Switching charger capable of accurately sensing small currents

Abstract

The application discloses a switching charger capable of accurately sensing small current. The first end of a first transistor and the first end of a second transistor are coupled with a system voltage. The second end of the first transistor and the first input end of an operational amplifier are connected with a battery. The first end of a third transistor is connected with the second end of the second transistor and the second input end of the operational amplifier. The control end of the third transistor is connected with the output end of the operational amplifier. The first end of a fourth transistor is connected with the second end of the third transistor. The first end of a fifth transistor is coupled with an input voltage. The control end of the first transistor and the control end of the fifth transistor are connected with a control circuit. The first end of a sixth transistor is connected with the second end of the fifth transistor.

Description

Technical Field

[0001] This invention relates to a switching charger, and more particularly to a switching charger capable of accurately sensing small currents. Background Technology

[0002] In recent years, with the advancement of technology, electronic products with various functions have been developed, not only meeting people's diverse needs but also integrating into everyone's daily life, making life more convenient. These electronic products are composed of various electronic components, and each component requires a different power supply voltage. In order for these diverse electronic products to operate normally, a switching charger is needed to convert the input voltage into an appropriate voltage for the electronic components. However, traditional switching chargers cannot accurately sense the charging current, especially small charging currents. Summary of the Invention

[0003] The technical problem this invention aims to solve is to provide a switching charger capable of accurately sensing small currents, addressing the shortcomings of conventional technologies. The charger includes a first current mirror, a first operational amplifier, a third transistor, a second current mirror, and a control circuit. The first current mirror includes multiple first transistors and a second transistor. The first terminal of each first transistor and the first terminal of each second transistor are coupled to the system voltage. The second terminal of each first transistor is connected to a battery. The first input terminal of the first operational amplifier is connected to the battery and obtains the battery voltage. The first terminal of the third transistor is connected to the second terminal of the second transistor and the second input terminal of the first operational amplifier. The control terminal of the third transistor is connected to the output terminal of the first operational amplifier. The second current mirror includes a fourth transistor, multiple fifth transistors, and multiple sixth transistors. The first terminal of the fourth transistor is connected to the second terminal of the third transistor and the control terminal of the fourth transistor. The second terminal of the fourth transistor is grounded. The first terminal of each fifth transistor is connected to the first terminal of a sensing resistor. The second terminal of the sensing resistor is coupled to the input voltage. The first terminals of the multiple sixth transistors are respectively connected to the second terminals of the multiple fifth transistors. The second terminals of each sixth transistor are grounded. The control terminal of each sixth transistor is connected to the control terminal of the fourth transistor. The control terminal of one of the plurality of first transistors is connected to the control terminal of a second transistor, and the control circuit is connected to the control terminals of the other plurality of first transistors and the control terminals of each fifth transistor. The control circuit selectively turns off the plurality of first transistors and the plurality of fifth transistors to adjust the value of the current flowing through the sensing resistor.

[0004] In one embodiment, the switching charger capable of accurately sensing small currents further includes a voltage selector. The input of the voltage selector is connected to the battery and coupled to the system voltage. The output of the voltage selector is connected to the fourth terminal of each of the first transistors and the fourth terminal of each of the second transistors. The voltage selector is configured to select the maximum of the system voltage and the battery voltage and output it to the fourth terminal of each of the first transistors and the fourth terminal of each of the second transistors.

[0005] In one embodiment, the switching charger capable of accurately sensing small currents further includes a reference resistor. A first terminal of the reference resistor is connected to a control circuit. A second terminal of the reference resistor is grounded. The control circuit selectively shuts down a plurality of first transistors and a plurality of fifth transistors based on the resistance value of the reference resistor.

[0006] In one embodiment, the switching charger capable of accurately sensing small currents further includes a reference current source. The reference current source is connected to a first terminal of a reference resistor. The reference current source provides a reference current. The control circuit selectively shuts down a plurality of first transistors and a plurality of fifth transistors based on the voltage obtained by multiplying the value of the reference current by the value of the reference resistor.

[0007] In one embodiment, the switching charger capable of accurately sensing small currents further includes a detection circuit. The detection circuit is connected to a control circuit and a first terminal of a reference resistor. The detection circuit is configured to detect the voltage or resistance value at the first terminal of the reference resistor and provide it to the control circuit.

[0008] In one embodiment, the control circuit is connected to the storage circuit. The control circuit selectively turns off a plurality of first transistors and a plurality of fifth transistors based on data provided by the storage circuit.

[0009] In one embodiment, the control circuit selectively shuts down a plurality of first transistors and a plurality of fifth transistors based on the battery charging current.

[0010] In one embodiment, the switching charger capable of accurately sensing small currents further includes a first amplifier. A first input terminal of the first amplifier is connected to a first terminal of a sensing resistor. A second input terminal of the first amplifier is coupled to a first reference voltage. The output terminal of the first amplifier is connected to the control terminals of each first transistor and the second transistor. The first amplifier is configured to compare the voltage at the first terminal of the sensing resistor with the first reference voltage to output an amplified signal to the control terminals of each first transistor and the second transistor.

[0011] In one embodiment, the switching charger capable of accurately sensing small currents further includes a first comparator. A first input terminal of the first comparator is coupled to the system voltage. A second input terminal of the first comparator is connected to the battery and obtains the battery voltage. The output terminal of the first comparator is connected to the input terminal of a control circuit.

[0012] In one embodiment, the second input terminal of the first comparator is connected to the first terminal of a voltage source. The second terminal of the voltage source is connected to a battery.

[0013] In one embodiment, the switching charger capable of accurately sensing small currents further includes multiple multiplexers. The first input terminal of each multiplexer is connected to the output terminal of a voltage selector. The second input terminals of the multiple multiplexers are respectively connected to the output terminals of a first amplifier. The output terminals of the multiple multiplexers are respectively connected to the control terminals of multiple first transistors. A control circuit is connected to the control terminals of each multiplexer. The control circuit controls the multiple multiplexers to select the maximum of the system voltage selected by the voltage selector and the battery voltage, or based on an amplified signal output by the first amplifier, to control the operation of the multiple first transistors respectively.

[0014] In one embodiment, the switching charger capable of accurately sensing small currents further includes a seventh transistor, an eighth transistor, and a second operational amplifier. The control terminal of the seventh transistor is connected to the control terminal of the fourth transistor. The first terminal of the seventh transistor is grounded. The first terminal of the eighth transistor is connected to the second terminal of the seventh transistor. The control terminal of the eighth transistor is connected to a control circuit. The first input terminal of the second operational amplifier is connected to the battery and obtains the battery's voltage. The output terminal of the second operational amplifier is connected to the second input terminal of the second operational amplifier and the second terminal of the eighth transistor.

[0015] In one embodiment, the switching charger capable of accurately sensing small currents further includes a main control circuit, a drive circuit, an upper bridge switch, and a lower bridge switch. The input terminal of the main control circuit is connected to the output terminal of the second operational amplifier. The input terminal of the drive circuit is connected to the output terminal of the main control circuit. The first terminal of the upper bridge switch is coupled to a shared voltage. The control terminal of the upper bridge switch is connected to the output terminal of the drive circuit. The first terminal of the lower bridge switch is connected to the second terminal of the upper bridge switch. The second terminal of the lower bridge switch is grounded. The control terminal of the lower bridge switch is connected to the output terminal of the drive circuit. The node between the first terminal of the lower bridge switch and the second terminal of the upper bridge switch is connected to the first terminal of an inductor. The second terminal of the inductor is grounded.

[0016] In one embodiment, the switching charger capable of accurately sensing small currents further includes a first resistor grounded. A first terminal of the first resistor is connected to the output of a second operational amplifier. A second terminal of the first resistor is connected to the second terminal of an eighth transistor.

[0017] In one embodiment, the switching charger capable of accurately sensing small currents further includes an error amplifier. A first input terminal of the error amplifier is connected to a second terminal of a first resistor. A second input terminal of the error amplifier is coupled to a second reference voltage.

[0018] In one embodiment, the switching charger capable of accurately sensing small currents further includes a voltage divider circuit. The voltage divider circuit includes a second resistor and a third resistor. A first terminal of the second resistor is connected to a second terminal of an inductor. A second terminal of the second resistor is connected to a first terminal of the third resistor. A second terminal of the third resistor is grounded. The voltage at the node between the second terminal of the second resistor and the first terminal of the third resistor serves as a second reference voltage.

[0019] In one embodiment, the switching charger capable of accurately sensing small currents further includes a second comparator. The first input of the second comparator is connected to the output of a ramp signal generator. The second input of the second comparator is connected to the output of an error amplifier. The output of the second comparator is connected to the input of the main control circuit.

[0020] In one embodiment, the switching charger capable of accurately sensing small currents further includes a third operational amplifier. A first input terminal of the third operational amplifier is connected to a node between the second terminal of the second resistor and the first terminal of the third resistor. A second input terminal of the third operational amplifier is coupled to a third reference voltage. The output terminal of the third operational amplifier is connected to the second input terminal of an error amplifier.

[0021] In one embodiment, the switching charger capable of accurately sensing small currents further includes a fourth resistor. A first terminal of the fourth resistor is connected to the output of a third operational amplifier. A second terminal of the fourth resistor is connected to the second input of an error amplifier.

[0022] As described above, this invention provides a switching charger capable of accurately sensing small currents. It selectively shuts down multiple first transistors and multiple fifth transistors to selectively change the ratio of the input current to the output current of the first current mirror and / or the ratio of the input current to the output current of the fifth current mirror, thereby adjusting the current value flowing through the sensing resistor. Specifically, it adjusts the current value of the sensing resistor, which is less than a current threshold, to a larger current value. This adjusted current value is used as the sensing current value. Furthermore, the difference between the system voltage and the battery voltage can be further adjusted according to the magnitude of the battery charging current, improving the charging efficiency of the switching charger. The smaller the proportion of the operational amplifier's offset voltage to the difference between the system voltage and the battery voltage, the smaller its impact on the sensing accuracy of the current, allowing the external processing circuit to accurately determine this sensing current value and perform appropriate operations accordingly.

[0023] To further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are for reference and illustration only and are not intended to limit the present invention. Attached Figure Description

[0024] Figure 1This is a circuit layout diagram of a switching charger capable of accurately sensing small currents according to the first embodiment of the present invention.

[0025] Figure 2 This is a circuit layout diagram of a switching charger capable of accurately sensing small currents according to a second embodiment of the present invention.

[0026] Figure 3 This is a circuit layout diagram of a switching charger capable of accurately sensing small currents according to a third embodiment of the present invention.

[0027] Figure 4 This is a circuit layout diagram of a switching charger capable of accurately sensing small currents according to the fourth embodiment of the present invention.

[0028] Figure 5 This is a circuit layout diagram of a switching charger capable of accurately sensing small currents according to the fifth embodiment of the present invention.

[0029] Figure 6 This is a schematic diagram of the voltage and current signals of a switching charger capable of accurately sensing small currents according to the first to fifth embodiments of the present invention.

[0030] Figure 7 This is a schematic diagram showing the charging current versus the resistance value of a reference resistor for the switching charger and the conventional switching charger according to the second and third embodiments of the present invention.

[0031] Figure 8 This is a schematic diagram showing the efficiency versus battery current curves of the switching charger and the conventional switching charger according to the first to fifth embodiments of the present invention. Detailed Implementation

[0032] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. Furthermore, the accompanying drawings of the present invention are for simple illustrative purposes only and are not depictions of actual dimensions, as stated in advance. The following embodiments will further describe the relevant technical content of the present invention in detail, but the disclosed content is not intended to limit the scope of protection of the present invention. In addition, the term "or" as used herein may, depending on the actual situation, include any combination of any one or more of the associated listed items.

[0033] Please see Figure 1 This is a circuit layout diagram of a switching charger capable of accurately sensing small currents according to the first embodiment of the present invention.

[0034] The switching charger of this invention may include a first current mirror M1, a control circuit 10, a first operational amplifier OPA1, a third transistor T3, a second current mirror M2, a voltage selector 40, and a sensing resistor Rsen, but this invention is not limited thereto.

[0035] The first current mirror M1 may include multiple first transistors T10 to T1n and a second transistor T2. The number of first transistors T11 to T1n included in the first current mirror M1 may depend on actual requirements. In this embodiment, all first transistors T10 to T1n have the same size as the second transistor T2, but the invention is not limited thereto.

[0036] The first terminal of each of the first transistors T10 to T1n and the first terminal of the second transistor T2 can be coupled to the system voltage Vsys. The second terminal of each of the first transistors T10 to T1n can be connected to a battery and receive the battery voltage Vbat provided by the battery. In other words, the second terminal of each of the first transistors T10 to T1n can be coupled to the battery voltage Vbat.

[0037] The first input terminal of the first operational amplifier OPA1, such as the non-inverting input terminal, can be connected to a battery and receive the battery voltage Vbat provided by the battery. The second input terminal of the first operational amplifier OPA1, such as the inverting input terminal, can be connected to the first terminal of the third transistor T3. The first terminal of the third transistor T3 can be connected to the second terminal of the second transistor T2. The control terminal of the third transistor T3 can be connected to the output terminal of the first operational amplifier OPA1. The first operational amplifier OPA1 amplifies the difference between the voltage at its first input terminal and the voltage at its second input terminal to output a first amplified signal to the control terminal of the third transistor T3.

[0038] Additionally, the second current mirror M2 may include a fourth transistor T4, multiple fifth transistors T51 to T5m, and multiple sixth transistors T61 to T6m. In this embodiment, the number of fifth transistors T51 to T5m is the same as the number of sixth transistors T61 to T6m, both being m, where m is an appropriate integer value, but the invention is not limited thereto. The number of fifth transistors T51 to T5m and sixth transistors T61 to T6m included in the second current mirror M2 may depend on actual requirements.

[0039] The first terminal of the fourth transistor T4 can be connected to the second terminal of the third transistor T3 and the control terminal of the fourth transistor T4. The second terminal of the fourth transistor T4 can be grounded. The first terminals of each of the fifth transistors T51 to T5m can be connected to the first terminal of the sensing resistor Rsen. The second terminal of the sensing resistor Rsen can be coupled to an input voltage.

[0040] The first terminals of multiple sixth transistors T61 to T6m can be connected to the second terminals of multiple fifth transistors T51 to T5m respectively. The second terminal of each sixth transistor T61 to T6m can be grounded. The control terminal of each sixth transistor T61 to T6m can be connected to the control terminal of the fourth transistor T4.

[0041] If necessary, the switching charger of this embodiment may further include a first amplifier AMP1. A first input terminal of the first amplifier AMP1, such as an inverting input terminal, may be connected to a first terminal of a sensing resistor Rsen. A second input terminal of the first amplifier AMP1, such as a non-inverting input terminal, may be coupled to a first reference voltage Vref1. The output terminal of the first amplifier AMP1 may be connected to the control terminals of each of the first transistors T10 to T1n and the control terminal of the second transistor T2.

[0042] The first amplifier AMP1 can amplify the difference between the voltage at the first terminal of the sensing resistor Rsen and the first reference voltage Vref1, so as to output an amplified signal to the control terminals of each first transistor T10 to T1n and the control terminal of the second transistor T2, so as to drive each first transistor T10 to T1n and the second transistor T2.

[0043] If necessary, the switching charger of this embodiment may further include multiple multiplexers MU1 to MUn. The first input terminal of each multiplexer MU1 to MUn can be connected to the output terminal of the voltage selector 40. The second input terminals of the multiple multiplexers MU1 to MUn can be respectively connected to the output terminal of the first amplifier AMP1. The output terminals of the multiple multiplexers MU1 to MUn can be respectively connected to the control terminals of the multiple first transistors T11 to T1n.

[0044] The input terminal of voltage selector 40 can be connected to a battery to receive the battery voltage Vbat, and can be coupled to the system voltage Vsys. The output terminal of voltage selector 40 can be connected to the fourth terminal of each of the first transistors T10 to T1n and the fourth terminal of the second transistor T2.

[0045] The voltage selector 40 can select the maximum of the system voltage Vsys and the battery voltage Vbat and output it to the fourth terminal of each of the first transistors T10 to T1n and the fourth terminal of the second transistor T2, so that each of the first transistors T10 to T1n and the second transistor T2 can be turned off normally.

[0046] It is worth noting that the voltage selector 40 can select the maximum of the system voltage Vsys and the battery voltage Vbat, and output it to the first input terminal of each multiplexer MU1 to MUn. The control circuit 10 can be connected to the control terminal of each multiplexer MU1 to MUn, and can control the multiple multiplexers MU1 to MUn to operate the multiple first transistors T11 to T1n respectively according to the maximum of the system voltage Vsys and the battery voltage Vbat selected by the voltage selector 40 or according to the amplified signal output by the first amplifier AMP1.

[0047] It is worth noting that in a conventional charger, all transistors in the current mirror remain on. However, in this embodiment, the output of the control circuit 10 can be connected to the control terminals of one or more of the first transistors T11 to T1n and the fifth transistors T51 to T5m. The control circuit 10 can selectively turn off the first transistors T11 to T1n and the fifth transistors T51 to T5m to adjust the value of the current flowing through the sensing resistor Rsen, as explained below.

[0048] If the voltage offset of the first operational amplifier OPA1 is not considered, the ratio of the input current of the first current mirror M1 to the output current of the first current mirror M1 is basically equal to the ratio of the number of first transistors T11 to T1n turned on to the number of second transistors T2.

[0049] When N first transistors T10 to T1n are turned on, the ratio of the input current flowing through the first transistors T10 to T1n to the output current flowing through the second transistor T2 is N:1. In other words, the output current flowing through the second transistor T2 is equal to the input current flowing through the first transistors T10 to T1n divided by N.

[0050] The number of first transistors T11 to T1n that are turned off depends on the magnitude of the battery charging current, for example, it is proportional to the battery charging current. The smaller the battery charging current (i.e., the input current flowing through the first transistors T10 to T1n), the more first transistors T11 to T1n are turned off by the control circuit 10, that is, the fewer first transistors T11 to T1n are turned on, making the aforementioned N value smaller, and thus making the output current flowing through the second transistor T2 larger.

[0051] The ratio of the input current to the output current of the second current mirror M2 is essentially equal to the ratio of the number of fourth transistors T4 to the number of fifth transistors T51 to T5m that are turned on. That is, when M fifth transistors T51 to T5m are turned on, the ratio of the input current flowing through the fourth transistor T4 to the output current flowing through the fifth transistors T51 to T5m is 1:M. In other words, the output current flowing through the fifth transistors T51 to T5m is equal to the input current flowing through the fourth transistor T4 multiplied by M.

[0052] Therefore, the smaller the battery charging current, the more fifth transistors T51 to T5m are turned on by the control circuit 10, so that the value of M is larger and the output current flowing through the fifth transistors T51 to T5m is larger to obtain a target current value.

[0053] If the voltage offset of the first operational amplifier OPA1 is not considered, the value of the current flowing through the sensing resistor Rsen is basically equal to the charging current of the battery (i.e. the input current flowing through the first transistor T10) divided by the above-mentioned N value, and then multiplied by the above-mentioned M value.

[0054] In other words, the control circuit 10 can selectively turn off one or more of the first transistors T11 to T1n of the first current mirror M1 based on the value of the battery charging current, for example, when the battery charging current is less than a charging current threshold, to adjust the ratio of the input current to the output current of the first current mirror M1. Alternatively, the control circuit 10 can selectively turn on one or more of the fifth transistors T51 to T5m of the second current mirror M2 based on the value of the battery charging current, to adjust the ratio of the input current to the output current of the second current mirror M2. In this way, the current flowing through the sensing resistor Rsen can be made higher than a sensing current threshold, allowing the external processing circuit to easily and accurately determine the magnitude of the current value of the sensing resistor Rsen and perform appropriate operations accordingly.

[0055] Conversely, when the battery charging current is greater than a charging current threshold, the control circuit 10 can keep all the first transistors T11 to T1n and the second transistor T2 contained in the first current mirror M1 on, and can selectively turn off all the fourth transistors T4, multiple fifth transistors T51 to T5m and multiple sixth transistors T61 to T6m contained in the second current mirror M2.

[0056] Please see Figure 2 This is a circuit layout diagram of a switching charger capable of accurately sensing small currents according to the second embodiment of the present invention. The similarities between the second embodiment and the first embodiment will not be repeated here.

[0057] The control circuit 10 of the swappable charger in this embodiment of the invention can be connected to the storage circuit 20 or other external circuits. The control circuit 10 can selectively turn off the first transistors T11 to T1n and the fifth transistors T51 to T5m based on the data provided by the storage circuit 20 or other external circuits.

[0058] Alternatively, the charger in this embodiment of the invention may include one or more of a detection circuit 30, a reference resistor RSF, and a reference current source ISF.

[0059] The first terminal of the reference resistor RSF can be connected to the control circuit 10 (through the detection circuit 30). The second terminal of the reference resistor RSF is grounded. The detection circuit 30 can be connected to the control circuit 10 and can also be connected to the first terminal of the reference resistor RSF. The control circuit 10 can directly obtain the voltage value of the first terminal of the reference resistor RSF, or obtain the resistance value of the reference resistor RSF detected by the detection circuit 30. The reference resistor RSF can be a fixed resistor or a variable resistor. The resistance value of the reference resistor RSF determines the charging current of the battery.

[0060] The first terminal of the reference resistor RSF can be connected to the reference current source ISF. The reference current source ISF can provide a reference current. The control circuit 10 can obtain the resistance value of the reference resistor RSF directly or through the detection circuit 30, and selectively turn off the first transistors T11 to T1n and the fifth transistors T51 to T5m based on the voltage obtained by multiplying the resistance value of the reference resistor RSF by the current value of the reference current source ISF.

[0061] Please see Figure 3 This is a circuit layout diagram of a switching charger capable of accurately sensing small currents according to the third embodiment of the present invention. The similarities between the third embodiment and the first embodiment are not repeated here. The difference lies in that the system voltage VSYS and the battery voltage VBAT are very close in this case.

[0062] The switching charger of this embodiment may further include a first comparator CMP1. A first input terminal of the first comparator CMP1, such as a non-inverting input terminal, may be coupled to the system voltage Vsys. A second input terminal of the first comparator CMP1, such as an inverting input terminal, may be connected to a battery and receive the battery voltage Vbat provided by the battery. The output terminal of the first comparator CMP1 may be connected to the input terminal of the control circuit 10.

[0063] If necessary, the switching charger of this embodiment may further include a voltage source SV. The voltage source SV may be disposed between the second input terminal of the first comparator CMP1 and the battery. Specifically, the second input terminal of the first comparator CMP1 may be connected to the first terminal of the voltage source SV, for example, the positive terminal. The second terminal of the voltage source SV, for example, the negative terminal, may be connected to the battery, i.e., coupled to the battery voltage Vbat.

[0064] Ideally, the voltage at the first input terminal of the first operational amplifier OPA1 should be equal to the voltage at its second input terminal. However, in reality, a non-ideal offset voltage is generated during the manufacturing process between the first and second input terminals of OPA1, causing the current flowing through the third transistor T3 to contain offset current. As a result, the ratio of the input current flowing through the first transistors T10 to T1n to the output current flowing through the second transistor T2 is not actually equal to the ratio of the number of first transistors T10 to T1n turned on to the number of second transistors T2 turned on. Furthermore, because the battery charging current is relatively small, the voltage drop across the first transistors T10 to T1n is relatively small. This non-ideal offset voltage of the first operational amplifier OPA1 prevents the voltage at the first and second input terminals from locking together, resulting in an incorrect ratio of the input current flowing through the first transistors T10 to T1n to the output current flowing through the second transistor T2, thus affecting the sensing accuracy.

[0065] Therefore, the first comparator CMP1 compares the system voltage Vsys with the battery voltage Vbat (plus the voltage of the voltage source SV) to output a first comparison signal to the control circuit 10. The control circuit 10 can selectively turn off the first transistors T10 to T1n of the first current mirror M1 and selectively turn off the fifth transistors T51 to T5m of the second current mirror M2 according to the first comparison signal.

[0066] When the difference between the battery charging voltage Vbat and the system voltage Vsys is smaller during battery charging, the control circuit 10 will turn off more of the first transistors T11 to T1n, reducing the number of first transistors T11 to T1n that are turned on. This results in a larger total resistance value after the resistors of the first transistors T10 to T1n in the first current mirror M1 are connected in parallel. Consequently, the voltage value obtained by multiplying the resistance value of the first transistor T10 by the current flowing through the first current mirror M1 (i.e., the battery charging current) is larger. As a result, the offset voltage of the first operational amplifier OPA1 accounts for a smaller proportion of the difference between the system voltage Sys and the battery voltage Vbat. In other words, the offset of the first operational amplifier OPA1 has a smaller impact on the sensing accuracy of the current of the sensing resistor Rsen.

[0067] Conversely, when the battery charging current is large, the control circuit 10 can turn on a larger number of first transistors T11 to T1n, so that the resistance of the switching charger (first current mirror M1) is low, resulting in a lower temperature and better charging efficiency for the mobile phone.

[0068] Please see Figure 4This is a circuit layout diagram of a switching charger capable of accurately sensing small currents according to the fourth embodiment of the present invention. The similarities between the fourth embodiment and the first embodiment will not be repeated here.

[0069] The charger in this embodiment of the invention may further include a seventh transistor T7, an eighth transistor T8, and a second operational amplifier OPA2.

[0070] The control terminal of the seventh transistor T7 can be connected to the control terminal of the fourth transistor T4. The first terminal of the seventh transistor T7 is grounded. The first terminal of the eighth transistor T8 can be connected to the second terminal of the seventh transistor T7. The control terminal of the eighth transistor T8 can be connected to the output terminal of the control circuit 10. The control circuit 10 can turn the eighth transistor T8 on or off.

[0071] The first input terminal of the second operational amplifier OPA2, such as the non-inverting input terminal, can be connected to a battery and receive the battery voltage Vbat provided by the battery. That is, the first input terminal of the second operational amplifier OPA2 can be coupled to the battery voltage Vbat. The second input terminal of the second operational amplifier OPA2, such as the inverting input terminal, can be connected to the output terminal of the second operational amplifier OPA2 and the second terminal of the eighth transistor T8.

[0072] The output of the second operational amplifier OPA2 can be connected to the first terminal of the first resistor R1. The second terminal of the first resistor R1 can be connected to the input of the main control circuit 100 and the second terminal of the eighth transistor T8. The second terminal of the eighth transistor T8 can be connected to the current source Ioff and receive the current supplied by the current source Ioff. The output of the main control circuit 100 can be connected to the input of the drive circuit 200. The output of the drive circuit 200 can be connected to the control terminal of the upper bridge switch HS via an inverter NT, and can also be connected to the control terminal of the lower bridge switch LS.

[0073] The first terminal of the upper bridge switch HS is coupled to the shared voltage PMID. The second terminal of the upper bridge switch HS can be connected to the first terminal of the lower bridge switch LS. The second terminal of the lower bridge switch LS is grounded. The node between the first terminal of the lower bridge switch LS and the second terminal of the upper bridge switch HS can be connected to the first terminal of the inductor L. The first terminal of the inductor L can be connected to the first terminal of the capacitor C. The second terminal of the capacitor C can be coupled to the input voltage Vg. The second terminal of the inductor L can be grounded (through the second resistor R2 and the third resistor R3).

[0074] If necessary, a diode Dd can be configured. The anode of diode Dd is coupled to the input voltage Vg, and the cathode of diode Dd is connected to the second terminal of capacitor C.

[0075] In this embodiment, the second operational amplifier OPA2 multiplies the difference between the battery voltage Vbat and the voltage at the second terminal of the eighth transistor T8 (that is, the difference between the induced current output by the second current mirror M2 and the current of the current source Ioff) by a gain and outputs a second amplified signal. The main control circuit 100, based on the second amplified signal received from the second operational amplifier OPA2, controls the drive circuit 200 to drive the upper bridge switch HS and the lower bridge switch LS to adjust the system voltage Vsys. This allows the difference between the system voltage Vsys and the battery voltage VBAT to be further adjusted according to the magnitude of the charging current, resulting in better battery charging efficiency.

[0076] Please see Figure 5 This is a circuit layout diagram of a switching charger capable of accurately sensing small currents according to the fifth embodiment of the present invention. The similarities between the fifth and fourth embodiments are not repeated here.

[0077] The charger of this invention embodiment may, depending on actual needs, further include one or more of the following: error amplifier ER, second comparator CMP2, third operational amplifiers OPA31 to OPA34, fourth operational amplifier OPA4, first resistor R1, switching component Q1, charging pump TR, diodes D31 to D32, fourth resistor R4, fifth resistor R5, second capacitor C2, third capacitor C3, fourth capacitor C4, and sixth resistor R6. This invention is not limited thereto.

[0078] The charge pump TR can be connected to the control terminal of the switching assembly Q1. The charge pump TR can provide power to the control terminal of the switching assembly Q1. The first terminal of the switching assembly Q1 can be coupled to the power supply voltage VBUS. The second terminal of the switching assembly Q1 can be connected to the first terminal of the upper bridge switch HS.

[0079] The first resistor R1 can be connected between the output terminal of the second operational amplifier OPA2 and the second terminal of the eighth transistor T8. Specifically, the first terminal of the first resistor R1 can be connected to the output terminal of the second operational amplifier OPA2, and the second terminal of the first resistor R1 can be connected to the second terminal of the eighth transistor T8.

[0080] The first input terminal of the error amplifier ER, such as the non-inverting input terminal, can be connected to the second terminal of the first resistor R1. If the first resistor R1 is omitted, the first input terminal of the error amplifier ER, such as the non-inverting input terminal, can be directly connected to the output terminal of the second operational amplifier OPA2. The second input terminal of the error amplifier ER, such as the inverting input terminal, can be coupled to a second reference voltage.

[0081] For example, the second input terminal of the error amplifier ER, such as the inverting input terminal, can be connected to the node between the second terminal of the second resistor R2 of the voltage divider circuit 50 and the first terminal of the third resistor R3 of the voltage divider circuit 50. The voltage at the node between the second terminal of the second resistor R2 and the first terminal of the third resistor R3 can be used as the aforementioned second reference voltage. The first terminal of the second resistor R2 is connected to the second terminal of the inductor L. The second terminal of the third resistor R3 is grounded.

[0082] If necessary, one or more third operational amplifiers OPA31 to OPA34 can be configured. The first input terminal of the third operational amplifier OPA31, such as the non-inverting input terminal, can be connected to the node between the second terminal of the second resistor R2 and the first terminal of the third resistor R3. The second input terminal of the third operational amplifier OPA31, such as the inverting input terminal, can be coupled to a third reference voltage Vcv, such as, but not limited to, the voltage of the first capacitor C1.

[0083] The third operational amplifier OPA31 can multiply the difference between the voltage at the node between the second terminal of the second resistor R2 and the first terminal of the third resistor R3 and the third reference voltage Vcv by a gain value to output a third amplified signal to the second input terminal, such as the inverting input terminal, of the error amplifier ER.

[0084] The inputs of other third operational amplifiers OPA32 to OPA34 can receive other voltage or current data from the switching charger (e.g., the capacitor current Icc of capacitor C1, the power supply voltage DPM, and the power supply current Icic, respectively), and output a third amplified signal to the second input of the error amplifier ER, such as the inverting input, based on the received data (and the reference voltage or reference current).

[0085] The first terminals (e.g., anodes) of multiple diodes D31 to D32 can be connected to the output terminals of multiple third operational amplifiers OPA31 to OPA34, respectively. The second terminals (e.g., cathodes) of each diode D31 to D32 can be connected to the first terminal of a fourth resistor R4. The second terminal of the fourth resistor R4 can be connected to the second input terminal (e.g., inverting input) of the error amplifier ER. The first terminal of a fifth resistor R5 can be connected to the first terminal of the fourth resistor R4. The second terminal of the fifth resistor R5 can be connected to the first terminal of a second capacitor C2. The second terminal of the second capacitor C2 can be connected to the second terminal of the fourth resistor R4.

[0086] The second input terminal of the error amplifier ER, for example, the inverting input terminal, can be connected to the first terminal of the third capacitor C3 and the first terminal of the sixth resistor R6. The output terminal of the error amplifier ER can be connected to the second terminal of the third capacitor C3 and the second terminal of the sixth resistor R6.

[0087] The error amplifier ER can output an error amplification signal EAO based on the difference between the voltage at the first input terminal and the voltage at the second input terminal of the error amplifier ER.

[0088] The first input terminal of the second comparator CMP2, such as the non-inverting input terminal, can be connected to the output terminal of a ramp signal generator, and the ramp signal RAMP can be received from this ramp signal generator.

[0089] The second input terminal of the second comparator CMP2, for example, the inverting input terminal, is connected to the output terminal of the error amplifier ER. If necessary, the second input terminal of the second comparator CMP2, for example, the inverting input terminal, can also be connected to the output terminal of the fourth operational amplifier OPA4. The output terminal of the second comparator CMP2 is connected to the input terminal of the main control circuit 100.

[0090] The first input terminal of the fourth operational amplifier OPA4, such as the non-inverting input terminal, can be connected to a threshold voltage Vch. The second input terminal of the fourth operational amplifier OPA4, such as the inverting input terminal, can be connected to the output terminal of the fourth operational amplifier OPA4. The fourth operational amplifier OPA4 can multiply the difference between the voltage at its first input terminal and the voltage at its second input terminal by a gain value to output a fourth amplified signal.

[0091] The second comparator CMP2 compares the ramp signal RAMP with the error amplification signal EAO of the error amplifier ER (or the fourth amplification signal of the fourth operational amplifier OPA4) to output a second comparison signal. The main control circuit 100, based on the second comparison signal (and a frequency signal from the frequency signal generator 300), controls the drive circuit to drive the upper bridge switch HS and the lower bridge switch LS to adjust the system voltage Vsys. This ensures that the system voltage Vsys is slightly higher than the battery voltage Vbat, making the proportion of the offset voltage of the first operational amplifier OPA1 relative to the difference between the system voltage Vsys and the battery voltage Vbat smaller. In other words, this minimizes the impact of the offset of the first operational amplifier OPA1 on the sensing accuracy of the current of the sensing resistor Rsen.

[0092] Please see Figure 6 This is a schematic diagram of the voltage and current signals of the switching charger capable of accurately sensing small currents according to the first to fifth embodiments of the present invention.

[0093] like Figure 6As shown, the switching charger of this embodiment can adjust the difference between the battery voltage Vbat and the system voltage Vsys based on the value of the battery charging current Ichg. When the battery charging current Ichg is small, the difference between the system voltage Vsys and the battery voltage Vbat is large. As the battery charging current Ichg gradually increases, the difference between the system voltage Vsys and the battery voltage Vbat gradually decreases to improve charging efficiency.

[0094] Please see Figure 7 This is a schematic diagram showing the charging current versus the resistance value of a reference resistor for the switching charger and the conventional switching charger in the second and third embodiments of the present invention.

[0095] For example, such as Figure 2 and Figure 3 The reference resistor RSF of the switching charger shown can be a variable resistor, just like the reference resistor of a traditional switching charger. For example... Figure 7 As shown, the charging current of the switching charger of the present invention can be adjusted according to the resistance value of the reference resistor RSF. Similarly, the charging current of a conventional switching charger can be adjusted according to the resistance value of the reference resistor of the conventional switching charger.

[0096] In a conventional switching charger, all transistors remain on. Curve C11 represents the charging current versus the resistance of the reference resistor in a conventional switching charger. Influenced by the +0.48mV offset voltage of the operational amplifier in the conventional switching charger, curve C11 is non-linear and fails to cross zero. Similarly, curve C13 represents the charging current versus the resistance of the reference resistor in a conventional switching charger. Influenced by the -0.48mV offset voltage of the operational amplifier in the conventional switching charger, curve C13 is non-linear and fails to cross zero.

[0097] Curve C12 represents the curve of the charging current of the switching charger in this embodiment of the invention versus the resistance of the reference resistor RSF. It is linear and passes through zero, completely unaffected by the offset voltage of the operational amplifier. Clearly, as... Figure 2 and Figure 3 The switching charger of the present invention shown can switch the first transistor T10 to T1n of the first current mirror M1 according to the resistance value of the reference resistor RSF, so as to precisely adjust the charging current value of the switching charger.

[0098] Please see Figure 8 This is a schematic diagram showing the efficiency versus battery current curves of the switching charger and the conventional switching charger in the first to fifth embodiments of the present invention.

[0099] In the switching charger of the present invention, the first transistor T10 to T1n of the first current mirror M1 can be selectively switched according to the value of the charging current of the battery of the switching charger, so as to adjust the resistance value of the first current mirror M1. Furthermore, according to the magnitude of the charging current, the detection current output by the second current mirror M2 is subtracted from the current of the current source Ioff, thereby finely adjusting the difference between the system voltage Vsys and the battery voltage Vbat.

[0100] In contrast, in a conventional switching charger, all transistors in the current mirror are maintained.

[0101] like Figure 8 As shown, curve C21 represents the efficiency of the switching charger of this invention versus battery current, while curve C22 represents the efficiency of a conventional switching charger versus battery current. Clearly, because the difference between the system voltage Vsys and the battery voltage Vbat can be further adjusted according to the magnitude of the charging current, the switching charger of this invention has higher efficiency.

[0102] In summary, this invention provides a switching charger capable of accurately sensing small currents. It selectively shuts down multiple first transistors and multiple fifth transistors to selectively change the ratio of the input current to the output current of the first current mirror and / or the ratio of the input current to the output current of the fifth current mirror, thereby adjusting the current value flowing through the sensing resistor. Specifically, it adjusts the current value of the sensing resistor, which is below a current threshold, to a larger current value, and the adjusted current value is used as the sensing current value. Furthermore, the difference between the system voltage and the battery voltage can be further adjusted according to the magnitude of the battery charging current, improving the charging efficiency of the switching charger. The smaller the proportion of the operational amplifier's offset voltage to the difference between the system voltage and the battery voltage, the less impact it has on the accuracy of the sensing current, allowing the external processing circuit to accurately determine this sensing current value and perform appropriate operations accordingly.

[0103] The above-disclosed content is only a preferred embodiment of the present invention and is not intended to limit the claims of the present invention. Therefore, all equivalent technical changes made based on the description and drawings of the present invention are included in the claims of the present invention.

Claims

1. A switching charger capable of accurately sensing small currents, characterized in that, The switching charger includes: A first current mirror includes a plurality of first transistors and a second transistor, wherein a first terminal of each first transistor and a first terminal of each second transistor are coupled to a system voltage, and a second terminal of each first transistor is connected to a battery. A first operational amplifier, wherein the first input terminal of the first operational amplifier is connected to the battery and obtains the voltage of the battery; The third transistor has a first terminal connected to the second terminal of the second transistor and the second input terminal of the first operational amplifier, and a control terminal connected to the output terminal of the first operational amplifier. The second current mirror includes: A fourth transistor, wherein the first terminal of the fourth transistor is connected to the second terminal of the third transistor and the control terminal of the fourth transistor, and the second terminal of the fourth transistor is grounded; A plurality of fifth transistors, wherein the first terminal of each fifth transistor is connected to the first terminal of a sensing resistor, and the second terminal of the sensing resistor is coupled to an input voltage; as well as A plurality of sixth transistors, wherein the first terminals of the plurality of sixth transistors are respectively connected to the second terminals of the plurality of fifth transistors, the second terminals of each sixth transistor are grounded, and the control terminal of the sixth transistor is connected to the control terminal of the fourth transistor; as well as A control circuit, wherein the control terminal of one of the plurality of first transistors is connected to the control terminal of the second transistor, and the control circuit is connected to the control terminals of the other plurality of first transistors and the control terminals of each of the fifth transistors; The control circuit selectively shuts down the plurality of first transistors and the plurality of fifth transistors to adjust the value of the current flowing through the sensing resistor.

2. The switching charger capable of accurately sensing small currents according to claim 1, characterized in that, The switching charger also includes a reference resistor, a first end of which is connected to the control circuit and a second end of which is grounded. The control circuit selectively shuts down the plurality of first transistors and the plurality of fifth transistors based on the resistance value of the reference resistor.

3. The switching charger capable of accurately sensing small currents according to claim 2, characterized in that, The switching charger also includes a reference current source connected to a first terminal of the reference resistor, the reference current source providing a reference current to the reference resistor, and the control circuit selectively turning off the plurality of first transistors and the plurality of fifth transistors based on the voltage obtained by multiplying the reference current by the reference resistor.

4. The switching charger capable of accurately sensing small currents according to claim 3, characterized in that, The switching charger further includes a detection circuit connected to the control circuit and a first terminal of the reference resistor, configured to detect the voltage at the first terminal of the reference resistor provided to the control circuit.

5. The switching charger capable of accurately sensing small currents according to claim 1, characterized in that, The control circuit is connected to the storage circuit and selectively shuts down the plurality of first transistors and the plurality of fifth transistors based on data provided by the storage circuit.

6. The switching charger capable of accurately sensing small currents according to claim 1, characterized in that, The control circuit selectively shuts down the plurality of first transistors and the plurality of fifth transistors based on the charging current of the battery.

7. The switching charger capable of accurately sensing small currents according to claim 1, characterized in that, The switching charger also includes a voltage selector, the input of which is connected to the battery and coupled to the system voltage, and the output of which is connected to the fourth terminal of each of the first transistors and the fourth terminal of the second transistor. The voltage selector is configured to select the maximum of the system voltage and the battery voltage to output to the fourth terminal of each of the first transistors and the fourth terminal of the second transistor.

8. The switching charger capable of accurately sensing small currents according to claim 7, characterized in that, The switching charger further includes a first amplifier, the first input terminal of the first amplifier is connected to the first terminal of the sensing resistor, the second input terminal of the first amplifier is coupled to a first reference voltage, and the output terminal of the first amplifier is connected to the control terminal of each of the first transistors and the control terminal of the second transistor. The first amplifier is configured to compare the voltage at the first terminal of the sensing resistor with the first reference voltage to output an amplified signal to the control terminals of the first transistor and the second transistor.

9. The switching charger capable of accurately sensing small currents according to claim 8, characterized in that, The switching charger further includes a first comparator, a first input terminal of which is coupled to the system voltage, a second input terminal of which is connected to the battery and obtains the battery voltage, and an output terminal of which is connected to the input terminal of the control circuit.

10. The switching charger capable of accurately sensing small currents according to claim 9, characterized in that, The second input terminal of the first comparator is connected to the first terminal of the voltage source, and the second terminal of the voltage source is connected to the battery.

11. The switching charger capable of accurately sensing small currents according to claim 8, characterized in that, The switching charger also includes: Multiple multiplexers are provided, with the first input terminal of each multiplexer connected to the output terminal of the voltage selector, the second input terminals of each multiple multiplexer connected to the output terminal of the first amplifier, and the output terminals of each multiple multiplexer connected to the control terminals of the multiple first transistors. The control circuit is connected to the control terminal of each of the multiplexers and controls the multiple multiplexers to select the maximum of the system voltage selected by the voltage selector and the battery voltage, or to select an amplified signal output by the first amplifier, so as to control the operation of the multiple first transistors respectively.

12. The switching charger capable of accurately sensing small currents according to claim 1, characterized in that, The switching charger also includes: The seventh transistor has its control terminal connected to the control terminal of the fourth transistor, and its first terminal is grounded. The eighth transistor has its first terminal connected to the second terminal of the seventh transistor, and its control terminal connected to the control circuit. as well as The second operational amplifier has its first input terminal connected to the battery and obtaining the battery's voltage, and its output terminal connected to its second input terminal and the second terminal of the eighth transistor.

13. The switching charger capable of accurately sensing small currents according to claim 12, characterized in that, The switching charger also includes: A main control circuit, wherein the input terminal of the main control circuit is connected to the output terminal of the second operational amplifier; A driving circuit, wherein the input terminal of the driving circuit is connected to the output terminal of the main control circuit; An upper bridge switch, wherein the first terminal of the upper bridge switch is coupled to a shared voltage, and the control terminal of the upper bridge switch is connected to the output terminal of the drive circuit; as well as A lower bridge switch is provided, the first end of which is connected to the second end of the upper bridge switch, the second end of which is grounded, and the control end of the lower bridge switch is connected to the output end of the drive circuit. The node between the first end of the lower bridge switch and the second end of the upper bridge switch is connected to the first end of an inductor, and the second end of the inductor is grounded.

14. The switching charger capable of accurately sensing small currents according to claim 13, characterized in that, The switching charger also includes: A first resistor, the first end of which is connected to the output terminal of the second operational amplifier, and the second end of which is connected to the second terminal of the eighth transistor.

15. The switching charger capable of accurately sensing small currents according to claim 14, characterized in that, The switching charger also includes: An error amplifier, wherein the first input terminal of the error amplifier is connected to the second terminal of the first resistor, and the second input terminal of the error amplifier is coupled to a second reference voltage.

16. The switching charger capable of accurately sensing small currents according to claim 15, characterized in that, The switching charger also includes: The voltage divider circuit includes a second resistor and a third resistor. The first end of the second resistor is connected to the second end of the inductor, the second end of the second resistor is connected to the first end of the third resistor, and the second end of the third resistor is grounded. The voltage at the node between the second end of the second resistor and the first end of the third resistor is used as the second reference voltage.

17. The switching charger capable of accurately sensing small currents according to claim 16, characterized in that, The switching charger also includes: The second comparator has its first input connected to the output of the ramp signal generator, its second input connected to the output of the error amplifier, and its output connected to the input of the main control circuit.

18. The switching charger capable of accurately sensing small currents according to claim 17, characterized in that, The switching charger also includes: A third operational amplifier has its first input terminal connected to the node between the second terminal of the second resistor and the first terminal of the third resistor, its second input terminal coupled to a third reference voltage, and its output terminal connected to the second input terminal of the error amplifier.

19. The switching charger capable of accurately sensing small currents according to claim 18, characterized in that, The switching charger also includes: The fourth resistor has its first end connected to the output of the third operational amplifier and its second end connected to the second input of the error amplifier.

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