CN111884287A

CN111884287A - Battery charging circuit

Info

Publication number: CN111884287A
Application number: CN202010711595.7A
Authority: CN
Inventors: 罗康伟
Original assignee: Shenzhen H&T Intelligent Control Co Ltd
Current assignee: Shenzhen H&T Intelligent Control Co Ltd
Priority date: 2020-07-22
Filing date: 2020-07-22
Publication date: 2020-11-03
Anticipated expiration: 2040-07-22
Also published as: CN111884287B

Abstract

The embodiment of the invention relates to the technical field of battery charging control, and discloses a battery charging circuit, which comprises: the device comprises a voltage comparator circuit, a button switch, a discharge circuit, a pulse generator circuit and a constant current source charging circuit; the positive pole of the rechargeable battery is connected with the voltage comparator circuit, the discharging circuit, the pulse generator circuit and the constant current source charging circuit, and the negative pole of the rechargeable battery is grounded; one end of the button switch is connected with the voltage comparator circuit, the other end of the button switch is grounded, the button switch is triggered, the voltage comparator circuit outputs a low level, the discharge circuit controls the rechargeable battery to discharge to a first voltage, the voltage comparator circuit outputs a high level, the pulse generator circuit is controlled to output square wave pulses, and the constant current source charging circuit is controlled to charge the rechargeable battery according to the square wave pulses until the charging is completed. Through the mode, the embodiment of the invention can realize the functions of battery discharging, charging, indicating, trickle charging and overvoltage protection, has low cost, is practical and reliable, and has very high practical application value.

Description

Battery charging circuit

Technical Field

The embodiment of the invention relates to the technical field of battery charging control, in particular to a battery charging circuit.

Background

The cost of the battery charging circuit is a key factor limiting the use of the nickel cadmium battery, but in practical applications, many of the charging schemes for the nickel cadmium battery are designed based on integrated circuits, all the technologies are mastered in chip manufacturers, and general companies have difficulty in reducing the design and production costs through peripheral devices. A reliable, practical and low cost charging scheme for nickel cadmium batteries is necessary.

At present, a plurality of nickel-cadmium battery charging schemes are designed based on a special battery charging scheme of an integrated circuit MAX712 chip, or the design of the actual battery charging process is realized through a single chip microcomputer and some peripheral devices.

Disclosure of Invention

In view of the above, embodiments of the present invention provide a battery charging circuit that overcomes or at least partially solves the above-mentioned problems.

According to an aspect of an embodiment of the present invention, there is provided a battery charging circuit including: the device comprises a voltage comparator circuit, a button switch, a discharge circuit connected with the voltage comparator circuit, a pulse generator circuit and a constant current source charging circuit connected with the pulse generator circuit; the positive electrode of the rechargeable battery is connected with the voltage comparator circuit, the discharge circuit, the pulse generator circuit and the constant current source charging circuit, and the negative electrode of the rechargeable battery is grounded; one end of the button switch is grounded, the other end of the button switch is connected with a voltage comparator circuit, when the button switch is triggered, the voltage comparator circuit outputs a low level, the rechargeable battery is controlled to discharge to a first voltage through the discharge circuit, the voltage comparator circuit is controlled to output a high level according to the first voltage, the pulse generator circuit is controlled to output square wave pulses, and the constant current source charging circuit is controlled to charge the rechargeable battery according to the square wave pulses until the charging is completed.

In an alternative form, the voltage comparator circuit includes a first comparator, an input circuit, a second resistor, and a first diode; the non-inverting input end of the first comparator is connected with the anode of the first diode through the discharge circuit, the cathode of the first diode is connected with one end of the button switch, the cathode of the first diode is further connected with the output end of the first comparator through the second resistor, the inverting input end of the first comparator is connected with the anode of the rechargeable battery, and the output end of the first comparator serves as the output end of the voltage comparator circuit and is connected with the discharge circuit and the pulse generator circuit.

In an alternative mode, the input circuit comprises a first variable resistor, a second variable resistor, a first resistor and a first capacitor; one end of the first capacitor is connected with a power supply voltage, the other end of the first capacitor is connected with the non-inverting input end of the first comparator, the first end of the first variable resistor is connected with the non-inverting input end of the first comparator through a first resistor and is also connected with the discharge circuit, the second end of the first variable resistor is connected with the power supply voltage, and the sliding end of the first variable resistor is connected with the pulse generator circuit; the first end of the second variable resistor is connected with the non-inverting input end of the first comparator, and the second end and the sliding end of the second variable resistor are grounded.

In an optional manner, the battery charging circuit further includes a power-up indication circuit, and the power-up indication circuit includes: the anode of the first light-emitting diode is connected with the power supply voltage through the third resistor, the cathode of the first light-emitting diode is grounded, and the anode of the first light-emitting diode is further connected with the voltage comparator circuit.

In an alternative form, the discharge circuit includes: the LED driving circuit comprises a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a first triode, a second light emitting diode, a second comparator, a second diode, a third diode and a third triode; the first end of the first triode is connected with the output end of the voltage comparator circuit, the second end of the first triode is connected with the first end of the second triode, the third end of the first triode is connected with the cathode of the second light-emitting diode through the fourth resistor, the anode of the second light-emitting diode is connected with the power supply voltage, the second end of the second triode is connected with the inverting input end of the second comparator through the fifth resistor, the inverting input end of the second comparator is also connected with the anode of the rechargeable battery, the third end of the second triode is grounded, the non-inverting input end of the second comparator is connected with the voltage comparator circuit, the output end of the second comparator is connected with the anode of the second diode, and the cathode of the second diode is connected with the output end of the voltage comparator circuit and the cathode of the third diode, the anode of the third diode is connected with the constant current source charging circuit; the first end of the third triode is connected with the output end of the voltage comparator circuit through the sixth resistor, the second end of the third triode is connected with the pulse generator circuit through the seventh resistor, and the third end of the third triode is connected with the output end of the pulse generator circuit.

In an optional mode, the battery charging circuit further comprises a differentiating circuit, wherein the differentiating circuit comprises an eighth resistor, a ninth resistor and a second capacitor; one end of the eighth resistor is connected with the output end of the voltage comparator circuit, the other end of the eighth resistor is connected with the discharge circuit and one end of the second capacitor through the ninth resistor, the other end of the second capacitor is connected with the pulse generator circuit, and the other end of the eighth resistor is connected with the discharge circuit.

In an alternative form, the pulse generator circuit includes: a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a third comparator, a third capacitor, and a fourth diode; the non-inverting input end of the third comparator is connected with the anode of the rechargeable battery, the non-inverting input end of the third comparator is grounded through the eleventh resistor and is connected with the output end of the third comparator through the twelfth resistor, the inverting input end of the third comparator is grounded through the third capacitor and is connected with the output end of the third comparator through the tenth resistor and is also connected with the anode of the fourth diode through the thirteenth resistor, and the cathode of the fourth diode is connected with the output end of the third comparator and the differential circuit.

In an alternative form, the constant current source charging circuit includes: the fourth triode, the fifth triode, the sixth triode, the fourteenth resistor, the fifteenth resistor, the sixteenth resistor, the seventeenth resistor and the third light-emitting diode; the first end of the fourth triode is connected with the cathode of the third light emitting diode, the anode of the third light emitting diode is connected with the power supply voltage, the second end of the fourth triode is connected with the anode of the rechargeable battery, the second end of the fourth triode is also connected with the first end of the fifth triode through the fifteenth resistor and is connected with the first end of the sixth triode through the sixteenth resistor; the first end of the fifth triode is further connected with the discharge circuit, the second end of the sixth triode and the output end of the pulse generator circuit, the second end of the fifth triode is connected with the first end of the fourth triode, the first end of the sixth triode is grounded through the seventeenth resistor, and the third end of the fifth triode and the third end of the sixth triode are grounded.

In an optional manner, the battery charging circuit further includes a fifth diode, an anode of the fifth diode is connected to the constant current source charging circuit, and a cathode of the fifth diode is connected to the output terminal of the pulse generator circuit.

In an optional manner, the battery charging circuit further includes an overvoltage detection circuit, the overvoltage detection circuit including: an eighteenth resistor, a fourth comparator, a sixth diode, and a seventh diode; the non-inverting input end of the fourth comparator is connected with the voltage comparator circuit and the anode of the sixth diode, the inverting input end of the fourth comparator is connected with the anode of the rechargeable battery, the cathode of the sixth diode is connected with the output end of the fourth comparator and the cathode of the seventh diode through the eighteenth resistor, and the anode of the seventh diode is the output end of the overvoltage detection circuit and is connected with the input end of the pulse generator circuit.

The battery charging circuit of the embodiment of the invention comprises: the device comprises a voltage comparator circuit, a button switch, a discharge circuit connected with the voltage comparator circuit, a pulse generator circuit and a constant current source charging circuit connected with the pulse generator circuit; the positive electrode of the rechargeable battery is connected with the voltage comparator circuit, the discharge circuit, the pulse generator circuit and the constant current source charging circuit, and the negative electrode of the rechargeable battery is grounded; one end of the button switch is grounded, the other end of the button switch is connected with a voltage comparator circuit, when the button switch is triggered, the voltage comparator circuit outputs a low level to control the discharging circuit to discharge the rechargeable battery to a first voltage, the voltage comparator circuit is controlled to output a high level according to the first voltage to control the pulse generator circuit to output square wave pulses, the constant current source charging circuit is controlled to charge the rechargeable battery according to the square wave pulses until the charging is finished, and the functions of battery discharging, charging, indicating, trickle charging and overvoltage protection are realized by applying a common operational amplifier and some simple peripheral circuits, so that the button switch is low in cost, practical and reliable and has high practical application value.

The foregoing description is only an overview of the technical solutions of the embodiments of the present invention, and the embodiments of the present invention can be implemented according to the content of the description in order to make the technical means of the embodiments of the present invention more clearly understood, and the detailed description of the present invention is provided below in order to make the foregoing and other objects, features, and advantages of the embodiments of the present invention more clearly understandable.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

FIG. 1 illustrates a block schematic diagram of a battery charging circuit provided by an embodiment of the present invention;

fig. 2 shows a schematic circuit diagram of a battery charging circuit according to an embodiment of the present invention.

Detailed Description

Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

Fig. 1 shows a block schematic diagram of a battery charging circuit according to an embodiment of the present invention, and as shown in fig. 1, a battery charging circuit 10 includes: a voltage comparator circuit 11, a push-button switch SA, a discharge circuit 12 connected to the voltage comparator circuit 11, a pulse generator circuit 13, and a constant current source charging circuit 14 connected to the pulse generator circuit 13; the positive electrode of the rechargeable battery is connected with the voltage comparator circuit 11, the discharge circuit 12, the pulse generator circuit 13 and the constant current source charging circuit 14, and the negative electrode of the rechargeable battery is grounded to GND; one end of the button switch SA is grounded, the other end of the button switch SA is connected with the voltage comparator circuit 11, when the button switch SA is triggered, the voltage comparator circuit 11 outputs a low level, the discharge circuit 12 controls the rechargeable battery to discharge to a first voltage VCC1, the voltage comparator circuit 11 is controlled to output a high level according to the first voltage VCC1, the pulse generator circuit 13 is controlled to output square wave pulses, and the constant current source charging circuit 14 is controlled to charge the rechargeable battery according to the square wave pulses until the charging is completed. The rechargeable battery includes a first rechargeable battery BAT1 and a second rechargeable battery BAT2 connected in parallel, although the number of rechargeable batteries is not limited to this, and may be one or more.

In the embodiment of the present invention, as shown in fig. 2, the voltage comparator circuit 11 includes a first comparator U1, an input circuit 110, a second resistor R2, and a first diode D1. The non-inverting input terminal of the first comparator U1 is connected to the input circuit 110 and the anode of the first diode D1, the cathode of the first diode D1 is connected to one end of the push button switch SA, the cathode of the first diode D1 is further connected to the output terminal of the first comparator U1 through the second resistor R2, the inverting input terminal of the first comparator U1 is connected to the positive electrode of the rechargeable battery, and the output terminal of the first comparator U1 is used as the output terminal of the voltage comparator circuit 11 and is connected to the discharge circuit 12 and the pulse generator circuit 13. The input circuit 110 provides a first reference voltage to the non-inverting input of the first comparator U1. The voltage comparator circuit 11 is used to discharge the voltage of the rechargeable battery to a first voltage VCC1 before charging the rechargeable battery, and the first reference voltage is slightly higher than the first voltage VCC1 and smaller than the second voltage VCC 2.

The input circuit 110 includes a first variable resistor RP1, a second variable resistor RP2, a first resistor R1, and a first capacitor C1. One end of the first capacitor C1 is connected to a power supply voltage VCC, the other end is connected to a non-inverting input terminal of the first comparator U1, a first end of the first variable resistor RP1 is connected to the non-inverting input terminal of the first comparator U1 through a first resistor R1, and is also connected to the discharge circuit 12, a second end of the first variable resistor RP1 is used as an input terminal of the voltage comparator circuit 11 and is connected to the power supply voltage VCC, and a sliding end of the first variable resistor RP1 is connected to the pulse generator circuit 13; the first end of the second variable resistor RP2 is connected with the non-inverting input end of the first comparator U1, and the second end and the sliding end of the second variable resistor RP2 are grounded. The input circuit 110 is used to provide corresponding reference voltages to the first comparator U1, the discharge circuit 12, and the pulse generator circuit 13.

The battery charging circuit 10 further comprises a power-up indication circuit 15, said power-up indication circuit 15 comprising: third resistance R3 and first emitting diode LED1, first emitting diode LED 1's positive pole passes through third resistance R3 connects the mains voltage VCC, first emitting diode LED 1's negative pole ground connection GND, first emitting diode LED 1's positive pole still with voltage comparator circuit 11 connects, and first voltage comparator circuit 11's input passes through promptly third resistance R3 is connected mains voltage VCC. The power-up indication circuit 15 is used to light the first LED1 when the battery charging circuit 10 is powered up, indicating that the battery charging circuit 10 is operating properly.

The discharge circuit 12 includes: a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a first triode Q1, a second triode Q2, a second light emitting diode LED2, a second comparator U2, a second diode D2, a third diode D3 and a third triode Q3; the first end of the first triode Q1 is connected to the output end of the voltage comparator circuit 11, the second end of the first triode Q1 is connected to the first end of the second triode Q2, the third end of the first triode Q1 is connected to the cathode of the second light emitting diode LED2 through the fourth resistor R4, the anode of the second light emitting diode LED2 is connected to the power supply voltage VCC, the second end of the second triode Q2 is connected to the inverting input end of the second comparator U2 through the fifth resistor R5, the inverting input end of the second comparator U2 is further connected to the positive electrode of the rechargeable battery, the third end of the second triode Q2 is grounded, and the non-inverting input end of the second comparator U2 is connected to the voltage comparator circuit 11. Specifically, the non-inverting input terminal of the second comparator U2 is connected to the first terminal of the first variable resistor RP1 in the voltage comparator circuit 11, and is used for obtaining a corresponding second reference voltage from the input circuit 110, where the second reference voltage is slightly smaller than the second voltage VCC 2. The output terminal of the second comparator U2 is connected to the anode of the second diode D2, the cathode of the second diode D2 is connected to the output terminal of the voltage comparator circuit 11 and the cathode of the third diode D3, and the anode of the third diode D3 is connected to the constant current source charging circuit 14; a first end of the third transistor Q3 is connected to an output end of the voltage comparator circuit 11, i.e., an output end of the first comparator U1, through the sixth resistor R6, a second end of the third transistor Q3 is connected to the pulse generator circuit 13, through the seventh resistor R7, and a third end of the third transistor Q3 is connected to an output end of the pulse generator circuit 13.

The battery charging circuit 10 further comprises a differentiating circuit 16, wherein the differentiating circuit 16 comprises an eighth resistor R8, a ninth resistor R9 and a second capacitor C2; one end of the eighth resistor R8 is connected to the output end of the voltage comparator circuit 11, the other end of the eighth resistor R8 is connected to the discharge circuit 12 and one end of the second capacitor C2 through the ninth resistor R9, the other end of the second capacitor C2 is connected to the pulse generator circuit 13, and the other end of the eighth resistor R8 is further connected to the discharge circuit 12. Specifically, one end of an eighth resistor R8 is connected to the output end of the first comparator U1, and the other end of the eighth resistor R8 is connected to the first end of the first transistor Q1 through the ninth resistor R9, and is connected to the cathode of the second diode D2 and the cathode of the third diode D3. The voltage comparator circuit 11 makes the first transistor Q1 and the second transistor Q2 in the discharging circuit 12 conduct for a short time through the differentiating circuit 16 to discharge the rechargeable battery before charging. While the voltage comparator circuit 11 also provides an output frequency control signal to the pulse generator circuit 13 via a differentiating circuit 16.

The pulse generator circuit 13 includes: a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a third comparator U3, a third capacitor C3, and a fourth diode D4; the non-inverting input terminal of the third comparator U3 is connected to the positive electrode of the rechargeable battery, the non-inverting input terminal of the third comparator U3 is further connected to the GND through the eleventh resistor R11 and to the output terminal of the third comparator U3 through the twelfth resistor R12, the inverting input terminal of the third comparator U3 is connected to the GND through the third capacitor C3 and to the output terminal of the third comparator U3 through the tenth resistor R10, and is also connected to the anode of the fourth diode D4 through the thirteenth resistor R13, and the cathode of the fourth diode D4 is connected to the output terminal of the third comparator U3 and the differentiating circuit 16. The inverting input terminal of the third comparator U3 is further connected to the second terminal of the third transistor through a seventh resistor R7. The pulse generator circuit 13 is used to supply square wave pulses to the constant current source charging circuit 13 to control the charging of the rechargeable battery. The pulse generator circuit 13 may also use other square wave pulse generators, such as a square wave pulse generator configured based on a 555 timer, and the like, which is not limited herein.

The constant current source charging circuit 14 includes: a fourth triode Q4, a fifth triode Q5, a sixth triode Q6, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17 and a third light emitting diode LED 3; a first end of the fourth triode Q4 is connected to a cathode of the third light emitting diode LED3, an anode of the third light emitting diode LED3 is connected to the power supply voltage VCC, a second end of the fourth triode Q4 is connected to an anode of the rechargeable battery, a second end of the fourth triode Q4 is further connected to a first end of the fifth triode Q5 through the fifteenth resistor R15, and is connected to a first end of the sixth triode Q6 through the sixteenth resistor R16; the first end of the fifth triode Q5 is further connected to the discharge circuit 12, the second end of the sixth triode Q6, and the output end of the pulse generator circuit 13, the second end of the fifth triode Q5 is connected to the first end of the fourth triode Q4, the first end of the sixth triode Q6 is further grounded to GND via the seventeenth resistor R17, and the third end of the fifth triode Q5 and the third end of the sixth triode Q6 are grounded to GND. The constant current source charging circuit 14 is used to supply a charging current required for charging to the rechargeable battery. The constant current source charging circuit 14 may be a constant current source circuit of other structures, which is not limited herein.

The first triode Q1, the third triode Q3 and the fourth triode Q4 are PNP triodes, the second triode Q2, the fifth triode Q5 and the sixth triode Q6 are NPN triodes, the first end is a base, the second end is a collector, and the third end is an emitter.

The battery charging circuit 10 further includes a fifth diode D5, an anode of the fifth diode D5 is connected to the constant current source charging circuit, and particularly to the first terminal of the fifth transistor Q5, and a cathode of the fifth diode D5 is connected to the output terminal of the pulse generator circuit 13, i.e., the output terminal of the third comparator U3.

The battery charging circuit 10 further comprises an overvoltage detection circuit 17, said overvoltage detection circuit 17 comprising: an eighteenth resistor R18, a fourth comparator U4, a sixth diode D6, and a seventh diode D7; a non-inverting input terminal of the fourth comparator U4 is connected to the voltage comparator circuit 11 and an anode of the sixth diode D6, an inverting input terminal of the fourth comparator U4 is connected to an anode of the rechargeable battery, a cathode of the sixth diode D6 is connected to an output terminal of the fourth comparator U4 and a cathode of the seventh diode D7 through the eighteenth resistor R18, and an anode of the seventh diode D7 is an output terminal of the overvoltage detection circuit 17 and is connected to an input terminal of the pulse generator circuit 13, that is, a non-inverting input terminal of the third comparator U3. Specifically, the non-inverting input terminal of the fourth comparator U4 and the sliding terminal of the first variable resistor RP1 are configured to obtain a third reference voltage from the input circuit 110, where the third reference voltage is slightly smaller than the third voltage VCC 3.

The first comparator U1, the second comparator U2, the third comparator U3, and the fourth comparator U4 in the embodiment of the present invention employ operational amplifiers.

The principle of the battery charging circuit 10 of the embodiment of the present invention is explained below:

after the power is turned on, the power voltage VCC supplies current to the first LED1 through the third resistor R3, and the first LED1 lights up, indicating that the battery charging circuit 10 is operating normally. After passing through the third resistor R3, the power supply voltage VCC is divided by the first variable resistor RP1, the first resistor R1 and the second variable resistor RP2 and then provides a voltage to the non-inverting input terminal of the first comparator U1, at this time, the voltage at the inverting input terminal of the first comparator U1 is lower than the voltage at the non-inverting input terminal, the first comparator U1 outputs a high level, and the battery charging circuit 10 enters a working state.

The button switch SA is touched, i.e. released after being pressed, so that the button switch SA is closed in a short time. When the push switch SA is closed, the cathode of the first diode D1 is connected to ground through the push switch SA, triggering the battery charging circuit 10 into a discharged state. At this time, the voltage at the non-inverting input terminal of the first comparator U1 is at a low level, the voltage at the inverting input terminal of the first comparator U1 is higher than the voltage at the non-inverting input terminal, and the output terminal of the first comparator U1 outputs a low level signal. The low level signal is divided into two paths, one path provides an output frequency control signal to a pulse generator circuit 13 composed of a third comparator U3 through a differential circuit 16 composed of an eighth resistor R8, a ninth resistor R9 and a second capacitor C2, and the other path provides a low level signal to the base of a first triode Q1 through an eighth resistor R8 and a ninth resistor R9, so that the first triode Q1 is conducted. The power supply voltage VCC supplies a turn-on voltage to the base of the second transistor Q2 through the second light emitting diode LED2, the fourth resistor R4, and the turned-on first transistor Q1, so that the second transistor Q2 is turned on. During discharging, one of the first rechargeable battery BAT1 and the second rechargeable battery BAT2 discharges through the first resistor R5 and the second triode Q2, and the other discharges through the fifteenth resistor R15, the third diode D3, the ninth resistor R9, the first triode Q1 and the second triode Q2. At this time, the second light emitting diode LED2 lights up to indicate discharge, and the third light emitting diode LED3 for indicating charge turns off.

When the rechargeable battery is discharged to the first voltage VCC1, the first voltage at the inverting input terminal of the first comparator U1 is VCC1, the first reference voltage at the non-inverting input terminal of the first comparator U1 is higher than the voltage at the inverting input terminal, and the output terminal of the first comparator U1 outputs a high level signal. The voltage of the inverting input terminal of the second comparator U2 is also the first voltage VCC1, the second reference voltage of the non-inverting input terminal of the second comparator U2 is higher than the voltage of the inverting input terminal, the output terminal of the second comparator U2 also outputs a high level signal, the second diode D2 is turned on, so that the first triode Q1, the second triode Q2 and the third diode D3 are turned off, the discharging process of the rechargeable battery is finished, then the battery charging circuit 10 enters a charging state, the charging is started, the rechargeable battery is subjected to constant current charging by the constant current source charging circuit 14, and the third light emitting diode LED3 is turned on for indicating the charging.

When the voltage of the rechargeable battery rises to the second voltage VCC2, the voltage at the inverting input terminal of the first comparator U1 is the second voltage VCC2, the voltage at the inverting input terminal of the first comparator U1 is higher than the first reference voltage at the non-inverting input terminal, and the output terminal of the first comparator U1 changes from high level to low level. At this time, the voltage at the inverting input terminal of the second comparator U2 is also the second voltage VCC2, the second reference voltage at the non-inverting input terminal of the second comparator U2 is smaller than the voltage at the inverting input terminal, and the output terminal of the second comparator U2 is also changed from high level to low level. The low level signal is connected to the pulse generator circuit 13 composed of the third comparator U3, the tenth resistor R10, the eleventh resistor R11, the twelfth resistor R12, the thirteenth resistor R13 and the fourth diode D4 through the differential circuit 16 composed of the eighth resistor R8, the ninth resistor R9 and the second capacitor C2, and the output frequency control signal is provided to the pulse generator circuit 13. The square wave pulse output by the third comparator U3 changes from slow to fast, the control pulse width of the base of the fifth triode Q5 becomes small, the average value of the net charging current becomes small, and the battery charging circuit 10 enters a trickle charging state. At this time, when the square wave pulse output by the third comparator U3 is at a low level, the fifth diode D5 is turned on, and the fifth transistor Q5 is controlled to be turned off, the constant current source charging circuit 14 stops charging the rechargeable battery, and when the square wave pulse output by the third comparator U3 is at a high level, the fifth diode D5 is turned off, the fifth transistor Q5 is turned on, and the constant current source charging circuit 14 normally charges the rechargeable battery.

When the charging voltage of the first rechargeable battery BAT1 and the second rechargeable battery BAT2 rises to the third voltage VCC3, the voltage at the inverting input terminal of the fourth comparator U4 is the third voltage VCC3, the voltage at the inverting input terminal of the fourth comparator U4 is higher than the third reference voltage at the non-inverting input terminal, the output terminal of the fourth comparator U4 changes from high level to low level, the seventh diode D7 is turned on, the voltage at the non-inverting input terminal of the third comparator U3 becomes low, the voltage at the inverting input terminal of the third comparator U3 is higher than the voltage at the non-inverting input terminal, the output terminal of the third comparator U3 is clamped at low level, the fifth diode D5 is turned on, the base voltage of the fifth triode Q5 is pulled low, the fifth triode Q5 is turned off, the charging is ended, and the protection function of turning off the charging at the time of overvoltage charging by the detection circuit 17 is realized.

The battery charging circuit of the embodiment of the invention discharges the rechargeable battery by using the voltage comparator circuit 11 and the discharging circuit 12 which are composed of the operational amplifier before charging so as to eliminate the memory effect, and automatically converts the rechargeable battery into charging after discharging. The charging mode is pulse width modulation constant current charging, and pulse constant current charging adds the pulse discharge two kinds of modes, is full of the back and passes through overvoltage detection circuit 17 automated inspection rechargeable battery both ends voltage, realizes dual control and parallelly connected charging, and the circuit is simple, and is practical reliable, and low cost holds concurrently, can improve product competitiveness.

The battery charging circuit 10 of the embodiment of the present invention includes: a voltage comparator circuit 11, a push-button switch SA, a discharge circuit 12 connected to the voltage comparator circuit 11, a pulse generator circuit 13, and a constant current source charging circuit 14 connected to the pulse generator circuit 13; the positive electrode of the rechargeable battery is connected with the voltage comparator circuit 11, the discharge circuit 12, the pulse generator circuit 13 and the constant current source charging circuit 14, and the negative electrode of the rechargeable battery is grounded to GND; one end of the button switch SA is grounded GND, the other end of the button switch SA is connected with a voltage comparator circuit 11, when the button switch SA is triggered, the voltage comparator circuit 11 outputs low level, the discharge circuit 12 controls the rechargeable battery to discharge to a first voltage VCC1, the voltage comparator circuit 11 is controlled to output high level according to the first voltage VCC1, the pulse generator circuit 13 is controlled to output square wave pulse, the constant current source charging circuit 14 is controlled to charge the rechargeable battery according to the square wave pulse until the charging is completed, and the functions of battery discharging, charging, indicating, trickle charging and overvoltage protection are realized by using a common operational amplifier and some simple peripheral circuits.

In the description provided herein, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the invention, various features of the embodiments of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the invention and aiding in the understanding of one or more of the various inventive aspects. However, the disclosed method should not be interpreted as reflecting an intention that: that the invention as claimed requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, those skilled in the art will appreciate that while some embodiments herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the following claims, any of the claimed embodiments may be used in any combination.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The usage of the words first, second and third, etcetera do not indicate any ordering. These words may be interpreted as names. The steps in the above embodiments should not be construed as limiting the order of execution unless specified otherwise.

Claims

1. A battery charging circuit, comprising: the device comprises a voltage comparator circuit, a button switch, a discharge circuit connected with the voltage comparator circuit, a pulse generator circuit and a constant current source charging circuit connected with the pulse generator circuit; the positive electrode of the rechargeable battery is connected with the voltage comparator circuit, the discharge circuit, the pulse generator circuit and the constant current source charging circuit, and the negative electrode of the rechargeable battery is grounded; one end of the button switch is grounded, the other end of the button switch is connected with a voltage comparator circuit, when the button switch is triggered, the voltage comparator circuit outputs a low level, the rechargeable battery is controlled to discharge to a first voltage through the discharge circuit, the voltage comparator circuit is controlled to output a high level according to the first voltage, the pulse generator circuit is controlled to output square wave pulses, and the constant current source charging circuit is controlled to charge the rechargeable battery according to the square wave pulses until the charging is completed.

2. The battery charging circuit of claim 1, wherein the voltage comparator circuit comprises a first comparator, an input circuit, a second resistor, and a first diode, wherein a non-inverting input of the first comparator is connected to the input circuit and an anode of the first diode, a cathode of the first diode is connected to one end of the push button switch, a cathode of the first diode is further connected to an output of the first comparator through the second resistor, an inverting input of the first comparator is connected to an anode of the rechargeable battery, and an output of the first comparator is connected to the discharge circuit and the pulse generator circuit as an output of the voltage comparator circuit.

3. The battery charging circuit of claim 2, wherein the input circuit comprises a first variable resistor, a second variable resistor, a first resistor, and a first capacitor; one end of the first capacitor is connected with a power supply voltage, the other end of the first capacitor is connected with the non-inverting input end of the first comparator, the first end of the first variable resistor is connected with the non-inverting input end of the first comparator through a first resistor and is also connected with the discharge circuit, the second end of the first variable resistor is connected with the power supply voltage, and the sliding end of the first variable resistor is connected with the pulse generator circuit; the first end of the second variable resistor is connected with the non-inverting input end of the first comparator, and the second end and the sliding end of the second variable resistor are grounded.

4. The battery charging circuit of claim 1, wherein the battery charging circuit further comprises a power-up indication circuit comprising: the anode of the first light-emitting diode is connected with the power supply voltage through the third resistor, the cathode of the first light-emitting diode is grounded, and the anode of the first light-emitting diode is further connected with the voltage comparator circuit.

5. The battery charging circuit of claim 1, wherein the discharge circuit comprises: the LED driving circuit comprises a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a first triode, a second light emitting diode, a second comparator, a second diode, a third diode and a third triode; the first end of the first triode is connected with the output end of the voltage comparator circuit, the second end of the first triode is connected with the first end of the second triode, the third end of the first triode is connected with the cathode of the second light-emitting diode through the fourth resistor, the anode of the second light-emitting diode is connected with the power supply voltage, the second end of the second triode is connected with the inverting input end of the second comparator through the fifth resistor, the inverting input end of the second comparator is also connected with the anode of the rechargeable battery, the third end of the second triode is grounded, the non-inverting input end of the second comparator is connected with the voltage comparator circuit, the output end of the second comparator is connected with the anode of the second diode, and the cathode of the second diode is connected with the output end of the voltage comparator circuit and the cathode of the third diode, the anode of the third diode is connected with the constant current source charging circuit; the first end of the third triode is connected with the output end of the voltage comparator circuit through the sixth resistor, the second end of the third triode is connected with the pulse generator circuit through the seventh resistor, and the third end of the third triode is connected with the output end of the pulse generator circuit.

6. The battery charging circuit of claim 1, further comprising a differentiating circuit comprising an eighth resistor, a ninth resistor, and a second capacitor; one end of the eighth resistor is connected with the output end of the voltage comparator circuit, the other end of the eighth resistor is connected with the discharge circuit and one end of the second capacitor through the ninth resistor, the other end of the second capacitor is connected with the pulse generator circuit, and the other end of the eighth resistor is connected with the discharge circuit.

7. The battery charging circuit of claim 6, wherein the pulse generator circuit comprises: a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a third comparator, a third capacitor, and a fourth diode; the non-inverting input end of the third comparator is connected with the anode of the rechargeable battery, the non-inverting input end of the third comparator is grounded through the eleventh resistor and is connected with the output end of the third comparator through the twelfth resistor, the inverting input end of the third comparator is grounded through the third capacitor and is connected with the output end of the third comparator through the tenth resistor and is also connected with the anode of the fourth diode through the thirteenth resistor, and the cathode of the fourth diode is connected with the output end of the third comparator and the differential circuit.

8. The battery charging circuit of claim 1, wherein the constant current source charging circuit comprises: the fourth triode, the fifth triode, the sixth triode, the fourteenth resistor, the fifteenth resistor, the sixteenth resistor, the seventeenth resistor and the third light-emitting diode; the first end of the fourth triode is connected with the cathode of the third light emitting diode, the anode of the third light emitting diode is connected with the power supply voltage, the second end of the fourth triode is connected with the anode of the rechargeable battery, the second end of the fourth triode is also connected with the first end of the fifth triode through the fifteenth resistor and is connected with the first end of the sixth triode through the sixteenth resistor; the first end of the fifth triode is further connected with the discharge circuit, the second end of the sixth triode and the output end of the pulse generator circuit, the second end of the fifth triode is connected with the first end of the fourth triode, the first end of the sixth triode is grounded through the seventeenth resistor, and the third end of the fifth triode and the third end of the sixth triode are grounded.

9. The battery charging circuit of claim 1, further comprising a fifth diode, an anode of said fifth diode being connected to said constant current source charging circuit, and a cathode of said fifth diode being connected to an output of said pulse generator circuit.

10. The battery charging circuit of claim 1, further comprising an over-voltage detection circuit, the over-voltage detection circuit comprising: an eighteenth resistor, a fourth comparator, a sixth diode, and a seventh diode; the non-inverting input end of the fourth comparator is connected with the voltage comparator circuit and the anode of the sixth diode, the inverting input end of the fourth comparator is connected with the anode of the rechargeable battery, the cathode of the sixth diode is connected with the output end of the fourth comparator and the cathode of the seventh diode through the eighteenth resistor, and the anode of the seventh diode is the output end of the overvoltage detection circuit and is connected with the input end of the pulse generator circuit.