TWI591950B - Dcr inductor current-sensing in four-switch buck-boost converters - Google Patents

Description

Current detection of DC impedance inductor in four-switch buck-boost converter [Cross-Reference to Related Applications]

The present invention relates to and claims the application No. 62/054,587, entitled "Current Detection of DC Impedance Inductors in a Four-Switch Buck-Boost Converter", filed on September 24, 2014, in the US invention provisional application (hereinafter referred to as " Pending trial 1"). The disclosure of Pending Case 1 is incorporated herein by reference.

The present invention relates to and claims the application No. 62/088, 433, entitled "Switching Boost Buck Regulator with Peak Bucking Peak Boost Current Mode Control", and the filing date of the US invention for December 5, 2014 Case (hereinafter referred to as "temporary case 2 pending"). The disclosure of Pending Case 2 is incorporated herein by reference.

The present invention relates to and claims the application No. 14/677,794, entitled "Current Detection of DC Impedance Inductors in a Four-Switch Buck-Boost Converter", filed on April 2, 2015, the US invention provisional application (hereinafter referred to as " Pending trial 3"). The disclosure of Pending Case 3 is incorporated herein by reference.

The present invention relates to and claims the application No. 14/660,739, entitled "Switching Boost Buck Regulator with Peak Bucking Peak Boost Current Mode Control", filed on March 17, 2015, US Provisional Application for Inventions Case (hereinafter referred to as "temporary case 4 pending"). The disclosure of the temporary case 4 pending It is incorporated herein by reference.

The present invention relates to current measurement of an inductor in a four-switch buck-boost power converter; the present invention utilizes a RC circuit to be a virtual ground to measure the current of the inductor.

The four-switch buck-boost power converter can be used in many different applications, such as a power converter that regulates the output voltage to be higher, the same, or lower than the input voltage. The traditional four-switch buck-boost power converter has a single inductor that provides high efficiency over a wide range of load currents. Although providing overcurrent protection, discontinuous operation mode or current loop regulation, and detecting inductor current are the basic requirements of power converters, for four-switch buck-boost power converters, high common mode is often found in the bilateral terminals of inductors. Noise makes current detection difficult.

Figure 1 shows a first current sensing technique using a sense resistor in power converter 100 for use with the LM5118 and LM25118 circuits of Texas Instruments, Dallas, Texas. As shown in FIG. 1, the circuit of the power converter 100 includes an inductor 101, a diode 104, a detecting resistor 105, and switches 102, 103. The detecting resistor 105 and the diode 104 are connected in series to an end point of the inductor 101. When (only when) the diode 104 is in the on state, the current on the inductor 101 is detected, but such a configuration cannot be detected. The peak current of the inductor 101.

FIG. 2 shows another current sensing technique for a four-switch buck-boost power converter 200. The four-switch power converter 200 includes an inductor 201, switches 202-205, an output capacitor 206, and a sense resistor 207. Detecting resistor 207 detects the valley current of the inductor in "buck" mode (ie, when switch 205 remains in the "on" state) and detects the peak of the inductor in "boost" mode Current (ie, when switch 202 remains in the normally "on" state). The current sensing technology is used in the LTC3780, LTC3789, LT3791, and LT8705 circuits of Linear Technology, Milpitas, California.

The techniques of FIGS. 1 and 2 have two disadvantages. First, the detecting resistor 105 of FIG. 1 and the detecting resistor 207 of FIG. 2 can only detect a part of the inductor current, because each detecting resistor has to have The switch is configured so that the current flowing through each inductor flows through the sense resistor. Second, the detecting resistor 105 of FIG. 1 and the detecting resistor 207 of FIG. 2 are both energy intensive, causing problems in heat dissipation of each circuit. At the same time, the use of high-power, high-precision detection resistors increases system cost and takes up a lot of space.

Another type of current sensing technology called "DC Current Inductor Detection Current Structure" has been widely used in buck or boost converters. Figure 3 shows a DC impedance inductor on a four-switch buck-boost converter 300. The structure of the current is detected. As shown in FIG. 3, the four-switch buck-boost converter 300 includes switches 305-308, an inductor 303, and an output capacitor 309. The equivalent DC impedance R _{DCR of the} inductor 303 is indicated by an equivalent DC impedance 304 in FIG. The current of inductor 303 is measured from series sense resistor 301 and sense capacitor 302 and in parallel to inductor 303 (and equivalent DC impedance 304). Try to match the DC impedance inductor detection current structure with the time constant of the inductor current i _L , which can be the ratio of the inductor 303 inductance L to the equivalent DC impedance R _DCR (ie L / R _DCR ), or the detection resistance. The product of the 301 resistance value R _s and the capacitance C _s of the detection capacitor 302 is obtained, and the voltage V _sense measured across the entire detection capacitor 302 under the structure, and the inductor current i _L and the equivalent DC impedance of the inductor are obtained. The result of R _DCR is proportional to V _sense = i _L * R _DCR . However, as Park et al . proposed in the 23rd Applied Power Electronics Symposium "10MHz Current Mode Four-Switch Buck-Up Converter for Polarization Modulation", pp. 1977-83: Switching on the measured voltage The rail-to-rail common-mode voltage range and high common-mode noise generated by the converter output switch make the current-detecting circuit very complicated and difficult to implement.

According to an embodiment of the present invention, an inductor current measuring circuit for measuring an inductor current includes: (a) a first resistor-capacitor network (RC network) coupled to the first terminal of the inductor and the reference voltage source And (b) a second resistor-capacitor network coupled between the second terminal of the inductor and the reference voltage source. The first resistor-capacitor network and the second resistor-capacitor network each have a time constant, and the time constant is substantially equal to a ratio between the inductor inductance and the equivalent DC impedance. The current-measured inductor can be a primary inductor in a four-switch buck-boost converter that receives the input voltage and provides an output voltage.

In one embodiment the reference voltage source provides a virtual ground terminal that is coupled to the system ground reference terminal by a decoupling capacitor. When the four-switch buck-boost converter is in buck mode, boost mode, and buck-boost mode, the virtual ground reference is used as the output voltage, the input voltage, and the average voltage across the entire inductor voltage.

In one embodiment, the inductor current measuring circuit may further include a third detecting capacitor connected between the first resistor-capacitor network and the second resistor-capacitor network, the third detecting capacitor having a first detecting ratio The capacitance of each of the two resistor-capacitor networks has a higher capacitance value.

According to another embodiment of the present invention, the first resistor-capacitor network and the second resistor-capacitor network each have a time constant, and the time constant is substantially equal to a ratio between the inductor and the equivalent DC impedance. The first and second resistor-capacitor networks each have (a) a detecting capacitor; (b) a first resistor coupled between the first terminal of the detecting resistor and the first terminal of the detecting capacitor; (c) coupled to a DC blocking capacitor of one of the terminals of the inductor; and (d) a second resistor coupled between the first terminal of the detecting capacitor and the other terminal of the DC blocking capacitor. After the ratio of the resistance between the second resistor of the second resistor-capacitor network and the first resistor is reduced by one, it is roughly the inductance of the inductor and the equivalent DC impedance. Resistance ratio. The respective DC blocking capacitors of the first and second resistor-capacitor networks have higher capacitance values than the respective sensing capacitors on the first and second resistor-capacitor networks.

The method for detecting the inductor current of the present invention can be used to control the switching of a four-switch buck-boost converter, and the embodiment of the control is disclosed in Pending Case 2.

For a better understanding of the present invention, the following detailed description will be further described in conjunction with the accompanying drawings.

100‧‧‧Power Converter

101‧‧‧Inductors

102, 103‧‧‧ switch

104‧‧‧ diode

105‧‧‧Detection resistance

200‧‧‧4-switched buck-boost power converter

201‧‧‧Inductors

202-205‧‧‧Switch

206‧‧‧Output capacitor

207‧‧‧Detection resistance

300‧‧‧4-switch buck-boost converter

301‧‧‧Detection resistance

302‧‧‧Detecting capacitance

303‧‧‧Inductors

304‧‧‧ equivalent DC impedance

305-308‧‧‧Switch

309‧‧‧output capacitor

400‧‧‧4-switch buck-boost converter

401-a, 401-b‧‧‧ Detecting resistance

402-a, 402-b‧‧‧ detection capacitance

410, 420‧‧‧ phase shift filter

500‧‧‧4-switch buck-boost converter

501‧‧‧Decoupling capacitor

600‧‧‧4-switch buck-boost converter

601‧‧‧Detection Capacitance

700‧‧‧4-switch buck-boost converter

701‧‧‧Detection resistance

702-a, 702-b‧‧‧ DC blocking capacitor

703-a, 703-b‧‧‧ resistance

800‧‧‧ four-switch buck-boost converter

801‧‧‧Detection Capacitance

802‧‧‧virtual ground

R _DCR ‧‧‧ equivalent DC impedance

i _L ‧‧‧Inductor current

L‧‧‧Inductance

R _s ‧‧‧resistance

R ₁ ‧‧‧ resistance value

R ₂ ‧‧‧ resistance value

R _sense ‧‧‧Detection resistance

C _s ‧ ‧ capacitance value

C _f ‧‧‧capacitance value

C _{dcouple ‧‧‧capacitance} value

C _block ‧‧‧capacitance value

V _sense ‧‧‧Measured voltage

I _sense+ , I _sense- ‧‧‧ nodes

SW1, SW2‧‧‧ switch node

R _s C _s ‧‧‧ time constant

V _OUT ‧‧‧ output voltage

V _IN ‧‧‧ input voltage

Virtual GND‧‧‧Virtual Ground

FIG. 1 shows a first current sensing technique in which the conventional power converter 100 uses a sense resistor.

FIG. 2 shows another current sensing technique for the conventional four-switch buck-boost power converter 200.

FIG. 3 shows a structure of a DC-impedance inductor detecting current on a conventional four-switch buck-boost converter 300.

4 shows an embodiment of a four-switch buck-boost converter 400 of the present invention for performing a DC impedance current measurement method.

Figure 5 shows an embodiment of the four-switch buck-boost converter 500 of the present invention that eliminates the DC bias of the sense capacitors 402-a and 402-b by setting the phase shift filters 410 and 420 to virtual ground.

6 shows an embodiment of the four-switch buck-boost converter 600 of the present invention that provides higher performance than the four-switch buck-boost converter 500 operating in the buck-boost mode of FIG.

FIG. 7 shows an embodiment in which the four-switch buck-boost converter 700 of the present invention detects current on the inductor 303 using the sense resistor 701 instead of the DC impedance of the inductor 303.

8 shows an embodiment of the four-switch buck-boost converter 800 of the present invention that provides a _sense capacitance 801 across the nodes I _sense+ and I _sense- and the virtual ground 802.

Similar elements are labeled with similar component symbols in the above figures.

4 shows an embodiment of a four-switch buck-boost converter 400 of the present invention for performing a DC impedance current measurement method. Compared with the four-switch buck-boost converter 300 having the detecting resistor 301 and the detecting capacitor 302 connected in parallel with the inductor 303, the four-switch buck-boost converter 400 has phase shift filters 410 and 420, a phase shift filter. 410 and 420 are respectively composed of a detecting resistor 401-a and a detecting capacitor 402-a, a detecting resistor 401-b, and a detecting capacitor 402-b. The voltage measured by the nodes I _sense+ and I _sense- on the respective phase shift filters 410 and 420 respectively represents the differential voltage across the switch nodes SW1 and SW2 by using the time constant L / R _DCR and The time constants R _s C _{s of} the phase shift filters 410 and 420 are matched, and the measured voltage V _{sense is} proportional to the inductor current i _L and the inductor equivalent DC impedance R _DCR , ie V _sense =I _sense+ -I _Sense- = i _L * R _DCR (see Figure 4).

In the embodiment of FIG. 4, although lossless full inductor current detection can be achieved without high common mode noise, the detection capacitors 402-a and 402-b must maintain a very good match to eliminate all instantaneous differential errors. For example, two detection capacitors can be assembled on the same crystal plate to achieve such a match. At the same time, since the DC bias voltages of the detecting capacitors 402-a and 402-b are changed according to the input and output voltages, the detecting capacitors 402-a and 402-b are preferably capacitors having a low voltage coefficient, so that the width is wide. The voltage range is maintained to match the time constant.

5 shows an embodiment of the four-switch buck-boost converter 500 of the present invention that eliminates the DC bias of the sense capacitors 402-a and 402-b by setting the phase shift filters 410 and 420 to the virtual ground Virtual GND. As shown in FIG. 5, the detecting capacitors 402-a and 402-b are not connected to the system ground but are connected to the virtual ground. The voltage of the virtual ground may be different reference voltages depending on the mode of operation, for example, In the buck mode (ie, the switch 308 remains in the active state in this mode of operation), the virtual ground can be connected to the output voltage V _OUT ; in the boost mode (ie, the switch 305 remains in the active mode), the virtual ground The terminal can be connected to the input voltage V _IN ; in the buck-boost mode, the virtual ground can be set to track the average voltage of the nodes SW1 and SW2. The decoupling capacitor 501 stabilizes the voltage and transient bias of the virtual ground when switching the mode of operation. In the four-switch buck-boost converter 500 of FIG. 5, the sense resistors 401-a and 401-b and the sense capacitors 402-a and 402-b are also used to match the time constant of the inductor current i _L , ie, L / R _DCR =R _s C _s . Preferably, the virtual ground terminal maintains a stable voltage during the buck-boost mode to avoid errors in the instantaneous mismatch of the detection capacitors 402-a and 402-b, and the detection capacitors 402-a and 402-b should Maintain a good match to avoid transient errors when operating in buck-boost mode.

6 shows an embodiment of the four-switch buck-boost converter 600 of the present invention that provides higher performance than the four-switch buck-boost converter 500 operating in the buck-boost mode of FIG. By detecting the capacitance in the 402-a and 402-b (respective capacitance value C _f) with an additional detection capacitance 601 (capacitance value C _s), four-switch buck converter 600 may improve performance instantly. The time constant of the inductor current i _L of the four-switch buck-boost converter 600 is matched according to this formula (See Fig. 6). In this formula, the term in parentheses is the first term of the capacitance value C _s of the capacitor 601 (ie, the capacitance value C _f is selected to be a capacitance value much lower than the capacitance value C _s ), and the capacitance is made. The value C _s can match the time constant of the inductor current. This method reduces the sensitivity of the detection capacitors 402-a and 402-b, so any effect caused by the mismatch of the capacitances of the detection capacitors 402-a and 402-b can be significantly minimized.

Then, the DC impedance inductor flow measurement method modified by the four-switch buck-boost converter 600 in FIG. 6 is studied by a simulation experiment. L = 4.7uH, the equivalent DC resistance R _DCR = 10m Ω, sensing resistor 401-a and 401-b of each of the resistance value R _s = 33.33k Ω in the inductance of the simulation, the inductor 303, and detecting capacitance 601 is the standard capacitance value C _s = 0.0047uF, the capacitance values of the detection capacitors 402-a and 402-b are 0.0037uF and 0.0057uF, respectively, and the standard capacitance C _f between the analog detection capacitors 402-a and 402-b There is a 10% mismatch. In this simulation experiment, the four-switch buck-boost converter 600 operates in a buck-boost mode. The input voltage is ramped from 0 volts (ms) to 10 volts to 10 volts, and at 10 volts for 0.4 ms, then allowed to cost. It rises to 13 volts at 0.15ms and is maintained until the input voltage rises from 0 volts and then 2.0ms. During this period, the output voltage starts at 0 volts, but rises to about 15 volts at 0.7 ms after the start, and the regulation is maintained at 15 volts level to 1.3 ms after the start, and the output voltage drops sharply at 1.3 ms. To ground. From the current measured across the entire capacitor 601 as the current and voltage of the inductor 303 drop, it can be seen that the difference between the two is not significant throughout the simulation. A 10% mismatch between the sense capacitors 402-a and 402-b is detected, and the instantaneous voltage across the entire sense capacitor 601 is expected to be less than 4 mV.

Because the DC resistance of the inductor is relatively unstable, the detection resistor can be used instead of the equivalent DC impedance 304 (ie, the DC impedance of the inductor 303) for high precision operation. FIG. 7 shows an embodiment of the four-switch buck-boost converter 700 of the present invention for detecting current on the inductor 303 using the sense resistor 701. As shown in FIG. 7, the _sense resistor 701 having a resistance value of R _sense is connected in series to the inductor 303 (the resistor 701 can be connected to the node SW1 or the node SW2, that is, one end of the inductor 303). Through the series connection of the resistor-capacitor network formed by the detecting resistors 401-a, 401-b and the detecting capacitors 402-a, 402-b, the end points of the detecting resistor 701 are each coupled to the ground. In addition, the two resistor-capacitor networks formed by the resistors 703-a, 703-b and the DC blocking capacitors 702-a, 702-b respectively connect the nodes I _sense+ and I _sense- to the one end of the inductor 303 away from the detector The node SW2 of the resistance 701 is measured. Detecting capacitor 402-a and 402-b of the respective capacitance value C _s, respectively, much lower than the selected value of the capacitance C _block of the value C _s of a DC blocking capacitor 702-a and 702-b, 7 The resistance values of the resistors 401-a and 703-b are all R ₁ ; the resistance values of the resistors 401-b and 703-a are both R ₂ . Under this setting, when the resistance relationship is maintained as ( R ₂ / R ₁ )-1=R _sense /R _DCR (see Figure 7), select the phase shift time for the resistor 401-b and the detection capacitor 402-b. The constant and the inductor 303 (ie, L / R _DCR = R ₂ C _s ) match the capacitance value C _s and the resistance values R ₁ , R ₂ . The product of the inductor current i _L and the _sense resistor R _sense is the voltage drop value V _sense across the nodes I _sense+ and I _sense− .

As shown in FIG. 5 and FIG. 6, the application of the virtual ground and the detection capacitor across I _sense+ and I _sense- can avoid the influence of the capacitance values mismatch between the detection capacitors 402-a and 402-b. The same applies to the four-switch buck-boost converter 700 of FIG. Figure 8 shows four switching step-down converter 800 provides a crossover node I _{sense +,} 802 Example _I sense- detection capacitor 801 and a virtual ground. As shown in Figure 8, the decoupling capacitor (capacitance value C _dcouple ) _isolates the true ground reference from the virtual ground 802. The voltage of the virtual ground 802 can be set to node SW1, node SW2, or other average The average voltage. In the structure of four-switch step-down converter 800, by selecting a capacitance detection is greater than 402-a and 402-b of the respective capacitance values of C _f and C _block is much smaller than the capacitance value of the capacitance detector C _s, when the resistance relationship holds When ( R ₂ / R ₁ )-1=R _sense /R _DCR , the time constant of the inductor 303 can be matched according to the formula of L / R _DCR = R ₂ (C _s + C _f /2). The product of the inductor current i _L and the _sense resistor R _sense is the voltage drop value V _sense across the nodes I _sense+ and I _sense- (see Figure 8). Like the four-switch buck-boost converter 700 of FIG. 7, the sense resistor 701 can also be connected to the node SW1 or the node SW2, that is, one end of the inductor 303.

The invention can be applied to any range of sources for detecting inductor current, such as detecting the average current of an inductor. The method illustrated in Figures 4 through 6 improves the inductor current by high-pass filtering or low-pass filtering, providing a lossless method that detects the continuous current of the inductor without dc errors. The method of the present invention is equally applicable to a four-switch buck-boost converter controlled in a voltage mode or a current mode, and can also be applied to an integrated circuit.

The above description is only illustrative of the embodiments of the present invention and is not intended to limit the scope of the present invention, and those skilled in the art can make various modifications and changes to the invention without departing from the scope of the invention. The definition of the invention is as described in the following patent.

400‧‧‧4-switch buck-boost converter

303‧‧‧Inductors

304‧‧‧ equivalent DC impedance

305-308‧‧‧Switch

309‧‧‧output capacitor

401-a, 401-b‧‧‧ Detecting resistance

402-a, 402-b‧‧‧ detection capacitance

410, 420‧‧‧ phase shift filter

R _DCR ‧‧‧ equivalent DC impedance

L‧‧‧Inductance

R _s ‧‧‧resistance

C _s ‧ ‧ capacitance value

I _sense+ , I _sense- ‧‧‧ nodes

SW1, SW2‧‧‧ switch node

V _OUT ‧‧‧ output voltage

V _IN ‧‧‧ input voltage

Claims (45)

An inductor current measuring circuit for measuring a current of a primary inductor in a four-switch buck-boost converter, wherein the primary inductor receives an input voltage and an output voltage, and has an inductor and a The equivalent DC impedance includes: a first resistor-capacitor network coupled between the first terminal of the primary inductor and a reference voltage source; and a second resistor-capacitor network coupled to the original The second terminal of one of the level inductors is coupled to the reference voltage source, wherein the reference voltage source provides a virtual ground reference terminal to the first resistor-capacitor network and the second resistor-capacitor network. The inductor current measuring circuit of claim 1, wherein the first resistor-capacitor network and the second resistor-capacitor network each have a time constant which is substantially equal to the inductance and the equivalent DC impedance. The ratio. The inductor current measuring circuit of claim 1 further includes a decoupling capacitor, and the virtual ground reference terminal is connected to a system ground reference terminal. The inductor current measuring circuit of claim 1, wherein when the four-switch buck-boost converter operates in a buck mode, the voltage of the virtual ground reference terminal is an output voltage. The inductor current measuring circuit of claim 1, wherein when the four-switch buck-boost converter operates in a boost mode, the voltage of the virtual ground reference terminal is an input voltage. The inductor current measuring circuit of claim 1, wherein when the four-switch buck-boost converter operates in a buck-boost mode, the voltage of the virtual ground reference terminal is connected across the first terminal and the second The average voltage of one of the terminals. The inductor current measuring circuit of claim 1 further includes a detecting capacitor connected between the first resistor-capacitor network and the second resistor-capacitor network. The inductor current measuring circuit of claim 7, wherein the detecting capacitor has a capacitance value higher than an effective capacitance of the first resistor-capacitor network and the second resistor-capacitor network. A method for measuring a current in a primary inductor of a four-switch buck-boost converter, wherein the primary inductor receives an input voltage and an output voltage, and has an inductor and an equivalent DC impedance, including Connecting a first resistor-capacitor network between the first terminal of the inductor and a reference voltage source; connecting a second resistor-capacitor network between the second terminal of the inductor and the reference voltage source The reference voltage source provides a virtual ground reference to the first resistor-capacitor network and the second resistor-capacitor network; and measuring a node of the first resistor-capacitor network and the second resistor-capacitor network A voltage between a node. The method of claim 9, wherein the first resistor-capacitor network and the second resistor-capacitor network each have a time constant that is substantially equal to the inductor and the equivalent DC impedance of the primary inductor. The ratio between the two. The method of claim 9, further comprising a decoupling capacitor connecting the virtual ground reference to a system ground reference. The method of claim 9, wherein when the four-switch buck-boost converter operates in a buck mode, the voltage of the virtual ground reference terminal is an output voltage. The method of claim 9, wherein the voltage of the virtual ground reference terminal is used as an input voltage when the four-switch buck-boost converter operates in a boost mode. The method of claim 9, wherein when the four-switch buck-boost converter operates in a buck-boost mode, the voltage of the virtual ground reference terminal is averaged across one of the first terminal and the second terminal. Voltage. The method of claim 9, further comprising a detecting capacitor connected between the first resistor-capacitor network and the second resistor-capacitor network. The method of claim 15, wherein the detecting capacitor has a capacitance value higher than an effective capacitance of the first resistor-capacitor network and the second resistor-capacitor network. An inductor current measuring circuit for measuring a current on an inductor, wherein the inductor has a first terminal and a second terminal, and the inductor current measuring circuit comprises: a detecting resistor connected to the inductor The first terminal; a first DC blocking capacitor and a second DC blocking capacitor, each of the DC blocking capacitors has a first terminal and a second terminal, and the second terminal of each DC blocking capacitor is coupled to the first terminal a second terminal of the inductor; a first resistor-capacitor network coupled between the first terminal of the detecting resistor and a reference voltage source, and coupled to the first DC blocking capacitor And a second resistor-capacitor network coupled between the second terminal of the detecting resistor and the reference voltage source, and coupled to the first terminal of the second DC blocking capacitor. The inductor current measuring circuit of claim 17, wherein the first resistor-capacitor network and the second resistor-capacitor network each have a time constant which is substantially equal to the inductance and the equivalent DC impedance. The ratio. The inductor current measuring circuit of claim 17, wherein the first resistor-capacitor network comprises: a detecting capacitor having a first terminal and a second terminal, the second terminal coupling of the detecting capacitor Connected to the reference voltage source; a first resistor coupled between the first terminal of the detecting resistor and the first terminal of the detecting capacitor; and a second resistor coupled to the detecting The first terminal of the capacitor is between the first terminal of the first DC blocking capacitor. The inductor current measuring circuit of claim 19, wherein the second resistor-capacitor network comprises: a detecting capacitor having a first terminal and a second terminal, the second terminal coupling of the detecting capacitor Connected to the reference voltage source; a first resistor coupled between the second terminal of the detecting resistor and the first terminal of the detecting capacitor in the second resistor-capacitor network; and a second resistor The first terminal of the detecting capacitor and the first terminal of the second DC blocking capacitor are coupled to the second resistor-capacitor network. The inductor current measuring circuit of claim 20, wherein a ratio of a resistance between the second resistor of the second resistor-capacitor network and the first resistor of the second resistor-capacitor network is reduced by one The resistance ratio of the sense resistor of the inductor to the equivalent DC impedance. The inductor current measuring circuit of claim 20, wherein the first and the second DC blocking capacitors each have a higher one of the detection capacitors corresponding to the respective first and second resistor-capacitor networks. Capacitance value. The inductor current measuring circuit of claim 17, wherein the inductor is a primary inductor of a four-switch buck-boost converter for receiving an input voltage and providing an output voltage. The inductor current measuring circuit of claim 23, wherein the reference voltage source provides a virtual ground reference. The inductor current measuring circuit of claim 24 further includes a decoupling capacitor, and the virtual ground reference terminal is connected to a system ground reference terminal. The inductor current measuring circuit of claim 24, wherein when the four-switch buck-boost converter operates in a buck mode, the voltage of the virtual ground reference terminal is an output voltage. The inductor current measuring circuit of claim 24, wherein when the four-switch buck-boost converter operates in a boost mode, the voltage of the virtual ground reference terminal is an input voltage. The inductor current measuring circuit of claim 24, wherein when the four-switch buck-boost converter operates in a buck-boost mode, the voltage of the virtual ground reference terminal is a first terminal across the inductor. And an average voltage of one of the second terminals of the inductor. The inductor current measuring circuit of claim 24 further includes an additional detecting capacitor connected between the first resistor-capacitor network and the second resistor-capacitor network. The inductor current measuring circuit of claim 29, wherein the additional detecting capacitor has a capacitance value higher than a detecting capacitance of the first resistor-capacitor network and the second resistor-capacitor network. . A method for measuring a current on an inductor, wherein the inductor has a first terminal and a second terminal, and has an inductor and an equivalent DC impedance, including: connecting a detecting resistor to the inductor One terminal Connecting a second terminal of a first DC blocking capacitor and a second terminal of a second DC blocking capacitor to the second terminal of the inductor, wherein each of the DC blocking capacitors has a first terminal and the second a first resistor-capacitor network is coupled between the first terminal of the detecting resistor and a reference voltage source, and coupled to the first terminal of the first DC blocking capacitor; and the second resistor and capacitor The network is coupled between the second terminal of the detecting resistor and the reference voltage source, and coupled to the first terminal of the second DC blocking capacitor; and measuring a node of the first resistor-capacitor network A voltage between a node of the second resistor-capacitor network. The method of claim 31, wherein the first resistor-capacitor network and the second resistor-capacitor network each have a time constant that is substantially equal to a ratio between the inductor and the equivalent DC impedance. The method of claim 31, wherein the first resistor-capacitor network comprises: a detecting capacitor having a first terminal and a second terminal, wherein the second terminal of the detecting capacitor is coupled to the reference a voltage source; a first resistor coupled between the first terminal of the detecting resistor and the first terminal of the detecting capacitor; and a second resistor coupled to the detecting capacitor A terminal is between the first terminal of the first DC blocking capacitor. The method of claim 33, wherein the second resistor-capacitor network comprises: a detecting capacitor having a first terminal and a second terminal, wherein the second terminal of the detecting capacitor is coupled to the reference power source; a first resistor coupled between the second terminal of the detecting resistor and the first terminal of the detecting capacitor; and a second resistor coupled to the first terminal of the detecting capacitor Between the first terminals of the second DC blocking capacitor. The method of claim 34, wherein the voltage is connected to the first terminal of the detecting capacitor across the first resistor-capacitor network and the first detecting capacitor on the second resistor-capacitor network The terminal is measured. The method of claim 34, wherein a ratio of a resistance between the second resistor of the second resistor-capacitor network and the first resistor of the second resistor-capacitor network is reduced by one, that is, the inductor The resistance ratio of the sense resistor to the equivalent DC impedance. The method of claim 34, wherein the first and the second DC blocking capacitors each have a higher capacitance value than the respective detection capacitors of the first and second resistor-capacitor networks. The method of claim 31, wherein the inductor is a primary inductor of a four-switch buck-boost converter for receiving an input voltage and providing an output voltage. The method of claim 38, wherein the reference voltage source provides a virtual ground reference. The method of claim 39, further comprising a decoupling capacitor, connecting the virtual ground reference to a system ground reference. The method of claim 39, wherein when the four-switch buck-boost converter operates in a buck mode, the voltage of the virtual ground reference terminal is an output voltage. The method of claim 39, wherein when the four-switch buck-boost converter operates in a boost mode, the voltage of the virtual ground reference terminal is an input voltage. The method of claim 39, wherein when the four-switch buck-boost converter operates in a buck-boost mode, the voltage of the virtual ground reference terminal is across a first terminal of the inductor and the inductor One of the second terminals is an average voltage. The method of claim 39, further comprising an additional detecting capacitor connected between the first resistor-capacitor network and the second resistor-capacitor network. The method of claim 44, wherein the additional detection capacitor has a capacitance value higher than a detection capacitance of the first resistor-capacitor network and the second resistor-capacitor network.