CN219351297U

CN219351297U - Charging and protecting circuit

Info

Publication number: CN219351297U
Application number: CN202222753248.8U
Authority: CN
Inventors: 周敏; 程志勇; 杨国斌
Original assignee: Mornsun Guangzhou Science and Technology Ltd
Current assignee: Mornsun Guangzhou Science and Technology Ltd
Priority date: 2022-10-19
Filing date: 2022-10-19
Publication date: 2023-07-14
Anticipated expiration: 2032-10-19

Abstract

The utility model discloses a charging and protecting circuit, which comprises a charging current sampling circuit, a battery voltage detecting circuit, a main power MOS turn-off bleeder circuit and a charging circuit, wherein the charging current sampling circuit is connected with the battery voltage detecting circuit; firstly, a single chip microcomputer is utilized to generate PWM square waves as the switching frequency of battery charging, the principle that GS of a PMOS tube is conducted under negative pressure is utilized, when the PWM square waves are high in level, an NMOS tube is driven to generate an electrifying loop for GS of the PMOS tube, the GS generates negative pressure to enable the PMOS tube to be conducted, thus input voltage stores energy for an inductor through the PMOS tube to charge the battery, otherwise, when the PWM square waves are low in level, the PMOS tube rapidly discharges GS electricity through a cut-off bleeder circuit, the PMOS is turned off, the inductor energy charges the battery through a freewheeling diode, constant-current charging is conducted through detecting battery voltage and charging current, when the battery voltage is relatively low, the duty ratio of the PWM square waves is controlled through the single chip microcomputer, when the battery voltage is close to the floating charging voltage, the duty ratio of the PWM square waves is gradually reduced until the charging is completed, and the PWM square waves are turned off.

Description

Charging and protecting circuit

Technical Field

The utility model relates to the technical field of switching power supplies, in particular to a charging and protecting circuit. The battery charging and protecting circuit method can be applied to a switching power supply which needs to charge a battery, and can realize the functions of constant current charging of the battery voltage, reverse connection prevention of the battery, floating charge protection and the like by combining a singlechip.

Background

In practical application of battery charging, most of charging circuits are charged by BUCKIC and constant current, but BUCKIC has an input power supply problem, common ICs generally only support 40V input, and when the voltage of a storage battery in many application occasions reaches more than 3 sections, floating charging voltage needs to reach more than 42V, so that the common ICs cannot support the operation; furthermore, in battery charging applications, it is often observed that the battery is charged and the fire is caused by the fire or the reverse connection of the battery, and if the battery is not protected from charging and reverse connection protection, the battery is easily damaged, and the fire is caused seriously.

Disclosure of Invention

The utility model aims to provide a charging and protecting circuit which can realize constant-current charging of a battery voltage in real time and is not limited in input voltage.

The technical scheme adopted by the utility model is as follows:

provided is a charging and protection circuit including: the charging circuit comprises a charging current sampling circuit, a main power PMOS turn-off bleeder circuit, a battery voltage detection circuit and a charging circuit;

the input end of the charging circuit is used for being connected with a power supply and PWM square wave signals generated by the singlechip, and the output end of the charging circuit is used for being connected with a battery;

the input end of the charging current sampling circuit is connected with the charging circuit, and the output end of the charging current sampling circuit is connected with the singlechip;

the charging current sampling circuit is used for collecting charging voltage of the charging circuit and transmitting the charging voltage to the singlechip, so that the singlechip controls the duty ratio of the charging PWM square wave signal according to the charging voltage;

the main power PMOS turn-off bleeder circuit is connected with the charging circuit and is used for discharging a main power tube of the charging circuit;

the input end of the battery voltage detection circuit is used for being connected with the positive end of the battery, the output end of the battery voltage detection circuit is used for being connected with the singlechip, the battery voltage detection circuit is used for sampling the battery voltage and transmitting the battery voltage to the singlechip, and the singlechip is enabled to control the duty ratio of the charging PWM square wave signal according to the voltage of the battery.

The PWM square wave generated by the singlechip is used as the switch control for charging the battery, the battery is charged after the input voltage is reduced, and meanwhile, the charging current and the charging voltage of the battery are detected, so that the effect of constant-current charging is achieved.

Preferably, the battery reverse connection preventing circuit is further arranged, the input end of the battery reverse connection preventing circuit is connected with the singlechip, the output end of the battery reverse connection preventing circuit is connected with the charging circuit, and the battery reverse connection preventing circuit is used for controlling the charging circuit to be disconnected with the battery when the singlechip judges that the battery is reversely connected according to the battery voltage;

and the output end of the charging circuit is connected with the battery through the battery reverse connection preventing circuit.

By adding the battery reverse connection preventing circuit in the charging loop, the battery reverse connection preventing circuit is not conducted at the moment when the battery voltage is negative pressure through detecting the battery voltage, so that the battery and devices in the loop are protected.

Preferably, the input end of the charging circuit comprises a first input end and a second input end, and the output end comprises a positive output end and a negative output end; the charging circuit comprises a capacitor C5, a capacitor C7, a capacitor C8, a capacitor C9, a resistor R7, a resistor R10, a resistor R16, a resistor R20, a resistor R21, a sampling resistor R22, a main power tube Q2, a MOS tube Q5, a diode D2, a voltage stabilizing tube ZD1 and an inductor L1; the positive end of the capacitor C9 is connected with the cathode of the voltage stabilizing tube ZD1, one end of the resistor R7, one end of the resistor R10 and the source electrode of the main power tube Q2, and is used as a first input end of the charging circuit for being connected with a power supply; the anode of the voltage stabilizing tube ZD1 is connected with the other end of the resistor R10, one end of the resistor R16 and the grid electrode of the main power tube Q2; the other end of the resistor R7 is connected with one end of the capacitor C5; the other end of the capacitor C5 is connected with one end of the inductor L1, the cathode of the diode D3 and the drain electrode of the main power tube Q2; the other end of the inductor L1 is connected with the positive end of the capacitor C7 and then used as the positive output end of the charging circuit to be connected with a battery through the battery reverse connection preventing circuit; the other end of the resistor R16 is connected with the drain electrode of the MOS tube Q5 and one end of the capacitor C8; the grid electrode of the MOS tube Q5 is connected with one end of a capacitor R20 and one end of a resistor R21; the other end of the resistor R20 is used as a second input end of the charging circuit and is connected with the singlechip; the negative end of the capacitor C9, the other end of the resistor R21, the source electrode of the MOS tube Q5, one end of the capacitor C8, the anode of the diode D3, the negative end of the capacitor C7 and one end of the sampling resistor R22 are grounded; the other end of the sampling resistor R22 is connected with the battery as a negative output end of the charging circuit.

The charging circuit is a similar BUCK circuit, when the PWM square wave is at a high level, the main power tube Q2 is conducted, the input voltage stores energy for the inductor and charges the battery, when the PWM square wave is at a low level, the main power tube Q2 is turned off, and the inductor L1 charges the battery through the freewheeling diode D3.

Preferably, the charging current sampling circuit comprises an amplifying unit, an RC filtering unit and a following unit; the input end of the amplifying unit is used as the input end of the charging current sampling circuit, the output end of the amplifying unit is connected with the input ends of the RC filter unit and the following unit, and the output end of the following unit is used as the output end of the charging current sampling circuit.

The voltage of the sampling resistor R22 in the charging circuit is sampled, the voltage is amplified by an operational amplifier and then transmitted to the A/D port of the singlechip, the singlechip can detect the charging current in real time, and then the duty ratio of the charging PWM square wave signal is controlled, so that the constant-current charging and the protection effects are achieved.

Preferably, the input terminal of the amplifying unit includes a positive input terminal and a negative input terminal; the amplifying unit comprises a resistor R1, a resistor R2, a resistor R5, a resistor R6, a capacitor C4 and an amplifier U1B; one end of a resistor R5 is used as a positive input end of the amplifying unit and is connected with one end of a sampling resistor R22 of the charging circuit, and one end of a resistor R2 is used as a negative input end of the amplifying unit and is connected with the other end of the sampling resistor R22 of the charging circuit; the other end of the resistor R2 is connected with one end of the resistor R1 and the negative input end of the operational amplifier U1B; the other end of the resistor R5 is connected with one end of the capacitor C4, one end of the resistor R6 and the positive input end of the operational amplifier U1B; the other end of the resistor R1 is connected with the output end of the operational amplifier U1B and then used as the output end of the amplifying unit.

Preferably, the following unit comprises a resistor R3, a capacitor you C2 and an operational amplifier U1A; one end of a resistor R3 is used as an input end of the following unit, and the other end of the resistor R3 is connected with one end of a capacitor C2 and a positive input end of an operational amplifier U1A; the inverting input end of the operational amplifier U1A is connected with the output end and then used as the output end of the following unit.

Preferably, the charging current sampling circuit further includes a first protection unit connected to the output end of the following unit, for preventing the voltage output by the following unit from being too high.

Preferably, the battery voltage detection circuit comprises a resistor R9, a resistor R14, a resistor R17, a capacitor C6 and a second protection unit; one end of the resistor R9 is used as an input end of the battery voltage detection circuit, and the other end of the resistor R14 is connected with one end of the battery voltage detection circuit; the other end of the resistor R14 is connected with one end of the capacitor C6 and one end of the resistor R17 and then used as the output end of the battery voltage detection circuit to be connected with the singlechip; the other end of the capacitor C6 and the other end of the resistor R17 are grounded.

The battery voltage is sampled to provide a judgment basis for constant current charging, floating charge protection, battery voltage reverse connection prevention and the like, and when the battery voltage is reversely connected, a battery reverse connection prevention circuit is not conducted, so that the battery does not have a loop, and the effects of protecting the battery and devices in the loop are achieved; when the battery is connected positively and the voltage is smaller, the singlechip charges the battery with constant current by controlling the PWM square wave, and when the voltage of the battery is close to the floating charge voltage, the duty ratio of the PWM square wave is gradually reduced until the charging is completed, and the PWM square wave is closed.

Preferably, the battery voltage detection circuit further includes a second protection unit connected to an output terminal of the battery voltage detection circuit, for preventing the output voltage of the battery voltage detection circuit from being too high.

Preferably, the main PMOS turn-off bleeder circuit includes a resistor R8, a resistor R11, a resistor R12, a resistor R13, a resistor R15, a resistor R18, a resistor R19, a MOS transistor Q3, a MOS transistor Q4, and a triode Q1; one end of the resistor R8 is connected with the emitter of the triode Q1 and then is used for being connected with a power supply; the other end of the resistor R8 is connected with the base electrode of the triode Q1 and one end of the resistor R12; the collector of the triode Q1 is connected with one end of a resistor R13, and the other end of the resistor R13 is connected with the grid electrode of a main power tube Q2 of the charging circuit; the other end of the resistor R12 is connected with the drain electrode of the MOS tube Q3, and the grid electrode of the MOS tube Q3 is connected with one end of the resistor R11, one end of the resistor R18 and the drain electrode of the MOS tube Q4; the other end of the resistor R11 is used for being connected with a power supply; the grid electrode of the MOS tube Q4 is connected with one end of a resistor R15 and one end of a resistor R19; the other end of the resistor R15 is connected with the input end of the charging circuit; the other end of the resistor R19, the source electrode of the MOS tube Q4, the other end of the resistor R18 and the source electrode of the MOS tube Q3 are grounded.

The main power PMOS turn-off bleeder circuit has the main characteristics that GS of a main power tube Q2 is rapidly discharged, and because the parasitic capacitance of the GS of the main power tube Q2 is relatively large, if the bleeder circuit is not added, when the PWM square wave frequency is relatively high, the GS cannot be rapidly turned off, so that the inductor L1 always stores energy, and the main power tube Q2 has damage risk; and when the PWM square wave of the singlechip is at a low level, the GS of the main power tube Q2 is not provided with a power-on loop, and the GS is rapidly discharged through the bleeder circuit, so that the main power tube Q2 achieves the turn-off effect.

Preferably, the reverse battery connection preventing circuit comprises a relay K1, a diode D4, a capacitor C10, a capacitor C11, a capacitor C12, a resistor R23, a resistor R24, a resistor R25, a resistor R26 and a MOS tube Q6; one end of the resistor R26 is used for being connected with a power supply, and the other end of the resistor R26 is connected with one end of the capacitor C11, one end of the capacitor C12, the cathode of the diode D4 and one end of the relay K1; the anode of the diode D4 is connected with the other end of the relay K1 and the drain electrode of the MOS tube Q6; the grid electrode of the MOS tube Q6 is connected with one end of a capacitor C10, one end of a resistor R25 and one end of a resistor R24; the other end of the resistor R24 is connected with one end of the resistor R23 and then used as the input end of the battery reverse connection preventing circuit to be connected with the singlechip; the other end of the resistor R23 is used for being connected with a power supply; the other end of the resistor R25, the other end of the capacitor C10, the source electrode of the MOS tube, the other end of the capacitor C11 and the other end of the capacitor C12 are grounded; the charging circuit is connected with the battery through a relay K1.

Compared with the prior art, the utility model has the beneficial effects that: according to the embodiment, the duty ratio of the PWM square wave is controlled according to the sampled battery voltage and charging current, so that the constant-current charging effect is realized; the utility model is matched with a singlechip for use, the constant-current charging current can be effectively controlled by adjusting the PWM control duty ratio, and according to the number of the battery, the utility model can be correspondingly supported by modifying the singlechip program and the main power parameter, and the control mode is simple, thereby ensuring that the input voltage is not limited and improving the applicability of the product; by adding the battery reverse connection preventing circuit in the charging loop, when the voltage of the battery is reversely connected, the relay in the charging loop is not conducted, so that the battery does not have a loop, and the effect of protecting the battery and devices in the loop is achieved.

Drawings

Fig. 1 is a schematic diagram of a charging current sampling circuit according to the present embodiment;

FIG. 2 is a schematic diagram of a battery voltage detection circuit according to the present embodiment;

FIG. 3 is a schematic diagram of the main PMOS turn-off bleeder circuit according to the present embodiment;

fig. 4 is a schematic diagram of the charging circuit according to the present embodiment;

FIG. 5 is a schematic diagram of the battery reverse connection prevention circuit according to the present embodiment;

fig. 6 is a schematic diagram of the charging and protection circuit according to the present embodiment.

Detailed Description

The drawings are for illustrative purposes only and are not to be construed as limiting the utility model, and certain components of the drawings may be omitted, enlarged or reduced in order to better illustrate the following embodiments, and are not intended to represent the actual product size; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The utility model is further described below with reference to examples.

In this embodiment, a charging and protection circuit is provided, including: the charging circuit comprises a charging current sampling circuit, a main power PMOS turn-off bleeder circuit, a battery voltage detection circuit and a charging circuit;

As a specific embodiment of the charging current sampling circuit, the charging current sampling circuit comprises an amplifying unit, an RC filtering unit and a following unit; the input end of the amplifying unit is used as the input end of the charging current sampling circuit, the output end of the amplifying unit is connected with the input ends of the RC filter unit and the following unit, and the output end of the following unit is used as the output end of the charging current sampling circuit.

As a specific embodiment of the amplifying unit, the input terminal of the amplifying unit includes a positive input terminal and a negative input terminal; the amplifying unit comprises a resistor R1, a resistor R2, a resistor R5, a resistor R6, a capacitor C4 and an amplifier U1B; one end of a resistor R5 is used as a positive input end of the amplifying unit and is connected with one end of a sampling resistor R22 of the charging circuit, and one end of a resistor R2 is used as a negative input end of the amplifying unit and is connected with the other end of the sampling resistor R22 of the charging circuit; the other end of the resistor R2 is connected with one end of the resistor R1 and the negative input end of the operational amplifier U1B; the other end of the resistor R5 is connected with one end of the capacitor C4, one end of the resistor R6 and the positive input end of the operational amplifier U1B; the other end of the resistor R1 is connected with the output end of the operational amplifier U1B and then used as the output end of the amplifying unit.

As a specific embodiment of the following unit, the following unit comprises a resistor R3, a capacitor C2 and an operational amplifier U1A; one end of a resistor R3 is used as an input end of the following unit, and the other end of the resistor R3 is connected with one end of a capacitor C2 and a positive input end of an operational amplifier U1A; the inverting input end of the operational amplifier U1A is connected with the output end and then used as the output end of the following unit.

In order to prevent the single chip microcomputer from being damaged due to the fact that the voltage output by the following unit is too high, the charging current sampling circuit further comprises a first protection unit, and the first protection unit is connected with the output end of the following unit and used for preventing the voltage output by the following unit from being too high.

Specifically, the first protection unit comprises a first diode and a second diode; the anode of the first diode is grounded, the cathode of the first diode is connected with the anode of the second diode, then connected with the output end of the following unit, and the cathode of the second diode is used for being connected with a power supply; in a specific implementation process, the power supply is 3.3V.

As shown in fig. 1, which is a schematic diagram of a charge current sampling circuit of the present embodiment, the positive input terminal vchange_cs+ and the negative input terminal vchange_cs+ of the amplifying unit sample voltages at two ends of the sampling resistor R22, the amplifying unit is formed by the operational amplifier U1B, the resistor R1, the resistor R2, the resistor R5 and the resistor R6, when the value r1=r5 and the value r2=r6 are taken, the amplification factor is equal to R1/R2, the amplified voltages form the RC filter unit through the resistor R4 and the capacitor C3 to be used as the positive input terminal of the operational amplifier U1A, and the operational amplifierThe reverse input end of the U1A is connected with the output end of the operational amplifier U1A, the first-stage following is carried out, the voltage corresponding to the obtained charging current is more accurate, the output voltage of the operational amplifier U1A is connected to the A/D port of the singlechip, the external protection first protection unit is used for protection, the singlechip is prevented from being damaged by overhigh voltage, the magnitude of the charging current can be known in real time through the operation of the A/D port of the singlechip, and the charging current

As one embodiment of the battery voltage detection circuit, the battery voltage detection circuit comprises a resistor R9, a resistor R14, a resistor R17, a capacitor C6 and a second protection unit; one end of the resistor R9 is used as an input end of the battery voltage detection circuit, and the other end of the resistor R14 is connected with one end of the battery voltage detection circuit; the other end of the resistor R14 is connected with one end of the capacitor C6 and one end of the resistor R17 and then used as the output end of the battery voltage detection circuit to be connected with the singlechip; the other end of the capacitor C6 and the other end of the resistor R17 are grounded.

In order to prevent the single chip microcomputer from being damaged due to the fact that the voltage output by the battery voltage detection circuit is too high, the battery voltage detection circuit further comprises a second protection unit which is connected with the output end of the battery voltage detection circuit and used for preventing the voltage output by the battery voltage detection circuit from being too high.

Specifically, the first protection unit comprises a third diode and a fourth diode; the anode of the third diode is grounded, the cathode of the third diode is connected with the anode of the fourth diode, and then is connected with the output end of the battery voltage detection circuit, and the cathode of the fourth diode is used for being connected with a power supply; in a specific implementation process, the power supply is 3.3V.

As shown in FIG. 2, which is a schematic diagram of a battery voltage detection circuit of the present embodiment, the circuit is relatively simple, the voltage of the positive end Vbat+ of the battery is divided by a voltage dividing circuit composed of a resistor R9, a resistor R14 and a resistor R17, the divided voltage Vbat_sense is connected to an A/D port of the SCM, a second protection unit is additionally arranged for protection, and the SCM is prevented from being damaged due to the fact that the voltage sent to the SCM exceeds the withstand voltage of the SCM, so that the battery voltage can be calculated at the moment

As a specific implementation mode of the main power PMOS turn-off bleeder circuit, the main power PMOS turn-off bleeder circuit includes a resistor R8, a resistor R11, a resistor R12, a resistor R13, a resistor R15, a resistor R18, a resistor R19, a MOS transistor Q3, a MOS transistor Q4 and a triode Q1; one end of the resistor R8 is connected with the emitter of the triode Q1 and then is used for being connected with a power supply; the other end of the resistor R8 is connected with the base electrode of the triode Q1 and one end of the resistor R12; the collector of the triode Q1 is connected with one end of a resistor R13, and the other end of the resistor R13 is connected with the grid electrode of a main power tube Q2 of the charging circuit; the other end of the resistor R12 is connected with the drain electrode of the MOS tube Q3, and the grid electrode of the MOS tube Q3 is connected with one end of the resistor R11, one end of the resistor R18 and the drain electrode of the MOS tube Q4; the other end of the resistor R11 is used for being connected with a power supply; the grid electrode of the MOS tube Q4 is connected with one end of a resistor R15 and one end of a resistor R19; the other end of the resistor R15 is connected with the input end of the charging circuit; the other end of the resistor R19, the source electrode of the MOS tube Q4, the other end of the resistor R18 and the source electrode of the MOS tube Q3 are grounded.

Specifically, the main power Q2 is a PMOS transistor, as shown in fig. 3, which is a schematic diagram of a main power PMOS turn-off bleeder circuit of the present embodiment, mainly solves the problem that the PMOS transistor Q2 cannot be turned off under the condition of higher switching frequency, when the charging current is larger, the parasitic capacitance corresponding to GS of the PMOS transistor Q2 is larger, the GS stored energy cannot be quickly released, so that the PMOS transistor Q2 cannot be quickly turned off, the energy is accumulated, the PMOS transistor Q2 is damaged, the circuit can well solve the problem, when the BCH is in a high level, the BCH is divided by the resistor R15 and the resistor R19 and then drives the MOS transistor Q4, the MOS transistor Q4 is turned on, when the BCH is in a low level, the MOS transistor Q3 is not turned on, the base current of the PNP transistor Q1 is not turned on, otherwise when the BCH is in a low level, the MOS transistor Q4 is not turned on, the GS is divided by the resistor R11 and the resistor R18 through the GS 5V, the voltage of the MOS transistor Q3 is quickly divided by the resistor R8, when the voltage of the PMOS transistor Q2 is quickly turned off, the voltage of the Q2 is quickly controlled by the resistor R8, and the base current of the Q2 is quickly turned off by the resistor Q7.v=0, and the voltage of the Q2 is quickly turned off, and the voltage of the Q2 is required to be quickly turned off, and the voltage is equal to the voltage of the Q2 is quickly turned off by the base value of the Q2.

As a specific embodiment of the charging circuit, the input end of the charging circuit comprises a first input end and a second input end, and the output end comprises a positive output end and a negative output end; the charging circuit comprises a capacitor C5, a capacitor C7, a capacitor C8, a capacitor C9, a resistor R7, a resistor R10, a resistor R16, a resistor R20, a resistor R21, a sampling resistor R22, a main power tube Q2, a MOS tube Q5, a diode D2, a voltage stabilizing tube ZD1 and an inductor L1; the positive end of the capacitor C9 is connected with the cathode of the voltage stabilizing tube ZD1, one end of the resistor R7, one end of the resistor R10 and the source electrode of the main power tube Q2, and is used as a first input end of the charging circuit for being connected with a power supply; the anode of the voltage stabilizing tube ZD1 is connected with the other end of the resistor R10, one end of the resistor R16 and the grid electrode of the main power tube Q2; the other end of the resistor R7 is connected with one end of the capacitor C5; the other end of the capacitor C5 is connected with one end of the inductor L1, the cathode of the diode D3 and the drain electrode of the main power tube Q2; the other end of the inductor L1 is connected with the positive end of the capacitor C7 and then used as the positive output end of the charging circuit to be connected with a battery through the battery reverse connection preventing circuit; the other end of the resistor R16 is connected with the drain electrode of the MOS tube Q5 and one end of the capacitor C8; the grid electrode of the MOS tube Q5 is connected with one end of a capacitor R20 and one end of a resistor R21; the other end of the resistor R20 is used as a second input end of the charging circuit and is connected with the singlechip; the negative end of the capacitor C9, the other end of the resistor R21, the source electrode of the MOS tube Q5, one end of the capacitor C8, the anode of the diode D3, the negative end of the capacitor C7 and one end of the sampling resistor R22 are grounded; the other end of the sampling resistor R22 is connected with the battery as a negative output end of the charging circuit.

As shown in fig. 4, which is a schematic diagram of a charging circuit of the present embodiment, through the charging current sampling circuit and the battery voltage detecting circuit of fig. 1 and 2, and the main PMOS turn-off bleeder circuit of fig. 3, the control principle is that firstly, the battery voltage is detected, and then the BCHPWM duty cycle is slowly released through soft start, so that the charging current is smoothly converted and slowly reaches the set constant current value; when the BCH reaches a constant current value, the MOS tube Q5 is conducted after the voltage is divided by the resistor R20 and the resistor R21, a voltage difference is generated on the resistor R10 by VIN through a loop formed by the resistor R10 and the resistor R16, the PMOS tube Q2 is damaged in order to prevent the voltage difference from being too large, a 12V voltage stabilizing tube is connected in parallel to the GS end of the PMOS tube Q2, the GS of the PMOS tube Q2 generates a negative pressure to enable the PMOS tube Q2 to be conducted, the VIN stores energy into the inductor L1 and the capacitor C7 through the PMOS tube Q2 and charges a battery, the charging current is judged through the voltage detected in the prior art, the duty ratio of the PWM square wave of the singlechip can be adjusted according to the requirements of a user, when the BCH is at a low level, the MOS tube Q5 is not conducted any more, the PMOS tube Q2 is rapidly turned off through a discharging loop of FIG. 3, and the battery is kept charged through the loop formed by the flywheel diode D3. The charging current always maintains constant current charging when the battery voltage is smaller, the duty ratio of the BCHPWM square wave is increased along with the increase of the battery voltage, the VIN is required to be larger than the battery float charging voltage, otherwise, the battery cannot reach float charging, when the battery voltage is close to the float charging voltage, the duty ratio of the PWM square wave is slowly reduced until the float charging is finished, and the PWM square wave is closed.

In order to prevent reverse connection of the battery, the embodiment further comprises a reverse connection prevention circuit, wherein the input end of the reverse connection prevention circuit is connected with the singlechip, the output end of the reverse connection prevention circuit is connected with the charging circuit, and the reverse connection prevention circuit is used for controlling the charging circuit to be disconnected with the battery when the singlechip judges that the battery is reversely connected according to the battery voltage;

As a specific embodiment of the battery reverse connection preventing circuit, the battery reverse connection preventing circuit comprises a relay K1, a diode D4, a capacitor C10, a capacitor C11, a capacitor C12, a resistor R23, a resistor R24, a resistor R25, a resistor R26 and a MOS tube Q6; one end of the resistor R26 is used for being connected with a power supply, and the other end of the resistor R26 is connected with one end of the capacitor C11, one end of the capacitor C12, the cathode of the diode D4 and one end of the relay K1; the anode of the diode D4 is connected with the other end of the relay K1 and the drain electrode of the MOS tube Q6; the grid electrode of the MOS tube Q6 is connected with one end of a capacitor C10, one end of a resistor R25 and one end of a resistor R24; the other end of the resistor R24 is connected with one end of the resistor R23 and then used as the input end of the battery reverse connection preventing circuit to be connected with the singlechip; the other end of the resistor R23 is used for being connected with a power supply; the other end of the resistor R25, the other end of the capacitor C10, the source electrode of the MOS tube, the other end of the capacitor C11 and the other end of the capacitor C12 are grounded; the charging circuit is connected with the battery through a relay K1.

As shown in fig. 5, the schematic diagram of the circuit for preventing Reverse connection of the battery in this embodiment is mainly used for solving the problem of the influence of Reverse connection of the battery, because the internal resistance of the battery is very small, once the Reverse connection occurs, if a loop passes, a very large current is generated, devices in the loop are easily damaged, and fire is caused seriously, by using fig. 2, we can detect the voltage of the battery in real time, when the battery is reversely connected, vbat_reverse is at a low level, the MOS transistor Q6 is turned off, the relay K1 has no power supply loop, the relay K1 is not turned on, and the battery has no current loop. Only when the detection of the positive voltage of the Vbat_sense is positive, that is, when the battery is normally connected, the VBAT_reverse is high level, the MOS tube Q6 is conducted after the voltage is divided by the resistor R24 and the resistor R25, the relay K1 generates a power supply loop, the relay K1 is conducted, and the VIN is operated to charge the battery.

The principle of the charge and protection circuit in this embodiment is that the charge and protection circuit is used in cooperation with a single chip microcomputer, and the charge of the battery is achieved by controlling the duty ratio of a PWM square wave, so as to achieve the application of battery charge, float charge protection, battery reverse connection prevention and the like.

It should be understood that the foregoing examples of the present utility model are merely illustrative of the present utility model and are not intended to limit the present utility model to the specific embodiments thereof. Any modification, equivalent replacement, improvement, etc. that comes within the spirit and principle of the claims of the present utility model should be included in the protection scope of the claims of the present utility model.

Claims

1. A charging and protection circuit, comprising: the charging circuit comprises a charging current sampling circuit, a main power PMOS turn-off bleeder circuit, a battery voltage detection circuit and a charging circuit;

2. The charging and protecting circuit according to claim 1, further comprising a battery reverse connection preventing circuit, wherein an input end is used for being connected with the single-chip microcomputer, an output end is connected with the charging circuit, and the battery reverse connection preventing circuit is used for controlling the charging circuit to be disconnected from the battery when the single-chip microcomputer judges that the battery is reversely connected according to the battery voltage;

3. The charging and protection circuit of claim 2, wherein the input of the charging circuit comprises a first input and a second input, and the output comprises a positive output and a negative output; the charging circuit comprises a capacitor C5, a capacitor C7, a capacitor C8, a capacitor C9, a resistor R7, a resistor R10, a resistor R16, a resistor R20, a resistor R21, a sampling resistor R22, a main power tube Q2, a MOS tube Q5, a diode D2, a voltage stabilizing tube ZD1 and an inductor L1; the positive end of the capacitor C9 is connected with the cathode of the voltage stabilizing tube ZD1, one end of the resistor R7, one end of the resistor R10 and the source electrode of the main power tube Q2, and is used as a first input end of the charging circuit for being connected with a power supply; the anode of the voltage stabilizing tube ZD1 is connected with the other end of the resistor R10, one end of the resistor R16 and the grid electrode of the main power tube Q2; the other end of the resistor R7 is connected with one end of the capacitor C5; the other end of the capacitor C5 is connected with one end of the inductor L1, the cathode of the diode D3 and the drain electrode of the main power tube Q2; the other end of the inductor L1 is connected with the positive end of the capacitor C7 and then used as the positive output end of the charging circuit to be connected with a battery through the battery reverse connection preventing circuit; the other end of the resistor R16 is connected with the drain electrode of the MOS tube Q5 and one end of the capacitor C8; the grid electrode of the MOS tube Q5 is connected with one end of a capacitor R20 and one end of a resistor R21; the other end of the resistor R20 is used as a second input end of the charging circuit and is connected with the singlechip; the negative end of the capacitor C9, the other end of the resistor R21, the source electrode of the MOS tube Q5, one end of the capacitor C8, the anode of the diode D3, the negative end of the capacitor C7 and one end of the sampling resistor R22 are grounded; the other end of the sampling resistor R22 is connected with the battery as a negative output end of the charging circuit.

4. The charging and protection circuit of claim 1, wherein the charging current sampling circuit comprises an amplifying unit, an RC filtering unit, and a follower unit; the input end of the amplifying unit is used as the input end of the charging current sampling circuit, the output end of the amplifying unit is connected with the input ends of the RC filter unit and the following unit, and the output end of the following unit is used as the output end of the charging current sampling circuit.

5. The charging and protection circuit of claim 4, wherein the input of the amplifying unit comprises a positive input and a negative input; the amplifying unit comprises a resistor R1, a resistor R2, a resistor R5, a resistor R6, a capacitor C4 and an amplifier U1B; one end of a resistor R5 is used as a positive input end of the amplifying unit and is connected with one end of a sampling resistor R22 of the charging circuit, and one end of a resistor R2 is used as a negative input end of the amplifying unit and is connected with the other end of the sampling resistor R22 of the charging circuit; the other end of the resistor R2 is connected with one end of the resistor R1 and the negative input end of the operational amplifier U1B; the other end of the resistor R5 is connected with one end of the capacitor C4, one end of the resistor R6 and the positive input end of the operational amplifier U1B; the other end of the resistor R1 is connected with the output end of the operational amplifier U1B and then used as the output end of the amplifying unit.

6. The charging and protection circuit of claim 4, wherein the follower unit comprises a resistor R3, a capacitor C2, an operational amplifier U1A; one end of a resistor R3 is used as an input end of the following unit, and the other end of the resistor R3 is connected with one end of a capacitor C2 and a positive input end of an operational amplifier U1A; the inverting input end of the operational amplifier U1A is connected with the output end and then used as the output end of the following unit.

7. The charging and protection circuit of claim 1, wherein the battery voltage detection circuit comprises a resistor R9, a resistor R14, a resistor R17, a capacitor C6, and a second protection unit; one end of the resistor R9 is used as an input end of the battery voltage detection circuit, and the other end of the resistor R14 is connected with one end of the battery voltage detection circuit; the other end of the resistor R14 is connected with one end of the capacitor C6 and one end of the resistor R17 and then used as the output end of the battery voltage detection circuit to be connected with the singlechip; the other end of the capacitor C6 and the other end of the resistor R17 are grounded.

8. The charging and protection circuit of claim 7, wherein the battery voltage detection circuit further comprises a second protection unit connected to an output terminal of the battery voltage detection circuit for preventing the output voltage of the battery voltage detection circuit from being too high.

9. The charging and protection circuit of claim 2, wherein the active PMOS shutdown bleeder circuit comprises resistor R8, resistor R11, resistor R12, resistor R13, resistor R15, resistor R18, resistor R19, MOS transistor Q3, MOS transistor Q4, and transistor Q1; one end of the resistor R8 is connected with the emitter of the triode Q1 and then is used for being connected with a power supply; the other end of the resistor R8 is connected with the base electrode of the triode Q1 and one end of the resistor R12; the collector of the triode Q1 is connected with one end of a resistor R13, and the other end of the resistor R13 is connected with the grid electrode of a main power tube Q2 of the charging circuit; the other end of the resistor R12 is connected with the drain electrode of the MOS tube Q3, and the grid electrode of the MOS tube Q3 is connected with one end of the resistor R11, one end of the resistor R18 and the drain electrode of the MOS tube Q4; the other end of the resistor R11 is used for being connected with a power supply; the grid electrode of the MOS tube Q4 is connected with one end of a resistor R15 and one end of a resistor R19; the other end of the resistor R15 is connected with the input end of the charging circuit; the other end of the resistor R19, the source electrode of the MOS tube Q4, the other end of the resistor R18 and the source electrode of the MOS tube Q3 are grounded.

10. The charging and protection circuit of claim 2, wherein the anti-reverse battery connection circuit comprises a relay K1, a diode D4, a capacitor C10, a capacitor C11, a capacitor C12, a resistor R23, a resistor R24, a resistor R25, a resistor R26, and a MOS transistor Q6; one end of the resistor R26 is used for being connected with a power supply, and the other end of the resistor R26 is connected with one end of the capacitor C11, one end of the capacitor C12, the cathode of the diode D4 and one end of the relay K1; the anode of the diode D4 is connected with the other end of the relay K1 and the drain electrode of the MOS tube Q6; the grid electrode of the MOS tube Q6 is connected with one end of a capacitor C10, one end of a resistor R25 and one end of a resistor R24; the other end of the resistor R24 is connected with one end of the resistor R23 and then used as the input end of the battery reverse connection preventing circuit to be connected with the singlechip; the other end of the resistor R23 is used for being connected with a power supply; the other end of the resistor R25, the other end of the capacitor C10, the source electrode of the MOS tube, the other end of the capacitor C11 and the other end of the capacitor C12 are grounded; the charging circuit is connected with the battery through a relay K1.