High-precision current detection circuit

Abstract

The utility model discloses a high-precision current detection circuit, belongs to the technical field of integrated circuits, and solves the problem of accurate sampling and detection of inductive current. Comprising a current sampling circuit of which the input end is electrically connected, one end of the output end is grounded, the other end of the output end is connected with a switching power supply chip, and the current sampling circuit is used for forming a voltage difference on the two output ends; and the high-speed gain comparator is connected to the current sampling circuit, the positive pole input end of the high-speed gain comparator is connected between the input end of the current sampling circuit and the grounding output end of the current sampling circuit, and the negative pole input end of the high-speed gain comparator is connected between the input end of the current sampling circuit and the output end of the switching power supply chip of the current sampling circuit. According to the utility model, the current sampling circuit and the high-speed gain comparator can provide a high-frequency working basis for the switching power supply chip, a lower tube can be accurately turned off, an upper tube can be accurately turned on, the accuracy of inductive current is remarkably improved, and meanwhile, a high-voltage tube is utilized to ensure that the circuit can work under a higher voltage condition.

Description

Technical Field

[0001] The utility model relates to the technical field of integrated circuits, in particular to a high-precision current detection circuit. Background Art

[0002] As the "engine" of electronic devices, the power management chip is responsible for power management in the electronic device system and is indispensable.

[0003] In the design and application of power chips, there are a variety of control strategies adopted. Each control method corresponds to a specific application environment and is accompanied by its own advantages and limitations. Among many control methods, the current-mode control method has become one of the most widely used technologies due to its excellent performance. Under this control method, it is particularly crucial to achieve accurate sampling and detection of the inductor current, which directly affects the stability of the power chip output and the amplitude of the current ripple. Accurate current sampling not only ensures the continuous and stable operation of the power supply system but also plays a decisive role in reducing the fluctuation of the output voltage and improving the power quality. Therefore, for maintaining the overall performance and reliability of the power supply system, the accurate detection of the inductor current is an indispensable link.

[0004] Therefore, a high-precision current detection circuit is proposed to solve or alleviate the above problems. Summary of the Utility Model

[0005] The purpose of the utility model is to propose a high-precision current detection circuit to solve the deficiencies existing in the prior art.

[0006] To achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A high-precision current detection circuit includes:

[0008] A current sampling circuit, whose input end is electrically connected, one end of its output end is grounded, and the other end of its output end is connected to a switching power supply chip. The current sampling circuit is used to form a voltage difference between its two output ends;

[0009] A high-speed gain comparator, which is connected to the current sampling circuit. Its positive input terminal is connected between the input terminal of the current sampling circuit and the grounded output terminal of the current sampling circuit, and its negative input terminal is connected between the input terminal of the current sampling circuit and the output terminal of the switching power supply chip of the current sampling circuit. And the input terminal of the high-speed gain comparator is connected to the switching power supply chip. The high-speed gain comparator is used to output a comparison result to the switching power supply chip.

[0010] Preferably, the high-speed gain comparator includes a four-stage comparator, a current bias circuit, and a flip acceleration circuit.

[0011] Preferably, the four-stage comparator includes a first-stage amplifier circuit, a second-stage amplifier circuit, a third-stage amplifier circuit, and a fourth-stage amplifier circuit;

[0012] The first-stage amplifier circuit and the second-stage amplifier circuit are used for pre-amplification, the third-stage amplifier circuit is used for gain, and the fourth-stage amplifier circuit is used for outputting a comparison result.

[0013] Preferably, the first-stage amplifier circuit, the second-stage amplifier circuit, the third-stage amplifier circuit, and the fourth-stage amplifier circuit all include a plurality of NMOS transistors.

[0014] Preferably, the current bias circuit includes a plurality of PMOS transistors.

[0015] Preferably, the flip acceleration circuit includes MOS transistors.

[0016] Preferably, the current sampling circuit includes four NMOS transistors.

[0017] The utility model has the following beneficial effects:

[0018] In the utility model, the current sampling circuit and the high-speed gain comparator can provide a basis for the high-frequency operation of the switching power supply chip, can accurately turn off the lower transistor and turn on the upper transistor, significantly increase the accuracy of the inductor current, and at the same time use high-voltage transistors to ensure that the circuit can work under higher voltage conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the wiring diagram of the utility model;

[0020] Figure 2 is the wiring diagram of the high-speed high-gain comparator in the utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the utility model. Apparently, the described embodiments are only a part of the embodiments of the utility model, rather than all of the embodiments.

[0022] A high-precision current detection circuit includes: a current sampling circuit and a high-speed gain comparator.

[0023] As Figure 1 shown, for the current sampling circuit, its input terminal is electrically connected, one of its output terminals is grounded, the other output terminal is connected to the switching power supply chip, the current sampling circuit is used to form a voltage difference between its two output terminals, and the current sampling circuit includes four NMOS transistors.

[0024] As Figure 2As shown, a high-speed gain comparator is connected to a current sampling circuit. Its positive input terminal is connected between the input terminal of the current sampling circuit and the grounded output terminal of the current sampling circuit. Its negative input terminal is connected between the input terminal of the current sampling circuit and the output terminal of the switching power supply chip of the current sampling circuit. And the input terminal of the high-speed gain comparator is connected to the switching power supply chip. The high-speed gain comparator is used to output a comparison result to the switching power supply chip.

[0025] The high-speed gain comparator includes a four-stage comparator, a current bias circuit, and a flip acceleration circuit. The four-stage comparator includes a first-stage amplifier circuit, a second-stage amplifier circuit, a third-stage amplifier circuit, and a fourth-stage amplifier circuit. The first-stage amplifier circuit and the second-stage amplifier circuit are used for pre-amplification. The third-stage amplifier circuit is used for gain. The fourth-stage amplifier circuit is used for outputting a comparison result. The first-stage amplifier circuit, the second-stage amplifier circuit, the third-stage amplifier circuit, and the fourth-stage amplifier circuit all include several NMOS transistors. The current bias circuit includes several PMOS transistors. The flip acceleration circuit includes MOS transistors.

[0026] Among them, the first-stage amplifier circuit and the second-stage amplifier circuit of the four-stage comparator use resistors as loads, which have smaller parasitic capacitances compared with traditional mos as loads, thus pushing the main pole of the amplifier to a higher frequency to obtain a larger bandwidth. In addition, a capacitor to ground is added between the load resistors, which can also improve the comparator bandwidth. The four-stage comparator also adds a mos transistor with a diode structure in the third-stage amplifier circuit to play a role in accelerating the flip. The gain of the four-stage comparator reaches 92 dB, and the 3 dB bandwidth reaches 4 MHz, which can be used in most switching power supplies.

[0027] When the lower transistor of the current sampling circuit is turned on, four NMOS transistors are turned on. The circuit calculates by collecting the voltage difference between DGND and SW at both ends of the power transistor through a resistor. The current sources I1 and I2 containing the control signal Vc are added to the circuit for operation. Among them, I c1 = I0 + I c , I c2 = 2I0 - I c , I0 is a fixed current generated by a reference. I c is a control current obtained by conversion via EA output. I1 is the current flowing through R5. I2 is the current flowing through R6. MN1 - MN4 are all high-voltage DEMOS, and the drain terminals are connected to the DGND terminal or the SW terminal to meet the working scenario of the chip operating at high-voltage input. When the lower transistor is turned on, the potential of SW gradually rises. When the voltage at the reverse terminal of the four-stage comparator exceeds the voltage at the forward terminal, the four-stage comparator triggers a flip, giving a signal to the subsequent control module to turn off the lower transistor. When the flip is triggered, I1 = I2, (I c1 + I1)R1 = (I c2 + I2)R2 + VSW , substituting all expressions can calculate the inductor current value when the lower transistor is turned off. This current sampling circuit and high-speed gain comparator can provide the basis for the high-frequency operation of the switching power supply chip, accurately turn off the lower transistor and turn on the upper transistor, significantly improve the accuracy of the inductor current, and at the same time use a high-voltage transistor to ensure that the circuit can operate under higher voltage conditions.

[0028] As described above, only the preferred specific embodiments of the present invention are given, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A high-precision current detection circuit, characterized in that: include: A current sampling circuit, wherein the input end thereof is connected to an electrical device, one end thereof is grounded, and the other end thereof is connected to a switching power supply chip, and the current sampling circuit is used to form a voltage difference at the two output ends thereof; A high-speed gain comparator is connected to the current sampling circuit, wherein the positive input end is connected between the input end of the current sampling circuit and the ground output end of the current sampling circuit, the negative input end is connected between the input end of the current sampling circuit and the output end of the switching power supply chip of the current sampling circuit, and the input end of the high-speed gain comparator is connected to the switching power supply chip, and the high-speed gain comparator is used to output the comparison result to the switching power supply chip.

2. A high-precision current detection circuit according to claim 1, characterized in that: The high-speed gain comparator comprises a four-stage comparator, a current bias circuit and a flip acceleration circuit.

3. A high-precision current detection circuit according to claim 2, characterized in that: The four-stage comparator includes a first-stage amplifying circuit, a second-stage amplifying circuit, a third-stage amplifying circuit, and a fourth-stage amplifying circuit; The first-stage amplifier circuit and the second-stage amplifier circuit are used for pre-amplification, the third-stage amplifier circuit is used for gain, and the fourth-stage amplifier circuit is used for outputting a comparison result.

4. A high-precision current detection circuit according to claim 3, characterized in that: The first-stage amplifier circuit, the second-stage amplifier circuit, the third-stage amplifier circuit, and the fourth-stage amplifier circuit all include a plurality of NMOS transistors.

5. A high-precision current detection circuit according to claim 3, characterized in that: The current bias circuit includes a plurality of PMOS transistors.

6. A high-precision current detection circuit according to claim 3, characterized in that: The flip acceleration circuit includes a MOS tube.

7. A high-precision current detection circuit according to claim 1, characterized in that: The current sampling circuit includes four NMOS transistors.

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