Method, circuit and system for detecting load current of switching power supply

Abstract

The invention provides a method, a circuit and a system for detecting load current of a switching power supply, and belongs to the technical field of electronics. In the scheme provided by the invention, the sampling sub-circuit in the detection circuit can sample the switching signal of the DC / DC controller in the switching power supply, and the detection sub-circuit can determine the load current of the switching power supply based on the duty ratio of the switching signal and the stored corresponding relation between the calibration duty ratio and the calibration current. The detection circuit can realize real-time detection of the load current of the switching power supply. Moreover, the detection circuit detects the size of the load current based on the duty ratio of the switching signal, and the load current output by the switching power supply does not need to be directly detected, so that chips such as an operational amplifier do not need to be additionally arranged, the structure of the detection circuit is effectively simplified, and the cost of the detection circuit is reduced.

Description

Technical Field

[0001] The present application relates to the field of electronic technologies, and particularly to a method, a circuit and a system for detecting the load current of a switching power supply. Background Art

[0002] A switching power supply, which can also be referred to as a direct current / direct current (DC / DC) converter, is a device used to convert a fixed input voltage into a supply voltage required by a load. A switching power supply generally includes a DC / DC controller, as well as energy storage components such as inductors and capacitors. The DC / DC controller integrates a switching transistor and a drive control circuit. The drive control circuit can output a switching signal to the switching transistor to drive the switching transistor to perform high-frequency switching actions. During the process of the switching transistor performing high-frequency switching actions, the energy storage components can continuously store and release energy, thereby realizing the power supply to the load.

[0003] Since the load current (also referred to as the output current) of a switching power supply can reflect the working states of the load and the switching power supply, detecting the load current of a switching power supply plays an important role in improving product performance. However, in related art, the current detection scheme generally integrates a mirror current source in the DC / DC controller, and the mirror current source can sample the passing current of the switching transistor. The drive control circuit in the DC / DC controller can perform overcurrent detection and protection based on the magnitude of the passing current.

[0004] However, the scheme in related art can only achieve overcurrent protection for the switching power supply itself and cannot achieve real-time detection of the load current. Summary of the Invention

[0005] The present application provides a method, a circuit and a system for detecting the load current of a switching power supply, which can solve the technical problem that the current detection scheme in related art can only achieve overcurrent protection for the switching power supply itself and cannot achieve real-time detection of the load current.

[0006] In a first aspect, a detection circuit for the load current of a switching power supply is provided. The switching power supply includes a direct current / direct current (DC / DC) controller. The detection circuit includes a sampling sub-circuit and a detection sub-circuit. The sampling sub-circuit is respectively connected to the DC / DC controller and the detection sub-circuit, and is used for sampling the switching signal in the DC / DC controller and transmitting it to the detection sub-circuit. The detection sub-circuit is used for detecting the duty cycle of the switching signal, and determining the load current of the switching power supply based on the duty cycle of the switching signal and the corresponding relationship between the calibrated duty cycle and the calibrated current stored in the detection sub-circuit.

[0007] The detection circuit provided by this application can achieve real-time detection of the load current of the switching power supply. Moreover, since the detection circuit detects the magnitude of the load current based on the duty cycle of the switching signal without directly detecting the load current output by the switching power supply, there is no need to additionally set chips such as operational amplifiers, thereby effectively simplifying the structure of the detection circuit and reducing the cost of the detection circuit.

[0008] Optionally, the sampling sub-circuit may include: a low-pass filtering sub-circuit; the low-pass filtering sub-circuit is used to perform low-pass filtering on the sampled switching signal and transmit the switched signal after low-pass filtering to the detection sub-circuit.

[0009] Since the switching signal sampled by the sampling sub-circuit may be a strong driving signal, the switching signal can be filtered by the low-pass filtering sub-circuit to avoid electromagnetic compatibility (EMC) problems caused by excessive energy in the high-frequency part of the switching signal.

[0010] Optionally, the low-pass filtering sub-circuit may be a resistor filtering circuit or a resistor-capacitor (RC) filtering circuit. Among them, the resistor filtering circuit may include one resistor or may include multiple series resistors. The above resistor filtering circuit or RC filtering circuit has a relatively simple structure, which can avoid increasing the cost and structural complexity of the detection circuit.

[0011] Optionally, the sampling sub-circuit may further include a voltage limiting sub-circuit; the voltage limiting sub-circuit can be used to limit the voltage of the switched signal after low-pass filtering and transmit the switched signal after low-pass filtering and voltage limiting to the detection sub-circuit. By limiting the voltage of the switching signal through the voltage limiting sub-circuit, it can be ensured that the switched signal after voltage limiting can meet the requirements of the working voltage of the detection sub-circuit, thereby ensuring the normal operation of the detection sub-circuit.

[0012] Optionally, the sampling sub-circuit may include a voltage limiting sub-circuit; the voltage limiting sub-circuit can be used to limit the voltage of the sampled switching signal and transmit the switched signal after voltage limiting to the detection sub-circuit. That is, in this implementation, the sampling sub-circuit may not need to include a low-pass filtering sub-circuit, and the voltage limiting sub-circuit can directly limit the voltage of the sampled switching signal.

[0013] Optionally, the voltage limiting sub-circuit may be a resistor voltage dividing circuit, a diode clamping circuit or a zener diode voltage limiting circuit. The above voltage limiting sub-circuits all have relatively simple structures, and can minimize the cost and structural complexity of the detection circuit on the premise of ensuring that the switching signal meets the input requirements of the detection sub-circuit.

[0014] Optionally, the detection sub-circuit may include a controller, which may be a digital control device such as a field programmable gate array (FPGA), a complex programmable logic device (CPLD), a micro-controller unit (MCU), or a central processing unit (CPU). The controller is configured to detect the duration of the first level and the duration of the second level in the switching signal, and determine the duty cycle of the switching signal based on the duration of the first level and the duration of the second level. Wherein, the first level may be a high level relative to the second level, that is, the controller can determine the duty cycle of the switching signal by detecting the duration of the high level and the duration of the low level of the switching signal within a certain period of time.

[0015] Optionally, the sampling sub-circuit may further include an integration sub-circuit, and the detection sub-circuit includes an analog to digital converter (ADC) and a controller. The integration sub-circuit is configured to convert the switched signal that has passed through low-pass filtering into a voltage signal and transmit it to the ADC. The ADC is configured to perform analog-to-digital conversion on the voltage signal and then transmit it to the controller, and the voltage signal after analog-to-digital conversion can be used to represent the duty cycle of the switching signal. The controller may be configured to determine the load current of the switching power supply based on the duty cycle of the switching signal represented by the voltage signal after analog-to-digital conversion and the corresponding relationship between the calibrated duty cycle and the calibrated current stored in the controller.

[0016] It can be understood that in this implementation manner, the calibrated duty cycle stored in the controller may also be represented by the voltage signal (i.e., voltage value) after analog-to-digital conversion. And this implementation manner can be applied to a scenario where the hardware product system already has an ADC redundant channel, that is, the ADC in the detection sub-circuit can reuse the existing ADC in the switching power supply.

[0017] Optionally, the sampling sub - circuit may include an integration sub - circuit, and the detection sub - circuit includes an ADC and a controller. The integration sub - circuit is used to convert the sampled switching signal into a voltage signal and transmit it to the ADC. The ADC is used to perform analog - to - digital conversion on the voltage signal and then transmit it to the controller. The voltage signal after analog - to - digital conversion can be used to characterize the duty cycle of the switching signal. The controller can be used to determine the load current of the switching power supply based on the duty cycle of the switching signal characterized by the voltage signal after analog - to - digital conversion and the corresponding relationship between the calibrated duty cycle and the calibrated current stored in the controller. It can be understood that in this implementation, the sampling sub - circuit may not need to include a low - pass filtering sub - circuit, and the integration sub - circuit can directly convert the sampled switching signal into a voltage signal.

[0018] Optionally, the integration sub - circuit can be an RC integration circuit or an LC integration circuit. Here, L refers to an inductor. The structures of both the RC integration circuit and the LC integration circuit are relatively simple, which can avoid increasing the cost and structural complexity of the detection circuit.

[0019] Optionally, the DC / DC controller includes a switching transistor. The sampling sub - circuit can be connected to the gate of the switching transistor, or the sampling sub - circuit can be connected to the target electrode of the switching transistor, where the target electrode is the electrode of the switching transistor used to connect the inductor in the switching power supply.

[0020] It can be understood that if the DC / DC controller in the switching power supply leads out the gate of the switching transistor, the sampling sub - circuit can be connected to the gate of the switching transistor to ensure accurate sampling of the switching signal applied to the switching transistor. If the DC / DC controller does not lead out the gate of the switching transistor, the sampling sub - circuit can be connected to the target electrode. Among them, since the target electrode needs to be connected to the inductor (also called the power inductor) in the switching power supply, the DC / DC controller usually leads out the target electrode.

[0021] In a second aspect, a method for detecting the load current of a switching power supply is provided, which can be applied to the detection sub - circuit in the load - current detection circuit provided in the first aspect as described above. The method includes: detecting the measured duty cycle of the switching signal in the DC / DC controller of the switching power supply, and determining the load current of the switching power supply based on the measured duty cycle of the switching signal and the corresponding relationship between the stored calibrated duty cycle and the calibrated current.

[0022] Optionally, the corresponding relationship can be a functional relationship between the calibrated duty cycle and the calibrated current. Moreover, the detection sub - circuit can store the coefficients of the functional relationship (which can also be called polynomial coefficients) to implement the storage of the corresponding relationship.

[0023] Optionally, the method may further include: when the switching power supply is connected to the first load, detecting a first calibrated duty cycle of the switching signal in the DC / DC controller, and obtaining a first calibrated current flowing through the first load; when the switching power supply is connected to the second load, detecting a second calibrated duty cycle of the switching signal in the DC / DC controller, and obtaining a second calibrated current flowing through the second load, where the resistance value of the second load is different from that of the first load. Then, based on the first calibrated duty cycle, the first calibrated current, the second calibrated duty cycle, and the second calibrated current, determine the corresponding relationship between the calibrated duty cycle and the calibrated current.

[0024] In the solution provided by this application, before the switching power supply leaves the factory, the duty cycle of the switching signal when the switching power supply is connected to different loads can be detected through a detection circuit, and the detected duty cycle (i.e., the calibrated duty cycle) can be stored corresponding to the actually measured or calculated load current (i.e., the calibrated current). Thus, the accuracy and reliability of detecting the load current of the switching power supply based on this corresponding relationship can be ensured to be relatively high.

[0025] Optionally, the process of determining the corresponding relationship between the calibrated duty cycle and the calibrated current based on the first calibrated duty cycle, the first calibrated current, the second calibrated duty cycle, and the second calibrated current may include: performing curve fitting on the first calibrated duty cycle, the first calibrated current, the second calibrated duty cycle, and the second calibrated current to obtain the corresponding relationship between the calibrated duty cycle and the calibrated current.

[0026] Among them, the curve fitting may be linear fitting. Using the corresponding relationship obtained by curve fitting to detect the load current of the switching power supply can ensure a relatively high detection accuracy.

[0027] In a third aspect, a detection system for the load current of a switching power supply is provided. The detection system includes: a switching power supply, and a detection circuit for the load current of the switching power supply provided in the first aspect as described above. Among them, the switching power supply may be a boost-type switching power supply or a buck-type switching power supply.

[0028] In summary, this application provides a method, a circuit, and a system for detecting the load current of a switching power supply. In the solution provided by this application, the sampling sub-circuit in the detection circuit can sample the switching signal of the DC / DC controller in the switching power supply, and the detection sub-circuit can determine the load current of the switching power supply based on the duty cycle of the switching signal and the stored corresponding relationship between the calibrated duty cycle and the calibrated current. The detection circuit can realize real-time detection of the load current of the switching power supply. Moreover, since the detection circuit detects the magnitude of the load current based on the duty cycle of the switching signal without directly detecting the load current output by the switching power supply, there is no need to additionally set chips such as operational amplifiers, thereby effectively simplifying the structure of the detection circuit. Description of the Drawings

[0029] Figure 1 It is a schematic structural diagram of a switching power supply provided by an embodiment of the present application;

[0030] Figure 2 It is a schematic structural diagram of another switching power supply provided by an embodiment of the present application;

[0031] Figure 3 It is a schematic structural diagram of a detection circuit for the load current of a switching power supply provided by an embodiment of the present application;

[0032] Figure 4 It is a schematic structural diagram of a detection circuit for the load current of another switching power supply provided by an embodiment of the present application;

[0033] Figure 5 It is a schematic structural diagram of a detection circuit for the load current of yet another switching power supply provided by an embodiment of the present application;

[0034] Figure 6 It is a schematic structural diagram of a detection circuit for the load current of still another switching power supply provided by an embodiment of the present application;

[0035] Figure 7 It is a schematic flow diagram of a method for detecting the load current of a switching power supply provided by an embodiment of the present application. Specific embodiments

[0036] The following will introduce in detail the method, circuit, and system for detecting the load current of the switching power supply provided by the embodiments of the present application in conjunction with the accompanying drawings. First, the key terms related to the embodiments of the present application will be introduced.

[0037] Detecting the load current of a switching power supply plays an important role in improving the design for the X stage of hardware products (design for X, DFX). For example, in products such as satellite payloads in the aerospace application field, semiconductor device loads in the outer space of the universe are prone to single event effects (SEE) and total ionizing dose (TID) effects due to high-energy particle irradiation. These two effects are strongly related to the load current of the device. In addition, if a single event latch-up (SEL) effect, also known as a latching effect, occurs, it will cause a sharp increase in the load current. If the protection is not timely, it may lead to device burnout and payload failure. It can be seen that it is crucial to detect the load current of the switching power supply in real time and take protection measures in a timely manner.

[0038] To detect the load current of a switching power supply, in an alternative solution, a sampling resistor can be connected in series in the load circuit of the switching power supply, and the voltage across the sampling resistor is amplified by an operational amplifier and then sent to an ADC for analog-to-digital conversion. The voltage after the analog-to-digital conversion can reflect the magnitude of the load current. However, this solution requires additional chips such as operational amplifiers and ADCs, which will increase the complexity of the detection circuit and the material cost. Moreover, in the aerospace application field, since the operational amplifier is a semiconductor device, it also has SEE and TID effects, thus affecting the credibility and reliability of the current detection result. If space-grade operational amplifiers are added to the detection circuit for this reason, the cost of the detection circuit will increase significantly, which is not suitable for use in the commercial aerospace field.

[0039] In another alternative solution, the passing current of a metal-oxide-semiconductor field-effect transistor (MOSFET) in the switching power supply can be sampled through a mirror current source. Then, it is amplified by an error amplifier, compared with a threshold voltage by a comparator, and the comparison result is output to a control unit (such as the drive control circuit in a DC / DC controller), and then the control unit makes a judgment and performs protection. The current detection devices (such as mirror current sources, error amplifiers, and comparators, etc.) in this solution are generally integrated in the DC / DC controller of the switching power supply. Moreover, this solution is generally used to implement overcurrent protection for the switching power supply itself, and it cannot flexibly adjust the current protection threshold according to the requirements of the load circuit, nor can it be used for real-time detection of the load current. It can be seen that the function of this solution is relatively single, and the application flexibility is poor.

[0040] The embodiment of the present application provides a detection circuit for the load current of a switching power supply. This detection circuit does not require additional chips such as operational amplifiers, and its circuit structure is relatively simple, with high application flexibility. First, the switching power supply involved in the embodiment of the present application is introduced. This switching power supply can also be called a DC / DC converter, and it generally includes the following two types of circuits: such as Figure 1 the buck type circuit shown, and such as Figure 2 the boost type circuit shown. Referring to Figure 1 and Figure 2 it can be seen that the switching power supply can include a DC / DC controller, and energy storage components such as an inductor L0 and a capacitor C0 connected to the DC / DC controller.

[0041] The DC / DC controller integrates switching transistors (such as Figure 1 M0 and M1 in Figure 2M0) in it, and a drive control circuit for driving the switching transistor. The drive control circuit can output a switching signal to the gate of the switching transistor, and the switching signal can be a pulse width modulation (PWM) signal, which can drive the switching transistor to perform high-frequency switching actions. During the process of the switching transistor performing high-frequency switching actions, energy storage elements such as the inductor L0 and / or the capacitor C0 can continuously store and release energy, so as to realize the power supply for the load R0. Among them, the switching transistor integrated in the DC / DC controller can be a metal-oxide-semiconductor field-effect transistor (MOSFET), for example, it can be an N-type MOSFET, that is, NMOS.

[0042] Figure 3 is a schematic structural diagram of a detection circuit for the load current of a switching power supply provided by an embodiment of the present application. As Figure 3 shown, the detection circuit includes: a sampling sub-circuit 10 and a detection sub-circuit 20.

[0043] Among them, the sampling sub-circuit 10 is respectively connected to the DC / DC controller 01 in the switching power supply 00 and the detection sub-circuit 20. The sampling sub-circuit 10 is used to sample the switching signal in the DC / DC controller 01 and transmit the sampled switching signal to the detection sub-circuit 20.

[0044] The detection sub-circuit 20 is used to detect the duty cycle of the received switching signal, and based on the duty cycle of the switching signal and the corresponding relationship between the calibrated duty cycle and the calibrated current stored in the detection sub-circuit 20, determine the load current of the switching power supply 00.

[0045] It can be understood that if the loss of the switching power supply 00 itself is ignored, then combining Figure 1 and Figure 2 , the input voltage U in , input current I in , output voltage U out , and output current (i.e., load current) I out of the switching power supply 00 can satisfy:

[0046] U in ×I in ×t in =U out ×I out ×t out Formula (1);

[0047] Among them, t in can refer to the input current I inDuration, t out may refer to the duration of the load current I out The duration. The duration t in After normalization, it can be equivalent to the duty cycle D of the switching signal in This duration t out After normalization, it can be equivalent to the duty cycle D of the output voltage of the switching power supply 00 out Since the switching power supply 00 has a DC output, D out = 1. Based on this, the above formula (1) can be converted to:

[0048] U in × I in × D in = U out × I out Formula (2);

[0049] Based on formula (2), it can be deduced that the load current I out satisfies:

[0050] I out = (U in × I in / U out ) × D in Formula (3).

[0051] It can also be understood that according to the application scenario of the switching power supply 00, after the circuit parameters of the switching power supply 00 are fixed, the input voltage U in and the output voltage U out are both constants. The input current I in is related to the circuit parasitic parameters, and the input current I in is also a constant at the fixed operating point of the switching power supply 00 (i.e., the fixed input voltage U in and the output voltage U out ). It can be seen that within a certain operating range, the load current I out is proportional to the duty cycle D of the switching signal in , so the magnitude of the load current I in can be reflected by the duty cycle D of this switching signal out .

[0052] In the embodiment of the present application, the detection sub-circuit 20 prestores the corresponding relationship between the calibrated duty cycle and the calibrated current. This corresponding relationship can be obtained by pre-calibrating the duty cycle of the switching signal and the load current in the switching power supply 00, for example, it can be obtained before the switching power supply 00 leaves the factory. During the actual operation of the switching power supply 00, the detection sub-circuit 20 can detect the duty cycle of the switching signal sampled by the sampling sub-circuit 10, and based on the detected duty cycle and the prestored corresponding relationship, determine the load current I of the switching power supply 00 out 。

[0053] Based on the above analysis, it can be seen that the detection circuit provided by the embodiment of the present application samples the switching signal and determines the load current through the duty cycle of the switching signal. Since there is no need to directly detect the load current output by the switching power supply, there is no need to additionally set chips such as operational amplifiers. Only a simple sampling sub-circuit and a detection sub-circuit are required to realize the real-time detection of the load current. The structure of this detection circuit is relatively simple, the cost is low, and since it does not need to be integrated in the DC / DC controller, the application flexibility is relatively high.

[0054] Reference Figures 1 to 3 shows that the DC / DC controller 01 includes switching transistors, such as Figure 1 and Figure 3 the switching transistors M0 and M1 in, or Figure 2 the switching transistor M0 in. The drive control circuit in the DC / DC controller 01 can apply a switching signal to the gate of the switching transistor to drive the switching transistor to perform high-frequency switching actions.

[0055] In the first possible implementation manner, the sampling sub-circuit 10 can be directly connected to the gate of the switching transistor, that is, the sampling point of the sampling sub-circuit 10 can be the gate of the switching transistor. Based on this, the sampling sub-circuit 10 can directly and accurately collect the switching signal applied by the drive control circuit to the switching transistor.

[0056] In the second possible implementation manner, the sampling sub-circuit 10 can be connected to the target electrode of the switching transistor, that is, the sampling point of the sampling sub-circuit 10 can be the target electrode of the switching transistor. As Figure 3 、 Figure 4 and Figure 5 ​As shown, the target electrode can be the electrode in the switching transistor for connecting the inductor L0. The inductor L0 can also be referred to as a power inductor. Since the target electrode of the switching transistor needs to be connected to the inductor L0 outside the DC / DC controller 01, most DC / DC controllers 01 will lead out this target electrode, that is, the DC / DC controller 01 usually has a pin connected to this target electrode. It can be seen from this that by designing the sampling point at the target electrode connected to the power inductor L0, it can be ensured that the detection circuit provided by the embodiments of the present application is compatible with most DC / DC controllers 01.

[0057] It can be understood that the DC / DC controller 01 in the switching power supply 00 is an integrated chip, and the sampling point of the sampling sub-circuit 10 can be flexibly selected according to the signal fan-out of this integrated chip. For example, if the signal fanned out by the DC / DC controller 01 includes the switching signal of the drive control circuit, that is, the DC / DC controller 01 leads out the gate of the switching transistor, then the sampling point of the sampling sub-circuit 10 can be the gate of this switching transistor. If the DC / DC controller 01 does not lead out the gate of the switching transistor, then the sampling point of the sampling sub-circuit 10 can be the target electrode of this switching transistor.

[0058] Optionally, as Figure 4 and Figure 5 shown, the sampling sub-circuit 10 can include: a low-pass filter sub-circuit 101, and this low-pass filter sub-circuit 101 can be used to perform low-pass filtering on the sampled switching signal and transmit the switched signal after low-pass filtering to the detection sub-circuit 20.

[0059] Since the switching signal sampled by the sampling sub-circuit 10 (such as the switching signal sampled at the target electrode) is a strong drive signal, and the energy of its high-frequency part is too strong, which will cause EMC problems. Therefore, the solution provided by the embodiments of the present application can filter the switching signal through the low-pass filter sub-circuit 101 to avoid the board-level EMC problems caused by this switching signal.

[0060] Optionally, the low-pass filter sub-circuit 101 can be a filter circuit composed of passive devices. For example, the low-pass filter sub-circuit 101 can be a resistor filter circuit or an RC filter circuit. Among them, the resistor filter circuit can include one resistor, or can include multiple resistors connected in series.

[0061] Exemplarily, referring to Figure 4 and Figure 5 , the resistor R1 can form a resistor filter circuit. Or, the resistor R1 and the capacitor C1 can form an RC filter circuit. Among them, one end of the resistor R1 can be connected to the sampling point of the sampling sub-circuit 10, and the other end can be connected to one end of the capacitor C1, and the other end of this capacitor C1 can be grounded.

[0062] It can be understood that the low-pass filter sub-circuit 101 can attenuate high-frequency signals, so it can also be called an attenuation circuit. Moreover, the low-pass filter sub-circuit 101 can be arranged close to the sampling point to effectively reduce the probability of EMC problems caused by the switching signal.

[0063] As a first possible implementation, referring to Figure 4 and Figure 5 , the sampling sub-circuit 10 may further include a voltage-limiting sub-circuit 102, and the voltage-limiting sub-circuit 102 is connected to the low-pass filter sub-circuit 101. The voltage-limiting sub-circuit 102 can be used to limit the voltage of the switched signal after low-pass filtering to ensure that the switched signal after voltage-limiting can meet the requirements of the input voltage of the detection sub-circuit 20. Moreover, the voltage-limiting sub-circuit 102 can also transmit the switched signal after low-pass filtering and voltage-limiting to the detection sub-circuit 20.

[0064] Optionally, the voltage-limiting sub-circuit 102 can be a voltage-limiting circuit composed of passive devices. For example, the voltage-limiting sub-circuit 102 can be a resistor voltage-dividing circuit, a diode clamping circuit or a zener diode voltage-limiting circuit, etc.

[0065] Exemplarily, Figure 4 and Figure 5 the series-connected resistor R2 and resistor R3 in can form a resistor voltage-dividing circuit. Or, Figure 4 and Figure 5 the diode D1 in, as well as the resistors R2 and R3 can form a diode clamping circuit. Or, the diode D1 and the resistor R2 can also form a diode clamping circuit. From Figure 4 and Figure 5 it can be seen that the negative electrode of the diode D1 can be connected to the power supply terminal VCC, and the voltage of the power supply terminal vCC can be determined based on the requirements of the input voltage of the detection sub-circuit 20. For example, the voltage of the power supply terminal VCC can be 3.3 volts (V).

[0066] The zener diode voltage-limiting circuit can include a zener diode and a resistor. The negative electrode of the zener diode can be connected to one end of the resistor and connected to the detection sub-circuit 20, and the positive electrode of the zener diode can be grounded.

[0067] In this first implementation, the detection sub-circuit 20 can include a controller. The controller can be a digital controller, such as digital control devices such as FPGA, CPLD, MCU or CPU, etc. Moreover, the voltage-limiting point of the voltage-limiting sub-circuit 102 can be determined based on the operating voltage of the controller.

[0068] The controller can be used to detect the duration of the first level and the duration of the second level in the switching signal, and determine the duty cycle of the switching signal based on the duration of the first level and the duration of the second level. For example, the controller can determine the duty cycle of the switching signal based on the ratio of the duration of the first level to the duration of the second level. Wherein, the first level can be a high level relative to the second level, that is, the first level can be a high level and the second level can be a low level.

[0069] In the first implementation manner above, the sampling sub-circuit 10 can be composed of simple discrete devices (such as resistors and capacitors, etc.), and the above-mentioned discrete devices are all passive devices. Since the sampling sub-circuit 10 does not require additional chips such as operational amplifiers and ADCs, the cost and structural complexity of the detection circuit can be effectively reduced. Moreover, in the field of aerospace applications, since the above-mentioned discrete devices are insensitive to SEE and TID effects, the credibility and reliability of the detection results of the load current can be ensured.

[0070] Optionally, for the first implementation manner, the voltage limiting sub-circuit 102 can also be directly connected to the sampling point, and can directly limit the voltage of the sampled switching signal and transmit the voltage-limited switching signal to the detection sub-circuit 20. That is to say, the low-pass filtering sub-circuit 101 may not need to be provided in the sampling sub-circuit 10. For example, if the sampling point of the sampling sub-circuit 10 is the gate of the switching transistor in the DC / DC controller 01, since the probability of the switching signal sampled at the gate generating EMC problems is relatively low, the low-pass filtering sub-circuit 101 may not need to be provided in the sampling sub-circuit 10.

[0071] Or, if the voltage of the switching signal sampled by the sampling sub-circuit 10 can meet the input voltage requirements of the detection sub-circuit 20, the voltage limiting sub-circuit 102 may not need to be provided in the sampling sub-circuit 10. Correspondingly, the low-pass filtering sub-circuit 101 can directly transmit the low-pass filtered switching signal to the detection sub-circuit 20.

[0072] It can be understood that if the sampling sub-circuit 10 does not include the low-pass filtering sub-circuit 101 and the voltage limiting sub-circuit 102, the sampling sub-circuit 10 can be a signal line for transmitting the switching signal to the detection sub-circuit 20.

[0073] As a second possible implementation manner, as Figure 6 shown, the sampling sub-circuit 10 may further include an integrating sub-circuit 103, and the detection sub-circuit 20 may include an ADC 201 and a controller 202. The integrating sub-circuit 103 is respectively connected to the low-pass filtering sub-circuit 101 and the ADC 201, and the integrating sub-circuit 103 can be used to convert the low-pass filtered switching signal into a voltage signal and transmit it to the ADC 201.

[0074] The ADC 201 is used to perform analog-to-digital conversion on the voltage signal and then transmit it to the controller. The voltage signal after analog-to-digital conversion can represent the duty cycle of the switch signal. The controller 202 can be used to determine the load current of the switching power supply based on the duty cycle of the switch signal represented by the voltage signal after analog-to-digital conversion and the corresponding relationship between the calibrated duty cycle and the calibrated current stored in the controller.

[0075] It can be understood that in the second implementation manner, the calibrated duty cycle stored in the controller can also be represented by the voltage signal (i.e., the voltage value) after analog-to-digital conversion.

[0076] It can also be understood that the second implementation manner can be applied to the scenario where the switching power supply hardware product system already has an ADC redundant channel, that is, the ADC 201 can reuse the redundant channel of the existing ADC in the switching power supply hardware product system. This can effectively improve the utilization rate of the existing resources in the switching power supply. And, compared with the operational amplifier, the structure of the integrator sub-circuit is relatively simple and the cost is also lower. Therefore, it can realize the real-time detection of the load current of the switching power supply at a relatively low cost.

[0077] Optionally, the integrator sub-circuit 103 can be an integrating circuit composed of passive devices. For example, the integrator sub-circuit 103 can be an RC integrating circuit or an LC integrating circuit. Here, L refers to an inductor.

[0078] Exemplarily, referring to Figure 6 , the integrator sub-circuit 103 can be an RC integrating circuit, and the RC integrating circuit includes a resistor R2, a resistor R3, and a capacitor C2. One end of the resistor R2 is connected to the sampling point of the sampling sub-circuit 10, for example, it can be connected to the sampling point through the low-pass filtering sub-circuit 101, and the other end is connected to the input end of the ADC 201. The capacitor C2 and the resistor R3 are connected in parallel between the input end of the ADC 201 and the ground end.

[0079] Optionally, for the second implementation manner, the integrator sub-circuit 103 can also be directly connected to the sampling point and can directly convert the sampled switch signal into a voltage signal and then transmit it to the ADC 201. That is, the low-pass filtering sub-circuit 101 can be not set in the sampling sub-circuit 10. For example, if the sampling point of the sampling sub-circuit 10 is the gate of the switching transistor in the DC / DC controller 01, since the probability of generating EMC problems for the switch signal sampled at the gate is relatively low, the low-pass filtering sub-circuit 101 can also be not set in the sampling sub-circuit 10.

[0080] It can be understood that the controller in the detection sub - circuit 20 can reuse the controllers commonly found in the hardware systems of switching power supply products, such as FPGA, CPLD, MCU, or CPU, etc. Since most hardware systems of switching power supply products have controllers, by reusing the software resources of the existing controllers, it is possible to avoid adding additional chips. Based on the above analysis, it can be seen that the solution provided in the embodiments of the present application only needs to add a small number of discrete devices such as resistors and / or capacitors to achieve real - time detection of the load current. Its circuit structure is relatively simple, the cost is low, and the application flexibility is high.

[0081] In summary, the embodiments of the present application provide a detection circuit for the load current of a switching power supply. The sampling sub - circuit in the detection circuit can sample the switching signal of the DC / DC controller in the switching power supply, and the detection sub - circuit can determine the load current of the switching power supply based on the duty cycle of the switching signal and the stored corresponding relationship between the calibrated duty cycle and the calibrated current. This detection circuit can achieve real - time detection of the load current of the switching power supply. Moreover, since this detection circuit detects the magnitude of the load current based on the duty cycle of the switching signal without directly detecting the load current output by the switching power supply, there is no need to additionally set up chips such as operational amplifiers, thereby effectively simplifying the structure of the detection circuit and reducing the cost of the detection circuit.

[0082] The embodiments of the present application also provide a method for detecting the load current of a switching power supply. This method can be applied to the detection sub - circuit in the load current detection circuit provided in the above - mentioned embodiments. As Figure 7 shown, this method may include:

[0083] Step 301: When the switching power supply is connected to the first load, detect the first calibrated duty cycle of the switching signal in the DC / DC controller, and obtain the first calibrated current flowing through the first load.

[0084] The detection method provided in the embodiments of the present application may include a calibration stage and an actual measurement stage. The calibration stage can be executed before the detection circuit leaves the factory, and the actual measurement stage can be executed when the detection circuit is working properly after leaving the factory. In this calibration stage, the switching power supply can be connected to the first load. After that, the detection circuit can work normally, and the sampling sub - circuit in the detection circuit can transmit the sampled switching signal in the DC / DC controller to the detection sub - circuit. The detection sub - circuit can then detect the first calibrated duty cycle of the switching signal.

[0085] Exemplarily, the detection sub - circuit can count the duration of the high - level and the duration of the low - level of the switching signal within a certain period of time, and determine the first calibrated duty cycle of the switching signal based on the duration of the high - level and the duration of the low - level.

[0086] In this calibration phase, the detection sub - circuit can also obtain a first calibration current flowing through the first load. The first calibration current can be obtained by actual measurement (for example, measured by an ammeter), or can be calculated based on the resistance value of the first load and the voltage across the first load. And the actually measured or calculated calibration current can be manually input by the tester or automatically input by the equipment into the detection sub - circuit, that is, the detection sub - circuit can obtain the input calibration current.

[0087] Step 302: When the switching power supply is connected to the second load, detect the second calibration duty cycle of the switching signal in the DC / DC controller, and obtain a second calibration current flowing through the second load.

[0088] In this calibration phase, the switching power supply can also be connected to the second load, and the resistance value of the second load is different from that of the first load. Then, the detection sub - circuit can detect the second calibration duty cycle of the switching signal in the DC / DC controller again, and obtain the second calibration current flowing through the second load. The implementation process of step 302 can refer to the above step 301 and will not be elaborated here.

[0089] Optionally, the first load and the second load can be different loads. That is, in the calibration phase, the switching power supply can be connected to different loads respectively.

[0090] Or, the first load and the second load can be the same load, and the resistance value of the load is adjustable. Correspondingly, after the detection sub - circuit completes the detection of the first calibration duty cycle and obtains the first calibration current, the resistance value of the load can be adjusted. Then, the detection sub - circuit can detect the second calibration duty cycle and obtain the second calibration current.

[0091] Step 303: Based on the first calibration duty cycle, the first calibration current, the second calibration duty cycle, and the second calibration current, determine the corresponding relationship between the calibration duty cycle and the calibration current.

[0092] In the embodiment of the present application, after the detection sub - circuit obtains the above two sets of calibration data (each set of calibration data can include a calibration duty cycle and the corresponding calibration current), it can determine the corresponding relationship between the calibration duty cycle and the calibration current based on the two sets of calibration data.

[0093] As a possible implementation manner, the detection sub - circuit can perform curve fitting (such as linear fitting) on the two sets of calibration data to obtain the corresponding relationship between the calibration duty cycle and the calibration current. Correspondingly, the corresponding relationship can be a functional relationship between the calibration duty cycle and the calibration current.

[0094] As another possible implementation manner, the detection sub - circuit can directly record (for example, record in the form of a table) the corresponding relationship between the calibration duty cycle and the calibration current.

[0095] The above description is given by taking the example that the detection sub - circuit determines the corresponding relationship between the calibrated duty cycle and the calibrated current based on two sets of calibration data. It can be understood that the switching power supply can also be connected to more loads with different resistances, and the detection sub - circuit can also obtain more sets of calibration data by repeating the methods shown in step 301 and step 302 above. For example, the switching power supply can be connected to N loads with different resistances. Correspondingly, the detection sub - circuit can obtain N sets of calibration data. Here, N can be an integer greater than 1, and the value of N can be flexibly set according to the accuracy requirements of the detection circuit.

[0096] Optionally, after the detection sub - circuit performs curve fitting on the N sets of calibration data, the calibrated duty cycle D in and the calibrated current I out satisfy the following functional relationship:

[0097]

[0098] where k 0 to k N-1 can be the polynomial coefficients determined by the detection sub - circuit through curve fitting. The polynomial coefficients can be stored in the detection sub - circuit, that is, this corresponding relationship can be characterized by the polynomial coefficients. Since the polynomial coefficients are obtained by curve fitting of multiple sets of calibration data, the detection accuracy can be ensured when detecting current based on these polynomial coefficients.

[0099] Step 304: Detect the measured duty cycle of the switching signal in the DC / DC controller of the switching power supply.

[0100] During the actual measurement stage, the detection sub - circuit can detect the measured duty cycle of the switching signal in the DC / DC controller of the switching power supply during the actual operation of the switching power supply. For example, the detection sub - circuit can count the duration of the high - level and the low - level of the switching signal within a certain period, and determine the measured duty cycle of the switching signal based on the duration of the high - level and the low - level.

[0101] Step 305: Determine the load current of the switching power supply based on the measured duty cycle of the switching signal and the stored corresponding relationship between the calibrated duty cycle and the calibrated current.

[0102] After the detection sub - circuit detects the measured duty cycle of the switching signal, it can determine the load current of the switching power supply based on the measured duty cycle and the stored corresponding relationship between the calibrated duty cycle and the calibrated current.

[0103] For example, if the polynomial coefficients (k 0 to k N-1),the detection sub-circuit can substitute the measured duty cycle detected into the above formula (4) to calculate the load current of the switching power supply.

[0104] Alternatively, if the detection sub-circuit records the calibrated current corresponding to different calibrated duty cycles in the form of a table, the detection sub-circuit can determine the calibrated current corresponding to the measured duty cycle by looking up the table, and determine the calibrated current corresponding to the measured duty cycle as the load current of the switching power supply.

[0105] It can be understood that if the detection circuit of the load current adopts Figure 6 the scheme shown (that is, the sampling sub-circuit includes an integration sub-circuit, and the detection sub-circuit includes an ADC and a controller), in the corresponding relationship between the calibrated duty cycle and the calibrated current stored in the detection sub-circuit (such as the controller), the calibrated duty cycle can be represented by the voltage signal after analog-to-digital conversion. That is, in the above steps 301 and 302, the voltage value after the ADC in the detection sub-circuit performs analog-to-digital conversion on the voltage signal output by the integration sub-circuit can represent the calibrated duty cycle of the switching signal. Or it can be understood that: the detection sub-circuit can store the corresponding relationship between the voltage value after the analog-to-digital conversion and the calibrated current.

[0106] It can also be understood that the order of the steps of the load current detection method provided by the embodiments of the present application can be appropriately adjusted, and the steps can also be increased or decreased accordingly according to the situation. For example, the above steps 301 to 303 can be deleted according to the situation, that is, the detection sub-circuit does not need to detect the calibrated duty cycle. For example, the tester can use other detection devices to detect the corresponding relationship between the calibrated duty cycle and the calibrated current, and directly configure the detected corresponding relationship (such as polynomial coefficients) in the detection sub-circuit.

[0107] In summary, the embodiments of the present application provide a method for detecting the load current of a switching power supply. This method can detect the duty cycle of the switching signal of the DC / DC controller in the switching power supply, and based on this duty cycle and the stored corresponding relationship between the calibrated duty cycle and the calibrated current, determine the load current of the switching power supply. Thus, the real-time detection of the load current of the switching power supply can be realized. And, since this detection method detects the magnitude of the load current based on the duty cycle of the switching signal, without directly detecting the load current output by the switching power supply, there is no need to additionally set chips such as operational amplifiers in the detection circuit, thereby effectively simplifying the structure of the detection circuit and reducing the cost of the detection circuit.

[0108] The embodiments of the present application also provide a detection system for the load current of a switching power supply. As Figure 3As shown, the detection system may include a switching power supply 00 and a detection circuit for load current provided in the above embodiment. Among them, the switching power supply 00 may be a boost switching power supply or a buck switching power supply, and the embodiments of the present application do not limit this.

[0109] Optionally, the solution provided by the embodiments of the present application can be applied to the aerospace field. Since in the aerospace field, the detection of the load current of the switching power supply is highly necessary, and the cost of aerospace-grade devices is relatively higher than that of industrial-grade devices, therefore, adopting the solution provided by the embodiments of the present application in the aerospace field (such as satellite payload products) can not only effectively improve the performance of the product, but also have obvious cost advantages.

[0110] Of course, the solution provided by the embodiments of the present application can also be applied to fields such as consumer or information and communications technology (ICT) to improve the performance of products in these fields and reduce costs.

[0111] In the embodiments of the present application, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. The term "at least one" means one or more, and "a plurality" means two or more.

[0112] The term "and / or" in the present application is merely a description of the association relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0113] As described above, the above are only alternative embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A detection circuit for the load current of a switching power supply, characterized in that, the switching power supply includes a DC / DC controller, and the detection circuit includes: a sampling sub-circuit and a detection sub-circuit; the sampling sub-circuit is respectively connected to the DC / DC controller and the detection sub-circuit, and is used for sampling the switching signal in the DC / DC controller and transmitting it to the detection sub-circuit; the detection sub-circuit is used for detecting the duty cycle of the switching signal, and based on the duty cycle of the switching signal and the corresponding relationship between the calibrated duty cycle and the calibrated current stored in the detection sub-circuit, determining the load current of the switching power supply.

2. The detection circuit according to claim 1, characterized in that, the sampling sub-circuit includes: a low-pass filtering sub-circuit; the low-pass filtering sub-circuit is used for: performing low-pass filtering on the sampled switching signal; transmitting the switched signal after the low-pass filtering to the detection sub-circuit.

3. The detection circuit according to claim 2, characterized in that, the low-pass filtering sub-circuit is a resistor filtering circuit or a resistor-capacitor (RC) filtering circuit.

4. The detection circuit according to claim 2 or 3, characterized in that, the sampling sub-circuit further includes: a voltage limiting sub-circuit; the voltage limiting sub-circuit is used for: limiting the voltage of the switched signal after the low-pass filtering; transmitting the switched signal after the low-pass filtering and the voltage limiting to the detection sub-circuit.

5. The detection circuit according to claim 1, characterized in that, the sampling sub-circuit includes: a voltage limiting sub-circuit; the voltage limiting sub-circuit is used for: limiting the voltage of the sampled switching signal; transmitting the switched signal after the voltage limiting to the detection sub-circuit.

6. The detection circuit according to claim 4 or 5, characterized in that, the voltage limiting sub-circuit is a resistor voltage dividing circuit, a diode clamping circuit or a voltage stabilizing diode voltage limiting circuit.

7. The detection circuit according to any one of claims 1 to 6, characterized in that, the detection sub-circuit includes: a controller; the controller is used for detecting the duration of the first level and the duration of the second level in the switching signal, and determining the duty cycle of the switching signal based on the duration of the first level and the duration of the second level; wherein, the first level is a high level relative to the second level.

8. The detection circuit according to claim 2 or 3, characterized in that, the sampling sub-circuit further includes: an integrating sub-circuit; the detection sub-circuit includes: an analog-to-digital converter (ADC) and a controller; the integrating sub-circuit is used for converting the switched signal after the low-pass filtering into a voltage signal and transmitting it to the ADC; the ADC is used for performing analog-to-digital conversion on the voltage signal and then transmitting it to the controller, and the voltage signal after the analog-to-digital conversion is used to represent the duty cycle of the switching signal; the controller is used for determining the load current of the switching power supply based on the duty cycle of the switching signal represented by the voltage signal after the analog-to-digital conversion and the corresponding relationship between the calibrated duty cycle and the calibrated current stored in the controller.

9. The detection circuit according to claim 1, wherein, the sampling sub - circuit includes: an integration sub - circuit; the detection sub - circuit includes: an ADC and a controller; the integration sub - circuit is configured to convert the sampled switch signal into a voltage signal and transmit it to the ADC; the ADC is configured to perform analog - to - digital conversion on the voltage signal and transmit it to the controller, and the voltage signal after analog - to - digital conversion is used to represent the duty cycle of the switch signal; the controller is configured to determine the load current of the switching power supply based on the duty cycle of the switch signal represented by the voltage signal after analog - to - digital conversion and the corresponding relationship between the calibrated duty cycle and the calibrated current stored in the controller.

10. The detection circuit according to claim 8 or 9, wherein, the integration sub - circuit is an RC integration circuit or an inductance - capacitance LC integration circuit.

11. The detection circuit according to any one of claims 1 to 10, wherein, the DC / DC controller includes a switching transistor; the sampling sub - circuit is connected to the gate of the switching transistor, or the sampling sub - circuit is connected to the target electrode of the switching transistor, and the target electrode is the electrode of the switching transistor for connecting the inductor.

12. A method for detecting the load current of a switching power supply, wherein, applied to the detection sub - circuit in the detection circuit for the load current of the switching power supply according to any one of claims 1 to 11, the method includes: detecting the measured duty cycle of the switch signal in the DC / DC controller of the switching power supply; determining the load current of the switching power supply based on the measured duty cycle of the switch signal and the corresponding relationship between the calibrated duty cycle and the calibrated current stored.

13. The method according to claim 12, wherein, the corresponding relationship is a functional relationship between the calibrated duty cycle and the calibrated current.

14. The method according to claim 12 or 13, wherein, the method further includes: when the switching power supply is connected to a first load, detecting the first calibrated duty cycle of the switch signal in the DC / DC controller and obtaining the first calibrated current flowing through the first load; when the switching power supply is connected to a second load, detecting the second calibrated duty cycle of the switch signal in the DC / DC controller and obtaining the second calibrated current flowing through the second load, and the resistance value of the second load is different from that of the first load; determining the corresponding relationship between the calibrated duty cycle and the calibrated current based on the first calibrated duty cycle, the first calibrated current, the second calibrated duty cycle and the second calibrated current.

15. The method according to claim 14, wherein, the determining the corresponding relationship between the calibrated duty cycle and the calibrated current based on the first calibrated duty cycle, the first calibrated current, the second calibrated duty cycle and the second calibrated current includes: performing curve fitting on the first calibrated duty cycle, the first calibrated current, the second calibrated duty cycle and the second calibrated current to obtain the corresponding relationship between the calibrated duty cycle and the calibrated current.

16. A detection system for the load current of a switching power supply, characterized in that, the detection system includes: a switching power supply, and a detection circuit for the load current of the switching power supply according to any one of claims 1 to 11.

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