagram of a switch control unit in yet another embodiment of this application.

[0039] Figure 9 The diagram shown is a circuit block diagram of an overvoltage protection unit according to one embodiment of this application.

[0040] Figure 10 The diagram shown is a schematic diagram of the circuit structure of a sampling unit in one embodiment of this application.

[0041] Figure 11 The diagram shown is a circuit block diagram of a control device in yet another embodiment of this application.

[0042] Figure 12 The diagram shown is a schematic diagram of the optical coupler detection circuit in one embodiment of this application.

[0043] Figure 13 The diagram shown is a schematic diagram of the soft-start detection circuit in one embodiment of this application.

[0044] Figure 14The diagram shown is a circuit block diagram of a power supply device according to one embodiment of this application. Detailed Implementation

[0045] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification.

[0046] In the following description, reference is made to the accompanying drawings, which illustrate several embodiments of the present application. It should be understood that other embodiments may also be used, and changes in mechanical composition, structure, electrical, and operation may be made without departing from the spirit and scope of this disclosure. The following detailed description should not be considered limiting, and the scope of the embodiments of the present application is defined only by the claims of the published patents. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present application. Spatially related terms, such as “upper,” “lower,” “left,” “right,” “below,” “below,” “lower part,” “above,” “upper part,” etc., may be used herein to illustrate the relationship between one element or feature shown in the figures and another element or feature.

[0047] While the terms first, second, etc., are used in some instances herein to describe various elements or parameters, these elements or parameters should not be limited by these terms. These terms are used only to distinguish one element or parameter from another. For example, a first sampling terminal may be referred to as a second sampling terminal, and similarly, a second sampling terminal may be referred to as a first sampling terminal, without departing from the scope of the various described embodiments. Both first and second sampling terminals describe a sampling terminal, but they are not the same sampling terminal unless the context otherwise explicitly indicates otherwise. Similar cases include first protection signal and second protection signal, or first sampling signal and second sampling signal.

[0048] Furthermore, as used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context indicates otherwise. It should be further understood that the terms “comprising,” “including,” indicate the presence of the stated feature, step, operation, element, component, item, kind, and / or group, but do not preclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, components, items, kinds, and / or groups. The terms “or” and “and / or” as used herein are to be interpreted inclusively, or mean any one or any combination thereof. Thus, “A, B, or C” or “A, B, and / or C” means “any one of: A; B; C; A and B; A and C; B and C; A, B, and C.” Exceptions to this definition occur only when combinations of elements, functions, steps, or operations are inherently mutually exclusive in some way.

[0049] Furthermore, it should be noted that this document describes each embodiment separately below in order to clearly illustrate the various inventive features disclosed in this application. However, this does not mean that each embodiment can only be implemented individually. Those skilled in the art can design feasible implementation examples by combining them together according to their needs, or simply replace the interchangeable components / modules in different embodiments according to their design requirements. In other words, the implementation methods taught in this application are not limited to the states described in the following embodiments, but also include substitutions and arrangements between the embodiments / components / modules where feasible, which are described in advance here.

[0050] Please see Figure 1 The figure shows a circuit block diagram of a switching power supply according to one embodiment of this application. As shown, the power supply device 10 includes a rectifier circuit 11, a filter circuit 12, a control device 13, a switching device 14, and a power conversion circuit 15. The rectifier circuit 11 is used to receive an external drive signal and output a rectified signal. The external drive signal can be, for example, an AC signal output from the mains power grid or a DC signal. The rectifier circuit 11 can be a full-wave rectifier circuit or a half-wave rectifier circuit composed of electronic components such as diodes, used to rectify the received external drive signal, thereby outputting a rectified signal. The filter circuit 12 is coupled to the rectifier circuit 11 and is used to filter the rectified signal to output a filtered signal. The control device 13 is coupled to the switching device 14 and the power conversion circuit 15, and is used to control the switching device 14 to periodically turn on and off according to the load power supply condition, so that the power conversion circuit 15 can convert the filtered signal into energy to output the required load power supply.

[0051] In some embodiments, the power conversion circuit requires a feedback circuit to feed back the output load power supply to the control device, enabling the control device to accurately control the power conversion circuit to output the required load power supply. However, when the components in the feedback circuit malfunction, the control device may cause the switching device to operate with a longer conduction time in one cycle, resulting in excessive load power supply. If the load power supply operates above its rated power supply for an extended period, or exceeds its maximum withstand value, it will affect its service life or even burn out. In one example, the power conversion circuit is a forward converter, which feeds back the load power supply to the control device through a feedback circuit composed of optocouplers. Since the optocouplers may fail or be damaged due to light intensity attenuation or overcurrent, the signal reflecting the load power supply may become abnormal. Consequently, the control device may control the switching device to operate with the maximum conduction time, resulting in an excessively high load power supply output, which affects the load.

[0052] Therefore, in some embodiments, a multi-feedback circuit is added between the power conversion circuit and the control device to feed the load power back to the control device. For example, in the aforementioned example, two optocouplers are connected between the forward power conversion circuit and the control device, so that if one of them fails, the other can be used as a backup. However, in this embodiment, additional electronic components are added, which not only increases the power loss of the power supply device but also occupies a larger area, which contradicts the goal of low power consumption and small size in power supply devices.

[0053] In other embodiments, an additional adjustment circuit is provided within the control device to adjust the on-time of the control device. For example, a duty cycle adjustment circuit is provided within the control device to adjust the duty cycle of the drive signal output by the control device to prevent the switching device from operating with an excessively long on-time. However, in this embodiment, the additional adjustment circuit still relies on an external signal, and there is still a risk of component damage. Moreover, it generally has application limitations, such as the duty cycle adjustment circuit being effective only when the power supply is in continuous mode. Thus, the aforementioned risk of excessive load power supply still exists.

[0054] In view of the above, in a possible implementation, this application proposes a control device for a switching device. The control device controls the switching device to turn on and off, so that the power conversion circuit coupled to the switching device performs energy conversion to output power to the load. In the event of the risk of excessive power supply to the load, it can effectively achieve overvoltage protection for the load.

[0055] Please see Figure 2 The figure shows a circuit block diagram of a control device in one embodiment of this application. As shown, the control device 20 includes a first sampling terminal P_21, a second sampling terminal P_22, an output terminal P_23, a switch control unit 21, and an overvoltage protection unit 22. The first sampling terminal P_21 is used to acquire a first sampling signal Fb, the second sampling terminal P_22 is used to acquire a second sampling signal Cs, and the output terminal P_23 is used to couple to the control terminal of the switching device. The switch control unit 21 is coupled to the first sampling terminal P_21, the second sampling terminal P_22, and the output terminal P_23, and is used to output a drive signal Dri based on the first sampling signal Fb and the second sampling signal Cs to control the switching device to turn on and off. The overvoltage protection unit 22 is coupled to the second sampling terminal P_22 and the switch control unit 21, and is used to output a first protection signal Pro1 when the load power supply is higher than the protection threshold based on the acquired second sampling signal Cs, so that the switch control unit 21 controls the switching device to stop working.

[0056] The first sampling signal reflects the load power supply and is obtained by the first sampling terminal through a feedback circuit coupled to the power conversion circuit. The second sampling signal reflects the current flowing through the switching device and is obtained by the second sampling terminal connected to the switching device. The specific methods for obtaining the first and second sampling signals will be detailed later in the embodiments of the power supply device and will not be repeated here.

[0057] Please see Figure 3 The figure shows a circuit block diagram of a switch control unit 21 according to one embodiment of this application. As shown, the switch control unit 21 includes a conduction detection unit 210, a shutdown detection unit 211, and a logic driving unit 213. The conduction detection unit 210 is used to output a conduction signal On. The shutdown detection unit 211 is coupled to a first sampling terminal P_21 and is used to output a first shutdown signal Off1 based on a first sampling signal Fb and a second sampling signal Cs. The logic driving unit 213 is coupled to the conduction detection unit 210 and the shutdown detection unit 211 and is used to output the driving signal Dri based on the conduction signal On and the first shutdown signal Off1.

[0058] The continuity detection unit is used to output a continuity signal On. In one embodiment, the continuity detection unit includes a PWM generation circuit, and the rising edge of the PWM pulse signal output by the PWM generation circuit is used as a continuity signal to the logic driving unit. In this embodiment, the control device uses pulse width modulation (PWM) to control the switching device to turn on and off. In another embodiment, the input terminal of the continuity detection unit is coupled to at least one of the first sampling terminal and the second sampling terminal, so as to output a continuity signal to the logic driving unit based on the received sampling signal. In this embodiment, the control device uses, for example, pulse frequency modulation (PFM) to control the switching device to turn on and off. It should be noted that the implementation of the continuity detection unit is not limited to the embodiments described above. Depending on the control type of the required control device, the continuity detection unit can also be composed of other circuit structures capable of outputting a continuity signal, and this application is not limited thereto.

[0059] Please see Figure 4The figure shows a schematic diagram of the circuit structure of a shutdown detection unit in one embodiment of this application. As shown, the shutdown detection unit 211 includes a shutdown reference generation circuit 2110 and a shutdown comparison circuit 2111. The shutdown reference generation circuit 2110 is coupled to a first sampling terminal P_21 and is used to generate a shutdown reference signal Fb_ref ​​based on a first sampling signal Fb. The shutdown comparison circuit 2111 is coupled to the output terminal of the shutdown reference generation circuit 2110 and is used to detect a second sampling signal Cs based on the shutdown reference signal Fb_ref ​​to output a first shutdown signal Off1.

[0060] by Figure 4 The circuit structure shown is an example. The shutdown reference generation circuit 2110 includes resistors R1 and R2, and a switching transistor Q1. One end of resistor R1 is coupled to the first sampling terminal P_21 and is coupled to the power supply Vcc. The other end is coupled to the first terminal of the switching transistor Q1, which is connected to the control terminal of the switching transistor Q1. One end of resistor R2 is coupled to the second terminal of the switching transistor Q1 and serves as the output terminal of the shutdown reference generation circuit 2110, connected to the shutdown comparator circuit 2111. The other end is grounded Gnd. The shutdown reference generation circuit 2110 outputs a shutdown reference signal Fb_ref ​​by dividing the power supply Vcc using resistor R2. However, it should be noted that... Figure 4 The shutdown reference generation circuit shown is only an example. The resistors therein can also be replaced with other equivalent resistive components. The shutdown reference generation circuit 2110 can also adopt other voltage divider circuit structures. As long as it can generate a shutdown reference signal as a reference for the second sampling signal Cs, it is within the scope of protection of this application.

[0061] The shutdown comparison circuit 2111 includes a comparator Cmp1. The first input terminal of comparator Cmp1 is coupled to the second sampling terminal P_22 to receive the second sampled signal Cs. The second input terminal is coupled to the output terminal of the shutdown reference generation circuit 2110 to obtain the shutdown reference signal Fb_ref. The output terminal P_211 serves as the output terminal of the shutdown detection unit 211, used to connect to the logic driving circuit. Comparator Cmp1 compares the second sampled signal Cs with the shutdown reference signal Fb_ref. When the second sampled signal Cs reaches the shutdown reference signal Fb_ref, it outputs a first shutdown signal Off1 to the logic driving unit. Figure 4 The turn-off comparator circuit shown is only an example. In practical applications, a leading-edge blanking circuit can also be set between the second sampling terminal P_22 and the first input terminal of the comparator Cmp1 to eliminate interference signals when the switching device is turned on. This application does not limit the structure of the turn-off comparator circuit.

[0062] Presented as Figure 3As shown, the logic drive unit 213 can control the switching device to turn on based on the on signal On output by the on detection unit 210, and control the switching device to turn off based on the first off signal Off1 output by the off detection unit 211, thereby enabling the power conversion circuit coupled to the switching device to output load power. However, in practical applications, since the load power supply has not yet been output normally during the power conversion circuit startup phase, the first sampling signal Fb obtained by the first sampling terminal P_21 is very large at this time. Therefore, the switching device operates at a high on-time during the startup phase, which will cause overshoot in the power supply device including the power conversion circuit, the switching device, and the control device, resulting in damage to the components.

[0063] Therefore, in some embodiments, the switch control unit further includes a soft-start unit to ensure a smooth power supply during the start-up phase, avoiding the impact of overshoot on components. Please refer to [link to relevant documentation]. Figure 5 The figure shows a circuit block diagram of a switch control unit in another embodiment of this application, as shown in the figure. Figure 3 Based on the circuit block shown, the switch control unit 20 further includes a soft-start unit 212. The soft-start unit 212 is coupled to the second sampling terminal P_22 and is used to output a second turn-off signal Off2 based on the second sampling signal Cs. Figure 5 In the embodiment shown, the logic drive unit 212 is also coupled to the soft start unit 212 and is used to output a drive signal Dri based on the on signal On, the first off signal Off1, and the second off signal Off2.

[0064] Please see Figure 6 The figure shows a schematic diagram of the circuit structure of a soft-start unit in one embodiment of this application. As shown, the soft-start unit 212 includes a soft-start reference generation circuit 2120 and a soft-start comparison circuit 2121. The soft-start reference generation circuit 2120 is used to generate a soft-start reference signal SS_ref. The soft-start comparison circuit 2122 is coupled to the second sampling terminal P_22 and the soft-start reference generation circuit 2120, and is used to detect the second sampling signal Cs based on the soft-start reference signal SS_ref to output a second turn-off signal Off2.

[0065] by Figure 6The circuit structure shown is an example. The soft-start reference generation circuit 2120 includes a capacitor C1, a switch Q2, a current source Is, and a proportional adjustment circuit K. One end of the current source Is is connected to the power supply Vcc, and one end of the capacitor C1 is connected to the other end of the current source Is, with the other end grounded Gnd. The switch Q2 is connected in parallel across the capacitor C1 via its first and second ends. One end of the proportional adjustment circuit K is connected to one end of the capacitor C1, and the other end is connected to the soft-start comparator circuit 2121. During startup, the switch Q2 is controlled to open, the current source Is charges the capacitor C1, and the capacitor voltage signal Vss gradually increases over time. The proportional adjustment circuit K proportionally adjusts the value of the capacitor voltage signal Vss, thereby outputting the soft-start reference signal SS_ref. Because the capacitor voltage Vss continuously increases during the startup phase, the soft-start reference signal SS_ref also continuously increases. It should be noted that the proportional adjustment circuit K can use 1 / 3, 1 / 2, or 1 / 4 as the adjustment ratio to adjust the capacitor voltage signal Vss, and this application is not limited to this. Furthermore, the structure of the soft-start reference generation circuit is also not limited to this; the switching transistor Q2 can be replaced with a transmission gate or other controllable switches. Any circuit structure capable of generating a soft-start reference signal SS_ref that increases smoothly over time falls within the protection scope of the soft-start reference generation circuit of this application.

[0066] The soft-start comparator circuit 2121 includes a comparator Cmp2. The first input of comparator Cmp2 is coupled to the second sampling terminal P_22 to receive the second sampling signal Cs. The second input is coupled to the output of the soft-start reference generation circuit 2121 to obtain the soft-start reference signal SS_ref. The output terminal P_212 serves as the output of the soft-start unit 212, used to connect to the logic driving circuit. Comparator Cmp2 compares the second sampling signal Cs with the soft-start reference signal SS_ref. When the second sampling signal Cs reaches the soft-start reference signal SS_ref, it outputs a second turn-off signal Off2 to the logic driving unit. Figure 6 The soft-start comparator circuit shown is only an example. In practical applications, a leading-edge blanking circuit can also be set between the second sampling terminal P_22 and the first input terminal of the comparator Cmp2 to eliminate interference signals when the switching device is turned on. This application does not limit the structure of the soft-start comparator circuit.

[0067] Please see Figure 7 The following is a waveform diagram of the second sampled signal during the soft-start phase in one embodiment of this application. Figure 6 and Figure 7The working process of the soft-start phase is explained below. As shown in the figure, the Cs_t coordinate system represents the waveform change of the second sampled signal, and Dri_t represents the waveform of the drive signal. Taking the first two cycles (T1, T2) of the startup phase of the switching device as an example, during the T1 to T2 phase, capacitor C1 is continuously charged, so the soft-start reference signal SS_ref continuously increases from T1 to T2. At T1, when the switching device is turned on, the second sampled signal Cs continuously rises. Since the soft-start reference signal SS_ref is relatively small at this time, the second sampled signal Cs quickly rises to the soft-start reference signal SS_ref1 (to distinguish it from the T2 phase). Figure 7 In stage T1, the soft-start reference signal is designated as SS_ref1, and the switching device is turned off. In stage T2, when the switching device is turned on, the second sampling signal Cs continuously increases. At this time, the soft-start reference signal SS_ref continues to increase based on T1, thus the second sampling signal Cs takes a longer time to rise to the soft-start reference signal SS_ref2 (to distinguish it from stage T1). Figure 7 When the soft-start reference signal for stage T2 is designated as SS_ref2, the switching device is turned off. This continues until the capacitor voltage signal Vss increases to the point that the soft-start reference signal SS_ref is higher than the turn-off reference signal Fb_ref. At this point, the control device enables the power conversion circuit to start. Subsequently, the switch control unit in the control device controls the switching device to turn on and off based on the turn-on signal and the first turn-off signal output by the turn-off detection circuit and the turn-on detection circuit.

[0068] As mentioned above, in some embodiments, the control device may, for example, use pulse width modulation to control the switching device to turn on and off. That is, during the entire control process of the switching device, the switching period of the switching device remains unchanged (i.e., constant frequency, the switching period is the period of the PWM pulse signal output by the pulse width modulation). The control device adjusts the duty cycle of the switching device based on the second sampling signal and the first sampling signal to control the energy conversion of the power conversion circuit.

[0069] However, when the control device is unable to control the duty cycle of the switching devices—for example, due to damage or failure of electronic components (such as optocouplers) in the feedback circuit between the power conversion circuit and the first sampling terminal, resulting in an abnormal first sampling signal, or due to malfunction of internal electronic components in the control device preventing the output of the first turn-off signal—the control device cannot change the conduction duration (i.e., duty cycle) of the switching devices. It can only control the power conversion circuit based on the inherent duty cycle of the PWM pulse signal output by the conduction detection unit. However, since the inherent duty cycle of the PWM pulse signal is generally set relatively large, when the power conversion circuit is in current continuous mode (CCM) and the input signal of the power conversion circuit is also high, the load power supply may exceed the maximum value that the load can accept, thereby damaging the load.

[0070] Therefore, in one embodiment, the switch control unit further includes a duty cycle adjustment circuit, used to output a duty cycle adjustment signal to the switch control unit to adjust the duty cycle of the drive signal when the conduction duration of the switching device exceeds a duration threshold in CCM mode. Please refer to [link to relevant documentation]. Figure 8 The diagram shown is a circuit block diagram of the switch control unit in yet another embodiment of this application. Figure 8 by Figure 3 The circuit block diagram of the switch control unit shown is for example. The switch control unit 21 also includes a duty cycle adjustment circuit 214. The duty cycle adjustment circuit 214 has an input terminal P_214, which is used to sample the input signal Vin of the power conversion circuit. The duty cycle adjustment circuit 214 is used to output a third turn-off signal Off3 to the logic drive circuit 24 to control the switch device to turn off when the conduction time of the switching device exceeds a time threshold, thereby preventing the load power supply output by the power conversion circuit from being too high. In other words, the time threshold determines the maximum value that the conduction time of the switching device can reach, that is, it determines the maximum value of the duty cycle. It should be noted that... Figure 8 This is merely to illustrate the connection method of the duty cycle adjustment circuit in the switch control unit and is not intended to limit the circuit structure of the switch control unit. The duty cycle adjustment circuit can also be used in... Figure 5 It is added based on the switch control unit shown.

[0071] In one example, the duty cycle adjustment circuit includes a current conversion circuit and a delay circuit (not shown). The input terminal of the current conversion circuit serves as the input terminal of the duty cycle adjustment circuit to sample the input signal Vin and convert the sampled input signal Vin into an input current, which determines the duration of the time threshold. The delay circuit is coupled to the current conversion circuit and is used to time based on the input current. When the on-time of the switching device exceeds the time threshold, the delay circuit outputs the third off signal Off3.

[0072] Presented as Figure 3 , Figure 5 ,as well as Figure 8 As shown, the on-time detection unit 210, off-time detection unit 211, soft-start unit 212, and duty cycle adjustment circuit 214 each output their respective signals to the logic drive unit 213. Therefore, the logic drive unit 213 outputs a drive signal Dri based on the on-time signal On, the first off-time signal Off1, the second off-time signal Off2, and the duty cycle adjustment signal Off3 to drive the switching device to turn on or off. In one embodiment, the logic drive unit includes a logic control circuit and a drive circuit (not shown). The logic control circuit is coupled to the on-time detection unit 210, the off-time detection unit 211, the soft-start unit 212, and the duty cycle adjustment circuit 214, and outputs a logic signal Log based on the on-time signal On, the first off-time signal Off1, the second off-time signal Off2, and the duty cycle adjustment signal Off3. The drive circuit is connected to the logic control circuit to output a drive signal Dri based on the logic signal Log to drive the switching device to turn on or off. The logic circuit 232, according to control logic, includes, but is not limited to, triggers, timers, selectors, AND gates, NOR gates, etc., and this application does not impose any limitations on it. It should also be noted that in other embodiments, the soft-start unit 212 and the duty cycle adjustment circuit 214 may be omitted entirely or partially as needed. Therefore, the logic driving unit outputs the logic signal Log based on the on signal On and the first off signal Off1, or the logic driving unit outputs the logic signal Log based on at least one of the second off signal Off2 and the duty cycle adjustment signal Off3, the on signal On, and the first off signal Off1.

[0073] As mentioned above, the duty cycle adjustment circuit can only regulate the load to prevent damage when the control device uses PFM modulation and is in CCM mode, due to excessively high input signal from the power conversion circuit causing excessive load power supply. Therefore, in other modes, such as when electronic components (e.g., optocouplers) in the feedback circuit between the power conversion circuit and the first sampling terminal are damaged or fail, overvoltage protection cannot be achieved. Thus, as shown... Figure 2As shown, the control device described in this application further includes an overvoltage protection unit 22, which is used to output a first protection signal Pro1 when the load power supply is determined to be higher than the protection threshold based on the acquired second sampling signal Cs, so that the switch control unit 21 controls the switching device to stop working. The protection threshold refers to a predetermined maximum allowable value for the load power supply, which may be, for example, the maximum allowable voltage value of the load, or for example, the rated voltage of the load. This application is not limited to this, and those skilled in the art can set it according to actual needs.

[0074] In practical applications, the second sampled signal contains numerous interference signals at the instant the switching device is turned on. Using this second sampled signal as the basis for judging the load power supply at this moment can easily lead to misjudgment. At the moment the switching device is about to turn off, the second sampled signal reaches its peak value. However, the peak value of the second sampled signal may be the same depending on the control device's mode. Therefore, using the peak value of the second sampled signal as the basis for judging the load power supply is also inaccurate. Therefore, the overvoltage protection unit detects the second sampled signal during a preset period of time during the switching device's on-time to output a first protection signal. The preset period of time is the middle portion of the on-time, excluding the two ends of the on-time. The two ends of the on-time refer to the period from the instant of on-time to a preset duration, and the period before the instant of off-time, respectively. For example, the middle period of time may be the period from a fixed delay after the instant the switching device is turned on to a fixed duration before the instant the switching device is turned off; or, for example, the middle period of time may be from 1 / 5 to 4 / 5 of the on-time.

[0075] In one embodiment, the overvoltage protection unit generates a sampling pulse during a preset period of time during the conduction of the switching device to sample the second sampling signal, and compares the sampled second sampling signal with an overvoltage threshold signal to output a first protection signal so that the switch control unit controls the switching device to stop working. The overvoltage threshold signal corresponds to the protection threshold. In one example, the second sampling signal changes inversely with the load power supply. For example, the power conversion circuit coupled to the switching device is a forward converter. Therefore, when the switching device is on, the current flowing through the switching device is the sum of the primary side excitation current and the secondary side current of the forward converter coupled to the primary side. Therefore, the second sampling signal Cs and... They are directly proportional, where V o Indicates the power supply to the load, L m L represents the primary inductance. sThe second sampled signal represents the secondary inductance, and 'n' represents the primary-to-secondary turns ratio. In other words, the second sampled signal changes in opposite directions to the load power supply. In this example, the overvoltage protection unit determines that the second sampled signal is lower than the overvoltage threshold signal by comparison, and therefore determines that the load power supply is higher than the protection threshold, thus outputting the first protection signal. The above example is merely illustrative and is not intended to limit the application. For instance, in an example where the second sampled signal changes in the same direction as the load power supply, the overvoltage protection unit determines that the second sampled signal is higher than the overvoltage threshold signal by comparison, and therefore determines that the load power supply is higher than the protection threshold.

[0076] Please see Figure 9 The figure shows a circuit block diagram of an overvoltage protection unit according to one embodiment of this application. As shown, the overvoltage protection unit 22 includes a sampling unit 220 and a comparison unit 221. The sampling unit 220 is coupled to a second sampling terminal P_22 and is used to sample the second sampling signal Cs during the preset time period and output it. The comparison unit 221 is coupled to the sampling unit 220 and is used to compare the second sampling signal Cs with an overvoltage threshold signal ( Figure 9 (Not shown in the figure) Outputs the first protection signal Pro1.

[0077] Please see Figure 10 The figure shows a schematic diagram of the circuit structure of a sampling unit in one embodiment of this application. As shown, the sampling unit 220 includes a timing detection circuit 2200 and a transmission circuit 2201. The timing detection circuit 2200 is coupled to a switch control unit 21 and is used to time the output of a sampling pulse Pul within a preset time period based on the signal output by the switch control unit 21. The transmission circuit 2201 has an output terminal P_220, which is used to connect to a comparison unit. The transmission circuit 2201 is coupled to the timing detection circuit 2200 and is used to output a second sampling signal Cs to the comparison unit through its output terminal P_220 during the receipt of the sampling pulse Pul. The transmission circuit 2201 includes a transmission gate TG, which is turned on during the receipt of the sampling pulse Pul, thereby transmitting the second sampling signal Cs to the output terminal P_220. It should be noted that... Figure 10 The circuit structure of the transmission circuit 2201 shown is only an example. In other embodiments, the transmission circuit 2201 may also be composed of other controllable switching circuits that can transmit electrical signals.

[0078] In one embodiment, the timing detection circuit 2200 counts the conduction duration of the switching device in the current cycle based on the logic signal or drive signal generated by the switch control unit, and outputs the sampling pulse when the count reaches a reference duration signal. The reference duration signal corresponds to a moment within a preset time period. In one example, the reference duration signal is generated based on the logic signal or drive signal output by the switch control unit. For instance, the reference duration signal is set to reflect the midpoint of the conduction duration of the switch device. The timing detection circuit 2200 times the conduction duration of the switch device in the previous cycle based on the logic signal or drive signal, and generates the reference duration signal based on the conduction duration of the previous cycle. Alternatively, the timing detection circuit 2200 calculates the average conduction duration of the switch device in the previous few cycles based on the logic signal or drive signal, and generates the reference duration signal based on the average value. This application does not limit the generation method of the reference duration signal to this. The reference duration signal only needs to correspond to a moment determined within the preset time period. The timing detection circuit 2200 may include electronic components such as capacitors, proportional operators, comparators, and triggers, depending on the required functions.

[0079] During the normal operation of the control device, a normal increase in load power supply may occur. For example, the feedback circuit composed of optocouplers may not be damaged, or the control device may be in a soft-start phase. To prevent the overvoltage protection unit from misidentifying the normal increase in load power supply as an abnormal overvoltage, in some embodiments, the control device further includes an anti-false overvoltage protection unit (not shown). This anti-false overvoltage protection unit is coupled to prevent the overvoltage protection unit from mistakenly outputting the first protection signal to generate false overvoltage protection.

[0080] Please see Figure 11The figure shows a circuit block diagram of a control device in another embodiment of this application. As shown, the first sampling terminal P_21 of the control device is coupled to an optocoupler. The control device also includes an overvoltage protection unit 23, which includes an optocoupler detection circuit 230, a soft-start detection circuit 231, and a logic circuit 232. The optocoupler detection circuit 230 is coupled to the first sampling terminal P_21 and is used to detect the first sampling signal Fb to output a second protection signal Pro2. The soft-start detection circuit 231 has an input terminal P_321, which is used to connect to the aforementioned soft-start circuit. The soft-start detection circuit 231 is used to detect the startup process of the soft-start circuit to output a third protection signal Pro3. The logic circuit 232 is coupled to the overvoltage protection unit 22, the optocoupler detection circuit 230, and the soft-start detection circuit 231, and is used to output an overvoltage protection signal Ovp based on the first protection signal Pro1, the second protection signal Pro2, and the third protection signal Pro3, so that the switch control unit 21 controls the switching device to stop working based on the overvoltage protection signal Ovp.

[0081] The optocoupler detection circuit detects the first sampled signal based on a first reference signal, and outputs a second protection signal based on the comparison result by comparing the first sampled signal with the first reference signal. (See also...) Figure 12 The figure shows a schematic diagram of the optocoupler detection circuit in one embodiment of this application. As shown, the optocoupler detection circuit 230 includes a comparator Cmp3. The first input terminal of the comparator Cmp3 is coupled to the first sampling terminal P_21 to obtain a first sampling signal Cs, and the second input terminal receives a first reference signal Ref1. When the comparator Cmp3 detects that the first sampling signal Cs reaches the first reference signal Ref1, it considers the optocoupler to be damaged or failed, and thus outputs a second protection signal Pro2. The first reference signal Ref1 is a preset fixed value, provided by the power supply of the control device based on a voltage divider circuit or other circuits composed of constant current sources or constant voltage sources; this application is not limited thereto.

[0082] The soft-start detection circuit detects the soft-start circuit based on a second reference signal, and the soft-start circuit adopts... Figure 6 Taking the circuit structure shown as an example, Figure 11 The soft-start detection circuit 23 shown has its input terminal P_321 coupled to one end of capacitor C1 to detect the capacitor voltage signal Vss of the soft-start circuit. When the capacitor voltage signal Vss reaches the second reference signal, the soft-start detection circuit 231 determines that the soft start has ended and outputs the third protection signal Pro3. The second reference signal Ref2 is a preset fixed value, provided by the power supply of the control device based on a voltage divider circuit or other circuit composed of a constant current source or constant voltage source. Please refer to [link to relevant documentation]. Figure 13 The figure shows a schematic diagram of the soft-start detection circuit in one embodiment of the present application. As shown in the figure, the soft-start detection circuit 231 includes a comparator Cmp4. The first input terminal of the comparator Cmp4 is coupled to one end of the capacitor C1 to detect the capacitor voltage signal Vss of the soft-start circuit. The second input terminal receives the second reference signal Ref2. When the comparator Cmp4 detects that the capacitor voltage signal Vss reaches the second reference signal Ref2, it considers the soft start to be over and outputs the third protection signal Pro3.

[0083] The logic circuit performs logical operations on each received protection signal, such as a logical AND operation. That is, if any one of the logic circuits does not receive a protection signal, it will not output an overvoltage protection signal. The logic circuit includes, but is not limited to, AND gates, based on control logic.

[0084] It should be noted that, Figure 11 This is merely one example of an overvoltage protection unit designed to prevent accidental overvoltage. In practice, for example, the overvoltage protection unit may include a soft-start detection circuit and a logic circuit, wherein the logic circuit outputs an overvoltage protection signal based on a first protection signal and a third protection signal. Alternatively, the overvoltage protection unit may include an optocoupler detection circuit and a logic circuit, wherein the logic circuit outputs an overvoltage protection signal based on a second protection signal and a third protection signal.

[0085] The following combination Figure 2 , Figures 9 to 11 The overvoltage protection function of the control device is explained below. The switch control unit 21 outputs a drive signal Dri to control the switching device to turn on and off, thereby enabling the power conversion circuit connected to the switching device to perform energy conversion to supply power to the load. During this period, the overvoltage protection unit 22 samples a second sampling signal Cs at the midpoint of the current conduction cycle to determine whether the load power supply exceeds the protection threshold. When the load power supply exceeds the protection threshold, it outputs a first protection signal Pro1 to the logic circuit 232. The optocoupler detection circuit 230 detects the first sampling signal Fb to determine whether the externally connected optocoupler is damaged or failed. When it determines that the optocoupler is damaged or failed based on the first sampling signal Fb, it outputs a second protection signal Pro2 to the logic circuit 232. The soft-start detection circuit 231 detects the capacitor voltage signal Vss to determine whether the control device has completed a soft start. When it is determined that the control device has completed a soft start, it outputs a third protection signal Pro3 to the logic circuit 232. When logic circuit 232 receives the first protection signal Pro1, the second protection signal Pro2, and the third protection signal Pro3 at its input terminal, it outputs an overvoltage protection signal Ovp, and the switch control unit 21 controls the switching device to stop working based on the overvoltage protection signal Ovp.

[0086] In summary, the control device disclosed in this application utilizes the existing circuit structure of the power supply device. By sampling the second sampling signal reflecting the current flowing through the switching device during a preset time period, it detects the load power supply to achieve overvoltage protection. Furthermore, it is applicable to all control modes of the control device and has high reliability. In addition, the control device of this application also includes an overvoltage protection unit to prevent overvoltage from occurring when the load power supply is normally increased under control.

[0087] This application also discloses a control chip, which is packaged with the control device described in any of the above embodiments. The control chip further includes multiple pins. In one embodiment, the chip is packaged with a switch control unit and an overvoltage protection unit as described above. The multiple pins include a first pin for acquiring a first sampling signal reflecting the load power supply, a second pin for acquiring a second sampling signal reflecting the flow through the switching device, a third pin for outputting a drive signal, a fourth pin for acquiring the chip power supply, and a fifth pin for grounding. In another embodiment, the chip is packaged with a switch control unit, an overvoltage protection unit, and an anti-misoperation overvoltage protection unit as described above. The multiple pins include a first pin for acquiring a first sampling signal reflecting the load power supply, a second pin for acquiring a second sampling signal reflecting the flow through the switching device, a third pin for outputting a drive signal, a fourth pin for acquiring the chip power supply, and a fifth pin for grounding. For the modules and circuits in each embodiment, please refer to the foregoing description of... Figures 2 to 13 The explanation will not be repeated here.

[0088] This application also discloses a power supply device; please refer to [link / reference]. Figure 14 The figure shows a circuit block diagram of a power supply device in one embodiment of the present application. As shown, the power supply device 30 includes a rectifier circuit 31, a filter circuit 32, a control device 33, a switching device 34, and a power conversion circuit 35.

[0089] The rectifier circuit 31 is used to receive external drive signals and output rectified signals. The external drive signal can be, for example, an AC signal output from the mains power grid or a DC signal. The rectifier circuit 31 can be a full-wave rectifier circuit or a half-wave rectifier circuit composed of electronic components such as diodes, used to rectify the received external drive signal, thereby outputting a rectified signal.

[0090] The filter circuit 32 is coupled to the rectifier circuit 31 and is used to filter the rectified signal output by the rectifier circuit 31 to output a filtered signal to the power conversion circuit 35. In the embodiments, the filter circuit 32 may be a filter capacitor, a π-type filter circuit, an LC-type filter circuit, an RC-type filter circuit, an LCπ-type filter circuit, an RCπ-type filter circuit, etc., and this application does not limit it.

[0091] The control terminal of the switching device 34 is coupled to the control device 33 and is used to turn it on or off based on the drive signal. In this embodiment, the switching device refers to a three-terminal controllable device that can be controlled to both turn on and off by a drive signal. The three-terminal controllable device includes a control terminal, a first terminal, and a second terminal. The control terminal controls the on / off state between its first and second terminals based on the received drive signal. The three-terminal controllable device includes a controllable transistor, such as a metal-oxide-semiconductor field-effect transistor (MOSFET) or a bipolar junction transistor (BJT).

[0092] The power conversion circuit 35 is coupled between the filter circuit 32 and the switching device 34, and is used to convert the received input signal into power to supply power to the load based on the on or off state of the switching device 34; wherein, the input signal is the filtered signal. It should be noted that, in some embodiments, the power supply device may omit the filter circuit 32, in which case the power conversion circuit 35 is coupled between the rectifier circuit 31 and the switching device 34, and the input signal received by the power conversion circuit 35 is the rectified signal.

[0093] In one embodiment, the power conversion circuit is a forward converter. An optocoupler feedback circuit (not shown) is coupled between the power conversion circuit 35 and the control device 33 to acquire a first sampling signal reflecting the load power supply and output it to the control device 33. In one example, the optocoupler feedback circuit includes an optocoupler and a Zener diode. The optocoupler is, for example, composed of a light-emitting diode (LED) and a phototransistor. The LED is connected in series with the Zener diode and in parallel to the output of the power conversion circuit 35. The LED is coupled to the control device 33.

[0094] The control device 33 is used to output a drive signal. The control device 33 can be the control device disclosed in the aforementioned application. For its structure and working principle, please refer to the relevant application. Figures 2 to 13 The explanation will not be repeated here.

[0095] This application also discloses a control method for a switching device, comprising the following steps: step S10, step S11, and step S12. Steps S11 and S12 are not necessarily ordered. During step S11, step S12 is also executed simultaneously to achieve overvoltage protection when the load power supply output in step S11 exceeds a protection threshold. The control method for the switching device can be executed by the aforementioned control device or by other control devices capable of performing the control method.

[0096] In step S10, the first sampling signal and the second sampling signal are acquired.

[0097] Here, by coupling with a switching device, the control device acquires a second sampled signal reflecting the current flowing through the switching device. By coupling with an optocoupler feedback circuit, the control device acquires a first sampled signal reflecting the power supply to the load.

[0098] In step S11, a drive signal is output based on the first sampling signal and the second sampling signal to control the switching device to turn on and off.

[0099] The switch control unit in the control device outputs a drive signal based on the first and second sampled signals. Figures 3 to 8 Taking the description as an example, the switch control unit adopts Figures 3 to 8 For details regarding the execution step S11 of any embodiment and its described circuit structure and operating principle, please refer to the documentation for... Figures 3 to 8 The description will not be repeated here.

[0100] In step S12, when the load power supply is determined to be higher than the protection threshold based on the acquired second sampling signal, a first protection signal is output to stop the switching device from working.

[0101] In this control device, the overvoltage protection unit outputs a first protection signal when it determines that the load power supply is higher than a protection threshold based on the acquired second sampling signal. For example, the overvoltage protection unit detects the second sampling signal during a preset period when the switching device is on to output the first protection signal. Taking the second sampling signal having an inverse relationship with the load power supply as an example, when the overvoltage protection unit detects that the second sampling signal is lower than an overvoltage threshold signal during the preset period, it outputs the first protection signal, wherein the overvoltage threshold signal corresponds to the protection threshold.

[0102] by Figure 2 , Figure 9 , Figure 10 Taking the description as an example, the overvoltage protection unit adopts Figure 2 , Figure 9 , Figure 10 For details regarding the execution step S12 of any embodiment and its described circuit structure and operating principle, please refer to the documentation for... Figure 2 , Figure 9 , Figure 10 The description will not be repeated here.

[0103] During the normal operation of the control device, a normal increase in load power supply may occur, for example, if the optocoupler feedback circuit is not damaged, or if the control device is in the soft-start phase. To prevent the overvoltage protection unit from misidentifying the normal increase in load power supply as an abnormal overvoltage, the control method further includes step S13, in which the first protection signal is prevented from being mistakenly output to generate false overvoltage protection.

[0104] The overvoltage protection unit prevents the erroneous output of a first protection signal. In one embodiment, the overvoltage protection unit detects the first sampled signal based on a first reference signal to output a second protection signal, thereby outputting an overvoltage protection signal based on the first and second protection signals to stop the switching device from operating. In another embodiment, the overvoltage protection unit detects a soft-start circuit based on a second reference signal to output a third protection signal, thereby outputting an overvoltage protection signal based on the first and third protection signals to stop the switching device from operating. In other embodiments, the overvoltage protection unit detects the first sampled signal based on a first reference signal to output a second protection signal, and detects a soft-start circuit based on the second reference signal to output a third protection signal, thereby outputting an overvoltage protection signal based on the first, second, and third protection signals to stop the switching device from operating.

[0105] by Figures 11 to 13 Taking the description as an example, the overvoltage protection unit for preventing accidental overvoltage uses Figures 11 to 13 For details regarding the execution step S13 of any embodiment and its described circuit structure and operating principle, please refer to the documentation for... Figures 11 to 13 The description will not be repeated here.

[0106] In summary, the control device and method for the switching device, the power supply device, and the chip disclosed in this application utilize the existing circuit structure of the power supply device. By sampling the second sampling signal reflecting the current flowing through the switching device during a preset time period, the load power supply is detected to achieve overvoltage protection. Furthermore, this application is applicable to all control modes of the control device and exhibits high reliability. Additionally, this application includes an overvoltage protection unit to prevent overvoltage from occurring when the load power supply is normally increased under control.

[0107] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A control device for a switching device, characterized in that, include: The first sampling terminal is used to acquire the first sampling signal reflecting the power supply to the load. The second sampling terminal is used to acquire a second sampling signal reflecting the current flowing through the switching device; A switch control unit, coupled to the first sampling terminal and the second sampling terminal, is used to output a drive signal based on the first sampling signal and the second sampling signal to control the switching device to turn on and off; An overvoltage protection unit, coupled to the switch control unit and the second sampling terminal, is used to output a first protection signal when the load power supply is higher than the protection threshold based on the acquired second sampling signal. An overvoltage protection unit, coupled to the overvoltage protection unit, is used to prevent the overvoltage protection unit from erroneously outputting the first protection signal to generate erroneous overvoltage protection. It includes at least one of an optocoupler detection circuit and a soft-start detection circuit, as well as a logic circuit, wherein: The optocoupler detection circuit is coupled to the first sampling terminal of an optocoupler and is used to detect the first sampling signal based on the first reference signal to output a second protection signal. The soft-start detection circuit is coupled to a soft-start circuit and is used to detect the soft-start circuit based on a second reference signal to output a third protection signal. The logic circuit is coupled to the optocoupler detection circuit and / or the soft-start detection circuit, and is used to output an overvoltage protection signal based on at least one of the second protection signal and the third protection signal and the first protection signal, so that the switch control unit controls the switching device to stop working based on the overvoltage protection signal.

2. The control device according to claim 1, characterized in that, The second sampling signal changes inversely to the load power supply.

3. The control device according to claim 1, characterized in that, The overvoltage protection unit is used to detect the second sampling signal during a preset period of time when the switching device is turned on, so as to output the first protection signal.

4. The control device according to claim 3, characterized in that, The overvoltage protection unit includes: A sampling unit, coupled to the second sampling terminal, is used to sample the second sampling signal within the preset time period and output it; A comparison unit, coupled to the sampling unit, is used to output the first protection signal based on the second sampling signal and an overvoltage threshold signal.

5. The control device according to claim 4, characterized in that, The sampling unit includes: A timing detection circuit, coupled to the switch control unit, is used to time based on the signal output by the switch control unit to output a sampling pulse within the preset time period; A transmission circuit, coupled to the timing detection circuit, is used to output the second sampling signal during the receipt of the sampling pulse.

6. The control device according to claim 1, characterized in that, The switch control unit includes: A continuity detection unit is used to output a continuity signal; A shutdown detection unit, coupled to the first sampling terminal, is used to output a first shutdown signal based on the first sampling signal and the second sampling signal; A logic driving unit, coupled to the conduction detection unit and the shutdown detection unit, is used to output the driving signal based on the conduction signal and the first shutdown signal.

7. The control device according to claim 6, characterized in that, The shutdown detection unit includes: A shutdown reference generation circuit, coupled to the first sampling terminal, is used to generate a shutdown reference signal based on the first sampling signal. A shutdown comparison circuit, coupled to the shutdown reference generation circuit, is used to detect the second sampled signal based on the shutdown reference signal to output a first shutdown signal.

8. The control device according to claim 6, characterized in that, The switch control unit further includes: a soft-start unit coupled to the second sampling terminal, used to output a second shutdown signal based on the second sampling signal; wherein, the logic drive unit outputs the drive signal based on the turn-on signal, the first shutdown signal, and the second shutdown signal.

9. The control device according to claim 8, characterized in that, The soft-start unit includes: A soft-start reference generation circuit includes a capacitor for generating a soft-start reference signal by charging the capacitor; A soft-start comparator circuit, coupled to the soft-start reference generation circuit and the second sampling terminal, is used to detect the second sampling signal based on the soft-start reference signal to output a second shutdown signal.

10. The control device according to claim 6, characterized in that, The switch control unit further includes a duty cycle adjustment circuit coupled to the logic drive unit, used to output a duty cycle adjustment signal to the logic drive unit to adjust the duty cycle of the drive signal when the conduction time of the switching device exceeds a duration threshold.

11. A control chip, characterized in that, The chip is packaged with a control device as described in any one of claims 1 to 10.

12. A power supply device, characterized in that, include: A rectifier circuit is used to receive external drive signals and output rectified signals. A filter circuit, coupled to the rectifier circuit, is used to filter the rectified signal to output a filtered signal; The control device as described in any one of claims 1 to 10 is used to output a drive signal; A switching device, the control terminal of which is coupled to the control device, for turning on or off based on the drive signal; A power conversion circuit, coupled to the switching device and the filtering circuit, is used to convert the energy of the filtered signal based on the on or off state of the switching device to supply power to the load.

13. The power supply device according to claim 12, characterized in that, Also includes: An optocoupler feedback circuit, coupled to the power conversion circuit and the control device, is used to obtain a first sampling signal reflecting the power supply to the load and send it to the control device.

14. The power supply device according to claim 12, characterized in that, The power conversion circuit is configured as a forward power conversion circuit.

15. A control method for a switching device, characterized in that, A control device applicable to any one of claims 1 to 10, comprising the following steps: Acquire a first sampling signal and a second sampling signal, wherein the first sampling signal reflects the load power supply and the second sampling signal reflects the current flowing through the switching device; Based on the first sampling signal and the second sampling signal, a drive signal is output to control the switching device to turn on and off; During this period, if the load power supply is determined to be higher than the protection threshold based on the acquired second sampling signal, a first protection signal is output; and, The first sampled signal is detected based on the first reference signal to output a second protection signal and / or a soft-start circuit is detected based on the second reference signal to output a third protection signal, so as to output an overvoltage protection signal based on at least one of the second protection signal and the third protection signal and the first protection signal, so that the switch control unit controls the switching device to stop working based on the overvoltage protection signal.

16. The control method according to claim 15, characterized in that, The second sampling signal changes inversely to the load power supply.

17. The control method according to claim 15, characterized in that, The step of determining that the load power supply is higher than the protection threshold based on the acquired second sampling signal and outputting the first protection signal includes: detecting the second sampling signal during a preset period of time during the conduction of the switching device to output the first protection signal.

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