Zero-cross detection circuit, zero-cross detection method, power management chip and electronic equipment

Abstract

The invention discloses a zero-cross detection circuit, a zero-cross detection method, a power management chip and electronic equipment, and belongs to the technical field of integrated circuits. The zero-cross detection circuit comprises a first comparison circuit and a counting circuit; the first comparison circuit is used for outputting a first control signal in response to the fact that the first inductive current of the step-down circuit in the working stage of the first follow current tube is smaller than a first zero crossing point threshold value corresponding to a first counting value currently recorded by the counting circuit; the counting circuit is used for calculating the first counting value according to the first inductive current at the end of the working stage of the first follow current tube to obtain a second counting value; and the first comparison circuit is also used for outputting a second control signal in response to the situation that the second inductive current of the step-down circuit in the working stage of the second freewheeling tube is smaller than a second zero crossing threshold corresponding to the second count value. And the flexibility and the precision of controlling the working state of the follow current tube in the working stage are improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of integrated circuit technology, and in particular to a zero-crossing detection circuit, a zero-crossing detection method, a power management chip, and an electronic device. Background Art

[0002] A buck circuit is a circuit that steps down the voltage it receives, so that the voltage at its output is less than the voltage at its input. Currently, to prevent current backflow from the output to the input of a buck circuit, a zero-crossing detection circuit is typically included in the buck circuit. This zero-crossing detection circuit performs zero-crossing detection on the buck circuit, comparing the inductor current of the buck circuit with a zero-crossing threshold. Based on this comparison, the freewheeling diode's operating state is controlled.

[0003] In related art, the zero-crossing detection circuit only includes a comparison circuit. This comparison circuit is used to control the end of the freewheeling diode operating phase in each step-down diode operating phase in response to the inductor current of the step-down circuit being less than a fixed zero-crossing threshold. Relying on a fixed zero-crossing threshold to control the operating state of the freewheeling diode during each operating phase lacks flexibility and has low accuracy in controlling the operating state of the freewheeling diode during each operating phase. Summary of the Invention

[0004] The embodiments of the present application provide a zero-crossing detection circuit, a zero-crossing detection method, a power management chip, and an electronic device. The technical solution is as follows:

[0005] On the one hand, an embodiment of the present application provides a zero-crossing detection circuit, which is applied to a step-down circuit. The zero-crossing detection circuit includes a first comparison circuit and a counting circuit connected to each other;

[0006] the first comparison circuit being configured to output a first control signal in response to a first inductor current of the buck circuit in the first freewheeling tube operating stage being less than a first zero-crossing threshold corresponding to a first count value currently recorded by the counting circuit, the first control signal being configured to control the first freewheeling tube operating stage to end;

[0007] The counting circuit is configured to calculate the first count value according to the first inductor current at the end of the working phase of the first freewheeling transistor to obtain a second count value;

[0008] The first comparison circuit is further configured to output a second control signal in response to the second inductor current of the step-down circuit in the second freewheeling tube working stage being less than a second zero-crossing threshold corresponding to the second count value, wherein the second control signal is configured to control the end of the second freewheeling tube working stage, and the second freewheeling tube working stage is the next freewheeling tube working stage after the end of the first freewheeling tube working stage.

[0009] In one possible implementation, the counting circuit is configured to, in response to the first inductor current being greater than a standard zero-crossing threshold at the end of the first freewheeling transistor operating phase, perform a first operation on the first count value to obtain the second count value; and, in response to the first inductor current being less than the standard zero-crossing threshold at the end of the first freewheeling transistor operating phase, perform a second operation on the first count value to obtain the second count value;

[0010] The first operation is used to make the second zero-crossing threshold smaller than the first zero-crossing threshold; and the second operation is used to make the second zero-crossing threshold larger than the first zero-crossing threshold.

[0011] In one possible implementation, the zero-crossing detection circuit further includes a second comparison circuit connected to the counting circuit;

[0012] the second comparison circuit being configured to output a comparison signal based on a magnitude relationship between a node voltage at a first node and a ground voltage during an operation phase of the first freewheeling transistor, wherein the first node is a node between the freewheeling transistor and the inductor in the buck circuit, and the comparison signal is a first level signal or a second level signal, wherein the first level signal is configured to indicate that the node voltage is less than the ground voltage, and the second level signal is configured to indicate that the node voltage is greater than the ground voltage;

[0013] The counting circuit is further configured to determine, in response to the comparison signal most recently output by the second comparison circuit before the end of the first freewheeling tube working stage being the first level signal, that the first inductor current at the end of the first freewheeling tube working stage is greater than the standard zero-crossing threshold; and to determine, in response to the comparison signal most recently output by the second comparison circuit before the end of the first freewheeling tube working stage being the second level signal, that the first inductor current at the end of the first freewheeling tube working stage is less than the standard zero-crossing threshold.

[0014] In one possible implementation, the first size relationship is opposite to the second size relationship, the first size relationship is the size relationship between the first count value and the second count value, and the second size relationship is the size relationship between the first zero-crossing threshold and the second zero-crossing threshold; the first operation includes an addition operation, and the second operation includes a subtraction operation.

[0015] In one possible implementation, the third magnitude relationship is the same as the fourth magnitude relationship, the third magnitude relationship is the magnitude relationship between the first sampling voltage and the second sampling voltage, and the fourth magnitude relationship is the magnitude relationship between the first inductor current and the first zero-crossing threshold;

[0016] The first comparison circuit is further configured to determine that the first inductor current is less than the first zero-crossing threshold in response to the first sampling voltage being less than the second sampling voltage.

[0017] In a possible implementation, the first sampling voltage is a product of a first reference current and a reference resistance;

[0018] The second sampling voltage is the sum of the node voltage of the first node in the working stage of the first freewheeling tube and the first voltage; the first node is a node located between the freewheeling tube and the inductor in the buck circuit, and the node voltage is determined based on the first inductor current and the on-resistance of the freewheeling tube; the first voltage is the product of the target current and the reference resistance, the target current is the sum of the first reference current and the sampling current, and the product of the sampling current and the reference resistance is equal to the product of the first zero-crossing threshold and the on-resistance of the freewheeling tube.

[0019] In a possible implementation, the first count value is an N-bit binary value, the sampled current is the sum of sub-currents corresponding to each binary value in the N-bit binary value, and N is a positive integer.

[0020] In one possible implementation, the first size relationship is opposite to the second size relationship, where the first size relationship is a size relationship between the first count value and the second count value, and the second size relationship is a size relationship between the first zero-crossing threshold and the second zero-crossing threshold;

[0021] The sub-current corresponding to the ith binary value in the N-bit binary value is the product of the second reference current and the coefficient corresponding to the ith binary value; wherein, when the value of the ith binary value is 1, the coefficient corresponding to the ith binary value is 0; when the value of the ith binary value is 0, the coefficient corresponding to the ith binary value is 2 i , i is a positive integer not greater than N.

[0022] In a possible implementation, the reference resistor is the sum of on-resistances of at least one transistor, and the type of the at least one transistor is the same as that of the freewheeling transistor.

[0023] In one possible implementation, the first reference current is a zero-temperature current.

[0024] On the other hand, an embodiment of the present application further provides a zero-crossing detection method, the method comprising:

[0025] In response to the first inductor current of the buck circuit in the first freewheeling tube working stage being less than the first zero-crossing threshold corresponding to the first count value, the buck circuit outputs a first control signal, wherein the first control signal is used to control the first freewheeling tube working stage to end;

[0026] performing calculation on the first count value according to the first inductor current at the end of the working phase of the first freewheeling transistor to obtain a second count value;

[0027] In response to the second inductor current of the buck circuit in the second freewheeling tube working stage being less than the second zero-crossing threshold corresponding to the second count value, a second control signal is output, and the second control signal is used to control the end of the second freewheeling tube working stage. The second freewheeling tube working stage is the next freewheeling tube working stage after the end of the first freewheeling tube working stage.

[0028] On the other hand, an embodiment of the present application further provides a power management chip, which includes: a step-down circuit, and any of the zero-crossing detection circuits described above.

[0029] On the other hand, an embodiment of the present application further provides an electronic device, which includes: the above-mentioned power management chip.

[0030] The technical solutions provided by the embodiments of the present application bring at least the following beneficial effects:

[0031] The technical solution provided by the embodiments of the present application comprises a zero-crossing detection circuit including a first comparison circuit and a counting circuit. The counting circuit is capable of calculating an existing count value based on the inductor current at the end of the freewheeling tube operating phase, so that the first comparison circuit controls the operating state of the freewheeling tube operating phase based on the zero-crossing threshold corresponding to the latest count value. The zero-crossing threshold used to control the operating state of the freewheeling tube operating phase is relatively flexible, thereby facilitating greater flexibility in controlling the operating state of the freewheeling tube operating phase.

[0032] In addition, the count value corresponding to the zero-crossing threshold is obtained by calculating the inductor current at the end of the freewheeling tube working phase, which is beneficial to improving the matching degree between the zero-crossing threshold and the actual situation, thereby improving the accuracy of controlling the working state of the freewheeling tube working phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0034] Figure 1This is a schematic structural diagram of a step-down circuit provided in an embodiment of the present application;

[0035] Figure 2 This is a waveform diagram of a freewheeling tube working stage provided by an embodiment of the present application;

[0036] Figure 3 1 is a structural diagram of a zero-crossing detection circuit provided in an embodiment of the present application;

[0037] Figure 4 is a structural diagram of a first comparison circuit provided in an embodiment of the present application;

[0038] Figure 5 1 is a schematic structural diagram of a component providing a reference resistance according to an embodiment of the present application;

[0039] Figure 6 1 is a structural diagram of another zero-crossing detection circuit provided in an embodiment of the present application;

[0040] Figure 7 is a structural diagram of a second comparison circuit provided in an embodiment of the present application;

[0041] Figure 8 1 is a structural diagram of another zero-crossing detection circuit provided in an embodiment of the present application;

[0042] Figure 9 This is a flow chart of a zero-crossing detection method provided in an embodiment of the present application;

[0043] Figure 10 This is a schematic diagram of the structure of a power management chip provided in an embodiment of the present application;

[0044] Figure 11 This is a structural diagram of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0045] In order to make the objectives, technical solutions and advantages of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0046] Efficiency is a crucial metric for power management chips. In applications, some power management chips require very high efficiency even under light loads. A power management chip is an integrated circuit responsible for power conversion, distribution, detection, and other energy management. Its core function is to ensure that all components in electronic devices operate at optimal power levels by regulating voltage and current, while also achieving energy conservation and stable power supply. In some embodiments, a power management chip can also be referred to as a power supply chip.

[0047] A power management chip may include a buck circuit, which is a circuit that steps down the received voltage so that the voltage output at the output is less than the voltage input at the input. Zero-crossing detection circuits play a crucial role in improving efficiency. Therefore, to improve the efficiency of power management chips that include buck circuits, a zero-crossing detection circuit is typically provided for the buck circuit. The zero-crossing detection circuit provided for the buck circuit can detect zero crossings in the buck circuit to prevent current backflow from the output to the input of the buck circuit. Zero-crossing detection in the buck circuit involves comparing the inductor current of the buck circuit with a zero-crossing threshold and controlling the operating state of the freewheeling diode during the operating phase based on the comparison result. The inductor current of the buck circuit refers to the current in the inductor of the buck circuit, and the inductor current refers to the current flowing through the inductor.

[0048] In the related art, the zero-crossing detection circuit provided for the buck circuit only includes a comparison circuit. This comparison circuit is used to control the end of the freewheeling tube operating phase in response to the inductor current of the buck circuit being less than a fixed zero-crossing threshold value during each freewheeling tube operating phase of the buck circuit. Under different output voltages or different inductances, the falling slope of the inductor current is different, resulting in different zero-crossing threshold values. However, the setting of a fixed zero-crossing threshold value obviously cannot meet the requirements and lacks flexibility. The flexibility of controlling the working state of the freewheeling tube operating phase is poor, and the zero-crossing point cannot be accurately controlled in real time, resulting in low accuracy in controlling the working state of the freewheeling tube operating phase.

[0049] The embodiment of the present application provides a zero-crossing detection circuit, which is applied to a step-down circuit. In other words, the zero-crossing detection circuit can also be called a zero-crossing detection circuit applied to a step-down circuit. A step-down circuit is a circuit that steps down the received voltage so that the voltage at the output end is less than the voltage at the input end. Figure 1 The step-down circuit includes a switch tube, a freewheeling tube, an inductor L and a capacitor C.

[0050] The inductor L is connected between the first node SW and the output terminal VOUT of the step-down circuit; the capacitor C is connected between the output terminal VOUT of the step-down circuit and the ground terminal GND; the switching transistor is connected between the input terminal VIN of the step-down circuit and the first node SW; and the freewheeling transistor is connected between the first node SW and the ground terminal GND. The voltage outputted by the output terminal VOUT of the step-down circuit is used to power the load.

[0051] The switching tube can be periodically turned on and off in response to a control signal. When the switch is off, the freewheeling diode provides a freewheeling path for the current in the inductor L, allowing the current to continue flowing and preventing the inductor L from generating excessive back electromotive force. The inductor L stores and releases energy. When the switch is on, the inductor L stores energy; when the switch is off, the inductor L releases energy. The capacitor C smoothes the output voltage, reducing output voltage ripple and making the output voltage more stable.

[0052] Figure 1 The working principle of the buck circuit shown is: when the switch tube is turned on under the action of the control signal, the current flows out from the input terminal VIN, passes through the switch tube, and then flows through the inductor L. Then part of the current supplies power to the load, and part of the current charges the capacitor C. At this time, the current in the inductor L will increase linearly, and the inductor L stores energy. At this stage, the freewheeling tube is subjected to reverse voltage and is in the cut-off state.

[0053] When the switch is turned off, the current in the inductor L cannot change suddenly, so it generates a back EMF, attempting to maintain the current flow. At this point, the freewheeling diode turns on, and the current in the inductor L forms a loop through it, continuing to supply power to the load and maintaining the voltage on capacitor C. The current in the inductor L then begins to decrease linearly, releasing energy. This process repeats until the next switch-on cycle begins. By adjusting the duty cycle of the switch, the output voltage can be controlled, achieving the goal of reducing voltage.

[0054] In some embodiments, the switch tube and the freewheeling tube can be any element that can switch between the two states of conduction and shutdown. For example, the type of the switch tube and the freewheeling tube can be MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or IGBT (Insulated Gate Bipolar Transistor).

[0055] The zero-crossing detection circuit provided in the embodiments of the present application is used to compare the inductor current of the buck circuit with a zero-crossing threshold value and control the operating state of the freewheeling diode during the operating phase based on the comparison result. The freewheeling diode operating phase refers to the phase when the switch diode is off and the freewheeling diode is on. The freewheeling diode operating phase includes two operating states: normal operation and termination.

[0056] In some embodiments, the stage in which the switch tube is turned on and the freewheeling tube is turned off is called the switch tube working stage.

[0057] A buck circuit's operating cycle includes a switching transistor operating phase and a freewheeling transistor operating phase. The switching transistor operating phase in the next operating cycle begins after the freewheeling transistor operating phase in the previous operating cycle ends. In some embodiments, the switching transistor operating phase and the freewheeling transistor operating phase can be executed continuously without interruption. In other embodiments, a dead time may exist between the switching transistor operating phase and the freewheeling transistor operating phase. The dead time refers to the period of time when both the switching transistor and the freewheeling transistor are turned off.

[0058] For example, taking the freewheeling tube controlled by the freewheeling tube control signal NG (when the freewheeling tube control signal NG is a high level signal, the freewheeling tube is turned on, and when the freewheeling tube control signal NG is a low level signal, the freewheeling tube is turned off) as an example, in the freewheeling tube working stage, the waveforms of the freewheeling tube control signal NG, the current IL of the inductor L, and the voltage VSW of the first node SW can be seen in FIG. Figure 2 The area between the two dotted lines in . Figure 2 It can be seen that in the freewheeling tube working stage, the freewheeling tube control signal NG is a high-level signal, and the current IL of the inductor L gradually decreases.

[0059] Assuming that the on-resistance of the freewheeling tube is Ron, the direction of the current IL in the inductor L is Figure 1 In the direction shown in FIG, the voltage VSW of the first node SW is VSW=-IL*Ron. Since the current IL of the inductor L gradually decreases during the freewheeling tube working stage, the voltage VSW of the first node SW gradually increases.

[0060] like Figure 3 As shown, the zero-crossing detection circuit applied to the buck circuit provided in the embodiment of the present application includes a first comparison circuit 10 and a counting circuit 20 connected to each other.

[0061] The first comparison circuit 10 is configured to output a first control signal in response to a first inductor current of the buck circuit in the first freewheeling transistor operating phase being less than a first zero-crossing threshold corresponding to a first count value currently recorded by the counting circuit 20. The first control signal is configured to control the first freewheeling transistor operating phase to end.

[0062] The counting circuit 20 is configured to calculate the first count value according to the first inductor current at the end of the first freewheeling transistor working phase to obtain a second count value;

[0063] The first comparison circuit 10 is further configured to output a second control signal in response to the second inductor current of the buck circuit in the second freewheeling tube working stage being less than a second zero-crossing threshold corresponding to the second count value. The second control signal is configured to control the end of the second freewheeling tube working stage. The second freewheeling tube working stage is the next freewheeling tube working stage after the end of the first freewheeling tube working stage.

[0064] The first freewheeling tube working stage refers to the freewheeling tube working stage in the first working cycle of the buck circuit. The first working cycle can be any working cycle of the buck circuit. The first inductor current refers to the inductor in the buck circuit (such as Figure 1 The inductor L) has a current in the first freewheeling tube working stage. It should be noted that the first inductor current changes continuously with time.

[0065] The first count value refers to the value recorded by the counting circuit 20 in the first freewheeling diode operating stage. In some embodiments, the first count value may be a default count value of the counting circuit 20. In other embodiments, the first count value may also refer to the count value obtained by the counting circuit 20 after calculating the inductor current at the end of the previous freewheeling diode operating stage. The previous freewheeling diode operating stage refers to the freewheeling diode operating stage most recently executed before the first freewheeling diode operating stage, and may also be referred to as the freewheeling diode operating stage in the operating cycle before the first operating cycle.

[0066] In the embodiment of the present application, each count value recorded by the counting circuit 20 corresponds to a zero crossing threshold value, and the zero crossing threshold values ​​corresponding to different count values ​​are different, so as to improve the flexibility of the working state of the freewheeling tube working phase. The embodiment of the present application does not limit the corresponding relationship between the count value and the zero crossing threshold value corresponding to the count value. In some embodiments, the count value and the zero crossing threshold value corresponding to the count value are negatively correlated, that is, the larger the count value is, the smaller the zero crossing threshold value corresponding to the count value is. In other embodiments, the count value and the zero crossing threshold value corresponding to the count value are positively correlated, that is, the larger the count value is, the larger the zero crossing threshold value corresponding to the count value is.

[0067] The embodiment of the present application does not limit the form of the count value recorded by the counting circuit 20. For example, the count value can be in the form of a decimal value or an N-bit binary value. N is a positive integer. The value of N can be set based on experience or flexibly adjusted based on demand. For example, the value of N can be 2, 4, 6, etc. For the case where the count value is in the form of an N-bit binary value, the zero-crossing threshold has a value of 2. N situation.

[0068] In some embodiments, when the count value is in the form of an N-bit binary value, the counting circuit 20 may also be referred to as an N-bit digital counter, an N-bit counter, etc.

[0069] The first comparison circuit 10 can control the operating state of the first freewheeling diode in the operating stage according to the first count value. Exemplarily, the process of the first comparison circuit 10 controlling the operating state of the first freewheeling diode in the operating stage according to the first count value includes: in response to the first inductor current being less than a first zero-crossing threshold corresponding to the first count value, the first comparison circuit 10 outputs a first control signal, the first control signal being used to control the end of the first freewheeling diode operating stage; and in response to the first inductor current being greater than the first zero-crossing threshold corresponding to the first count value, the first comparison circuit 10 outputs a third control signal, the third control signal being used to control the normal operation of the first freewheeling diode in the operating stage.

[0070] In some embodiments, the first inductor current may also be equal to the first zero-crossing threshold corresponding to the first count value. The embodiment of the present application does not limit the control method of the first comparison circuit 10 when the first inductor current is equal to the first zero-crossing threshold corresponding to the first count value. Exemplarily, the first comparison circuit 10 outputs a first control signal to control the end of the working phase of the first freewheeling tube, or outputs a third control signal to control the normal operation of the working phase of the first freewheeling tube in response to the first inductor current being equal to the first zero-crossing threshold corresponding to the first count value.

[0071] In an exemplary embodiment, the buck circuit includes a first control circuit configured to control the state of a freewheeling diode. Exemplarily, the first control circuit controls the state of the freewheeling diode by applying different voltages to a control gate of the freewheeling diode.

[0072] In an exemplary embodiment, the first comparison circuit 10 is connected to the first control circuit, and the first control signal output by the first comparison circuit 10 can be synchronized to the first control circuit, and the first control circuit turns off the freewheeling tube according to the first control signal to end the working phase of the first freewheeling tube. The third control signal output by the first comparison circuit 10 can be synchronized to the first control circuit, and the first control circuit continues to turn on the freewheeling tube according to the third control signal to enable the first freewheeling tube to operate normally in the working phase. Exemplarily, the first control signal and the third control signal are two different level signals, for example, the first control signal is a high level signal and the third control signal is a low level signal; or, the first control signal is a low level signal and the third control signal is a high level signal.

[0073] Exemplarily, the first control circuit controls the state of the freewheeling tube via the freewheeling tube control signal NG (when the freewheeling tube control signal NG is a high-level signal, the freewheeling tube is turned on, and when the freewheeling tube control signal NG is a low-level signal, the freewheeling tube is turned off). The first freewheeling tube operating phase begins when the freewheeling tube control signal NG is a high-level signal. Exemplarily, the first control circuit turns off the freewheeling tube according to the first control signal in the following manner: the first control circuit adjusts the freewheeling tube control signal NG from a high-level signal to a low-level signal according to the first control signal, and turns off the freewheeling tube according to the low-level signal. The first control circuit continues to turn on the freewheeling tube according to the third control signal in the following manner: the first control circuit maintains the freewheeling tube control signal NG as a high-level signal according to the third control signal, and continues to turn on the freewheeling tube according to the high-level signal.

[0074] In an exemplary embodiment, the first comparison circuit 10 can determine the magnitude relationship between the first inductor current and the first zero-crossing threshold corresponding to the first count value by directly comparing the first inductor current with the first zero-crossing threshold corresponding to the first count value. In this case, the first comparison circuit 10 has the function of detecting the first inductor current or has the function of receiving the first inductor current detected by a current detection element and transmitted to the first comparison circuit 10. It should be noted that the first comparison circuit 10 or the current detection element detecting the first inductor current means that the first comparison circuit 10 or the current detection element periodically detects the first inductor current. The period for detecting the first inductor current can be set based on experience or can be flexibly adjusted according to needs, and this is not limited in the present embodiment.

[0075] Exemplarily, the first comparison circuit 10 may record a correspondence between a count value and a zero-crossing threshold value. The first comparison circuit 10 may determine a first zero-crossing threshold value based on the first count value, and then compare the detected first inductor current or the received first inductor current with the first zero-crossing threshold value to obtain a magnitude relationship between the first inductor current and the first zero-crossing threshold value.

[0076] In one possible implementation, the third magnitude relationship is the same as the fourth magnitude relationship. The third magnitude relationship is the magnitude relationship between the first sampled voltage and the second sampled voltage, and the fourth magnitude relationship is the magnitude relationship between the first inductor current and the first zero-crossing threshold. The first comparison circuit 10 can indirectly determine the magnitude relationship between the first inductor current and the first zero-crossing threshold by determining the magnitude relationship between the first sampled voltage and the second sampled voltage. In this case, the first comparison circuit 10 is further configured to determine that the first inductor current is less than the first zero-crossing threshold in response to the first sampled voltage being less than the second sampled voltage. Comparing voltages is less difficult than comparing currents. Determining the magnitude relationship between the first inductor current and the first zero-crossing threshold by comparing the magnitude relationship between the first sampled voltage and the second sampled voltage is more convenient.

[0077] In an exemplary embodiment, the first sampling voltage is the product of a first reference current and a reference resistor. The second sampling voltage is the sum of a node voltage at the first node during the first freewheeling diode operating phase and the first voltage. The first node is a node located between the freewheeling diode and the inductor in the buck circuit, and the node voltage is determined based on the first inductor current and the on-resistance of the freewheeling diode. The first voltage is the product of a target current and a reference resistor. The target current is the sum of the first reference current and the sampling current. The product of the sampling current and the reference resistor is equal to the product of the first zero-crossing threshold and the on-resistance of the freewheeling diode.

[0078] The first node is a node between the freewheeling diode and the inductor in the buck circuit. For example, the first node can be Figure 1 The node voltage of the first node SW in the first freewheeling diode operating phase changes continuously over time. The node voltage is determined based on the first inductor current and the on-resistance of the freewheeling diode. The embodiment of the present application uses the positive direction of the first inductor current as an example, that is, the direction of the first inductor current flowing from the inductor through the freewheeling diode to the first node. In this case, the node voltage is the difference between the ground voltage and the on-voltage, and the on-voltage is the product of the first inductor current and the on-resistance of the freewheeling diode. Taking the ground voltage as zero as an example, the node voltage is the inverse of the product of the first inductor current and the on-resistance of the freewheeling diode.

[0079] The first reference current and the reference resistance can be set based on experience, or can be flexibly adjusted according to the application scenario, which is not limited in the embodiments of the present application.

[0080] For example, the first sampling voltage may be calculated based on the following formula 1, and the second sampling voltage may be calculated based on the following formula 2:

[0081] SMP_GND=I1*R (Formula 1)

[0082] SMP_SW=VSW+(I1+I2)*R (Formula 2)

[0083] Wherein, SMP_GND represents the first sampled voltage; SMP_SW represents the second sampled voltage; I1 represents the first reference current; R represents the reference resistor; VSW represents the node voltage of the first node during the first freewheeling diode operating phase, which is calculated using Formula 3 below; I2 represents the sampled current, and the relationship between I2 and the first zero-crossing threshold is shown in Formula 4. In some embodiments, the node voltage VSW of the first node during the first freewheeling diode operating phase and the second sampled voltage SMP_SW can both be considered voltage signals obtained by converting the first inductor current.

[0084] VSW=-IL*Ron (Formula 3)

[0085] I2*R = Ith1*Ron (Equation 4)

[0086] Where, IL represents the first inductor current, and the positive direction of the first inductor current is the direction from the inductor through the freewheeling diode into the first node (such as the direction of IL shown in Figure 1 ); Ron represents the on-resistance of the freewheeling diode; Ith1 represents the first zero-crossing threshold.

[0087] According to the above Equations 1 to 4, it can be deduced that when SMP_GND < SMP_SW, IL < Ith1, that is, when the first sampling voltage is less than the second sampling voltage, the first inductor current is less than the first zero-crossing threshold.

[0088] In a possible implementation manner, the first count value is an N-bit binary value, and the sampling current is the sum of sub-currents corresponding to each bit binary value in the N-bit binary value, where N is a positive integer.

[0089] The value of N can be set according to experience, and the value of N can be set according to experience or can be flexibly adjusted according to requirements. Exemplarily, the value of N can be 2, or can be 4, or can also be 6, etc.

[0090] Taking the value of N as 6 as an example, the N-bit binary value can be respectively represented as CNT5, CNT4, CNT3, CNT2, CNT1, and CNT0 from the highest bit (the 5th bit) to the lowest bit (the 0th bit). According to the first count value, the value of each bit binary value can be determined, and the value of each bit binary value is 0 or 1. In some embodiments, the value of each bit binary value can also be referred to as the code value of each bit binary value.

[0091] The embodiments of the present application do not limit the calculation method of the sub-current corresponding to any bit binary value (referred to as the i-th bit binary value) in the N-bit binary value, as long as it can ensure that the sampling current and the first zero-crossing threshold have the relationship defined in Equation 4.

[0092] In a possible implementation manner, the first magnitude relationship is opposite to the second magnitude relationship. The first magnitude relationship is the magnitude relationship between the first count value and the second count value, and the second magnitude relationship is the magnitude relationship between the first zero-crossing threshold and the second zero-crossing threshold, that is, the count value and the zero-crossing threshold corresponding to the count value are negatively correlated. In this case, the sub-current corresponding to the i-th bit binary value in the N-bit binary value is the product of the second reference current and the coefficient corresponding to the i-th bit binary value. Where, when the value of the i-th bit binary value is 1, the coefficient corresponding to the i-th bit binary value is 0; when the value of the i-th bit binary value is 0, the coefficient corresponding to the i-th bit binary value is 2 i , where i is a positive integer not greater than N.

[0093] The second reference current can be set based on experience or flexibly adjusted according to the application scenario, which is not limited in the embodiment of the present application. The second reference current can be the same as the first reference current or different from the first reference current.

[0094] For example, taking the value of N as 6, the sampling current can be calculated based on Formula 5:

[0095] I2=(1-CNT5)*32*I0+(1-CNT4)*16*I0+(1-CNT3)*8*I0+(1-CNT2)*4*I0+(1-CNT1)*2*I0+(1-CNT0)*I0 (Formula 5)

[0096] Among them, I2 represents the sampling current; (1-CNT5)*32 represents the coefficient corresponding to CNT5; (1-CNT4)*16 represents the coefficient corresponding to CNT4; (1-CNT3)*8 represents the coefficient corresponding to CNT3; (1-CNT2)*4 represents the coefficient corresponding to CNT2; (1-CNT1)*2 represents the coefficient corresponding to CNT1; (1-CNT0) represents the coefficient corresponding to CNT0; I0 represents the second reference current.

[0097] For example, taking the first count value as 100000, that is, the value of CNT5 is 1, the value of CNT4 is 0, the value of CNT3 is 0, the value of CNT2 is 0, the value of CNT1 is 0, and the value of CNT0 is 0, the sampling current I2=31*I0 is calculated according to Formula 5.

[0098] According to the above content, by adjusting the count value, the values ​​of CNT5, CNT4, CNT3, CNT2, CNT1 and CNT0 can be adjusted, thereby achieving adjustment of the sampling current and the zero-crossing threshold.

[0099] The embodiment of the present application does not limit the structure of the first comparison circuit 10 .

[0100] Exemplarily, the first comparison circuit 10 may include a current determination subcircuit, a sampling subcircuit, and a comparison subcircuit. The current determination subcircuit is used to determine the sampled current, the sampling subcircuit is used to determine a first sampled voltage and a second sampled voltage, and the comparison subcircuit is used to determine the magnitude relationship between the first inductor current and a first zero-crossing threshold based on the magnitude relationship between the first sampled voltage and the second sampled voltage, and output a control signal for controlling the operating state of the first freewheeling diode during the operating phase based on the magnitude relationship between the first inductor current and the first zero-crossing threshold. Exemplarily, the comparison subcircuit may output a first control signal when the first inductor current is less than the first zero-crossing threshold, output a third control signal when the first inductor current is greater than the first zero-crossing threshold, and output either the first control signal or the third control signal when the first inductor current is equal to the first zero-crossing threshold.

[0101] For example, taking the first count value as a 6-bit binary value, the first control signal as a high-level signal, and the third control signal as a low-level signal, the structure of the first comparison circuit 10 can be as follows: Figure 4 shown.

[0102] exist Figure 4 In the illustrated first comparison circuit 10, the first comparison circuit 10 includes 16 P-type MOSFETs (MP1-MP16), three N-type MOSFETs (MN1-MN3), an inverter INV1, and two sampling elements (sampling element 11 and sampling element 12) with resistors R. MP1-MP10 and MN1-MN3 are turned on under the control of a current source IS and a voltage source VDD. The current flowing into MN1 and MN2 is the same, both being a first reference current I1.

[0103] The source input of MP5 has a current of 32*I0, the source input of MP6 has a current of 16*I0, the source input of MP7 has a current of 8*I0, the source input of MP8 has a current of 4*I0, the source input of MP9 has a current of 2*I0, and the source input of MP10 has a current of I0. The state of MP11 is controlled by CNT5. When the value of CNT5 is 1, MP11 is turned off. When the value of CNT5 is 0, MP11 is turned on. The state of MP12 is controlled by CNT4. When the value of CNT4 is 1, MP12 is turned off. When the value of CNT4 is 0, MP12 is turned on. The state of MP13 is controlled by CNT3. When the value of CNT3 is 1, MP13 is turned off. When the value of CNT3 is 0, MP13 is turned on. MP14's state is controlled by CNT2: when CNT2 is 1, MP14 is off; when CNT2 is 0, MP14 is on. MP15's state is controlled by CNT1: when CNT1 is 1, MP15 is off; when CNT1 is 0, MP15 is on. MP16's state is controlled by CNT0: when CNT0 is 1, MP16 is off; when CNT0 is 0, MP16 is on. The total current flowing through MP11 to MP16 is the sampling current I2.

[0104] Sampling element 11 is connected between the source of MN2 and a first sampling point located between the freewheeling diode and ground. Sampling element 12 is connected between the source of MN1 and a second sampling point located between the first node SW and the freewheeling diode. In some embodiments, sampling elements 11 and 12 can be considered components of a freewheeling diode voltage divider sampling circuit, which is used to convert the inductor current into a voltage signal (e.g., the node voltage VSW at the first node and the first sampling voltage SMP_SW).

[0105] The voltage at the source of MN2 is a first sampling voltage SMP_GND, which is the product of the first reference current I1 and the reference resistor R. The voltage at the source of MN1 is a second sampling voltage SMP_SW, which is the sum of the node voltage of the first node SW and the first voltage, which is the product of the target current and the reference resistor, and the target current is the sum of the first reference current I1 and the sampling current I2.

[0106] When the first sampling voltage SMP_GND is less than the second sampling voltage SMP_SW (i.e., the first inductor current is less than the first zero-crossing threshold), the higher second sampling voltage SMP_SW will pull up the voltage of the control gate of MN3, thereby causing the voltage of the drain of MN3 to become lower. That is, the voltage input to the input end of the inverter INV1 is a lower voltage. After the inverter INV1 inverts the lower voltage, the output OUT1 is a high-level signal. When the first sampling voltage SMP_GND is greater than the second sampling voltage SMP_SW (i.e., the first inductor current is greater than the first zero-crossing threshold), the lower second sampling voltage SMP_SW will pull down the voltage of the control gate of MN3, thereby causing the voltage of the drain of MN3 to become higher. That is, the voltage input to the input end of the inverter INV1 is a higher voltage. After the inverter INV1 inverts the higher voltage, the output OUT1 is a low-level signal.

[0107] It should be noted that Figure 4 This is only an exemplary structural diagram of the first comparison circuit 10, and the embodiments of the present application are not limited thereto. It is sufficient as long as the first comparison circuit 10 can determine the magnitude relationship between the first inductor current and the first zero-crossing threshold corresponding to the first count value and output a corresponding control signal based on the magnitude relationship.

[0108] In some embodiments, the zero-crossing detection circuit may further include a voltage divider sampling circuit, which may obtain a first sampling voltage and a second sampling voltage, and output the first sampling voltage and the second sampling voltage to a first comparison circuit 10. The first comparison circuit 10 may be a comparator that compares the input first sampling voltage and the second sampling voltage.

[0109] In one possible implementation, the reference resistance is the sum of the on-resistances of at least one transistor, and the type of at least one transistor is the same as that of the freewheeling diode. That is, at least one transistor connected in series can be used as an element providing the reference resistance. The type of at least one transistor is the same as that of the freewheeling diode. For example, if the freewheeling diode is an N-type MOSFET, then at least one transistor is also an N-type MOSFET; if the freewheeling diode is a P-type MOSFET, then at least one transistor is also a P-type MOSFET.

[0110] For example, the element providing the reference resistance may be Figure 5 As shown, in Figure 5 In the embodiment, the elements providing the reference resistance are three N-type MOSFETs connected in series, the control gates of the three N-type MOSFETs connected in series are connected to a voltage source VDD, and the voltage source VDD is used to turn on the three N-type MOSFETs connected in series, and the sum of the on-resistances of the three N-type MOSFETs connected in series is the reference resistance R.

[0111] Based on this, the element providing the reference resistor is prepared using the same process as the freewheeling tube, which is beneficial to reducing the deviation caused by the different preparation processes on the zero-crossing detection process, improving the accuracy of the zero-crossing detection result by reducing the deviation caused by temperature changes on the zero-crossing detection. In some embodiments, the preparation process can be represented by a process angle (corner), which refers to the deviation range of the electrical characteristics of the component (such as threshold voltage, carrier mobility, resistance / capacitance value, etc.) due to the deviation of the semiconductor manufacturing process (such as doping concentration, transistor size, oxide layer thickness, etc.).

[0112] In one possible implementation, the first reference current is a zero-temperature current. A zero-temperature current refers to a current that hardly fluctuates with temperature changes. For example, Figure 4 The current provided by the current source IS is a zero-temperature current, thereby making the first reference current a zero-temperature current. When the first reference current is a zero-temperature current, it is beneficial to reduce the deviation caused by temperature changes in zero-crossing detection, thereby improving the accuracy of the zero-crossing detection results of the zero-crossing detection circuit. In some embodiments, the zero-temperature current can also be referred to as a trimmed current.

[0113] In an exemplary embodiment, the second reference current is also a zero-temperature current to further reduce the deviation of zero-crossing detection caused by temperature changes and improve the accuracy of zero-crossing detection results.

[0114] After the first comparison circuit 10 outputs the first control signal to control the end of the first freewheeling diode operating phase, the counting circuit 20 calculates the first count value based on the first inductor current at the end of the first freewheeling diode operating phase to obtain a second count value. The second count value provides a reference for the first comparison circuit 10 to control the operating state of the second freewheeling diode operating phase. The second freewheeling diode operating phase is the next freewheeling diode operating phase after the end of the first freewheeling diode operating phase.

[0115] In one possible implementation, the counting circuit 20 is configured to perform a first operation on the first count value to obtain a second count value in response to the first inductor current being greater than a standard zero-crossing threshold at the end of the first freewheeling diode operating phase; and to perform a second operation on the first count value to obtain a second count value in response to the first inductor current being less than the standard zero-crossing threshold at the end of the first freewheeling diode operating phase. The first operation is configured to cause the second zero-crossing threshold to be less than the first zero-crossing threshold, and the second operation is configured to cause the second zero-crossing threshold to be greater than the first zero-crossing threshold.

[0116] The standard zero-crossing threshold value refers to the zero-crossing threshold value under ideal conditions, and illustratively, the standard zero-crossing threshold value is zero. If the first inductor current at the end of the first freewheeling tube operating phase is greater than the standard zero-crossing threshold value, then it is explained that the first freewheeling tube operating phase has just been ended in advance before the first inductor current drops to the standard zero-crossing threshold value, that is, the first zero-crossing threshold value is the value greater than the standard zero-crossing threshold value. Since the best zero-crossing threshold value is the standard zero-crossing threshold value, it is necessary to adjust the count value in the direction of reducing the zero-crossing threshold value. Therefore, counting circuit 20 carries out the first operation to the first count value, and the second zero-crossing threshold value corresponding to the second count value obtained by carrying out the first operation to the first count value is less than the first zero-crossing threshold value.

[0117] If the first inductor current at the end of the first freewheeling tube operating phase is less than the standard zero-crossing threshold, it indicates that the first freewheeling tube operating phase has not been terminated in a timely manner when the first inductor current drops to the standard zero-crossing threshold, which means that the first zero-crossing threshold is less than the value of the standard zero-crossing threshold. Since the optimal zero-crossing threshold is the standard zero-crossing threshold, it is necessary to adjust the count value in a direction that increases the zero-crossing threshold. Therefore, the counting circuit 20 performs a second operation on the first count value, and the second zero-crossing threshold corresponding to the second count value obtained by performing the first operation on the first count value is greater than the first zero-crossing threshold.

[0118] In some embodiments, the first inductor current at the end of the first freewheeling tube working stage may also be equal to the standard zero-crossing threshold. In this case, it indicates that the first zero-crossing threshold is equal to the value of the standard zero-crossing threshold. The first count value can be kept unchanged and used as the second count value.

[0119] The specific circumstances of the first operation and the second operation in the embodiment of the present application are not limited.

[0120] In some embodiments, the first magnitude relationship is opposite to the second magnitude relationship. The first magnitude relationship is the magnitude relationship between the first count value and the second count value, and the second magnitude relationship is the magnitude relationship between the first zero-crossing threshold and the second zero-crossing threshold. That is, the count value and the corresponding zero-crossing threshold are negatively correlated. In this case, the first operation includes an addition operation, and the second operation includes a subtraction operation. In other words, when the first inductor current at the end of the first freewheeling diode operating phase is greater than the standard zero-crossing threshold, the counting circuit 20 performs an addition operation on the first count value to obtain the second count value. Adding the first count value may mean adding a first reference value to the first count value. The first reference value can be set based on experience, for example, the first reference value can be 1. When the first inductor current at the end of the first freewheeling diode operating phase is less than the standard zero-crossing threshold, the counting circuit 20 performs a subtraction operation on the first count value to obtain the second count value. Subtracting the first count value may mean subtracting a second reference value from the first count value. The second reference value can be set based on experience and can be the same as or different from the first reference value. For example, the second reference value and the first reference value are both 1.

[0121] In one possible implementation, see Figure 6 The zero-crossing detection circuit further includes a second comparison circuit 30 connected to the counting circuit 20 .

[0122] The second comparison circuit 30 is configured to output a comparison signal based on the magnitude relationship between the node voltage at the first node and the ground voltage during the first freewheeling diode operating phase. The first node is a node located between the freewheeling diode and the inductor in the buck circuit. The comparison signal is a first level signal or a second level signal. The first level signal is used to indicate that the node voltage is less than the ground voltage, and the second level signal is used to indicate that the node voltage is greater than the ground voltage. The counting circuit 20 is further configured to determine that the first inductor current at the end of the first freewheeling diode operating phase is greater than a standard zero-crossing threshold in response to the comparison signal most recently output by the second comparison circuit 30 before the end of the first freewheeling diode operating phase being a first level signal; and to determine that the first inductor current at the end of the first freewheeling diode operating phase is less than the standard zero-crossing threshold in response to the comparison signal most recently output by the second comparison circuit 30 before the end of the first freewheeling diode operating phase being a second level signal.

[0123] The second comparator 30 may be any element capable of comparing the node voltage of the first node with the ground voltage.

[0124] In an exemplary embodiment, the second comparison circuit 30 operates during the freewheeling transistor operating phase and stops operating after the freewheeling transistor operating phase ends to reduce power consumption. For example, the freewheeling transistor state can be controlled by the freewheeling transistor control signal NG. The operation of the second comparison circuit 30 during the freewheeling transistor operating phase can be referred to as the second comparison circuit 30 operating during the phase in which the freewheeling transistor is turned on by the freewheeling transistor control signal NG. In some embodiments, the freewheeling transistor control signal NG can also be referred to as the clock signal CLK that controls the operation of the second comparison circuit 30.

[0125] In an exemplary embodiment, the second comparison circuit 30 is connected to the counting circuit 20 , and the comparison signal output by the second comparison circuit 30 can be synchronized to the counting circuit 20 .

[0126] Exemplarily, the first level signal and the second level signal are two different level signals. For example, the first level signal is a high level signal and the second level signal is a low level signal. For another example, the first level signal is a low level signal and the second level signal is a high level signal.

[0127] In an exemplary embodiment, the second comparison circuit 30 may periodically obtain the magnitude relationship between the node voltage and the ground voltage, and output a comparison signal to the counting circuit 20 each time the magnitude relationship between the node voltage and the ground voltage is obtained. The period for obtaining the magnitude relationship between the node voltage and the ground voltage may be set based on experience or flexibly adjusted as needed, and is not limited in this embodiment of the present application.

[0128] The present embodiment does not limit the structure of the second comparison circuit 30, as long as it can obtain the magnitude relationship between the node voltage and the ground voltage and output a corresponding signal based on the magnitude relationship. In some embodiments, the second comparison circuit 30 can receive the node voltage transmitted by the voltage divider sampling circuit, and the second comparison circuit 30 can be a comparator that compares the node voltage with the ground voltage.

[0129] In some embodiments, the first level signal is a high level signal and the second level signal is a low level signal, that is, the second comparison circuit 30 outputs a high level signal when the node voltage is less than the ground voltage and outputs a low level signal when the node voltage is greater than the ground voltage. For example, the structure of the second comparison circuit 30 can be as follows: Figure 7 As shown. Figure 7The second comparison circuit 30 shown includes four P-type MOSFETs (MP1'-MP4'), seven N-type MOSFETs (MN1'-MN7'), and an inverter INV2. The states of MP1', MP4', MN6', and MN7' are controlled by a freewheeling transistor control signal NG. The source of MN3' is connected to the node voltage VSW at the first node. The sources of MP1'-MP4' are connected to a voltage source VDD. The drain of MN1' is connected to a current source ISC. The signal OUT2 output by the inverter INV2 is the comparison signal.

[0130] The current ratio of MN1', MN2' and MN3' is 1:1:1; MN4' and MN5' are the same size, MN6' and MN7' are the same size; MP1' and MP2' are the same size, MP3' and MP4' are the same size.

[0131] When the freewheeling diode control signal NG is a low-level signal, i.e., the freewheeling diode operation phase ends, the second comparison circuit 30 does not need to operate, and the output OUT2 of the inverter INV2 is a reset signal. For example, when the freewheeling diode control signal NG is a low-level signal, MP1' and MP4' are turned on, MN6' and MN7' are turned off, and the voltage input to the input terminal of the inverter INV2 is a relatively high voltage (close to the voltage provided by the voltage source VDD). After the inverter INV2 inverts the relatively high voltage, the output OUT2 is a low-level signal, i.e., the reset signal is a low-level signal.

[0132] When the freewheeling tube control signal NG is high, that is, the freewheeling tube works normally, the second comparator 30 starts to work. When the freewheeling tube control signal NG is high, MP1' and MP4' are turned off, and MN6' and MN7' are turned on. When the input node voltage VSW is lower than the ground voltage GND, the lower node voltage VSW will pull down the voltage of the drain of MN3', and then pull down the voltage of the drain of MN4' and the voltage of the drain of MN7', that is, the voltage input to the input end of the inverter INV2 is a lower voltage, and after the inverter INV2 inverts the lower voltage, the output OUT2 is a high-level signal; when the input node voltage VSW is higher than the ground voltage GND, the higher node voltage VSW will pull up the voltage of the drain of MN3', and then pull up the voltage of the drain of MN4' and the voltage of the drain of MN7', that is, the voltage input to the input end of the inverter INV2 is a higher voltage, and after the inverter INV2 inverts the higher voltage, the output OUT2 is a low-level signal.

[0133] In some embodiments, the process of the second comparison circuit 30 outputting the comparison signal may also be referred to as a process of detecting the inductor current in real time.

[0134] During the first freewheeling diode operating phase, the second comparison circuit 30 continuously outputs a comparison signal to the counting circuit 20. The counting circuit 20 determines the magnitude relationship between the first inductor current at the end of the first freewheeling diode operating phase and the standard zero-crossing threshold value based on the most recent comparison signal output by the second comparison circuit 30 before the end of the first freewheeling diode operating phase. The most recent comparison signal output by the second comparison circuit 30 before the end of the first freewheeling diode operating phase can be considered the comparison signal output closest to the end of the first freewheeling diode operating phase. This comparison signal can more accurately represent the magnitude relationship between the first inductor current at the end of the first freewheeling diode operating phase and the standard zero-crossing threshold value.

[0135] When the comparison signal most recently output by the second comparison circuit 30 before the first freewheeling tube working stage ends is a second level signal, it indicates that the node voltage at the end of the first freewheeling tube working stage is greater than the ground voltage.

[0136] The present embodiment of the present application is described by taking the positive direction of the first inductor current as the direction of flow from the inductor through the freewheeling diode into the first node, the standard zero-crossing threshold value as zero, and the ground voltage as zero as an example. According to the above formula 3, when the ground voltage is zero, the node voltage is the inverse of the product of the first inductor current and the on-resistance of the freewheeling diode. Therefore, if the comparison signal most recently output by the second comparison circuit 30 before the end of the first freewheeling diode operating phase is a first level signal, it means that the node voltage at the end of the first freewheeling diode operating phase is less than zero (ground voltage), thereby indicating that the first inductor current at the end of the first freewheeling diode operating phase is greater than zero (standard zero-crossing threshold value). If the comparison signal most recently output by the second comparison circuit 30 before the end of the first freewheeling diode operating phase is a second level signal, it means that the node voltage at the end of the first freewheeling diode operating phase is greater than zero (ground voltage), thereby indicating that the first inductor current at the end of the first freewheeling diode operating phase is less than zero (standard zero-crossing threshold value).

[0137] After obtaining the second count value, the counting circuit 20 synchronizes the second count value with the first comparison circuit 10, so that the first comparison circuit 10 controls the operating state of the second freewheeling diode operating stage based on the second count value. The second freewheeling diode operating stage is the next freewheeling diode operating stage after the first freewheeling diode operating stage ends. In other words, the second freewheeling diode operating stage is the freewheeling diode operating state in the second operating cycle of the buck circuit, and the second operating cycle is the operating cycle following the first operating cycle.

[0138] The inductor in the step-down circuit (such as Figure 1The current of the inductor L) in the second freewheeling tube working stage is called the second inductor current. The first comparison circuit 10 controls the working state of the second freewheeling tube working stage according to the second count value in the following manner: in response to the second inductor current being less than the second zero-crossing threshold corresponding to the second count value, output a second control signal, the second control signal being used to control the end of the second freewheeling tube working stage; in response to the second inductor current being greater than the second zero-crossing threshold corresponding to the second count value, output a fourth control signal, the fourth control signal being used to control the normal operation of the second freewheeling tube working stage; in response to the second inductor current being equal to the second zero-crossing threshold corresponding to the second count value, output a second control signal or output a fourth control signal. Exemplarily, the second control signal is the same as the first control signal, and the fourth control signal is the same as the third control signal. The principle of the first comparison circuit 10 controlling the working state of the second freewheeling tube working stage according to the second count value is the same as the principle of the first comparison circuit 10 controlling the working state of the first freewheeling tube working stage according to the first count value, and will not be repeated here.

[0139] For example, the structure of the zero-crossing detection circuit can be as follows: Figure 8 As shown, in Figure 8 In the illustrated zero-crossing detection circuit, the second comparison circuit 30 compares the node voltage VSW of the first node with the ground voltage GND in real time during each freewheeling diode operating phase, and outputs a comparison signal OUT2 to the counting circuit 20. The counting circuit 20 performs a corresponding operation on the existing count value based on the comparison signal OUT2, and outputs the calculated count value to the first comparison circuit 10. In a new freewheeling diode operating phase, the first comparison circuit 10 compares the first sampled voltage SMP_GND and the second sampled voltage SMP_SW based on the most recently received count value, and outputs a signal OUT1 for controlling the operating state of the new freewheeling diode operating phase.

[0140] In some embodiments, the counting circuit 20 has a default count value, which corresponds to a default zero-crossing threshold. The default count value can be set based on experience or flexibly adjusted as needed, and this is not limited in the embodiments of the present application. The default count value is a count value between the maximum count value and the minimum count value allowed to be recorded by the counting circuit 20. For example, taking the count value in the counting circuit 20 as a 6-bit binary value as an example, the default count value can be 1000000.

[0141] After each clock cycle, that is, each time the freewheeling diode control signal NG switches from a high-level signal to a low-level signal, the counting circuit 20 performs an operation based on the comparison signal most recently output by the second comparison circuit 30 during the period when the freewheeling diode control signal NG was a high-level signal, to determine the adjustment direction of the first comparison circuit 10. For example, in the case where the count value and the corresponding zero-crossing threshold value are negatively correlated, an addition operation is performed when the most recently output comparison signal is a high-level signal, and a subtraction operation is performed when the most recently output comparison signal is a low-level signal.

[0142] In some embodiments, if the second comparison circuit 30 receives a reset signal, the count value is set to a reset count value. The reset count value is different from the normal count value. For example, taking the count value in the counting circuit 20 as a 6-bit binary value, the reset count value can be 64.

[0143] In some embodiments, adding the first count value means adding the first count value when the first count value is less than the maximum count value; subtracting the first count value means subtracting the first count value when the first count value is greater than the minimum count value. If the first count value is equal to the maximum count value when the first count value needs to be added, the first count value remains unchanged and the first count value is used as the second count value; if the first count value is equal to the minimum count value when the first count value needs to be subtracted, the first count value remains unchanged and the first count value is used as the second count value. The maximum count value and the minimum count value are respectively the maximum value and the minimum value that the counting circuit 20 can record. The maximum count value and the minimum count value can be set based on experience or flexibly adjusted according to needs. This embodiment of the present application does not limit this.

[0144] For example, taking the count value in the counting circuit 20 as a 6-bit binary value, the maximum count value may be 111111 (converted to decimal, 63), and the minimum count value may be 000000 (converted to binary, 0).

[0145] Exemplarily, the state of the freewheeling tube is controlled by the freewheeling tube control signal NG (the freewheeling tube is turned on when the freewheeling tube control signal NG is a high-level signal, and the freewheeling tube is turned off when the freewheeling tube control signal NG is a low-level signal); the second comparison circuit 30 outputs a high-level signal when the node voltage at the first node is less than the ground voltage, and outputs a low-level signal when the node voltage at the first node is greater than the ground voltage; the counting circuit 20 is a 6-bit digital counter, that is, the count value recorded by the counting circuit 20 is a 6-bit binary value; the count value and the zero-crossing threshold value corresponding to the count value are negatively correlated. In combination with the above situation, the working principle of the zero-crossing detection circuit provided in the embodiment of the present application is further explained.

[0146] When the freewheeling transistor control signal NG is high, the freewheeling transistor (N-type MOSFET) is turned on, the inductor current decreases, and the node voltage VSW of the first node decreases. The freewheeling transistor control signal NG and the node voltage VSW are simultaneously input to the second comparison circuit 30. When the freewheeling tube control signal NG is a high-level signal, the second comparison circuit 30 starts to operate. If the inductor current does not reverse, the node voltage VSW is a negative voltage, and the second comparison circuit 30 outputs a high-level signal. The high-level signal is input to the counting circuit 20, and the counting circuit 20 starts to perform an addition operation and outputs CNT5-CNT0. The code value CNT5-CNT0 changes from 100000 to 111111. From the formula Ith=[(1-CNT5)*32*I0+(1-CNT4)*16*I0+(1-CNT3)*8*I0+(1-CNT2)*4*I0+(1-CNT1)*2*I0+(1-CNT0)*I0]*R / Ron, it can be seen that the zero-crossing threshold Ith gradually decreases.

[0147] If the inductor current reverses direction, node voltage VSW becomes positive, and second comparator circuit 30 outputs a low-level signal. This low-level signal is input to counter circuit 20, which begins a subtraction operation and outputs CNT5-CNT0. The code value CNT5-CNT0 changes from 100000 to 000000, and the zero-crossing threshold Ith gradually increases. After multiple cycles, the inductor current zero-crossing threshold eventually stabilizes within a step range.

[0148] The second comparison circuit 30 detects the node voltage VSW during each high-level signal of the freewheeling tube control signal NG, and the counting circuit 20 changes once in each working cycle, so that the zero-crossing threshold Ith changes once in each working cycle, thereby achieving the purpose of successive approximation, making the zero-crossing detection circuit a successive approximation adaptive zero-crossing detection circuit applied to a buck circuit.

[0149] In addition, the use of a 6-bit binary counting value can achieve a 64-bit step of the zero-crossing threshold, which can make the zero-crossing threshold very small, greatly improving the accuracy of zero-crossing detection; at the same time, the reference resistor R is processed, using the same type of resistor as the freewheeling tube, and using a trimmed zero-temperature current, which greatly reduces the impact of temperature and process deviations on the zero-crossing threshold and further improves the accuracy.

[0150] The embodiments of the present application utilize an adaptive zero-crossing detection circuit that automatically adjusts the inductor current zero-crossing threshold according to different situations. This circuit is adaptable to different outputs and inductors, offering high flexibility and significantly improving light-load efficiency. Furthermore, the circuit is adaptable to power management chips with multiple inductors and multiple outputs, thus offering a wide range of applications. Furthermore, the circuit utilizes a successive approximation adaptive regulation method, resulting in high precision and flexibility. Improving the accuracy of zero-crossing detection helps reduce power loss and significantly improves light-load efficiency.

[0151] In an embodiment of the present application, the zero-crossing detection circuit includes a first comparison circuit and a counting circuit. The counting circuit can calculate an existing count value based on the inductor current at the end of the freewheeling tube working phase, so that the first comparison circuit controls the working state of the freewheeling tube working phase based on the zero-crossing threshold corresponding to the latest count value. The zero-crossing threshold based on which the working state of the freewheeling tube working phase is controlled is relatively flexible, thereby facilitating greater flexibility in controlling the working state of the freewheeling tube working phase.

[0152] In addition, the count value corresponding to the zero-crossing threshold is obtained by calculating the inductor current at the end of the freewheeling tube working phase, which is beneficial to improving the matching degree between the zero-crossing threshold and the actual situation, thereby improving the accuracy of controlling the working state of the freewheeling tube working phase.

[0153] The present application also provides a zero-crossing detection method, which can be applied to the zero-crossing detection circuit described in the above embodiment. Figure 9 The zero-crossing detection method includes the following steps 901 to 903.

[0154] Step 901: In response to a first inductor current of the buck circuit in the first freewheeling tube working stage being less than a first zero-crossing threshold corresponding to a first count value, output a first control signal, wherein the first control signal is used to control the first freewheeling tube working stage to end.

[0155] In one possible implementation, the third magnitude relationship is the same as the fourth magnitude relationship, the third magnitude relationship is the magnitude relationship between the first sampling voltage and the second sampling voltage, and the fourth magnitude relationship is the magnitude relationship between the first inductor current and the first zero-crossing threshold. The method further includes: in response to the first sampling voltage being less than the second sampling voltage, determining that the first inductor current is less than the first zero-crossing threshold.

[0156] In one possible implementation, the first sampling voltage is the product of a first reference current and a reference resistor; the second sampling voltage is the sum of a node voltage of the first node in the first freewheeling tube working stage and the first voltage; the first node is a node located between the freewheeling tube and the inductor in the buck circuit, and the node voltage is determined based on the first inductor current and the on-resistance of the freewheeling tube; the first voltage is the product of the target current and the reference resistor, the target current is the sum of the first reference current and the sampling current, and the product of the sampling current and the reference resistor is equal to the product of the first zero-crossing threshold and the on-resistance of the freewheeling tube.

[0157] In a possible implementation, the first count value is an N-bit binary value, the sampled current is the sum of sub-currents corresponding to each binary value in the N-bit binary value, and N is a positive integer.

[0158] In one possible implementation, the first size relationship is opposite to the second size relationship, the first size relationship is the size relationship between the first count value and the second count value, and the second size relationship is the size relationship between the first zero-crossing threshold value and the second zero-crossing threshold value; the sub-current corresponding to the i-th binary value in the N-bit binary value is the product of the second reference current and the coefficient corresponding to the i-th binary value; wherein, when the value of the i-th binary value is 1, the coefficient corresponding to the i-th binary value is 0; when the value of the i-th binary value is 0, the coefficient corresponding to the i-th binary value is 2 i , i is a positive integer not greater than N.

[0159] In a possible implementation, the reference resistor is the sum of on-resistances of at least one transistor, and the type of the at least one transistor is the same as that of the freewheeling diode.

[0160] In one possible implementation, the first reference current is a zero-temperature current.

[0161] Step 902: Calculate the first count value according to the first inductor current at the end of the first freewheeling diode working phase to obtain a second count value.

[0162] In one possible implementation, a first count value is calculated based on the first inductor current at the end of the first freewheeling tube working stage to obtain a second count value, including: in response to the first inductor current at the end of the first freewheeling tube working stage being greater than a standard zero-crossing threshold, a first operation is performed on the first count value to obtain a second count value; in response to the first inductor current at the end of the first freewheeling tube working stage being less than the standard zero-crossing threshold, a second operation is performed on the first count value to obtain a second count value; wherein the first operation is used to make the second zero-crossing threshold less than the first zero-crossing threshold; and the second operation is used to make the second zero-crossing threshold greater than the first zero-crossing threshold.

[0163] In one possible implementation, the method further includes: outputting a comparison signal based on a magnitude relationship between a node voltage of the first node in the first freewheeling tube working stage and a ground voltage, the first node being a node located between the freewheeling tube and the inductor in the buck circuit, the comparison signal being a first level signal or a second level signal, the first level signal being used to indicate that the node voltage is less than the ground voltage, and the second level signal being used to indicate that the node voltage is greater than the ground voltage; in response to the comparison signal most recently output before the end of the first freewheeling tube working stage being a first level signal, determining that the first inductor current at the end of the first freewheeling tube working stage is greater than a standard zero-crossing threshold; in response to the comparison signal most recently output before the end of the first freewheeling tube working stage being a second level signal, determining that the first inductor current at the end of the first freewheeling tube working stage is less than a standard zero-crossing threshold.

[0164] In one possible implementation, the first size relationship is opposite to the second size relationship, the first size relationship is the size relationship between the first count value and the second count value, and the second size relationship is the size relationship between the first zero-crossing threshold and the second zero-crossing threshold; the first operation includes an addition operation, and the second operation includes a subtraction operation.

[0165] Step 903: In response to the second inductor current of the buck circuit in the second freewheeling tube working stage being less than the second zero-crossing threshold corresponding to the second count value, a second control signal is output, where the second control signal is used to control the end of the second freewheeling tube working stage, and the second freewheeling tube working stage is the next freewheeling tube working stage after the end of the first freewheeling tube working stage.

[0166] The above description of the embodiment of the zero-crossing detection method has similar beneficial effects as the embodiment of the zero-crossing detection circuit. For technical details not disclosed in the embodiment of the zero-crossing detection method, please refer to the description of the embodiment of the zero-crossing detection circuit of this application for understanding.

[0167] See also Figure 10 In one embodiment, a power management chip is further provided. The power management chip includes a step-down circuit and a zero-crossing detection circuit according to any of the above possible implementations. The zero-crossing detection circuit is configured to detect zero crossings in the step-down circuit. Exemplarily, the step-down circuit and the zero-crossing detection circuit are two hardware modules in the power management chip. In some embodiments, the power management chip may also be referred to as a power supply chip.

[0168] See also Figure 11 In one embodiment, an electronic device is also provided, which includes the above-mentioned power management chip.

[0169] For example, the electronic device may be a display device including a display panel. For example, the electronic device may be any product or component with a display function, such as a smartphone, a tablet computer, a player, a laptop computer, a desktop computer, a flexible display device, a television, or a monitor.

[0170] It should be noted that the information (including but not limited to user device information, user personal information, etc.), data (including but not limited to data used for analysis, stored data, displayed data, etc.) and signals involved in this application are all authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with the relevant laws, regulations and standards of relevant countries and regions.

[0171] The terms "first," "second," and the like in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential sequence. It should be understood that the data used in this manner are interchangeable where appropriate so that the embodiments of the application described herein can be implemented in a sequence other than those illustrated or described herein. The embodiments described in the exemplary embodiments above do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application.

[0172] It should be understood that the term "plurality" used herein refers to two or more. "And / or" describes a relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone. The character " / " generally indicates an "or" relationship between the associated objects.

[0173] The above description is merely an exemplary embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A zero-crossing detection circuit, characterized in that: The zero-crossing detection circuit is applied to a step-down circuit, and the zero-crossing detection circuit includes a first comparison circuit and a counting circuit connected to each other; the first comparison circuit being configured to output a first control signal in response to a first inductor current of the buck circuit in the first freewheeling tube operating stage being less than a first zero-crossing threshold corresponding to a first count value currently recorded by the counting circuit, the first control signal being configured to control the first freewheeling tube operating stage to end; The counting circuit is configured to calculate the first count value according to the first inductor current at the end of the working phase of the first freewheeling transistor to obtain a second count value; The first comparison circuit is further configured to output a second control signal in response to the second inductor current of the step-down circuit in the second freewheeling tube working stage being less than a second zero-crossing threshold corresponding to the second count value, wherein the second control signal is configured to control the end of the second freewheeling tube working stage, and the second freewheeling tube working stage is the next freewheeling tube working stage after the end of the first freewheeling tube working stage.

2. The circuit according to claim 1, wherein: the counting circuit is configured to, in response to the first inductor current being greater than a standard zero-crossing threshold at the end of the first freewheeling diode operation phase, perform a first operation on the first count value to obtain the second count value; and, in response to the first inductor current being less than the standard zero-crossing threshold at the end of the first freewheeling diode operation phase, perform a second operation on the first count value to obtain the second count value; The first operation is used to make the second zero-crossing threshold smaller than the first zero-crossing threshold; and the second operation is used to make the second zero-crossing threshold larger than the first zero-crossing threshold.

3. The circuit according to claim 2, characterized in that The zero-crossing detection circuit further includes a second comparison circuit connected to the counting circuit; the second comparison circuit being configured to output a comparison signal based on a magnitude relationship between a node voltage at a first node and a ground voltage during an operation phase of the first freewheeling transistor, wherein the first node is a node between the freewheeling transistor and the inductor in the buck circuit, and the comparison signal is a first level signal or a second level signal, wherein the first level signal is configured to indicate that the node voltage is less than the ground voltage, and the second level signal is configured to indicate that the node voltage is greater than the ground voltage; The counting circuit is further configured to determine, in response to the comparison signal most recently output by the second comparison circuit before the end of the first freewheeling tube working stage being the first level signal, that the first inductor current at the end of the first freewheeling tube working stage is greater than the standard zero-crossing threshold; and to determine, in response to the comparison signal most recently output by the second comparison circuit before the end of the first freewheeling tube working stage being the second level signal, that the first inductor current at the end of the first freewheeling tube working stage is less than the standard zero-crossing threshold.

4. The circuit according to claim 2, characterized in that The first size relationship is opposite to the second size relationship, the first size relationship is the size relationship between the first count value and the second count value, and the second size relationship is the size relationship between the first zero-crossing threshold and the second zero-crossing threshold; the first operation includes an addition operation, and the second operation includes a subtraction operation.

5. The circuit according to any one of claims 1 to 4, characterized in that: The third magnitude relationship is the same as the fourth magnitude relationship, the third magnitude relationship is the magnitude relationship between the first sampling voltage and the second sampling voltage, and the fourth magnitude relationship is the magnitude relationship between the first inductor current and the first zero-crossing threshold; The first comparison circuit is further configured to determine that the first inductor current is less than the first zero-crossing threshold in response to the first sampling voltage being less than the second sampling voltage.

6. The circuit according to claim 5, characterized in that The first sampling voltage is the product of the first reference current and the reference resistance; The second sampling voltage is the sum of the node voltage of the first node in the working stage of the first freewheeling tube and the first voltage; the first node is a node located between the freewheeling tube and the inductor in the buck circuit, and the node voltage is determined based on the first inductor current and the on-resistance of the freewheeling tube; the first voltage is the product of the target current and the reference resistance, the target current is the sum of the first reference current and the sampling current, and the product of the sampling current and the reference resistance is equal to the product of the first zero-crossing threshold and the on-resistance of the freewheeling tube.

7. The circuit according to claim 6, characterized in that The first count value is an N-bit binary value, the sampling current is the sum of sub-currents corresponding to each binary value in the N-bit binary value, and N is a positive integer.

8. The circuit according to claim 7, characterized in that The first size relationship is opposite to the second size relationship, the first size relationship is the size relationship between the first count value and the second count value, and the second size relationship is the size relationship between the first zero-crossing threshold and the second zero-crossing threshold; The sub-current corresponding to the ith binary value in the N-bit binary value is the product of the second reference current and the coefficient corresponding to the ith binary value; wherein, when the value of the ith binary value is 1, the coefficient corresponding to the ith binary value is 0; when the value of the ith binary value is 0, the coefficient corresponding to the ith binary value is 2 i , i is a positive integer not greater than N.

9. The circuit according to any one of claims 6 to 8, characterized in that: The reference resistor is the sum of the on-resistances of at least one transistor, and the type of the at least one transistor is the same as that of the freewheeling transistor.

10. The circuit according to any one of claims 6 to 8, characterized in that: The first reference current is a zero temperature current.

11. A zero-crossing detection method, characterized in that: The method comprises: In response to the first inductor current of the buck circuit in the first freewheeling tube working stage being less than the first zero-crossing threshold corresponding to the first count value, the buck circuit outputs a first control signal, wherein the first control signal is used to control the first freewheeling tube working stage to end; performing calculation on the first count value according to the first inductor current at the end of the working phase of the first freewheeling transistor to obtain a second count value; In response to the second inductor current of the buck circuit in the second freewheeling tube working stage being less than the second zero-crossing threshold corresponding to the second count value, a second control signal is output, and the second control signal is used to control the end of the second freewheeling tube working stage. The second freewheeling tube working stage is the next freewheeling tube working stage after the end of the first freewheeling tube working stage.

12. A power management chip, characterized in that: The power management chip includes: a step-down circuit, and a zero-crossing detection circuit according to any one of claims 1 to 10.

13. An electronic device, characterized in that: The electronic device comprises: the power management chip as claimed in claim 12.

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