WO2020061727A1

WO2020061727A1 - Load current detection method and circuit for inductive switching power converter

Info

Publication number: WO2020061727A1
Application number: PCT/CN2018/107197
Authority: WO
Inventors: 张海波; 李盛峰; 柏志彬; 黄令华
Original assignee: 深圳市华芯邦科技有限公司
Priority date: 2018-09-25
Filing date: 2018-09-25
Publication date: 2020-04-02

Abstract

A load current detection method for an inductive switching power converter, comprising the following steps: acquiring inductor current rise or fall period time T_A in an Ath switching cycle and inductor current rise or fall period time T_B in a Bth switching cycle; sampling a load current in the Bth switching cycle at a time point after 0.5T_A elapses from a starting point of an inductor current rise or fall period, i.e. a first middle time point T_MB; from the first middle time point T_MB to a second middle time point T_MC, according to the type and working mode of a switching power converter, sampling and holding the sample value of the load current using a corresponding method, and using said sample value as a load current of the switching power converter in a switching cycle, the second middle time point T_MC being a time point after 0.5 T_B elapses from a starting point of an inductor current rise or fall period in a Cth switching cycle. An inductor current changes linearly in a turn-on period of a power transistor, and the sampled and held current signal can be converted into a load current signal according to a circuit type and a working mode, greatly simplifying a detection circuit and improving the detection accuracy.

Description

Method and circuit for detecting load current of inductive switching power converter

Technical field

The invention relates to the technical field of switching power converter circuits, and in particular to a method and a circuit for detecting a load current of an inductive switching power converter, which reduces the complexity of the load current detection circuit and improves the accuracy of load current detection.

Background technique

Switching power converter circuits are one of the most important types of power supply voltage converters, and are mainly applicable to voltage conversion situations. The circuit form of DC / DC switching power converters includes a charge pump circuit implemented with a capacitor and also includes an inductor Implemented buck-type Buck switching circuit, boost-type Boost circuit, and negative-voltage circuit Buck-Boost circuit. In order to precisely control the current in the switching power converter circuit, it is necessary to accurately detect the load current.

In the prior art, one of the commonly used load current detection methods is the technical solution shown in FIG. 2. A current sense resistor is connected in series on the current path of the inductor, and the voltage on the current sense resistor is amplified by an operational amplifier to implement load current detection. In the scheme of an external current-sense resistor, the operational amplifier needs to detect the voltage across the resistor at all times, which requires extremely high speed and accuracy of the operational amplifier.

In the technical solution shown in FIG. 2, it is assumed that the circuit terminal V1 is an input terminal of an external power supply and V2 is a power output terminal of a switching power converter. At this time, the switching power converter is a switching power supply based on a buck circuit. converter. Conversely, if the circuit terminal V1 is a power output terminal of a switching power converter and V2 is an input terminal of an external power supply, the switching power converter is a switching power converter based on a boost circuit.

When the switching power converter works in Buck circuit mode, the current flowing through the load detection resistor Rsen also flows through the inductor, so the amplifier can indirectly detect the current through the current detection resistor Rsen by detecting the voltage on the load detection resistor Rsen. And inductor current. The circuit of this structure needs to connect a load detection resistor Rsen to the inductor in series. The efficiency of this switching power converter is lost, additional pins are required to detect the voltage across the resistor, and a high-precision current detection resistor is more expensive.

In the prior art, the second commonly used load current detection method is a technical solution for detecting load current through a power tube current mirror as shown in FIG. 3. In the method for detecting load current through a power tube current mirror, a mirror tube Q3 is required. The ratio of the mirror tube Q3 to the power tube Q1 is 1: K. For a switching power converter based on a buck-type circuit, the sum of the currents flowing through power tube Q1 and power tube Q2 is the load current. If power tube Q1 and power tube Q2 are to be detected, then the circuit will be very complicated. Although the current of the Buck switching power converter circuit is continuous, if the currents of the two power tubes, namely the switching tube and the freewheeling tube, are to be detected, two sets of load current detection circuits are required. The detection cost is relatively high and the implementation is complicated.

In some prior art load detection circuits, the peak current of any one of the power tube Q1 or the power tube Q2 is detected, and the peak current is sampled and held as the load current of one switching cycle. As shown in Figures 4 and 5, it is clear that there is a shaded error between the current sampled and held according to the peak current of power tube Q1 and the actual load current. When the Buck-type circuit-based switching power converter works in CCM mode, the error is already relatively large, and the error is shown in the shaded part in Figure 4. When the load current is getting smaller and smaller, even after entering the DCM mode, as shown in the figure As shown in Fig. 5, the error, that is, the proportion of the shadow area in the area of the entire figure, is larger, and the error of the detection circuit is also larger.

In summary, in the Buck switching power converter circuit, if only the peak current during the on-time of one of the power tubes such as the switch tube is detected, and the current during the on-time of the freewheeling tube is calculated by this simulation, the simulation error is very large. Large, and also requires the operational amplifier to have a good response ability throughout the entire load detection cycle to ensure the accuracy of the current detection; if a general operational amplifier is used, the error of the above method will be greater.

The load current is detected by mirroring the current of the switching tube. There are also limitations in the Boost switching power converter circuit; as shown in Figure 6, the shaded part in the figure is the error of the load current, which is subject to the limited bandwidth of the op amp. There will be an error at the beginning of the test. In the Boost switching power converter circuit, because the load current is discontinuous, the response of the operational amplifier is required to be fast and the accuracy is high, and the error of the load current detected by the ordinary operational amplifier is large. Further, in the technical solution shown in FIG. 3, if the freewheeling tube is replaced by a diode, the circuit of the current mirror structure cannot be used to detect the load current of the non-synchronous rectification.

Glossary:

The meaning of the Buck switching power converter in this application is a step-down DC / DC conversion system using the Buck REGULATOR method; its input voltage is greater than the output voltage;

The meaning of the Boost switching power converter in this application is a boost DC / DC conversion system using a Boost REGULATOR method; its output voltage is greater than the input voltage;

The meaning of the Buck-Boost switching power converter in this application is a negative voltage DC / DC conversion system using the Buck-Boost REGULATOR method;

PWM is the abbreviation of Pulse Width Modulation in English, which means pulse width modulation in Chinese; pulse width modulation (PWM) switching power converter is to stabilize the output frequency of the control circuit by adjusting its duty cycle to achieve stability The purpose of the output voltage;

PFM is the abbreviation of Pulse and Modulation in English, which means pulse frequency modulation in Chinese; the pulse frequency modulation (PFM) switching regulator circuit is a "same-width frequency modulation" method, that is, the chopping frequency of the circuit is adjusted to achieve the purpose of stabilizing the output voltage .

CCM is the abbreviation of English Continuous Mode and Chinese meaning continuous conduction mode, which refers to the working mode in which the power tube in the boost circuit is alternately and continuously turned on so that the current in the inductor is continuously changed;

DCM: is the abbreviation of Discontinuous and Conduction Mode in English. The Chinese meaning is discontinuous conduction mode, which means that in the boost step-up circuit, the power tube is turned off one by one, so that the current in the inductor is a discontinuous change working mode.

Summary of the Invention

The technical problem to be solved by the present invention is to avoid the shortcomings of the prior art solutions described above, and a load current detection method and circuit of the inductive switching power converter are proposed, which greatly reduces the transient step of the operational amplifier in the load current detection. The requirement of response reduces the complexity of the load current detection circuit and improves the accuracy of load current detection.

The technical solution adopted by the present invention to solve the technical problem is a method for detecting a load current of an inductive switching power converter, which includes the following steps: obtaining a period of time during which the switching current converter ’s inductor current rises or falls during the Ath switching cycle; Time is recorded as T _A ; the time for obtaining the rising or falling period of the inductor current in the B switching period of the switching power converter is recorded as T _B , and B is equal to A + N; obtaining the rising period of the inductor current in the B switching period Or the first mid-point time T _{MB of the} falling period; the first mid-point time T _MB is the time after 0.5 T _A from the starting time of the rising or falling period of the inductor current in the B-th switching cycle; The second midpoint time T _{MC of the} rising or falling period of the inductor current in each switching cycle, C equals B + M; the second midpoint time T _MC is the rising or falling period of the inductor current in the Cth switching cycle starting from the time after the lapse 0.5T _B; where a, B, C, N and M are a natural number greater than or equal to 1; at the midpoint of the first sampling time T _MB load current, and through the sample and hold circuit The sample hold value to a second load current middle time T _MC; T _MB in the middle time to a second time period T _MC first midpoint in time, if the switching power converter is a Buck-type switching power converter, the The load current sampling signal is output during the inductor current rising and falling time periods; if the switching power converter is a Boost or Buck-Boost switching power converter, the load current sampling signal is output during the inductor current falling time period.

In the method for detecting load current of an inductive switching power converter, the load current sampling signal output by the sample-and-hold circuit is filtered by a low-pass filter and used as the load current signal of the switching power converter; or the load current sampling signal output by the sample-and-hold circuit After integration operation by the integration circuit, it is used as the load current signal of the switching power converter.

In the method for detecting a load current of an inductive switching power converter, when the switching power converter is a Buck switching power converter and the Buck switching power converter works in a CCM mode, the sampling moment of the load current is the first midpoint. Time T _MB is the starting point of the inductor current rising period or falling period of the Bth switching cycle. The time after 0.5T _A begins, where B = A + 1, that is, N = 1; the update time of the load current is the second midpoint. Time T _MC is the time after 0.5T _B begins at the beginning of the rising or falling period of the inductor current of the Cth switching cycle, where C = B + 1, that is, M = 1.

In the method for detecting a load current of an inductive switching power converter, when the switching power converter is a Buck switching power converter and the Buck switching power converter works in a DCM mode, the sampling moment of the load current is the first midpoint. Time T _MB is the starting point of the inductor current rising period or falling period of the Bth switching cycle. The time after 0.5T _A begins, where B = A + 1, that is, N = 1; the update time of the load current is the second midpoint. Time T _MC is the beginning of the rising or falling period of the inductor current of the Cth switching cycle. The time after 0.5T _B begins, where C = B + 1, that is, M = 1; when the inductor current is zero, the switch circuit passes Turn off the load current output, that is, during the time period when the inductor current is zero, the sampled and held load current value is not output to the outside.

In the method for detecting a load current of an inductive switching power converter, when the switching power converter is a Boost switching power converter or a Buck-Boost switching power converter, and the switching power converter works in a CCM mode; the load current The sampling time, ie, the first midpoint time T _MB, is the time after 0.5T _A begins at the beginning of the rising or falling period of the inductor current of the Bth switching cycle, where B = A + 1, that is, N = 1; load current The update time of the second mid-point time T _MC is the time after 0.5T _B starts at the beginning of the rising or falling period of the inductor current of the Cth switching cycle, where C = B + 1, that is, M = 1; During the period of current rise, the load current output is turned off by the switching circuit, that is, during the time period when the inductor current rises, the sampled and held load current value is not output to the outside.

In the method for detecting a load current of an inductive switching power converter, when the switching power converter is a Boost switching power converter or a Buck-Boost switching power converter, and the switching power converter works in a DCM mode; the load current The sampling time, ie, the first midpoint time T _MB, is the time after 0.5T _A begins at the beginning of the rising or falling period of the inductor current of the Bth switching cycle, where B = A + 1, that is, N = 1; load current The update time of the second mid-point time T _MC is the time after 0.5T _B starts at the beginning of the rising or falling period of the inductor current of the Cth switching cycle, where C = B + 1, that is, M = 1; During the current rising period, the load current output is turned off through the switch circuit, and the sampled and held load current value is not output to the outside; and when the inductor current is zero, the load current output is turned off through the switch circuit, and the sampled and held load is not output to the outside Current value.

The method for detecting a load current of an inductive switching power converter includes a step of using a switching signal of a switching power converter to obtain a midpoint time of a falling period or a rising period of an inductor current in a switching signal period. The step includes the following sub-steps : Generating the first midpoint detection control signal and the second midpoint detection control signal according to the switching signal of the switching power converter: dividing the switching signal into an odd-numbered period and an even-numbered period, and the first mid-point detection control signal is only switched in the odd number When the switching signal in the cycle is high, it is high, and the rest of the time is low; the second midpoint detection control signal is only when the switching signal in the even switching cycle is high. High level, the remaining moments are low level; that is, the first midpoint detection control signal or the upper second midpoint detection control signal is equal to the switching signal; a midpoint detection operational amplifier is set, and the non-inverting input terminal of the midpoint detection operational amplifier is set And the inverting input terminal are connected to the first midpoint detection capacitor and the second midpoint detection capacitor, respectively, The capacitance of the midpoint detection capacitor is the same, and the other terminals of the two capacitors are grounded; the first midpoint detection control signal and the second midpoint detection control signal are used to control the first midpoint detection capacitor and the second midpoint detection capacitor respectively. Charge and discharge process; the midpoint detection operational amplifier outputs the midpoint time signal according to the voltage input from the non-inverting input terminal and the inverting input terminal, the midpoint time signal includes the first midpoint time T _MB and the second midpoint time T _MC information .

The technical solution adopted by the present invention to solve the technical problem may also be an inductive switching power converter load current detection circuit, which includes a midpoint detection circuit for an inductor current rising period or a falling period, and a sample-and-hold for load current sampling and holding The midpoint detection circuit of the inductor current rising period or falling period is used to obtain the inductor current rising period or falling period during the Ath switching cycle, which is denoted as T _A , and is also used to obtain the inductance during the Bth switching period. The current rising period or falling period is denoted as T _B , and B is equal to A + N; the inductor current rising or falling period midpoint detection circuit is also used to obtain the first midpoint time T _MB and A second mid-point time T _{MC in} the C-th switching cycle; the first mid-point time T _MB is a time after 0.5 T _A from the start time of the rising or falling period of the inductor current in the B-th switching cycle; The second midpoint time T _MC is the time after 0.5 T _B from the starting point of the rising or falling period of the inductor current in the C-th switching cycle; where C is equal to B + M; A, B, C, N And M are both natural numbers greater than or equal to 1; the midpoint detection circuit of the inductor current rising period or falling period is electrically connected to the sample-and-hold circuit, and the inductor current rising period or falling period midpoint detection circuit outputs a midpoint moment signal To the sample-and-hold circuit; the mid-point time signal includes the first mid-point time T _MB and the second mid-point time T _MC information; the sample-and-hold circuit samples the load current at the first mid-point time T _MB and samples the load The current is maintained until the update time is the second midpoint time T _MC . During the period between the first midpoint time T _MB and the second midpoint time T _MC , if the switching power converter is a Buck-type switching power converter, Load current sampling signals are output during both the rising and falling inductor current periods; if the switching power converter is a Boost or Buck-Boost switching power converter, the load current sampling signals are output during the inductor current falling periods.

The inductive switching power converter load current detection circuit further includes a low-pass filter circuit; the low-pass filter circuit and the sample-and-hold circuit are electrically connected; and the load current sampling signal input from the sample-and-hold circuit to the low-pass filter circuit passes through The low-pass filter circuit outputs after low-pass filtering.

The midpoint detection circuit of the inductor current rising period or falling period includes a first midpoint detection switch, a second midpoint detection switch, a third midpoint detection switch, a fourth midpoint detection switch, a first midpoint detection capacitor, and a first Two midpoint detection capacitors, midpoint detection operational amplifiers, two current sources of the same size, namely a first current source and a second current source, where the first current source is used to inject current and the second current source is used to output current; An output terminal of a current source is electrically connected through a first midpoint detection switch and an inverting input terminal of the midpoint detection operational amplifier, and an output terminal of the first current source is also in phase through a second midpoint detection switch and a midpoint detection operational amplifier. The input terminals are electrically connected; the input terminal of the second current source is electrically connected through the third midpoint detection switch and the inverting input terminal of the midpoint detection operational amplifier, and the input terminal of the second current source is also connected through the fourth midpoint detection switch and the middle. The non-inverting input terminal of the point detection operational amplifier is electrically connected; the non-inverting input terminal of the midpoint detection operational amplifier is electrically connected to one end of the second midpoint detection capacitor. The other end of the second midpoint detection capacitor is grounded; the inverting input terminal of the midpoint detection operational amplifier is electrically connected to one end of the first midpoint detection capacitor, and the other end of the first midpoint detection capacitor is grounded; the first midpoint detection capacitor The capacitance value is the same as that of the second midpoint detection capacitor; the first and fourth midpoint detection switches are controlled by the first midpoint detection control signal; when the first midpoint detection control signal is high, the first Both the midpoint detection switch and the fourth midpoint detection switch are closed, so that both ends of the switch are turned on; when the first midpoint detection control signal is at a low level, both the first midpoint detection switch and the fourth midpoint detection switch are open, Disconnect both ends of the switch; the second midpoint detection switch and the third midpoint detection switch are controlled by the second midpoint detection control signal; when the second midpoint detection control signal is high, the second midpoint detection switch And the third neutral point detection switch are both closed, so that both ends of the switch are turned on; when the second neutral point detection control signal is at a low level, both the second neutral point detection switch and the third neutral point detection switch are opened, making both ends of the switch Open connection; the first midpoint detection control signal or the second midpoint detection control signal is equal to the switching signal of the inductive switching power converter; when the switching signal is in an odd number of cycles, the high voltage of the first midpoint detection control signal Level is the same as the high level of the switching signal; when the switching signal is in an even number of cycles, the high level of the second midpoint detection control signal is the same as the high level of the switching signal; the output terminal of the midpoint detection operational amplifier outputs the first A midpoint time signal, the first midpoint time signal is transmitted to the sample and hold circuit, and controls the sampling time of the sampling circuit.

The midpoint detection circuit of the inductor current rising period or falling period further includes a D flip-flop and an exclusive-OR gate; a clock signal of the D flip-flop is an externally input switching signal for controlling an inductive switching power converter; the The first input terminal of the D flip-flop is electrically connected to the second output terminal of the D flip-flop, and the first output terminal of the D flip-flop outputs a signal to one input terminal of the XOR gate; the output of the midpoint detection operational amplifier The terminal outputs a first midpoint time signal to another input terminal of the XOR gate. The output terminal of the XOR gate outputs a second midpoint time signal. The second midpoint time signal is transmitted to the sample-and-hold circuit to control the sampling circuit. Sampling time.

A first output terminal of the D flip-flop outputs a signal to a first AND gate, performs an AND operation with a switching signal controlled by an inductive switching power converter, and outputs a first midpoint detection control signal; a second of the D flip-flop The output terminal outputs a signal to a second AND gate, performs an AND operation on a switching signal controlled by the inductive switching power converter, and outputs a second midpoint detection control signal.

The sample-and-hold circuit includes a second sample-and-hold switch, a second sample-and-hold capacitor, a third sample-and-hold switch, a third sample-and-hold capacitor, and a sample-and-hold operational amplifier. One end of the second sample-and-hold switch is used for external inductor current detection. The circuit connection acquires the load current sampling signal. The other end of the second sample-and-hold switch is electrically connected to one end of the second sample-and-hold capacitor and the third sample-and-hold switch at the same time, and the other end of the second sample-and-hold capacitor is grounded. The other end of the switch is electrically connected to the non-inverting input terminal of the sample and hold operational amplifier and one end of the third sample and hold capacitor, and the other end of the third sample and hold capacitor is grounded; the inverting input terminal of the sample and hold operational amplifier and the The output terminals are electrically connected; the second sample-and-hold switch is controlled by the non-signal of the signal at the second midpoint time. When the non-signal of the signal at the second mid-point time is high, the second sample-and-hold switch is closed to make both ends of the switch on. When the non-signal of the signal at the second midpoint is low, the second sampling Holding the switch open disconnects both ends of the switch; the third sample-and-hold switch is controlled by the second midpoint signal, and when the signal at the second midpoint is high, the third sample-and-hold switch is closed and the two ends of the switch are turned on When the signal at the second midpoint is low, the third sample-and-hold switch is opened to disconnect the two ends of the switch.

The inductive switching power converter load current detection circuit further includes an inductor current zero-crossing detection circuit for obtaining a low-pass filtered switch control signal.

The low-pass filter circuit and the sample-and-hold circuit are electrically connected through a low-pass filter switch; the low-pass filter switch is controlled by a low-pass filter switch control signal output from the inductor current zero-crossing detection circuit; when the inductor current is zero When the low-pass filter switch control signal controls the low-pass filter switch to open, the two ends of the switch are disconnected, so that the low-pass filter circuit and the sample-and-hold circuit are disconnected, and the input of the low-pass filter is disconnected. Grounding; when the inductor current is non-zero, the low-pass filter switch control signal controls the low-pass filter switch to close to make both ends of the switch on, thereby electrically connecting the low-pass filter circuit and the sample-and-hold circuit.

The inductive switching power converter load current detection circuit further includes a low-pass filter input pull-down MOS tube, which is used to pull down the low-pass filter after the connection between the low-pass filter circuit and the sample-and-hold circuit is disconnected. Input so that the low-pass filter input is zero.

The low-pass filter circuit includes one or more low-pass filters.

When the low-pass filter circuit is a first-level RC low-pass filter, the first-level RC low-pass filter includes a low-pass filter resistor and a low-pass filter capacitor; one end of the low-pass filter resistor and one end of the low-pass filter switch Electrical connection, at the same time, one end of the low-pass filter resistor is electrically connected to the source of the low-pass filter input pull-down MOS tube, and the gate of the low-pass filter input pull-down MOS tube is connected to a non-signal of a low-pass filter switch control signal, The drain of the low-pass filter input pulls down the drain of the MOS tube; the other end of the low-pass filter resistor is used as the output terminal of the low-pass filter circuit, and the other end of the low-pass filter resistor is also connected to one end of the low-pass filter capacitor. Electrically connected, the other end of the low-pass filter capacitor is grounded.

The inductive switching power converter load current detection circuit further includes an inductive current detection circuit for sampling and obtaining a load current; the inductive current detection circuit is electrically connected to the sample-and-hold circuit; and the inductive current-detection circuit is sample-and-hold The circuit outputs a load current signal.

The technical solution adopted by the present invention to solve the technical problem may also be an inductive switching power converter circuit, which includes the load current detection circuit of the switching power converter according to any one of the above.

The inductive switching power converter circuit further includes a logic control circuit; the logic control circuit is used to generate a basic switching signal for the timing control of the inductive switching power converter; and the logic control circuit generates a control signal for controlling two The first control signal GP and the second control signal GN of each power switch tube; when the first control signal GP is high level, one of the power tubes is turned on; when the first control signal GP is low level, the other power tube is turned on; A control signal GP and a second control signal GN are synchronous conversion signals of the basic switching signal; the inductor current rise time period and the inductor current fall time period are synchronized with the first control signal GP and the second control signal GN; thus the inductor current rise time The period and the inductor current drop period are also synchronized with the basic switching signal.

Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Through clever timing control, according to the inductor current rising period or falling period of the elapsed switching period, simulate the acquisition of the current switching period inductance rising period or falling period. The midpoint of the inductor, and the sample and hold performed cleverly at this moment, making full use of the characteristic that the inductor current linearly changes during the rising or falling period. At the same time, when the load current is constant, the midpoint of the inductor current rising is equal to the inductor current falling. The midpoint can greatly simplify the load detection circuit; 2. At the same time, because the sampling time is close to or approximately the midpoint of the on-time of the switch tube or the on-time of the freewheeling tube, the sampling current is usually the best for working in the op amp. Within the range of the response interval, the accuracy of the overall load current detection is also improved, which not only avoids the complicated circuit design, but also improves the detection accuracy of the load current, reducing the complexity and design difficulty of the circuit; 3. The circuit structure is simple Ingenious, strong applicability can use Buck, Boost and Buck-Boost various DC / DC switching power supply conversion ; Whether it is a switching tube or a freewheeling tube, this method can be used to restore the size of the load current with strong flexibility; it is also suitable for synchronous and non-synchronous rectification circuits, and is commonly used for power tube proportional current detection and series resistance current detection circuits; In integrated circuit applications, it is easy to deploy applications and save chip area.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a principle schematic block diagram of a preferred embodiment of a load current detection circuit according to the present invention;

2 is one of the schematic block diagrams of the prior art load current detection circuit in the application of DC / DC switching power converter circuit;

3 is a second schematic block diagram of the principle of a prior art load current detection circuit in a DC / DC switching power converter circuit application;

FIG. 4 is a schematic diagram illustrating the corresponding timing and error description of the inductor current and load current detection when the circuit in FIG. 3 works in the Buck-type CCM mode;

FIG. 5 is a schematic diagram illustrating the corresponding timing and error description of the inductor current and load current detection when the circuit in FIG. 3 works in the Buck-type DCM mode;

FIG. 6 is a schematic diagram illustrating the corresponding timing and error description of the inductor current and load current detection under the Boost CCM mode of the circuit in FIG. 3; FIG.

7 is a characteristic analysis diagram of an inductor current of an inductive switching power converter;

8 is a schematic diagram of an inductor current timing of an inductive switching power converter;

9 is a principle schematic block diagram of a preferred embodiment of a load current detection circuit of the present invention in a DC / DC switching power converter circuit application;

10 is a schematic circuit diagram of a preferred embodiment of a midpoint detection circuit for rising or falling inductor current in FIG. 1;

FIG. 11 is a timing relationship diagram of signals in the application example of the Buck switching power converter in FIG. 10; FIG.

FIG. 12 is a schematic block diagram of a circuit principle of a preferred embodiment of a load current detection circuit according to the present invention; a sample-and-hold circuit 34 and a low-pass filter 35 are shown in the figure;

FIG. 13 is a schematic circuit configuration diagram of a preferred embodiment of the low-pass filter 35;

14 is a schematic diagram showing a relationship between a transient response curve of a sampling current signal of an operational amplifier and a load current in the prior art;

15 and 16 are signal timing diagrams of the present invention when the switching power converter is a Buck-type switching power converter and the Buck-type switching power converter operates in the CCM mode; in FIG. 15, the current sampling time is in the inductor current rising period ; In Figure 16, the current sampling time is in the inductor current drop period;

17 and 18 are signal timing diagrams of the present invention when the switching power converter is a Buck-type switching power converter and the Buck-type switching power converter operates in the DCM mode; in FIG. 17, the current sampling time is in the inductor current rising period ; Figure 18, the current sampling time is in the inductor current drop period;

19 and 20 are signal timing diagrams of the present invention when the switching power converter is a Boost or Buck-Boost switching power converter, and the switching power converter operates in the CCM mode; in FIG. 18, the current sampling time is at Inductor current drop period; in Figure 19, the current sampling moment is in the inductor current rise period;

21 and 22 are signal timing diagrams of the present invention when the switching power converter is a Boost or Buck-Boost switching power converter, and the switching power converter operates in the DCM mode; in FIG. 21, the current sampling time is at Inductor current drop period; in Figure 22, the current sampling time is in the inductor current rise period.

detailed description

The embodiments of the present invention are described in further detail below with reference to the accompanying drawings.

The basic principle of the inductive switching power converter is to use the energy storage characteristics of the inductor to achieve the voltage change. The rate of change of the inductor current is equal to the voltage across the inductor divided by the Henry value of the inductor.

The change of the inductor current is a linear process. The speed of the inductor current changes, that is, the slope of the linear change of the inductor current is related to the voltage across the inductor and the inductance value. When the applied voltage across the inductor is constant and the inductance value is also determined, the inductor current rises. And the slope of the drop is also fixed.

The basic characteristics of the switching power converter referred to in the present invention include: In the CCM operating mode, the switching power converter controls two power switching tubes to be turned on alternately through a logic control circuit. One switching cycle includes an inductor current rising time period. And inductor current drop time period; in DCM operating mode, the switching power converter controls the two power switch tubes to be turned on alternately and turned off at intervals through a logic control circuit, that is, in a switching cycle, including the inductor current rise time period, the inductance The current fall time period and the time period when the inductor current is zero.

The logic control circuit in the switching power converter not only generates the basic switching signals of the switching power converter, such as a PWM switching signal, but also generates a first control signal GP and a second control signal GN for controlling two power switching tubes; the first When the control signal GP is high, one of the power tubes is turned on; when the second control signal GN is low, the other power tube is turned on; the first control signal GP that controls the switch tube and the second control signal GN that controls the freewheeling tube Both are generated based on the PWM switching signals, so the first control signal GP and the second control signal GN are transformed signals of the PWM signals, and the signals are synchronized. The inductor current rise time period and inductor current fall time period are synchronized with the first control signal GP and the second control signal GN; and the first control signal GP and the second control signal GN are synchronized with the PWM switching signal, so it is possible The high and low periods of the PWM switching signal are used to obtain the inductor current rising time period and the inductor current falling time period.

As shown in Figure 7, the inductor current of the inductive switching power converter is a triangular wave. It can be seen from the figure that the inductor current climbs from T0 to T1, and 0.5T1 is the midpoint of the inductor current climb; from T1 to T3 At the moment, the inductor current decreases downward, and T2 is the midpoint moment of its decrease. When the load current is constant, the starting point of the rise of the inductor current is equal to the end point of the drop in each switching cycle. If not, if the end point of each drop is higher than the starting point of the rise, the inductor current will always increase, otherwise Just keep getting smaller. Therefore, at time T0 and time T3, the magnitude of the inductor current is the same. If the midpoint of the rising edge of the inductor and the midpoint of the falling are connected, this line segment is parallel to the X axis, that is, the midpoint of the rising of the inductor current is equal to the midpoint of the falling of the inductor current, so the midpoint of the rising period of the inductor current and the sampling The midpoint of the inductor current drop period is an equivalent change.

As shown in FIG. 7, if the starting current of the inductor current rising period is equal to the ending current of the inductor falling period and has a peak current, it is shown in FIG. 7. The area of the first triangle 1 is equal to the area of the second triangle 2. The area of the third triangle 3 is equal to the area of the fourth triangle 4. For any type of inductive switching power converter using an inductor, according to the characteristic that the inductor current changes linearly within this interval, as long as the size of the inductor current at 0.5T1 or T2 is found, and the current at the sampling time is measured. Sample and hold can be converted into the load current through simple calculations. If the midpoint moment of the rising edge of the inductor current is 0.5T1 or the midpoint moment of the falling inductor current is T2, that is, the inductor current at the midpoint of the triangular current of the inductor current, the load current of the entire switching cycle can be calculated. Therefore, the above two This is the key point of sampling current at this moment. To obtain the midpoint of the rising or falling period of the inductor current of the current switching cycle, the real-time characteristics of the circuit are often very high. In the present invention, the total of the rising or falling period of the inductor current in the elapsed switching cycle is first obtained. At time T, the midpoint of the current cycle is replaced by the time from the beginning of the cycle to 0.5T, and the load current of the full switching cycle is obtained through the corresponding sample-and-hold strategy.

As shown in Figure 7, for a Buck switching power converter circuit, the sampled midpoint current is I _h . Since the inductor current outputs energy to the outside during the rise and fall,

As shown in Figure 7, for Boost or Buck-Boost converters, the external output is discharged only when the inductor current is decreasing, so

As shown in Figure 8, when n is 1, the total time for the inductor current to rise during the first cycle is Ta, the total time for the inductor current to rise during the second cycle is Tb, and the total time for the inductor current to rise during the third cycle Is Tc. At the midpoint of the second cycle: T _MB = T1 + 0.5Ta, and at the midpoint of the third cycle: T _MC = T2 + 0.5Tb. For the same reason, the same method can be used to collect the midpoint of the falling period. When the load current does not change, the peak value and the bottom value of the inductor current do not change. Therefore, the midpoint of the rising period of the inductor current and the midpoint of the falling period are the same, and can be flexibly selected according to the actual application.

FIG. 9 is a schematic block diagram of a load current detection circuit for implementing a load current detection method in a DC / DC switching power converter circuit application according to the present invention.

In FIG. 9, if the circuit terminal V1 is an external power input terminal of the switching power converter, and the circuit terminal V2 is connected to a capacitor as an output terminal of the switching power converter, the switching power converter is a Buck switching power converter. The transistor Q1 in the figure is a PMOS transistor used as a switching transistor, and the transistor Q2 in the figure is an NMOS transistor used as a freewheeling transistor.

In FIG. 9, if the circuit terminal V2 is an external power input terminal of the switching power converter and the circuit terminal V1 is used as an output terminal of the switching power converter, the switching power converter is a Boost type switching power converter. The transistor Q2 is an NMOS transistor used as a switching transistor, and the transistor Q1 in the figure is a PMOS transistor used as a freewheeling transistor.

The current midpoint sample-and-hold circuit indicated by reference numeral 41 in FIG. 9 is also the load current detection circuit of the switching power converter according to the present invention.

In FIG. 9, the inductor current is input to the current midpoint sampling and holding circuit 41. The current midpoint sampling and holding circuit 41 outputs a load current signal, which is an IFB signal, and the output voltage sampling circuit 40 outputs a voltage feedback signal, which is a VFB signal, and a load current signal, which is IFB. The signal and the output voltage feedback signal, that is, the VFB signal and the reference reference voltage VBG signal, are transmitted to the internal CC / CV error amplifier 42. The CC / CV error amplifier 42 outputs the signal to the PWM comparator 44; the output signal of the CC / CV error amplifier 42 And the output signal of the slope compensation circuit 43 are input to the control PWM comparator 44. The PWM comparator 44 outputs the PWM control signal to the logic control module 45. The output of the logic control module 45 is controlled by controlling the output of the PWM comparator 44 so that each The PWM signal of each cycle is controlled by the feedback load current signal, so as to control the power output stage to control the maximum output load current, so as to achieve the purpose of constant maximum output current. FIG. 9 only shows an embodiment of a switching mode power converter in the PWM mode. In fact, the technical solution of the present invention is also applicable to a switching mode power converter circuit in the PFM mode.

As shown in FIG. 1, it is a circuit block diagram of one of the preferred embodiments of the present invention, including a midpoint detection circuit 32 of an inductor current rising period or a falling period, an inductor current detection circuit 30, an inductor current zero-crossing detection circuit 31, and a sample-and-hold circuit 34. And low-pass filter 35.

As shown in FIG. 1, the midpoint detection circuit 32 of the rising or falling period of the inductor current obtains the total time of the rising or falling period of the inductor current of the switching power converter during the Ath switching cycle, and records it as T _A , the Bth The total time during which the inductor current rises or falls during the switching period is denoted as T _B. The first inductor current rise period or fall period is 0.5T _A , which is the time after the first midpoint time T _{MB is} sampled from the start time of the B-th inductor current rise or fall period, and the load current sample value is held to the second midpoint time T by the sample-and-hold circuit. _MC ; the second mid-point time T _MC is the C-th switching cycle, the time after the start point of the inductor current rising or falling period passes 0.5T _B ; at the first mid-point time T _MB to the second mid-point time T _MC During this period, the sampling current value of T _MB at the first midpoint is sampled and held. Where A, B and C are all natural numbers greater than or equal to 1, B = A + 1, C = B + 1;

The application of the present invention to a Buck switching power converter is described in detail below. Assume that the Buck-type switching power converter works in CCM mode, that is, continuous operation mode, and the output load current is equal to the average value of the inductor current. In the absence of a load current sampling resistor, it is difficult to directly sample the current on the inductor, but the inductor current is divided into two parts, one of which is that when the switch is turned on, the current flowing through the switch is equal to the current of the inductor. The current flowing through the freewheeling tube is 0. Another part of the inductor current is that when the freewheeling tube is open, the current flowing through the freewheeling tube is equal to the current of the inductor, and the current flowing through the switching tube is 0, so the load current flows through the switch. The average of the sum of the currents of the tube and the freewheeling tube. When the load current is constant, the current flowing through the switch tube in each switching cycle is a linearly increasing current; accordingly, in the present invention, the time T of the switch tube being turned on in the previous cycle is first obtained, and the switch tube is turned on in the current cycle. When the time continues for T / 2, the inductor current is sampled as the load current, and the sampled value of the load current at this moment is maintained until the switch-on time of the next cycle reaches half of the switch-on time of the previous cycle. Assuming that the Buck switching power converter works in DCM mode, that is, discontinuous operation mode, it is only necessary to keep the sampled value until the time when the freewheeling tube is closed. When the switch and freewheeling tube are not conducting, no current flows out. To the load, the output voltage is maintained only by the output capacitor; the sample-and-hold value of the sample-and-hold circuit is not output to the outside when the switch tube and the freewheeling tube are not conducting.

For Boost or Buck-Boost switching power converters, the same method can be used to sample the load current at the midpoint of the on-time of the freewheeling tube, and sample and hold the load current sample value; freewheeling in the current switching cycle During the time period when the tube is turned on, the load current sampling value sampled and held in the previous cycle is output, and the current cycle load current sample value can be refreshed until the starting point of the freewheeling tube in the current switching cycle to half of the previous period. . Finally, the sampled and held load current signal is output after passing through the low-pass filter, as the load current of the switching power converter in this period. The present invention does not need to accurately sample the entire period of the inductor current of the entire switching cycle. It only needs to sample the load current from the starting point of the switching cycle to half of the previous period on time during the current switching cycle, and The load current sampling value is sampled and held until the next update time, and the full cycle load current can be accurately obtained. In this way, the requirements for the load current detection circuit and the sampling circuit are greatly reduced, the circuit complexity is reduced, and the accuracy of the load detection is improved. Especially during the full period of the switch tube and freewheeling tube alternately conducting, the current change of the switch tube and freewheeling tube usually needs to go through a process from zero or linearly increasing from the base current to the peak current. The current of the tube and the freewheeling tube places high requirements on the operational amplifier in the current detection circuit. The operational amplifier is required to have a full frequency band response capability, otherwise the current sampling error during the full cycle is unavoidable.

In the PWM switching power converter circuit, the rising or falling period of the inductor current corresponds to the on-time and off-time of the switch; the pulse width of the PWM switching signal is equal to the on-time of the switch or freewheeling tube. The first control signal GP and the second control signal GN of the switch tube and the freewheeling tube are generated based on the PWM switching signal. Therefore, the first control signal GP and the second control signal GN are transformed signals of the PWM signal. Are synchronized. In addition, when the switching tube or freewheeling tube is turned on to closed, the inductor current rises linearly during this period, so the midpoint of the rising or falling inductor current is half of the pulse width of the PWM, GP, or GN switching signal. Therefore, only the midpoint of the pulse width of the PWM switching signal needs to be detected to find the midpoint of the inductor current. After the sample-and-hold circuit obtains the information of the above-mentioned midpoint time, it can sample the current at the midpoint time and sample and hold the output until the midpoint time of the on-time of the switch tube in the next PWM switching signal cycle.

In the present invention, the time of half of the on-time of the switch during the previous PWM switching signal period is used to replace the time of half of the on-time of the switch during the current PWM switching signal period. When the period of the PWM switching signal is stable, it can be very clever. And a simple circuit completes the control of the sampling moment. Even during the period of the PWM switching signal change, because the on-period information in the two adjacent periods is used, the PWM only lags the inductor current by one or more switching cycles, which basically achieves real-time detection, and the load current also has to pass Subsequent low-pass filters can only be obtained after averaging, which has no effect on the accuracy of inductor current detection.

As shown in FIG. 10, in a specific embodiment of the midpoint detection circuit 32 of the inductor current rising period or falling period of the present invention, it includes two first current sources I1 and second current sources I2 of the same size. Point detection operational amplifier OP1, four midpoint detection switches, namely first midpoint detection switch, second midpoint detection switch, third midpoint detection switch and fourth midpoint detection switch, and two first The midpoint detection capacitor CA and the second midpoint detection capacitor CB. FIG. 11 is a timing relationship diagram of signals in FIG. 10.

As shown in Figs. 10 and 11, the first midpoint detection control signal Φ1 and the second midpoint detection control signal Φ1B are signals generated by the PWM switching signal of the switching power converter; as shown in Fig. 10, the first The midpoint detection control signal Φ1 and the second midpoint detection control signal Φ1B are signals obtained after the first control signal GP or the second control signal GN passes through the cloud, respectively. When the PWM switching signal is in an odd number of cycles, the high level of the first midpoint detection control signal Φ1 is the same as the high level of the PWM switching signal; when the PWM switching signal is in an even number of cycles, the second midpoint detection control The high level of the signal Φ1B is the same as the high level of the PWM switching signal. The relationship between the first midpoint detection control signal Φ1 and the second midpoint detection control signal Φ1B is that the first midpoint detection control signal Φ1 or the upper second midpoint detection control signal Φ1B is equal to the PWM switching signal.

As shown in Figures 10 and 11, the first current source I1 and the second current source I2 are current sources of the same size, where the first current source I1 is used to inject current and the second current source I2 is used to output current; assuming the first The capacitances of the midpoint detection capacitor CA and the second midpoint detection capacitor CB are equal, and the initial value of the non-ground terminal to ground is 0, that is, the positive input terminal and the negative input terminal of the midpoint detection operational amplifier OP1. Voltage VC1 = VC2 = 0, in the pulse width period of the first PWM switching signal, the first midpoint detection control signal Φ1 is high level Φ1 = 1, and the second midpoint detection control signal Φ1B is low level, that is, Φ1B = 0, the first midpoint detection capacitor CA starts to charge to VC1 = Vch, and the second midpoint detection capacitor CB is discharged to VC2 = 0; both the first midpoint detection control signal Φ1 and the second midpoint detection control signal Φ1B When it is low level, ie, Φ1 = Φ1B = 0, the voltage VC1 on the first midpoint detection capacitor CA and the voltage VC2 on the second midpoint detection capacitor CB are maintained; in the pulse width period of the second period PWM switching signal , The first midpoint detection control signal Φ1 is at a high level φ1 = 1, and the second midpoint detection System to a low level signal Φ1B φ1B = 0, the midpoint of the first voltage VC1 on capacitor CA is detected from the start of discharge Vch, the voltage VC2 on the midpoint of the second detection capacitor CB from 0 to start charging. Because CA = CB and I1 = I2, when VC1 = VC2, the level of the MID signal output by the midpoint detection operational amplifier is reversed, and the moment of inversion is the PWM pulse midpoint of the previous cycle of the PWM switching signal.

As shown in FIG. 12, it is a schematic circuit diagram of one of the preferred embodiments of the load current detection circuit of the present invention. The figure shows the midpoint detection circuit 32, the inductor current detection circuit 30, and the inductor current The zero detection circuit 31, the sample-and-hold circuit 34, and the low-pass filter 35.

As shown in FIG. 12, the sample and hold circuit 34 includes a second sample and hold switch, a second sample and hold capacitor C2, a third sample and hold switch, a third sample and hold capacitor C3, and a sample and hold operational amplifier. One end is used to connect to the external inductor current detection circuit 30 to obtain a load current sampling signal. The other end of the second sample-and-hold switch is electrically connected to one end of the second sample-and-hold capacitor and one end of the third sample-and-hold switch at the same time. The other end of the capacitor is grounded; the other end of the third sample-and-hold switch is electrically connected to the non-inverting input terminal of the sample-and-hold operational amplifier and one end of the third sample-and-hold capacitor, and the other end of the third sample-and-hold capacitor is grounded; The inverting input terminal is electrically connected to the output terminal of the sample-and-hold operational amplifier; the second sample-and-hold switch is controlled by the non-signal of the signal at the second midpoint

When the signal is not at the second midpoint

When the level is high, the second sample and hold switch is closed to make both ends of the switch on. When the non-signal of the signal at the second midpoint is low, the second sample and hold switch is opened to disconnect the two ends of the switch. The hold switch is controlled by the second midpoint signal D50C. When the second midpoint signal D50C is high, the third sample and hold switch is closed to make both ends of the switch on. When the second midpoint signal D50C is low, Usually, the third sample-and-hold switch is turned on to disconnect the two ends of the switch.

As shown in FIG. 12, the low-pass filter circuit 35 and the sample-and-hold circuit 34 are electrically connected through a low-pass filter switch; the low-pass filter switch is controlled by the low-pass filter output from the inductor current zero-crossing detection circuit 31. Non-signal of switch control signal ZC

At this time, the load current detection circuit of the switching power converter further includes an inductor current zero-crossing detection circuit 31 for obtaining a low-pass filtered switch control signal ZC and its non-signal.

Logic NOT signal for ZC.

For a Buck-type switching power supply circuit, when the low-pass filter switch control signal ZC is zero, the low-pass filter switch control signal controls the low-pass filter switch to open, disconnecting both ends of the switch, so that the two ends of the switch are disconnected. The low-pass filter circuit 35 and the sample-and-hold circuit 34 are disconnected; when the inductor current is non-zero, the low-pass filter switch control signal controls the low-pass filter switch to be closed so that both ends of the switch are turned on, so that the low-pass The filter circuit 35 and the sample-and-hold circuit 34 are electrically connected.

For Boost or Buck-Boost switching power supply circuits, the low-pass filter switch control signal ZC is high when the inductor current is zero or the switch is on, and the low-pass filter switch control signal ZC controls the low-pass filter switch to open. So that the low-pass filter circuit 35 and the sample-and-hold circuit 34 are disconnected and the low-pass filter input is pulled to ground; when the inductor current is non-zero and the freewheeling tube is turned on, the low-pass filter switch controls The signal controls the low-pass filter switch to be closed, so that the low-pass filter circuit 35 and the sample-and-hold circuit 34 are electrically connected.

As shown in FIG. 12, the low-pass filter circuit 35 includes a low-pass filter resistor and a low-pass filter capacitor; the sample-and-hold circuit 34 further includes a low-pass filter input pull-down for controlling the input of the low-pass filter when the inductor current is zero. MOS tube; one end of the low-pass filter resistor is electrically connected to one end of the low-pass filter switch, and one end of the low-pass filter resistor is electrically connected to the source of the low-pass filter input pull-down MOS tube, and the low-pass filter input The gate of the pull-down MOS tube is connected to the low-pass filter switch control signal ZC, and the drain of the low-pass filter input is pulled down to the ground of the MOS tube. The other end of the low-pass filter resistor is used as the output terminal of the low-pass filter circuit 35. The other end of the low-pass filter resistor is also electrically connected to one end of the low-pass filter capacitor, and the other end of the low-pass filter capacitor is grounded.

As shown in Figure 13, another embodiment of the low-pass filter includes two stages of RC low-pass filters with the same circuit parameters. The resistance and capacitance of each two-stage filter are 1MΩ and 4pF, which are suitable for switching. When the signal frequency is 500MHz. The parameters of the low-pass filter can be selected according to the actual situation, such as selecting appropriate low-pass filtering parameters according to different maximum load currents, current sampling ratios, switching signal frequency and loop gain of the corresponding circuit.

In conjunction with the sample-and-hold circuit 34 shown in FIG. 12, it is assumed that the switching power converter is a Buck-type switching power converter and the Buck-type switching power converter operates in the CCM mode. After the sample-and-hold circuit 34 detects the inductor current signal, it passes through The point detection circuit obtains the second midpoint time signal D50C. In the first half of the PWM switching signal, the second sample-and-hold capacitor C2 samples the magnitude of the inductor current. When it reaches the time given by the midpoint detection circuit, it is the second midpoint time signal. After the first sampling time given by D50C is reached, the second sample-and-hold capacitor C2 and the third sample-and-hold capacitor C3 are short-circuited by a switch, where C2 >> C3, so that the upper voltage of the third sample-and-hold capacitor C3 and the second sample-and-hold capacitor The voltage of C2 at the time of sampling remains the same. The sample-and-hold operational amplifier is held until the sampling time of the next PWM switching signal cycle. The electrical connection between the third sample-and-hold capacitor C3 and the second sample-and-hold capacitor C2 is disconnected, and the second sample-and-hold capacitor C2 is used to sample a new PWM switch. The amount of inductor current in the signal period.

In conjunction with the sample-and-hold circuit 34 shown in FIG. 12, it is assumed that the switching power converter is a Buck switching power converter and the Buck switching power converter operates in the DCM mode. The other operating timing and the Buck switching power converter operate in the CCM. The mode is the same, except that when the inductor current becomes zero, that is, when the signal of the low-pass filter switch control signal is high, ZC = 1, and the low-pass filter switch is controlled to open, so that the sample-and-hold circuit 34 and the low-pass filter The electrical connection between the circuits 35 is broken, and the input of the low-pass filter is pulled to ground through the low-pass filtering input pull-down MOS tube, so that the current output by the low-pass filtering circuit 35 can truly characterize the load current of the switching power converter. size.

In conjunction with the sample-and-hold circuit 34 shown in FIG. 12, it is assumed that the switching power converter is a Boost type or a Buck-Boost switching power converter and the switching power converter works in the CCM mode. The other working timing and Buck switching power supply conversion The converter works in the same CCM mode, the difference is that only the load current is sampled and held during the on-time of the freewheeling tube, and during the on-time of the switch, the signal of the low-pass filter switch control signal is high, that is, ZC = 1, thereby disconnecting the sample-and-hold circuit from the low-pass filter circuit 35. In this way, the sample-and-hold current is only the current of the freewheeling tube, and the average is obtained by the low-pass filter, which is a Boost or Buck-Boost switching power supply conversion. The load current in the CCM mode.

In conjunction with the sample-and-hold circuit 34 shown in FIG. 12, it is assumed that the switching power converter is a Boost or Buck-Boost switching power converter and the switching power converter operates in a DCM mode. The other working timings are Boost or Buck-Boost. Type switching power converter works in the same CCM mode, the difference is that when the inductance becomes zero, the signal of the low-pass filter switch control signal will be high level, that is, ZC = 1, which controls the low-pass filter switch to open and break. The open sample-and-hold circuit is connected to the low-pass filter circuit 35, and the output of the low-pass filter circuit 35 is pulled to ground without waiting for the switch to turn on before setting the signal of the low-pass filter switch control signal to a high level. The output of the pass filter circuit 35 is the actual load current of the Boost or Buck-Boost switching power converter in the DCM mode.

As shown in the prior art, the operational amplifier response curve and the relationship with load current are shown in the prior art. The dashed line in the figure indicates the actual transient response curve of the operational amplifier. During the load current rising from near zero, the prior art operational amplifier needs to be tracked. The magnitude of the inductor current during the entire rise time of the detection output, the finite gain and response time of the op amp require a certain response time. The initial stage of the inductor current detection error is large, which will also affect the accuracy of the load current detection throughout the cycle. Because the present invention only needs to sample at the midpoint, there is enough time to establish the operational amplifier response from the time when the inductor current climbs from the low point to the midpoint. The error of the op amp response in the initial stage does not affect the accuracy of the sampling current. . Therefore, the design difficulty and requirements of operational amplifiers are greatly reduced.

15 is a signal timing diagram of the present invention when the switching power converter is a Buck-type switching power converter operating in CCM mode, and the Buck-type switching power converter performs load current sampling during an inductor current rising period; as can be seen in the figure, After the first inductor current rise period T1 starts, the mid-point current sampling value Vsen1 of the previous cycle is first output, and the input signal Vsen2 of the low-pass filter is equal to Vsen1. When the time reaches half of the previous inductor current rise period T0, it is updated The inductor current sampling value Vsen1 is output to the low-pass filter at the same time. The input voltage Vsen2 of the low-pass filter is equal to Vsen1 until the next inductor current rising period T2 reaches the time of 0.5T1. When the time of T2 period reaches 0.5T1, the current is sampled again, and the updated midpoint current sampling value Vsen1 is maintained until the time of T3 period reaches 0.5T2; the cycle is repeated and will not be repeated. Because when the switching tube and the freewheeling tube are turned on, the switching power converter outputs current to the load, the load current I _load should be the sum of the switching tube and freewheeling tube currents. In the figure, the current feedback signal IFB is a load current signal that represents the magnitude of the load current after the sampled and held load current value is filtered by a low-pass filter.

FIG. 16 is a signal timing diagram of the present invention when the switching power converter is a Buck-type switching power converter operating in the CCM mode, and the Buck-type switching power converter performs load current sampling during an inductor current drop period. Different from FIG. 15, the sample-and-hold circuit samples and updates the current sampling value Vsen1 at the midpoint of the inductor current drop period, and samples and updates the current sample value again at the midpoint of the next inductor current drop period.

17 is a signal timing diagram of the present invention when the switching power converter is a Buck-type switching power converter operating in the DCM mode, and the Buck-type switching power converter performs load current sampling during an inductor current rising period; After the inductor current rise period T1 starts, the midpoint sampling signal Vsen1 of the previous period is first output, and the input Vsen2 of the low-pass filter is equal to Vsen1. When the time reaches half of the previous inductor current rise period T0, the sampling updates the midpoint current sampling. The value Vsen1, when the over-inductance current zero detection circuit detects that the inductor current drops to zero, makes the low-pass filter input signal Vsen2 = 0. When the next inductor current rising period T2 comes, first output the mid-point sampling current sampling value Vsen1 in the T1 period, and when it reaches 0.5T1, sample and update the mid-point current sampling value Vsen1 again, and keep it until the freewheeling tube is turned off, and then turn the low-pass The input signal Vsen2 of the filter is pulled to ground. Repeatedly, I will not repeat them. In a single switching cycle, the magnitude of the output load current I _load should be the rectangular area with the same shaded line in one switching cycle in FIG. 17, that is, the integrated value of the load current divided by the time of the integration period. In the DCM mode, the inductor current will drop to zero, the inductor current is discontinuous, so the sampling of the inductor current is also discontinuous, and the load current is the average value of this discontinuous current. Therefore, the magnitude of the load current I _load in this mode will be Less than the midpoint sampling current.

FIG. 18 is a signal timing diagram of the present invention when the switching power converter is a Buck-type switching power converter operating in the DCM mode, and the Buck-type switching power converter performs load current sampling during the inductor current drop period. Different from FIG. 17, the sample-and-hold circuit samples and updates the sampling current at the midpoint of the inductor current falling period.

FIG. 19 is a timing diagram of the present invention when the switching power converter is a Boost-type or Buck-Boost switching power converter operating in the CCM mode, and the switching power converter samples the load current during the falling period of the inductor current; After the first inductor current drop period T1 starts, the mid-point current sampling value Vsen1 of the previous cycle is first output, and the input signal Vsen2 = Vsen1 of the low-pass filter. When the 0.5T0 is reached, the inductor current sampling value Vsen1 is updated while maintaining this current. The signal is output to the low-pass filter, and the low-pass filter input signal Vsen2 = Vsen1 until the end of the inductor current drop period ends. When the second inductor current drop period T2 arrives, the sampled current value at the time of the previous inductor current drop period T1 + 0.5T0 is output first, and when the inductor current drop period reaches 0.5T1, the current sample value Vsen1 is sampled and updated again. And keep until the end of the inductor current drop period. Repeatedly, I will not repeat them. Because Boost-type switching power converter circuits only output current to the output capacitor when the freewheeling tube is on, the load current is equal to the amount of current flowing through the freewheeling tube. Therefore, the output sampling current is output only when the freewheeling tube is turned on. The magnitude of I _load is the rectangular area with the same shadow line in one switching cycle, that is, the integral value of the load current divided by the time of the integration period.

FIG. 20 is a timing diagram of the signals of the present invention when the switching power converter is a Boost or Buck-Boost switching power converter operating in the CCM mode and sampling the load current during the inductor current rising period. After the inductor current rise period T1 begins in this cycle, the input Vsen2 of the low-pass filter is pulled down to 0, and the sampling current value Vsen1 is proportional to the magnitude of the inductor current; when the estimated midpoint 0.5T0 is reached, the sampling current value Vsen1 is maintained and Vsen1 is maintained. At this time, the input signal Vsen2 of the low-pass filter is still equal to 0; until the moment when the inductor current starts to drop, the switch is turned on to make the input signal Vsen2 = Vsen1 of the low-pass filter. Until the end of the switching cycle, this Vsen1 is the increase of the inductor current. The sampled value of the inductor current sampled in the period T1 at 0.5T0 of the period. When the inductor current rise period T2 of the next switching cycle arrives, the input signal Vsen2 of the low-pass filter is pulled down for the entire time period when the inductor current rises. When the inductor current rise period 0.5T1 is reached, the inductor current is sampled and the current is updated. The sampling value Vsen1 is held but not output to the low-pass filter. When the inductor current starts to decrease, the input signal Vsen2 = Vsen1 of the low-pass filter is made until the switching cycle ends. This Vsen1 is the inductor current rising period T2. Sampling value of the inductor current sampled at 0.5T1 during the period. Repeatedly, I will not repeat them.

FIG. 21 is a signal timing diagram of the present invention when the switching power converter is a Boost or Buck-Boost switching power converter operating in the DCM mode, and the load current is sampled at the falling edge of the inductor current. After the first inductor current drop period T1 starts, the current sampling value Vsen1 of the previous switching cycle is first output, and the current is sampled at the time T1 + 0.5T0, and the updated current sampling value Vsen1 is output to the low-pass filter and the low-pass filter. Input signal Vsen2 = Vsen1, while holding the current sampling value until the inductor current drops to 0, disconnect the sample-and-hold circuit and the low-pass filter from the electrical connection and pull the input signal Vsen2 of the low-pass filter low.

FIG. 22 is a signal timing diagram of the present invention when the switching power converter is a Boost or Buck-Boost switching power converter operating in the DCM mode, and the load current is sampled at the rising edge of the inductor current. After the inductor current rise period T1 of the current switching cycle starts, the sampling current is not output first; the current is sampled when the expected midpoint 0.5T0 is reached, and the rising edge midpoint current sample value Vsen1 is obtained and held, but the sample current signal is not output The input signal Vsen2 of the low-pass filter is still 0 during the rise of the inductor; until the moment when the inductor current starts to fall, the input of the low-pass filter Vsen2 = Vsen1, Vsen1 is 0.5T0 of the inductor current rise period T1 during this period. The value of the inductor current signal sampled at all times; the sample-and-hold circuit outputs the sampled current value Vsen1 of the low-pass filter until the inductor current drops to 0, the electrical connection between the sample-and-hold circuit and the low-pass filter is disconnected, and the The input signal Vsen2 is pulled low. A method for detecting a load current of a switching power converter includes the following steps: obtaining the total time T _A and T _{B of the} switching power converter during the A or B inductor current rising period or falling period, where B is equal to A + 1; The time at which the 0.5th _A of the inductor current rises or falls at the beginning of the B period, after which 0.5 T _A has passed, that is, the T _MB sample the load current at the first midpoint, and the sample current of the load current is maintained to the second midpoint by the sample-and-hold circuit Time T _MC ; the second mid-point time T _MC is a time after 0.5 T _B from the start time of the C-th inductor current rising period or falling period; at the first mid-point time T _MB to the second mid-point time During this period of time T _MC , the current-sampling signal using sample-and-hold is transformed into a load current signal according to different types of circuits and different operating modes. The load current sampling signal is smoothed by a low-pass filter to obtain the load current signal of the switching power converter. No matter what type of circuit, the load current sample value is not output when the inductor current is zero.

Through clever timing control, the total time of the rising or falling period of the inductor current in the elapsed switching signal period is used to simulate the midpoint of the rising or falling period of the inductor current in the current cycle, and it is skillfully performed at that moment Sampling and holding make full use of the linear characteristics of the inductor current during the on-time of the switch tube or the on-time of the freewheeling tube, simplifying the load detection circuit; at the same time, the sampling time is close to or approximates the on-time or freewheeling of the switch tube At the midpoint of the tube turn-on period, the sampling current is usually within the optimal response interval of the op amp, so the overall load current detection accuracy is also improved, which not only avoids complex circuit design, but also increases the load current. The detection accuracy reduces the complexity and difficulty of the circuit; the circuit structure is simple and clever, and the applicability is strong. Buck, Boost and Buck-Boost DCDC switching power converters can be used; whether it is a switching tube or a freewheeling tube, it can be used This method restores the size of the load current and has strong flexibility; it is also commonly used for power tube proportional current detection and series connection Resistive current detection circuit, synchronous or non-synchronous rectification circuit; in integrated circuit applications, easy to deploy the application, save chip area.

The above is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the description of the invention and the contents of the drawings, or directly or indirectly used in other related technical fields All are included in the patent protection scope of the present invention.

Claims

A method for detecting load current of an inductive switching power converter includes the following steps:

Obtain the time of the rising or falling period of the inductor current of the switching power converter in the Ath switching cycle as T A ; record the time of the rising or falling period of the inductor current of the switching power converter in the Bth switching cycle as T B , B is equal to A + N;

Get the inductor current in the first rising period switching cycles B or falling period of the first middle time T MB; a midpoint of the first time starting from the time T MB B of the switching cycle the inductor current rising period or the falling period The moment after 0.5T A ;

Obtain the second mid-point time T MC of the rising or falling period of the inductor current in the C-th switching cycle, where C is equal to B + M; the second mid-point time T MC is the rising period of the inductor current in the C-th switching cycle Or the time after 0.5T B from the beginning of the falling period; where A, B, C, N, and M are all natural numbers greater than or equal to 1;

The load current is sampled at the time T MB at the first midpoint, and the sampled value of the load current is held by the sample and hold circuit to the time T MC at the second mid point; the time between the first mid point T MB and the second mid point T MC For a period of time, if the switching power converter is a Buck-type switching power converter, the load current sampling signal is output during the time when the inductor current rises and falls; if the switching power converter is a Boost or Buck-Boost switching power converter, Then, the load current sampling signal is output during the period when the inductor current decreases.
The method for detecting a load current of an inductive switching power converter according to claim 1, wherein:

The load current sampling signal output by the sample-and-hold circuit is filtered by a low-pass filter as the load current signal of the switching power converter;

Or the load current sampling signal output by the sample-and-hold circuit is used as the load current signal of the switching power converter after being integrated by the integration circuit.
The method for detecting a load current of an inductive switching power converter according to claim 1, wherein:

When the switching power converter is a Buck-type switching power converter, and the Buck-type switching power converter works in CCM mode;

The sampling time of the load current, that is, the first midpoint time T MB, is the time after 0.5T A starts at the beginning of the rising or falling period of the inductor current of the Bth switching cycle, where B = A + 1, that is, N = 1.

The update time of the load current, that is, the second mid-point time T MC is the time after 0.5 T B starts at the beginning of the rising or falling period of the inductor current of the C-th switching cycle, where C = B + 1, that is, M = 1.
The method for detecting a load current of an inductive switching power converter according to claim 1, wherein:

When the switching power converter is a Buck-type switching power converter, and the Buck-type switching power converter works in the DCM mode;

The sampling time of the load current, that is, the first midpoint time T MB, is the time after 0.5T A starts at the beginning of the rising or falling period of the inductor current of the Bth switching cycle, where B = A + 1, that is, N = 1.

The update time of the load current, that is, the second mid-point time T MC is the time after 0.5T B starts at the beginning of the rising or falling period of the inductor current of the C-th switching cycle, where C = B + 1, that is, M = 1;

When the inductor current is zero, the load current output is turned off through the switching circuit, that is, during the time period when the inductor current is zero, the load current value held by the sample is not output to the outside.
The method for detecting a load current of an inductive switching power converter according to claim 1, wherein:

When the switching power converter is a Boost switching power converter or a Buck-Boost switching power converter, and the switching power converter works in the CCM mode;

The sampling time of the load current, that is, the first midpoint time T MB, is the time after 0.5T A begins at the beginning of the rising or falling period of the inductor current of the Bth switching cycle, where B = A + 1, that is, N = 1.

The update time of the load current, that is, the second mid-point time T MC is the time after 0.5T B starts at the beginning of the rising or falling period of the inductor current of the C-th switching cycle, where C = B + 1, that is, M = 1;

During the period when the inductor current rises, the load current output is turned off by the switching circuit, that is, during the time period when the inductor current rises, the sampled and held load current value is not output to the outside.
The method for detecting a load current of an inductive switching power converter according to claim 1, wherein:

When the switching power converter is a Boost switching power converter or a Buck-Boost switching power converter, and the switching power converter works in the DCM mode;

The sampling time of the load current, that is, the first midpoint time T MB, is the time after 0.5T A begins at the beginning of the rising or falling period of the inductor current of the Bth switching cycle, where B = A + 1, that is, N = 1.

The update time of the load current, that is, the second mid-point time T MC is the time after 0.5T B starts at the beginning of the rising or falling period of the inductor current of the C-th switching cycle, where C = B + 1, that is, M = 1;

During the period when the inductor current rises, the load current output is turned off through the switching circuit, and the sampled and held load current value is not output to the outside;

And when the inductor current is zero, the load current output is turned off through the switch circuit, and the sampled and held load current value is not output to the outside.
The method for detecting a load current of an inductive switching power converter according to claim 1, wherein:

The method includes the step of using the switching signal of the switching power converter to obtain the midpoint moment of the falling or rising period of the inductor current in the switching signal period. The step includes the following sub-steps:

Steps of generating the first midpoint detection control signal (Φ1) and the second midpoint detection control signal (Φ1B) according to the switching signal of the switching power converter: the switching signal is divided into an odd period and an even period, and the first midpoint detection control The signal (Φ1) is high only when the switching signal in the odd-numbered switching cycle is high, and the remaining time is low; the second midpoint detection control signal (Φ1B) is only in the even-numbered switching cycle. When the switching signal is high, it is high, and the rest of the time are low; that is, the first midpoint detection control signal (Φ1) or the upper second midpoint detection control signal (Φ1B) is equal to the switching signal;

Set up a midpoint detection operational amplifier. Connect the non-inverting input terminal and the inverting input terminal of the midpoint detection operational amplifier to the first and second midpoint detection capacitors, the first and second midpoint detection capacitors, respectively. The capacitance of the capacitor is the same, and the other terminal of the two capacitors is grounded;

The first midpoint detection control signal (Φ1) and the second midpoint detection control signal (Φ1B) are used to control the charging and discharging processes of the first midpoint detection capacitor and the second midpoint detection capacitor respectively; the midpoint detection operational amplifier is based on the in-phase input The voltage input from the terminal and the inverting input terminal outputs a midpoint time signal, and the midpoint time signal includes first midpoint time T MB and second midpoint time T MC information.
A load current detection circuit for an inductive switching power converter is characterized by:

Including the midpoint detection circuit (32) of the inductor current rising period or falling period and the sample-and-hold circuit (34) for sampling and holding of the load current;

The midpoint detection circuit (32) for the rising period or falling period of the inductor current is used to obtain the rising period or falling period of the inductor current during the Ath switching cycle, which is denoted as T A , and is also used to obtain the period during the Bth switching cycle. The rising or falling period of the inductor current is recorded as T B , and B is equal to A + N;

The midpoint detection circuit (32) of the rising period or falling period of the inductor current is further configured to obtain a first midpoint time T MB in the Bth switching cycle and a second midpoint time T MC in the Cth switching cycle. The first midpoint time T MB is the time after 0.5T A from the start time of the rising or falling period of the inductor current in the Bth switching cycle; the second midpoint time T MC is the Cth switch The time after 0.5T B has passed from the beginning of the rising or falling period of the inductor current in the cycle; where C is equal to B + M; A, B, C, N, and M are all natural numbers greater than or equal to 1;

The midpoint detection circuit (32) of the inductor current rising period or falling period is electrically connected to the sample-and-hold circuit (34), and the inductor current rising period or falling period midpoint detection circuit (32) outputs a midpoint instant signal to A sample-and-hold circuit (34); the mid-point time signal includes the first mid-point time T MB and the second mid-point time T MC information; the sample-and-hold circuit (34) samples the load current at the first mid-point time T MB , and Keep the sampled load current until the update time, that is, the second midpoint time T MC ; during the period from the first mid point time T MB to the second mid point time T MC ,

If the switching power converter is a Buck switching power converter, the load current sampling signal is output during the inductor current rising and falling time periods; if the switching power converter is a Boost or Buck-Boost switching power converter, the The load current sampling signal is output during the period when the current decreases.
The load current detection circuit of an inductive switching power converter according to claim 8, characterized in that:

Also includes a low-pass filter circuit (35);

The low-pass filter circuit (35) and the sample-and-hold circuit (34) are electrically connected;

The load current sampling signal input from the sample-and-hold circuit (34) to the low-pass filter circuit (35) is outputted after being low-pass filtered by the low-pass filter circuit (35).
The load current detection circuit of an inductive switching power converter according to claim 8, characterized in that:

The midpoint detection circuit (32) of the inductor current rising period or falling period includes a first midpoint detection switch, a second midpoint detection switch, a third midpoint detection switch, a fourth midpoint detection switch, and a first midpoint detection. Capacitor, second midpoint detection capacitor, midpoint detection operational amplifier, two current sources of the same size, namely a first current source and a second current source, where the first current source is used to inject current and the second current source is used to output Current

The output terminal of the first current source is electrically connected through the first midpoint detection switch and the inverting input terminal of the midpoint detection operational amplifier. The output terminal of the first current source is also connected through the second midpoint detection switch and the midpoint detection operational amplifier. The non-inverting input terminal is electrically connected; the input terminal of the second current source is electrically connected through the third midpoint detection switch and the inverting input terminal of the midpoint detection operational amplifier, and the input terminal of the second current source is also connected through the fourth midpoint detection switch and The non-inverting input terminals of the midpoint detection operational amplifier are electrically connected;

The non-inverting input terminal of the midpoint detection operational amplifier is electrically connected to one end of the second midpoint detection capacitor, and the other end of the second midpoint detection capacitor is grounded; the inverting input terminal of the midpoint detection operational amplifier and the first midpoint detection capacitor One end is electrically connected, and the other end of the first midpoint detection capacitor is grounded; the capacitance values of the first midpoint detection capacitor and the second midpoint detection capacitor are the same;

The first midpoint detection switch and the fourth midpoint detection switch are controlled by the first midpoint detection control signal (Φ1); when the first midpoint detection control signal is high, the first midpoint detection switch and the fourth midpoint The detection switches are both closed, so that both ends of the switch are turned on; when the first midpoint detection control signal is at a low level, both the first midpoint detection switch and the fourth midpoint detection switch are turned on, so that both ends of the switch are disconnected;

The second midpoint detection switch and the third midpoint detection switch are controlled by the second midpoint detection control signal (Φ1B); when the second midpoint detection control signal is high, the second midpoint detection switch and the third midpoint The detection switches are both closed, so that both ends of the switch are turned on; when the second midpoint detection control signal is at a low level, both the second midpoint detection switch and the third midpoint detection switch are opened, so that both ends of the switch are disconnected;

The first midpoint detection control signal (Φ1) or the upper second midpoint detection control signal (Φ1B) is equal to the switching signal of the inductive switching power converter; when the switching signal is in an odd number of cycles, the first midpoint detection control signal The high level of (Φ1) is the same as the high level of the switching signal; when the switching signal is in an even number of cycles, the high level of the second midpoint detection control signal (Φ1B) is the same as the high level of the switching signal;

An output terminal of the midpoint detection operational amplifier outputs a first midpoint time signal, and the first midpoint time signal is transmitted to the sample and hold circuit (34) to control the sampling time of the sampling circuit.
The load current detection circuit of an inductive switching power converter according to claim 10, wherein:

The midpoint detection circuit (32) of the inductor current rising period or falling period further includes a D flip-flop and an exclusive OR gate;

The clock signal of the D flip-flop is an externally-input switching signal for inductive switching power converter control; a first input terminal (D) of the D flip-flop and a second output terminal of the D flip-flop ( Qn) electrical connection, the first output terminal (Q) of the D flip-flop outputs a signal to one input terminal of the exclusive OR gate;

The output terminal of the midpoint detection operational amplifier outputs a first midpoint time signal to another input terminal of the XOR gate, and the output terminal of the XOR gate outputs a second midpoint time signal, which is transmitted to the second midpoint time signal. The sample-and-hold circuit (34) controls the sampling timing of the sampling circuit.
The load current detection circuit of an inductive switching power converter according to claim 11, wherein:

A first output terminal (Q) of the D flip-flop outputs a signal to a first AND gate, performs an AND operation with a switching signal controlled by an inductive switching power converter, and outputs a first midpoint detection control signal (Φ1);

The second output terminal (Qn) of the D flip-flop outputs a signal to a second AND gate, performs an AND operation with a switching signal controlled by the inductive switching power converter, and outputs a second midpoint detection control signal (Φ1B).
The load current detection circuit of an inductive switching power converter according to claim 11, wherein:

The sample and hold circuit (34) includes a second sample and hold switch, a second sample and hold capacitor, a third sample and hold switch, a third sample and hold capacitor, and a sample and hold operational amplifier;

One end of the second sample-and-hold switch is used to connect to an external inductor current detection circuit to obtain a load current sampling signal. The other end of the second sample-and-hold switch is electrically connected to one end of the second sample-and-hold capacitor and one end of the third sample-and-hold switch simultaneously. The other end of the second sample-and-hold capacitor is grounded; the other end of the third sample-and-hold switch is simultaneously electrically connected to the non-inverting input terminal of the sample-and-hold operational amplifier and one end of the third sample-and-hold capacitor, and the other end of the third sample-and-hold capacitor is grounded; The inverting input terminal of the sample-and-hold operational amplifier is electrically connected to the output terminal of the sample-and-hold operational amplifier;

The second sample-and-hold switch is controlled by the non-signal of the signal at the second mid-point time. When the non-signal of the signal at the second mid-point time is high, the second sample-and-hold switch is closed to make both ends of the switch on. When the non-signal of the signal at the moment is low, the second sample-and-hold switch is opened to disconnect the two ends of the switch;

The third sample-and-hold switch is controlled by the second mid-point signal. When the second mid-point signal is high, the third sample-and-hold switch is closed to make both ends of the switch on. When the second mid-point signal is low, Usually, the third sample-and-hold switch is turned on to disconnect the two ends of the switch.
The load current detection circuit for an inductive switching power converter according to claim 9, wherein:

It also includes an inductor current zero-crossing detection circuit (31) for obtaining a low-pass filtered switch control signal.
The load current detection circuit of an inductive switching power converter according to claim 14, wherein:

The low-pass filter circuit (35) and the sample-and-hold circuit (34) are electrically connected through a low-pass filter switch; the low-pass filter switch is controlled by the low-pass filter output from the inductor current zero-crossing detection circuit (31). Switch control signal;

When the inductor current is zero, the low-pass filter switch control signal controls the low-pass filter switch to open, so that both ends of the switch are disconnected, so that the low-pass filter circuit (35) and the sample-and-hold circuit (34) are disconnected. Open the connection, and ground the input of the low-pass filter (35); when the inductor current is non-zero, the low-pass filter switch control signal controls the low-pass filter switch to be closed so that both ends of the switch are turned on, so that the low The pass filter circuit (35) and the sample-and-hold circuit (34) are electrically connected.
The load current detection circuit of an inductive switching power converter according to claim 15, wherein:

It also includes a low-pass filter input pull-down MOS tube, which is used to pull down the input of the low-pass filter (35) after disconnecting between the low-pass filter circuit (35) and the sample-and-hold circuit (34), so that all the The input of the low-pass filter (35) is zero.
The load current detection circuit of an inductive switching power converter according to claim 16, wherein:

The low-pass filter circuit (35) includes one or more low-pass filters.
The load current detection circuit of an inductive switching power converter according to claim 17, wherein:

When the low-pass filter circuit (35) is a first-level RC low-pass filter, the first-level RC low-pass filter includes a low-pass filter resistor and a low-pass filter capacitor;

One end of the low-pass filter resistor is electrically connected to one end of the low-pass filter switch, and one end of the low-pass filter resistor is electrically connected to the source of the low-pass filter input pull-down MOS tube, and the low-pass filter input pull-down MOS tube is electrically connected. The gate of the MOSFET is connected to the non-signal of the control signal of the low-pass filter switch, and the drain of the MOS tube is pulled down to ground by the low-pass filter input;

The other end of the low-pass filter resistor is used as an output terminal of the low-pass filter circuit (35), and the other end of the low-pass filter resistor is also electrically connected to one end of the low-pass filter capacitor. Ground at one end.
The load current detection circuit of a switching power converter according to claim 8, wherein:

It also includes an inductor current detection circuit (30) for sampling and obtaining the load current;

The inductor current detection circuit (30) and the sample-and-hold circuit (34) are electrically connected;

The inductor current detection circuit (30) outputs a load current signal to the sample-and-hold circuit (34).
An inductive switching power converter circuit is characterized by:

The load current detection circuit for a switching power converter according to any one of claims 8 to 19 is included.
The inductive switching power converter circuit according to claim 20, wherein:

It also includes a logic control circuit; the logic control circuit is used to generate a basic switching signal for timing control of an inductive switching power converter;

The logic control circuit generates a first control signal GP and a second control signal GN for controlling two power switching tubes according to a basic switching signal; when the first control signal GP is at a high level, one of the power tubes is turned on; the first control When the signal GP is at a low level, another power tube is turned on; the first control signal GP and the second control signal GN are synchronously converted signals of the base switching signal; the inductor current rising time period and the inductor current falling time period are synchronized with the first control The signal GP and the second control signal GN; thus, the inductor current rising time period and the inductor current falling time period and the basic switching signal are also synchronized.