A battery charging circuit

Abstract

The present invention relates to the technical field of battery charging circuits, and more particularly to a low-cost battery charging circuit, comprising a power input terminal J1 and a power output terminal J2. The power input terminal is connected to the anode of a diode D1 and the emitters of transistors Q4 and Q6, respectively. The cathode of diode D1 is connected to one end of a resistor R4 and a constant-current charging circuit. The other end of resistor R4 is connected to the source of a MOS transistor Q3. The drain of MOS transistor Q3 is connected to capacitors C1, C2, and the power output terminal J2. The base of transistor Q4 is connected to the source of MOS transistor Q3. The collector of transistor Q4 is connected to resistor R8 and the gate of MOS transistor Q3, respectively. The collector of transistor Q6 is connected to resistor R8. The base of transistor Q6 is connected to resistor R14. The other end of resistor R14 is connected to the collector of transistor Q5. This circuit utilizes a small number of transistors, MOS transistors, resistors, and capacitors to achieve battery charging management.

Description

Technical Field

[0001] The present invention relates to the technical field of battery charging circuits, and in particular to a battery charging circuit. Background Art

[0002] There are two common approaches to battery charging in portable electronic products: using expensive charge management chips or simply charging the battery with current-limiting resistors. The former is too expensive, while the latter is too damaging to the battery, shortening its lifespan. Summary of the Invention

[0003] In order to overcome the above defects of the prior art, the present invention provides a battery charging circuit to solve the above

[0004] The problems raised in the background technology are described.

[0005] The present invention solves the problems in the prior art by adopting a technical solution: a battery charging circuit, comprising a power input terminal J1, a power output terminal J2, a diode D1, a transistor Q1, a MOS transistor Q2, a MOS transistor Q3, a transistor Q4, a transistor Q5, and a transistor Q6. The power input terminal is respectively connected to the anode of the diode D1 and the emitters of the transistors Q4 and Q6. The cathode of the diode D1 is connected to one end of a resistor R4 and a constant current charging circuit. The other end of the resistor R4 is connected to the source of the MOS transistor Q3. The drain of the MOS transistor Q3 is connected to capacitors C1, C2, and the power output terminal J2. The base of the transistor Q4 is connected to the source of the MOS transistor Q3. The collector of the transistor Q4 is respectively connected to resistor R8 and the gate of the MOS transistor Q3. The collector of the transistor Q6 is connected to resistor R8. The base of the transistor Q6 is connected to resistor R14. The other end of the resistor R14 is connected to the collector of the transistor Q5.

[0006] As a preferred embodiment of the present invention, the constant current charging circuit includes a resistor R1 and a resistor R3 connected to the cathode of the diode, the other end of the resistor R3 is connected to the source of the MOS transistor Q2, the other end of the resistor R1 is connected to the resistor R2 and the gate of the MOS transistor Q2, the drain of the MOS transistor Q2 is connected to the source of the MOS transistor Q3, the other end of the resistor R2 is connected to the collector of the transistor Q1, the base of the transistor Q1 is connected to the resistor R13, and the emitter of the transistor Q1 is grounded.

[0007] As a preferred solution of the present invention, the transistors Q1 and Q5 are NPN transistors, and the transistors Q4 and Q6 are PNP transistors.

[0008] As a preferred solution of the present invention, the MOS tube is an AO3415 MOS tube.

[0009] As a preferred solution of the present invention, the positive electrode of the power input terminal J1 is connected to the power supply VIN-5V, and the positive electrode of the power output terminal J2 is connected to the battery V-BAT.

[0010] Compared with the prior art, the present invention has the following technical effects:

[0011] The present invention provides a battery charging circuit, which uses a small number of triodes, MOS tubes, resistors and capacitors to achieve battery charging management. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a circuit schematic diagram of a battery charging circuit in the invention. DETAILED DESCRIPTION

[0013] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0014] The description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0015] As shown in the accompanying drawings: a battery charging circuit includes a power input terminal J1, a power output terminal J2, a diode D1, a transistor Q1, a MOS transistor Q2, a MOS transistor Q3, a transistor Q4, a transistor Q5, and a transistor Q6. The power input terminal is respectively connected to the anode of the diode D1 and the emitters of the transistors Q4 and Q6. The cathode of the diode D1 is connected to one end of a resistor R4 and a constant current charging circuit. The other end of the resistor R4 is connected to the source of the MOS transistor Q3. The drain of the MOS transistor Q3 is connected to capacitors C1, C2, and the power output terminal J2. The base of the transistor Q4 is connected to the source of the MOS transistor Q3. The collector of the transistor Q4 is respectively connected to resistor R8 and the gate of the MOS transistor Q3. The collector of the transistor Q6 is connected to resistor R8. The base of the transistor Q6 is connected to resistor R14. The other end of the resistor R14 is connected to the collector of the transistor Q5.

[0016] As a preferred embodiment of the present invention, the constant current charging circuit includes a resistor R1 and a resistor R3 connected to the cathode of the diode, the other end of the resistor R3 is connected to the source of the MOS transistor Q2, the other end of the resistor R1 is connected to the resistor R2 and the gate of the MOS transistor Q2, the drain of the MOS transistor Q2 is connected to the source of the MOS transistor Q3, the other end of the resistor R2 is connected to the collector of the transistor Q1, the base of the transistor Q1 is connected to the resistor R13, and the emitter of the transistor Q1 is grounded.

[0017] Preferably, the transistors Q1 and Q5 are NPN transistors, and the transistors Q4 and Q6 are PNP transistors.

[0018] Preferably, the MOS tube is an AO3415 MOS tube.

[0019] Preferably, the positive electrode of the power input terminal J1 is connected to the power supply VIN-5V, and the positive electrode of the power output terminal J2 is connected to the battery V-BAT.

[0020] The working principle of this embodiment, taking lithium battery charging as an example, is as follows:

[0021] 1) When the lithium battery voltage is less than 3V, transistors Q5 and Q6 are non-conducting, and transistors Q1 and MOSFET Q2 are also non-conducting. Power supply VIN_5V charges V_BAT through diode D1, resistor R4, and MOSFET Q3. The charging current gradually rises to Isat, then stabilizes, maintaining constant current charging. Resistor R4 acts as a current sampling resistor, and transistor Q4 provides negative feedback. When the current flowing through resistor R4 exceeds Isat, the collector voltage of transistor Q4 increases, causing the VGS voltage of MOSFET Q3 to decrease, thereby reducing the charging current. Conversely, when the charging current is less than Isat, the collector voltage of transistor Q4 decreases, causing the VGS voltage to increase, thereby increasing the charging current.

[0022] 2) When the lithium battery voltage is greater than 3V and less than 4.2V, transistors Q5 and Q6 are off, while transistors Q1 and MOS transistor Q2 are on. The current sampling resistor is approximately the parallel combination of resistors R4 and R3 (approximately 1 / 10 of R4's value). Transistor Q4 also provides negative feedback, stabilizing the charging current at approximately 10*Isat.

[0023] 3) When the charging voltage rises to 4.2V, transistors Q5 and Q6 are turned on, raising the gate voltage of MOS tube Q3 and lowering the VGS voltage of MOS tube Q3, thereby reducing the charging current until charging is turned off.

[0024] Compared with the prior art, the present invention has the following technical effects:

[0025] The present invention provides a battery charging circuit, which uses a small number of triodes, MOS tubes, resistors and capacitors to achieve battery charging management.

[0026] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A battery charging circuit, characterized in that: The circuit includes a power input terminal J1, a power output terminal J2, a diode D1, a transistor Q1, a MOS transistor Q2, a MOS transistor Q3, a transistor Q4, a transistor Q5, and a transistor Q6. The power input terminal is respectively connected to the positive electrode of the diode D1, the emitters of the transistor Q4 and the transistor Q6, the negative electrode of the diode D1 is connected to one end of the resistor R4 and the constant current charging circuit, the other end of the resistor R4 is connected to the source of the MOS transistor Q3, the drain of the MOS transistor Q3 is connected to the capacitor C1, the capacitor C2 and the power output terminal J2, the base of the transistor Q4 is connected to the source of the MOS transistor Q3 for adjusting the charging current, the collector of the transistor Q4 is respectively connected to the resistor R8 and the gate of the MOS transistor Q3, and the collector of the transistor Q6 is connected to the gate of the MOS transistor Q3. The cathode of the diode is connected to resistor R8, the base of the transistor Q6 is connected to resistor R14, the other end of the resistor R14 is connected to the collector of the transistor Q5; the constant current charging circuit includes resistors R1 and R3 connected to the cathode of the diode, the other end of the resistor R3 is connected to the source of the MOS transistor Q2, the other end of the resistor R1 is respectively connected to resistor R2 and the gate of the MOS transistor Q2, the drain of the MOS transistor Q2 is connected to the source of the MOS transistor Q3, the other end of the resistor R2 is connected to the collector of the transistor Q1, the base of the transistor Q1 is connected to resistor R13, the emitter of the transistor Q1 is grounded, the positive electrode of the power input terminal J1 is connected to the power supply VIN-5V, and the positive electrode of the power output terminal J2 is connected to the battery V-BAT.

2. A battery charging circuit according to claim 1, characterized in that: The transistors Q1 and Q5 are NPN transistors, and the transistors Q4 and Q6 are PNP transistors.

3. The battery charging circuit according to claim 1, wherein: The MOS tube is AO3415MOS tube.

Images