CN114520532A

CN114520532A - Charger capable of preventing current from flowing backwards

Info

Publication number: CN114520532A
Application number: CN202210204131.6A
Authority: CN
Inventors: 杨永兵
Original assignee: Shanghai Maixiang Power Technology Co ltd
Current assignee: Shanghai Maixiang Power Technology Co ltd
Priority date: 2022-03-02
Filing date: 2022-03-02
Publication date: 2022-05-20
Anticipated expiration: 2042-03-02
Also published as: CN114520532B

Abstract

The invention provides a charger capable of preventing current from flowing backwards, which comprises an electric energy conversion circuit and a protection circuit, wherein the protection circuit comprises a first switch, a second switch and a comparator, the first switch is connected with the output end of the electric energy conversion circuit in series, the input end of the comparator detects current flowing through the first switch, the output end of the comparator is connected with the control end of the second switch, when the current direction is reversed, the comparator controls the second switch to be closed, the second switch short-circuits the grid-source electrode of the first switch, and the first switch is turned off. The anti-backflow current switching circuit provided by the invention can quickly respond and quickly turn off the switch at the output end of the charger, cut off the path of the backflow current flowing to the charger and limit the size of the backflow current within an acceptable range.

Description

Charger capable of preventing current from flowing backwards

Technical Field

The invention relates to the technical field of battery charging, in particular to a charger capable of preventing reverse current.

Background

In the lithium battery charger, in order to guarantee reliable charging and protect the lithium battery, a switch is usually added at the output end of the charger to protect the lithium battery, the switch is usually controlled by an MCU, and the MCU closes the switch after detecting a fault state. However, when the lithium battery is being charged, if the charger is short-circuited, the MCU detects that the fault state can be disconnected with the lithium battery after the ms-level delay from the fault state to the closing switch, so that the lithium battery is also in the ms-level short-circuit state, and the lithium battery has very large current flowing back into the charger to damage the lithium battery, thereby affecting the service life of the lithium battery.

Disclosure of Invention

The invention provides a charger capable of preventing backward current, which can quickly respond and quickly turn off a switch at the output end of the charger, cut off a path of the backward current flowing to the charger and limit the size of the backward current within an acceptable range.

In order to achieve the purpose, the invention adopts the technical scheme that:

the utility model provides a charger of anti-flowing backwards current, includes electric energy conversion circuit, electric energy conversion circuit carries out the electric energy transform, still includes protection circuit, protection circuit includes first switch, comparator and second switch, first switch series connection in electric energy conversion circuit's output, the second switch connect in parallel in between the grid source of first switch, the comparator detects the direction of current that flows through in the first switch, works as when the direction of current is the direction of flowing backwards, the comparator control the second switch is closed, first switch turn-off.

In some embodiments, a first input terminal of the comparator is connected to the drain of the first switch, a negative supply terminal of the comparator is connected to the source of the first switch, and a second input terminal of the comparator is connected to a reference voltage.

In some embodiments, the protection circuit further comprises a sampling resistor, the sampling resistor is connected in series with the first switch, and the first input terminal of the comparator is connected with the negative power supply terminal of the comparator after passing through the sampling resistor.

In some embodiments, the first input terminal of the comparator is connected to the negative power supply terminal of the comparator after passing through the sampling resistor and the first switch.

In some embodiments, the protection circuit further comprises a third switch in anti-series with the first switch, the first switch in parallel with the gate of the first switch.

In some embodiments, the power conversion circuit includes a full-bridge rectifier module and a dc-dc converter module, the full-bridge rectifier module and the dc-dc converter module are connected in series, the dc-dc converter module includes a flyback conversion unit, the dc-dc converter module includes a transformer, a primary winding of the transformer is connected in series with a fourth switch and then connected in parallel with an output terminal of the full-bridge rectifier module, a secondary winding of the transformer is connected in parallel with a first output rectifier and filter unit, an output terminal of the first output rectifier and filter unit is connected in series with a first switch and a third switch in the protection circuit and then connected in parallel with a battery input terminal

In some embodiments, the transformer further comprises an auxiliary winding outputting an auxiliary voltage through a second rectifying and filtering unit, the auxiliary voltage supplying power to the protection circuit.

In some embodiments, the anode of the auxiliary voltage is connected to the anode of the power supply of the comparator, the cathode of the auxiliary voltage is connected to the cathode of the power supply of the comparator, and the first diode and the second diode are connected in parallel and in series in the same direction between the anode and the cathode of the power supply of the comparator.

In some embodiments, the protection circuit further comprises a shielding unit that controls the second switch to turn off for a short period of time when the first and third switches have just turned on.

When the battery is charged and the reverse current flows to the charger, the reverse current prevention switch circuit quickly responds and quickly turns off the switch at the output end of the charger, cuts off the path of the reverse current flowing to the charger and limits the magnitude of the reverse current within an acceptable range.

Drawings

Fig. 1 is a schematic diagram of a charger according to a first embodiment of the present invention.

Fig. 2 is a schematic diagram of a charger according to a second embodiment of the present invention.

Fig. 3 is a schematic diagram of a third embodiment of the charger provided by the present invention.

Fig. 4 is a schematic diagram of a fourth embodiment of the charger provided by the present invention.

Fig. 5 is a schematic diagram of a fifth embodiment of the charger provided by the present invention.

Description of the reference numerals:

10,20,30,40, 50-protection circuit, 101-switch module, 102-switch protection module;

11,21,31,41, 51-a power conversion circuit,

12,23,33,43, 53-battery.

Detailed Description

In order to make the purpose and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. It should be apparent that the described embodiments are only some of the embodiments of the present invention, and not all of them. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.

The terms "first," "second," "third," "fourth," and the like (if any) in this disclosure are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the subject matter described herein are, for example, capable of operation in other sequences than those illustrated or otherwise described herein. Further, wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

As shown in fig. 1, the charger of the present invention includes a power conversion circuit 11 and a protection circuit 10, an output terminal of the power conversion circuit 11 is connected in series with the protection circuit 10 and then connected in parallel with a battery 12, the protection circuit 10 includes a switch S1, the switch S1 is connected in series with the output terminal of the power conversion circuit 11, when the power conversion circuit 11 charges the battery 12, the switch S1 is turned on, and when the battery 12 outputs a backward current, the switch S1 is turned off. The protection circuit 10 further comprises a comparator U1, the comparator U1 samples a current Io at an output end of the electric energy conversion circuit 11, and the current Io is output from the power supplyWhen the battery 12 flows to the power conversion circuit 11, the comparator U1 outputs a high level to the control end of the switch S3, the switch S3 is turned on, the switch S3 is connected in parallel with the gate-source of the switch S1, the switch S3 is turned on, the switch S1 is turned off reliably, and the connection between the battery 12 and the power conversion circuit 11 is cut off. As shown in fig. 1, the positive input terminal of the comparator U1 is connected to one terminal of the switch S1, the negative input terminal of the comparator U1 receives a reference voltage Vref, the reference voltage Vref is referenced to the voltage at the source terminal of the switch S1, and the negative power supply terminal of the comparator is connected to the terminal P1. In one embodiment, referring to fig. 5, the winding N2 of the reference voltage Vref is obtained after rectification filtering and linear voltage stabilization. The comparator U1 collects the voltage of the terminal P2 in real time, and the voltage of the terminal P2 is the voltage of the terminal P1 as the reference ground, i.e. the voltage V between the drain and the source of the switch S1 _b＝I_o*R_dsWherein, I_oFor a charging current flowing from terminal P1 to terminal P2, R_dsIs the on-resistance of switch S1, voltage U_bIf the voltage is negative, the comparator U1 outputs low level, and the switch S3 is turned off; when the current Io flows from the terminal P2 to the terminal P1, the voltage U_bPositive, the comparator U1 outputs a high and the switch S3 is conductive.

The output of the power conversion circuit 11 is connected in parallel with the battery 12 via a capacitor C3 as shown in fig. 1.

The protection circuit 10 further includes a resistor R1, and the resistor R1 is connected in parallel between the gate and the source of the switch S1, and is used for discharging between the gate and the source of the switch S1 and reducing the impedance between the gate and the source, so as to prevent false turn-on.

The protection circuit 10 further includes a diode D1, the diode D1 is connected in series with the output end of the comparator U1, when the comparator U1 outputs a high level, the diode D1 is turned on and charges a capacitor C1, when the voltage of the capacitor C1 reaches the driving turn-on voltage of the switch S3, the switch S3 is turned on, the capacitor C1 is connected in parallel with the gate-source electrode of the switch S3, the resistor R3 is connected in parallel with the capacitor C1, and when the diode D1 is turned off, the capacitor C1 discharges the resistor R3.

In the embodiment shown in fig. 1, the on-resistance of the switch S1 is used as the detection resistance of the backward current, please refer to fig. 2 again, and the embodiment shown in fig. 1 In a different embodiment, the resistor Rs is connected in series with the switch S1, and the comparator U1 detects the voltage across the switch S1 and the resistor Rs, i.e., U_b＝I_o*(R_ds+ Rs) to improve the control accuracy of the circuit.

Referring to fig. 4 again, unlike the embodiment shown in fig. 1, the comparator U1 detects the voltage across the resistor Rs, i.e., U_b＝I_o*Rs。

As shown in fig. 3, in this embodiment, the switch S1 and the switch S2 are connected in series, and the switch S1 and the switch S2 are turned on simultaneously when the power conversion circuit 31 charges the battery 32. The switch S1 prevents the battery current from flowing backward to the power conversion circuit for output, and the switch S2 prevents the power conversion circuit from charging the battery after the battery is reversely connected.

In the present invention, FIG. 1 shows a backward flow of current I_dgCan be expressed by the following expression (1), fig. 2 and 3 backward flow current I_dgExpressed by the following expression (2), by setting the appropriate Vref, the backward flow current I can be limited_dgThe value of (c).

I_dg＝V_ref/R_ds (1)

I_dg＝V_ref/(R_ds+R_s) (2)

The

protection circuits

10, 20, 30 and 40 provided by the invention allow the current Io to flow from the end P4 to the end P2, when the current Io flows from the end P2 to the end P4, the backward flow current is generated, and the allowance is smaller than the backward flow current I_dgWhen the current Io is a backward flow current and is larger than I_dgThe

protection circuits

10, 20, 30 and 40 will quickly control the switches S1 and S2 to turn off. The protection circuit provided by the present invention is not limited to the circuit structures shown in fig. 1, 2, 3 and 4, and any similar circuit structure or operation principle to that shown in fig. 1, 2, 3 and 4 is within the protection scope of the present invention, such as replacing the switches S1, S2 and S3 in the present invention with other switches to make corresponding changes to the circuit structure, or exchanging the signals of the positive and negative terminals of the comparator U1 to make corresponding changes to other switches or circuits, and the basic operation principle is still similar to that of the present invention.

As shown in fig. 5, the present invention provides a charger, in which the power conversion circuit 51 includes a full-bridge rectification module 511 and a dc-dc conversion module 512, and the full-bridge rectification module 511 and the dc-dc conversion module 512 are connected in series. The full-bridge rectification module 511 comprises diodes D4-D7, the dc-dc conversion module 512 comprises a flyback conversion unit, the dc-dc conversion module 512 comprises a transformer T1, a primary winding of the transformer T1 is connected in series with a switch S4 and then connected in parallel with an output end of the full-bridge rectification module 511, a secondary winding N1 of the transformer T1 is connected in parallel with an output rectification filter unit 5121, an output end of the output rectification filter unit 5121 is connected in series with a switch S1 and a switch S2 in the protection circuit 50 and then connected in parallel with an input end of the battery 52, wherein the switch S1 and the switch S2 are connected in series in an opposite direction. The transformer T1 further includes an auxiliary winding N2, and the auxiliary winding N2 outputs an auxiliary voltage Vs through the rectifying and filtering unit 5122, and the auxiliary voltage Vs supplies power to the protection circuit 50.

When the battery 52 needs to be charged, the MCU control module 5021 first detects whether a fault occurs in the charger, such as whether the output capacitor C3 is short-circuited, and if there is no fault, the MCU control module 5021 outputs a high level to the optocoupler U2 to control the switches S1 and S2 to be turned on, and the current input from the charger to the battery 52 flows from the terminal P4 to the terminal P2. The comparator U1 detects that the voltage between the drain and the source of the switch S1 is negative, the comparator U1 outputs low level, and the switch S3 is turned off. If a fault occurs, the battery 42 is prevented from generating backward flow current, firstly, the comparator U1 detects that the voltage between the drain and the source of the switch S1 is positive, the comparator U1 outputs high level, the switch S3 is closed, the gate and the source of the switch S1 are short-circuited, the switch S1 is reliably turned off, secondly, the MCU control module 5021 outputs low level through operation after detecting the fault, and the switch S1 and the switch S2 are also controlled to be turned off.

The output positive electrode of the auxiliary power supply module 4122 is connected with the power supply positive electrode of the comparator U1, the output negative electrode of the auxiliary power supply module 4122 is connected with the power supply negative electrode of the comparator U1, diodes D2 and D3 which are connected in series in the same direction are connected between the power supply positive electrode and the power supply negative electrode of the comparator U1 in parallel, and the positive input end of the comparator U1 detects the backward flow current through a resistor R2. And a resistor R4 is connected in parallel between the output end of the comparator U1 and the power supply anode thereof, and the resistor R4 is used as a pull-up resistor. The output positive pole of the auxiliary power supply module 5122 is connected with one end of the output side of the optocoupler U2, the other end of the output side is connected with the gates of the switches S1 and S2, and the input side of the optocoupler U2 is connected with the output end of the MCU control module. The output cathode of the auxiliary power module 5122 is connected to the series midpoint of the switches S1 and S2.

We can also connect a shielding unit 5011 at the gate of the switch S3, including a capacitor C5, a switch S5 and a resistor R5, where one end of the capacitor C5 is connected to the output end of the optocoupler U2, and the other end is connected to the gate of the switch S5, the resistor R7 is connected in parallel with the gate source of the switch S5, when it is necessary to charge the battery 52, the optocoupler U2 outputs a high level, the switches S1 and S2 are driven to conduct, the optocoupler U2 outputs a short period of high level during which current flows in the capacitor C5, a voltage drop is generated across the resistor R7 to turn on the switch S5, since the optocoupler U2 outputs a direct current, after a short period, the blocking effect of the capacitor C5 is zero, the current flowing through the resistor R7 is zero, then the switch S5 is turned off, then the switch S1 is turned on for a short period, the shielding unit 5011 works to pull down the gate voltage of the switch S3 for a short period, and control the switch S3 to be turned off, so as to prevent the switch S6855 and S6474 from being turned off by mistake, after a short period of time, the shielding unit 5011 stops operating.

When the battery is charged and the backward current flows to the charger, the backward current prevention switching circuit quickly responds and quickly turns off the switch at the output end of the charger, so that the path of the backward current flowing to the charger is cut off, and the magnitude of the backward current is limited within an acceptable range.

Although the present invention has been described with reference to particular embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. The utility model provides a charger of anti-flowing backwards current, includes electric energy converting circuit, electric energy converting circuit carries out the electric energy transform, its characterized in that still includes protection circuit, protection circuit includes first switch, comparator and second switch, first switch series connection in electric energy converting circuit's output, the second switch connect in parallel in between the grid source of first switch, the comparator detects the current direction that flows in first switch, works as when the current direction is the backward flow current direction, comparator control the second switch is closed, first switch turn-off.

2. The charger of claim 1, wherein a first input terminal of the comparator is connected to a drain of the first switch, a negative power supply terminal of the comparator is connected to a source of the first switch, and a second input terminal of the comparator is connected to a reference voltage.

3. The charger according to claim 2, wherein the protection circuit further comprises a sampling resistor, the sampling resistor is connected in series with the first switch, and a first input terminal of the comparator is connected to a negative power supply terminal of the comparator after passing through the sampling resistor.

4. The charger of claim 3, wherein the first input terminal of the comparator is connected to the negative power supply terminal of the comparator after passing through the sampling resistor and the first switch.

5. The reverse current prevention charger according to claim 4, wherein the protection circuit further comprises a third switch connected in reverse series with the first switch, and the first switch is connected in parallel with a gate of the first switch.

6. The charger of claim 1, wherein the power conversion circuit comprises a full-bridge rectification module and a dc-dc conversion module, the full-bridge rectification module and the dc-dc conversion module are connected in series, the dc-dc conversion module comprises a flyback conversion unit, the dc-dc conversion module comprises a transformer, a primary winding of the transformer is connected in series with a fourth switch and then connected in parallel with an output terminal of the full-bridge rectification module, a secondary winding of the transformer is connected in parallel with a first output rectification filter unit, and an output terminal of the first output rectification filter unit is connected in series with a first switch and a third switch of the protection circuit and then connected in parallel with an input terminal of the battery.

7. The charger of claim 6, wherein the transformer further comprises an auxiliary winding, the auxiliary winding outputs an auxiliary voltage through the second rectifying and filtering unit, and the auxiliary voltage supplies power to the protection circuit.

8. The reverse current prevention charger according to claim 7, wherein the positive pole of the auxiliary voltage is connected to the positive power supply pole of the comparator, the negative pole of the auxiliary voltage is connected to the negative power supply pole of the comparator, and the first diode and the second diode are connected in series in the same direction between the positive power supply pole and the negative power supply pole of the comparator.

9. The reverse current prevention charger according to claim 8, wherein the protection circuit further comprises a shielding unit, and the shielding unit controls the second switch to be turned off during a short period of time when the first and third switches are just turned on.