A circuit structure with a load open-circuit detection function

Abstract

The present application discloses a circuit structure with a load open - circuit detection function, which relates to the technical field of battery charging. The circuit structure includes a battery charging circuit and a load open - circuit detection circuit; the battery charging circuit is used to provide a charging current and a charging voltage for the battery load, and input the charging voltage as its output voltage to the load open - circuit detection circuit; in the load open - circuit detection circuit, the power supply voltage is grounded through a third detection resistor, a fourth detection resistor, a first detection resistor, a fourth detection switch tube and the second branch of the current mirror in sequence; the output voltage is grounded through a second detection resistor, a fifth detection switch tube and the third branch of the current mirror, and the control end of the fifth detection switch tube is connected to the control end of the fourth detection switch tube. The load open - circuit detection circuit of this solution detects the output voltage and the power supply voltage, and determines whether there is an open - circuit fault in the battery load through the voltage difference between the two, improving the safety and reliability of the battery load and the charging circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of battery charging, and more particularly to a circuit structure with a load open circuit detection function. Background Art

[0002] In the battery charging circuit of the prior art, in order to ensure the safety and reliability of the charging circuit, it is usually necessary to monitor the state of the battery load. In practical applications, such as Figure 1 the circuit structure shown, when an open circuit fault occurs in the battery load, if it cannot be detected and processed in time, it will not only affect the charging efficiency of the battery circuit, but also cause serious consequences such as damage to the battery charging circuit, and even lead to dangerous situations such as battery heating, swelling, leakage, and explosion.

[0003] Therefore, how to realize the real-time monitoring and fault warning of the load state of the battery charging circuit is a technical problem that needs to be solved urgently at present. Summary of the Invention

[0004] The purpose of the present invention is to provide a circuit structure with a load open circuit detection function, which uses a load open circuit detection circuit to detect the output voltage and power supply voltage of the battery charging circuit, realizes the monitoring of the battery load state, and improves the safety of the circuit.

[0005] To achieve the above object, the present invention discloses the following technical solutions:

[0006] In the first aspect of the present invention, there is provided a circuit structure with a load open circuit detection function, which includes a battery charging circuit and a load open circuit detection circuit; the battery charging circuit is used to provide a charging current and a charging voltage for the battery load, and input the charging voltage as its output voltage vout to the load open circuit detection circuit;

[0007] In the load open circuit detection circuit, the power supply voltage vdd is grounded successively through the first detection current source B1 and the first branch of the current mirror; the power supply voltage vdd also passes through the third detection resistor rb, the fourth detection resistor rc, the first detection resistor ra1, the fourth detection switch tube M4 and the second branch of the current mirror to be grounded, and the control end of the fourth detection switch tube M4 is connected to its current output end, and both ends of the fourth detection resistor rc are connected in parallel with the ninth detection switch tube M9; the power supply voltage vdd also passes through the second detection current source B2 and the eighth detection switch tube M8 to be grounded, and the current input end of the eighth detection switch tube M8 is connected to the control end of the ninth detection switch tube M9 and outputs a detection voltage;

[0008] The output voltage vout is grounded through a second detection resistor ra2, a fifth detection switch tube M5, and a third branch of a current mirror in sequence, and the control terminal of the fifth detection switch tube M5 is connected to the control terminal of the fourth detection switch tube M4; the current output terminal of the fifth detection switch tube M5 is also grounded through a sixth detection switch tube M6 and a seventh detection switch tube M7 in sequence, and the control terminal of the sixth detection switch tube M6 is connected to its current input terminal and connected to the control terminal of an eighth detection switch tube M8, and the control terminal of the seventh detection switch tube M7 is connected to its current input terminal.

[0009] In a possible implementation manner, the first branch of the current mirror includes a first detection switch tube M1, the second branch includes a second detection switch tube M2, the third branch includes a third detection switch tube M3, and the control terminal of the first detection switch tube M1, the control terminal of the second detection switch tube M2, and the control terminal of the third detection switch tube M3 are connected and connected to the current input terminal of the first detection switch tube M1.

[0010] In a possible implementation manner, the first detection switch tube M1, the second detection switch tube M2, and the third detection switch tube M3 have the same parameters; the fourth detection switch tube M4 and the fifth detection switch tube M5 have the same parameters; the first detection resistor ra1 and the second detection resistor ra2 have the same resistance value.

[0011] In a possible implementation manner, the first detection switch tube M1, the second detection switch tube M2, the third detection switch tube M3, the sixth detection switch tube M6, the seventh detection switch tube M7, the eighth detection switch tube M8, and the ninth detection switch tube M9 are all NMOS transistors or NPN triodes;

[0012] The fourth detection switch tube M4 and the fifth detection switch tube M5 are both PMOS transistors or PNP triodes.

[0013] In the above circuit structure, in a possible implementation manner, the load open - circuit detection circuit detects the output voltage vout and the power supply voltage vdd, and when the voltage difference between the output voltage vout and the power supply voltage vdd is less than a preset threshold, it is determined that an open - circuit fault occurs in the battery load.

[0014] In a possible implementation manner, in the battery charging circuit, the power supply voltage vdd is grounded through a second resistor r2, a first power switch tube Ma, and a first resistor r1 in sequence, and the control terminal of the first power switch tube Ma is connected to the output terminal of a first operational amplifier A1; the positive input terminal of the first operational amplifier A1 is connected to a reference voltage vref, and the negative input terminal is connected to the current output terminal of the first power switch tube Ma;

[0015] The power supply voltage Vdd is also grounded through a third resistor R3, a second power switch transistor Mp and a battery load in sequence, and the control terminal of the second power switch transistor Mp is connected to the output terminal of a second operational amplifier A2; the non-inverting input terminal of the second operational amplifier A2 is connected to the current input terminal of the first power switch transistor Ma, and the inverting input terminal is connected to the current input terminal of the second power switch transistor Mp.

[0016] In a possible implementation manner, the rated value of the output voltage Vout is set to be less than or equal to , where i1 is the first current i1 generated by the first detection current source B1 after the load open detection circuit is powered on. The preset threshold is set to .

[0017] In the above circuit structure, in a possible implementation manner, when the battery charging circuit is working normally, the load open detection circuit outputs a high-level detection voltage Vb; when an open circuit fault occurs in the battery load, the load open detection circuit outputs a low-level detection voltage Vb.

[0018] In a possible implementation manner, the load open detection circuit is connected to a protection execution circuit. When an open circuit fault occurs in the battery load and the voltage difference between the output voltage Vout and the power supply voltage Vdd increases to be less than a preset threshold, the load open detection circuit triggers the protection execution circuit to protect the battery charging circuit.

[0019] In a possible implementation manner, the circuit structure further includes a locking circuit. The load open detection circuit is connected to the protection execution circuit through the locking circuit. When an open circuit fault occurs in the battery load, the locking circuit triggers the protection execution circuit to protect the battery charging circuit.

[0020] In a possible implementation manner, the locking circuit includes a D flip-flop. When an open circuit fault occurs in the battery load, the load open detection circuit outputs a low-level detection voltage Vb. The D flip-flop latches the low-level detection voltage Vb and generates a low-level locking voltage Vc to be input into the protection execution circuit.

[0021] In a second aspect of the present invention, a battery charging device is provided. The battery charging device includes the circuit structure with a load open detection function as described in the first aspect.

[0022] The effects provided in the summary of the invention are only the effects of the embodiments, rather than all the effects of the invention. One of the above technical solutions has the following advantages or beneficial effects:

[0023] A circuit structure with a load open - circuit detection function provided by this application includes a battery charging circuit and a load open - circuit detection circuit. The battery charging circuit can provide a stable and reliable charging current and charging voltage for the battery load. The load open - circuit detection circuit is connected to the battery charging circuit, detects the output voltage and power supply voltage of the battery charging circuit, and can determine whether the battery load has an open - circuit fault through the voltage difference between the output voltage and the power supply voltage, realizing real - time monitoring of the battery load status and fault warning, and improving the safety and reliability of the battery load and the charging circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings herein are incorporated into and constitute a part of the specification, showing embodiments consistent with this application, and are used together with the specification to explain the principles of this application.

[0025] Figure 1 is a schematic diagram of a battery charging circuit in the prior art;

[0026] Figure 2 is a schematic diagram of the circuit structure with a load open - circuit detection function according to an embodiment of this application;

[0027] Figure 3 is a schematic diagram of the circuit principle of the circuit structure with a load open - circuit detection function according to an embodiment of this application;

[0028] Figure 4 is a schematic diagram of the circuit principle of the circuit structure with a load open - circuit detection function according to another embodiment of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to 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 used to limit the present invention.

[0030] It should be noted that the references to "one embodiment", "embodiment", "exemplary embodiment", etc. in this specification mean that the described embodiment may include specific features, structures or characteristics, but not every embodiment must include these specific features, structures or characteristics. In addition, such expressions do not refer to the same embodiment. Further, when combining embodiments to describe specific features, structures or characteristics, whether or not there is an explicit description, it has been shown that combining such features, structures or characteristics into other embodiments is within the knowledge scope of those skilled in the art.

[0031] Figure 1 is a schematic diagram of a battery charging circuit in the prior art. Refer to Figure 1, the battery charging circuit includes a first operational amplifier A1, a second operational amplifier A2, a first resistor r1, a second resistor r2, a third resistor r3, a first power switch Ma, a second power switch Mp, and a battery load. In this battery charging circuit, the power supply voltage vdd is grounded through the second resistor r2, the first power switch Ma, and the first resistor r1 in sequence, and the control terminal of the first power switch Ma is connected to the output terminal of the first operational amplifier A1. The non-inverting input terminal of the first operational amplifier A1 is connected to the reference voltage vref, and the inverting input terminal is connected to the current output terminal of the first power switch Ma. The power supply voltage vdd is also grounded through the third resistor r3, the second power switch Mp, and the battery load in sequence, and the control terminal of the second power switch Mp is connected to the output terminal of the second operational amplifier A2. The non-inverting input terminal of the second operational amplifier A2 is connected to the current input terminal of the first power switch Ma, and the inverting input terminal is connected to the current input terminal of the second power switch Mp.

[0032] It can be seen from Figure 1 that in this circuit, the first operational amplifier A1 can adjust the voltage vas at the current output terminal of the first power switch Ma to be equal to the reference voltage vref. At this time, the current on the first resistor r1 can be obtained, and thus the voltage at the current input terminal of the first power switch Ma can be obtained. Also, since the second operational amplifier A2 can adjust the voltage vps at the current input terminal of the second power switch Mp to be equal to the voltage vad, the current flowing through the third resistor r3, that is, the output current , can be obtained.

[0033] When Figure 1 a load open circuit fault occurs in the battery charging circuit in , the output current iout will become very small. That is, at this time, the current flowing through the third resistor r3 is also very small. Therefore, it can be considered that the voltage vps at the current input terminal of the second power switch Mp ≈ the power supply voltage vdd. And from the above analysis, under the action of the first operational amplifier A1, the voltage vad is a fixed value

[0034] . Thus, it can be obtained that the voltage vps is greater than the voltage vad. Therefore, the control voltage vg output by the second operational amplifier A2 is relatively low. After this control voltage vg is input to the control terminal of the second power switch Mp, the voltage difference between the control terminal and its current input terminal of the second power switch Mp is relatively large, while the output current iout flowing through the second power switch Mp is relatively small. Therefore, at this time, it can be obtained that the voltage difference between the current input terminal and the current output terminal of the second power switch Mp is relatively small. That is, at this time, the output voltage vout ≈ the voltage vps ≈ the power supply voltage vdd.

[0034] It can be seen from the above analysis that when Figure 1When a load open - circuit fault occurs in the circuit, the output voltage vout≈ the power - supply voltage vdd. Therefore, it is possible to further detect the output voltage vout and the power - supply voltage vdd, and when the voltage difference between the output voltage vout and the power - supply voltage vdd is small, it can be determined that the battery load has an open - circuit fault.

[0035] Based on Figure 1 the above characteristics of the battery charging circuit in Figure 2 As shown in Figure 1 In one embodiment, the circuit structure includes a battery charging circuit 110 and a load open - circuit detection circuit 120. Among them, the battery charging circuit 110 is the Figure 1 circuit shown in

[0036] Figure 3 to provide a stable and reliable charging current and charging voltage for the battery load. The load open - circuit detection circuit 120 is connected to the battery charging circuit 110, and can realize real - time monitoring of the battery load state by detecting the output voltage vout and the power - supply voltage vdd of the battery charging circuit 110. When the voltage difference between the output voltage vout and the power - supply voltage vdd is less than a preset threshold, it can be determined that the battery load has an open - circuit fault, so that protective measures can be taken in time to improve the safety of the circuit.

[0036] Figure 3 is the circuit schematic diagram of the circuit with a load open - circuit detection function according to an embodiment of the present application. As shown in Figure 3 In the load open - circuit detection circuit 120 of this embodiment, the power - supply voltage vdd is grounded through the first detection current source B1 and the first branch of the current mirror in sequence. The power - supply voltage vdd also passes through the third detection resistor rb, the fourth detection resistor rc, the first detection resistor ra1, the fourth detection switch tube M4 and the second branch of the current mirror to be grounded, and the control end of the fourth detection switch tube M4 is connected to its current output end, and the ninth detection switch tube M9 is connected in parallel at both ends of the fourth detection resistor rc. The power - supply voltage vdd also passes through the second detection current source B2 and the eighth detection switch tube M8 to be grounded, and the current input end of the eighth detection switch tube M8 is connected to the control end of the ninth detection switch tube M9, and the detection voltage vb is output.

[0037] Continue to refer to Figure 3, in the load open - circuit detection circuit 120, the output voltage vout of the battery charging circuit 110 is grounded successively through the second detection resistor ra2, the fifth detection switch tube M5, and the third branch of the current mirror, and the control terminal of the fifth detection switch tube M5 is connected to the control terminal of the fourth detection switch tube M4. The current output terminal of the fifth detection switch tube M5 is also grounded successively through the sixth detection switch tube M6 and the seventh detection switch tube M7, and the control terminal of the sixth detection switch tube M6 is connected to its current input terminal and connected to the control terminal of the eighth detection switch tube M8, and the control terminal of the seventh detection switch tube M7 is connected to its current input terminal.

[0038] According to the circuit structure of this embodiment, after the circuit is powered on, the output voltage vout starts to increase from 0. When the battery charging circuit 110 is in a normal working state, the output voltage vout is a rated value. At this time, the detection voltage vb output by the load open - circuit detection circuit 120 is in a high - level state. When an open - circuit fault occurs in the battery load, the output voltage vout starts to increase from the rated value. When the voltage difference between the output voltage vout and the power supply voltage vdd is less than a preset threshold, the load open - circuit detection circuit 120 outputs a low - level detection voltage vb. Therefore, by detecting the high - and low - level states of the detection voltage vb, it can be determined whether an open - circuit fault occurs in the battery load, thereby realizing real - time monitoring and fault warning of the battery load state and improving the safety and reliability of the circuit.

[0039] In some embodiments, the first branch of the current mirror includes a first detection switch tube M1, the second branch includes a second detection switch tube M2, the third branch includes a third detection switch tube M3, and the control terminals of the first detection switch tube M1, the second detection switch tube M2, and the third detection switch tube M3 are connected and connected to the current input terminal of the first detection switch tube M1. In addition, in order to simplify the circuit design and improve the system performance, in some embodiments, the parameters of the first detection switch tube M1, the second detection switch tube M2, and the third detection switch tube M3 are the same. The parameters of the fourth detection switch tube M4 and the fifth detection switch tube M5 are the same. The resistance values of the first detection resistor ra1 and the second detection resistor ra2 are the same.

[0040] In some embodiments, the first power switch tube Ma, the first detection switch tube M1, the second detection switch tube M2, the third detection switch tube M3, the sixth detection switch tube M6, the seventh detection switch tube M7, the eighth detection switch tube M8, and the ninth detection switch tube M9 are all NMOS transistors or NPN triodes. The second power switch tube Mp, the fourth detection switch tube M4, and the fifth detection switch tube M5 are all PMOS transistors or PNP triodes.

[0041] In addition, in some embodiments, the rated value of the output voltage vout is set to be less than or equal to , where i1 is the first current i1 generated by the first detection current source B1 after the load open detection circuit 120 is powered on. Corresponding to the rated value of the output voltage vout, the preset threshold is set to .

[0042] Next, based on Figure 3 the circuit structure of the embodiment, its working principle and working process will be described in detail.

[0043] After the circuit starts to be powered on, the first detection current source B1 raises the control terminal voltages of the first detection switch transistor M1, the second detection switch transistor M2, and the third detection switch transistor M3, and the first detection switch transistor M1, the second detection switch transistor M2, and the third detection switch transistor M3 are turned on. After that, the control terminal voltage of the fourth detection switch transistor M4 is pulled down through the second detection switch transistor M2, and the fourth detection switch transistor M4 is turned on. At this time, according to Figure 3 the circuit structure, the first detection switch transistor M1, the second detection switch transistor M2, and the third detection switch transistor M3 form a 1:1:1 current mirror structure, and the first current i1 generated by the first detection current source B1 is equal to the second current i2 flowing through the series structure composed of the fourth detection switch transistor M4 and the second detection switch transistor M2, that is, i1 = i2.

[0044] At the same time, when the circuit is just powered on, the output voltage vout of the battery charging circuit 110 is 0. Therefore, the fifth detection switch transistor M5 is in the off state, and the fifth current i5 flowing through the fifth detection switch transistor M5 is also 0. At this time, the control terminal voltages va of the sixth detection switch transistor M6 and the eighth detection switch transistor M8 are pulled down through the third detection switch transistor M3, and the sixth detection switch transistor M6 and the eighth detection switch transistor M8 are in the off state. The detection voltage vb output by the load open detection circuit 120 is pulled up to the power supply voltage vdd by the second detection current source B2. After the pulled-up detection voltage vb is input to the control terminal of the ninth detection switch transistor M9, the ninth detection switch transistor M9 is turned on. At this time, the fourth detection resistor rc is short-circuited by the ninth detection switch transistor M9.

[0045] After that, during the process of power-on adjustment of the circuit, the output voltage vout continuously increases. In this embodiment, the rated value of the output voltage vout is set to be less than or equal to , where i1 is the first current i1 generated by the first detection current source B1 after the load open detection circuit 120 is powered on, and the values of the power supply voltage vdd, the first current i1, the third detection resistor rb, and the fourth detection resistor rc are all fixed values set in advance. After the output voltage vout rises to the rated value, the battery charging circuit 110 is in a stable normal working state. At this time, since the output voltage vout is much greater than 0, and the control terminal voltage of the fifth detection switch M5 is pulled low through the second detection switch M2, the fifth detection switch M5 is turned on, and a fifth current i5 flows through the fifth detection switch M5, and a third current i3 flows through the third detection switch M3.

[0046] When the current input terminal voltage vx of the fourth detection switch M4 is equal to the current input terminal voltage vy of the fifth detection switch M5, that is, vx = vy, the voltage difference between the current input terminal and the control terminal of the fourth detection switch M4 is equal to the voltage difference between the current input terminal and the control terminal of the fifth detection switch M5. Therefore, at this time, the second current i2 flowing through the fourth detection switch M4 is equal to the fifth current i5 flowing through the fifth detection switch M5, that is, i2 = i5. Also, since the first detection switch M1, the second detection switch M2, and the third detection switch M3 form a 1:1:1 current mirror structure, the second current i2 flowing through the second detection switch M2 is equal to the third current i3 flowing through the third detection switch M3, that is, i2 = i3. At this time, the third current i3 flowing through the third detection switch M3 is equal to the fifth current i5 flowing through the fifth detection switch M5, that is, i3 = i5. Therefore, at this time, the control terminal voltage va of the sixth detection switch M6 and the eighth detection switch M8 is at a low level, the sixth detection switch M6 and the eighth detection switch M8 are in an off state, and the detection voltage vb output by the load open detection circuit 120 is in a high level state.

[0047] When the current input terminal voltage vx of the fourth detection switch M4 is greater than the current input terminal voltage vy of the fifth detection switch M5, that is, vx > vy, the voltage difference between the current input terminal and the control terminal of the fourth detection switch M4 is greater than the voltage difference between the current input terminal and the control terminal of the fifth detection switch M5. Therefore, at this time, the second current i2 flowing through the fourth detection switch M4 is greater than the fifth current i5 flowing through the fifth detection switch M5, that is, i2 > i5. Also, since the first detection switch M1, the second detection switch M2, and the third detection switch M3 form a 1:1:1 current mirror structure, the second current i2 flowing through the second detection switch M2 is equal to the third current i3 flowing through the third detection switch M3, that is, i2 = i3. At this time, the third current i3 flowing through the third detection switch M3 should be greater than the fifth current i5 flowing through the fifth detection switch M5. However, Figure 3According to the circuit structure, the current input terminal of the third detection switch transistor M3 is connected to the control terminals of the sixth detection switch transistor M6 and the eighth detection switch transistor M8, and the control terminals of the sixth detection switch transistor M6 and the eighth detection switch transistor M8 (such as the gates of NMOS transistors or the bases of NPN transistors) do not allow current to flow out in the direction of the current input terminal. Therefore, at this time, the third current i3 flowing through the third detection switch transistor M3 is less than the second current i2 flowing through the second detection switch transistor M2, that is, the third current i3 flowing through the third detection switch transistor M3 is equal to the fifth current i5 flowing through the fifth detection switch transistor M5. However, the current pulling-down ability of the third detection switch transistor M3 is greater than the current pulling-up ability of the fifth detection switch transistor M5. Therefore, the control terminal voltage va of the sixth detection switch transistor M6 and the eighth detection switch transistor M8 is in a low-level state, the sixth detection switch transistor M6 and the eighth detection switch transistor M8 are in an off state, and the detection voltage vb output by the load open-circuit detection circuit 120 is in a high-level state.

[0048] When the voltage vx at the current input terminal of the fourth detection switch transistor M4 is less than the voltage vy at the current input terminal of the fifth detection switch transistor M5, that is, vx < vy, the voltage difference between the current input terminal and the control terminal of the fourth detection switch transistor M4 is less than the voltage difference between the current input terminal and the control terminal of the fifth detection switch transistor M5. Therefore, at this time, the second current i2 flowing through the fourth detection switch transistor M4 is less than the fifth current i5 flowing through the fifth detection switch transistor M5, that is, i2 < i5. Also, since the first detection switch transistor M1, the second detection switch transistor M2, and the third detection switch transistor M3 form a 1:1:1 current mirror structure, the second current i2 flowing through the second detection switch transistor M2 is equal to the third current i3 flowing through the third detection switch transistor M3, that is, i2 = i3. At this time, the third current i3 flowing through the third detection switch transistor M3 is less than the fifth current i5 flowing through the fifth detection switch transistor M5. Therefore, at this time, a fourth current i4 flows from the fifth detection switch transistor M5 to the sixth detection switch transistor M6 in the circuit, the control terminal voltage va of the sixth detection switch transistor M6 and the eighth detection switch transistor M8 is pulled up, and the sixth detection switch transistor M6 and the eighth detection switch transistor M8 are turned on. The control terminal voltage of the seventh detection switch transistor M7 is pulled up through the sixth detection switch transistor M6, and the seventh detection switch transistor M7 is turned on. At this time, the fourth current i4 flows into the series branch composed of the sixth detection switch transistor M6 and the seventh detection switch transistor M7. At the same time, the series branch composed of the sixth detection switch transistor M6 and the seventh detection switch transistor M7 can make the control terminal voltage of the eighth detection switch transistor M8 equal to twice the voltage difference between the current input terminal and the control terminal during normal operation of the switch transistor, so as to ensure that when the eighth detection switch transistor M8 can be turned on, it also has a large current pulling-down ability. At this time, the detection voltage vb output by the load open-circuit detection circuit 120 is pulled down to a low-level state.

[0049] As can be seen from the above analysis, inFigure 3 In the circuit structure of the embodiment, after the circuit is powered on, the output voltage vout starts to increase from 0, the detection voltage vb output by the load open circuit detection circuit 120 is at a high level, the ninth detection switch tube M9 is in a conducting state, and the voltage at the current input end of the fourth detection switch tube M4 , and the voltage at the current input end of the fifth detection switch tube M5 .

[0050] When the battery charging circuit 110 is in a normal working state, the maximum value of the output voltage vout is the rated value, and the rated value of the output voltage vout is less than or equal to , so it is less than . From the above analysis, when the voltage vx = vy, the current i1 = i5. When the voltage vx > vy, the current i1 > i5. When the voltage vx < vy, the current i1 < i5. At the same time, since the resistance value of the first detection resistor ra1 is equal to the resistance value of the second detection resistor ra2, it can be obtained that if the voltage vx = vy, since the rated value of the output voltage vout is less than , therefore, the first current i1 must be greater than the fifth current i5, which contradicts that the first current i1 is equal to the fifth current i5. If the voltage vx < vy, since the rated value of the output voltage vout is less than , therefore, the first current i1 must be greater than the fifth current i5, which contradicts that the first current i1 is less than the fifth current i5. If the voltage vx > vy, since the rated value of the output voltage vout is less than , therefore, the first current i1 can be greater than, less than or equal to the fifth current i5, which does not contradict that the first current i1 is greater than the fifth current i5. It can be seen from this that when the battery charging circuit 110 is working normally, the rated value of the output voltage vout is less than , and the voltage vx > vy. At this time, the detection voltage vb output by the load open circuit detection circuit 120 is in a high level state, and the ninth detection switch tube M9 is always in a conducting state.

[0051] After an open circuit fault occurs in the battery load, the output voltage vout starts to increase from the rated value, and the voltage vy at the current input end of the fifth detection switch tube M5 also starts to increase. When the voltage vy at the current input end of the fifth detection switch tube M5 increases to be equal to the voltage vx at the current input end of the fourth detection switch tube M4, the first current i1 is equal to the fifth current i5, that is, i1 = i5. The detection voltage vb output by the load open circuit detection circuit 120 is in a critical state of level switching. At this time, the output voltage vout increases to be equal to , that is, the voltage difference between the output voltage vout and the power supply voltage vdd at this time is equal to the preset threshold .

[0052] When the output voltage vout continues to increase, the voltage difference between the output voltage vout and the power supply voltage vdd is less than the preset threshold at this time , the voltage vx at the current input terminal of the fourth detection switch tube M4 is less than the voltage vy at the current input terminal of the fifth detection switch tube M5, the first current i1 is less than the fifth current i5, that is, i1 < i5, and the detection voltage vb output by the load open detection circuit 120 switches to a low level state. At this time, it is determined that an open circuit fault has occurred in the battery load. At the same time, the ninth detection switch tube M9 is turned off, and the fourth detection resistor rc is connected to the load open detection circuit 120. At this time, the voltage vx at the current input terminal of the fourth detection switch tube M4 decreases to , so as to ensure that the voltage vx at the current input terminal of the fourth detection switch tube M4 is less than the voltage vy at the current input terminal of the fifth detection switch tube M5, and avoid the load open detection circuit 120 from oscillating near the voltage vx at the current input terminal of the fourth detection switch tube M4 being equal to the voltage vy at the current input terminal of the fifth detection switch tube M5, improving the stability of the load open detection circuit 120

[0053] After detecting abnormal conditions such as an open circuit in the battery load, in order to prevent the circuit from being damaged due to abnormal conditions, such as Figure 3 As shown, in this embodiment, the load open detection circuit 120 is also connected to the protection execution circuit 140. When a fault occurs in the battery load, the load open detection circuit 120 triggers the protection execution circuit 140 to protect the battery charging circuit 110, thereby ensuring the safety of the battery and the entire circuit system. The protection execution circuit 140 in this embodiment can adopt the commonly used circuit structures in the prior art, such as a comparator protection circuit, a threshold protection circuit, etc., which will not be elaborated here

[0054] It can be seen from the above analysis that Figure 3 For the circuit structure of the embodiment, on the one hand, when the battery charging circuit 110 is working normally, the load open detection circuit 120 outputs a high-level detection voltage vb. When an open circuit fault occurs in the battery load and the voltage difference between the output voltage and the power supply voltage increases to be less than the preset threshold, the load open detection circuit 120 outputs a low-level detection voltage vb. Inputting this detection voltage vb into the protection execution circuit 140 can trigger the protection execution circuit 140 to protect the battery charging circuit 110 in case of a battery open circuit fault, improving the safety and reliability of the battery load and the charging circuit. On the other hand, the load open detection circuit 120 in this embodiment can avoid oscillating near the voltage vx at the current input terminal of the fourth detection switch tube M4 being equal to the voltage vy at the current input terminal of the fifth detection switch tube M5, improving the stability of the circuit structure

[0055] Although Figure 3The circuit structure provided by the embodiment can effectively protect the battery charging circuit 110 in case of an open-circuit fault of the battery load. However, the inventor found that there is still an actual situation where when the load just has an open-circuit fault and the protection execution circuit 140 may not have had time to take protection actions, the open-circuit fault of the load has recovered by itself. At this time, after the load has an open-circuit fault, the voltage at the current input terminal of the fourth detection switch tube M4 , the voltage at the current input terminal of the fifth detection switch tube M5 , and when the voltage vx < vy, the first current i1 is less than the fifth current i5, that is, i1 < i5. After that, during the process of the load fault recovery, the output voltage vout gradually decreases, and both the voltage vy and the fifth current i5 start to decrease. When the output voltage vout decreases to be equal to , the voltage vy decreases to be equal to the voltage vx, and the fifth current i5 decreases to be equal to the first current i1. At this time, the fourth current i4 is equal to 0, and the control terminal voltage va of the sixth detection switch tube M6 and the eighth detection switch tube M8 switches to a low level. Therefore, the detection voltage vb output by the load open-circuit detection circuit 120 switches to a high level state, the ninth detection switch tube M9 conducts, and the fourth detection resistor rc is short-circuited again. At this time, the voltage vx at the current input terminal of the fourth detection switch tube M4 increases to , so as to ensure that the voltage vx at the current input terminal of the fourth detection switch tube M4 is greater than the voltage vy at the current input terminal of the fifth detection switch tube M5, avoiding the oscillation of the load open-circuit detection circuit 120 near the situation where the voltage vx at the current input terminal of the fourth detection switch tube M4 is equal to the voltage vy at the current input terminal of the fifth detection switch tube M5, and improving the stability of the load open-circuit detection circuit 120. At this time, the output voltage vout of the battery charging circuit 110 starts to work normally according to the rated value (when the rated value is equal to ), or the output voltage vout continues to decrease to the rated value for operation (when the rated value is less than ).

[0056] Therefore, in order to avoid the situation in actual application where the protection execution circuit 140 has not had time to take protection actions and the open-circuit fault of the load has recovered by itself, further increasing the possibility of subsequent load open-circuit faults, the present application also provides a circuit structure with a load open-circuit detection function as shown in Figure 4 . Compared with the circuit structure of the Figure 3 embodiment, the circuit structure in the Figure 4 embodiment further includes a locking circuit 130. The load open-circuit detection circuit 120 is connected to the protection execution circuit 140 through the locking circuit 130. When an open-circuit fault occurs in the battery load, the locking circuit 130 triggers the protection execution circuit 140 to protect the battery charging circuit 110.

[0057] In some embodiments, the locking circuit 130 includes a D flip-flop. When an open-circuit fault occurs in the battery load, the load open-circuit detection circuit 120 outputs a detection voltage vb of low level. The D flip-flop latches the detection voltage vb of low level and outputs a locking voltage vc of low level.

[0058] As Figure 4 shown, when the battery charging circuit 110 is operating normally, the detection voltage vb output by the load open-circuit detection circuit 120 is of high level. At this time, the locking voltage vc output by the locking circuit 130 is also of high level. After an open-circuit fault occurs in the load, the detection voltage vb output by the load open-circuit detection circuit 120 switches to low level. At this time, the locking voltage vc output by the locking circuit 130 also switches to low level. After that, even if the open-circuit fault of the load is self-recovered and the detection voltage vb output by the load open-circuit detection circuit 120 switches back to high level, the locking voltage vc output by the locking circuit 130 still remains at low level, so that after an open-circuit fault occurs in the load, the locking voltage vc of low level is input into the protection execution circuit 140 to ensure that the protection execution circuit 140 can protect the battery charging circuit 110.

[0059] It can be seen from the above analysis that Figure 4 in the circuit structure of the embodiment, a locking circuit 130 is provided. The load open-circuit detection circuit 120 is connected to the protection execution circuit 140 through the locking circuit 130, so that after an open-circuit fault occurs in the circuit, regardless of whether the open-circuit fault of the load is self-recovered or not, the locking circuit 130 outputs a corresponding locking signal to the protection execution circuit 140 to ensure that the protection execution circuit 140 can protect the battery charging circuit 110, further improving the safety and reliability of the battery and the charging circuit.

[0060] It should be noted that Figure 3 the embodiments Figure 4 The circuit structure with load open-circuit detection function shown in the embodiments is only a preferred circuit structure for realizing the purpose of the present invention. In some other embodiments, other circuit structures capable of realizing the same function can also be selected for each circuit module or device, and the present application is not limited thereto.

[0061] In addition, the embodiments of the present application further provide a battery charging device, which includes the circuit structure with load open-circuit detection function in the above embodiments and is used to provide safe and reliable electric energy for the load. For the circuit structure and working process not described in detail in the battery charging device in this embodiment, reference can be made to the relevant parts in the above embodiments of the circuit structure with load open-circuit detection function, and details are not described herein again.

[0062] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A circuit structure with a load open circuit detection function, characterized in that: It includes a battery charging circuit and a load open circuit detection circuit; the battery charging circuit is used to provide a charging current and a charging voltage for the battery load, and inputs the charging voltage as its output voltage vout to the load open circuit detection circuit; In the load open circuit detection circuit, the power supply voltage vdd is grounded through the first detection current source B1 and the first branch of the current mirror in sequence; the power supply voltage vdd is also grounded through the third detection resistor rb, the fourth detection resistor rc, the first detection resistor ra1, the fourth detection switch tube M4 and the second branch of the current mirror in sequence, and the control end of the fourth detection switch tube M4 is connected to its current output end, and the two ends of the fourth detection resistor rc are connected in parallel to the ninth detection switch tube M9; the power supply voltage vdd is also grounded through the second detection current source B2 and the eighth detection switch tube M8 in sequence, and the current input end of the eighth detection switch tube M8 is connected to the control end of the ninth detection switch tube M9, and outputs the detection voltage; The output voltage vout is grounded through the second detection resistor ra2, the fifth detection switch tube M5 and the third branch of the current mirror in sequence, and the control end of the fifth detection switch tube M5 is connected to the control end of the fourth detection switch tube M4; the current output end of the fifth detection switch tube M5 is also grounded through the sixth detection switch tube M6 and the seventh detection switch tube M7 in sequence, and the control end of the sixth detection switch tube M6 is connected to its current input end and connected to the control end of the eighth detection switch tube M8, and the control end of the seventh detection switch tube M7 is connected to its current input end; The first branch of the current mirror includes a first detection switch tube M1, the second branch includes a second detection switch tube M2, and the third branch includes a third detection switch tube M3, and the control end of the first detection switch tube M1, the control end of the second detection switch tube M2 and the control end of the third detection switch tube M3 are connected and connected to the current input end of the first detection switch tube M1.

2. The circuit structure according to claim 1, characterized in that: The parameters of the first detection switch tube M1, the second detection switch tube M2 and the third detection switch tube M3 are the same; the parameters of the fourth detection switch tube M4 and the fifth detection switch tube M5 are the same; the resistance value of the first detection resistor ra1 and the second detection resistor ra2 are the same.

3. The circuit structure according to claim 2, characterized in that: The first detection switch tube M1, the second detection switch tube M2, the third detection switch tube M3, the sixth detection switch tube M6, the seventh detection switch tube M7, the eighth detection switch tube M8 and the ninth detection switch tube M9 are all NMOS tubes or NPN transistors; The fourth detection switch tube M4 and the fifth detection switch tube M5 are both PMOS tubes or PNP transistors.

4. The circuit structure according to any one of claims 1 to 3, characterized in that: The load open circuit detection circuit detects the output voltage vout and the power supply voltage vdd, and determines that an open circuit fault occurs in the battery load when a voltage difference between the output voltage vout and the power supply voltage vdd is less than a preset threshold.

5. The circuit structure according to claim 4, characterized in that: In the battery charging circuit, the power supply voltage vdd is grounded through the second resistor r2, the first power switch tube Ma and the first resistor r1 in sequence, and the control end of the first power switch tube Ma is connected to the output end of the first operational amplifier A1; the non-inverting input end of the first operational amplifier A1 is connected to the reference voltage vref, and the inverting input end is connected to the current output end of the first power switch tube Ma; The power supply voltage vdd is also grounded through the third resistor r3, the second power switch tube Mp and the battery load in sequence, and the control end of the second power switch tube Mp is connected to the output end of the second operational amplifier A2; the non-phase input end of the second operational amplifier A2 is connected to the current input end of the first power switch tube Ma, and the inverting input end is connected to the current input end of the second power switch tube Mp.

6. The circuit structure according to claim 5, characterized in that: The rated value of the output voltage vout is set to be less than or equal to vdd-i1×rb-i1×rc, where i1 is the first current i1 generated by the first detection current source B1 after the load open circuit detection circuit is powered on.

7. The circuit structure according to claim 6, characterized in that: The preset threshold is set to i1×rb.

8. The circuit structure according to any one of claims 1 to 3 and 5 to 7, characterized in that: When the battery charging circuit works normally, the load open circuit detection circuit outputs a high-level detection voltage vb; when the battery load has an open circuit fault, the output voltage vout increases to a voltage difference between the output voltage vout and the power supply voltage vdd that is less than a preset threshold, and the load open circuit detection circuit outputs a low-level detection voltage vb.

9. The circuit structure according to claim 8, characterized in that: The load open circuit detection circuit is connected to the protection execution circuit. When an open circuit fault occurs in the battery load, the load open circuit detection circuit triggers the protection execution circuit to protect the battery charging circuit.

10. The circuit structure according to claim 8, characterized in that: It also includes a locking circuit, and the load open circuit detection circuit is connected to the protection execution circuit through the locking circuit. When an open circuit fault occurs in the battery load, the locking circuit triggers the protection execution circuit to protect the battery charging circuit.

11. The circuit structure according to claim 10, characterized in that: The locking circuit includes a D trigger. When an open circuit fault occurs in the battery load, the load open circuit detection circuit outputs a low-level detection voltage vb. The D trigger latches the low-level detection voltage vb and generates a low-level locking voltage vc to be input into the protection execution circuit.

12. A battery charging device, characterized in that: It comprises a circuit structure with a load open circuit detection function as described in any one of claims 1 to 11.

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