A load detection circuit and circuit board assembly

Abstract

The embodiment of the present invention relates to the field of electronic circuit design, and discloses a detection circuit and circuit board assembly of a load. The circuit includes: a power supply, a switch module, a comparison module and a constant current module; the positive pole of the power supply is connected to the first end of the switch module, the second end of the switch module is used to connect the first end of the load, the negative pole of the power supply is grounded, and is used to connect the second end of the load, the output end of the constant current module is connected to the second end of the switch module, the second end of the switch module is also connected to the first end of the comparison module, the second end of the comparison module is used to receive a first voltage threshold, the third end of the comparison module is connected to the negative pole of the power supply, and the fourth end of the comparison module is connected to the third end of the switch module. When the detection circuit detects that the load has been connected to the circuit, the application will turn on the power supply circuit between the power supply and the load, effectively improving the safety of the power supply circuit.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of electronic circuit design, and in particular to a load detection circuit and a circuit board assembly. Background Art

[0002] A traditional power supply is usually provided with two output terminals for connecting to a load or accessing a power grid. These two output terminals are usually exposed outside the power supply but have the ability to supply high current.

[0003] If the two output terminals of the power supply are connected by accident due to wires, insects or other reasons, the power supply will be short-circuited and sparks will occur. In severe cases, the power supply and the circuit where the power supply is located may be damaged, and even a fire may occur. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a load detection circuit and a circuit board assembly, which turns on the power supply circuit between the power supply and the load only when the detection circuit detects that the load has been connected to the circuit, thereby effectively improving the safety of the power supply circuit.

[0005] To solve the above technical problems, an embodiment of the present invention provides a load detection circuit, including: a power supply, a switch module, a comparison module and a constant current module; the positive electrode of the power supply is connected to the first end of the switch module, the second end of the switch module is used to connect the first end of the load, the negative electrode of the power supply is grounded, and is used to connect the second end of the load, the output end of the constant current module is connected to the second end of the switch module, the second end of the switch module is also connected to the first end of the comparison module, the second end of the comparison module is used to receive a first voltage threshold, the third end of the comparison module is connected to the negative electrode of the power supply, and the fourth end of the comparison module is connected to the third end of the switch module; the comparison module is used to control the switch module to be turned on when the voltage at the first end of the comparison module is less than the first voltage threshold.

[0006] An embodiment of the present invention further provides a circuit board assembly, comprising the above-mentioned load detection circuit.

[0007] In an embodiment of the present invention, a comparison module is provided so that the comparison module can determine whether the load is currently connected to the circuit by detecting the voltage at the first end of the comparison module and the size of the first voltage threshold, and only when the load is currently connected to the circuit, the switch module is controlled to be turned on so that the load is powered by the power supply, thereby limiting the maximum power supply current when the load is not connected, and effectively improving the safety of the power supply circuit. If the load is connected after the output end of the circuit has a large current supply capability, if the load is capacitive, the current at the output end of the circuit will transiently surge at the moment of connecting the load, and a fire accident may occur in severe cases. In an embodiment of the present application, when it is detected that the load has been connected to the circuit, the power supply circuit between the power supply and the load is softly turned on so that the current at the output end increases slowly, thereby eliminating the spark caused by the current surge, and further improving the safety of the power supply circuit.

[0008] In some embodiments, the comparison module includes: a first resistor, a second resistor, a first comparator and a first MOS tube, the first MOS tube is an NMOS tube; the first end of the first resistor serves as the first end of the comparison module, the second end of the first resistor is connected to the first end of the second resistor, the second end of the second resistor serves as the third end of the comparison module, the second end of the first resistor is connected to the inverting input end of the first comparator, the in-phase input end of the first comparator serves as the second end of the comparison module, the output end of the first comparator is connected to the gate of the first MOS tube, the source of the first MOS tube is connected to the third end of the comparison module, and the drain of the first MOS tube serves as the fourth end of the comparison module. In this embodiment, when the load is not connected to the circuit, the voltage at the reverse input terminal of the first comparator is greater than the first voltage threshold received by the in-phase input terminal. At this time, the output terminal of the first comparator will output a low level to the gate of the first MOS tube, and the first MOS tube will be disconnected, so that the comparison module can output a high level to the switch module; when the load is connected to the circuit, due to the voltage division effect of the load, the voltage at the reverse input terminal of the first comparator will be less than the first voltage threshold received by the in-phase input terminal. At this time, the output terminal of the first comparator will output a high level to the gate of the first MOS tube, and the first MOS tube will be turned on to lower the gate voltage of the second MOS tube.

[0009] In some embodiments, the switch module includes a second MOS tube, which is a PMOS tube; the source of the second MOS tube serves as the first end of the switch module, the drain of the second MOS tube serves as the second end of the switch module, and the gate of the second MOS tube serves as the third end of the switch module. In this embodiment, a specific implementation of the switch module is provided, and when the load is not connected to the circuit, the comparison module outputs a high impedance to the switch module, and the second MOS tube is in a disconnected state; when the load is connected to the circuit, the comparison module outputs a low impedance to the switch module, and the second MOS tube is in a conducting state, so that the power supply supplies power to the load.

[0010] In some embodiments, the switch module further includes a first capacitor, a first end of the first capacitor is connected to the first end of the switch module, and a second end of the first capacitor is connected to the third end of the switch module. In this embodiment, before the second MOS tube is turned on, the first capacitor will be charged first, until the voltage across the first capacitor is greater than the turn-on voltage of the second MOS tube, the second MOS tube will be turned on, that is, the embodiment of the present application sets a slow start process for the second MOS tube, prolonging the time for the second MOS tube to pass through the linear region to prevent the charging current from being too large, further improving the safety of the power supply circuit.

[0011] In some embodiments, the comparison module further includes a second capacitor, a first end of the second capacitor is connected to the first end of the first resistor, and a second end of the second capacitor is connected to the second end of the first resistor. In this embodiment, during the process of the output voltage starting to rise, a current will flow through the second capacitor. Compared with only setting the first resistor, the current flowing through the total resistance obtained by connecting the second capacitor in parallel with the first resistor will be larger, which can make the first comparator reach the threshold voltage earlier to output a low level, so that the first MOS tube and the second MOS tube are both in the cut-off state, preventing the second MOS tube from jittering due to false triggering, and effectively improving the reliability of the circuit.

[0012] In some embodiments, the comparison module further includes a diode, the positive electrode of the diode is connected to the second end of the second resistor, and the negative electrode of the diode is connected to the first end of the second resistor. In this embodiment, if the load is short-circuited, due to the voltage across the second capacitor, the voltage at the inverting input of the first comparator will be negative, which may cause damage to the first comparator. By adding a diode, the embodiment of the present application can clamp the voltage at the inverting input of the first comparator to not less than -0.7V, thereby protecting the first comparator and improving the safety of the circuit under extreme conditions.

[0013] In some embodiments, the comparison module further includes a third resistor and / or a third capacitor; a first end of the third resistor is connected to the non-inverting input of the first comparator, a second end of the third resistor is connected to the output of the first comparator, and / or a first end of the third capacitor is connected to the non-inverting input of the first comparator, a second end of the third capacitor is connected to the output of the first comparator. In this embodiment, by setting the third resistor and / or the third capacitor to form a feedback loop of the first comparator, the first comparator can be made to work more stably.

[0014] In some embodiments, the constant current module includes a voltage source, a first triode, a second triode, a third triode and a fourth resistor, the output voltage of the voltage source is greater than the output voltage of the power supply, the first triode, the second triode and the third triode are all PNP triodes; the negative electrode of the voltage source is grounded, the positive electrode of the voltage source is connected to the emitter of the first triode, the collector of the first triode is connected to the first end of the fourth resistor, the second end of the fourth resistor is grounded, the base of the first triode is connected to the base of the second triode, the emitter of the first triode is connected to the emitter of the second triode, the collector of the second triode is connected to the emitter of the third triode, the collector of the second triode is also connected to the base of the second triode, the collector of the third triode is used as the output end of the constant current module, and the base of the third triode is connected to the first end of the fourth resistor. In this embodiment, the technician can adjust the current output from the constant current module to the comparison module by adjusting the resistance value of the fourth resistor to meet various different application scenarios.

[0015] In some embodiments, the circuit also includes a short-circuit detection module, wherein the first input end of the short-circuit detection module is used to receive a second voltage threshold, the second input end of the short-circuit detection module is connected to the inverting input end of the first comparator, the first output end of the short-circuit detection module is connected to the first end of the switch module, and the second output end of the short-circuit detection module is connected to the third end of the switch module; the short-circuit detection module includes a second comparator, a fourth transistor and a fifth transistor, the fourth transistor is an NPN transistor, the fifth transistor is a PNP transistor, the same-direction input end of the second comparator serves as the first input end of the short-circuit detection module, the reverse input end of the second comparator serves as the second input end of the short-circuit detection module, the output end of the second comparator is connected to the base of the fourth transistor, the emitter of the fourth transistor is grounded, the collector of the fourth transistor is connected to the base of the fifth transistor, the emitter of the fifth transistor serves as the first output end of the short-circuit detection module, and the collector of the fifth transistor serves as the second output end of the short-circuit detection module. In this embodiment, the detection circuit also includes a short-circuit detection module. When the load is short-circuited, the voltage at the inverting input terminal of the second comparator is very small and will be less than the second voltage threshold. At this time, the second comparator will output high impedance, and the fourth transistor and the fifth transistor will be turned on. At this time, the first and third terminals of the switch module have the same voltage, the second MOS tube is disconnected, and the power supply no longer supplies power to the load to avoid irreversible damage to the circuit caused by the load short circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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.

[0017] Figure 1is a block diagram of a load detection circuit in an embodiment provided by the present application;

[0018] Figure 2 is a circuit diagram of a load detection circuit in an embodiment provided by the present application Figure 1 ;

[0019] Figure 3 is a circuit diagram of a load detection circuit in an embodiment provided by the present application Figure 2 . DETAILED DESCRIPTION

[0020] To make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. However, it will be appreciated by those skilled in the art that in the embodiments of the present invention, many technical details are proposed in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present application can be implemented. The division of the following embodiments is for the convenience of description, and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined and referenced with each other without contradiction.

[0021] A traditional power supply is usually provided with two output terminals for connecting to a load or accessing a power grid. These two output terminals are usually exposed outside the power supply but have the ability to supply high current.

[0022] If the two output terminals of the power supply are connected by accident due to wires, insects or other reasons, the power supply will be short-circuited and sparks will occur. In severe cases, the power supply and the circuit where the power supply is located may be damaged, and even a fire may occur.

[0023] In addition, the two output ends of the traditional power supply are not hot-swappable. If the two output ends have high current supply capacity and then the load is connected, if the load is capacitive, the current at the output end of the circuit will surge at the moment the load is connected. In severe cases, sparks may occur. If equipment containing traditional power supplies is used in places where fireworks are strictly prohibited, safety accidents are likely to occur, causing immeasurable losses.

[0024] In response to the above problems, the embodiments of the present application provide the following technical concepts: the load condition is detected by a tiny current. When the load is not connected, the tiny current will raise the output voltage. When the load is short-circuited, the output voltage will be pulled down. In both cases, the output voltage will exceed the preset range. By detecting the output voltage, the present application can determine the current condition of the load and thus select a reasonable time to connect the main power supply.

[0025] One embodiment of the present invention relates to a load detection circuit. Figure 1The circuit includes: a power supply 1, a switch module 2, a comparison module 3 and a constant current module 4.

[0026] The circuit structure is as follows: the positive electrode of the power supply 1 is connected to the first end of the switch module 2, the second end of the switch module 2 is used to connect the first end of the load Rload, the negative electrode of the power supply 1 is grounded GND, and is used to connect the second end of the load Rload, the output end of the constant current module 4 is connected to the second end of the switch module 2, the second end of the switch module 2 is also connected to the first end of the comparison module 3, the second end of the comparison module 3 is used to receive the first voltage threshold, the third end of the comparison module 3 is connected to the negative electrode of the power supply 1, and the fourth end of the comparison module 3 is connected to the third end of the switch module 2.

[0027] The comparison module 3 controls the switch module 2 to be turned on when the voltage at the first end of the comparison module 3 is less than the first voltage threshold.

[0028] In this embodiment, a comparison module is set up so that the comparison module can determine whether the load is currently connected to the circuit by detecting the voltage at the first end of the comparison module and the size of the first voltage threshold, and only when the load is currently connected to the circuit, the switch module is controlled to be turned on so that the load is powered by the power supply, thereby limiting the maximum power supply current when the load is not connected, and effectively improving the safety of the power supply circuit. If the load is connected after the output end of the circuit has a large current supply capability, if the load is capacitive, the current at the output end of the circuit will transiently surge at the moment of connecting the load, and a fire accident may occur in severe cases. In the embodiment of the present application, when it is detected that the load has been connected to the circuit, the power supply circuit between the power supply and the load is softly turned on so that the current at the output end increases slowly, thereby eliminating the spark caused by the current surge, and further improving the safety of the power supply circuit.

[0029] The implementation details of the load detection circuit of this embodiment are specifically described below. The following content is only provided for easy understanding of the implementation details and is not necessary for implementing this solution.

[0030] When the load Rload is not connected to the circuit, the voltage Vout at the first end of the load detection circuit is approximately equal to the sum of the output voltage V1 of the power supply 1 and the voltage drop across the switch module 2. If the voltage drop across the switch module 2 is, for example, 1V, then Vout can be considered to be approximately equal to (V1+1)V. At this time, the voltage at the first end of the comparison module is equal to Vout>V1.

[0031] When the load Rload is connected to the circuit, a part of the current of the constant current module 4 will flow through the load, thereby reducing the current flowing into the comparison module 3. At this time, the voltage Vout of the first end of the load detection circuit will be pulled down to less than V1, thereby causing the voltage of the first end of the comparison module 3 to be equal to Vout. <V1。

[0032] In the embodiment of the present application, a comparison module 3 is set so that the comparison module 3 determines the size of the voltage at the first end of the comparison module 3 and the first voltage threshold (in the above example, the first voltage threshold can be equal to V1), and when the voltage at the first end of the comparison module 3 is less than the first voltage threshold, it is considered that the load is currently connected to the circuit, and a control signal is output to the switch module 2 to control the switch module 2 to be turned on, so that the power supply 1 supplies power to the load; when the voltage at the first end of the comparison module 3 is greater than or equal to the first voltage threshold, it is considered that the load is currently not connected to the circuit, and at this time, the switch module 2 is controlled to be disconnected to disconnect the power supply circuit for the power supply 1 to supply power to the load.

[0033] In some embodiments, please refer to Figure 2 The comparison module 3 includes: a first resistor R1, a second resistor R2, a first comparator U1 and a first MOS tube M1. The first MOS tube M1 is an NMOS tube. In some embodiments, the first MOS tube M1 can also be replaced by a PNP transistor as long as the conditions for the on and off of the two are consistent.

[0034] The circuit structure is as follows: the first end of the first resistor R1 serves as the first end of the comparison module 3, the second end of the first resistor R1 is connected to the first end of the second resistor R2, the second end of the second resistor R2 serves as the third end of the comparison module 3, the second end of the first resistor R1 is connected to the inverting input end of the first comparator U1, the non-inverting input end of the first comparator U1 serves as the second end of the comparison module 3, the output end of the first comparator U1 is connected to the gate of the first MOS tube M1, the source of the first MOS tube M1 is connected to the third end of the comparison module 3, and the drain of the first MOS tube M1 serves as the fourth end of the comparison module 3.

[0035] The first comparator U1 also includes two power supply terminals (not shown in the figure), the positive power supply terminal of the first comparator U1 is connected to one end of the reference voltage source VCC, and the other end of VCC is grounded through a decoupling capacitor C to keep the output of VCC stable, and the negative power supply terminal of the first comparator U1 is grounded.

[0036] In some embodiments, technicians can adjust the voltage input to the reverse input terminal of the first comparator U1 by adjusting the ratio of the resistance values ​​of the first resistor R1 and the second resistor R2. Specifically, the smaller the ratio of the resistance values ​​of the first resistor R1 and the second resistor R2, the greater the voltage at the reverse input terminal of the first comparator U1.

[0037] In some embodiments, please refer to Figure 2, a reference voltage source V2 can be set in the comparison module 3 to input the first voltage threshold into the non-inverting input terminal of the first comparator U1. Specifically, the negative electrode of the reference voltage source V2 is connected to the third terminal of the comparison module 3, and the positive electrode of the reference voltage source V2 is connected to the non-inverting input terminal of the first comparator U1 through a resistor R6. The technician can adjust the first voltage threshold by adjusting the output voltage of the reference voltage source V2 or the resistance value of the resistor R6.

[0038] In this embodiment, when the load is not connected to the circuit, the voltage at the reverse input terminal of the first comparator is greater than the first voltage threshold received by the in-phase input terminal. At this time, the output terminal of the first comparator will output a low level to the gate of the first MOS tube, and the first MOS tube will be disconnected, so that the comparison module can output a high level to the switch module; when the load is connected to the circuit, due to the voltage division effect of the load, the voltage at the reverse input terminal of the first comparator will be less than the first voltage threshold received by the in-phase input terminal. At this time, the output terminal of the first comparator will output a high level to the gate of the first MOS tube, and the first MOS tube will be turned on to lower the gate voltage of the second MOS tube.

[0039] In some embodiments, please refer to Figure 2 The comparison module 3 further includes a second capacitor C2, a first end of the second capacitor C2 is connected to the first end of the first resistor R1, and a second end of the second capacitor C2 is connected to the second end of the first resistor R1.

[0040] In this embodiment, during the process of the output voltage starting to rise, current will flow through the second capacitor. Compared with only setting the first resistor, the current flowing through the total resistance obtained by connecting the second capacitor in parallel with the first resistor will be larger, so that the first comparator can reach the threshold voltage earlier to output a low level, so that the first MOS tube and the second MOS tube are both in the cut-off state, preventing the second MOS tube from jittering due to false triggering, and effectively improving the reliability of the circuit.

[0041] In some embodiments, please refer to Figure 2 The second capacitor C2 can also be connected in series with a resistor R5, and the branch formed by the series connection is connected in parallel at both ends of the first resistor R1.

[0042] In some embodiments, please refer to Figure 2 The comparison module 3 further includes a diode D1 , an anode of the diode D1 is connected to the second end of the second resistor R2 , and a cathode of the diode D1 is connected to the first end of the second resistor R2 .

[0043] In this embodiment, if a load short circuit occurs, the first comparator may be damaged due to the voltage across the second capacitor. The embodiment of the present application can clamp the voltage at the inverting input terminal of the first comparator to no less than -0.7V by adding a diode, thereby protecting the first comparator and improving the safety of the circuit under extreme conditions.

[0044] In some embodiments, please refer to Figure 2 , the comparison module 3 also includes a third resistor R3 and / or a third capacitor C3.

[0045] The circuit structure is as follows: a first end of the third resistor R3 is connected to the non-inverting input terminal of the first comparator U1, a second end of the third resistor R3 is connected to the output terminal of the first comparator U1, and / or a first end of the third capacitor C3 is connected to the non-inverting input terminal of the first comparator U1, a second end of the third capacitor C3 is connected to the output terminal of the first comparator U1, Figure 2 In the figure, the simultaneous provision of the third resistor R3 and the third capacitor C3 is taken as an example.

[0046] In this embodiment, by providing the third resistor and / or the third capacitor to form a feedback loop of the first comparator, the first comparator can work more stably.

[0047] In some embodiments, please refer to Figure 2 The comparison module 3 also includes a resistor R7 and a resistor R8. The first end of the resistor R7 is connected to the third end of the comparison module 3, and the second end of the resistor R7 is connected to the gate of the first MOS tube M1 for stabilizing the gate voltage of the first MOS tube M1. The first end of the resistor R8 is connected to the drain of the first MOS tube M1, and the second end of the resistor R8 serves as the fourth end of the comparison module 3.

[0048] In some embodiments, a specific implementation of the switch module is provided. Figure 2 The switch module 2 includes a second MOS tube M2, which is a PMOS tube. In some embodiments, the second MOS tube M2 can also be replaced by a PNP transistor as long as the on and off conditions of the two are consistent.

[0049] The source of the second MOS tube M2 serves as the first end of the switch module 2 , the drain of the second MOS tube M2 serves as the second end of the switch module 2 , and the gate of the second MOS tube M2 serves as the third end of the switch module 2 .

[0050] In this embodiment, when the load is not connected to the circuit, the comparison module will output high impedance to the switch module, and the second MOS tube will be in a disconnected state; when the load is connected to the circuit, the comparison module will output low impedance to the switch module, and the second MOS tube will be in a conductive state, so that the power supply can power the load.

[0051] In some embodiments, please refer to Figure 2 The switch module 2 further includes a first capacitor C1, a first end of the first capacitor C1 is connected to a first end of the switch module 2, and a second end of the first capacitor C1 is connected to a third end of the switch module 2. In some embodiments, a resistor R9 may be connected in parallel at both ends of the first capacitor C1. The technician may adjust the threshold voltage of the second MOS tube M2 by adjusting the ratio of the resistance value of the resistor R9 to the resistance value of the resistor R8, so that the second MOS tube M2 can work normally.

[0052] In this embodiment, before the second MOS tube is turned on, the first capacitor will be charged first, and the second MOS tube will not be turned on until the voltage across the first capacitor is greater than the turn-on voltage of the second MOS tube. That is, the embodiment of the present application sets a slow start process for the second MOS tube, prolonging the time for the second MOS tube to pass through the linear region to prevent the charging current from being too large, thereby further improving the safety of the power supply circuit.

[0053] In some embodiments, please refer to Figure 2 The constant current module 4 includes a voltage source V3, a first transistor Q1, a second transistor Q2, a third transistor Q3 and a fourth resistor R4. The output voltage of the voltage source V3 needs to be greater than the output voltage of the power supply 1, that is, V3>V1. Specifically, V3>(V1+2)V can be set, where 2V can be considered as the sum of the voltage drops on other components in the constant current module 4, and can be set according to actual conditions. The first transistor Q1, the second transistor Q2 and the third transistor Q3 are all PNP transistors.

[0054] The circuit structure is as follows: the negative electrode of the voltage source V3 is grounded, the positive electrode of the voltage source V3 is connected to the emitter of the first triode Q1, the collector of the first triode Q1 is connected to the first end of the fourth resistor R4, the second end of the fourth resistor R4 is grounded, the base of the first triode Q1 is connected to the base of the second triode Q2, the emitter of the first triode Q1 is connected to the emitter of the second triode Q2, the collector of the second triode Q2 is connected to the emitter of the third triode Q3, the collector of the second triode Q1 is also connected to the base of the second triode Q2, the collector of the third triode Q3 serves as the output end of the constant current module 4, and the base of the third triode Q3 is connected to the first end of the fourth resistor R4.

[0055] In this embodiment, technicians can adjust the current output from the constant current module to the comparison module by adjusting the resistance value of the fourth resistor to meet various application scenarios.

[0056] In some embodiments, please refer to Figure 3The circuit also includes a short-circuit detection module 5, a first input end of the short-circuit detection module 5 is used to receive the second voltage threshold, a second input end of the short-circuit detection module 5 is connected to the inverting input end of the first comparator U1, a first output end of the short-circuit detection module 5 is connected to the first end of the switch module 2, and a second output end of the short-circuit detection module 5 is connected to the third end of the switch module 2.

[0057] The short-circuit detection module 5 specifically includes a second comparator U2, a fourth transistor Q4 and a fifth transistor Q5. The fourth transistor Q4 is an NPN-type transistor, the fifth transistor Q5 is a PNP-type transistor, the same-direction input end of the second comparator U2 serves as the first input end of the short-circuit detection module 5, the reverse input end of the second comparator U2 serves as the second input end of the short-circuit detection module 5, the output end of the second comparator U2 is connected to the base of the fourth transistor Q4, the emitter of the fourth transistor Q4 is grounded, the collector of the fourth transistor Q4 is connected to the base of the fifth transistor Q5, the emitter of the fifth transistor Q5 serves as the first output end of the short-circuit detection module 5, and the collector of the fifth transistor Q5 serves as the second output end of the short-circuit detection module 5.

[0058] Among them, the second comparator U2 also includes two power supply terminals (not shown in the figure), the positive power supply terminal of the second comparator U2 is connected to one end of the reference voltage source VCC, and the other end of VCC is grounded through a decoupling capacitor C to keep the output of VCC stable, and the negative power supply terminal of the second comparator U2 is grounded.

[0059] In some embodiments, please refer to Figure 3 , the reference voltage source V2 can be set in the comparison module 3 to input the second voltage threshold into the non-inverting input terminal of the second comparator U2. Specifically, the positive electrode of the reference voltage source V2 can be connected to the non-inverting input terminal of the second comparator U2 through a resistor R10, and the non-inverting input terminal of the second comparator U2 is also grounded through a resistor R11. The technician can adjust the size of the second voltage threshold by adjusting the output voltage of the reference voltage source V2 or the ratio of the resistance values ​​of the resistor R10 and the resistor R11.

[0060] When the two output ends of a traditional power supply are short-circuited, technicians will use intermittent starting, current limiting or over-temperature protection to protect the circuit. However, when the power supply repeatedly attempts to start, the stress on the components in the power supply circuit is often too large, which can easily cause damage to the components. Therefore, components with higher specifications are required. At the same time, during the repeated attempts to start the power supply, large losses will be generated. The heat generated by these losses will continue to accumulate, which can easily cause fire accidents.

[0061] In this embodiment, the detection circuit also includes a short-circuit detection module. When the load is short-circuited, the voltage at the inverting input terminal of the second comparator is very small and will be less than the second voltage threshold. At this time, the second comparator will output high impedance, and the fourth transistor and the fifth transistor will be turned on. At this time, the first end and the third end of the switch module have the same voltage, the second MOS tube is disconnected, and the power supply no longer supplies power to the load to avoid irreversible damage to the circuit caused by the load short circuit. The power supply does not need to repeatedly try to start, so it will not cause excessive losses, effectively improving the safety of the power supply circuit.

[0062] In some embodiments, please refer to Figure 3 The non-inverting input terminal of the second comparator U2 can be connected to the output terminal of the second comparator U2 through the resistor R12 to form a feedback loop of the second comparator U2, which can make the second comparator work more stably.

[0063] Also, please refer to Figure 3 The output end of the second comparator U2 can also be connected to the base of the fourth transistor Q4 through the resistor R13, and the collector of the fourth transistor Q4 can be connected to the base of the fifth transistor Q5 through the resistor R14. The technician can adjust the resistance values ​​of the resistor R13 and the resistor R14 to make the fourth transistor Q4 and the fifth transistor Q5 work normally.

[0064] The following is an example of data from a notebook adapter. V1 is 19V, V3 is 21V, R4=2KΩ, R1=34.8KΩ, R2=5KΩ, the constant current module 4 outputs a current I1≈10mA, the voltage Vout of the first end of the comparison module 3 is 20V, and V2=2.5V.

[0065] When the load Rload is not connected to the circuit, the voltage at the non-inverting input terminal of the first comparator U1 is V2 minus the voltage across the resistor R6, which is approximately equal to 2.45V. At this time, the voltage at the reverse input terminal of the first comparator U1 is the value obtained by dividing the Vout voltage by the first resistor R1 and the second resistor R2, which is approximately equal to 2.51V. Since 2.51V>2.45V, the first comparator U1 will output a low level to the first MOS tube M1, and M1 and M2 are both disconnected. At this time, the power supply circuit of the power supply 1 is in a disconnected state.

[0066] When the load Rload is connected to the circuit, the current I1 output by the constant current module 4 will flow through the load Rload. If the load Rload is a capacitive load, the current I1 will charge the equivalent capacitor of the load Rload, which will cause the voltage Vout to be pulled down. At this time, the voltage at the inverting input terminal of the first comparator U1 will be less than the first voltage threshold 2.45V, so the first comparator U1 will output a high level to the first MOS tube M1, and both M1 and M2 will be turned on. At this time, the power supply circuit of the power supply 1 is in the on state, and the power supply 1 can supply power to the load Rload.

[0067] It is worth mentioning that all modules involved in this embodiment are logic modules. In practical applications, a logic unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. In addition, in order to highlight the innovative part of the present invention, this embodiment does not introduce units that are not closely related to solving the technical problem proposed by the present invention, but this does not mean that there are no other units in this embodiment.

[0068] Another embodiment of the present invention relates to a circuit board assembly, comprising the load detection circuit of any one of the above embodiments.

[0069] Those skilled in the art will appreciate that the above embodiments are specific embodiments for implementing the present invention, and that in actual applications, various changes may be made in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A load detection circuit, characterized in that: include: Power supply, switch module, comparison module and constant current module; The positive electrode of the power supply is connected to the first end of the switch module, the second end of the switch module is used to connect the first end of the load, the negative electrode of the power supply is grounded, and is used to connect the second end of the load, the output end of the constant current module is connected to the second end of the switch module, the second end of the switch module is also connected to the first end of the comparison module, the second end of the comparison module is used to receive the first voltage threshold, the third end of the comparison module is connected to the negative electrode of the power supply, and the fourth end of the comparison module is connected to the third end of the switch module; The comparison module is used for controlling the switch module to be turned on when the voltage at the first end of the comparison module is less than the first voltage threshold; The comparison module includes: a first resistor, a second resistor, a first comparator and a first MOS tube, wherein the first MOS tube is an NMOS tube; The first end of the first resistor serves as the first end of the comparison module, the second end of the first resistor is connected to the first end of the second resistor, the second end of the second resistor serves as the third end of the comparison module, the second end of the first resistor is connected to the inverting input end of the first comparator, the non-inverting input end of the first comparator serves as the second end of the comparison module, the output end of the first comparator is connected to the gate of the first MOS tube, the source of the first MOS tube is connected to the third end of the comparison module, and the drain of the first MOS tube serves as the fourth end of the comparison module.

2. The load detection circuit according to claim 1, characterized in that: The switch module includes a second MOS tube, and the second MOS tube is a PMOS tube; The source of the second MOS transistor serves as the first end of the switch module, the drain of the second MOS transistor serves as the second end of the switch module, and the gate of the second MOS transistor serves as the third end of the switch module.

3. The load detection circuit according to claim 2, characterized in that: The switch module further includes a first capacitor, a first end of the first capacitor is connected to the first end of the switch module, and a second end of the first capacitor is connected to the third end of the switch module.

4. The load detection circuit according to claim 1, characterized in that: The comparison module further includes a second capacitor, a first end of the second capacitor is connected to the first end of the first resistor, and a second end of the second capacitor is connected to the second end of the first resistor.

5. The load detection circuit according to claim 4, characterized in that: The comparison module further includes a diode, an anode of the diode is connected to the second end of the second resistor, and a cathode of the diode is connected to the first end of the second resistor.

6. The load detection circuit according to claim 1, characterized in that: The comparison module further includes a third resistor and / or a third capacitor; The first end of the third resistor is connected to the non-inverting input terminal of the first comparator, and the second end of the third resistor is connected to the output terminal of the first comparator, and / or the first end of the third capacitor is connected to the non-inverting input terminal of the first comparator, and the second end of the third capacitor is connected to the output terminal of the first comparator.

7. The load detection circuit according to claim 1, characterized in that: The constant current module includes a voltage source, a first triode, a second triode, a third triode and a fourth resistor, the output voltage of the voltage source is greater than the output voltage of the power supply, and the first triode, the second triode and the third triode are all PNP triodes; The negative electrode of the voltage source is grounded, the positive electrode of the voltage source is connected to the emitter of the first triode, the collector of the first triode is connected to the first end of the fourth resistor, the second end of the fourth resistor is grounded, the base of the first triode is connected to the base of the second triode, the emitter of the first triode is connected to the emitter of the second triode, the collector of the second triode is connected to the emitter of the third triode, the collector of the second triode is also connected to the base of the second triode, the collector of the third triode serves as the output end of the constant current module, and the base of the third triode is connected to the first end of the fourth resistor.

8. The load detection circuit according to claim 2, characterized in that: The circuit further comprises a short circuit detection module, wherein a first input terminal of the short circuit detection module is used to receive a second voltage threshold, a second input terminal of the short circuit detection module is connected to an inverting input terminal of the first comparator, a first output terminal of the short circuit detection module is connected to a first terminal of the switch module, and a second output terminal of the short circuit detection module is connected to a third terminal of the switch module; The short-circuit detection module includes a second comparator, a fourth transistor and a fifth transistor, the fourth transistor is an NPN-type transistor, the fifth transistor is a PNP-type transistor, the same-direction input end of the second comparator serves as the first input end of the short-circuit detection module, the reverse input end of the second comparator serves as the second input end of the short-circuit detection module, the output end of the second comparator is connected to the base of the fourth transistor, the emitter of the fourth transistor is grounded, the collector of the fourth transistor is connected to the base of the fifth transistor, the emitter of the fifth transistor serves as the first output end of the short-circuit detection module, and the collector of the fifth transistor serves as the second output end of the short-circuit detection module.

9. A circuit board assembly, characterized in that: A detection circuit comprising a load as claimed in any one of claims 1 to 8.

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