Constant current charging and dual power supply uninterrupted switching circuit for new energy vehicle

Abstract

The invention discloses a constant-current charging and dual-power-supply uninterrupted switching circuit for a new energy vehicle. The constant-current charging and dual-power-supply uninterrupted switching circuit comprises a constant-current charging control circuit, a voltage acquisition circuit, a turn-off circuit S1, a turn-off circuit S2 and a comparator circuit, the two input ends of the constant-current charging control circuit are respectively connected with the DCDC converter and one input end of the comparator circuit, and the output end of the constant-current charging control circuit is connected with the storage battery; one end of the voltage acquisition circuit is connected with the storage battery, and the other end of the voltage acquisition circuit is connected with the DCDC converter; the other input end of the comparator circuit is connected with the voltage sampling circuit, the output end of the comparator circuit is connected with the input end of the turn-off circuit S1 and the input end of the turn-off circuit S2, the input end of the turn-off circuit S1 is further connected with the input end of the turn-off circuit S2, the output end of the turn-off circuit S1 is connected with the storage battery, and the output end of the turn-off circuit S2 is connected with the DCDC converter. And the other output end of the turn-off circuit S2 is connected with the other output end of the turn-off circuit S1. According to the invention, the functions of constant-current charging and uninterrupted switching of the dual power supplies are realized through a small number of electronic devices, and the functional safety level of the new energy vehicle is improved.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology of new energy vehicles, and in particular to a control circuit for charging a low-voltage battery through a DCDC converter and outputting power from the battery and the DCDC converter to the outside. Background Art

[0002] In new energy vehicles, the high-voltage battery pack charges the low-voltage battery through the DCDC converter, and the power supply to the load cannot be interrupted. When the DCDC converter is abnormal or the battery voltage is low, the charging current to the low-voltage battery will increase, and there are some potential hidden dangers: ① Damage to the battery: Due to excessive current, the chemical reaction inside the battery may get out of control, thereby accelerating the aging process of the battery and shortening its service life. ② Damage to the electrode plate: Long-term use of high-current charging may damage the battery plate, resulting in water loss and bulging. ③ Safety hazards: During high-current charging, the internal heating of the battery will cause the external temperature of the battery to rise, and even when it is too high, it will cause safety problems such as battery short circuit and explosion. Therefore, there will be a momentary interruption when the DCDC converter and the battery power supply are switched to each other, affecting the function of the electronic components and bringing too high charging current. Excessive charging current is prone to battery safety hazards. To solve the above problems, it is necessary to control the current of the charging circuit and ensure that the functional safety is not degraded when switching between the battery power supply or the DCDC converter power supply.

[0003] The invention with application number 202111480150.3 discloses a battery management circuit and a battery device, including: an acquisition circuit, a processing circuit, a first switch element, a second switch element and a limiting circuit; the acquisition circuit is connected to the battery; the second end of the first switch element is connected to the first end of the second switch element, and the second end of the second switch element is grounded; the first end of the limiting circuit is connected to the first end of the first switch element, and the second end of the limiting circuit is connected to the second end of the first switch element; the processing circuit is connected to the acquisition circuit, the control end of the first switch element and the control end of the second switch element; the processing circuit switches to a normal charging mode or a current limiting charging mode by controlling the states of the first switch element and the second switch element according to the working environment of the battery detected by the acquisition circuit. The acquisition circuit is used to collect circuit parameters, the processing circuit is used to switch the charging mode, and the limiting circuit is used to complete the current limiting, so that the battery can be automatically charged normally or with current limiting under different working conditions. However, the above invention can only control normal charging and current limiting charging, and cannot prevent reverse cutoff (such as when the DCDC converter fails, the battery shall not supply power to the DCDC converter), nor can it achieve uninterrupted power supply when the battery and the DCDC converter switch to the next stage power supply. Summary of the invention

[0004] The present invention proposes a constant current charging and dual power supply uninterruptible switching circuit for new energy vehicles, so as to solve the technical problem that when the high-voltage battery pack of the new energy vehicle charges the low-voltage battery through the DCDC converter, a momentary interruption occurs when the power supply of the DCDC converter and the battery are switched to each other, resulting in the electronic components failing to meet the functional safety requirements, which easily causes a battery safety hazard.

[0005] In order to achieve the above object, the technical solution of the present invention is achieved as follows: A constant current charging and dual power supply uninterruptible switching circuit for new energy vehicles, including a constant current charging control circuit, a voltage acquisition circuit, a shutdown circuit S1, a shutdown circuit S2 and a comparator circuit; The input end of the constant current charging control circuit is connected to the DCDC converter, the other input end of the constant current charging control circuit is connected to an input end of the comparator circuit, and the output end of the constant current charging control circuit is connected to the battery; one end of the voltage acquisition circuit is connected to the battery, and the other end of the voltage acquisition circuit is connected to the DCDC converter; the other input end of the comparator circuit is connected to the voltage sampling circuit, an output end of the comparator circuit is connected to the input end of the shutdown circuit S1, and the other output end of the comparator circuit is connected to the input end of the shutdown circuit S2, the input end of the shutdown circuit S1 is also connected to the input end of the shutdown circuit S2, the output end of the shutdown circuit S1 is connected to the battery, the output end of the shutdown circuit S2 is connected to the DCDC converter, and the other output end of the shutdown circuit S2 is connected to the other output end of the shutdown circuit S1.

[0006] Preferably, the constant current charging control circuit includes an anti-backflow diode, a slow-start capacitor, a sampling resistor, a transistor, a voltage-stabilizing diode and a fifth MOS transistor; the positive electrode of the anti-backflow diode is connected to the DCDC converter, and the negative electrode of the anti-backflow diode is respectively connected to one end of the slow-start capacitor, one end of the sampling resistor, and the emitter of the transistor; the other end of the slow-start capacitor and the collector of the transistor are both connected to an input end of the comparator circuit; the other end of the sampling resistor is respectively connected to the base of the transistor, the negative electrode of the voltage-stabilizing diode, and the source of the fifth MOS transistor, the positive electrode of the voltage-stabilizing diode and the gate of the fifth MOS transistor are both connected to an input end of the comparator circuit, and the drain of the fifth MOS tube is connected to the battery.

[0007] Preferably, the voltage acquisition circuit includes a first resistor, a second resistor, a third resistor and a fourth resistor; one end of the first resistor is connected to the battery, and the other end of the first resistor is respectively connected to one end of the second resistor and the other input end of the comparator circuit; the other end of the second resistor is respectively connected to the system ground and one end of the third resistor; the other end of the third resistor is respectively connected to one end of the fourth resistor and an input end of the comparator circuit, and the other end of the fourth resistor is connected to the DCDC converter.

[0008] Preferably, the comparator circuit includes a lower operational amplifier and an upper operational amplifier, the non-inverting input terminal of the upper operational amplifier is respectively connected to the other end of the first resistor, one end of the second resistor, and the inverting input terminal of the lower operational amplifier, the inverting input terminal of the upper operational amplifier is respectively connected to the other end of the third resistor, the non-inverting input terminal of the lower operational amplifier, the other end of the slow start capacitor in the constant current charging control circuit, the collector of the transistor, the positive electrode of the voltage regulator diode, and the gate of the fifth MOS tube, the output terminal of the upper operational amplifier is connected to the input terminal of the shutdown circuit S1, and the output terminal of the lower operational amplifier is connected to the input terminal of the shutdown circuit S2.

[0009] Preferably, a first bleeder resistor and a second bleeder resistor are provided between the input end of the shutdown circuit S1 and the input end of the shutdown circuit S2, one end of the first bleeder resistor is connected to the input end of the shutdown circuit S1, the other end of the first bleeder resistor is respectively connected to one end of the second bleeder resistor and the system ground, one end of the second bleeder resistor is also connected to the system ground, and the other end of the second bleeder resistor is connected to the input end of the shutdown circuit S2.

[0010] Preferably, the other output end of the shutdown circuit S1 and the other output end of the shutdown circuit S2 are also connected to a switching holding capacitor, one end of the switching holding capacitor is respectively connected to the other output end of the shutdown circuit S1 and the other output end of the shutdown circuit S2, and the other end of the switching holding capacitor is connected to the system ground.

[0011] Preferably, the parameters of the switching holding capacitor are selected according to: V t =V0exp(-t / RC), where V t is the voltage on the switching holding capacitor C2 at time t, V0 is the initial voltage of the switching holding capacitor C2, R is the load resistance, and C is the capacity of the switching holding capacitor C2.

[0012] Preferably, the shutdown circuit S1 includes a first MOS tube and a second MOS tube; the shutdown circuit S2 includes a third MOS tube and a fourth MOS tube; the source of the first MOS tube is connected to the battery, the drain of the first MOS tube is connected to the drain of the second MOS tube, and the gate of the first MOS tube is respectively connected to the output end of the upper operational amplifier of the comparator circuit and one end of the first discharge resistor; the source of the second MOS tube is respectively connected to the source of the fourth MOS tube and one end of the switching holding capacitor, and the gate of the second MOS tube is respectively connected to the output end of the upper operational amplifier of the comparator circuit and one end of the first discharge resistor; the source of the third MOS tube is connected to the DCDC converter, the drain of the third MOS tube is connected to the drain of the fourth MOS tube, and the gate of the third MOS tube is respectively connected to the output end of the lower operational amplifier of the comparator circuit and the other end of the second discharge resistor; the source of the fourth MOS tube is connected to one end of the switching holding capacitor, and the gate of the fourth MOS tube is respectively connected to the output end of the lower operational amplifier of the comparator circuit and the other end of the second discharge resistor.

[0013] Preferably, the voltage acquisition circuit acquires the battery voltage and the DCDC converter voltage and transmits the acquisition result to the comparator circuit, and the comparator circuit controls the on and off of the shutdown circuit S1 and the shutdown circuit S2 according to the acquisition result; when the shutdown circuit S1 is turned on and the shutdown circuit S2 is turned off, the output voltage is powered by the battery; when the shutdown circuit S1 is turned off and the shutdown circuit S2 is turned on, the output voltage is powered by the DCDC converter.

[0014] Preferably, when the battery voltage and the DCDC converter voltage are close, if the product of the current collected on the sampling resistor of the constant current charging control circuit and the resistance value of the sampling resistor is less than a predetermined value, the transistor of the constant current charging control circuit does not work, and the magnitude of the output current is completely determined by the magnitude of the battery voltage. When the product of the current flowing through the sampling resistor and the resistance value of the sampling resistor is greater than a predetermined value, the voltage on the sampling resistor of the constant current charging control circuit turns on the emitter junction of the transistor, and the transistor of the constant current charging control circuit turns on and works, and the transistor of the constant current charging control circuit After being turned on, the voltage stored on the junction capacitor of the gate-source voltage of the fifth MOS tube of the constant current charging control circuit is discharged through the triode, so that the gate-source voltage of the fifth MOS tube of the constant current charging control circuit decreases. As the gate-source voltage of the fifth MOS tube of the constant current charging control circuit decreases, the equivalent resistance between the DS poles of the fifth MOS tube of the constant current charging control circuit increases, and the total impedance of the entire loop remains unchanged, limiting the trend of the output current exceeding the current limit value due to the increase in load, ensuring that the output current does not exceed the current limit value, and realizing constant current charging. The predetermined value is 0.7V.

[0015] Compared with the prior art, the present invention has the following beneficial effects: the present invention realizes the functions of constant current charging and uninterrupted switching of dual power supplies through a small number of electronic devices, thereby improving the functional safety level of new energy vehicles; it has significant advantages in terms of charging efficiency, battery life, system reliability, power supply continuity, system availability, maintenance cost and user experience. These advantages make the present invention the preferred solution in many fields, especially in those occasions where higher requirements are placed on the stability and continuity of power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 FIG. 4 is a circuit diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] like Figure 1 As shown, a constant current charging and dual power supply uninterruptible switching circuit for new energy vehicles includes a constant current charging control circuit, a voltage acquisition circuit, a shutdown circuit S1, a shutdown circuit S2 and a comparator circuit.

[0020] The input end of the constant current charging control circuit is connected to the DCDC converter, the other input end of the constant current charging control circuit is connected to an input end of the comparator circuit, and the output end of the constant current charging control circuit is connected to the battery; one end of the voltage acquisition circuit is connected to the battery, and the other end of the voltage acquisition circuit is connected to the DCDC converter; the other input end of the comparator circuit is connected to the voltage sampling circuit, an output end of the comparator circuit is connected to the input end of the shutdown circuit S1, and the other output end of the comparator circuit is connected to the input end of the shutdown circuit S2, the input end of the shutdown circuit S1 is also connected to the input end of the shutdown circuit S2, the output end of the shutdown circuit S1 is connected to the battery, the output end of the shutdown circuit S2 is connected to the DCDC converter, and the other output end of the shutdown circuit S2 is connected to the other output end of the shutdown circuit S1.

[0021] The constant current charging control circuit is used to control the DCDC converter to perform constant current charging on the battery when the battery voltage is lower than the output voltage of the DCDC converter; the voltage acquisition circuit is used to acquire the battery voltage and the DCDC converter voltage; the comparator circuit is used to control the on and off of the shutdown circuit S1 and the shutdown circuit S2 according to the acquisition result of the voltage acquisition circuit; the shutdown circuit S1 is used to turn on or off the battery power supply, thereby controlling the output of the battery and preventing the output terminal voltage from flowing back; the shutdown circuit S2 is used to turn on or off the DCDC converter power supply.

[0022] Furthermore, the other output end of the shutdown circuit S1 and the other output end of the shutdown circuit S2 are also connected to a switching holding capacitor C2, one end of the switching holding capacitor C2 is respectively connected to the other output end of the shutdown circuit S1 and the other output end of the shutdown circuit S2, and the other end of the switching holding capacitor C2 is connected to the system ground GND. The switching holding capacitor C2 is used to maintain the output voltage VCC during the switching process of the shutdown circuit S1 and the shutdown circuit S2 to avoid causing instantaneous power failure of the subsequent circuit.

[0023] Furthermore, the parameter selection of the switching holding capacitor C2 is determined by the switching time difference between the shut-down circuit S1 and the shut-down circuit S2 and the load size: V t =V0exp(-t / RC), where V t is the voltage on the switching holding capacitor C2 at time t, V0 is the initial voltage of the switching holding capacitor C2, R is the load resistance, and C is the capacity of the switching holding capacitor C2.

[0024] A first bleeder resistor R5 and a second bleeder resistor R6 are provided between the input end of the shutdown circuit S1 and the input end of the shutdown circuit S2. One end of the first bleeder resistor R5 is connected to the input end of the shutdown circuit S1, and the other end of the first bleeder resistor R5 is respectively connected to one end of the second bleeder resistor R6 and the system ground GND. One end of the second bleeder resistor R6 is also connected to the system ground GND, and the other end of the second bleeder resistor R6 is connected to the input end of the shutdown circuit S2.

[0025] Furthermore, the constant current charging control circuit includes an anti-backflow diode D1, a slow-start capacitor C1, a sampling resistor R11, a transistor Q6, a voltage regulator diode D2 and a fifth MOS transistor Q5, wherein the sampling resistor R11 and the transistor Q6 form a current regulation control circuit. The positive electrode of the anti-backflow diode D1 is connected to the DCDC converter, and the negative electrode of the anti-backflow diode D1 is respectively connected to one end of the slow-start capacitor C1, one end of the sampling resistor R11, and the emitter of the transistor Q6; the other end of the slow-start capacitor C1 and the collector of the transistor Q6 are both connected to an input end of the comparator circuit; the other end of the sampling resistor R11 is respectively connected to the base of the transistor Q6, the negative electrode of the voltage regulator diode D2, and the source of the fifth MOS transistor Q5, the positive electrode of the voltage regulator diode D2 and the gate of the fifth MOS transistor Q5 are both connected to an input end of the comparator circuit, and the drain of the fifth MOS transistor Q5 is connected to the battery. The voltage stabilizing diode D2 is used to prevent the gate-source voltage Vgs of the fifth MOS transistor Q5 from exceeding the limit when the input voltage fluctuates, thereby preventing the fifth MOS transistor Q5 from being damaged; the sampling resistor R11 is used to collect the current during charging to control the bias state of the transistor Q6 to adjust the charging current; the transistor Q6 is used to adjust the charging current.

[0026] Furthermore, the voltage acquisition circuit includes a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4; one end of the first resistor R1 is connected to the battery, and the other end of the first resistor R1 is respectively connected to one end of the second resistor R2 and the other input end of the comparator circuit; the other end of the second resistor R2 is respectively connected to the system ground GND and one end of the third resistor R3; the other end of the third resistor R3 is respectively connected to one end of the fourth resistor R4 and an input end of the comparator circuit; the other end of the fourth resistor R4 is connected to the DCDC converter.

[0027] Further, the comparator circuit includes a lower operational amplifier U1_A and an upper operational amplifier U1_B, the non-inverting input terminal of the upper operational amplifier U1_B is respectively connected to the other end of the first resistor R1, one end of the second resistor R2, and the inverting input terminal of the lower operational amplifier U1_A, the inverting input terminal of the upper operational amplifier U1_B is respectively connected to the other end of the third resistor R3, the non-inverting input terminal of the lower operational amplifier U1_A, the other end of the slow start capacitor C1 in the constant current charging control circuit, the collector of the transistor Q6, the positive electrode of the voltage regulator diode D2, and the gate of the fifth MOS tube, the output terminal of the upper operational amplifier U1_B is connected to the input terminal of the shutdown circuit S1, and the output terminal of the lower operational amplifier U1_A is connected to the input terminal of the shutdown circuit S2. The lower operational amplifier U1_A and the upper operational amplifier U1_B are used as comparators.

[0028] Furthermore, the voltage division value outputted from the connection point of the first resistor R1 and the second resistor R2 is transmitted to the positive input terminal of the upper operational amplifier U1_B and the inverting input terminal of the upper operational amplifier U1_B, the positive input terminal of the lower operational amplifier U1_A and the inverting input terminal of the lower operational amplifier U1_A, and the lower operational amplifier U1_A and the upper operational amplifier U1_B compare and output a high level or a low level to control the on and off of the shutdown circuit S2 and the shutdown circuit S1. The first discharge resistor R5 is used to discharge the input terminal of the shutdown circuit S1, and pull the voltage of the input terminal of the shutdown circuit S1 down to 0V when the output of the upper operational amplifier U1_B changes from a high level to a low level, and the second discharge resistor R6 is used to discharge the input terminal of the S2 circuit, and pull the voltage of the input terminal of the shutdown circuit S2 down to 0V when the output of the lower operational amplifier U1_A changes from a high level to a low level.

[0029] Further, the shutdown circuit S1 includes a first MOS tube Q1 and a second MOS tube Q2; the shutdown circuit S2 includes a third MOS tube Q3 and a fourth MOS tube Q4; the source of the first MOS tube Q1 is connected to the battery, the drain of the first MOS tube Q1 is connected to the drain of the second MOS tube Q2, and the gate of the first MOS tube Q1 is respectively connected to the output end of the upper operational amplifier U1_B and one end of the first discharge resistor R5; the source of the second MOS tube Q2 is respectively connected to the source of the fourth MOS tube Q4 and one end of the switching holding capacitor C2, and the gate of the first MOS tube Q1 is respectively connected to the output end of the upper operational amplifier U1_B and one end of the first discharge resistor R5. The gate of the third MOS tube Q2 is respectively connected to the output end of the upper operational amplifier U1_B and one end of the first discharge resistor R5; the source of the third MOS tube Q3 is connected to the DCDC converter, the drain of the third MOS tube Q3 is connected to the drain of the fourth MOS tube Q4, and the gate of the third MOS tube Q3 is respectively connected to the output end of the lower operational amplifier U1_A and the other end of the second discharge resistor R6; the source of the fourth MOS tube Q4 is connected to one end of the switching holding capacitor C2, and the gate of the fourth MOS tube Q4 is respectively connected to the output end of the lower operational amplifier U1_A and the other end of the second discharge resistor R6.

[0030] Specifically, when the DCDC converter does not output a voltage, the positive input terminal (PIN5) of the upper operational amplifier U1_B fed back by the voltage acquisition circuit to the comparator circuit is high, the inverting input terminal (PIN6) of the upper operational amplifier U1_B is low, the output terminal (PIN7) of the upper operational amplifier U1_B outputs a high level, and the shutdown circuit S1 is turned on; the inverting input terminal (PIN2) of the lower operational amplifier U1_A is high, the positive input terminal (PIN3) of the lower operational amplifier U1_A is low, the output terminal (PIN1) of the lower operational amplifier U1_A outputs a low level, the shutdown circuit S2 is turned off, and the output voltage VCC is powered by the battery; since the DCDC converter does not output a voltage, the fifth MOS tube Q5 in the constant current charging control circuit is turned off, and the constant current charging control circuit does not work.

[0031] Specifically, when the DCDC converter starts to output voltage, the voltage acquisition circuit detects that the DCDC converter has voltage output, the positive input terminal (PIN5) of the upper operational amplifier U1_B fed back by the voltage acquisition circuit to the comparator is low level, the inverting input terminal (PIN6) of the upper operational amplifier U1_B is high level, the output terminal (PIN7) of the upper operational amplifier U1_B outputs a low level, and the first discharge resistor R5 pulls down the voltage of the output terminal (PIN7) of the upper operational amplifier U1_B to 0V, so that the shutdown circuit S1 is turned off; the inverting input terminal (PIN2) of the lower operational amplifier U1_A is low level, the positive input terminal (PIN3) of the lower operational amplifier U1_A is high level, the output terminal (PIN1) of the lower operational amplifier U1_A outputs a high level, the shutdown circuit S2 is turned on, and the output voltage VCC is powered by the DCDC converter; in the switching process of the shutdown circuit S1 and the shutdown circuit S2, the output voltage VCC is maintained by switching the holding capacitor C2 to avoid causing instantaneous power failure of the subsequent circuit. The third resistor R3 and the fourth resistor R4 collect the output voltage of the DCDC converter. At this time, the voltage at the Net_A terminal increases, so that the fifth MOS tube Q5 in the constant current charging control circuit is turned on, and the DCDC converter starts to charge the battery. When the DCDC converter is just powered on, because the voltage on the slow-start capacitor C1 is zero, the voltage at the Net_A point is the highest at this time. As the slow-start capacitor C1 is charged, the charging current becomes smaller and smaller, the voltage at the Net_A point gradually decreases, and the voltage on the slow-start capacitor C1 becomes larger and larger, thereby ensuring that the gate-source voltage Vgs of the fifth MOS tube Q5 increases slowly, and the slow start of the switching action of the fifth MOS tube Q5 is realized.

[0032] Specifically, when the battery voltage and the DCDC converter voltage are close, if the product of the current collected on the sampling resistor R11 and the resistance value of the sampling resistor R11 is less than 0.7V, the transistor Q6 does not work. At this time, the output current is completely determined by the battery voltage. When the battery voltage is low, the output load of the constant current charging control circuit is relatively large. When the output current flows through the current on the sampling resistor R11 and the product of the resistance value of the sampling resistor R11 is greater than 0.7V, when the output current is about to exceed the current limit value, the voltage on the sampling resistor R11 turns on the emitter junction of the transistor Q6, and the transistor Q6 turns on and works. After the transistor Q6 is turned on, The voltage stored on the junction capacitance of the gate-source voltage Vgs of the fifth MOS tube Q5 will be discharged through the transistor Q6, and the gate-source voltage Vgs of the fifth MOS tube Q5 will decrease. Since the magnitude of the gate-source voltage Vgs of the fifth MOS tube Q5 is related to the magnitude of the resistance between the DS electrodes of the fifth MOS tube, as the gate-source voltage Vgs of the fifth MOS tube Q5 decreases, the equivalent resistance between the DS electrodes of the fifth MOS tube Q5 will increase. When the gate-source voltage Vgs of the fifth MOS tube Q5 decreases to a certain value, that is, the resistance between the DS electrodes of the fifth MOS tube Q5 increases to a certain value, the total impedance of the entire loop remains unchanged. At this time, although the load is increased and the load impedance is reduced, the resistance between the DS electrodes of the fifth MOS tube Q5 increases, which limits the tendency of the output current to exceed the current limit value due to the increase in load, and due to the existence of the emitter junction of the transistor Q6, the current of the entire loop will be clamped to not exceed the current limit value, and finally the gate-source voltage Vgs of the fifth MOS tube Q5 will be stabilized at a value lower than 12V. If the load is further increased at this time, the gate-source voltage Vgs of the fifth MOS tube Q5 will continue to decrease, and the DS electrode resistance of the fifth MOS tube Q5 will continue to increase. The DS electrode resistance of the fifth MOS tube Q5 will make up for the reduced part of the battery load impedance, so that the total impedance of the whole loop remains unchanged, ensuring that the output current does not exceed the current limit value.

[0033] Specifically, when the DCDC converter of the vehicle is abnormal, the positive input terminal (PIN5) of the upper operational amplifier U1_B fed back by the voltage acquisition circuit to the comparator circuit is low, the inverting input terminal (PIN6) of the upper operational amplifier U1_B is high, the output terminal (PIN7) of the upper operational amplifier U1_B outputs a high level, and the shutdown circuit S1 is turned on; the inverting input terminal (PIN2) of the lower operational amplifier U1_A is high, the positive input terminal (PIN3) of the lower operational amplifier U1_A is low, the second discharge resistor R6 pulls the voltage of the output terminal (PIN1) of the lower operational amplifier U1_A down to 0V, the shutdown circuit S2 is cut off, and the output voltage VCC is powered by the battery; during the switching process of the shutdown circuit S1 and the shutdown circuit S2, the output voltage VCC is maintained by switching the holding capacitor C2 to avoid causing instantaneous power failure in the subsequent circuit. The third resistor R3 and the fourth resistor R4 collect the output voltage of the DCDC converter. At this time, the voltage at the Net_A terminal decreases, so that the fifth MOS tube Q5 in the constant current charging control circuit is turned off, and the DCDC converter stops charging the battery.

[0034] Through the above process, the present invention realizes the functions of constant current charging and uninterrupted switching of dual power supplies.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A constant current charging and dual power uninterruptible switching circuit for new energy vehicles, characterized in that: It includes a constant current charging control circuit, a voltage acquisition circuit, a shutdown circuit S1, a shutdown circuit S2 and a comparator circuit; The input end of the constant current charging control circuit is connected to the DCDC converter, the other input end of the constant current charging control circuit is connected to an input end of the comparator circuit, and the output end of the constant current charging control circuit is connected to the battery; one end of the voltage acquisition circuit is connected to the battery, and the other end of the voltage acquisition circuit is connected to the DCDC converter; the other input end of the comparator circuit is connected to the voltage sampling circuit, an output end of the comparator circuit is connected to the input end of the shutdown circuit S1, and the other output end of the comparator circuit is connected to the input end of the shutdown circuit S2, the input end of the shutdown circuit S1 is also connected to the input end of the shutdown circuit S2, the output end of the shutdown circuit S1 is connected to the battery, the output end of the shutdown circuit S2 is connected to the DCDC converter, and the other output end of the shutdown circuit S2 is connected to the other output end of the shutdown circuit S1.

2. The constant current charging and dual power uninterruptible switching circuit for new energy vehicles according to claim 1 is characterized in that: The constant current charging control circuit comprises an anti-backflow diode, a slow-start capacitor, a sampling resistor, a transistor, a voltage-stabilizing diode and a fifth MOS transistor; the positive electrode of the anti-backflow diode is connected to the DCDC converter, the negative electrode of the anti-backflow diode is respectively connected to one end of the slow-start capacitor, one end of the sampling resistor and the emitter of the transistor; the other end of the slow-start capacitor and the collector of the transistor are both connected to an input end of the comparator circuit; the other end of the sampling resistor is respectively connected to the base of the transistor, the negative electrode of the voltage-stabilizing diode and the source of the fifth MOS transistor, the positive electrode of the voltage-stabilizing diode and the gate of the fifth MOS transistor are both connected to an input end of the comparator circuit, and the drain of the fifth MOS transistor is connected to a battery.

3. The constant current charging and dual power uninterruptible switching circuit for new energy vehicles according to claim 2 is characterized in that: The voltage acquisition circuit includes a first resistor, a second resistor, a third resistor and a fourth resistor; one end of the first resistor is connected to the battery, and the other end of the first resistor is respectively connected to one end of the second resistor and the other input end of the comparator circuit; the other end of the second resistor is respectively connected to the system ground and one end of the third resistor; the other end of the third resistor is respectively connected to one end of the fourth resistor and an input end of the comparator circuit, and the other end of the fourth resistor is connected to the DCDC converter.

4. The constant current charging and dual power uninterruptible switching circuit for new energy vehicles according to claim 3 is characterized in that: The comparator circuit includes a lower operational amplifier and an upper operational amplifier, the non-inverting input end of the upper operational amplifier is respectively connected to the other end of the first resistor, one end of the second resistor, and the inverting input end of the lower operational amplifier, the inverting input end of the upper operational amplifier is respectively connected to the other end of the third resistor, the non-inverting input end of the lower operational amplifier, the other end of the slow start capacitor in the constant current charging control circuit, the collector of the transistor, the positive electrode of the voltage regulator diode, and the gate of the fifth MOS tube, the output end of the upper operational amplifier is connected to the input end of the shutdown circuit S1, and the output end of the lower operational amplifier is connected to the input end of the shutdown circuit S2.

5. The constant current charging and dual power uninterruptible switching circuit for new energy vehicles according to claim 1 or 4, characterized in that: A first bleeder resistor and a second bleeder resistor are provided between the input end of the shutdown circuit S1 and the input end of the shutdown circuit S2, one end of the first bleeder resistor is connected to the input end of the shutdown circuit S1, the other end of the first bleeder resistor is respectively connected to one end of the second bleeder resistor and the system ground, one end of the second bleeder resistor is also connected to the system ground, and the other end of the second bleeder resistor is connected to the input end of the shutdown circuit S2.

6. The constant current charging and dual power uninterruptible switching circuit for new energy vehicles according to claim 5, characterized in that: The other output end of the shutdown circuit S1 and the other output end of the shutdown circuit S2 are also connected to a switching holding capacitor, one end of the switching holding capacitor is respectively connected to the other output end of the shutdown circuit S1 and the other output end of the shutdown circuit S2, and the other end of the switching holding capacitor is connected to the system ground.

7. The constant current charging and dual power uninterruptible switching circuit for new energy vehicles according to claim 6, characterized in that: The parameters of the switching holding capacitor are selected according to: V t =V0exp(-t / RC), where V t is the voltage on the switching holding capacitor C2 at time t, V0 is the initial voltage of the switching holding capacitor C2, R is the load resistance, and C is the capacity of the switching holding capacitor C2.

8. The constant current charging and dual power uninterruptible switching circuit for new energy vehicles according to any one of claims 1-4, 6, and 7, characterized in that: The shutdown circuit S1 includes a first MOS tube and a second MOS tube; the shutdown circuit S2 includes a third MOS tube and a fourth MOS tube; the source of the first MOS tube is connected to the battery, the drain of the first MOS tube is connected to the drain of the second MOS tube, and the gate of the first MOS tube is respectively connected to the output end of the upper operational amplifier of the comparator circuit and one end of the first discharge resistor; the source of the second MOS tube is respectively connected to the source of the fourth MOS tube and one end of the switching holding capacitor, and the gate of the second MOS tube is respectively connected to the output end of the upper operational amplifier of the comparator circuit and one end of the first discharge resistor; the source of the third MOS tube is connected to the DCDC converter, the drain of the third MOS tube is connected to the drain of the fourth MOS tube, and the gate of the third MOS tube is respectively connected to the output end of the lower operational amplifier of the comparator circuit and the other end of the second discharge resistor; the source of the fourth MOS tube is connected to one end of the switching holding capacitor, and the gate of the fourth MOS tube is respectively connected to the output end of the lower operational amplifier of the comparator circuit and the other end of the second discharge resistor.

9. The constant current charging and dual power uninterruptible switching circuit for new energy vehicles according to claim 8, characterized in that: The voltage acquisition circuit acquires the battery voltage and the DCDC converter voltage and transmits the acquisition result to the comparator circuit, and the comparator circuit controls the on and off of the shutdown circuit S1 and the shutdown circuit S2 according to the acquisition result; when the shutdown circuit S1 is turned on and the shutdown circuit S2 is turned off, the output voltage is powered by the battery; when the shutdown circuit S1 is turned off and the shutdown circuit S2 is turned on, the output voltage is powered by the DCDC converter.

10. The constant current charging and dual power uninterruptible switching circuit for new energy vehicles according to claim 9, characterized in that: When the battery voltage and the DCDC converter voltage are close, if the product of the current collected on the sampling resistor of the constant current charging control circuit and the resistance value of the sampling resistor is less than a predetermined value, the transistor of the constant current charging control circuit does not work, and the magnitude of the output current is completely determined by the magnitude of the battery voltage. When the product of the current flowing through the sampling resistor and the resistance value of the sampling resistor is greater than the predetermined value, the voltage on the sampling resistor of the constant current charging control circuit turns on the emitter junction of the transistor, and the transistor of the constant current charging control circuit turns on and works. After the transistor of the constant current charging control circuit is turned on, the voltage stored on the junction capacitor of the gate-source voltage of the fifth MOS tube of the constant current charging control circuit is discharged through the transistor, so that the gate-source voltage of the fifth MOS tube of the constant current charging control circuit decreases. As the gate-source voltage of the fifth MOS tube of the constant current charging control circuit decreases, the equivalent resistance between the DS electrodes of the fifth MOS tube of the constant current charging control circuit increases, and the total impedance of the entire loop remains unchanged, limiting the trend of the output current exceeding the current limit value due to the increase in load, ensuring that the output current does not exceed the current limit value, and realizing constant current charging.

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