Current sampling circuit, power management chip and electronic device

Abstract

This application discloses a current sampling circuit, a power management chip, and an electronic device. The current sampling circuit is used to detect the average current of two alternately conducting low-side power transistors. It includes a displacement switch, a first operational amplifier circuit, and a current sensing transistor. The non-inverting input of the first operational amplifier circuit is alternately connected to the sources of the two low-side power transistors through the displacement switch. The inverting input of the first operational amplifier circuit is connected to the current sensing transistor. The output of the first operational amplifier circuit is connected to the output of the current sampling circuit. The current sensing transistor is also connected to the output of the current sampling circuit and ground, respectively. The current sensing transistor and the low-side power transistors are of the same type, and their on-resistances are proportional. This current sampling circuit can perform non-destructive testing of the low-side power transistors of a power management chip.

Description

Technical Field

[0001] This application belongs to the field of power management chip technology, specifically relating to a current sampling circuit, a power management chip, and an electronic device. Background Technology

[0002] In the field of power management chips, since losses cannot be completely avoided, chips will experience temperature increases during use, leading to decreased chip efficiency or even functional failure. As the chip's usage time increases, the efficiency of the power devices on the chip will also decrease. Therefore, it is necessary to determine the real-time current of the power devices to achieve more effective and accurate power management.

[0003] Traditional current sensing methods mostly use series resistors, measuring the voltage across the sampling resistor to reflect the current value. However, this method introduces additional power loss and voltage margin issues, especially for high current sensing. Therefore, in the increasingly demanding design of high-efficiency, fully integrated power management chips, traditional current sensing methods are becoming increasingly inadequate.

[0004] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0005] This application proposes a current sampling circuit, a power management chip, and an electronic device that can perform non-destructive testing on the low-side power transistors of the power management chip.

[0006] The first aspect of this application provides a current sampling circuit for detecting the average current of two alternately conducting low-side power transistors, including a displacement switch, a first operational amplifier circuit, and a current detection transistor; The non-inverting input terminal of the first operational amplifier circuit is alternately connected to the sources of the two low-side power transistors through the displacement switch; the inverting input terminal of the first operational amplifier circuit is connected to the current sensing transistor; and the output terminal of the first operational amplifier circuit is connected to the output terminal of the current sampling circuit. The current sensing transistor is also connected to the output terminal and the ground terminal of the current sampling circuit, and the current sensing transistor and the low-side power transistor are the same type of transistor, with their on-resistances being proportional.

[0007] In some optional embodiments, the first operational amplifier circuit includes a sampling power transistor and a first current mirror connected in series, the drain of the sampling power transistor being connected to the sampling power transistor, and the source of the sampling power transistor being grounded; The sampling power transistor and the current detection transistor are transistors of the same size.

[0008] In some optional embodiments, a second current mirror is also included, the input of which is connected to the output of the first operational amplifier circuit and the current detection transistor, respectively, and the output of the second current mirror is grounded and connected to the output of the current sampling circuit.

[0009] In some optional embodiments, a control power transistor is also included, the gate of which is connected to the output of the first operational amplifier circuit, the source of which is connected to the second current mirror, and the drain of which is connected to the current detection transistor.

[0010] In some optional embodiments, a first low-pass filter component is also included, which is disposed between the displacement switch and the first operational amplifier circuit.

[0011] In some alternative embodiments, a bias voltage source is also included, which is disposed between the inverting input of the first operational amplifier circuit and the current sensing transistor.

[0012] In some optional embodiments, a second operational amplifier circuit is also included, wherein the non-inverting input of the second operational amplifier circuit is connected to the output of the second current mirror, the inverting input and output are shorted together, and connected to the output of the current sampling circuit.

[0013] In some optional embodiments, a second low-pass filter component is also included, which is disposed between the second current mirror and the second operational amplifier circuit.

[0014] An embodiment of the second aspect of this application provides a power management chip that integrates the current sampling circuit described in the first aspect.

[0015] An embodiment of the third aspect of this application provides an electronic device including the power management chip described in the second aspect.

[0016] The technical solutions provided in this application embodiment have at least the following technical effects or advantages: The current sampling circuit provided in this application embodiment can synchronously and alternately sample two alternately conducting low-side power transistors by replacing the switch, thereby enabling real-time acquisition of the low-side power transistors on the left and right half-bridges. Figure 1The real-time current (not shown) is then measured. The current is then transmitted through a first operational amplifier circuit (APM1) and a current-sensing transistor connected to the inverting input of APM1. Since the non-inverting input of APM1 is connected to the low-side power transistor, based on the virtual short characteristic of the operational amplifier circuit (the voltage at the non-inverting input equals the voltage at the inverting input), the measured real-time current can be proportionally replicated onto the current-sensing transistor. This means that the current-sensing transistor can generate a DC current proportional to the average inductor current on the low-side power transistor. By detecting the current flowing through this current-sensing transistor, the real-time current of the low-side power transistor can be determined. Attached Figure Description

[0017] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A schematic diagram of the framework structure of a current sampling circuit provided in an embodiment of this application is shown; Figure 2 A schematic diagram of the structure of a first operational amplifier circuit provided in an embodiment of this application is shown; Figure 3 A schematic diagram of the specific structure of a current sampling circuit provided in an embodiment of this application is shown. Detailed Implementation

[0018] Exemplary embodiments of this application will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of this application are shown in the drawings, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this application and to fully convey the scope of this application to those skilled in the art.

[0019] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application shall have the ordinary meaning as understood by one of ordinary skill in the art to which this application pertains.

[0020] The following explains some of the technical terms used in this application.

[0021] Power management chips are a general term for integrated circuits that are responsible for the conversion, distribution, detection, and monitoring of electrical energy in electronic devices.

[0022] Low-side power transistor: In a bridge or half-bridge circuit, it is a switching transistor connected to ground (or the negative terminal of the power supply). In a synchronous rectification Buck circuit, it is a MOSFET that replaces the freewheeling diode and can also be called a "synchronous rectifier transistor" or "lower-side transistor".

[0023] Average inductor current: The average current flowing through the inductor under steady-state operation of the switching power supply. In this application, it refers to the average current flowing through (two) low-side power transistors per unit time.

[0024] In related technologies, besides the traditional current detection method that uses series resistance to measure the voltage across a sampling resistor to reflect the current value, current detection can also be achieved using current transformers and Hall effect sensors. However, when using a current transformer to detect current, it is difficult for the transformer to detect the DC component; when using a Hall effect sensor to detect current, the Hall effect sensor is susceptible to temperature fluctuations and is also relatively expensive. Given these shortcomings, existing current detection methods are increasingly unable to meet the requirements of power management chip designs that increasingly demand high efficiency and full integration.

[0025] To address the aforementioned problems, this application provides a current sampling circuit for a power management chip. This current sampling circuit is used to detect the average current of two alternately conducting low-side power transistors in a half-bridge or bridge circuit. Please refer to... Figure 1 This is a schematic diagram of the framework structure of the current sampling circuit provided in the embodiments of this application, as shown below. Figure 1 As shown, the current sampling circuit includes a displacement switch, a first operational amplifier circuit (APM1), and a current sensing transistor. The non-inverting input of the first operational amplifier circuit (APM1) is alternately connected to the sources of the two low-side power transistors via the displacement switch. The inverting input of the first operational amplifier circuit (APM1) is connected to the current sensing transistor. The output of the first operational amplifier circuit (APM1) is connected to the output of the current sampling circuit. The current sensing transistor is also connected to the output of the current sampling circuit and to ground. The current sensing transistor and the low-side power transistors are of the same type, and their on-resistances are proportional.

[0026] The current sampling circuit provided in this embodiment can synchronously and alternately sample two alternately conducting low-side power transistors by means of a replacement switch, thereby enabling real-time acquisition of the low-side power transistors on both the left and right half-bridges. Figure 1The real-time current (not shown) is then measured. The current is then transmitted through a first operational amplifier circuit (APM1) and a current-sensing transistor connected to the inverting input of APM1. Since the non-inverting input of APM1 is connected to the low-side power transistor, based on the virtual short characteristic of the operational amplifier circuit (the voltage at the non-inverting input equals the voltage at the inverting input), the measured real-time current can be proportionally replicated onto the current-sensing transistor. This means that the current-sensing transistor can generate a DC current proportional to the average inductor current on the low-side power transistor. By detecting the current flowing through this current-sensing transistor, the real-time current of the low-side power transistor can be determined.

[0027] It is understood that the two alternately conducting low-side power transistors mentioned above are of the same type and specifications, and both low-side power transistors are configured with a common gate and common source with the current sensing transistor. The current sensing transistor may include one or more power transistors, which can be set according to actual needs; this embodiment does not make specific limitations in this regard. The ground terminal mentioned above is consistent with the ground terminal of the low-side power transistors, and can be power ground or analog ground; this embodiment does not make specific limitations in this regard.

[0028] It should be noted that this embodiment does not specifically limit the structure of the above-mentioned replacement switch, the first operational amplifier circuit APM1, and the current detection transistor, as long as they can achieve the corresponding functions.

[0029] Specifically, such as Figure 1 As shown, the substitution switch may include two single-pole single-throw (SPS) switches, SW1 and SW2. Each SPS is independently connected to one of the two low-side power transistors. Closing one SPS allows for the acquisition of the current of the corresponding low-side power transistor. Thus, by controlling the closing and opening times of the two SPS switches, the switches can be alternately closed at the same frequency as the two low-side power transistors, enabling synchronous alternating sampling of the two low-side power transistors.

[0030] like Figure 2 As shown, the first operational amplifier circuit APM1 may include a sampling power transistor M1 connected in series and a first current mirror. The drain of the sampling power transistor is connected to the sampling power transistor, and the source of the sampling power transistor is grounded.

[0031] The sampling power transistor and the current sensing transistor are of the same size, meaning they have the same on-resistance. Due to the virtual short characteristic of the operational amplifier, their currents are also the same when the same voltage is applied.

[0032] Furthermore, such as Figure 2 As shown, the first operational amplifier circuit APM1 may also include a series of MOSFETs to form an error amplifier and generate an offset voltage. The types and connections of the MOSFETs may be, but are not limited to, as shown below. Figure 2 As shown. The first current mirror provides a reference bias current for the first operational amplifier circuit APM1 and uses a PMOS differential input pair (INP / INN). It can also be configured with an active load and a current mirror to amplify the signal gain, etc.

[0033] In this embodiment, utilizing the virtual short characteristic of the input terminal of the first operational amplifier circuit AMP1, by setting the sampling power transistor M1 and the first current mirror, the inverting input terminal INP and the non-inverting input terminal INN can generate an offset voltage, that is, the current I1 generated by the first current mirror and the impedance R of the sampling power transistor are equal. M1 The product of M1 and MN1. Since M1 is exactly the same as the current sensing transistor MN1, the adjustable current I1 will also be applied to the proportionally related low-side power transistor current sampled by the current sensing transistor MN1, thereby generating an adjustable cutoff voltage on the output voltage.

[0034] Furthermore, a first low-pass filter component can be provided between the displacement switch and the first operational amplifier circuit AMP1. In this embodiment, the voltage signal entering the current sampling circuit passes through the first low-pass filter and is integrated on the capacitor to obtain a new voltage signal that is proportional to the average inductor current (ILavg), which is the average inductor current multiplied by the on-resistance of the low-side power transistor.

[0035] Specifically, such as Figure 2 As shown, the first low-pass filter component may include, but is not limited to, resistive devices and capacitors, wherein the capacitor component is also connected to power ground.

[0036] In some alternative embodiments, the current sampling circuit may further include a bias voltage source disposed between the inverting input of the first operational amplifier circuit APM1 and the current sensing transistor.

[0037] In this embodiment, a bias voltage source is provided to provide a common-mode boost voltage to the first operational amplifier circuit AMP1, preventing the input or output of the first operational amplifier circuit AMP1 from being grounded, which would cause the acquired data to be distorted.

[0038] In some other alternative embodiments, such as Figure 3 As shown, the current sampling circuit may further include a second current mirror. The input terminal of the second current mirror is connected to the output terminal of the first operational amplifier circuit and the current detection transistor, respectively. The output terminal of the second current mirror is grounded and connected to the output terminal of the current sampling circuit.

[0039] In this embodiment, when both the current sensing transistor and the low-side power transistor are connected to power ground, the power ground exhibits significant noise at high currents, affecting the accuracy of subsequent power calculations. By setting a second current mirror, the noisy power ground can be replaced with a cleaner analog ground, resulting in a cleaner analog signal and more accurate calculation results. Simultaneously, the proportionally related current mirror can further amplify and reduce the current I1 collected by the current sensing transistor MN1 as needed, adapting to a wider range of output requirements. Furthermore, the current through the second current mirror multiplied by the corresponding resistor represents the output voltage of the current sampling circuit. Therefore, by detecting the output voltage of this current sampling circuit, the average inductor current on the low-side power transistor can be quickly calculated.

[0040] In some alternative embodiments, the current sampling circuit may further include a control power transistor, the gate of which is connected to the output of the first operational amplifier circuit APM1, the source of which is connected to the second current mirror, and the drain of which is connected to the current detection transistor. Thus, the connection of the second current mirror can be controlled by the control power transistor, forming redundant protection and preventing large currents from flowing back to the low-side power transistor, making the current sampling circuit more reliable.

[0041] Specifically, the aforementioned control power transistor can be an NMOS transistor, and the two MOS transistors constituting the second current mirror can be PMOS transistors to achieve current amplification.

[0042] In some other alternative embodiments, such as Figure 3 As shown, the current sampling circuit may further include a second low-pass filter component and some resistors disposed between the second current mirror and the output terminal of the current sampling circuit. The second low-pass filter component is disposed between the current mirror and the second operational amplifier circuit APM2.

[0043] In this embodiment, by setting a resistive element, the current output by the current mirror can be converted into a voltage. That is, the current generated by the second current mirror flows through a series of zero-temperature coefficient resistors to obtain a voltage signal that is independent of temperature and only related to the average inductor current. The current output by the current mirror can be filtered again by a dual low-pass filter component to suppress channel switching glitches.

[0044] In some alternative embodiments, the current sampling circuit may further include a second operational amplifier circuit APM2, wherein the non-inverting input of the second operational amplifier circuit APM2 is connected to the output of the current mirror, and the inverting input and output are shorted and connected to the output of the current sampling circuit.

[0045] In this embodiment, by adding a second operational amplifier circuit APM2 to the output terminal of the current sampling circuit, the driving capability of the current sampling circuit can be improved, and a better voltage output effect can be achieved.

[0046] In another specific embodiment, combined with Figure 2 and Figure 3 As shown, the specific solutions and principles of the embodiments of this disclosure will be described in detail below: During normal chip operation, the low-side power transistors of the left and right half-bridges alternately flow current. This design synchronously and alternately samples the SW voltage when the left and right low-side power transistors are turned on. This voltage signal passes through a low-pass filter and is integrated across a capacitor to obtain a voltage signal proportional to the average inductor current (ILavg), which is the average inductor current multiplied by the on-resistance of the low-side power transistor. This voltage signal then passes through a signal amplifier composed of AMP1. A series of power transistors of the same type, proportional to the low-side power transistors (the ratio is defined as K), are used. The voltage at this power transistor generates a current of ILavg / K. The corresponding ground is still the same as the power stage ground. Power grounds have very high noise at high currents. To ensure the obtained analog signal can be used for power calculations, a current mirror composed of M1 and M2 is used to replace the ground with a cleaner analog ground. Simultaneously, the proportional current mirror can further amplify and reduce the previously obtained current as needed. The generated current then flows through a series of zero-temperature coefficient resistors to obtain a voltage signal that is independent of temperature and only related to the average inductor current. Due to the large size of the chip in this application, an amplification buffer (e.g., but not limited to) can be added to the output. Figure 2 The second operational amplifier circuit (AMP2) in the circuit can improve the driving capability.

[0047] To ensure consistency in mass-produced products, trim (adjustable) design is also necessary. In this design, AMP1 is designed as an operational amplifier with a built-in offset voltage. The operational amplifier uses a sampling power transistor M1 of the same size as the current sampling transistor and a cluster of adjustable current mirrors I1 to generate an adjustable offset voltage. By utilizing the virtual short characteristic of the operational amplifier input, the controllable current can be added to or subtracted from the sampling current to achieve the function of trimming the output voltage.

[0048] Based on the same concept as the current sampling circuit described above, this embodiment also provides a power management chip that integrates the aforementioned current sampling circuit.

[0049] The power management chip provided in this embodiment is based on the same concept as the current sampling circuit described above. Therefore, it can at least achieve the beneficial effects that the current sampling circuit can achieve. Furthermore, any implementation of the current sampling circuit can be applied to the chip provided in this embodiment, and will not be described in detail here.

[0050] Based on the same concept as the current sampling circuit described above, this embodiment also provides an electronic device, including the power management chip described above.

[0051] The electronic device chip provided in this embodiment is based on the same concept as the current sampling circuit described above. Therefore, it can at least achieve the beneficial effects that the current sampling circuit can achieve. Furthermore, any implementation of the current sampling circuit described above can be applied to the chip provided in this embodiment, and will not be described in detail here.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A current sampling circuit, characterized by, The application discloses a current sampling circuit for detecting the average current of two low-side power transistors which are alternately turned on, and comprises a replacement switch, a first operational amplifier circuit and a current detection transistor. The non-inverting input terminal of the first operational amplifier circuit is alternately connected with the source of the two low-side power transistors through the replacement switch, the inverting input terminal of the first operational amplifier circuit is connected with the current detection transistor, and the output terminal of the first operational amplifier circuit is connected with the output terminal of the current sampling circuit. The current detection transistor is also connected with the output terminal and the ground terminal of the current sampling circuit respectively, and the current detection transistor and the low-side power transistor are the same type of transistors, and the on-resistance of the two transistors is in proportional relationship.

2. The current sampling circuit of claim 1, wherein, The first operational amplifier circuit comprises a sampling power transistor and a first current mirror connected in series, the drain of the sampling power transistor is connected with the sampling power transistor, and the source of the sampling power transistor is grounded. The sampling power transistor and the current detection transistor are the same size of transistors.

3. The current sampling circuit of claim 1, wherein, The second current mirror is also connected with the output terminal of the first operational amplifier circuit and the current detection transistor respectively, and the output terminal of the second current mirror is connected with the output terminal of the current sampling circuit and grounded respectively.

4. The current sampling circuit of claim 3, wherein, The control power transistor is also connected with the output terminal of the first operational amplifier circuit, the second current mirror and the current detection transistor.

5. The current sampling circuit of any one of claims 1-4, wherein, The first low-pass filter assembly is arranged between the replacement switch and the first operational amplifier circuit.

6. The current sampling circuit of any one of claims 1-4, wherein, The bias voltage source is arranged between the inverting input terminal of the first operational amplifier circuit and the current detection transistor.

7. The current sampling circuit of claim 3 or 4, wherein, The second operational amplifier circuit is also connected with the output terminal of the second current mirror, and the inverting input terminal and the output terminal of the second operational amplifier circuit are short-circuited and connected with the output terminal of the current sampling circuit.

8. The current sampling circuit of any of claims 2-4, wherein, The second low-pass filter assembly is arranged between the second current mirror and the second operational amplifier circuit.

9. A power management chip, characterized by, The current sampling circuit is integrated on the substrate.

10. An electronic device, comprising: The power management chip comprises the current sampling circuit.

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