Circuit structure with load open circuit detection function

Abstract

The invention discloses a circuit structure with a load open circuit detection function, and relates to the technical field of battery charging. The circuit structure comprises a battery charging circuit and a load open circuit detection circuit. The battery charging circuit is used for providing charging current and charging voltage for a battery load and inputting the charging voltage as 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 a second branch of the current mirror in sequence; the output voltage is grounded through the second detection resistor, the fifth detection switch tube and the third branch of the current mirror in sequence, and the control end of the fifth detection switch tube is connected with the control end of the fourth detection switch tube. The load open-circuit detection circuit of the scheme detects the output voltage and the power supply voltage, judges whether the battery load has an open-circuit fault through the voltage difference between the output voltage and the power supply voltage, and improves 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 in particular to a circuit structure with a load open circuit detection function. Background Art

[0002] In the prior art battery charging circuit, in order to ensure the safety and reliability of the charging circuit, it is usually necessary to monitor the state of the battery load. Figure 1 In the circuit structure shown, when an open circuit fault occurs in the battery load, if it cannot be discovered and handled 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 cause dangerous situations such as battery heating, expansion, leakage and explosion.

[0003] Therefore, how to achieve real-time monitoring of the load status of the battery charging circuit and fault warning is a technical problem that needs to be solved urgently. 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 a battery charging circuit, thereby monitoring the battery load state and improving the safety of the circuit.

[0005] To achieve the above object, the present invention discloses the following technical solution: In a first aspect of the present invention, a circuit structure with a load open circuit detection function is provided, the circuit structure comprising 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 a battery load, and input 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.

[0006] In a possible implementation, 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.

[0007] In a possible implementation, 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; and the first detection resistor ra1 and the second detection resistor ra2 have the same resistance value.

[0008] In a possible implementation, 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.

[0009] In a possible implementation of the above circuit structure, 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 the battery load has an open circuit fault.

[0010] In a possible implementation, 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.

[0011] In a possible implementation, the rated value of the output voltage vout is set to be less than or equal to , wherein i1 is the first current i1 generated by the first detection current source B1 after the load open circuit detection circuit is powered on. The preset threshold is set to .

[0012] In a possible implementation of the above circuit structure, when the battery charging circuit works normally, the load open circuit detection circuit outputs a high-level detection voltage vb; when an open-circuit fault occurs in the battery load, the load open circuit detection circuit outputs a low-level detection voltage vb.

[0013] In a possible implementation, the load open circuit detection circuit is connected to a protection execution circuit. When an open circuit fault occurs in the battery load, when 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, the load open circuit detection circuit triggers the protection execution circuit to protect the battery charging circuit.

[0014] In a possible implementation, the circuit structure further 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.

[0015] In one possible implementation, 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.

[0016] A second aspect of the present invention provides a battery charging device, which includes the circuit structure with a load open circuit detection function as described in the first aspect.

[0017] The effects provided in the content of the invention are only the effects of the embodiments, not all the effects of the invention. One of the above technical solutions has the following advantages or beneficial effects: The present application provides a circuit structure with a load open circuit detection function, including 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, and detects the output voltage and power supply voltage of the battery charging circuit. The voltage difference between the output voltage and the power supply voltage can be used to determine whether the battery load has an open circuit fault, thereby 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

[0018] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0019] Figure 1 It is a schematic diagram of a battery charging circuit in the prior art; Figure 2 A schematic diagram of a circuit structure with a load open circuit detection function according to an embodiment of the present application; Figure 3 This is a schematic diagram of a circuit with a load open circuit detection function according to an embodiment of the present application; Figure 4 This is a schematic diagram of a circuit with a load open circuit detection function according to another embodiment of the present application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0021] It should be noted that references to "one embodiment", "embodiment", "example embodiment", etc. in this specification refer to the embodiment being described which 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. Furthermore, when describing specific features, structures or characteristics in conjunction with an embodiment, whether or not there is an explicit description, it is indicated that incorporating such features, structures or characteristics into other embodiments is within the knowledge of those skilled in the art.

[0022] Figure 1 This is a schematic diagram of a battery charging circuit in the prior art. 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 tube Ma, a second power switch tube Mp and a battery load. 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-inverting 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.

[0023] Depend on Figure 1 It can be seen that in this circuit, the first operational amplifier A1 can adjust the current output terminal voltage vas of the first power switch tube Ma to be equal to the reference voltage vref. At this time, the current on the first resistor r1 can be obtained , so that the current input terminal voltage of the first power switch tube Ma can be obtained Since the second operational amplifier A2 can adjust the current input terminal voltage vps of the second power switch tube Mp to be equal to the voltage vad, the current flowing through the third resistor r3 can be obtained, that is, the output current .

[0024] when Figure 1 When the battery charging circuit in the circuit has a load open circuit fault, 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 current input terminal voltage vps of the second power switch tube Mp is ≈ the power supply voltage vdd. From the above analysis, it can be seen that under the action of the first operational amplifier A1, the voltage vad is a fixed value. , so 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 the control voltage vg is input to the control end of the second power switch tube Mp, the voltage difference between the control end of the second power switch tube Mp and its current input end is relatively large, while the output current iout flowing through the second power switch tube Mp is relatively small. Therefore, at this time, it can be obtained that the voltage difference between the current input end and the current output end of the second power switch tube Mp is relatively small, that is, at this time, the output voltage vout≈voltage vps≈power supply voltage vdd.

[0025] From the above analysis, we can see that when Figure 1When the circuit in FIG. 1 has a load open circuit fault, the output voltage vout≈the power supply voltage vdd. Therefore, the output voltage vout and the power supply voltage vdd can be further detected, 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.

[0026] based on Figure 1 In view of the above characteristics of the battery charging circuit, the present application embodiment provides a circuit structure with a load open circuit detection function. Figure 2 As shown, in one embodiment, the circuit structure includes a battery charging circuit 110 and a load open circuit detection circuit 120. The battery charging circuit 110 is Figure 1 The circuit shown in FIG. 1 is used to provide a stable and reliable charging current and charging voltage for a battery load. The load open circuit detection circuit 120 is connected to the battery charging circuit 110, and can monitor the battery load state in real time 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 an open circuit fault occurs in the battery load, so that protective measures can be taken in time to improve the safety of the circuit.

[0027] Figure 3 FIG. 1 is a schematic diagram of a circuit with a load open circuit detection function according to an embodiment of the present application. Figure 3 As shown, in the load open circuit detection circuit 120 of the present 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 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 vb.

[0028] Continue to refer Figure 3In the load open circuit detection circuit 120, the output voltage vout of the battery charging circuit 110 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.

[0029] 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 the 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 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, 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 voltage vb, it can be determined whether the battery load has an open circuit fault, thereby realizing real-time monitoring of the battery load state and fault warning, and improving the safety and reliability of the circuit.

[0030] 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, 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. 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 value of the first detection resistor ra1 is the same as that of the second detection resistor ra2.

[0031] 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 tubes or NPN transistors. The second power switch tube Mp, the fourth detection switch tube M4 and the fifth detection switch tube M5 are all PMOS tubes or PNP transistors.

[0032] In addition, in some embodiments, the rated value of the output voltage vout is set to be less than or equal to , wherein i1 is the first current i1 generated by the first detection current source B1 after the load open circuit detection circuit 120 is powered on. Corresponding to the rated value of the output voltage vout, the preset threshold is set to .

[0033] Next, based on Figure 3 The circuit structure of the embodiment, its working principle and working process are described in detail.

[0034] After the circuit starts to power on, the first detection current source B1 pulls up the control terminal voltage of the first detection switch tube M1, the second detection switch tube M2 and the third detection switch tube M3, and the first detection switch tube M1, the second detection switch tube M2 and the third detection switch tube M3 are turned on. Afterwards, the control terminal voltage of the fourth detection switch tube M4 is pulled down through the second detection switch tube M2, and the fourth detection switch tube M4 is turned on. At this time, Figure 3 From the circuit structure, it can be seen that the first detection switch tube M1, the second detection switch tube M2 and the third detection switch tube 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 tube M4 and the second detection switch tube M2, that is, i1=i2.

[0035] At the same time, when the circuit is just powered on, the output voltage vout of the battery charging circuit 110 is 0, so the fifth detection switch tube M5 is in the off state, and the fifth current i5 flowing through the fifth detection switch tube M5 is also 0. At this time, the control terminal voltage va of the sixth detection switch tube M6 and the eighth detection switch tube M8 is pulled down by the third detection switch tube M3, and the sixth detection switch tube M6 and the eighth detection switch tube M8 are in the off state. The detection voltage vb output by the load open circuit 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 tube M9, the ninth detection switch tube M9 is turned on. At this time, the fourth detection resistor rc is short-circuited by the ninth detection switch tube M9.

[0036] Afterwards, during the process of circuit power-up regulation, the output voltage vout continues to increase. 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 circuit 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 tube M5 is pulled down through the second detection switch tube M2, the fifth detection switch tube M5 is turned on, and the fifth current i5 flows through the fifth detection switch tube M5, and the third current i3 flows through the third detection switch tube M3.

[0037] When the voltage vx of the current input terminal of the fourth detection switch tube M4 is equal to the voltage vy of the current input terminal of the fifth detection switch tube M5, that is, vx=vy, the voltage difference between the current input terminal of the fourth detection switch tube M4 and its control terminal is equal to the voltage difference between the current input terminal of the fifth detection switch tube M5 and its control terminal. Therefore, at this time, the second current i2 flowing through the fourth detection switch tube M4 is equal to the fifth current i5 flowing through the fifth detection switch tube M5, that is, i2=i5. Since the first detection switch tube M1, the second detection switch tube M2 and the third detection switch tube M3 form a 1:1:1 current mirror structure, the second current i2 flowing through the second detection switch tube M2 is equal to the third current i3 flowing through the third detection switch tube M3, that is, i2=i3. At this time, the third current i3 flowing through the third detection switch tube M3 is equal to the fifth current i5 flowing through the fifth detection switch tube M5, that is, i3=i5. Therefore, at this time, the control terminal voltage va of the sixth detection switch tube M6 and the eighth detection switch tube M8 is at a low level, the sixth detection switch tube M6 and the eighth detection switch tube M8 are in the off state, and the detection voltage vb output by the load open circuit detection circuit 120 is at a high level.

[0038] When 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, that is, vx>vy, the voltage difference between the current input terminal of the fourth detection switch tube M4 and its control terminal is greater than the voltage difference between the current input terminal of the fifth detection switch tube M5 and its control terminal. Therefore, at this time, the second current i2 flowing through the fourth detection switch tube M4 is greater than the fifth current i5 flowing through the fifth detection switch tube M5, that is, i2>i5. In addition, since the first detection switch tube M1, the second detection switch tube M2 and the third detection switch tube M3 form a 1:1:1 current mirror structure, the second current i2 flowing through the second detection switch tube M2 is equal to the third current i3 flowing through the third detection switch tube M3, that is, i2=i3. At this time, the third current i3 flowing through the third detection switch tube M3 should be greater than the fifth current i5 flowing through the fifth detection switch tube M5, but due to Figure 3It can be seen from the circuit structure that the current input end of the third detection switch tube M3 is connected to the control end of the sixth detection switch tube M6 and the eighth detection switch tube M8, while the control end of the sixth detection switch tube M6 and the eighth detection switch tube M8 (such as the gate of the NMOS tube or the base of the NPN transistor) will not flow current in the direction of the current input end. Therefore, at this time, the third current i3 flowing through the third detection switch tube M3 is less than the second current i2 flowing through the second detection switch tube M2, that is, the third current i3 flowing through the third detection switch tube M3 is equal to the fifth current i5 flowing through the fifth detection switch tube M5. However, the current pull-down capability of the third detection switch tube M3 is greater than the current pull-up capability of the fifth detection switch tube M5, so the control end voltage va of the sixth detection switch tube M6 and the eighth detection switch tube M8 is in a low level state, the sixth detection switch tube M6 and the eighth detection switch tube 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.

[0039] When the voltage vx of the current input terminal of the fourth detection switch tube M4 is less than the voltage vy of the current input terminal of the fifth detection switch tube M5, that is, vx<vy, the voltage difference between the current input terminal of the fourth detection switch tube M4 and its control terminal is less than the voltage difference between the current input terminal of the fifth detection switch tube M5 and its control terminal. Therefore, at this time, the second current i2 flowing through the fourth detection switch tube M4 is less than the fifth current i5 flowing through the fifth detection switch tube M5, that is, i2<i5. Since the first detection switch tube M1, the second detection switch tube M2 and the third detection switch tube M3 form a current mirror structure of 1:1:1, the second current i2 flowing through the second detection switch tube M2 is equal to the third current i3 flowing through the third detection switch tube M3, that is, i2=i3. At this time, the third current i3 flowing through the third detection switch tube M3 is less than the fifth current i5 flowing through the fifth detection switch tube M5. Therefore, at this time, the circuit generates a fourth current i4 flowing from the fifth detection switch tube M5 to the sixth detection switch tube M6, and the control terminal voltage va of the sixth detection switch tube M6 and the eighth detection switch tube M8 is pulled up, and the sixth detection switch tube M6 and the eighth detection switch tube M8 are turned on. The control terminal voltage of the seventh detection switch tube M7 is pulled up by the sixth detection switch tube M6, and the seventh detection switch tube M7 is turned on. At this time, the fourth current i4 flows into the series branch composed of the sixth detection switch tube M6 and the seventh detection switch tube M7. At the same time, the series branch composed of the sixth detection switch tube M6 and the seventh detection switch tube M7 can make the control terminal voltage of the eighth detection switch tube M8 equal to twice the voltage difference between the current input terminal and the control terminal when the switch tube is working normally, thereby ensuring that when the eighth detection switch tube M8 can be turned on, it still has a large current pull-down capability. At this time, the detection voltage vb output by the load open circuit detection circuit 120 is pulled down to a low level state.

[0040] From the above analysis, we can see that Figure 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 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 .

[0041] 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 is not contradictory to the first current i1 being 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 detection circuit 120 is in a high level state, and the ninth detection switch tube M9 is always in a conducting state.

[0042] 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 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 .

[0043] When the output voltage vout continues to increase, the voltage difference between the output voltage vout and the power supply voltage vdd is now less than the preset threshold , 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 circuit 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 circuit detection circuit 120. At this time, the voltage vx at the current input terminal of the fourth detection switch tube M4 is reduced to , thereby ensuring that the current input terminal voltage vx of the fourth detection switch tube M4 is less than the current input terminal voltage vy of the fifth detection switch tube M5, avoiding the load open circuit detection circuit 120 from oscillating near the current input terminal voltage vx of the fourth detection switch tube M4 is equal to the current input terminal voltage vy of the fifth detection switch tube M5, and improving the stability of the load open circuit detection circuit 120.

[0044] After detecting an abnormal situation such as an open circuit in the battery load, in order to prevent the circuit from being damaged due to the abnormal situation, such as Figure 3 As shown, in this embodiment, the load open circuit detection circuit 120 is also connected to the protection execution circuit 140. When the battery load fails, the load open circuit 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 a circuit structure commonly used in the prior art, such as a comparator protection circuit, a threshold protection circuit, etc., which will not be repeated here.

[0045] From the above analysis, we can see that Figure 3 The circuit structure of the embodiment, on the one hand, when the battery charging circuit 110 works normally, the load open circuit detection circuit 120 outputs a high-level detection voltage vb. When the battery load has an open circuit fault, the output voltage increases to a voltage difference between the output voltage and the power supply voltage that is less than a preset threshold value, and the load open circuit detection circuit 120 outputs a low-level detection voltage vb, and the detection voltage vb is input to the protection execution circuit 140, which can trigger the protection execution circuit 140 to protect the battery charging circuit 110 when the battery has an open circuit fault, thereby improving the safety and reliability of the battery load and the charging circuit. On the other hand, the load open circuit detection circuit 120 in this embodiment can avoid oscillation near the current input terminal voltage vx of the fourth detection switch tube M4 equals the current input terminal voltage vy of the fifth detection switch tube M5, thereby improving the stability of the circuit structure.

[0046] 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 a practical 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 ).

[0047] Therefore, in order to avoid the situation in actual application where the load open-circuit fault has recovered by itself before the protection execution circuit 140 has had time to take protection actions, 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 in another embodiment 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.

[0048] 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 low-level detection voltage vb, and the D flip-flop latches the low-level detection voltage vb and outputs a low-level locking voltage vc.

[0049] like Figure 4 As shown, when the battery charging circuit 110 works normally, the detection voltage vb output by the load open circuit detection circuit 120 is at a high level, and at this time, the locking voltage vc output by the locking circuit 130 is also at a high level. When an open circuit fault occurs in the load, the detection voltage vb output by the load open circuit detection circuit 120 switches to a low level, and at this time, the locking voltage vc output by the locking circuit 130 also switches to a low level. Afterwards, even if the load open circuit fault recovers by itself, the detection voltage vb output by the load open circuit detection circuit 120 switches back to a high level, and the locking voltage vc output by the locking circuit 130 still remains at a low level, so that after an open circuit fault occurs in the load, the low-level locking voltage vc is input to the protection execution circuit 140, ensuring that the protection execution circuit 140 can protect the battery charging circuit 110.

[0050] From the above analysis, we can see that Figure 4 A locking circuit 130 is provided in the circuit structure of the embodiment, and the load open circuit detection circuit 120 is connected to the protection execution circuit 140 through the locking circuit 130, so that after a load open circuit fault occurs in the circuit, regardless of whether the load open circuit fault recovers automatically, the locking circuit 130 outputs a corresponding locking signal to the protection execution circuit 140, ensuring that the protection execution circuit 140 can protect the battery charging circuit 110, thereby further improving the safety and reliability of the battery and the charging circuit.

[0051] It should be noted that Figure 3 Example Figure 4 The circuit structure with load open circuit detection function shown in the embodiment is only a preferred circuit structure to achieve the purpose of the present invention. In other embodiments, each circuit module or device can also use other circuit structures that can achieve the same function, and the present application is not limited to this.

[0052] In addition, the embodiment of the present application also provides a battery charging device, which includes a circuit structure with a load open circuit detection function as in the above embodiment, and is used to provide safe and reliable electric energy to the load. For the circuit structure and working process of the battery charging device not described in detail in this embodiment, reference can be made to the relevant parts in the above embodiment of the circuit structure with a load open circuit detection function, and no further description is given here.

[0053] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls 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.

2. The circuit structure according to claim 1, characterized in that: 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.

3. The circuit structure according to claim 2, 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.

4. The circuit structure according to claim 3, 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.

5. The circuit structure according to any one of claims 1 to 4, 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.

6. The circuit structure according to claim 5, 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.

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

8. The circuit structure according to claim 7, characterized in that: The preset threshold is set to .

9. The circuit structure according to any one of claims 1 to 4 and 6 to 8, 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.

10. The circuit structure according to claim 9, 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.

11. The circuit structure according to claim 9, 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.

12. The circuit structure according to claim 11, 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.

13. 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 12.

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