阅读说明：本技术 一种电感电流采样电路及其实现方法 (Inductive current sampling circuit and implementation method thereof ) 是由 濮正林 于 2020-02-20 设计创作，主要内容包括：本发明公开了一种电感电流采样电路,主要解决现有电感电流采样精度差、电路成本高的问题。该电流采样的电路包括上采样电路和下采样电路,与上采样电路和下采样电路均相连的输出电路,与上采样电路相连的比较器E1,与下采样电路相连的比较器E2,与比较器E1和比较器E2均相连的数字信号产生模块,与数字信号产生模块相连的滤波电路,与滤波电路相连的负反馈环路,与负反馈环路相连的分压模块和运放电路,以及与运放电路、上采样电路、下采样电路均相连的电流镜像电路。本发明不会产生额外的功率损耗,同时上下管电流的同时检测以及负反馈环路的引入也保证了电流采样的精度。因此,适于推广应用。(The invention discloses an inductive current sampling circuit, which mainly solves the problems of poor sampling precision and high circuit cost of the existing inductive current. This circuit of current sampling includes sampling circuit and down-sampling circuit, the output circuit who all links to each other with sampling circuit and down-sampling circuit, comparator E1 that links to each other with the sampling circuit, comparator E2 that links to each other with the down-sampling circuit, the digital signal who all links to each other with comparator E1 and comparator E2 produces the module, the filter circuit who links to each other with the digital signal production module, the negative feedback loop that links to each other with filter circuit, voltage divider module and the operational amplifier circuit that links to each other with the negative feedback loop, and with the operational amplifier circuit, the sampling circuit, the current mirror image circuit that the down-sampling circuit all links to each other. The invention does not generate extra power loss, and simultaneously the current of the upper tube and the lower tube is detected simultaneously and the introduction of the negative feedback loop also ensures the current sampling precision. Therefore, the method is suitable for popularization and application.)

1. The utility model provides an inductive current sampling circuit, characterized in that, including upsampling circuit (1) and downsampling circuit (2), output circuit (3) with upsampling circuit (1) and downsampling circuit (2) all link to each other, comparator E1 with upsampling circuit (1) links to each other, comparator E2 with downsampling circuit (2) link to each other, digital signal produces module (4) with comparator E1 and comparator E2 all link to each other, filter circuit (6) with digital signal produces module (4) link to each other, negative feedback loop (7) that link to each other with filter circuit (6), voltage divider module (5) and operational amplifier circuit (8) that link to each other with negative feedback loop (7), and with operational amplifier circuit (8), upsampling circuit (1), current mirror image circuit (9) that downsampling circuit (2) all link to each other.

2. The inductor current sampling circuit as claimed in claim 1, wherein the up-sampling circuit comprises a power tube Q1 and a sampling tube Q1_ SNS connected with the gates, the drains of the power tube Q1 and the sampling tube Q1_ SNS are connected with the input terminal Vin, the source of the sampling tube Q1_ SNS is connected with the positive electrode of the comparator E1 and the current mirror circuit, and the source of the power tube Q1 is connected with the negative electrode of the comparator E1 and the output circuit; the down-sampling circuit comprises a power tube Q2 and a sampling tube Q2_ SNS, wherein the grid electrodes of the power tube Q2 and the sampling tube Q2_ SNS are connected and connected to the output circuit and the negative electrode of the comparator E2, the source electrode of the sampling tube Q2_ SNS is connected with the positive electrode of the comparator E2 and the current mirror circuit, and the source electrode of the power tube Q1 is connected with the negative electrode of the comparator E1 and grounded.

3. The inductor current sampling circuit according to claim 2, wherein the digital signal generating module is an RS flip-flop, and comprises two nor circuits U1 and U2, an input a of a nor circuit U1 is connected to an output terminal of a comparator E1, an input B of a nor circuit U1 is connected to an output terminal Q of a nor circuit U2, an input a of a nor circuit U2 is connected to an output terminal of a comparator E2, and an input B of a nor circuit U2 is connected to an output terminal Q of a nor circuit U1; wherein, the output end Q of the NOR gate circuit U2 is connected with the filter circuit.

4. The inductor current sampling circuit according to claim 3, wherein the filter circuit comprises a resistor R3 connected to the output terminal Q of the NOR gate circuit U2 at one end, and a capacitor C1 connected to the other end of the resistor R3 at one end and to ground at the other end.

5. The inductor current sampling circuit according to claim 4, wherein the voltage divider module comprises a resistor R1 having one end connected to the voltage Vcc, and a resistor R2 having one end connected to the resistor R1 and the other end connected to ground; wherein, the connection end of the resistor R1 and the resistor R2 is connected with a negative feedback loop.

6. The inductor current sampling circuit according to claim 5, wherein said negative feedback loop comprises an amplifier E3 having an anode connected to the connection terminal of the resistor R3 and the capacitor C1 and a cathode connected to the connection terminal of the resistor R1 and the resistor R2, and a capacitor C2 having one end connected to the output terminal of the amplifier E3 and the other end connected to ground.

7. The inductor current sampling circuit according to claim 6, wherein said operational amplifier circuit comprises an amplifier E4 having a positive terminal connected to the output terminal of the amplifier E3, and a resistor Rsns having one terminal connected to the negative terminal of the amplifier E4 and the other terminal connected to ground; the pole and the output end of the amplifier E4 are both connected with a current mirror circuit.

8. An inductor current sampling circuit according to claim 7, wherein said current mirror circuit comprises a MOS transistor Q3 having a gate connected to the output of the amplifier E4 and a source connected to the cathode of the amplifier E4, MOS transistors Q4, Q5, Q6 having gates connected to the drain of the MOS transistor Q3, MOS transistors Q7, Q8 having gates connected to the source of the MOS transistor Q5; the source electrodes of the MOS tubes Q4, Q5 and Q6 are connected and then connected with a voltage Vcc, the drain electrode of the MOS tube Q4 is communicated with the grid electrode of the MOS tube Q4, the source electrodes of the MOS tubes Q7 and Q8 are connected and then grounded, the drain electrode of the MOS tube Q8 is connected with the source electrode of the sampling tube Q1_ SNS, and the drain electrode of the MOS tube Q6 is connected with the source electrode of the sampling tube Q2_ SNS.

9. The method for implementing the inductor current sampling circuit according to any one of claims 1 to 8, comprising the following steps:

(S1) acquiring an upper tube current and a lower tube current using an up-sampling circuit and a down-sampling circuit, respectively;

(S2) adjusting the target current value through a negative feedback loop so that the target current is equal to half the power tube current;

(S3) the current mirror circuit controls two paths of target currents, during the conduction time of a tube-in, one path of target current is compared with the tube-in current through a comparator to generate an output signal, and during the conduction time of a tube-out, the other path of target current is compared with the tube-out current through another comparator to generate another output signal;

(S4) generating digital PWM signals by the two paths of output signals through an RS trigger;

(S5) the digital PWM signal is passed through a filter circuit to obtain an average voltage signal;

(S6) integrating the average voltage signal with the reference voltage through the operational amplifier circuit to obtain a voltage signal of the output current information; the reference voltage is obtained by voltage division and is half of the access voltage.

Technical Field

The invention relates to the technical field of power management, in particular to an inductive current sampling circuit.

Background

In applications of DC-DC converters in different fields, it is sometimes necessary to detect output or input current while ensuring output voltage accuracy. Taking a buck DC-DC converter as an example, the inductor current is the output current, and accurate sampling of the inductor current becomes a design challenge.

Fig. 1 and 2 illustrate two common methods applied to sampling the output current of a buck DC-DC converter in the prior art, wherein fig. 1 is a method for sampling the inductor current through the DCR of the inductor, which has the advantages of no additional power loss and poor current sampling precision due to poor DCR precision of the inductor; fig. 2 is a circuit diagram of a current detection circuit implemented by connecting a current sampling resistor in series on an output path, which has the advantage of high current sampling precision, but causes extra power loss on the sampling resistor, and the high power sampling resistor leads to high BOM cost.

Disclosure of Invention

The invention aims to provide an inductive current sampling circuit, which mainly solves the problems of poor inductive current sampling precision and high circuit cost in the prior art.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the utility model provides an inductive current sampling circuit, including upsampling circuit and downsampling circuit, the output circuit who all links to each other with upsampling circuit and downsampling circuit, comparator E1 who links to each other with upsampling circuit, comparator E2 who links to each other with downsampling circuit, the digital signal who all links to each other with comparator E1 and comparator E2 produces the module, the filter circuit who links to each other with the digital signal produces the module, the negative feedback loop who links to each other with filter circuit, voltage divider module and operational amplifier circuit that link to each other with the negative feedback loop, and with operational amplifier circuit, upsampling circuit, the current mirror image circuit that downsampling circuit all links to each other.

Furthermore, the up-sampling circuit comprises a power tube Q1 and a sampling tube Q1_ SNS, wherein the grid electrodes of the power tube Q1 and the sampling tube Q1_ SNS are connected and connected with the input end Vin, the source electrode of the sampling tube Q1_ SNS is connected with the anode of the comparator E1 and the current mirror circuit, and the source electrode of the power tube Q1 is connected with the cathode of the comparator E1 and the output circuit; the down-sampling circuit comprises a power tube Q2 and a sampling tube Q2_ SNS, wherein the grid electrodes of the power tube Q2 and the sampling tube Q2_ SNS are connected and connected to the output circuit and the negative electrode of the comparator E2, the source electrode of the sampling tube Q2_ SNS is connected with the positive electrode of the comparator E2 and the current mirror circuit, and the source electrode of the power tube Q1 is connected with the negative electrode of the comparator E1 and grounded.

Further, the digital signal generating module is an RS flip-flop and comprises two nor gate circuits U1 and U2, an input end a of the nor gate circuit U1 is connected to an output end of the comparator E1, an input end B of the nor gate circuit U1 is connected to an output end Q of the nor gate circuit U2, an input end a of the nor gate circuit U2 is connected to an output end of the comparator E2, and an input end B of the nor gate circuit U2 is connected to an output end Q of the nor gate circuit U1; wherein, the output end Q of the NOR gate circuit U2 is connected with the filter circuit.

Further, the filter circuit comprises a resistor R3 with one end connected with the output end Q of the NOR gate circuit U2, and a capacitor C1 with one end connected with the other end of the resistor R3 and the other end grounded.

Further, the voltage division module comprises a resistor R1 with one end connected to the voltage Vcc and a resistor R2 with one end connected to the resistor R1 and the other end grounded; wherein, the connection end of the resistor R1 and the resistor R2 is connected with a negative feedback loop.

Further, the negative feedback loop comprises an amplifier E3 of which the anode is connected with the connection end of the resistor R3 and the capacitor C1 and the cathode is connected with the connection end of the resistor R1 and the resistor R2, and a capacitor C2 of which one end is connected with the output end of the amplifier E3 and the other end is grounded.

Further, the operational amplifier circuit comprises an amplifier E4 of which the anode is connected with the output end of the amplifier E3, and a resistor Rsns of which one end is connected with the cathode of the amplifier E4 and the other end is grounded; the pole and the output end of the amplifier E4 are both connected with a current mirror circuit.

Further, the current mirror circuit comprises a MOS tube Q3, a grid of which is connected with the output end of the amplifier E4 and a source of which is connected with the cathode of the amplifier E4, MOS tubes Q4, Q5 and Q6, gates of which are connected with the drain of the MOS tube Q3, and MOS tubes Q7 and Q8, gates of which are connected with the source of the MOS tube Q5; the source electrodes of the MOS tubes Q4, Q5 and Q6 are connected and then connected with a voltage Vcc, the drain electrode of the MOS tube Q4 is communicated with the grid electrode of the MOS tube Q4, the source electrodes of the MOS tubes Q7 and Q8 are connected and then grounded, the drain electrode of the MOS tube Q8 is connected with the source electrode of the sampling tube Q1_ SNS, and the drain electrode of the MOS tube Q6 is connected with the source electrode of the sampling tube Q2_ SNS.

Based on the inductive current sampling circuit, the invention also provides an implementation method of the inductive current sampling circuit, which comprises the following specific processes:

(S1) acquiring an upper tube current and a lower tube current using an up-sampling circuit and a down-sampling circuit, respectively;

(S2) adjusting the target current value through a negative feedback loop so that the target current is equal to half the power tube current;

(S3) the current mirror circuit controls two paths of target currents, during the conduction time of a tube-in, one path of target current is compared with the tube-in current through a comparator to generate an output signal, and during the conduction time of a tube-out, the other path of target current is compared with the tube-out current through another comparator to generate another output signal;

(S4) generating digital PWM signals by the two paths of output signals through an RS trigger;

(S5) the digital PWM signal is passed through a filter circuit to obtain an average voltage signal;

(S6) integrating the average voltage signal with the reference voltage through the operational amplifier circuit to obtain a voltage signal of the output current information; the reference voltage is obtained by voltage division and is half of the access voltage.

Compared with the prior art, the invention has the following beneficial effects:

the invention utilizes the median comparison of the current of the upper and lower tubes, converts the PWM signal into an analog level through an RC filter, the reference voltage is Vcc/2, the Vsns is Rsns I L/K through a negative feedback loop formed by an integrator, the target current is iset1/iset2 is controlled through the negative feedback loop, and the target current is equal to the median of the current of the upper and lower tubes through the current comparison, thus not only indirectly obtaining the median of the current of the upper and lower tubes, but also obtaining the inductive current value.

Drawings

Fig. 1 is a schematic diagram of a current sampling method in the prior art.

Fig. 2 is another current sampling schematic of the prior art.

Fig. 3 is a schematic circuit diagram of the present invention.

Fig. 4 is a waveform diagram of a voltage waveform and an inductor current of a SW node of the DC-DC converter of the present invention.

Wherein, the names corresponding to the reference numbers are:

the circuit comprises a 1-up sampling circuit, a 2-down sampling circuit, a 3-output circuit, a 4-digital signal generating module, a 5-voltage division module, a 6-filter circuit, a 7-negative feedback loop, an 8-operational amplifier circuit and a 9-current mirror circuit.

Detailed Description

The present invention will be further described with reference to the following description and examples, which include but are not limited to the following examples.