A power supply device and a voltage detection device for a switching power supply

Abstract

This application discloses a power supply device and a voltage detection device for a switching power supply, applied in the field of circuit technology. The device includes: a first resistor whose first and second ends are respectively connected to the first end of an auxiliary winding and the first end of a first switching transistor in the switching power supply; the second end of the first switching transistor is connected to the first end of a second resistor; a control terminal is grounded; the second end of the second resistor is connected to the second end of a third resistor; and the first end of the third resistor is connected to a first power supply terminal. A first voltage detection circuit is used to: detect the voltage across the third resistor and send it to a controller when the power transistor controlling the energization of the primary winding in the switching power supply is in a conducting state, so that the controller performs overvoltage and / or undervoltage detection of the input voltage; the second end of the auxiliary winding is grounded and is the same-name terminal as the DC positive input terminal of the primary winding. Applying the solution of this application can effectively achieve overvoltage and undervoltage protection for the switching power supply, and the structure is simple and highly reliable.

Description

Technical Field

[0001] This invention relates to the field of circuit technology, and in particular to a power supply device and a voltage detection device for a switching power supply. Background Technology

[0002] Among the quality indicators of switching power supplies, the most important is reliability. In the event of a sudden input failure of the switching power supply, that is, if the input voltage of the switching power supply is too high or too low, the drive pulse of the switching power supply should be shut down immediately to stop the switching power supply from working.

[0003] Therefore, switching power supplies require input voltage detection circuits to detect overvoltage and undervoltage, ensuring the power supply is not damaged in case of abnormal input voltage. Current over / undervoltage protection circuits typically acquire the input voltage of the switching power supply via voltage divider resistors, then compare it with a reference voltage through optocoupler isolation and drive amplification to achieve over / undervoltage protection. This current approach requires optocoupler isolation circuits and an auxiliary power supply to power the comparator and reference circuit, resulting in a complex circuit structure and high power consumption.

[0004] In summary, how to effectively implement over- and under-voltage protection for switching power supplies, while ensuring a simple detection circuit structure and high reliability, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a power supply device and a voltage detection device for a switching power supply, so as to effectively realize over- and under-voltage protection of the switching power supply, and the detection circuit has a simple structure and high reliability.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A voltage detection device for a switching power supply includes: a first resistor, a second resistor, a third resistor, a first switching transistor, a first voltage detection circuit, and a controller.

[0008] The first end of the first resistor is connected to the first end of the auxiliary winding of the switching power supply, the second end of the first resistor is connected to the first end of the first switching transistor, the second end of the first switching transistor is connected to the first end of the second resistor, the control terminal of the first switching transistor is grounded, the second end of the second resistor is connected to the second end of the third resistor, and the first end of the third resistor is connected to the first power supply terminal.

[0009] The first voltage detection circuit is used to detect the terminal voltage of the third resistor and send it to the controller when the power transistor used to control the energization state of the primary winding in the switching power supply is in the on state.

[0010] The controller is used to: determine the input voltage of the switching power supply based on the terminal voltage of the third resistor, and perform overvoltage detection and / or undervoltage detection of the input voltage;

[0011] The second end of the auxiliary winding and the DC positive input terminal of the primary winding are of the same name, and the second end of the auxiliary winding is grounded.

[0012] Preferably, it also includes: a first diode, a second diode, a first capacitor, and a fourth resistor;

[0013] The anode of the first diode is connected to the second terminal of the fourth resistor and the control terminal of the first switching transistor, the cathode of the first diode is connected to the second terminal of the first capacitor and the connection terminal is grounded, the first terminal of the first capacitor is connected to the cathode of the second diode and the first terminal of the fourth resistor, and the anode of the second diode is connected to the first terminal of the first resistor and the first terminal of the auxiliary winding.

[0014] The first terminal of the first capacitor can be directly used as the first power supply terminal, or the electrical energy stored in the first capacitor can be converted into the first power supply terminal after voltage level conversion.

[0015] Preferably, it also includes: a fourth diode and a fifth diode;

[0016] The cathode of the fourth diode is connected to the anode of the first diode, and the anode of the fourth diode is connected to the second terminal of the fourth resistor and the control terminal of the first switching transistor, respectively.

[0017] The cathode of the fifth diode is connected to the second end of the first resistor, and the anode of the fifth diode is connected to the first end of the first resistor.

[0018] Preferred options also include:

[0019] The cathode is connected to the control terminal of the first switching transistor, and the anode is connected to the first terminal of the first resistor, forming a sixth diode.

[0020] Preferably, the first voltage detection circuit is a differential amplifier type first voltage detection circuit.

[0021] Preferably, the first voltage detection circuit includes: a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, and a first operational amplifier;

[0022] The first end of the fifth resistor serves as the first input terminal of the first voltage detection circuit and is connected to the first end of the third resistor. The first end of the sixth resistor serves as the second input terminal of the first voltage detection circuit and is connected to the second end of the third resistor. The second end of the fifth resistor is connected to the second end of the seventh resistor and the positive input terminal of the first operational amplifier. The first end of the seventh resistor is grounded. The second end of the sixth resistor is connected to the first end of the eighth resistor and the negative input terminal of the first operational amplifier. The second end of the eighth resistor is connected to the output terminal of the first operational amplifier, and the connection terminal serves as the output terminal of the first voltage detection circuit.

[0023] Preferred options also include:

[0024] The first terminal is connected to the positive input terminal of the first operational amplifier, and the second terminal is connected to the negative input terminal of the first operational amplifier.

[0025] Preferably, the power supply for the first operational amplifier is the first capacitor.

[0026] Preferably, the first switching transistor is a MOSFET or a bipolar transistor.

[0027] Preferably, the controller is further configured to:

[0028] When an overvoltage is detected in the input voltage, an overvoltage warning message is output and the switching power supply is turned off.

[0029] Preferably, the controller is further configured to:

[0030] When an undervoltage input is detected, an undervoltage warning message is output and the switching power supply is turned off.

[0031] Preferably, the controller is further configured to:

[0032] Based on the detected input voltage of the switching power supply, the overcurrent point of the switching power supply is set.

[0033] Preferred options also include:

[0034] The anode is connected to the first terminal of the first switching transistor and the second terminal of the first resistor, respectively, and the cathode is a third diode grounded.

[0035] Preferably, it also includes: a ninth resistor and a second voltage detection circuit;

[0036] The first end of the ninth resistor is connected to the cathode of the third diode, and the second end of the ninth resistor is grounded.

[0037] The second voltage detection circuit is connected to the first end of the ninth resistor and is used to detect the terminal voltage of the ninth resistor and send it to the controller when the power transistor used to control the energization state of the primary winding in the switching power supply is in the off state.

[0038] The controller is also configured to: determine the output voltage of the switching power supply based on the terminal voltage of the ninth resistor, and perform overvoltage detection and / or undervoltage detection of the output voltage.

[0039] A power supply device includes a voltage detection device for a switching power supply as described above.

[0040] By applying the technical solution provided in the embodiments of the present invention, considering that the overvoltage detection and / or undervoltage detection of the input voltage of the switching power supply can be realized by using the auxiliary winding TIB of the switching power supply, it is not necessary to set up an isolation circuit.

[0041] Specifically, when the power transistor controlling the energization of the primary winding in the switching power supply is in the ON state, DC current is input to the primary winding. Since the second terminal of the auxiliary winding and the positive DC input terminal of the primary winding are of the same name, the potential of the second terminal of the auxiliary winding is higher than that of the first terminal. Furthermore, the second terminal of the auxiliary winding is grounded, so its potential is 0, and the potential of the first terminal is negative. The first terminal of the first resistor is connected to the first terminal of the auxiliary winding of the switching power supply, and the second terminal of the first resistor is connected to the first terminal of the first switching transistor. Therefore, the voltage across the first resistor is negative, making detection difficult. Thus, the first switching transistor, the second resistor, and the third resistor are connected in series. When the power transistor controlling the energization of the primary winding in the switching power supply is in the on state, the current flows from the first power supply terminal through the third resistor, the second resistor, the first switching transistor, the first resistor, and the auxiliary winding to ground. In other words, when the power transistor controlling the energization of the primary winding in the switching power supply is in the on state, the voltage across the third resistor is detected by the first voltage detection circuit and sent to the controller. The controller can then calculate the input voltage of the switching power supply based on the voltage across the third resistor, thereby realizing overvoltage detection and / or undervoltage detection of the input voltage.

[0042] Furthermore, when the power transistor used to control the energization state of the primary winding in the switching power supply is in the off state, the potential of the first end of the auxiliary winding is higher than the potential of the second end of the auxiliary winding. The first switching transistor is in the off state, so no current flows through the third resistor. That is, there is no potential difference between the second end and the first end of the third resistor at this time, which will not affect the voltage detection of the third resistor when the power transistor is in the on state.

[0043] In summary, the voltage detection device for the switching power supply of this application can effectively realize over- and under-voltage protection of the switching power supply. Moreover, the voltage detection device for the switching power supply of this application utilizes the original auxiliary winding of the switching power supply to achieve detection, which has a simple structure and high reliability. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a first structural schematic diagram of the voltage detection device for the switching power supply in this invention;

[0046] Figure 2 This is a schematic diagram of the second structure of the voltage detection device for the switching power supply in this invention;

[0047] Figure 3 This is a schematic diagram of the third structure of the voltage detection device for the switching power supply in this invention;

[0048] Figure 4 This is a schematic diagram of the fourth structure of the voltage detection device for the switching power supply in this invention;

[0049] Figure 5 This is a fifth structural schematic diagram of the voltage detection device for the switching power supply in this invention. Detailed Implementation

[0050] The core of this invention is to provide a voltage detection device for a switching power supply, which can effectively realize over- and under-voltage protection of the switching power supply. Moreover, the voltage detection device of the switching power supply in this application utilizes the original auxiliary winding of the switching power supply to achieve detection, which has a simple structure and high reliability.

[0051] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Please refer to Figure 1 , Figure 1This is a schematic diagram of the structure of a voltage detection device for a switching power supply according to the present invention. The voltage detection device for the switching power supply may include: a first resistor R1, a second resistor R2, a third resistor R3, a first switching transistor Q1, a first voltage detection circuit 10, and a controller 20.

[0053] The first end of the first resistor R1 is connected to the first end of the auxiliary winding TIB of the switching power supply. The second end of the first resistor R1 is connected to the first end of the first switching transistor Q1. The second end of the first switching transistor Q1 is connected to the first end of the second resistor R2. The control terminal of the first switching transistor Q1 is grounded. The second end of the second resistor R2 is connected to the second end of the third resistor R3. The first end of the third resistor R3 is connected to the first power supply terminal.

[0054] The first voltage detection circuit 10 is used to detect the terminal voltage of the third resistor R3 and send it to the controller 20 when the power transistor used to control the energization state of the primary winding in the switching power supply is in the on state.

[0055] The controller 20 is used to: determine the input voltage of the switching power supply based on the terminal voltage of the third resistor R3, and perform overvoltage detection and / or undervoltage detection of the input voltage;

[0056] The second end of the auxiliary winding TIB is the same as the DC positive input terminal of the primary winding, and the second end of the auxiliary winding TIB is grounded.

[0057] Specifically, the solution in this application targets a switching power supply in which the primary winding receives DC input. Since DC is input to the primary winding, a power transistor is required on the primary side of the switching power supply to control the energized state of the primary winding. That is, when the power transistor is in the on state, the primary winding is energized; conversely, when the power transistor is in the off state, the primary winding is not energized, so that DC cannot be input to the primary winding.

[0058] During the excitation phase, the power transistor in the switching power supply, used to control the energization state of the primary winding, is in the ON state. At this time, the auxiliary winding TIB is coupled to the primary winding. For example, if the turns ratio of the primary winding to the auxiliary winding TIB is N:1, and the DC input voltage on the primary winding is Vin, then the voltage amplitude on the auxiliary winding TIB is Vin / N. Since the second terminal of the auxiliary winding TIB and the positive DC input terminal of the primary winding are of the same name, when the power transistor is in the ON state, Figure 1 At this time, the voltage on the auxiliary winding TIB is negative at the top and positive at the bottom. Since the second terminal of the auxiliary winding TIB is grounded, the voltage at the second terminal of the auxiliary winding TIB is 0V, which is the voltage of the reference ground, and the voltage at the first terminal of the auxiliary winding TIB is negative.

[0059] As can be seen from the circuit structure, when the power transistor used to control the energization state of the primary winding in the switching power supply is in the on state, the current can flow from the first power supply terminal through the third resistor R3, the second resistor R2, the first switching transistor Q1, the first resistor R1, and the auxiliary winding TIB to ground. The magnitude of the current is positively correlated with the input voltage Vin. Therefore, by detecting the current of the third resistor R3, the input voltage Vin of the primary winding can be determined.

[0060] Since the resistance value of the third resistor R3 is known, detecting the current of the third resistor R3 is also detecting the terminal voltage of the third resistor R3. In this application, the first voltage detection circuit 10 detects the terminal voltage of the third resistor R3 and sends it to the controller 20, so that the controller 20 can calculate the input voltage of the switching power supply based on the terminal voltage of the third resistor R3, thereby performing overvoltage detection and / or undervoltage detection of the input voltage.

[0061] When the power transistor in the switching power supply, which controls the energization state of the primary winding, is in the off state, the auxiliary winding TIB is coupled to the secondary winding. Figure 1 At this time, the voltage on the auxiliary winding TIB is positive at the top and negative at the bottom. At this time, the voltage at the first terminal of the first switch Q1 is higher than the voltage at the control terminal of the first switch Q1. The first switch Q1 is in the off state at this time. Therefore, no current flows through the third resistor R3. That is, there is no potential difference between the second terminal and the first terminal of the third resistor R3 at this time, which will not affect the detection of the terminal voltage of the third resistor R3 when the power transistor is in the on state.

[0062] Furthermore, it should be noted that the input voltage Vin of the primary winding can be determined by detecting the current of the third resistor R3. Similarly, the input voltage Vin of the primary winding can also be determined by detecting the current of the first resistor R1 or the second resistor R2. However, the first resistor R1 has a negative voltage, which is inconvenient to detect. Although the second resistor R2 has a positive voltage, the voltage at the first end of the second resistor R2 is close to 0, and the voltage at the second end of the second resistor R2 is also not high. This is usually not the most suitable voltage detection range for the first voltage detection circuit 10, which is not conducive to ensuring the voltage detection accuracy. Therefore, in the scheme of this application, the first voltage detection circuit 10 is connected to the third resistor R3 to detect the voltage of the third resistor R3.

[0063] In one specific embodiment of the present invention, see [reference needed]. Figure 2 It may also include: a first diode D1, a second diode D2, a first capacitor C1, and a fourth resistor R4;

[0064] The anode of the first diode D1 is connected to the second terminal of the fourth resistor R4 and the control terminal of the first switch Q1, respectively. The cathode of the first diode D1 is connected to the second terminal of the first capacitor C1 and the connection terminal is grounded. The first terminal of the first capacitor C1 is connected to the cathode of the second diode D2 and the first terminal of the fourth resistor R4, respectively. The anode of the second diode D2 is connected to the first terminal of the first resistor R1 and the first terminal of the auxiliary winding TIB, respectively.

[0065] The first terminal of the first capacitor C1 can be used directly as the first power supply terminal, or the electrical energy stored in the first capacitor C1 can be converted into a voltage level and then used as the first power supply terminal.

[0066] As described above, when the power transistor used to control the energization state of the primary winding in the switching power supply is in the off state, the auxiliary winding TIB is coupled to the secondary winding.

[0067] Furthermore, the solution in this application requires a first power supply terminal for power supply. In addition, the first voltage detection circuit 10 typically contains an operational amplifier, which also requires power. Therefore, in this embodiment of the application, considering that the electrical energy generated when the auxiliary winding TIB is coupled with the secondary winding can be effectively utilized, it is beneficial to save electrical energy. Moreover, it eliminates the need for a dedicated auxiliary power supply for the comparator and reference circuit as in conventional solutions, thus simplifying the circuit structure and reducing power consumption.

[0068] Specifically, when the power transistor in the switching power supply, which controls the energization state of the primary winding, is in the off state, the auxiliary winding TIB is coupled to the secondary winding. Figure 2 In this configuration, the voltage on the auxiliary winding TIB is positive at the top and negative at the bottom. The auxiliary winding TIB charges the first capacitor C1 through the second diode D2. The first terminal of the first capacitor C1 can then be used directly as the first power supply terminal, or the voltage level of the electrical energy stored in the first capacitor C1 can be converted before being used as the first power supply terminal. For example, in some cases, the voltage output from the first capacitor C1 is boosted / buckled by a boost / buck circuit and then used as the first power supply terminal required by this application. In the accompanying drawings of this application, the first power supply terminal is marked as REF.

[0069] Furthermore, it should be noted that in this embodiment, a first diode D1 is connected in series with the fourth resistor R4, and this series branch is connected in parallel with the first capacitor C1. The anode of the first diode D1 is connected to the control terminal of the first switching transistor Q1. This structure helps to further improve the detection accuracy. Specifically, when a negative voltage appears at the upper end of the auxiliary winding TIB, that is, when the power transistor in the switching power supply used to control the energization state of the primary winding is in the on state, the voltage on the auxiliary winding TIB is negative at the top and positive at the bottom. At this time, through the fourth resistor R4 and the first diode D1, a bias voltage of 1 junction voltage drop is provided to the first switching transistor Q1. That is, the control terminal voltage of the first switching transistor Q1 is approximately 0.7V, while the first terminal voltage of the first switching transistor Q1 is approximately 0V. This allows the first switching transistor Q1 to conduct when a negative voltage appears at the first terminal of the auxiliary winding TIB. At the same time, it can offset the influence of temperature on the turn-on voltage of the first switching transistor Q1, thus helping to improve the detection accuracy.

[0070] The specific model of the first switching transistor Q1 in this application can be set and adjusted according to actual needs, as long as it can meet the on / off requirements of the first switching transistor Q1 in this application. For example, in a specific case, the first switching transistor Q1 can be a MOSFET or a transistor. In the accompanying drawings of this application, the first switching transistor Q1 is an NPN type transistor, which has a lower cost. The base of the transistor serves as the control terminal of the first switching transistor Q1, the emitter of the transistor serves as the first terminal of the first switching transistor Q1, and the collector of the transistor serves as the second terminal of the first switching transistor Q1.

[0071] The specific circuit configuration of the first voltage detection circuit 10 can also be selected as needed. For example, to ensure the accuracy of the detection, please refer to [reference needed]. Figure 3 The first voltage detection circuit 10 in this application is specifically a differential amplifier type first voltage detection circuit 10. Of course, the specific structure of the differential amplifier type first voltage detection circuit 10 can also be various. Figure 3 In a specific implementation, the differential amplification type first voltage detection circuit 10 can be easily implemented using four resistors and one operational amplifier, resulting in high reliability.

[0072] Specifically, in this particular embodiment of the present invention, the first voltage detection circuit 10 may include: a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, and a first operational amplifier OP1;

[0073] The first end of the fifth resistor R5 serves as the first input terminal of the first voltage detection circuit 10 and is connected to the first end of the third resistor R3. The first end of the sixth resistor R6 serves as the second input terminal of the first voltage detection circuit 10 and is connected to the second end of the third resistor R3. The second end of the fifth resistor R5 is connected to the second end of the seventh resistor R7 and the positive input terminal of the first operational amplifier OP1. The first end of the seventh resistor R7 is grounded. The second end of the sixth resistor R6 is connected to the first end of the eighth resistor R8 and the negative input terminal of the first operational amplifier OP1. The second end of the eighth resistor R8 is connected to the output terminal of the first operational amplifier OP1, and the connection terminal serves as the output terminal of the first voltage detection circuit 10.

[0074] For example, if we call the potential at the first terminal of the third resistor R3 VP, and the potential at the second terminal of the second resistor R2 VN, then the voltage across the third resistor R3 can be expressed as ΔV = VP - VN. From the circuit structure, we know that when the power transistor in the switching power supply, which controls the energization state of the primary winding, is in the on state, the input voltage Vin conforms to:

[0075] In the formula, N is the turns ratio, that is, the turns ratio of the primary winding to the auxiliary winding TIB of the switching power supply is N:1. This represents the total voltage across the first resistor R1, the second resistor R2, and the third resistor R3, for example, 15V. If REF is 5V, then the voltage amplitude of the auxiliary winding TIB is 10V, meaning the voltage at the second terminal of the auxiliary winding TIB is 0V, and the voltage at the first terminal of the auxiliary winding TIB is -10V. If N is 10, then in this example, the input voltage Vin of the switching power supply is 100V.

[0076] exist Figure 3 In this embodiment, the output voltage of the first operational amplifier OP1 reflects the magnitude of the voltage ΔV across the third resistor R3. Based on the output voltage of the first operational amplifier OP1, the controller 20 can calculate the voltage ΔV across the third resistor R3, and then calculate the input voltage Vin of the switching power supply, thereby performing overvoltage and / or undervoltage detection. That is, when the input voltage Vin of the switching power supply is greater than the overvoltage threshold, it can be determined that the input voltage of the switching power supply is overvoltage; when the input voltage Vin of the switching power supply is less than the undervoltage threshold, it can be determined that the input voltage of the switching power supply is undervoltage.

[0077] See also Figure 3 In one specific embodiment of the present invention, it may further include:

[0078] The first terminal is connected to the positive input terminal of the first operational amplifier OP1, and the second terminal is connected to the negative input terminal of the first operational amplifier OP1.

[0079] In this embodiment, filtering by the second capacitor C2 can ensure the input stability of the first operational amplifier OP1, which is also beneficial to further improve the detection accuracy of the terminal voltage of the third resistor R3 in this application.

[0080] In one specific embodiment of the present invention, the power supply for the first operational amplifier OP1 is the first capacitor C1.

[0081] As described above, the first voltage detection circuit 10 typically includes an operational amplifier (op-amp) that requires a power supply. Therefore, in this embodiment, the power supply for the first op-amp OP1 is directly provided by the first capacitor C1. Figure 3 In the diagram, the power supply for the first operational amplifier OP1 is labeled VDD, which is the first terminal of the first capacitor C1. This implementation configuration allows for... Figure 3 The VDD and REF power required in this circuit can both come from the first capacitor C1. Therefore, the solution of this application effectively utilizes the power generated when the auxiliary winding TIB is coupled with the secondary winding, which is beneficial for saving power. Furthermore, it does not require a dedicated auxiliary power supply for the comparator and reference circuit as in traditional solutions, thus simplifying the circuit structure and reducing power consumption.

[0082] In one specific embodiment of the present invention, the controller 20 can also be used for:

[0083] When an overvoltage is detected in the input voltage, an overvoltage warning message is output and the switching power supply is turned off.

[0084] In this implementation, when the controller 20 detects an input voltage overvoltage, it can output an overvoltage warning message so that staff can promptly notice the overvoltage situation, for example, by displaying an overvoltage warning message via an indicator light. Simultaneously, the switching power supply can be controlled to be in the off state to ensure circuit safety.

[0085] In one specific embodiment of the present invention, the controller 20 can also be used for:

[0086] When an undervoltage input is detected, an undervoltage warning message is output and the switching power supply is turned off.

[0087] In this implementation, when the controller 20 detects an undervoltage input voltage, it can output an undervoltage warning message so that staff can promptly notice the undervoltage situation. At the same time, it can also control the switching power supply to be in the off state to ensure circuit safety.

[0088] In one specific embodiment of the present invention, the controller 20 can also be used for:

[0089] Based on the detected input voltage of the switching power supply, the overcurrent point of the switching power supply is set.

[0090] In this embodiment, since the solution of this application can accurately detect the input voltage of the switching power supply, the controller 20 can set the overcurrent point of the switching power supply based on the detected input voltage, thereby effectively improving power efficiency. Furthermore, in other embodiments, the detected input voltage of the switching power supply may be used in other ways without affecting the implementation of this invention.

[0091] In one specific embodiment of the present invention, see [reference needed]. Figure 3 It may also include:

[0092] The anode is connected to the first terminal of the first switching transistor Q1 and the second terminal of the first resistor R1, respectively, and the cathode is grounded.

[0093] This implementation takes into account that when the power transistor in the switching power supply used to control the energization state of the primary winding is in the off state, the auxiliary winding TIB is coupled to the secondary winding. Figure 3 In this configuration, the voltage on the auxiliary winding TIB is positive at the top and negative at the bottom. To prevent the voltage at the first terminal of the first switch Q1 from becoming too high and causing it to break down in reverse, a third diode D3 is used in this embodiment. It can be seen that when the voltage on the auxiliary winding TIB is positive at the top and negative at the bottom, the first switch Q1 is in the off state. Figure 3 Taking a transistor as an example, due to the setting of the third diode D3, the emitter voltage of the transistor is clamped at 0.7V, which effectively avoids the transistor being reverse-biased and broken down.

[0094] In one specific embodiment of the present invention, see [reference needed]. Figure 4 It may also include: a ninth resistor R9, and a second voltage detection circuit;

[0095] The first terminal of the ninth resistor R9 is connected to the cathode of the third diode D3, and the second terminal of the ninth resistor R9 is grounded.

[0096] The second voltage detection circuit is connected to the first end of the ninth resistor R9. When the power transistor used to control the energization state of the primary winding in the switching power supply is in the off state, the terminal voltage of the ninth resistor R9 is detected and sent to the controller 20.

[0097] The controller 20 is also used to: determine the output voltage of the switching power supply based on the terminal voltage of the ninth resistor R9, and perform overvoltage detection and / or undervoltage detection of the output voltage.

[0098] In the aforementioned embodiment, the detection of the input voltage of the switching power supply is described. In this embodiment, considering that the power transistor used to control the energization state of the primary winding in the switching power supply is in the off state, the auxiliary winding TIB is coupled to the secondary winding. Therefore, the voltage on the auxiliary winding TIB is proportional to the voltage of the secondary winding, i.e., to the output voltage of the switching power supply. The magnitude of the output voltage of the switching power supply can be calculated accordingly, thereby enabling overvoltage detection and / or undervoltage detection of the output voltage.

[0099] See also Figure 4 Since the voltage is positive at the top and negative at the bottom when the auxiliary winding TIB is coupled to the secondary winding, it is relatively easy to detect the output voltage of the switching power supply. That is, by detecting the voltage across the ninth resistor R9, the voltage VO on the auxiliary winding TIB can be determined.

[0100] Vout represents the voltage across the first terminal of the ninth resistor R9, which is the terminal voltage of the ninth resistor R9 detected by the second voltage detection circuit. D3 The forward voltage of the third diode D3 is typically 0.7V. After obtaining the voltage VO on the auxiliary winding TIB, the voltage of the secondary winding can be determined according to the turns ratio between the auxiliary winding TIB and the secondary winding, which in turn determines the output voltage of the switching power supply. Figure 4 The specific structure of the second voltage detection circuit is not shown in the diagram. It can be set according to actual needs and does not affect the implementation of the present invention.

[0101] In one specific embodiment of the present invention, see [reference needed]. Figure 5 It may also include: a fourth diode D4 and a fifth diode D5;

[0102] The cathode of the fourth diode D4 is connected to the anode of the first diode D1, and the anode of the fourth diode D4 is connected to the second terminal of the fourth resistor R4 and the control terminal of the first switch Q1.

[0103] The cathode of the fifth diode D5 is connected to the second end of the first resistor R1, and the anode of the fifth diode D5 is connected to the first end of the first resistor R1.

[0104] In the aforementioned embodiment, the first diode D1 provides a bias voltage equal to the junction voltage drop to the first switch Q1 when the first terminal of the auxiliary winding TIB is negative, ensuring the conduction of the first switch Q1. In this embodiment, a fourth diode D4 connected in series with the first diode D1 can be used, and correspondingly, a fifth diode D5 can be connected in series at the first terminal of the first switch Q1, similarly providing a bias voltage equal to the junction voltage drop to the first switch Q1 and ensuring its conduction. Furthermore, the inclusion of the fifth diode D5 helps to further prevent reverse breakdown of the first switch Q1 when the first terminal of the auxiliary winding TIB is positive.

[0105] In one specific embodiment of the present invention, it may further include:

[0106] A sixth diode D6 is connected to the control terminal of the first switching transistor Q1, and the anode is connected to the first terminal of the first resistor R1. In this embodiment, the sixth diode D6 can also prevent reverse breakdown of the first switching transistor Q1 when the first terminal of the auxiliary winding TIB is at a positive voltage.

[0107] By applying the technical solution provided in the embodiments of the present invention, considering that the overvoltage detection and / or undervoltage detection of the input voltage of the switching power supply can be realized by using the auxiliary winding TIB of the switching power supply, it is not necessary to set up an isolation circuit.

[0108] Specifically, when the power transistor controlling the energization state of the primary winding in the switching power supply is in the ON state, DC current is input to the primary winding. Since the second terminal of the auxiliary winding TIB and the positive DC input terminal of the primary winding are of the same name, the potential of the second terminal of the auxiliary winding TIB is higher than the potential of the first terminal of the auxiliary winding TIB. Furthermore, the second terminal of the auxiliary winding TIB is grounded, so its potential is 0, and the potential of the first terminal is negative. The first terminal of the first resistor R1 is connected to the first terminal of the auxiliary winding TIB of the switching power supply, and the second terminal of the first resistor R1 is connected to the first terminal of the first switching transistor Q1. Therefore, the voltage across the first resistor R1 is negative, making detection difficult. Therefore, the first switching transistor Q1, the second resistor R2, and the third resistor R3 are connected in series. When the power transistor controlling the energization of the primary winding in the switching power supply is in the on state, the current flows from the first power supply terminal through the third resistor R3, the second resistor R2, the first switching transistor Q1, the first resistor R1, and the auxiliary winding TIB to ground. In other words, when the power transistor controlling the energization of the primary winding in the switching power supply is in the on state, the first voltage detection circuit 10 detects the terminal voltage of the third resistor R3 and sends it to the controller 20. The controller 20 can then calculate the input voltage of the switching power supply based on the terminal voltage of the third resistor R3, thereby realizing overvoltage detection and / or undervoltage detection of the input voltage.

[0109] Furthermore, when the power transistor used to control the energization state of the primary winding in the switching power supply is in the off state, the potential of the first terminal of the auxiliary winding TIB is higher than the potential of the second terminal of the auxiliary winding TIB. The first switching transistor Q1 is in the off state, so no current flows through the third resistor R3. That is, there is no potential difference between the second terminal and the first terminal of the third resistor R3 at this time, which will not affect the voltage detection of the third resistor R3 when the power transistor is in the on state.

[0110] In summary, the voltage detection device for the switching power supply of this application can effectively realize over- and under-voltage protection of the switching power supply. Moreover, the voltage detection device for the switching power supply of this application utilizes the original auxiliary winding TIB of the switching power supply for detection, which has a simple structure and high reliability.

[0111] Corresponding to the above embodiments of the voltage detection device for switching power supplies, this embodiment of the invention also provides a power supply device, which may include the voltage detection device for switching power supplies as in any of the above embodiments. It can be referred to in correspondence with the above description, and will not be repeated here.

[0112] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0113] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0114] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A voltage detection device for a switching power supply, characterized in that, include: First resistor, second resistor, third resistor, first switching transistor, first voltage detection circuit and controller; The first end of the first resistor is connected to the first end of the auxiliary winding of the switching power supply, the second end of the first resistor is connected to the first end of the first switching transistor, the second end of the first switching transistor is connected to the first end of the second resistor, the control terminal of the first switching transistor is grounded, the second end of the second resistor is connected to the second end of the third resistor, and the first end of the third resistor is connected to the first power supply terminal. The first voltage detection circuit is used to detect the terminal voltage of the third resistor and send it to the controller when the power transistor used to control the energization state of the primary winding in the switching power supply is in the on state. The controller is used to: determine the input voltage of the switching power supply based on the terminal voltage of the third resistor, and perform overvoltage detection and / or undervoltage detection of the input voltage; The second end of the auxiliary winding and the DC positive input terminal of the primary winding are of the same name, and the second end of the auxiliary winding is grounded. It also includes: a first diode, a second diode, a first capacitor, and a fourth resistor; The anode of the first diode is connected to the second terminal of the fourth resistor and the control terminal of the first switching transistor, the cathode of the first diode is connected to the second terminal of the first capacitor and the connection terminal is grounded, the first terminal of the first capacitor is connected to the cathode of the second diode and the first terminal of the fourth resistor, and the anode of the second diode is connected to the first terminal of the first resistor and the first terminal of the auxiliary winding. The first terminal of the first capacitor can be directly used as the first power supply terminal, or the electrical energy stored in the first capacitor can be converted into the first power supply terminal after voltage level conversion. It also includes: the fourth diode and the fifth diode; The cathode of the fourth diode is connected to the anode of the first diode, and the anode of the fourth diode is connected to the second terminal of the fourth resistor and the control terminal of the first switching transistor, respectively. The cathode of the fifth diode is connected to the second end of the first resistor, and the anode of the fifth diode is connected to the first end of the first resistor. The first voltage detection circuit is a differential amplifier type first voltage detection circuit; The first voltage detection circuit includes: a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, and a first operational amplifier; The first end of the fifth resistor serves as the first input terminal of the first voltage detection circuit and is connected to the first end of the third resistor. The first end of the sixth resistor serves as the second input terminal of the first voltage detection circuit and is connected to the second end of the third resistor. The second end of the fifth resistor is connected to the second end of the seventh resistor and the positive input terminal of the first operational amplifier. The first end of the seventh resistor is grounded. The second end of the sixth resistor is connected to the first end of the eighth resistor and the negative input terminal of the first operational amplifier. The second end of the eighth resistor is connected to the output terminal of the first operational amplifier, and the connection terminal serves as the output terminal of the first voltage detection circuit.

2. The voltage detection device for a switching power supply according to claim 1, characterized in that, Also includes: The cathode is connected to the control terminal of the first switching transistor, and the anode is connected to the first terminal of the first resistor, forming a sixth diode.

3. The voltage detection device for a switching power supply according to claim 1, characterized in that, Also includes: The first terminal is connected to the positive input terminal of the first operational amplifier, and the second terminal is connected to the negative input terminal of the first operational amplifier.

4. The voltage detection device for a switching power supply according to claim 1, characterized in that, The power supply for the first operational amplifier is the first capacitor.

5. The voltage detection device for a switching power supply according to claim 1, characterized in that, The first switching transistor is either a MOSFET or a bipolar transistor.

6. The voltage detection device for a switching power supply according to claim 1, characterized in that, The controller is also used for: When an overvoltage is detected in the input voltage, an overvoltage warning message is output and the switching power supply is turned off.

7. The voltage detection device for a switching power supply according to claim 6, characterized in that, The controller is also used for: When an undervoltage input is detected, an undervoltage warning message is output and the switching power supply is turned off.

8. The voltage detection device for a switching power supply according to claim 1, characterized in that, The controller is also used for: Based on the detected input voltage of the switching power supply, the overcurrent point of the switching power supply is set.

9. The voltage detection device for a switching power supply according to any one of claims 1 to 8, characterized in that, Also includes: The anode is connected to the first terminal of the first switching transistor and the second terminal of the first resistor, respectively, and the cathode is a third diode grounded.

10. The voltage detection device for a switching power supply according to claim 9, characterized in that, Also includes: Ninth resistor, second voltage detection circuit; The first end of the ninth resistor is connected to the cathode of the third diode, and the second end of the ninth resistor is grounded. The second voltage detection circuit is connected to the first end of the ninth resistor and is used to detect the terminal voltage of the ninth resistor and send it to the controller when the power transistor used to control the energization state of the primary winding in the switching power supply is in the off state. The controller is also configured to: determine the output voltage of the switching power supply based on the terminal voltage of the ninth resistor, and perform overvoltage detection and / or undervoltage detection of the output voltage.

11. A power supply device, characterized in that, Includes a voltage detection device for a switching power supply as described in any one of claims 1 to 10.

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