An oscillation circuit for a charging chip and a lithium battery charging chip integrated with an MCU

Abstract

The application relates to the field of electronic circuits, and provides an oscillation circuit for a charging chip and a lithium battery charging chip integrated with an MCU, wherein the MCU in the lithium battery charging chip simultaneously provides charging signal control and external load PWM output control, a high-stability oscillation circuit is adopted to provide a clock signal for the MCU, the oscillation circuit comprises a power supply circuit and an oscillation output circuit, the power supply circuit provides a charging current for the oscillation output circuit and provides a bias voltage for the oscillation output circuit, the oscillation output circuit generates a periodically-changing voltage, converts the periodically-changing voltage into a clock signal output, and simultaneously performs temperature coefficient adjustment on the clock signal, so that the frequency of the clock signal is not affected by environmental temperature changes; the application makes the clock signal provided by the MCU in the lithium battery integrated charging chip stable and not affected by temperature, and guarantees stable working of the charging chip.

Description

Technical Field

[0001] This invention relates to the field of electronic circuits, and more specifically, to an oscillation circuit for a charging chip and a lithium battery charging chip with an integrated MCU. Background Technology

[0002] With the development of technology, battery charging technology has been widely applied. Battery charging chips are used to manage the charging of lithium batteries and are widely used in charging devices. Devices such as shavers and hand warmers require both charging management and load control. Therefore, some charging chips adopt an integrated design, integrating an MCU (Microcontroller Unit). While managing charging, they also set input and output ports to provide PWM signals for load control. MCUs generally require a clock module to provide a clock signal. A stable clock signal also affects the MCU's operation and output stability. Clock modules mostly use crystal oscillator circuits to provide clock signals to the MCU. Traditional oscillator circuits often use operational amplifiers, Schmitt triggers, etc., which typically have problems such as high power consumption, large chip area, and significant system delay. Furthermore, based on the system's power supply characteristics, the frequency of the clock signal output by the oscillator circuit is greatly affected by changes in ambient temperature, and the signal frequency may deviate from the set frequency depending on the increase or decrease in ambient temperature. When integrated chips are used for extended periods in charging devices such as shavers and hand warmers, the ambient temperature changes, which affects the clock signal and consequently the performance of the integrated charging chip. Summary of the Invention

[0003] The problem addressed by this invention is how to provide an oscillation circuit that can provide a stable, temperature-independent clock signal for the internal MCU of a lithium battery integrated charging chip.

[0004] To address the above problems, the present invention provides an oscillation circuit for a charging chip, comprising: a power supply circuit and an oscillation output circuit; The power supply circuit is connected to the oscillation output circuit. The power supply circuit provides charging current to the oscillation output circuit and bias voltage to the oscillation output circuit. The oscillation output circuit generates a periodically changing voltage and converts the periodically changing voltage (analog quantity) into a clock signal (digital quantity) for output. The oscillation output circuit adjusts the clock signal by temperature coefficient, so that the frequency of the clock signal is not affected by changes in ambient temperature, thus providing a stable clock signal for the charging chip.

[0005] Furthermore, the power supply circuit includes port ICDF and port VDAN.

[0006] Furthermore, the oscillation output circuit includes port IRCF, port VBS, and port CLKS; Port ICDF is connected to port IRCF to transmit the charging current Icg; Port VDAN is connected to port VBS to transmit the first bias voltage Vb1; Port CLKS is used to output the clock signal Sck.

[0007] Furthermore, the power supply circuit includes a bias circuit and a current source circuit; the bias circuit is connected to the current source circuit, and the bias circuit generates multiple bias voltages based on the power supply voltage and supplies them to the current source circuit so that it can work stably; the current source circuit generates a charging current Icg based on a negative feedback circuit structure, outputs it to the oscillation output circuit, and provides a first bias voltage Vb1 to a part of the circuit in the oscillation output circuit.

[0008] Furthermore, the oscillation output circuit includes a charging / discharging circuit and a conversion circuit. The charging / discharging circuit is connected to the conversion circuit. Based on a feedback circuit structure, the charging / discharging circuit periodically charges and discharges capacitor C1, thereby generating a periodically changing voltage. The conversion circuit converts the periodically changing voltage into a periodically changing level signal, and divides the level signal by two to generate a clock signal Sck. The clock signal Sck is output through port CLKS. Based on the periodically changing voltage generated in the charging / discharging circuit, the frequency of the clock signal Sck output by the conversion circuit can be adjusted by a temperature coefficient, thus making the frequency of the clock signal Sck unaffected by changes in ambient temperature.

[0009] The present invention also provides a lithium battery charging chip with integrated MCU, including a main control module, a clock module, a charging control module, a power interface, a battery interface, and an external signal port. The clock module is connected to the main control module. The input terminal of the charging control module is connected to the power interface, the output terminal is connected to the battery interface, and the controlled terminal is connected to the main control module. The charging control module performs charging control according to the signal from the main control module. The external signal port is connected to the main control module. The clock module adopts the above-mentioned oscillation circuit to provide a stable clock signal to the main control module.

[0010] Compared with the prior art, the beneficial effects of the present invention are: The main control MCU inside the lithium battery charging chip of this invention provides both charging signal control and PWM output control for external loads. The clock module uses a highly stable oscillation circuit to provide a clock signal to the MCU. This oscillation circuit includes a power supply circuit and an oscillation output circuit. The power supply circuit provides the charging current to the oscillation output circuit and provides a bias voltage to the oscillation output circuit. The oscillation output circuit generates a periodically changing voltage and converts the periodically changing voltage into a clock signal output. The oscillation output circuit adjusts the clock signal by a temperature coefficient so that the frequency of the clock signal is not affected by changes in ambient temperature. The oscillation output circuit has a simple and stable circuit structure, providing a precise and stable clock signal to the MCU inside the charging chip under the premise of low power consumption, ensuring the stability of the MCU output signal and the stability of the charging chip operation. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the oscillation circuit used in the internal clock of the lithium battery charging chip in an embodiment of the present invention. Figure 2 This is a schematic diagram of the power supply circuit in an embodiment of the present invention; Figure 3 This is a schematic diagram of the principle structure of the oscillation output circuit according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the principle structure of the lithium battery charging chip according to an embodiment of the present invention; Figure 5 This is a packaging diagram of the lithium battery charging chip according to an embodiment of the present invention.

[0012] Explanation of reference numerals in the attached figures: 1-Clock module; 2-Main control module; 3-Charging control module; 4-Power interface; 5-Battery interface; 6-External signal port; 10-Power supply circuit; 20-Oscillation output circuit; 101-Bias circuit; 102-Current source circuit; 201-Charging and discharging circuit; 202-Conversion circuit. Detailed Implementation

[0013] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0014] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0015] In the description of this specification, references to terms such as "embodiment," "one embodiment," and "one implementation" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or implementation is included in at least one embodiment or illustrative implementation of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or implementation. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or implementations.

[0016] like Figure 1 As shown, the present invention provides an oscillation circuit for a charging chip, which can provide a stable and accurate clock signal for the MCU inside the lithium battery charging chip, including: a power supply circuit 10 and an oscillation output circuit 20.

[0017] The power supply circuit 10 is connected to the oscillation output circuit 20. The power supply circuit 10 provides charging current and bias voltage to the oscillation output circuit 20. The oscillation output circuit 20 generates a periodically changing voltage and converts the periodically changing voltage (analog quantity) into a clock signal (digital quantity) for output. The oscillation output circuit 20 adjusts the clock signal according to its temperature coefficient, so that the frequency of the clock signal is not affected by changes in ambient temperature.

[0018] The power supply circuit 10 includes port ICDF and port VDAN.

[0019] The oscillation output circuit 20 includes port IRCF, port VBS and port CLKS.

[0020] Port ICDF is connected to port IRCF to transmit the charging current Icg; port VDAN is connected to port VBS to transmit the first bias voltage Vb1; port CLKS is used to output the clock signal Sck.

[0021] like Figure 1 As shown, the power supply circuit 10 includes a bias circuit 101 and a current source circuit 102.

[0022] It should be noted that the bias circuit 101 is connected to the current source circuit 102. The bias circuit 101 generates multiple bias voltages based on the power supply voltage and supplies them to the current source circuit 102 so that it can work stably. The current source circuit 102 generates a charging current Icg based on a negative feedback circuit structure, outputs it to the oscillation output circuit 20, and provides a first bias voltage Vb1 to a part of the circuit in the oscillation output circuit 20.

[0023] like Figure 1As shown, the oscillation output circuit 20 includes a charging / discharging circuit 201 and a conversion circuit 202. The charging / discharging circuit 201 is connected to the conversion circuit 202. The charging / discharging circuit 201 periodically charges and discharges the capacitor C1 based on a feedback circuit structure, thereby generating a periodically changing voltage. The conversion circuit 202 converts the periodically changing voltage into a periodically changing level signal, and divides the level signal by two to generate a clock signal Sck. The clock signal Sck is output through the CLKS port. Based on the periodically changing voltage generated in the charging / discharging circuit 201, the frequency of the clock signal Sck output by the conversion circuit 202 can be adjusted by a temperature coefficient, thus making the frequency of the clock signal Sck unaffected by changes in ambient temperature.

[0024] like Figure 2 As shown, the bias circuit 101 includes MOSFETs M1, M2, M3, M4, M5, M6, M7, M8, M9, and M10.

[0025] The source of MOSFET M1 is connected to the power supply VDD, and the gate of MOSFET M1 is connected to the drain of MOSFET M1. The drain of MOSFET M1 is connected to the drain of MOSFET M2. The drain of MOSFET M2 is connected to the gate of MOSFET M1, and the gate of MOSFET M2 is connected to the gate of MOSFET M4. The source of MOSFET M2 is grounded. The source of MOSFET M3 is connected to the source of MOSFET M1, and the gate of MOSFET M3 is connected to the drain of MOSFET M3. The drain of MOSFET M3 is connected to the drain of MOSFET M4. The drain of MOSFET M4 is connected to the gate of MOSFET M3, and the gate of MOSFET M4 is connected to the drain of MOSFET M2. The source of MOSFET M4 is grounded. The source of MOSFET M5 is connected to the source of MOSFET M3, and the gate of MOSFET M5 is connected to the drain of MOSFET M3. The drain of MOSFET M5 is connected to the drain of MOSFET M6.

[0026] The drain of MOSFET M6 is connected to the drain of MOSFET M5, the gate of MOSFET M6 is connected to the drain of MOSFET M6, and the source of MOSFET M6 is connected to the drain of MOSFET M7. The drain of MOSFET M7 is connected to the source of MOSFET M6, the gate of MOSFET M7 is connected to the drain of MOSFET M7, and the source of MOSFET M7 is grounded. The source of MOSFET M8 is connected to the power supply VDD, the gate of MOSFET M8 is connected to the drain of MOSFET M8, and the drain of MOSFET M8 is connected to the source of MOSFET M9. The source of MOSFET M9 is connected to the gate of MOSFET M8, the gate of MOSFET M9 is connected to the drain of MOSFET M9, and the drain of MOSFET M9 is connected to the drain of MOSFET M10. The drain of MOSFET M10 is connected to the gate of MOSFET M9, the gate of MOSFET M10 is connected to the gate of MOSFET M4, and the source of MOSFET M10 is grounded.

[0027] The gate of MOSFET M2 is connected to the gate of MOSFET M4, and the gate of MOSFET M2 is also connected to its own drain. Based on this circuit connection structure, the gate voltage Vgm4 of MOSFET M4 serves as the bias voltage for MOSFETs M10 and M23, respectively, causing them to operate in the subthreshold region. The gate of MOSFET M3 is connected to its own drain, and the gate of MOSFET M5 is connected to the drain of MOSFET M3. Based on this circuit connection structure, the gate voltage Vgm5 of MOSFET M5 serves as the bias voltage for MOSFETs M11, M15, M19, and M24, respectively, causing them to operate in the subthreshold region.

[0028] The gate of MOSFET M6 is connected to its own drain, and the drain of MOSFET M6 is connected to the drain of MOSFET M5. Based on this circuit structure, the drain voltage Vdm6 of MOSFET M6 serves as the bias voltage for MOSFETs M13 and M17, causing them to operate in the subthreshold region. The gate of MOSFET M9 is connected to its own drain, and the drain of MOSFET M9 is connected to the drain of MOSFET M10. Based on this circuit structure, the drain voltage Vdm9 of MOSFET M9 serves as the bias voltage for MOSFETs M12 and M16, causing them to operate in the subthreshold region.

[0029] like Figure 2 The current source circuit 102 shown includes MOSFETs M11, M12, M13, M14, M15, M16, M17, M18, M19, M20, M21, M22, M23, M24, and M25, resistors R1 and R2, port ICDF, and port VDAN.

[0030] The source of MOSFET M11 is connected to the power supply VDD, the gate of MOSFET M11 is connected to the gate of MOSFET M15, and the drain of MOSFET M11 is connected to the source of MOSFET M12. The source of MOSFET M12 is connected to the drain of MOSFET M11, the gate of MOSFET M12 is connected to the gate of MOSFET M16, and the drain of MOSFET M12 is connected to the drain of MOSFET M13. The drain of MOSFET M13 is connected to the drain of MOSFET M12, the gate of MOSFET M13 is connected to the gate of MOSFET M17, and the source of MOSFET M13 is connected to the drain of MOSFET M14. The drain of MOSFET M14 is connected to the source of MOSFET M13, the gate of MOSFET M14 is connected to the gate of MOSFET M18, and the source of MOSFET M14 is grounded.

[0031] The source of MOSFET M15 is connected to the source of MOSFET M11, the gate of MOSFET M15 is connected to the gate of MOSFET M5, and the drain of MOSFET M15 is connected to the source of MOSFET M16. The source of MOSFET M16 is connected to the drain of MOSFET M15, the gate of MOSFET M16 is connected to the drain of MOSFET M9, and the drain of MOSFET M16 is connected to the drain of MOSFET M17. The drain of MOSFET M17 is connected to the drain of MOSFET M16, the gate of MOSFET M17 is connected to the gate of MOSFET M6, and the source of MOSFET M17 is connected to the drain of MOSFET M18. The drain of MOSFET M18 is connected to the source of MOSFET M17, the gate of MOSFET M18 is connected to the drain of MOSFET M13, and the source of MOSFET M18 is grounded.

[0032] The source of MOSFET M19 is connected to the source of MOSFET M15, the gate of MOSFET M19 is connected to the gate of MOSFET M24, and the drain of MOSFET M19 is connected to the drain of MOSFET M20. The drain of MOSFET M20 is connected to the drain of MOSFET M19, the gate of MOSFET M20 is connected to the gate of MOSFET M25, the source of MOSFET M20 is connected to the upper end of resistor R1, the lower end of resistor R1 is connected to the upper end of resistor R2, and the lower end of resistor R2 is grounded.

[0033] The drain of MOSFET M21 is connected to the drain of MOSFET M11, the gate of MOSFET M21 is connected to the drain of MOSFET M19, and the source of MOSFET M21 is connected to the source of MOSFET M22. The drain of MOSFET M22 is connected to the drain of MOSFET M15, the gate of MOSFET M22 is connected to the drain of MOSFET M24, and the source of MOSFET M22 is connected to the drain of MOSFET M23. The drain of MOSFET M23 is connected to the source of MOSFET M21, the gate of MOSFET M23 is connected to the gate of MOSFET M10, and the source of MOSFET M23 is grounded.

[0034] The source of MOSFET M24 is connected to the source of MOSFET M19, the gate of MOSFET M24 is connected to the gate of MOSFET M15, and the drain of MOSFET M24 is connected to the drain of MOSFET M25. The gate of MOSFET M24 is connected to the drain of MOSFET M16, and the gate of MOSFET M24 is connected to port ICDF. The drain of MOSFET M25 is connected to port VDAN, the gate of MOSFET M25 is connected to the drain of MOSFET M25, and the source of MOSFET M25 is grounded.

[0035] MOSFETs M22, M16, M17, M18, M14, M13, and M12 are connected to form a negative feedback loop. This ensures that the drain voltage Vdm25 of MOSFET M25 remains equal to the drain voltage Vdm20 of MOSFET M20 despite power supply voltage fluctuations. Furthermore, the circuit connection structure of MOSFETs M17, M18, M14, and M13 also functions as an active load, significantly improving the feedback gain and feedback current of the negative feedback loop.

[0036] Both MOSFETs M20 and M25 operate in the subthreshold region. The expressions for the drain-source current Ids20 of MOSFET M20 and the drain-source current Ids25 of MOSFET M25 are shown in Equation (1) and Equation (2), respectively.

[0037] (1); (2); In the formula, Ks represents the process-related parameters of the MOSFET, W20 represents the channel width of the MOSFET M20, L20 represents the channel width of the MOSFET M20, Vgs20 represents the gate-source voltage of the MOSFET M20, Vth20 represents the threshold voltage of the MOSFET M20, n represents the subthreshold slope factor, W25 represents the channel width of the MOSFET M25, L25 represents the channel width of the MOSFET M25, Vgs25 represents the gate-source voltage of the MOSFET M25, and Vth25 represents the threshold voltage of the MOSFET M25.

[0038] In the formula, VT is the thermal voltage, and its expression is VT=B T / q, where B is the Boltzmann constant, T is the thermodynamic temperature, and q is the unit charge.

[0039] With Vth20=Vth25 set, according to formulas (1) and (2), the expression for the source voltage Vsm20 of MOS transistor M20 can be obtained, as shown in formula (3).

[0040] (3); Resistors R1 and R2 are two resistors with opposite temperature coefficients, and their expressions are shown in formula (4) and formula (5), respectively.

[0041] (4); (5); In the formula, R1n is the resistance value of resistor R1 at the reference temperature, a1 is the temperature coefficient of resistor R1 and a1>0, Td is the actual temperature change, R2n is the resistance value of resistor R2 at the reference temperature, a2 is the temperature coefficient of resistor R2 and a2<0.

[0042] Let the sum of resistors R1 and R2 be resistor Re, then the expression for resistor Re is shown in formulas (6) and (7).

[0043] (6); (7); In the formula, Ren is the resistance value of resistor Re at the reference temperature, i.e., Ren = R1n + R2n, a is the temperature coefficient of resistor Re, and Kn is the ratio of resistor R1 to resistor R2, i.e., Kn = R1 / R2.

[0044] The expression for the current Ie flowing through the drain-source branch of the MOS transistor M20 in the current source circuit 102 is shown in formula (8).

[0045] ; (8); In the formula, Ren is the resistance value of resistor Re at the reference temperature, Kn is the ratio of resistor R1 to resistor R2, a1 is the temperature coefficient of resistor R1, and a1>0, a2 is the temperature coefficient of resistor R2, and a2<0, Td is the actual temperature change, B is Boltzmann constant, T is thermodynamic temperature, q is the unit charge, n is the subthreshold slope factor, W20 is the channel width of MOSFET M20, L20 is the channel width of MOSFET M20, W25 is the channel width of MOSFET M25, and L25 is the channel width of MOSFET M25.

[0046] The gate of MOSFET M19 is connected to the gate of MOSFET M26 in charging / discharging circuit 201 through the connection of port ICDF and port IRCF, forming a mirror structure. If the size ratio of MOSFET M19 to MOSFET M26 is set to 1:4, then the charging current Icg flowing through the drain-source branch of MOSFET M26 is four times the current Ie, i.e., Icg = 4Ie.

[0047] The drain of MOSFET M25 is connected to the gate of MOSFET M27 through the connection of port VDAN and port VBS. The drain voltage Vdm25 of MOSFET M25 is used as the bias voltage of MOSFET M27, that is, the first bias voltage Vb1=Vdm25, so that MOSFET M27 operates in the saturation region.

[0048] like Figure 3 As shown, the charging and discharging circuit 201 includes MOSFETs M26, M27, and M28, capacitor C1, port IRCF, and port VBS.

[0049] The source of MOSFET M26 is connected to power supply VDD, the gate of MOSFET M26 is connected to port IRCF, and the drain of MOSFET M26 is connected to the drain of MOSFET M27. The drain of MOSFET M27 is connected to the drain of MOSFET M26, the gate of MOSFET M27 is connected to port VBS, the upper end of the source capacitor C1 of MOSFET M27 is connected, and the lower end of capacitor C1 is grounded. The drain of MOSFET M28 is connected to the source of MOSFET M27, the gate of MOSFET M28 is connected to the output of inverter NGT2, and the source of MOSFET M28 is grounded.

[0050] MOSFET M26, based on a mirror structure, provides a charging current Icg to the branch containing capacitor C1. MOSFET M27, based on the first bias voltage Vb1, is in a conducting state, allowing the charging current Icg to charge capacitor C1, causing the source voltage Vsm27 of MOSFET M27 to continuously increase. The drain voltage Vdm27 of MOSFET M27 is transmitted to the input of inverter NGT1 in conversion circuit 202 via a wire connection. The drain voltage Vdm27 of MOSFET M27 = Vsm27 + VR, where VR is the voltage drop across MOSFET M27.

[0051] Inverter NGT1 has two threshold voltages: a high threshold voltage VnH and a low threshold voltage VnL. When the source voltage Vsm27 of MOSFET M27 rises to Vsm20 (i.e., Vsm27 = Vsm20), the voltage Vdm27 is greater than the high threshold voltage VnH. At this time, the gate of MOSFET M28 receives a forward bias voltage through feedback from the switching circuit 202 and is in the on state. After MOSFET M28 is turned on, capacitor C1 discharges to ground through MOSFET M28, and voltage Vdm27 continuously decreases. When voltage Vdm27 is less than the low threshold voltage VnL, the gate of MOSFET M28 receives a reverse bias voltage through feedback from the switching circuit 202 and is in the off state. After MOSFET M28 is turned off, the charging current Icg continues to charge capacitor C1, causing voltage Vdm27 to rise again. This results in periodic charging and discharging of capacitor C1 and periodic rises and falls of voltage Vdm27.

[0052] like Figure 3 As shown, the conversion circuit 202 includes MOSFETs M29, M30, M31, and M32, inverters NGT1 and NGT2, D flip-flop DFF1, and port CLKS.

[0053] The source of MOSFET M29 is connected to power supply VDD, the gate of MOSFET M29 is connected to the output of inverter NGT1, and the drain of MOSFET M29 is connected to the drain of MOSFET M30. The drain of MOSFET M30 is connected to the drain of MOSFET M29, the gate of MOSFET M30 is connected to the output of inverter NGT2, and the source of MOSFET M30 is connected to the source of MOSFET M31. The source of MOSFET M31 is connected to the drain of MOSFET M26, the gate of MOSFET M31 is connected to the output of inverter NGT2, and the drain of MOSFET M31 is connected to the drain of MOSFET M32. The drain of MOSFET M32 is connected to the drain of MOSFET M31, the gate of MOSFET M32 is connected to the output of inverter NGT1, and the source of MOSFET M32 is grounded.

[0054] The input of inverter NGT1 is connected to the source of MOSFET M30. The output of inverter NGT1 is connected to the input of inverter NGT2. The output of inverter NGT2 is connected to the CLK input of D flip-flop DFF1. The Q output of D flip-flop DFF1 is connected to port SCK. The Q' output of D flip-flop DFF1 is connected to the D input of D flip-flop DFF1. The CLK input of D flip-flop DFF1 is connected to the gate of MOSFET M30.

[0055] The input terminal of inverter NGT1 is connected to the drain of MOSFET M27, and the drain voltage Vdm27 of MOSFET M27 is used as its input voltage. The output terminal of inverter NGT1 is connected to the input terminal of inverter NGT2, making the output levels of inverter NGT1 and inverter NGT2 inversely related; that is, if the output level of inverter NGT1 is high, the output level of inverter NGT2 is low. Similarly, if the output level of inverter NGT1 is low, the output level of inverter NGT2 is high.

[0056] Inverter NGT1 has two threshold voltages: a high threshold voltage VnH and a low threshold voltage VnL. When voltage Vdm27 is greater than the high threshold voltage VnH, inverter NGT1 outputs a low level, and inverter NGT2 outputs a high level. MOSFETs M29 and M30 are then turned on, maintaining the input voltage of inverter NGT1 above the high threshold voltage VnH, thus keeping the output of inverter NGT2 at a high level. Since the gate of MOSFET M28 is connected to the output of inverter NGT2, MOSFET M28 is in the on state at this time.

[0057] When the voltage Vdm27 is less than the low threshold voltage VnL, inverter NGT1 outputs a high level, and inverter NGT2 outputs a low level. Therefore, MOSFETs M31 and M32 are turned on, maintaining the input voltage of inverter NGT1 below the low threshold voltage VnL, thus keeping the output of inverter NGT2 at a low level. Since the gate of MOSFET M28 is connected to the output of inverter NGT2, MOSFET M28 is in the off state at this time.

[0058] The circuit structure consisting of interconnected MOSFETs M29, M30, M31, M32, inverter NGT1, and inverter NGT2 has the function of converting a changing analog voltage signal (the drain voltage Vdm27 of MOSFET M27) ​​into a changing digital level signal (the output level of inverter NGT2), and avoids the use of operational amplifier circuits and Schmitt trigger circuits. It performs analog-to-digital conversion while having low power consumption.

[0059] The high and low level changes at the output of inverter NGT2 are periodic, with a frequency of fp. Module DFF1 is a divide-by-two circuit based on a D flip-flop, which outputs a clock signal Sck with a frequency of fk through port CLKS. When the voltage Vsm27 = Vsm20, the voltage Vdm27 is greater than the high threshold voltage VnH, causing the output level of inverter NGT2 to flip. The expression for the frequency fk of the clock signal Sck is shown in formula (9).

[0060] (9); In the formula, Vsm20 is the source voltage of MOSFET M20, Icg is the charging current, c1 is the capacitance of capacitor C1, Re is the sum of resistors R1 and R2, Ren is the resistance of resistor Re at the reference temperature, Kn is the ratio of resistor R1 to resistor R2, a1 is the temperature coefficient of resistor R1 (a1>0), a2 is the temperature coefficient of resistor R2 (a2<0), and Td is the actual temperature change.

[0061] Since a1 and a2 have opposite temperature coefficients, by adjusting the resistance ratio Kn, Kn can be made... a1 + a2 = 0. Therefore, Kn When a1+a2=0, the expression for the frequency fk of the clock signal Sck is shown in formula (10).

[0062] (10); As can be seen from formula (10), the frequency fk of the clock signal Sck is not affected by temperature change (Td) and has high stability.

[0063] like Figure 4 As shown, the present invention also provides a lithium battery charging chip with integrated MCU, including a main control module 2, a clock module 1, a charging control module 3, a power interface 4, a battery interface 5, and an external signal port 6. The clock module 1 is connected to the main control module 2. The input terminal of the charging control module 3 is connected to the power interface 4, the output terminal is connected to the battery interface 5, and the controlled terminal is connected to the main control module 2. The charging control module 3 performs charging control according to the signal from the main control module 2. The external signal port is connected to the main control module 2. The clock module 1 adopts the above-mentioned oscillation circuit to provide a stable clock signal to the main control module 2.

[0064] It should be noted that while managing charging, the MCU in the main control module 2 also receives external signals through external signal port 6 to provide PWM signals for load control. The charging control module 3 generally uses a half-bridge circuit composed of MOSFETs for charging control. At the same time, the charging voltage and current are sampled and sent to the main control module 2. The MOSFETs are controlled by the PWM signal of the main control module. This lithium battery charging chip is used for a long time in some charging devices such as hand warmers and shavers. When the ambient temperature changes, the frequency of the clock signal is not affected by the temperature change, which ensures the stability of the clock signal of the main control module 2, making the output signal of the main control module 2 stable. This ensures the stable operation of the lithium battery charging chip and can accurately control battery charging and external loads.

[0065] like Figure 5 The diagram illustrates a packaging structure for a lithium battery charging chip. The diagram uses an SOP-16 package. Port VIN is the power interface 4, used to connect to a power source. Port BAT is the battery interface 5, used to connect to a lithium battery. Port EN is the enable port, internally connected to the main control module 2. Port ISET is the setting port, internally connected to the main control module 2, used for debugging, and grounded during normal use. PA and PC are 10-channel external signal ports 6, supporting ADC and PWM output. When used in charging equipment, it can receive external signals (such as switch / button signals) and transmit them to the main control module 2, or output PWM control signals to load control circuits (such as heating control and motor drive).

[0066] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. An oscillation circuit for a charging chip, characterized in that, include: Power supply circuit (10) and oscillation output circuit (20); The power supply circuit (10) is connected to the oscillation output circuit (20). The power supply circuit (10) provides charging current to the oscillation output circuit (20) and provides bias voltage to the oscillation output circuit (20). The oscillation output circuit (20) generates a periodically changing voltage and converts the periodically changing voltage into a clock signal output; The oscillation output circuit (20) adjusts the clock signal by temperature coefficient so that the frequency of the clock signal is not affected by changes in ambient temperature, thus providing a stable clock signal for the charging chip.

2. The oscillation circuit for a charging chip according to claim 1, characterized in that, The power supply circuit (10) includes a bias circuit (101) and a current source circuit (102). The bias circuit (101) is connected to the current source circuit (102). The bias circuit (101) generates multiple bias voltages based on the power supply voltage and supplies them to the current source circuit (102) so that it can work stably. The current source circuit (102) is based on a negative feedback circuit structure, generates a charging current, outputs it to the oscillation output circuit (20), and provides a first bias voltage for the oscillation output circuit (20).

3. The oscillation circuit for a charging chip according to claim 2, characterized in that, The oscillation output circuit (20) includes a charging and discharging circuit (201) and a conversion circuit (202); The charging and discharging circuit (201) is connected to the conversion circuit (202). The charging and discharging circuit (201) periodically charges and discharges the capacitor C1 based on the feedback circuit structure, thereby generating a periodically changing voltage. The conversion circuit (202) converts the periodically changing voltage into a periodically changing level signal, and divides the level signal by two to generate a clock signal, which is output through port CLKS. Based on the periodically changing voltage generated in the charging and discharging circuit (201), the frequency of the clock signal output by the conversion circuit (202) can be adjusted by a temperature coefficient, so that the frequency of the clock signal is not affected by changes in ambient temperature.

4. The oscillation circuit for a charging chip according to claim 3, characterized in that, The charging and discharging circuit (201) includes MOSFET M26, MOSFET M27, MOSFET M28, capacitor C1, port IRCF, and port VBS; The source of MOSFET M26 is connected to power supply VDD, the gate of MOSFET M26 is connected to port IRCF, and the drain of MOSFET M26 is connected to the drain of MOSFET M27. The drain of MOSFET M27 is connected to the drain of MOSFET M26, the gate of MOSFET M27 is connected to port VBS, the upper end of the source capacitor C1 of MOSFET M27 is connected to ground, and the lower end of capacitor C1 is grounded. The drain of MOSFET M28 is connected to the source of MOSFET M27, the gate of MOSFET M28 is connected to the output of inverter NGT2, and the source of MOSFET M28 is grounded.

5. The oscillation circuit for a charging chip according to claim 4, characterized in that, The conversion circuit 202 includes MOSFETs M29, M30, M31, and M32, inverters NGT1 and NGT2, D flip-flop DFF1, and port CLKS; The source of MOSFET M29 is connected to power supply VDD, the gate of MOSFET M29 is connected to the output of inverter NGT1, and the drain of MOSFET M29 is connected to the drain of MOSFET M30. The drain of MOSFET M30 is connected to the drain of MOSFET M29, the gate of MOSFET M30 is connected to the output of inverter NGT2, and the source of MOSFET M30 is connected to the source of MOSFET M31. The source of MOSFET M31 is connected to the drain of MOSFET M26, the gate of MOSFET M31 is connected to the output of inverter NGT2, and the drain of MOSFET M31 is connected to the drain of MOSFET M32. The drain of MOSFET M32 is connected to the drain of MOSFET M31, the gate of MOSFET M32 is connected to the output of inverter NGT1, and the source of MOSFET M32 is grounded. The input of inverter NGT1 is connected to the source of MOSFET M30, the output of inverter NGT1 is connected to the input of inverter NGT2, the output of inverter NGT2 is connected to the CLK input of D flip-flop DFF1, the Q output of D flip-flop DFF1 is connected to port SCK, the Q' output of D flip-flop DFF1 is connected to the D input of D flip-flop DFF1, and the CLK input of D flip-flop DFF1 is connected to the gate of MOSFET M30.

6. A lithium battery charging chip with integrated MCU, comprising a main control module (2), a clock module (1), a charging control module (3), a power interface (4), a battery interface (5), and an external signal port (6), wherein the clock module (1) is connected to the main control module (2), the input terminal of the charging control module (3) is connected to the power interface (4), the output terminal is connected to the battery interface (5), the controlled terminal is connected to the main control module (2), and charging control is performed according to the signal from the main control module (2), and the external signal port (6) is connected to the main control module (2), characterized in that, The clock module (1) uses the oscillation circuit described in any one of claims 1-5 to provide a stable clock signal to the main control module (2).

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