High-precision trickle charging circuit and method and electronic product

Abstract

According to the high-precision trickle charging circuit and method and the electronic equipment, the clamping circuit and the second power tube are added on the basis of the prior art, and the grid electrode of the second power tube is modulated through the output end of the clamping circuit, so that the current flowing through the second power tube can be effectively controlled, and the charging efficiency is improved. Therefore, according to the trickle charging circuit, the precision of the trickle charging circuit can be improved, so that the charging efficiency is improved.

Description

Technical Field

[0001] The embodiments of this application belong to the field of circuit technology, and in particular relate to a high-precision trickle charging circuit, method and electronic product. Background Technology

[0002] Electronic products require a precise trickle charging current to improve charging efficiency during the charging process, such as... Figure 1 As shown, a clamping circuit is used to modulate the magnitude of the trickle current. However, the offset voltage of the clamping circuit is too large when the voltage of the battery to be charged approaches zero, which causes a large deviation in the trickle charging current and thus affects the accuracy of the trickle charging current. Summary of the Invention

[0003] In order to solve or alleviate the technical problems in the prior art, in a first aspect, embodiments of this application provide a high-precision trickle charging circuit, including: a first power transistor, a second power transistor, a sampling transistor, and a clamping circuit;

[0004] The first terminal of the first power transistor is connected to the negative input terminal of the clamping circuit and the first terminal of the second power transistor, respectively, and the first terminal of the sampling transistor is connected to the positive input terminal of the first clamping circuit.

[0005] Both the second end of the first power transistor and the second end of the sampling transistor are connected to the power supply, and the second end of the second power transistor is connected to the battery to be charged.

[0006] The third terminal of the first power transistor is connected to the third terminal of the sampling transistor, and the third terminal of the second power transistor is connected to the output terminal of the first clamping circuit.

[0007] The first end of the sampling tube is also connected to a constant current source, and the constant current source is connected to a grounding terminal.

[0008] When the first power transistor and the sampling transistor are fully turned on, the first clamping circuit modulates the third terminal of the second power transistor, causing the second power transistor to partially turn on in order to determine the magnitude of the trickle charging current.

[0009] In a preferred embodiment of this application, the first power transistor, the second power transistor, and the sampling transistor are all PMOS transistors;

[0010] The first terminal of the first power transistor, the first terminal of the second power transistor, and the first terminal of the sampling transistor are all sources; the second terminal of the first power transistor, the second terminal of the second power transistor, and the second terminal of the sampling transistor are all drains; and the third terminal of the first power transistor, the third terminal of the second power transistor, and the third terminal of the sampling transistor are all gates.

[0011] Secondly, embodiments of this application provide a method for a high-precision trickle charging circuit, the method being implemented using the circuit described in the first aspect, the method comprising:

[0012] When the first power transistor and the sampling transistor are fully open, the first clamping circuit modulates the third terminal of the second power transistor, thereby controlling the current flowing through the second power transistor, that is, controlling the magnitude of the trickle charging current to determine the trickle charging current.

[0013] Thirdly, embodiments of this application provide an electronic device including the high-precision trickle charging circuit described in the first aspect.

[0014] This application provides a high-precision trickle charging circuit, method, and electronic device. By adding a clamping circuit and a second power transistor to the existing technology, the output terminal of the clamping circuit modulates the gate of the second power transistor, which can effectively control the current flowing through the second power transistor, thereby controlling the amount of trickle charging. Therefore, this application can improve the precision of the trickle charging circuit, thereby improving the charging efficiency. Attached Figure Description

[0015] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. Some specific embodiments of this application will be described in detail below with reference to the accompanying drawings in an exemplary and non-limiting manner. The same reference numerals in the drawings designate the same or similar parts or components. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0016] Figure 1 It is a trickle charging circuit provided by existing technology;

[0017] Figure 2 This is a trickle charging circuit provided in an embodiment of this application. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, of the embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort should fall within the scope of protection of the present application.

[0019] like Figure 1 As shown, a trickle charging circuit is provided in the prior art. In the prior art circuit, both the power transistor NM1 and the sampling transistor NM2 are NMOS. The clamping circuit AMP1 modulates the NMOS to control the magnitude of the trickle charging current.

[0020] exist Figure 1In this circuit, the first terminal of power transistor NM1 and the first terminal of sampling transistor NM2 are both sources, the second terminal of power transistor NM1 and the second terminal of sampling transistor NM2 are both drains, and the third terminal of power transistor NM1 and the third terminal of sampling transistor NM2 are both gates. The drains of power transistor NM1 and sampling transistor NM2 are both connected to a power supply, and the source of power transistor NM1 is connected to the battery to be recharged. The source of the sampling transistor is connected to power transistor PM4 and resistor R1, generating a voltage that is connected to the negative input terminal of clamping circuit AMP1. The positive input terminal of clamping circuit AMP1 is connected to a reference voltage, which is generated by a constant current source and resistor R2. The output stage of clamping circuit AMP1 is connected to the gates of power transistor NM1 and sampling transistor NM2.

[0021] In the prior art, the accuracy of the charging cut-off current is limited by two factors: (1) the offset voltage of the clamping circuit AMP1. Since the voltage of the battery to be charged is close to zero, the offset voltage of the clamping circuit AMP1 will have a significant impact on the current flowing through the sampling tube NM2, thus affecting the accuracy of the trickle charging current.

[0022] To address the problems in the existing technology, the first aspect is, such as Figure 2 As shown in the figure, this application embodiment provides a high-precision trickle charging circuit, including: a first power transistor PM1, a second power transistor PM3, a sampling transistor PM2, and a clamping circuit AMP2; after the first power transistor PM1 and the sampling transistor PM2 are fully turned on, the clamping circuit AMP2 modulates the third terminal of the second power transistor PM3. When the current through the first power transistor PM1 and the current through the sampling transistor PM2 reach a set ratio, the current through the power transistor PM1 is the set trickle charging current. The first power transistor PM1, the second power transistor PM3, and the sampling transistor PM2 are all PMOS transistors; the first terminal of the first power transistor PM1, the first terminal of the second power transistor PM3, and the first terminal of the sampling transistor PM2 are all sources, the second terminals of the first power transistor PM1, the second terminal of the second power transistor PM3, and the second terminal of the sampling transistor PM2 are all drains, and the third terminals of the first power transistor PM1, the second power transistor PM3, and the third terminal of the sampling transistor PM2 are all gates.

[0023] The source of the first power transistor PM1 is connected to the negative input terminal of the clamping circuit AMP2 and the source of the second power transistor PM3, respectively, and the source of the sampling transistor PM3 is connected to the positive input terminal of the clamping circuit AMP2.

[0024] The drains of the first power transistor PM1 and the second power transistor PM2 are both connected to the power supply, and the drain of the sampling transistor PM2 is connected to the battery to be charged.

[0025] The gate of the first power transistor PM1 is connected to the gate of the sampling transistor PM2, and the gate of the second power transistor PM3 is connected to the output terminal of the clamping circuit AMP2.

[0026] The source of the sampling tube PM2 is connected to the constant current source I2, and the constant current source I2 is connected to the ground terminal gnd; the constant current source I2 is the reference current.

[0027] When the first power transistor PM1 and the sampling transistor PM2 are fully turned on, the clamping circuit AMP2 will modulate the third terminal of the second power transistor PM3. When the current passing through the first power transistor PM1 and the current passing through the sampling transistor PM2 reach a set ratio, the modulation process is completed, and the current passing through the power transistor PM1 is the set trickle charging current.

[0028] In this embodiment of the application, when the electronic product starts trickle charging, the first power transistor PM1, the second power transistor PM3 and the sampling transistor PM2 will be turned on. When the current of the first power transistor PM1 is less than the set trickle charging current, the output voltage of the clamping circuit AMP2 will drop, so the current passing through the first power transistor PM1 will increase.

[0029] When the trickle charging current continues to increase and exceeds the set trickle charging current, the output voltage of the clamping circuit AMP2 will rise, thus reducing the current passing through the first power transistor PM1.

[0030] In this embodiment of the application, after the above modulation process, the current through the first power transistor PM1 stabilizes and becomes the trickle charging current during the charging process of the electronic product.

[0031] In this embodiment, the trickle charging accuracy depends on the offset voltage of the clamping circuit AMP1 and the ratio error between the first power transistor PM1 and the sampling transistor PM2. Compared with the prior art, this application reduces the offset voltage of the clamping circuit AMP2 by using a PMOS power transistor, thereby reducing the ratio error between the first power transistor PM1 and the sampling transistor PM2, thus increasing the accuracy of the trickle charging current.

[0032] In this embodiment, the trickle charging current I1 of the electronic product is calculated using the following formula: I1 = un * Cox * W1 / L1 [(Vgs - Vth1) * Vds1 - 0.5 * Vds1 * Vds1], where un is the electron mobility, Cox is the gate oxide capacitance per unit area, W1 / L1 is the channel width-to-length ratio of the power transistor, Vgs is the gate-source voltage of the power transistor, Vth1 is the threshold voltage of the power transistor, and Vds1 is the drain-source voltage of the power transistor. The sampling current I2 of the sampling transistor is calculated using the following formula: I2 = un * Cox * W2 / L2 [(Vgs - Vth2) * Vds2 - 0.5 * Vds2 * Vds2], where un is the electron mobility, Cox is the gate oxide capacitance per unit area, W2 / L2 is the channel width-to-length ratio of the sampling transistor, Vgs is the gate-source voltage of the sampling transistor, Vth2 is the threshold voltage of the sampling transistor, and Vds2 is the drain-source voltage of the sampling transistor. As can be seen from the above formula, by reducing the voltage difference between the two voltages Vds1 and Vds2, the proportional accuracy of the trickle charging current I1 and the sampling current I2 of the sampling tube can be improved. Therefore, this application uses a PMOS transistor to ensure that when the battery voltage approaches zero, the offset voltage of the clamping circuit is the voltage difference between Vds1 and Vds2.

[0033] In the prior art, the voltage difference P1 between two voltages, Vds1 and Vds2, during trickle charging of electronic products is calculated using the following formula:

[0034] P1 = I2 * R0 + VdsPM1 + Vosamp1 - Vbat, where I2 is the sampling current of the sampling transistor, R0 is the setting resistor, VdsPM1 is the drain-source voltage of the PMOS, Vosamp1 is the offset voltage of the clamping circuit, and Vbat is the battery voltage.

[0035] The voltage difference P2 between the two voltages Vds1 and Vds2 during trickle charging of the electronic product provided in this application is calculated using the following formula:

[0036] P2 = Vosamp1, where Vosamp1 is the offset voltage of the clamping circuit.

[0037] Secondly, embodiments of this application also provide a method for a high-precision trickle charging circuit, the method being implemented using the circuit described in the first aspect, the method comprising:

[0038] When the first power transistor PM1 and the sampling transistor PM2 are fully turned on, the clamping circuit AMP1 modulates the gate of the second power transistor PM3, thereby controlling the current flowing through the second power transistor PM2, that is, controlling the magnitude of the trickle charging current to determine the charging cut-off current.

[0039] Thirdly, embodiments of this application also provide an electronic device, including the high-precision trickle charging circuit described in the first aspect.

[0040] Compared with the prior art, the present application provides a high-precision trickle charging circuit, method and electronic device. By using PMOS as the power transistor on the basis of the prior art, the offset voltage of the clamping circuit will not be affected when the battery voltage approaches zero, and the deviation of the current flowing through the power transistor will also be reduced. Therefore, the present application can improve the accuracy of the trickle charging current, thereby improving the charging efficiency.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A high-precision trickle charging circuit, characterized in that, include: First power transistor, second power transistor, sampling transistor, and clamping circuit; The first terminal of the first power transistor is connected to the negative input terminal of the clamping circuit and the first terminal of the second power transistor, respectively, and the first terminal of the sampling transistor is connected to the positive input terminal of the first clamping circuit. Both the second end of the first power transistor and the second end of the sampling transistor are connected to the power supply, and the second end of the second power transistor is connected to the battery to be charged. The third terminal of the first power transistor is connected to the third terminal of the sampling transistor, and the third terminal of the second power transistor is connected to the output terminal of the clamping circuit. The first end of the sampling tube is also connected to a constant current source, and the constant current source is connected to a grounding terminal. When the first power transistor and the sampling transistor are fully turned on, the clamping circuit modulates the third terminal of the second power transistor, causing the second power transistor to partially turn on in order to determine the magnitude of the trickle charging current.

2. The high-precision trickle charging circuit as described in claim 1, characterized in that, The first power transistor, the second power transistor, and the sampling transistor are all PMOS transistors; The first terminal of the first power transistor, the first terminal of the second power transistor, and the first terminal of the sampling transistor are all sources; the second terminal of the first power transistor, the second terminal of the second power transistor, and the second terminal of the sampling transistor are all drains; and the third terminal of the first power transistor, the third terminal of the second power transistor, and the third terminal of the sampling transistor are all gates.

3. A method for a high-precision trickle charging circuit, characterized in that, The method is implemented using the circuit described in claim 1 or 2, and the method includes: When the first power transistor and the sampling transistor are fully open, the first clamping circuit modulates the third terminal of the second power transistor, thereby controlling the current flowing through the second power transistor, that is, controlling the magnitude of the trickle charging current to determine the trickle charging current.

4. An electronic device, characterized in that, Includes the high-precision trickle charging circuit as described in claim 1 or 2.

Images