Over-temperature and over-voltage protection circuit, circuit board, switching power supply and electronic equipment

Abstract

The invention relates to the technical field of over-temperature and over-voltage protection circuits, and discloses an over-temperature and over-voltage protection circuit, a circuit board, a switching power supply and electronic equipment. The over-temperature and over-voltage protection circuit comprises a trigger circuit, a controller, a temperature detection circuit and a voltage sampling circuit, wherein the temperature detection circuit generates a temperature detection signal at the second node according to the environment temperature, so that the trigger circuit triggers the controller to execute over-temperature protection operation. The voltage sampling circuit generates a voltage detection signal at the third node according to the external voltage, so that the trigger circuit triggers the controller to execute overvoltage protection operation. The temperature detection circuit and the voltage sampling circuit share the trigger circuit, so that the integration level of the over-temperature and over-voltage protection circuit is high. The detection results of the temperature detection circuit and the voltage sampling circuit are finally represented by the voltage of the first node, the controller only needs to open up a control pin to be electrically connected to the first node, and there is no need to open up an additional control pin for two functions, so that precious pin resources can be saved.

Description

Technical Field

[0001] The present invention relates to the technical field of over-temperature and over-voltage protection circuits, and in particular to an over-temperature and over-voltage protection circuit, a circuit board, a switching power supply and an electronic device. Background Art

[0002] Existing switching power supplies are usually equipped with over-temperature protection circuits and over-voltage protection circuits. When the operating temperature of the switching power supply is too high, the over-temperature protection circuit performs over-temperature protection operations. When the operating voltage of the switching power supply is too high, the over-voltage protection circuit performs over-voltage protection operations to avoid safety accidents caused by excessive temperature or voltage of the switching power supply, which is beneficial to improving the working reliability of the switching power supply.

[0003] In the switching power supply provided by the related art, the over-temperature protection circuit and the over-voltage protection circuit are separately provided, and the controller of the switching power supply needs to open two control pins to receive the feedback signal of the over-temperature protection circuit and the feedback signal of the over-voltage protection circuit respectively. Since the integration of the over-temperature protection circuit and the over-voltage protection circuit is not high, it is easy to cause the pin resources of the controller to be unable to meet the needs of other functions. Summary of the invention

[0004] One purpose of an embodiment of the present invention is to provide an over-temperature and over-voltage protection circuit, a circuit board, a switching power supply and an electronic device, aiming to solve the technical problem that the over-temperature and over-voltage protection circuit provided by the related technology has a low integration degree.

[0005] In a first aspect, an embodiment of the present invention provides an over-temperature and over-voltage protection circuit, comprising:

[0006] A trigger circuit includes a first node, a second node and a third node;

[0007] a controller, a control pin of the controller being electrically connected to the trigger circuit at the first node;

[0008] a temperature detection circuit, electrically connected to the trigger circuit at the second node, and configured to generate a temperature detection signal at the second node according to the ambient temperature, wherein the trigger circuit, in response to an input of the temperature detection signal, can control the voltage of the first node to be a trigger voltage, so that the controller performs an over-temperature protection operation according to the trigger voltage;

[0009] A voltage sampling circuit is electrically connected to the trigger circuit at the third node, and is used to generate a voltage detection signal at the third node according to an external voltage, wherein the trigger circuit responds to the input of the voltage detection signal and can control the voltage of the first node to be the trigger voltage, so that the controller performs an overvoltage protection operation according to the trigger voltage.

[0010] In a second aspect, an embodiment of the present invention provides a circuit board, comprising the above-mentioned over-temperature and over-voltage protection circuit.

[0011] In a third aspect, an embodiment of the present invention provides a switching power supply, comprising the above-mentioned circuit board.

[0012] In a fourth aspect, an embodiment of the present invention provides an electronic device, comprising the above-mentioned switching power supply.

[0013] In the over-temperature and over-voltage protection circuit provided in the embodiment of the present invention, the trigger circuit includes a first node, a second node and a third node, the control pin of the controller is electrically connected to the trigger circuit at the first node, and the temperature detection circuit is electrically connected to the trigger circuit at the second node, and is used to generate a temperature detection signal at the second node according to the ambient temperature, wherein the trigger circuit responds to the input of the temperature detection signal and can control the voltage of the first node to be a trigger voltage, so that the controller performs an over-temperature protection operation according to the trigger voltage. The voltage sampling circuit is electrically connected to the trigger circuit at the third node, and is used to generate a voltage detection signal at the third node according to an external voltage, wherein the trigger circuit responds to the input of the voltage detection signal and can control the voltage of the first node to be the trigger voltage, so that the controller performs an over-voltage protection operation according to the trigger voltage. First, the temperature detection circuit and the voltage sampling circuit share the trigger circuit, and both can trigger the trigger circuit, so that the trigger circuit controls the voltage of the first node to be the trigger voltage, and therefore, the temperature detection circuit, the voltage sampling circuit and the trigger circuit have a high degree of integration. In addition, the detection results of the temperature detection circuit and the voltage sampling circuit are ultimately represented by the voltage of the first node. The controller only needs to open a control pin electrically connected to the first node to perform over-temperature and over-voltage protection operations according to the trigger voltage of the first node. There is no need to open an extra control pin for the two functions, thereby saving valuable pin resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0015] Figure 1 A circuit principle block diagram of an over-temperature and over-voltage protection circuit provided for related technologies;

[0016] Figure 2 A schematic diagram of the circuit structure of an over-temperature and over-voltage protection circuit provided by an embodiment of the present invention;

[0017] Figure 3 A schematic diagram of the circuit structure of an over-temperature and over-voltage protection circuit provided by another embodiment of the present invention;

[0018] Figure 4 A schematic diagram of the circuit structure of an over-temperature and over-voltage protection circuit provided in yet another embodiment of the present invention;

[0019] Figure 5 A schematic diagram of the circuit structure of an over-temperature and over-voltage protection circuit provided in yet another embodiment of the present invention;

[0020] Figure 6 A schematic diagram of the circuit structure of an over-temperature and over-voltage protection circuit provided in yet another embodiment of the present invention;

[0021] Figure 7 A schematic diagram of the circuit structure of an over-temperature and over-voltage protection circuit provided in yet another embodiment of the present invention;

[0022] Figure 8 A schematic diagram of the circuit structure of an over-temperature and over-voltage protection circuit provided in yet another embodiment of the present invention;

[0023] Fig. 9 A schematic diagram of the circuit structure of an over-temperature and over-voltage protection circuit provided in yet another embodiment of the present invention;

[0024] Fig.10 A schematic diagram of the circuit structure of an over-temperature and over-voltage protection circuit provided in yet another embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] It should be noted that, if there is no conflict, the various features in the embodiments of the present invention can be combined with each other, all within the scope of protection of the present invention. In addition, although the functional modules are divided in the device schematic diagram and the logical order is shown in the flow chart, in some cases, the steps shown or described can be performed in a different order from the module division in the device or the flow chart. Furthermore, the words "first", "second", "third", etc. used in the present invention do not limit the data and execution order, but only distinguish the same items or similar items with basically the same functions and effects.

[0027] See also Figure 1The over-temperature and over-voltage protection circuit provided by the related technology includes an over-voltage protection unit 11, an over-temperature protection unit 12 and a controller 13, wherein the controller 13 provides a first pin FB and a second pin PRO, the first pin FB is electrically connected to the over-voltage protection unit 11, and the second pin PRO is electrically connected to the over-temperature protection unit 12.

[0028] The overvoltage protection unit 11 includes an overvoltage trigger circuit and a voltage regulator. When the external voltage V0 of the node B is normal, the overvoltage trigger circuit controls the voltage of the node A of the first pin FB to be within the normal voltage range, but the voltage regulator does not work. When the external voltage V0 is abnormal, the overvoltage trigger circuit controls the voltage of the node A of the first pin FB to be within the abnormal voltage range, and the controller 13 performs an overvoltage protection operation according to the voltage of the node A within the abnormal voltage range, and at the same time, the voltage regulator starts to work.

[0029] After the Zener diode works, the Zener diode and the overvoltage trigger circuit jointly pull down the external voltage V0 of the node B to obtain the voltage V0'. Although the voltage V0' is smaller than the external voltage V0, the external voltage V0 is pulled down to reduce the overvoltage risk, but the voltage V0' is not equal to 0, that is, the overvoltage protection unit 11 does not perform overvoltage protection by pulling the external voltage V0 down to 0. The non-zero voltage V0' may cause a risk of damage to the back-end devices.

[0030] The over-temperature protection unit 12 is used to detect the ambient temperature. When the ambient temperature is lower than the preset temperature, the over-temperature protection unit 12 controls the voltage of the node C of the second pin PRO to be within a normal voltage range. When the ambient temperature is higher than the preset temperature, the over-temperature protection unit 12 controls the voltage of the node C of the second pin PRO to be within an abnormal voltage range. The controller 13 performs an over-temperature protection operation according to the voltage of the node C within the abnormal voltage range.

[0031] In addition, since the ambient temperature sometimes fluctuates, the ambient temperature is sometimes greater than the preset temperature and sometimes less than the preset temperature, which causes the controller 13 to repeatedly switch back and forth between over-temperature protection operation and normal temperature control operation, which may further cause the output voltage to oscillate.

[0032] Based on this, an embodiment of the present invention provides an over-temperature and over-voltage protection circuit. Figure 2 The over-temperature and over-voltage protection circuit 200 includes a trigger circuit 300 , a controller 400 , a temperature detection circuit 500 and a voltage sampling circuit 600 .

[0033] The trigger circuit 300 includes a first node N1, a second node N2 and a third node N3. The trigger circuit 300 is configured with a temperature trigger threshold and a voltage trigger threshold.

[0034] The control pin PR0 of the controller 400 is electrically connected to the trigger circuit 300 at a first node N1.

[0035] The temperature detection circuit 500 is electrically connected to the trigger circuit 300 at the second node N2, and is used to generate a temperature detection signal at the second node N2 according to the ambient temperature, wherein the trigger circuit 300 responds to the input of the temperature detection signal and can control the voltage of the first node N1 to be a trigger voltage, so that the controller 400 performs an over-temperature protection operation according to the trigger voltage.

[0036] The ambient temperature is the temperature of the surrounding environment where the temperature detection circuit 500 is located, wherein the temperature detection circuit 500 can use a temperature sensor with a positive temperature coefficient or a negative temperature coefficient to detect the ambient temperature of the surrounding environment.

[0037] The trigger voltage is a voltage used to trigger the controller 400 to perform an over-temperature protection operation or an over-voltage protection operation. In some embodiments, the trigger voltage may be a low-level signal or a high-level signal.

[0038] In some embodiments, the trigger circuit 300 is configured with a temperature trigger threshold. The trigger circuit 300 responds to an input of a temperature detection signal and controls the voltage of the first node N1 according to the temperature detection signal and the temperature trigger threshold.

[0039] It is understandable that the trigger circuit 300 can be designed as a corresponding circuit structure, which is used to control the voltage of the first node N1 to be a trigger voltage or a normal voltage according to the temperature detection signal and the temperature trigger threshold. In some embodiments, when the temperature detection signal is greater than the temperature trigger threshold, the trigger circuit 300 controls the voltage of the first node N1 to be a trigger voltage. When the temperature detection signal is less than the temperature trigger threshold, the trigger circuit 300 controls the voltage of the first node N1 to be a normal voltage.

[0040] In some embodiments, when the temperature detection signal is less than the temperature trigger threshold, the trigger circuit 300 controls the voltage of the first node N1 to be a normal voltage. When the temperature detection signal is less than the temperature trigger threshold, the trigger circuit 300 controls the voltage of the first node N1 to be a trigger voltage.

[0041] The over-temperature protection operation includes the controller 400 pausing or stopping the operation of each circuit module, or starting the operation of the heat dissipation component, or reducing the output power or output current or output voltage, etc.

[0042] The voltage sampling circuit 600 is electrically connected to the trigger circuit 300 at the third node N3, and is used to generate a voltage detection signal at the third node N3 according to the external voltage, wherein the trigger circuit 300 responds to the input of the voltage detection signal and can control the voltage of the first node N1 to be a trigger voltage, so that the controller 400 performs an overvoltage protection operation according to the trigger voltage.

[0043] The external voltage is the output voltage of the circuit to be protected, wherein the circuit to be protected is a circuit that needs to perform over-temperature and over-voltage protection operations. In some embodiments, the circuit to be protected is a switching power supply circuit, and the external voltage is the output voltage of the secondary side of the switching power supply circuit.

[0044] In some embodiments, the trigger circuit 300 is configured with a voltage trigger threshold. The trigger circuit 300 responds to an input of a voltage detection signal and controls the voltage of the first node N1 according to the voltage detection signal and the voltage trigger threshold.

[0045] It is understandable that the trigger circuit 300 can be designed as a corresponding circuit structure, which is used to control the voltage of the first node N1 to be a trigger voltage or a normal voltage according to the voltage detection signal and the voltage trigger threshold. In some embodiments, when the voltage detection signal is greater than the voltage trigger threshold, the trigger circuit 300 controls the voltage of the first node N1 to be a trigger voltage. When the voltage detection signal is less than the voltage trigger threshold, the trigger circuit 300 controls the voltage of the first node N1 to be a normal voltage.

[0046] In some embodiments, when the voltage detection signal is less than the voltage trigger threshold, the trigger circuit 300 controls the voltage of the first node N1 to be a normal voltage. When the voltage detection signal is less than the voltage trigger threshold, the trigger circuit 300 controls the voltage of the first node N1 to be a trigger voltage.

[0047] In some embodiments, when the trigger voltage is a low level signal, the normal voltage is a high level signal. In some embodiments, when the trigger voltage is a high level signal, the normal voltage is a low level signal. It is understandable that the designer can design the specific circuit structure of the trigger circuit 300 according to the signal form of the trigger voltage and the normal voltage.

[0048] The overvoltage protection operation includes the controller 400 pausing or stopping the operation of each circuit module, or reducing the output power or output voltage, etc.

[0049] Since the temperature detection circuit 500 and the voltage sampling circuit 600 share the trigger circuit 300, both can trigger the trigger circuit 300, so that the trigger circuit 300 controls the voltage of the first node N1 to be the trigger voltage. Therefore, the temperature detection circuit 500, the voltage sampling circuit 600 and the trigger circuit 300 have a high degree of integration.

[0050] In addition, the detection results of the temperature detection circuit 500 and the voltage sampling circuit 600 are ultimately represented by the voltage of the first node N1. The controller 400 only needs to open a control pin electrically connected to the first node N1 to perform over-temperature and over-voltage protection operations according to the trigger voltage of the first node N1. There is no need to open an additional control pin for the two functions, thereby saving precious pin resources.

[0051] In some embodiments, see Figure 3 The trigger circuit 300 includes a signal comparison circuit 31 and a voltage control circuit 32 .

[0052] The signal comparison circuit 31 includes a fourth node N4. The signal comparison circuit 31 is electrically connected to the temperature detection circuit 500 at the second node N2, and is electrically connected to the voltage sampling circuit 600 at the third node N3. When the temperature detection signal is greater than a preset temperature trigger threshold, the signal comparison circuit 31 responds to the input of the temperature detection signal and can output an over-temperature trigger signal at the fourth node N4. Alternatively, when the voltage detection signal is greater than the preset voltage trigger threshold, the signal comparison circuit 31 responds to the input of the voltage detection signal and can output an over-voltage trigger signal at the fourth node N4.

[0053] In some embodiments, when the temperature detection signal is greater than the temperature trigger threshold, the signal comparison circuit 31 controls the fourth node N4 to output an over-temperature trigger signal. When the temperature detection signal is less than the temperature trigger threshold, the signal comparison circuit 31 controls the fourth node N4 to output a normal temperature signal.

[0054] The over-temperature trigger signal is used to trigger the voltage control circuit 32 to control the voltage of the first node N1 to be a trigger voltage. The normal temperature signal is used to trigger the voltage control circuit 32 to control the voltage of the first node N1 to be a normal voltage.

[0055] In some embodiments, when the over-temperature trigger signal is a high-level signal, the normal-temperature signal is a low-level signal. In some embodiments, when the over-temperature trigger signal is a low-level signal, the normal-temperature signal is a high-level signal. It is understandable that the designer can design the specific circuit structure of the signal comparison circuit 31 according to the signal forms of the over-temperature trigger signal and the normal-temperature signal.

[0056] In some embodiments, when the voltage detection signal is greater than the voltage trigger threshold, the signal comparison circuit 31 controls the fourth node N4 to output an overvoltage trigger signal. When the voltage detection signal is less than the voltage trigger threshold, the signal comparison circuit 31 controls the fourth node N4 to output a normal voltage signal.

[0057] The overvoltage trigger signal is used to trigger the voltage control circuit 32 to control the voltage of the first node N1 to be a trigger voltage. The normal voltage signal is used to trigger the voltage control circuit 32 to control the voltage of the first node N1 to be a normal voltage.

[0058] In some embodiments, when the overvoltage trigger signal is a high level signal, the normal voltage signal is a low level signal. In some embodiments, when the overvoltage trigger signal is a low level signal, the normal voltage signal is a high level signal. It is understandable that the designer can design the specific circuit structure of the signal comparison circuit 31 according to the signal forms of the overtemperature trigger signal and the normal temperature signal, the overvoltage trigger signal and the normal voltage signal.

[0059] The voltage control circuit 32 is electrically connected to the signal comparison circuit 31 at the fourth node N4 , and is used to control the voltage of the first node N1 to be a trigger voltage according to the over-temperature trigger signal or the over-voltage trigger signal.

[0060] In some embodiments, when the over-temperature trigger signal is a high-level signal, the voltage control circuit 32 controls the voltage of the first node N1 to be a trigger voltage, and when the over-voltage trigger signal is a high-level signal, the voltage control circuit 32 controls the voltage of the first node N1 to be a trigger voltage, wherein the trigger voltage is a low-level signal.

[0061] In some embodiments, when the over-temperature trigger signal is a low-level signal, the voltage control circuit 32 controls the voltage of the first node N1 to be a trigger voltage, and when the over-voltage trigger signal is a low-level signal, the voltage control circuit 32 controls the voltage of the first node N1 to be a trigger voltage, wherein the trigger voltage is a high-level signal.

[0062] In some embodiments, when the over-temperature trigger signal is a high-level signal, the voltage control circuit 32 controls the voltage of the first node N1 to be a trigger voltage, and when the over-voltage trigger signal is a high-level signal, the voltage control circuit 32 controls the voltage of the first node N1 to be a trigger voltage, wherein the trigger voltage is a high-level signal.

[0063] In some embodiments, when the over-temperature trigger signal is a low-level signal, the voltage control circuit 32 controls the voltage of the first node N1 to be a trigger voltage, and when the over-voltage trigger signal is a low-level signal, the voltage control circuit 32 controls the voltage of the first node N1 to be a trigger voltage, wherein the trigger voltage is a low-level signal.

[0064] The signal comparison circuit 31 provided in this embodiment integrates a circuit structure that can compare the size of the temperature detection signal with a preset temperature trigger threshold or the size of the voltage detection signal with a preset voltage trigger threshold, which is conducive to reliable and quantitative over-temperature monitoring and over-voltage monitoring with a highly integrated circuit structure.

[0065] In some embodiments, see Figure 4 The signal comparison circuit 31 includes a first three-terminal regulator 311 and a second three-terminal regulator 312 .

[0066] The reference electrode of the first three-terminal regulator 311 is electrically connected to the temperature detection circuit 500, the cathode is electrically connected to the fourth node N4, the anode is grounded, the reference electrode of the first three-terminal regulator 311 is the second node N2, when the temperature detection signal is greater than the temperature trigger threshold, the first three-terminal regulator 311 controls the fourth node N4 to output an over-temperature trigger signal. When the temperature detection signal is less than the temperature trigger threshold, the first three-terminal regulator 311 controls the fourth node N4 to output a normal temperature signal.

[0067] The reference electrode of the second three-terminal regulator 312 is electrically connected to the voltage sampling circuit 600, the cathode is electrically connected to the fourth node N4, the anode is grounded, the voltage control circuit 32 is electrically connected to the fourth node N4, and the reference electrode of the second three-terminal regulator 312 is the third node N3, wherein, when the voltage detection signal is greater than the voltage trigger threshold, the second three-terminal regulator 312 controls the fourth node N4 to output an overvoltage trigger signal. When the voltage detection signal is less than the voltage trigger threshold, the second three-terminal regulator 312 controls the fourth node N4 to output a normal voltage signal.

[0068] This embodiment uses a three-terminal regulator as the main body of the signal comparison circuit 31. The threshold voltage of the three-terminal regulator is adjustable and the performance is relatively stable and reliable. Therefore, the working performance of the signal comparison circuit 31 provided in this embodiment is also relatively stable and reliable, and the temperature trigger threshold or voltage trigger threshold can be flexibly set according to user needs, thereby meeting the over-temperature and over-voltage monitoring needs of various scenarios.

[0069] In some embodiments, see Figure 5 The signal comparison circuit 31 further includes a filter circuit 313, which is electrically connected between the fourth node N4 and the ground. The filter circuit 313 is used to filter the voltage of the fourth node N4.

[0070] See also Figure 6 The filter circuit 313 includes a capacitor C1, one end of which is electrically connected to the fourth node N4, and the other end is grounded. The capacitor C1 is used to filter the voltage of the fourth node N4, so that the voltage control circuit 32 can reliably control the voltage of the first node N1 according to the voltage of the fourth node N4.

[0071] In some embodiments, see Figure 7 The voltage control circuit 32 includes an optocoupler primary circuit 321 and an optocoupler secondary circuit 322 .

[0072] The optocoupler primary circuit 321 is electrically connected to the signal comparison circuit 31 at the fourth node N4.

[0073] The optocoupler secondary circuit 322 is electrically connected to the controller 400 at the first node N1. When the voltage of the fourth node N4 is greater than the voltage of the over-temperature trigger signal or the voltage of the over-voltage trigger signal, the optocoupler primary circuit 321 triggers the optocoupler secondary circuit 322 to control the voltage of the first node N1 to be the trigger voltage.

[0074] This embodiment uses optocoupler isolation to transmit over-temperature detection results or over-voltage detection results to the controller 400, which can isolate the controller 400 from noise, which is beneficial for the controller 400 to accurately and reliably determine whether the voltage of the first node N1 is a trigger voltage, and then reliably perform over-temperature protection operations or over-voltage protection operations.

[0075] Please continue reading Figure 6 The primary circuit 321 of the optocoupler includes a light emitting diode ZD, the anode of the light emitting diode ZD is used to receive the input of the internal voltage Vcc, and the cathode of the light emitting diode ZD is electrically connected to the fourth node N4. The secondary circuit 322 of the optocoupler includes a light receiving diode SD, the collector of the light receiving diode SD is electrically connected to the first node N1, and the emitter of the light receiving diode SD is grounded. The internal voltage Vcc is usually relatively constant or stable, and the internal voltage Vcc is usually the system voltage of the circuit to be protected.

[0076] When the light emitting diode ZD is turned on, the light emitting diode ZD emits light, and the light receiving diode SD enters the on state according to the light, and the voltage of the first node N1 can be pulled to a low level signal, that is, the trigger voltage is a low level signal. When the light emitting diode ZD is turned off, the light emitting diode ZD does not emit light, and the light receiving diode SD enters the off state, and the voltage of the first node N1 can be pulled to a high level signal, that is, the normal voltage is a high level signal.

[0077] Please continue reading Figure 6 The temperature detection circuit 500 includes a negative temperature coefficient resistor NTC and a first resistor R1, one end of the negative temperature coefficient resistor NTC is used to receive the input of the internal voltage Vcc, the other end of the negative temperature coefficient resistor NTC is electrically connected to one end of the first resistor R1 at the second node N2, and the other end of the first resistor R1 is grounded.

[0078] When the ambient temperature is higher, the negative temperature coefficient resistor NTC is smaller, and the voltage of the second node N2 becomes larger. When the ambient temperature is greater than the preset temperature threshold, the voltage of the second node N2 is greater than the reference voltage (such as 2.5V) of the first three-terminal regulator 311, so the first three-terminal regulator 311 enters the on state, and the voltage of the fourth node N4 is pulled down.

[0079] When the ambient temperature is lower, the negative temperature coefficient resistor NTC is larger, and the voltage of the second node N2 becomes smaller. When the ambient temperature is lower than the preset temperature threshold, the voltage of the second node N2 is lower than the reference voltage (such as 2.5V) of the first three-terminal regulator 311, so the first three-terminal regulator 311 enters the off state, and the voltage of the fourth node N4 is pulled up.

[0080] Please continue reading Figure 6 The voltage sampling circuit 600 includes a second resistor R2 and a third resistor R3. One end of the second resistor R2 is used to receive an input of an external voltage Vo. The other end of the second resistor R2 and one end of the third resistor R3 are electrically connected to a third node N3. The other end of the third resistor R3 is grounded.

[0081] When the external voltage Vo is larger, the voltage of the third node N3 becomes larger. When the external voltage Vo is greater than the preset overvoltage threshold, the voltage of the third node N3 is greater than the reference voltage (such as 2.5V) of the second three-terminal regulator 312, so the second three-terminal regulator 312 enters the on state, and the voltage of the fourth node N4 is pulled down.

[0082] When the external voltage Vo is smaller, the voltage of the third node N3 becomes smaller. When the external voltage Vo is less than the preset overvoltage threshold, the voltage of the third node N3 is smaller than the reference voltage (e.g., 2.5V) of the second three-terminal regulator 312, so the second three-terminal regulator 312 enters the off state, and the voltage of the fourth node N4 is pulled up.

[0083] In some embodiments, see Figure 8 The over-temperature and over-voltage protection circuit further includes a state maintaining circuit 700, which is electrically connected between the second node N2 and the third node N3 of the trigger circuit 300. When the trigger circuit 300 controls the voltage of the first node N1 to be the trigger voltage, the trigger circuit 300 outputs a state maintaining signal to the state maintaining circuit 700, so that the state maintaining circuit 700 responds to the state maintaining signal and controls the trigger circuit 300 to maintain the voltage of the first node N1 equal to the trigger voltage. When the trigger circuit 300 controls the voltage of the first node N1 to be the normal voltage, the trigger circuit 300 does not output the state maintaining signal to the state maintaining circuit 700, so the state maintaining circuit 700 does not apply an action signal to the trigger circuit 300.

[0084] When the ambient temperature fluctuates and causes the temperature detection signal to change frequently, or when the external voltage fluctuates and causes the voltage detection signal to change frequently, the state maintaining circuit 700 can control the trigger circuit 300 to maintain the voltage of the first node N1 equal to the trigger voltage according to the state maintaining signal, thereby avoiding the controller 400 from frequently switching between over-temperature protection operation and normal operation, or frequently switching between over-voltage protection operation and normal operation, which is beneficial to improving the operating stability of the over-temperature and over-voltage protection circuit.

[0085] In some embodiments, see Fig. 9 The state maintaining circuit 700 includes: a switch circuit 71 , a first clamping circuit 72 and a second clamping circuit 73 .

[0086] The switch circuit 71 is electrically connected to the fourth node N4 of the trigger circuit 300 and is used to receive the state maintenance signal through the fourth node N4. The switch circuit 71 includes a fifth node N5 and a sixth node N6. The fifth node N5 is used to receive the input of the internal voltage Vcc.

[0087] The first clamping circuit 72 is electrically connected between the second node N2 and the sixth node N6, wherein when the switch circuit 71 enters the on state in response to the state maintenance signal, the switch circuit 71 and the first clamping circuit 72 form a first clamping branch, and the first clamping branch can provide a first clamping voltage at the second node N2, and the first clamping voltage is used to control the trigger circuit 300 to maintain the voltage of the first node N1 equal to the trigger voltage.

[0088] The second clamping circuit 73 is electrically connected between the third node N3 and the sixth node N6, wherein when the switch circuit 71 enters the on state in response to the state maintenance signal, the switch circuit 71 and the second clamping circuit 73 form a second clamping branch, and the second clamping branch can provide a second clamping voltage at the third node N3, and the second clamping voltage is used to control the trigger circuit 300 to maintain the voltage of the first node N1 equal to the trigger voltage.

[0089] The first clamping circuit 72 and the second clamping circuit 73 share the switch circuit 71, wherein the first clamping circuit 72 can form a first clamping branch with the switch circuit 71, and the second clamping circuit 73 can form a second clamping branch with the switch circuit 71. The state maintaining circuit 700 of this embodiment has a high degree of integration and can be compatible to help achieve the purpose of over-temperature monitoring and over-voltage detection.

[0090] In some embodiments, see Fig.10 The switch circuit 71 includes a PNP tube Q1, the emitter of the PNP tube Q1 is used to receive the input of the internal voltage Vcc, the base is electrically connected to the fourth node N4 of the trigger circuit 300, and the collector is electrically connected to the first clamping circuit 72, wherein the emitter is the fifth node N5 and the collector is the sixth node N6.

[0091] The PNP transistor Q1 can form a first clamping branch with the first clamping circuit 72. When the voltage of the fourth node N4 is a low-level signal, the base of the PNP transistor Q1 is pulled down, and the PNP transistor Q1 meets the conduction condition, so the PNP transistor Q1 enters the conduction state. When the PNP transistor Q1 enters the conduction state, the first clamping voltage provided by the first clamping branch to the reference electrode of the first three-terminal regulator 311 is approximately equal to the sum of the CE junction voltage between the collector and the emitter of the PNP transistor Q1 and the voltage across the first clamping circuit 72. The sum of the CE junction voltage and the voltage across the first clamping circuit 72 is greater than the reference voltage of the first three-terminal regulator 311, so that when the ambient temperature is too high, the first three-terminal regulator 311 can continuously and stably enter the conduction state, continuously and stably pull down the voltage of the fourth node N4, and then prompt the trigger circuit 300 to maintain the voltage of the first node N1 equal to the trigger voltage.

[0092] In some embodiments, please refer to Fig.10The switch circuit 71 further includes a fourth resistor R4, a fifth resistor R5 and a sixth resistor R6, one end of the fourth resistor R4 is used to be applied with the internal voltage Vcc, the other end of the fourth resistor R4 is electrically connected to the fifth node N5, one end of the fifth resistor R5 is used to be applied with the internal voltage Vcc, the other end of the fifth resistor R5 is electrically connected to one end of the sixth resistor R6, and the other end of the sixth resistor R6 is electrically connected to the fourth node N4. The fourth resistor R4, the fifth resistor R5 and the sixth resistor R6 can play the role of current limiting and voltage dividing.

[0093] In some embodiments, the first clamp circuit 72 and the second clamp circuit 73 may be zener diodes or ordinary diodes.

[0094] Please continue reading Fig.10 The first clamping circuit 72 includes a first diode D1 , an anode of the first diode D1 is electrically connected to the sixth node N6 , and a cathode of the first diode D1 is electrically connected to the second node N2 .

[0095] Please continue reading Fig.10 The second clamping circuit 73 includes a second diode D2, an anode of the second diode D2 is electrically connected to the sixth node N6, and a cathode of the second diode D2 is electrically connected to the third node N3.

[0096] In order to explain in detail the working principle of the over-temperature and over-voltage protection circuit 200 provided in the embodiment of the present invention, the following is combined with Fig.10 To elaborate on this, it is understandable that Fig.10 Only one implementation is provided to help understanding, and does not limit the protection scope of the embodiments of the present invention. The details are as follows:

[0097] a. The over-temperature protection process is as follows:

[0098] When the ambient temperature is greater than the preset temperature threshold, the resistance of the negative temperature coefficient resistor NTC decreases, so that the voltage across the first resistor R1 increases, and the voltage of the second node N2 is used as a temperature detection signal, and the temperature detection signal will be greater than the temperature trigger threshold, wherein the temperature trigger threshold is the reference voltage of the first three-terminal regulator 311. When the temperature detection signal is greater than the temperature trigger threshold, the first three-terminal regulator 311 enters the on state to pull down the voltage of the fourth node N4 to a low-level signal.

[0099] Since the voltage of the fourth node N4 is pulled low, the light emitting diode ZD meets the conduction condition, therefore, the light emitting diode ZD emits light, and the light receiving diode SD enters the conduction state according to the light, and the voltage of the first node N1 can be pulled to a low level signal, that is, the trigger voltage is a low level signal. When the controller 400 detects that the voltage of the first node N1 is a low level signal, it performs the over-temperature protection operation.

[0100] At the same time, since the base of the PNP tube Q1 is pulled low, the PNP tube Q1 meets the conduction condition and enters the conduction state. When the PNP tube Q1 enters the conduction state, the voltage of the reference electrode of the first three-terminal regulator 311 is clamped to be equal to the sum of the voltage across the fourth resistor R4, the CE junction voltage of the PNP tube Q1 and the conduction voltage drop of the first diode D1. The sum of the voltage across the fourth resistor R4, the CE junction voltage of the PNP tube Q1 and the conduction voltage drop of the first diode D1 is greater than the reference voltage 2.5V of the first three-terminal regulator 311, so that the first three-terminal regulator 311 can continuously and stably enter the conduction state, continuously and stably pull down the voltage of the fourth node N4, thereby prompting the light emitting diode ZD to continuously emit light, and the light receiving diode SD continuously enters the conduction state according to the light, continuously pulls the voltage of the first node N1 to a low level signal, and the controller 400 continuously detects that the voltage of the first node N1 is a low level signal, and continuously performs the over-temperature protection operation.

[0101] When the ambient temperature is lower than the preset temperature threshold, the resistance of the negative temperature coefficient resistor NTC increases, so that the voltage across the first resistor R1 decreases, and the voltage of the second node N2 is lower than the temperature trigger threshold. When the temperature detection signal is lower than the temperature trigger threshold, the first three-terminal regulator 311 enters the off state to pull up the voltage of the fourth node N4 to a high level signal.

[0102] Since the voltage of the fourth node N4 is pulled high, the light emitting diode ZD does not meet the conduction condition, so the light emitting diode ZD does not emit light, and the light receiving diode SD enters the off state, so that the voltage of the first node N1 is pulled to a high level signal. When the controller 400 detects that the voltage of the first node N1 is a high level signal, it performs normal operation. At the same time, since the base of the PNP tube Q1 is pulled high, the PNP tube Q1 does not meet the conduction condition and enters the off state.

[0103] b. The overvoltage protection process is as follows:

[0104] When the external voltage is greater than the preset overvoltage threshold, the voltage across the third resistor R3 increases, and the voltage of the third node N3 is used as a voltage detection signal. The voltage detection signal will be greater than the voltage trigger threshold, wherein the voltage trigger threshold is the reference voltage of the second three-terminal regulator 312. When the voltage detection signal is greater than the voltage trigger threshold, the second three-terminal regulator 312 enters the on state to pull down the voltage of the fourth node N4 to a low level signal. Since the voltage of the fourth node N4 is pulled down, the light-emitting diode ZD meets the conduction condition, and therefore, the light-emitting diode ZD emits light, and the light-receiving diode SD enters the on state according to the light, and can pull the voltage of the first node N1 to a low level signal, that is, the trigger voltage is a low level signal. When the controller 400 detects that the voltage of the first node N1 is a low level signal, it performs an over-temperature protection operation.

[0105] At the same time, since the base of the PNP tube Q1 is pulled low, the PNP tube Q1 meets the conduction condition and enters the conduction state. When the PNP tube Q1 enters the conduction state, the voltage of the reference electrode of the second three-terminal regulator 312 is clamped to be equal to the sum of the voltage across the fourth resistor R4, the CE junction voltage of the PNP tube Q1 and the conduction voltage drop of the second diode D2. The sum of the voltage across the fourth resistor R4, the CE junction voltage of the PNP tube Q1 and the conduction voltage drop of the second diode D2 is greater than the reference voltage 2.5V of the second three-terminal regulator 312, so that the second three-terminal regulator 312 can continuously and stably enter the conduction state, continuously and stably pull down the voltage of the fourth node N4, thereby prompting the light emitting diode ZD to continuously emit light, and the light receiving diode SD continuously enters the conduction state according to the light, continuously pulls the voltage of the first node N1 to a low level signal, and the controller 400 continuously detects that the voltage of the first node N1 is a low level signal, and continuously performs the over-temperature protection operation.

[0106] When the external voltage is less than the preset overvoltage threshold, the voltage across the third resistor R3 decreases, and the voltage at the third node N3 is less than the voltage trigger threshold. When the voltage detection signal is less than the voltage trigger threshold, the second three-terminal regulator 312 enters the off state to pull up the voltage of the fourth node N4 to a high level signal. Since the voltage of the fourth node N4 is pulled up, the light-emitting diode ZD does not meet the conduction condition, so the light-emitting diode ZD does not emit light, and the light-receiving diode SD enters the off state, so that the voltage of the first node N1 is pulled to a high level signal. When the controller 400 detects that the voltage of the first node N1 is a high level signal, it performs normal operation. At the same time, since the base of the PNP tube Q1 is pulled up, the PNP tube Q1 does not meet the conduction condition and enters the off state.

[0107] As another aspect of an embodiment of the present invention, an embodiment of the present invention provides a circuit board. The circuit board includes the over-temperature and over-voltage protection circuit described in each of the above embodiments, wherein the circuit board can be spliced ​​by multiple circuit sub-boards, and other circuits in the over-temperature and over-voltage protection circuit can be arranged on different circuit sub-boards respectively. When the function of the over-temperature and over-voltage protection circuit needs to be realized, the user can splice the various circuit sub-boards into a circuit board with the over-temperature and over-voltage protection circuit.

[0108] As another aspect of an embodiment of the present invention, an embodiment of the present invention provides a switching power supply, and the switching power supply includes the circuit board described in each of the above embodiments.

[0109] As another aspect of the present invention, the present invention provides an electronic device, which includes the switching power supply described in the above embodiments, wherein the electronic device includes a display, a television, a tablet computer, a desktop computer, a laptop computer, an air conditioner, etc.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other changes in different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An over-temperature and over-voltage protection circuit, characterized in that: include: A trigger circuit includes a first node, a second node and a third node; a controller, a control pin of the controller being electrically connected to the trigger circuit at the first node; a temperature detection circuit, electrically connected to the trigger circuit at the second node, and configured to generate a temperature detection signal at the second node according to the ambient temperature, wherein the trigger circuit, in response to an input of the temperature detection signal, can control the voltage of the first node to be a trigger voltage, so that the controller performs an over-temperature protection operation according to the trigger voltage; A voltage sampling circuit is electrically connected to the trigger circuit at the third node, and is used to generate a voltage detection signal at the third node according to an external voltage, wherein the trigger circuit responds to the input of the voltage detection signal and can control the voltage of the first node to be the trigger voltage, so that the controller performs an overvoltage protection operation according to the trigger voltage.

2. The over-temperature and over-voltage protection circuit according to claim 1, characterized in that: The trigger circuit comprises: A signal comparison circuit, comprising a fourth node, electrically connected to the temperature detection circuit at the second node, and electrically connected to the voltage sampling circuit at the third node, wherein when the temperature detection signal is greater than a preset temperature trigger threshold, the signal comparison circuit responds to the input of the temperature detection signal and may output an over-temperature trigger signal at the fourth node, or, when the voltage detection signal is greater than a preset voltage trigger threshold, the signal comparison circuit responds to the input of the voltage detection signal and may output an over-voltage trigger signal at the fourth node; A voltage control circuit is electrically connected to the signal comparison circuit at the fourth node, and is used to control the voltage of the first node to be a trigger voltage according to the over-temperature trigger signal or the over-voltage trigger signal.

3. The over-temperature and over-voltage protection circuit according to claim 2, characterized in that: The signal comparison circuit comprises: A first three-terminal regulator, wherein a reference electrode of the first three-terminal regulator is electrically connected to the temperature detection circuit, a cathode is electrically connected to the fourth node, an anode is grounded, a reference electrode of the first three-terminal regulator is the second node, and when the temperature detection signal is greater than a temperature trigger threshold, the first three-terminal regulator controls the fourth node to output the over-temperature trigger signal; A second three-terminal regulator, wherein the reference pole of the second three-terminal regulator is electrically connected to the voltage sampling circuit, the cathode is electrically connected to the fourth node, the anode is grounded, the voltage control circuit is electrically connected to the fourth node, the reference pole of the second three-terminal regulator is the third node, wherein when the voltage detection signal is greater than the voltage trigger threshold, the second three-terminal regulator controls the fourth node to output the overvoltage trigger signal.

4. The over-temperature and over-voltage protection circuit according to claim 2, characterized in that: The voltage control circuit comprises: an optocoupler primary circuit, electrically connected to the signal comparison circuit at the fourth node; The optocoupler secondary circuit is electrically connected to the controller at the first node, and when the voltage of the fourth node is greater than the voltage of the over-temperature trigger signal or the voltage of the over-voltage trigger signal, the optocoupler primary circuit triggers the optocoupler secondary circuit to control the voltage of the first node to be a trigger voltage.

5. The over-temperature and over-voltage protection circuit according to any one of claims 1 to 4, characterized in that: It also includes a state maintaining circuit, which is electrically connected between the second node and the third node of the trigger circuit. When the trigger circuit controls the voltage of the first node to be a trigger voltage, the trigger circuit outputs a state maintaining signal to the state maintaining circuit, so that the state maintaining circuit responds to the state maintaining signal and controls the trigger circuit to maintain the voltage of the first node equal to the trigger voltage.

6. The over-temperature and over-voltage protection circuit according to claim 5, characterized in that: The state maintaining circuit comprises: a switch circuit, electrically connected to a fourth node of the trigger circuit, and configured to receive the state maintaining signal through the fourth node, the switch circuit comprising a fifth node and a sixth node, the fifth node being configured to receive an input of an internal voltage; a first clamping circuit electrically connected between the second node and the sixth node, wherein when the switch circuit enters the on state in response to the state maintaining signal, the switch circuit and the first clamping circuit form a first clamping branch, the first clamping branch can provide a first clamping voltage at the second node, and the first clamping voltage is used to control the trigger circuit to maintain the voltage of the first node equal to the trigger voltage; A second clamping circuit is electrically connected between the third node and the sixth node, wherein when the switch circuit enters a conductive state in response to the state maintaining signal, the switch circuit and the second clamping circuit form a second clamping branch, and the second clamping branch can provide a second clamping voltage at the third node, and the second clamping voltage is used to control the trigger circuit to maintain the voltage of the first node equal to the trigger voltage.

7. The over-temperature and over-voltage protection circuit according to claim 6, characterized in that: The switching circuit includes a PNP tube, the emitter of the PNP tube is used to receive the input of the internal voltage, the base is electrically connected to the fourth node of the trigger circuit, and the collector is electrically connected to the first clamping circuit, wherein the emitter is the fifth node and the collector is the sixth node.

8. The over-temperature and over-voltage protection circuit according to claim 6, characterized in that: The first clamping circuit includes a first diode, an anode of the first diode is electrically connected to the sixth node, and a cathode of the first diode is electrically connected to the second node.

9. The over-temperature and over-voltage protection circuit according to claim 6, characterized in that: The second clamping circuit includes a second diode, an anode of the second diode is electrically connected to the sixth node, and a cathode of the second diode is electrically connected to the third node.

10. The over-temperature and over-voltage protection circuit according to any one of claims 1 to 4, characterized in that: The temperature detection circuit includes a negative temperature coefficient resistor and a first resistor, one end of the negative temperature coefficient resistor is used to receive an input of an internal voltage, the other end of the negative temperature coefficient resistor is electrically connected to one end of the first resistor at the second node, and the other end of the first resistor is grounded.

11. The over-temperature and over-voltage protection circuit according to any one of claims 1 to 4, characterized in that: The voltage sampling circuit includes a second resistor and a third resistor, one end of the second resistor is used to receive an input of an external voltage, the other end of the second resistor and one end of the third resistor are electrically connected to the third node, and the other end of the third resistor is grounded.

12. A circuit board, characterized in that: The invention comprises an over-temperature and over-voltage protection circuit as claimed in any one of claims 1 to 11.

13. A switching power supply, characterized in that: Comprising the circuit board as claimed in claim 12.

14. An electronic device, characterized in that: Comprising the switching power supply as claimed in claim 13.

Images