CN117458838A

CN117458838A - Zero-crossing detection circuit, zero-crossing detection method and power management chip

Info

Publication number: CN117458838A
Application number: CN202311427708.0A
Authority: CN
Inventors: 李垚; 呙顺乐; 苏新河; 黄敏光
Original assignee: Xiamen Yingmaikexin Integrated Technology Co ltd
Current assignee: Xiamen Yingmaikexin Integrated Technology Co ltd
Priority date: 2023-10-31
Filing date: 2023-10-31
Publication date: 2024-01-26

Abstract

The application provides a zero-crossing detection circuit, a zero-crossing detection method and a power management chip, wherein the zero-crossing detection circuit comprises an adjusting module, a comparator and a control module; the input end of the regulating module receives a load current signal, the first output end and the second output end of the regulating module are respectively connected with the in-phase input end and the opposite-phase input end of the comparator, the in-phase input end of the comparator is also connected with the switch node, the output end of the comparator is connected with the first input end of the control module, the second input end of the control module is connected with a power tube control signal, and the first output end and the second output end of the control module are respectively connected with the upper tube and the lower tube; the adjusting module adjusts the voltage of the in-phase and/or anti-phase input end of the comparator according to the load current signal; the comparator sends a turn-off signal to the control module when detecting zero crossing of the voltage at the switch node; the control module also controls the down tube to be turned off according to the turn-off signal and the power tube control signal. The zero-crossing detection circuit can ensure the triggering reliability of the zero-crossing detection module based on the load current signal.

Description

Zero-crossing detection circuit, zero-crossing detection method and power management chip

Technical Field

The present application relates to the field of switching circuits, and more particularly, to a zero-crossing detection circuit, a zero-crossing detection method, and a power management chip.

Background

The dc-dc conversion circuit may generally include an upper tube and a lower tube, and may be connected to other external devices (such as an inductor, a capacitor, and a resistor) to perform functions such as voltage boosting or voltage dropping. The connection point of the upper pipe and the lower pipe is a switch node. When the upper tube is opened and the lower tube is closed, the inductance current is increased; when the upper tube is turned off and the lower tube is turned on, the inductance current is reduced. When the conduction time of the lower tube is too long, the inductor current reversely flows, so that the capacitor discharges to the ground, and serious conduction loss is generated.

In the related art, a zero-crossing detection circuit is generally adopted, and when the voltage at the switch node is detected to be zero, the lower tube is controlled to be turned off, so that the problem of reverse backflow of the inductance current is avoided. However, the actual zero crossing point of the zero crossing detection circuit is easily affected by offset voltage, so that the zero crossing detection is triggered in advance in a heavy load state, and the zero crossing detection cannot be triggered in a light load or no load state, so that the detection reliability of the zero crossing detection circuit is low, and the conversion efficiency of the direct current-direct current conversion circuit is low.

Disclosure of Invention

In order to solve the above problems, the present application provides a zero-crossing detection circuit, a zero-crossing detection method, and a power management chip, where the zero-crossing detection circuit can improve the reliability of zero-crossing detection in heavy load, light load, or no-load states based on load current, thereby improving the conversion efficiency of a dc-dc conversion circuit.

In a first aspect, the present application provides a zero-crossing detection circuit, where the dc-dc conversion circuit includes an inductor, an upper tube and a lower tube, and a connection point between a source electrode of the upper tube and a drain electrode of the lower tube is a switching node, and the zero-crossing detection circuit includes an adjusting module, a comparator and a control module; the input end of the regulating module is used for receiving a load current signal, the first output end of the regulating module is connected with the in-phase input end of the comparator, the second output end of the regulating module is connected with the reverse-phase input end of the comparator, the in-phase input end of the comparator is also connected with the switch node, the output end of the comparator is connected with the first input end of the control module, the second input end of the control module is used for accessing a power tube control signal, the first output end of the control module is connected with the upper tube, and the second output end of the control module is connected with the lower tube; the adjusting module is used for adjusting the voltage of the non-inverting input end and/or the inverting input end of the comparator according to the load current signal; the comparator is used for sending a turn-off signal to the control module when the voltage at the switch node is detected to be zero crossing; the control module is also used for controlling the lower tube to be turned off according to the turn-off signal and the power tube control signal.

Based on the zero-crossing detection circuit provided by the embodiment of the application, the voltage at the switching point can be detected in real time through the comparator, so that when the voltage zero crossing at the switching node is detected, a turn-off signal is sent to the control module to turn off the lower tube, and the problem of reverse backflow of the inductance current is avoided. And the regulating module can regulate the voltage of the non-inverting input end and/or the inverting input end of the comparator based on the load current signal so as to avoid the influence of offset voltage on the comparator, thereby causing the problem of weaker triggering reliability of the comparator, namely, the zero-crossing detection circuit provided by the application can improve the reliability of zero-crossing detection under heavy load, light load or no-load states based on the load current, thereby ensuring the synchronous rectification effect and further improving the conversion efficiency and the use reliability of the direct-current-direct-current conversion circuit applying the zero-crossing detection circuit.

In one possible design, the adjusting module is configured to increase the voltage of the inverting input terminal of the comparator when the sampling voltage corresponding to the load current signal is greater than the reference voltage; when the sampling voltage corresponding to the load current signal is smaller than the reference voltage, the adjusting module is used for increasing the voltage of the non-inverting input end of the comparator.

Based on the above-mentioned optional mode, can increase the voltage of the inverting input end of comparator through the regulating module under the heavy load state for the comparator can compare the voltage after increasing with the voltage of switch node department, thereby carries out accurate detection to the zero crossing state of switch node department voltage, has avoided receiving the offset voltage influence under the heavy load state, leads to crossing the problem of comparator output turn-off signal to control module in advance. The voltage of the non-inverting input end of the comparator can be increased through the adjusting module in the no-load or light-load state, so that the comparator can compare the increased voltage with the voltage of the inverting input end, and the problem that the comparator cannot output a turn-off signal to the control module due to the influence of offset voltage in the no-load or light-load state is avoided. Therefore, the voltage of the non-inverting input end and the voltage of the inverting input end of the comparator can be adjusted, the reliability of zero-crossing detection under heavy load, light load or no-load conditions can be improved, the detection accuracy and the triggering reliability of the comparator are ensured, and the synchronous rectification effect of the upper pipe and the lower pipe is further ensured.

In one possible embodiment, the regulation module comprises a first current source, a first resistor, a second resistor, a first switching tube and a second switching tube; one end of the first resistor is connected with the switch node, and the other end of the first resistor is connected with the non-inverting input end of the comparator; one end of the second resistor is grounded, and the other end of the second resistor is connected with the inverting input end of the comparator; the controlled end of the first switching tube is used for accessing reference voltage, the first pole of the first switching tube is connected with the first current source, and the second pole of the first switching tube is connected with the inverting input end of the comparator; the controlled end of the second switching tube is used for accessing the sampling voltage corresponding to the load current signal, the first pole of the second switching tube is connected with the first current source, and the second pole of the second switching tube is connected with the non-inverting input end of the comparator.

Based on the above alternative, when the sampling voltage corresponding to the load current signal is smaller than the reference voltage, the first switching tube is turned off, and the second switching tube is turned on, at this time, the voltage input by the non-inverting input end of the comparator is the voltage of the switching node, the product voltage of the first current source and the first resistor is superimposed, at this time, the voltage of the non-inverting input end is increased, the increased voltage is compared with the ground voltage of the inverting input end, and when the voltage of the non-inverting input end is greater than the ground voltage of the inverting input end, the comparator is turned over to output the turn-off signal to the control module. Therefore, the problem that the turn-off signal cannot be timely output under the light load condition is avoided, and the triggering reliability of the comparator is ensured. When the reference voltage corresponding to the load current signal is larger than the reference voltage, the first switch tube is turned on, the second switch tube is turned off, at the moment, the voltage input by the inverting input end of the comparator is the ground voltage, the product voltage of the first current source and the second resistor is superposed, the voltage is compared with the voltage of the switch node of the non-inverting input end, and only after the voltage of the switch node is larger than the voltage, the comparator can be turned over to output a turn-off signal to the control module. The problem that the turn-off signal can be output in advance under the condition of heavy load is avoided, and the triggering reliability of the comparator is ensured. Therefore, the regulating module can regulate the voltages of the non-inverting input end and the inverting input end of the comparator based on the load current signal so as to improve the reliability of zero-crossing detection of the comparator in heavy load, light load or no-load states, and further improve the conversion efficiency and the use reliability of a direct current-direct current conversion circuit applying the zero-crossing detection circuit.

In one possible design, the adjusting module is configured to reduce the voltage at the non-inverting input terminal of the comparator when the sampling voltage corresponding to the load current signal is greater than the reference voltage; when the sampling voltage corresponding to the load current signal is smaller than the reference voltage, the regulating module is also used for increasing the voltage of the non-inverting input end of the comparator.

Based on the above optional mode, the adjusting module can adjust the voltage of the non-inverting input end of the comparator based on the load current signal, so as to improve the reliability of zero-crossing detection of the comparator in heavy load, light load or no-load states, further ensure the synchronous rectification effect of the upper tube and the lower tube, and improve the conversion efficiency and the use reliability of the direct current-direct current conversion circuit applying the zero-crossing detection circuit.

In one possible embodiment, the regulation module comprises a second current source, a third resistor, a third switching tube, a fourth switching tube and a third current source; one end of the third resistor is connected with the switch node, and the other end of the third resistor is connected with the non-inverting input end of the comparator; the controlled end of the third switching tube is used for accessing reference voltage, the first pole of the third switching tube is connected with the second current source, and the second pole of the third switching tube is grounded; the controlled end of the fourth switching tube is used for accessing the sampling voltage corresponding to the load current signal, the first pole of the fourth switching tube is connected with the second current source, and the second pole of the fourth switching tube is connected with the non-inverting input end of the comparator; one end of the third current source is respectively connected with the other end of the third resistor, the non-inverting input end of the comparator and the second pole of the fourth switching tube, and the other end of the third current source is grounded; the current flowing through the second current source is greater than the current of the third current source.

Based on the above alternative mode, when the sampling voltage corresponding to the load current signal is smaller than the reference voltage, the voltage of the non-inverting input end of the comparator can be increased, that is, the voltage input by the non-inverting input end of the comparator is the product voltage of the current difference between the second current source and the third resistor, and then the increased voltage is compared with the grounding voltage of the inverting input end, when the voltage of the non-inverting input end is greater than the grounding voltage of the inverting input end, the comparator can be turned over to output a turn-off signal to the control module, so that the turning-over of the comparator is advanced, the problem that the turn-off signal cannot be timely output under no-load or light-load conditions is avoided, and the triggering reliability of the comparator is ensured. When the voltage of the non-inverting input end is larger than the ground voltage of the inverting input end, the comparator can overturn to output a turn-off signal to the control module, the overturn of the comparator is delayed, the problem that the turn-off signal is output in advance under the heavy load condition is avoided, and the triggering reliability of the comparator is ensured.

In one possible design, the zero-crossing detection circuit further includes a sampling module; the input end of the sampling module is used for receiving the load current signal, the output end of the sampling module is connected with the input end of the adjusting module, and the sampling module is used for converting the load current signal into sampling voltage and outputting the sampling voltage to the adjusting module.

Based on the above optional manner, the reliability of the sampling voltage corresponding to the load current signal received by the adjusting module can be ensured by the sampling module.

In a second aspect, the present application provides a zero-crossing detection method, including the zero-crossing detection circuit according to any one of the optional modes of the first aspect, where the method includes: the adjusting module acquires a load current signal and adjusts the voltage of the non-inverting input end and/or the inverting input end of the comparator according to the load current signal; the comparator sends a turn-off signal to the control module when detecting zero crossing of the voltage at the switch node; the control module controls the down tube to be turned off according to the turn-off signal and the input power tube control signal.

In one possible embodiment, the voltage at the non-inverting input and/or the inverting input of the comparator is adjusted as a function of the load current signal, comprising: when the sampling voltage corresponding to the load current signal is larger than the reference voltage, the regulating module increases the voltage of the inverting input end of the comparator; when the sampling voltage corresponding to the load current signal is smaller than the reference voltage, the regulating module increases the voltage of the non-inverting input end of the comparator.

Based on the above optional manner, the adjusting module can adjust the voltages of the in-phase input end and the anti-phase input end of the comparator based on the load current signal, so as to improve the reliability of the zero-crossing detection of the comparator in heavy load, light load or no load states, and further improve the conversion efficiency and the use reliability of the direct current-direct current conversion circuit applying the zero-crossing detection circuit.

In one possible embodiment, the voltage at the non-inverting input and/or the inverting input of the comparator is adjusted as a function of the load current signal, comprising: when the sampling voltage corresponding to the load current signal is larger than the reference voltage, the regulating module reduces the voltage of the non-inverting input end of the comparator; when the sampling voltage corresponding to the load current signal is smaller than the reference voltage, the regulating module increases the voltage of the non-inverting input end of the comparator.

Based on the above optional manner, the adjusting module can adjust the voltage of the non-inverting input end of the comparator based on the load current signal, so as to improve the reliability of zero-crossing detection of the comparator in heavy load, light load or no-load states, and further improve the conversion efficiency and the use reliability of the direct current-direct current conversion circuit applying the zero-crossing detection circuit.

In a third aspect, the present application provides a power management chip, including the zero-crossing detection circuit and the dc-dc conversion circuit according to any one of the optional modes of the first aspect.

Drawings

Fig. 1 is a schematic diagram of a dc-dc conversion circuit in the related art;

FIG. 2 is a schematic diagram of a driving circuit of a DC-DC conversion circuit in the related art;

FIG. 3 is a statistical chart of preset flip fold lines provided in an embodiment of the present application;

fig. 4 is a graph of flip broken line statistics when offset voltage provided in the embodiment of the present application is negative;

fig. 5 is a flip broken line statistical chart when offset voltage provided in the embodiment of the present application is a positive value;

fig. 6 is a schematic diagram of a structure of a zero-crossing detection circuit provided in an embodiment of the present application;

fig. 7 is a schematic diagram ii of a zero-crossing detection circuit according to an embodiment of the present application;

FIG. 8 is a schematic diagram of an exemplary structure of a zero-crossing detection circuit in the zero-crossing detection circuit according to an embodiment of the present application;

fig. 9 is a second schematic structural diagram of an exemplary zero-crossing detection circuit in the zero-crossing detection circuit according to the embodiment of the present application;

fig. 10 is a schematic diagram III of a structure of a zero-crossing detection circuit provided in an embodiment of the present application;

fig. 11 is a flowchart of a zero-crossing detection method provided in an embodiment of the present application.

Wherein, each reference sign in the figure:

100. a DC-DC conversion circuit;

200. a zero crossing detection system;

300. a driving circuit;

400. A zero-crossing detection circuit; 410. a control module; 420. an adjustment module; 430. a sampling module;

q1, upper tube; q2, lower tube; D. a parasitic diode; C. a capacitor; l, inductance; r1, a first resistor; r2, a second resistor; r3, a third resistor; r4, a fourth resistor; SW, switch node; IOUT, load current signal; VOUT, output voltage; vos, offset voltage; VIN, input voltage; COMP, comparator; q3, a first switching tube; q4, a second switching tube; q5, a third switching tube; q6, a fourth switching tube; -V1, a first voltage; v1, a second voltage; i1, light load; and I2, heavy load.

Detailed Description

In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system configurations, techniques, etc. in order to provide a thorough understanding of the embodiments of the present application. It will be apparent, however, to one skilled in the art that the present application may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, and circuits are omitted so as not to obscure the description of the present application with unnecessary detail.

Dc-dc conversion circuits are widely used in various circuits as boost and buck converters, and referring to fig. 1, a conventional dc-dc conversion circuit 100 may generally include: a capacitor (C shown in FIG. 1), an upper tube (Q1 shown in FIG. 1), a lower tube (Q2 shown in FIG. 1), an inductor (L shown in FIG. 1), and a fourth resistor (R4 shown in FIG. 1). The IOUT is a load current signal, the first pole of the upper tube Q1 is configured to receive an input voltage (VIN shown in fig. 1), the second pole of the upper tube Q1 is connected to one end of the inductor L and the first pole of the lower tube Q2, the connection point of the upper tube Q1 and the lower tube Q2 is a switch node (SW shown in fig. 1), the second pole of the lower tube Q2 is grounded, and the other end of the inductor L is connected to one end of the capacitor C and one end of the fourth resistor R4 and is configured to output an output voltage (VOUT shown in fig. 1), where it is worth explaining that the inductor L may collect peak current of the upper tube Q1 and valley current of the lower tube Q2. The other end of the capacitor C and the other end of the fourth resistor R4 are grounded. The upper tube Q1 and the lower tube Q2 are used for switching on and off current, the inductor L is used for converting electric energy into magnetic energy to be stored, meanwhile, the magnetic energy can be converted into electric energy to be released again, and the capacitor C is used for charging and discharging. Illustratively, the upper tube Q1 is turned on, the lower tube Q2 is turned off, the input voltage VIN is input, when the off time is up, the upper tube Q1 is turned off, the lower tube Q2 is turned on, the voltage across the inductor L is inverted and discharged, when the current of the inductor L is less than the reference signal, the upper tube Q1 is turned on, the lower tube Q2 is turned off, and the inductor L is charged, thus cyclically.

Here, it should be noted that the upper tube Q1 and the lower tube Q2 may be metal oxide semiconductor (Metal Oxide Semiconductor, MOS) field effect transistors, where a parasitic diode (as shown in fig. 1D) is present in the lower tube Q2, the upper tube Q1 is turned off, the lower tube Q2 is turned on, and in the process of inverting and discharging the voltage across the inductor L, the inductor L current flows through the lower tube Q2, that is, the lower tube Q2 is a rectifier, and at this time, the upper tube Q1 and the lower tube Q2 are MOS field effect transistors with extremely low on-state resistance, so the conversion efficiency of synchronous rectification is higher.

When the upper tube Q1 is turned off and the lower tube Q2 is turned on, the current of the inductor L flows to the fourth resistor R4, however, the current discharge of the inductor L gradually decreases, and in the forced current continuous mode (FCCM, forced Current Continuous Mode), during the freewheeling process of the lower tube Q2, the current of the inductor L flows in opposite phase, and at this time, the lower tube Q2 is not turned off, and the current of the inductor L flows in opposite phase, so that the capacitor C discharges to the ground, thereby generating serious conduction loss.

As shown in fig. 2, in the related art, a zero-crossing detection system 200 and a driving circuit 300 are generally provided, the driving circuit 300 is used for controlling on-off of an upper tube Q1 and a lower tube Q2, a first input end of the zero-crossing detection system 200 is respectively connected with a second pole of the upper tube Q1 and a first pole of the lower tube Q2, that is, connected with a switching node SW, for accessing a voltage at the switching node SW, and a second input end of the zero-crossing detection system 200 is grounded. The zero-crossing detection system 200 compares the voltage at the switch node SW with a 0V (volt) ground voltage to obtain a zero-crossing turn-off signal, when the voltage at the switch node SW is zero-crossing, the current freewheels of the inductor L and also crosses the zero point, and at this time, the zero-crossing detection system 200 sends the zero-crossing turn-off signal to the driving circuit 300, so that the driving circuit 300 controls the down tube Q2 to turn off, and the problem of reverse backflow of the current of the inductor L is avoided.

However, the actual zero crossing of the zero crossing detection system 200 is susceptible to offset voltage (Vos as shown in fig. 2), and, for example, assuming that the on-resistance of the lower tube Q2 is 5mΩ (milliohms), the current range corresponding to the zero crossing detection system 200 is + -2A (amperes) when the offset voltage Vos is + -10mV (millivolts), so that the current error range is too large, resulting in weaker detection and triggering reliability of the zero crossing detection system 200. For example, as shown in fig. 3, in the light load (I1 shown in fig. 3), the voltage at the switch node SW of the zero-crossing detection system 200 is the first voltage (V1 shown in fig. 3), and the zero-crossing detection system 200 is turned over; in the heavy load (I2 shown in fig. 3), the voltage at the switch node SW of the zero-crossing detection system 200 is the second voltage (V1 shown in fig. 3), and the zero-crossing detection system 200 is flipped. However, the zero-crossing detection system 200 cannot normally flip at the first voltage-V1 or the second voltage V1 due to the offset voltage Vos.

When the offset voltage Vos is negative, as shown in fig. 4, the voltage at the switch node SW of the zero-crossing detection system 200 is the sum of the second voltage V1 and the offset voltage Vos and is smaller than the second voltage V1 in the heavy load I2 state because the offset voltage Vos exists at the moment, so that the zero-crossing detection system 200 outputs a zero-crossing turn-off signal to the zero-crossing detection circuit 300 in advance, so that the zero-crossing detection circuit 300 turns off the lower tube Q2, and the zero-crossing detection system 200 has lower triggering reliability and reduces the synchronous rectification effect. When the offset voltage Vos is positive, as shown in fig. 5, because the offset voltage Vos exists at this time, in the light load I1 state, the voltage at the switch node SW of the zero-crossing detection system 200 is the sum of the first voltage-V1 and the offset voltage Vos and is always greater than the second voltage-V1, so that the zero-crossing detection system 200 cannot detect the zero crossing of the voltage at the switch node SW, and cannot output a zero turn-off signal to the zero-crossing detection circuit 300 all the time, the on time of the lower tube Q2 is prolonged, and the triggering reliability of the zero-crossing detection system 200 is lower, that is, the reliability of avoiding the current backflow is lower.

For this reason, the present application provides a zero-crossing detection circuit, a zero-crossing detection method, and a power management chip applied to the dc-dc conversion circuit 100, which can ensure the reliability of zero-crossing detection in heavy load, light load, or no-load states based on the load current signal IOUT, so as to ensure the control reliability of the zero-crossing detection circuit.

Exemplary descriptions of the zero-crossing detection circuit, the zero-crossing detection method and the power management chip development provided in the present application are provided below in conjunction with the accompanying drawings.

As shown in fig. 6, the zero-crossing detection circuit 400 provided in the present application includes a control module 410 and a comparator (COMP shown in fig. 6), wherein a second input end of the control module 410 is used for accessing a power tube control signal (PWM shown in fig. 6), a first output end of the control module 410 is connected with an upper tube Q1, a second output end of the control module 410 is connected with a lower tube Q2, the control module 410 can control the on-off of the upper tube Q1 and the lower tube Q2 periodically according to the power tube control signal PWM, however, the control module 410 can only control the on-off of the upper tube Q1 and the lower tube Q2 according to a preset period, the magnitude of the inductor L current cannot be identified, and when the on-time of the lower tube Q2 is too long, a problem of the inductor L current reverse flow exists.

Alternatively, the control module 410 may be a pulse width modulation (Pulse Width Modulation, PWM) chip, or may be another control chip, which is not specifically limited in this application.

The non-inverting input end (as shown in "+" in fig. 6) of the comparator COMP is connected to the switch node SW, that is, the non-inverting input end is connected to the voltage at the switch node SW, the inverting input end (as shown in "-" in fig. 6) of the comparator COMP is used for receiving the sampled voltage corresponding to the load current signal, the output end of the comparator COMP is connected to the first input end of the control module 410, the comparator COMP compares the sampled voltage corresponding to the load current signal IOUT with the voltage at the switch node SW to determine that the voltage at the switch node SW is zero crossing, and when the voltage at the switch node SW of the dc-dc conversion circuit 100 is detected to be zero crossing, the comparator COMP sends a turn-off signal to the control module 410, so that the control module 410 can control the turn-off of the down tube Q2 based on the turn-off signal, so as to avoid the problem that the turn-on time of the down tube Q2 is too long, the inductor L current reversely flows, and serious turn-on loss occurs. In this way, the comparator COMP provided in the embodiment of the present application compares the voltage at the switch node SW with the sampling voltage corresponding to the load current signal IOUT, and the inverting input end of the comparator COMP is used as the reference end, where the voltage can be changed along with the change of the load current signal IOUT, so that the problem of low triggering reliability of the comparator COMP under heavy load, light load or no-load conditions is avoided, and the synchronous rectification effect of the upper tube Q1 and the lower tube Q2 is ensured.

In order to ensure that the sampling voltage corresponding to the load current signal IOUT, which is accessed by the comparator COMP, can be changed based on the offset voltage Vos change in the dc-dc conversion circuit 100, thereby ensuring the reliability and the precision of the load current signal IOUT, and further ensuring the detection and the triggering reliability of the comparator COMP, as shown in fig. 7, in an example, the zero-crossing detection circuit 400 provided in the embodiment of the present application may further be provided with an adjusting module 420, an input end of the adjusting module 420 is used for receiving the load current signal IOUT, a first output end of the adjusting module 420 is connected with an in-phase input end of the comparator COMP, a second output end of the adjusting module 420 is connected with an out-phase input end of the comparator COMP, and the adjusting module 420 is used for detecting the load current signal IOUT of the dc-dc conversion circuit 100 and adjusting the voltage of the in-phase input end and/or the out-phase input end of the comparator COMP according to the load current signal IOUT.

An exemplary description will be given below of both cases where offset voltage Vos is negative and positive.

First kind: the offset voltage Vos is negative.

The adjusting module 420 detects the load current signal IOUT, and when the sampled voltage corresponding to the load current signal IOUT is detected to be greater than the reference voltage, it should be noted that a reference voltage is provided in the adjusting module 420, and when the sampled voltage corresponding to the load current signal IOUT is equal to the reference voltage, the load current signal IOUT is represented to be stable, and the adjusting module 420 may directly output the sampled voltage of the stable load current signal IOUT to the comparator COMP. When the sampling voltage corresponding to the load current signal IOUT is greater than the reference voltage, which represents that the dc-dc conversion circuit 100 is in a heavy load state, the voltage at the switch node SW is not zero-crossing yet, and at this time, the comparator COMP may determine that the voltage at the switch node SW is zero-crossing based on the offset voltage Vos, and output the turn-off signal to the control module 410 in advance.

In order to avoid the problem that the turn-off signal is output to the control module 410 in advance under the heavy load state, that is, the zero-crossing detection is triggered in advance, the voltage of the inverting input end of the comparator COMP can be increased, so that the voltage of the inverting input end of the comparator COMP is increased through the adjusting module 420, the increased voltage can be compared with the switch voltage SW by the comparator COMP, the zero-crossing state of the voltage at the switch node SW is accurately detected, the problem that the turn-off signal is output to the control module 410 in advance due to the influence of the offset voltage Vos under the heavy load state is avoided, the detection accuracy and the triggering reliability of the comparator COMP are guaranteed, and the synchronous rectification effect of the upper pipe Q1 and the lower pipe Q2 is further guaranteed. Here, it should be noted that the increased sampling voltage corresponding to the load current signal IOUT needs to be greater than or equal to a preset maximum voltage value, where the preset maximum voltage value refers to a maximum value of the offset voltage Vos, so as to ensure the accuracy of voltage adjustment, thereby ensuring the reliability of the voltage received by the comparator COMP, and ensuring the triggering reliability of the comparator COMP.

Optionally, the adjusting module 420 may further reduce the voltage of the non-inverting input terminal of the comparator COMP to avoid the problem that the comparator COMP outputs the off signal to the control module 410 in advance due to the offset voltage Vos in the heavy load state. Here, it should be noted that the voltage at the non-inverting input terminal of the comparator COMP can be adjusted based on different adjusting modules 420, so as to avoid the problem of triggering the zero crossing detection in advance in the heavy load state. For example, the trigger reliability of the comparator COMP can be ensured by adjusting the voltages of the non-inverting input terminal and the inverting input terminal of the comparator COMP at the same time; the triggering reliability of the comparator COMP is ensured by adjusting the voltage of the non-inverting input terminal of the comparator COMP alone, or by adjusting the voltage of the inverting input terminal of the comparator COMP alone, without specific limitation.

Second kind: the offset voltage Vos is a positive value.

The adjusting module 420 detects the load current signal IOUT, when the sampling voltage corresponding to the load current signal IOUT is detected to be smaller than the reference voltage, the dc-dc converting circuit 100 is in an idle or light load state, and the voltage at the switch node SW is zero-crossing, at this time, the comparator COMP may determine that the voltage at the switch node SW is not zero-crossing all the time based on the offset voltage Vos due to the offset voltage Vos, so that the down tube Q2 is continuously turned on, thereby causing a current backflow problem.

In order to avoid the problem that no turn-off signal can be output to the control module 410 in the no-load or light-load state, that is, zero-crossing detection can not be triggered, optionally, the voltage of the non-inverting input end of the comparator COMP can be increased, so that the voltage of the non-inverting input end of the comparator COMP is increased through the adjusting module 420, the increased voltage can be compared with the voltage of the inverting input end of the comparator COMP, thereby accurately detecting the zero-crossing state of the voltage at the switch node SW, avoiding the problem that the comparator COMP can not timely send the turn-off signal to the control module 410 due to the influence of offset voltage Vos in the no-load or light-load state, and further ensuring the detection accuracy and the triggering reliability of the comparator COMP and further ensuring the synchronous rectification effect of the upper pipe Q1 and the lower pipe Q2.

Optionally, the adjusting module 420 may further reduce the voltage of the inverting input terminal of the comparator COMP to avoid the problem that the comparator COMP cannot timely send the turn-off signal to the control module 410 due to the offset voltage Vos in the no-load or light-load state. Here, it should be noted that, the voltage at the non-inverting input terminal of the comparator COMP may be adjusted based on the different adjusting modules 420, so as to avoid the problem that the zero-crossing detection cannot be triggered in the no-load or light-load state, which is not limited specifically. For example, the trigger reliability of the comparator COMP can be ensured by adjusting the voltages of the non-inverting input terminal and the inverting input terminal of the comparator COMP at the same time; the triggering reliability of the comparator COMP is ensured by adjusting the voltage of the non-inverting input terminal of the comparator COMP alone, or by adjusting the voltage of the inverting input terminal of the comparator COMP alone, without specific limitation.

In this way, the zero-crossing detection circuit 400 provided in the embodiment of the present application can detect the voltage at the switch node SW in real time by providing the comparator COMP, so as to send a turn-off signal to the control module 410 when detecting that the voltage at the switch node SW is zero-crossing, so as to turn off the down tube Q2, thereby avoiding the problem of reverse current backflow of the inductor L. Moreover, the adjusting module 420 can adjust the voltage of the non-inverting input end and/or the inverting input end of the comparator COMP based on the load current signal IOUT, so as to avoid the problem that the triggering reliability of the comparator COMP is weaker due to the influence of the offset voltage Vos.

In an example, taking the voltage of the non-inverting input terminal and the inverting input terminal of the comparator COMP being adjusted at the same time, and further guaranteeing the triggering reliability of the comparator COMP, as shown in fig. 8, the adjusting module 420 may include a first current source (ISS 1 shown in fig. 8), a first resistor (R1 shown in fig. 8), a second resistor (R2 shown in fig. 8), a first switching tube (Q3 shown in fig. 8) and a second switching tube (Q4 shown in fig. 8), where one end of the first resistor R1 is connected to the switching node SW for accessing the voltage of the switching node SW, the other end of the first resistor R1 is connected to the non-inverting input terminal of the comparator COMP, one end of the second resistor R2 is grounded, and the other end of the second resistor R2 is connected to the inverting input terminal of the comparator COMP. The controlled end of the first switching tube Q3 is used for accessing a reference voltage, the first pole of the first switching tube Q3 is connected with the first current source ISS1, the second pole of the first switching tube Q3 is connected with the inverting input end of the comparator COMP, the controlled end of the second switching tube Q4 is used for accessing a sampling voltage corresponding to the load current signal IOUT, the first pole of the second switching tube Q4 is connected with the first current source ISS1, and the second pole of the second switching tube Q4 is connected with the non-inverting input end of the comparator COMP.

When the sampling voltage corresponding to the load current signal IOUT is smaller than the reference voltage, the first switching tube Q3 is turned off, and the second switching tube Q4 is turned on, at this time, the voltage input by the non-inverting input end of the comparator COMP is the multiplied voltage of the first current source ISS1 and the first resistor R1 superimposed on the voltage of the switching node SW, at this time, the voltage of the non-inverting input end is increased, the increased voltage is compared with the ground voltage of the inverting input end, and when the voltage of the non-inverting input end is greater than the ground voltage of the inverting input end, the comparator COMP is turned over to output the turn-off signal to the control module 410. Therefore, the problem that the turn-off signal cannot be timely output under the light load condition is avoided, and the triggering reliability of the comparator COMP is ensured. When the reference voltage corresponding to the load current signal IOUT is greater than the reference voltage, the first switching tube Q3 is turned on, and the second switching tube Q4 is turned off, and at this time, the voltage input by the inverting input terminal of the comparator COMP is the ground voltage, the product voltage of the first current source ISS1 and the second resistor R2 is superimposed, and then the voltage is compared with the voltage of the switching node SW of the non-inverting input terminal, and only after the voltage of the switching node SW is greater than the voltage, the comparator COMP is turned over to output the turn-off signal to the control module 410. The problem that the turn-off signal is output in advance under the condition of heavy load is avoided, and the triggering reliability of the comparator COMP is ensured. In this way, the adjusting module 420 can adjust the voltages of the non-inverting input terminal and the inverting input terminal of the comparator COMP based on the load current signal IOUT, so as to improve the reliability of the zero-crossing detection of the comparator COMP in the heavy load, light load or no load state, and further improve the conversion efficiency and the use reliability of the dc-dc conversion circuit 100 applying the zero-crossing detection circuit 400.

Optionally, in order to ensure adjustment reliability, the resistances of the first resistor R1 and the second resistor R2 are the same and adjustable.

In another example, taking only the voltage of the non-inverting input terminal of the comparator COMP to further ensure the triggering reliability of the comparator COMP as shown in fig. 9, the adjusting module 420 may include a second current source (ISS 2 shown in fig. 9), a third resistor (R3 shown in fig. 9), a third switching tube (Q5 shown in fig. 9), a fourth switching tube (Q6 shown in fig. 9) and a third current source (ISS 3 shown in fig. 9), one end of the third resistor R3 is connected to the switching node SW for accessing the voltage at the switching node SW, the other end of the third resistor R3 is connected to the non-inverting input terminal of the comparator COMP, the controlled end of the third switching tube Q5 is used for accessing the reference voltage, the first electrode of the third switching tube Q5 is connected to the second current source ISS2, the second electrode of the third switching tube Q5 is grounded, the controlled end of the fourth switching tube Q6 is used for accessing the sampling voltage corresponding to the load current signal IOUT, the first electrode of the fourth switching tube Q6 is connected to the second current source ISS2, the other end of the fourth switching tube Q6 is connected to the non-inverting input terminal of the fourth switching tube Q6 is connected to the other end of the comparator COMP, and the other end of the third switching tube Q3 is connected to the non-inverting input terminal of the comparator COMP is connected to the other end of the input terminal of the third switching tube 3.

When the sampled voltage corresponding to the load current signal IOUT is smaller than the reference voltage, the voltage at the non-inverting input terminal of the comparator COMP may be increased, and the voltage input at the non-inverting input terminal of the comparator COMP is exemplified to be the product voltage of the voltage difference between the current of the second current source ISS1 and the current of the third current source ISS3 and the third resistor R3 superimposed on the voltage at the switch node SW, where it is worth noting that the voltage at the non-inverting input terminal needs to be increased at this time, therefore, the current of the second current source ISS1 needs to be set to be greater than the current of the third current source ISS3, so that the problem that the voltage at the non-inverting input terminal decreases due to the fact that the current of the second current source ISS1 decreases by the third current source ISS3 gives a negative value is avoided. At this time, the voltage of the non-inverting input terminal increases, and then the increased voltage is compared with the ground voltage of the inverting input terminal, and when the voltage of the non-inverting input terminal is greater than the ground voltage of the inverting input terminal, the comparator COMP turns over to output the turn-off signal to the control module 410. Therefore, the overturn of the comparator COMP is advanced, the problem that the turn-off signal cannot be timely output under the condition of no load or light load is avoided, and the triggering reliability of the comparator COMP is ensured.

When the reference voltage corresponding to the load current signal IOUT is greater than the reference voltage, the voltage at the non-inverting input terminal of the comparator COMP may be reduced, and the voltage input at the non-inverting input terminal of the comparator COMP is, for example, the voltage at the switch node SW minus the product voltage of the third current source ISS3 and the third resistor R3, and then the reduced voltage is compared with the ground voltage at the inverting input terminal, and when the voltage at the non-inverting input terminal is greater than the ground voltage at the inverting input terminal, the comparator COMP is turned over to output the turn-off signal to the control module 410. Therefore, the overturn of the comparator COMP is delayed, the problem that the turn-off signal is output in advance under the condition of heavy load is avoided, and the triggering reliability of the comparator COMP is ensured.

Here, it should be noted that, in this example, in order to increase or decrease the voltage uniformity of the non-inverting input terminal of the comparator COMP in the no-load, light-load or heavy-load state, the current of the second current source ISS2 may be twice that of the third current source ISS3, so in the no-load or light-load state, it may be understood that the voltage of the non-inverting input terminal of the comparator COMP increases by the product voltage of the third current source ISS3 and the third resistor R3, and in the heavy-load state, the voltage of the non-inverting input terminal of the comparator COMP subtracts by the product voltage of the third current source ISS3 and the third resistor R3, so that the non-inverting input terminal of the comparator COMP increases or decreases the voltage uniformity in the no-load, light-load or heavy-load state. Other multiples can be set according to actual requirements, and the application is not particularly limited.

In order to ensure the reliability of the sampled voltage of the load current signal IOUT received by the adjustment module 420, as shown in fig. 10, in one example, the zero-crossing detection circuit 400 may further include a sampling module 430, an input end of the sampling module 430 is configured to receive the load current signal IOUT, an output end of the sampling module 430 is connected to the adjustment module 420, the sampling module 430 may sample and amplify the load current signal IOUT, and convert the amplified load current signal IOUT into a sampled voltage and output the sampled voltage to the adjustment module 420, so as to ensure the accuracy of the sampled voltage of the load current signal IOUT received by the adjustment module 420.

Alternatively, the sampling module 430 may be an amplifier, and the present application is not limited in particular.

The embodiment of the present application further provides a zero-crossing detection method, which is applied to the zero-crossing detection circuit 400 described in any of the foregoing optional manners, and in an example, as shown in fig. 11, the zero-crossing detection method may include:

s1, the adjusting module 420 obtains a load current signal IOUT, and adjusts a voltage of the non-inverting input terminal and/or the inverting input terminal of the comparator COMP according to the load current signal IOUT.

For example, taking as an example the voltages of the non-inverting input terminal and the inverting input terminal of the comparator COMP according to the load current signal IOUT, the adjusting module 420 may increase the voltage of the inverting input terminal of the comparator COMP when the sampled voltage corresponding to the load current signal IOUT is greater than the reference voltage, and the adjusting module 420 may increase the voltage of the non-inverting input terminal of the comparator COMP when the sampled voltage corresponding to the load current signal IOUT is less than the reference voltage. In this way, the adjusting module 420 can adjust the voltages of the non-inverting input terminal and the inverting input terminal of the comparator COMP based on the load current signal IOUT, so as to improve the reliability of the zero-crossing detection of the comparator COMP in the heavy load, light load or no load state, and further improve the conversion efficiency and the use reliability of the dc-dc conversion circuit 100 applying the zero-crossing detection circuit 400.

For example, taking as an example that only the voltage of the non-inverting input terminal of the comparator COMP is adjusted according to the load current signal IOUT, the adjusting module 420 may decrease the voltage of the non-inverting input terminal of the comparator COMP when the sampled voltage corresponding to the load current signal IOUT is greater than the reference voltage, and the adjusting module 420 may increase the voltage of the non-inverting input terminal of the comparator COMP when the sampled voltage corresponding to the load current signal IOUT is less than the reference voltage. In this way, the adjusting module 420 can adjust the voltage of the non-inverting input terminal of the comparator COMP based on the load current signal IOUT, so as to improve the reliability of zero-crossing detection of the comparator COMP in heavy load, light load or no load states, and further improve the conversion efficiency and the reliability of use of the dc-dc conversion circuit 100 applying the zero-crossing detection circuit 400.

Here, it should be noted that, according to the load current signal IOUT, only the voltage of the inverting input terminal of the comparator COMP may be adjusted, and the specific adjustment manner may be set according to the actual requirement, which is not limited in this application.

S2, the comparator COMP sends a turn-off signal to the control module 410 upon detecting a zero crossing of the voltage at the switching node SW.

S3, the control module 410 controls the lower tube Q1 to be turned off according to the turn-off signal and the input power tube control signal PWM.

The comparator COMP compares the sampling voltage corresponding to the load current signal IOUT with the voltage at the switch node SW to determine that the voltage at the switch node SW is zero crossing, and when the voltage at the switch node SW is detected to be zero crossing, the comparator COMP sends a turn-off signal to the control module 410, so that the control module 410 can control the turn-off of the down tube Q2 based on the turn-off signal, so as to avoid the problem that the turn-on time of the down tube Q2 is too long, and the reverse backflow of the inductance L current occurs, and serious turn-on loss is generated.

The embodiment of the present application further provides a power management chip, which includes the zero-crossing detection circuit 400 and the dc-dc conversion circuit 100 described in any of the above optional manners, which is not described herein again.

It should be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It should also be understood that the term "and/or" as used in this specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.

In addition, in the description of the present application and the appended claims, the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and are not to be construed as indicating or implying relative importance.

Reference in the specification to "one embodiment" or "some embodiments" or the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," and the like in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments" unless expressly specified otherwise. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless expressly specified otherwise.

The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application, and are intended to be included in the scope of the present application.

Claims

1. The utility model provides a zero crossing detection circuit is applied to direct current-direct current conversion circuit, direct current-direct current conversion circuit includes upper pipe and down the pipe, the tie point of the source of upper pipe with the drain electrode of down the pipe is the switch node, its characterized in that includes: the device comprises an adjusting module, a comparator and a control module;

the input end of the regulating module is used for receiving a load current signal, the first output end of the regulating module is connected with the non-inverting input end of the comparator, the second output end of the regulating module is connected with the inverting input end of the comparator, the non-inverting input end of the comparator is also connected with the switch node, the output end of the comparator is connected with the first input end of the control module, the second input end of the control module is used for accessing a power tube control signal, the first output end of the control module is connected with the upper tube, and the second output end of the control module is connected with the lower tube;

the adjusting module is used for adjusting the voltage of the non-inverting input end and/or the inverting input end of the comparator according to the load current signal;

the comparator is used for sending a turn-off signal to the control module when detecting that the voltage at the switch node is zero crossing;

The control module is also used for controlling the lower tube to be turned off according to the turn-off signal and the power tube control signal.

2. The zero-crossing detection circuit of claim 1, wherein,

when the sampling voltage corresponding to the load current signal is larger than the reference voltage, the adjusting module is used for increasing the voltage of the inverting input end of the comparator;

and when the sampling voltage corresponding to the load current signal is smaller than the reference voltage, the regulating module is used for increasing the voltage of the non-inverting input end of the comparator.

3. The zero crossing detection circuit of claim 2, wherein the conditioning module comprises:

a first current source;

one end of the first resistor is connected with the switch node, and the other end of the first resistor is connected with the non-inverting input end of the comparator;

one end of the second resistor is grounded, and the other end of the second resistor is connected with the inverting input end of the comparator;

the controlled end of the first switching tube is used for accessing the reference voltage, the first pole of the first switching tube is connected with the first current source, and the second pole of the first switching tube is connected with the inverting input end of the comparator; and

The controlled end of the second switching tube is used for accessing the sampling voltage corresponding to the load current signal, the first pole of the second switching tube is connected with the first current source, and the second pole of the second switching tube is connected with the non-inverting input end of the comparator.

4. The zero-crossing detection circuit of claim 1, wherein,

when the sampling voltage corresponding to the load current signal is larger than the reference voltage, the adjusting module is used for reducing the voltage of the non-inverting input end of the comparator;

when the sampling voltage corresponding to the load current signal is smaller than the reference voltage, the adjusting module is further used for increasing the voltage of the non-inverting input end of the comparator.

5. The zero crossing detection circuit of claim 4, wherein the adjustment module comprises:

a second current source is provided which is connected to the first current source,

one end of the third resistor is connected with the switch node, and the other end of the third resistor is connected with the non-inverting input end of the comparator;

the controlled end of the third switching tube is used for accessing the reference voltage, the first pole of the third switching tube is connected with the second current source, and the second pole of the third switching tube is grounded;

The controlled end of the fourth switching tube is used for accessing the sampling voltage corresponding to the load current signal, the first pole of the fourth switching tube is connected with the second current source, and the second pole of the fourth switching tube is connected with the non-inverting input end of the comparator; and

one end of the third current source is respectively connected with the other end of the third resistor, the non-inverting input end of the comparator and the second pole of the fourth switching tube, and the other end of the third current source is grounded;

the current flowing through the second current source is greater than the current of the third current source.

6. The zero-crossing detection circuit of any of claims 1-5, further comprising: a sampling module;

the input end of the sampling module is used for receiving the load current signal, the output end of the sampling module is connected with the input end of the adjusting module, and the sampling module is used for converting the load current signal into the sampling voltage and outputting the sampling voltage to the adjusting module.

7. A zero-crossing detection method as claimed in any one of claims 1 to 6, applied to a zero-crossing detection circuit, the method comprising:

The regulation module obtains a load current signal and regulates the voltage of the non-inverting input end and/or the inverting input end of the comparator according to the load current signal;

the comparator sends a turn-off signal to the control module when detecting zero crossing of the voltage at the switch node;

and the control module controls the lower tube to be turned off according to the turn-off signal and the input power tube control signal.

8. The zero crossing detection method as claimed in claim 7, wherein said adjusting the voltage at the non-inverting input and/or the inverting input of the comparator in dependence on the load current signal comprises:

when the sampling voltage corresponding to the load current signal is larger than the reference voltage, the regulating module increases the voltage of the inverting input end of the comparator;

and when the sampling voltage corresponding to the load current signal is smaller than the reference voltage, the regulating module increases the voltage of the non-inverting input end of the comparator.

9. The zero crossing detection method as claimed in claim 7, wherein said adjusting the voltage at the non-inverting input and/or the inverting input of the comparator in dependence on the load current signal comprises:

when the sampling voltage corresponding to the load current signal is larger than the reference voltage, the regulating module reduces the voltage of the non-inverting input end of the comparator;

10. A power management chip comprising the zero crossing detection circuit of any one of claims 1-6, and a dc-dc conversion circuit.