Inductive-current detection circuit for DC-DC converter, and DC-DC converter, and chip

Abstract

Provided in the present disclosure are an inductive-current detection circuit for a DC-DC converter, and a DC-DC converter, and a chip. The inductive-current detection circuit comprises: a switch circuit, a first control circuit, a second control circuit and an output circuit, wherein the switch circuit transfers the voltage at a first end of an inductor of a DC-DC converter to a first node during a period in which a first control signal is at an active level; the first control circuit generates, between a second node and the first node, a voltage difference equal to a first increment value; the second control circuit records a historical voltage positively correlated with the voltage of the first node during a period in which a second control signal is at an active level, and generates, on the basis of the historical voltage and between the second node and the first node, a voltage difference equal to a second increment value, such that the voltage difference between the second node and the first node is equal to the sum of the first increment value and the second increment value; and the output circuit generates a reverse current detection signal on the basis of the voltage of the second node, when the voltage of the second node rises to a flip threshold value, the reverse current detection signal flipping to an active level for turning off a freewheeling tube.

Description

Inductor current detection circuit, DC-DC converter and chip for DC-DC converter

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims priority to a Chinese patent application filed with the Patent Office of China on November 24, 2023, with application number 2023115860673, entitled “Inductor current detection circuit for DC-DC converter and DC-DC converter”, the entire contents of which are incorporated by reference into this disclosure. Technical Field

[0003] The present disclosure relates to the technical field of integrated circuits, and in particular to an inductor current detection circuit, a DC-DC converter, and a chip for a DC-DC converter. Background Art

[0004] DC-DC (direct current-to-direct current) converters are widely used as power sources for various electronic devices due to their high efficiency and low power consumption. Taking a synchronous buck converter (BUCK) as an example, under light load conditions, when the load current drops below the inductor current, inductor current reverse flow occurs. Excessive reverse current can draw energy from the buck's output energy storage capacitor, causing negative voltage at the buck's output, which can damage the load. To prevent the repeated transfer of energy between the input power supply and the output voltage, the buck's freewheeling diode must be disconnected promptly when the inductor current approaches zero, reducing the buck's power consumption in light load mode. Therefore, it is desirable to accurately detect the inductor current of a DC-DC converter.

[0005] Summary of the Invention

[0006] The embodiments described in this disclosure provide an inductor current detection circuit for a DC-DC converter, a DC-DC converter, and a chip.

[0007] According to a first aspect of the present disclosure, an inductor current detection circuit for a DC-DC converter is provided. The inductor current detection circuit includes a switching circuit, a first control circuit, a second control circuit, and an output circuit. The switching circuit is configured to transmit the voltage at the first end of the inductor of the DC-DC converter to a first node during the period when a first control signal is at an active level. The first end of the inductor is directly coupled to the second electrode of the freewheeling diode of the DC-DC converter. The first control signal is at an active level during the freewheeling period when the freewheeling diode is on and during the dead time immediately following the freewheeling period. The first control circuit is configured to generate a voltage difference between a second node and a first node equal to a first incremental value. The second control circuit is configured to record a historical voltage that is positively correlated with the voltage of the first node during the period when the second control signal is at an active level, and generate a voltage difference between the second node and the first node equal to a second incremental value based on the historical voltage, so that the voltage difference between the second node and the first node is equal to the sum of the first incremental value and the second incremental value. The second control signal is at an active level during the dead time. The output circuit is configured to generate a reverse current detection signal based on the voltage at the second node and output the reverse current detection signal from a signal output terminal of the inductor current detection circuit. When the voltage at the second node rises to a flip threshold, the reverse current detection signal flips to an active level to turn off the freewheeling diode.

[0008] In some embodiments of the present disclosure, the effective level of the reverse current detection signal is a high level. The output circuit includes: a first constant current source, a first transistor, and an inverter. The first constant current source is configured to output a first constant current. The control electrode of the first transistor is coupled to the second node. The first electrode of the first transistor is coupled to the first electrode of the freewheeling tube. The second electrode of the first transistor is coupled to the output end of the first constant current source and the input end of the inverter. The output end of the inverter is coupled to the signal output end.

[0009] In some embodiments of the present disclosure, the effective level of the reverse current detection signal is a low level. The output circuit includes: a first constant current source and a first transistor. The first constant current source is configured to output a first constant current. The control electrode of the first transistor is coupled to the second node. The first electrode of the first transistor is coupled to the first electrode of the freewheeling diode. The second electrode of the first transistor is coupled to the output terminal of the first constant current source and the signal output terminal.

[0010] In some embodiments of the present disclosure, the first control circuit includes: a second constant current source and a second transistor. The second constant current source is configured to output a second constant current. The second constant current is less than the first constant current. A control electrode and a second electrode of the second transistor are coupled to a second node and an output terminal of the second constant current source. The first electrode of the second transistor is coupled to the first node.

[0011] In some embodiments of the present disclosure, the size of the second transistor is the same as the size of the first transistor.

[0012] In some embodiments of the present disclosure, the first control circuit includes: a second constant current source and a diode. The second constant current source is configured to output a second constant current, the second constant current being less than the first constant current. The anode of the diode is coupled to the second node and the output terminal of the second constant current source, and the cathode of the diode is coupled to the first node.

[0013] In some embodiments of the present disclosure, a threshold voltage of the diode is equal to a threshold voltage of the first transistor.

[0014] In some embodiments of the present disclosure, the second control circuit includes: a first switch, a third transistor, and a capacitor. A second control signal is provided to a controlled terminal of the first switch. A first terminal of the first switch is coupled to a first node. A second terminal of the first switch is coupled to a first terminal of the capacitor and a control terminal of the third transistor. A second terminal of the capacitor is coupled to a first terminal of the first transistor. A first terminal of the third transistor is coupled to a second node. A second terminal of the third transistor is coupled to a first voltage terminal.

[0015] In some embodiments of the present disclosure, the first switch is a fourth transistor. A control electrode of the fourth transistor is provided with a second control signal. A first electrode of the fourth transistor is coupled to the first end of the capacitor and the control electrode of the third transistor. A second electrode of the fourth transistor is coupled to the first node.

[0016] In some embodiments of the present disclosure, a switching circuit includes a second switch. A first control signal is provided to a controlled terminal of the second switch. A first terminal of the second switch is coupled to a first node. A second terminal of the second switch is coupled to a first terminal of an inductor of a DC-DC converter and a second terminal of a freewheeling diode.

[0017] In some embodiments of the present disclosure, the DC-DC converter operates in a discontinuous switching mode (DCM).

[0018] In some embodiments of the present disclosure, the first end of the switching circuit is coupled to the first end of the inductor and the second pole of the freewheeling diode, and the second end of the switching circuit is coupled to the first end of the first control circuit and the first end of the second control circuit via the first node; the second end of the first control circuit is coupled to the input end of the output circuit and the second end of the second control circuit via the second node; the output end of the output circuit serves as the signal output end of the inductor current detection circuit.

[0019] In some embodiments of the present disclosure, the first control signal is generated based on the upper tube control signal and the lower tube control signal, and the first control signal is at a valid level during a time period from when the lower tube control signal flips to a valid level to when the upper tube control signal flips to a valid level.

[0020] In some embodiments of the present disclosure, the second control signal is generated based on the upper tube control signal and the lower tube control signal, and the second control signal is at a valid level during a time period between when the lower tube control signal flips to an invalid level and when the upper tube control signal flips to a valid level.

[0021] According to a second aspect of the present disclosure, an inductor current detection circuit for a DC-DC converter is provided. The inductor current detection circuit includes: a first transistor, a second transistor, a third transistor, a first constant current source, a second constant current source, a capacitor, a first switch, a second switch, and an inverter. The first constant current source is configured to output a first constant current. The control electrode of the first transistor is coupled to the control electrode and the second electrode of the second transistor. The first electrode of the first transistor is coupled to the first electrode of a freewheeling diode of the DC-DC converter. The second electrode of the first transistor is coupled to the output of the first constant current source and the input of the inverter. The output of the inverter is coupled to a signal output of the inductor current detection circuit. A reverse current detection signal is output from the signal output. The active level of the reverse current detection signal is used to shut down the freewheeling diode. The second constant current source is configured to output a second constant current. The second constant current is less than the first constant current. The control electrode of the second transistor is coupled to the output of the second constant current source and the first electrode of the third transistor. The first electrode of the second transistor is coupled to the first terminal of the first switch and the first terminal of the second switch. The controlled terminal of the second switch is provided with a first control signal. The second end of the second switch is coupled to the first end of the inductor of the DC-DC converter and the second electrode of the freewheeling diode. The first control signal is at an active level during a freewheeling period when the freewheeling diode is on and during a dead time immediately following the freewheeling period. The second control signal is provided to the controlled end of the first switch. The second end of the first switch is coupled to the first end of the capacitor and the control electrode of the third transistor. The second control signal is at an active level during the dead time. The second end of the capacitor is coupled to the first electrode of the first transistor. The second electrode of the third transistor is coupled to the first voltage terminal.

[0022] According to a third aspect of the present disclosure, a DC-DC converter is provided, comprising the inductor current detection circuit according to the first aspect or the second aspect of the present disclosure.

[0023] According to a fourth aspect of the present disclosure, a chip is provided, comprising the DC-DC converter according to the third aspect of the present disclosure.

[0024] According to a fifth aspect of the present disclosure, an electronic device is provided, comprising the chip according to the fourth aspect of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the present disclosure or related technologies, the following is a brief introduction to the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are some embodiments of the present disclosure, rather than limitations of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0026] FIG1 is an exemplary topology diagram of a DC-DC converter;

[0027] FIG2 is a waveform diagram of some signals of the DC-DC converter shown in FIG1 in the absence of reverse current;

[0028] FIG3 is a waveform diagram of some signals of the DC-DC converter shown in FIG1 in the presence of a reverse current;

[0029] 4 is a schematic block diagram of an inductor current detection circuit for a DC-DC converter according to an embodiment of the present disclosure;

[0030] 5 is an exemplary circuit diagram of an inductor current detection circuit for a DC-DC converter according to an embodiment of the present disclosure;

[0031] FIG6 is another exemplary circuit diagram of an inductor current detection circuit for a DC-DC converter according to an embodiment of the present disclosure.

[0032] In the drawings, reference numerals having the same last two digits correspond to the same elements. It should be noted that the elements in the drawings are schematic and not drawn to scale. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative work also fall within the scope of protection of the present disclosure.

[0034] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the specification and the relevant art, and will not be interpreted in an idealized or overly formal manner unless otherwise explicitly defined herein. As used herein, a statement that two or more parts are "connected" or "coupled" together shall mean that the parts are joined together either directly or through one or more intermediate components.

[0035] In all embodiments of the present disclosure, since the source and drain of the metal oxide semiconductor (MOS) transistor are symmetrical, and the conduction current directions between the source and drain of the N-type transistor and the P-type transistor are opposite, in the embodiments of the present disclosure, the controlled middle end of the MOS transistor is referred to as the control electrode, and the other two ends of the MOS transistor are referred to as the first electrode and the second electrode, respectively. In addition, for the convenience of unified expression, in this context, the base of the bipolar transistor (BJT) is referred to as the control electrode, the emitter of the BJT is referred to as the first electrode, and the collector of the BJT is referred to as the second electrode. In addition, terms such as "first" and "second" are only used to distinguish one component (or a part of a component) from another component (or another part of a component).

[0036] Figure 1 shows an exemplary topology diagram of a DC-DC converter (synchronous BUCK). In the example of Figure 1, the DC-DC converter generates an output voltage Vout based on the input voltage VIN. The control loop in the DC-DC converter can generate an upper tube control signal HG and a lower tube control signal LG to control the alternating conduction of the power tube MH and the freewheeling tube ML. The first end of the inductor L (node ​​LX) is directly coupled to the power tube MH and the freewheeling tube ML, and the second end of the inductor L is directly coupled to the output energy storage capacitor Cout and the output voltage terminal Vout. A load resistor RL is also shown in Figure 1. Under normal circumstances, the inductor current IL flows from the first end to the second end of the inductor L. Under light load conditions, when the load current drops below the inductor current IL, a reverse inductor current IL will appear (that is, the inductor current IL flows from the second end to the first end of the inductor L).

[0037] FIG2 shows the voltage V at the node LX LXS Waveform diagram when there is no reverse inductor current in the DC-DC converter. At time T1, the lower tube control signal LG flips to a low level to control the freewheeling tube ML to turn off, and the inductor current IL continues to flow through the body diode of the freewheeling tube ML. After the conduction delay of the inductor L, at time T2, the voltage V LXSAt time T3, the upper tube control signal HG turns to high level to control the power tube MH to turn on. At this time, the voltage V at the node LX is LXS The period between T1 and T3 is usually called "dead time". As shown in Figure 2, if there is no reverse current during the dead time, the voltage V LXS Will not exceed 0V.

[0038] FIG3 shows the voltage V at the node LX LXS Waveform diagram when reverse inductor current appears in the DC-DC converter. Before time T1, if reverse inductor current IL appears, the voltage V at node LX LXS At this time, the lower tube control signal LG is at a high level, and the freewheeling tube ML is turned on, so the voltage V at the node LX is LXS The maximum voltage can be increased to the threshold voltage of the freewheeling tube ML. Since the threshold voltage of the freewheeling tube ML is relatively small compared to the input voltage VIN, the voltage V LXS At time T1, the lower tube control signal LG turns to low level, thus controlling the freewheeling tube ML to turn off. After the conduction delay of the inductor L, at time T2, the voltage V LXS When the reverse inductor current IL is large, the reverse inductor current IL can be discharged to the input voltage terminal VIN through the body diode of the power tube MH, thereby making the voltage V LXS rises to exceed the input voltage VIN. In this case, the voltage V LXS The waveform is shown in curve 31. If the reverse inductor current IL is small, only the overshoot caused by the reverse inductor current IL charging the parasitic capacitance at the node LX is shown. In this case, the voltage V LXS The waveform is shown as curve 32 or curve 33. Curve 32 and curve 33 are used to represent different overshoot amplitudes.

[0039] In this context, a voltage V exceeding 0V LXS This can be called flyback-surging voltage.

[0040] The inductor current zero-crossing detection circuits in related art typically detect whether the inductor current has crossed zero, without considering adaptive adjustment of the zero-crossing detection threshold. Consequently, the kickback voltage at node LX is highly uncertain. If the inductor current zero-crossing detection circuits in related art are used, the DC-DC converter may disconnect the freewheeling diode due to detection of reverse current. It may also trigger the freewheeling diode to freewheel during the dead time, resulting in poor freewheeling diode disconnection response. Furthermore, the freewheeling diode may be disconnected before the power diode is connected due to the transition from freewheeling to charging.

[0041] To this end, the present disclosure proposes an inductor current detection circuit for a DC-DC converter, which uses the size of the kickback voltage that may occur when the freewheeling tube is disconnected to evaluate whether there is a reverse inductor current when the freewheeling tube is disconnected, and uses the kickback voltage in the dead time to adaptively adjust the current detection threshold so that the current detection threshold eventually converges to the target value. The target value can be zero current or a target reverse current (negative current). Accordingly, the kickback voltage will also converge to the target voltage value. The converged stable kickback voltage can improve the circuit-breaking response of the freewheeling tube (meaning that when there is a reverse current, the freewheeling tube is not triggered to continue flowing within the dead time). If the current detection threshold eventually converges to a negative value, the converged kickback voltage can reduce the voltage difference that needs to be increased when the power tube is turned on after charging the parasitic capacitance at the node LX, thereby being more conducive to the stability of the output voltage.

[0042] FIG4 shows a schematic block diagram of an inductor current detection circuit 400 for a DC-DC converter according to an embodiment of the present disclosure. In some embodiments of the present disclosure, the DC-DC converter operates in discontinuous switching mode (DCM). FIG4 shows a power transistor MH, a freewheeling transistor ML, and an inductor L in the DC-DC converter. The input terminal of the inductor current detection circuit 400 is coupled to a node LX of the DC-DC converter. The inductor current detection circuit 400 includes a switching circuit 410, a first control circuit 420, a second control circuit 430, and an output circuit 440.

[0043] The first terminal of the switch circuit 410 is directly coupled to the first terminal of the inductor L and the second terminal of the freewheeling diode ML. The second terminal of the switch circuit 410 is coupled to the first terminal of the first control circuit 420 and the first terminal of the second control circuit 430 via the first node N1. The switch circuit 410 is configured to: when the first control signal Cr1 is at an active level, the voltage V at the first terminal of the inductor L of the DC-DC converter is V LXS The first terminal of the inductor L is directly coupled to the second electrode of the freewheeling transistor ML of the DC-DC converter. The first control signal Cr1 is at an active level during the freewheeling period when the freewheeling transistor ML is turned on and during the dead time immediately after the freewheeling period.

[0044] In some embodiments of the present disclosure, the first control signal Cr1 can be generated based on the high-side control signal HG and the low-side control signal LG. The first control signal Cr1 remains active during the period between when the low-side control signal LG transitions to an active level and when the high-side control signal HG transitions to an active level. The inductor current detection circuit 400 may further include circuitry for generating the first control signal Cr1.

[0045] A first terminal of the first control circuit 420 is coupled to a second terminal of the switch circuit 410 and a first terminal of the second control circuit 430 via a first node N1. A second terminal of the first control circuit 420 is coupled to an input terminal of the output circuit 440 and a second terminal of the second control circuit 430 via a second node N2. The first control circuit 420 is configured to generate a voltage difference between the second node N2 and the first node N1 that is equal to a first incremental value. When the first node N1 is not floating (i.e., when the first control signal Cr1 is at an active level), the first incremental value is greater than 0V.

[0046] A first terminal of the second control circuit 430 is coupled to the second terminal of the switch circuit 410 and the first terminal of the first control circuit 420 via a first node N1. A second terminal of the second control circuit 430 is coupled to the input terminal of the output circuit 440 and the second terminal of the first control circuit 420 via a second node N2. The second control circuit 430 is configured to record a historical voltage that is positively correlated with the voltage of the first node N1 while the second control signal Cr2 is at an active level, and generate a voltage difference between the second node N2 and the first node N1 equal to a second incremental value based on the historical voltage, such that the voltage difference between the second node N2 and the first node N1 is equal to the sum of the first incremental value and the second incremental value. The second control signal Cr2 is at an active level during the dead time. Therefore, the second control circuit 430 can record voltage information related to the voltage of the node LX during the dead time. In some embodiments of the present disclosure, when the historical voltage is greater than 0V, the second incremental value is greater than 0V. When the historical voltage is equal to or less than 0V, the second incremental value is equal to 0V.

[0047] In some embodiments of the present disclosure, the second control signal Cr2 can be generated based on the high-side control signal HG and the low-side control signal LG. The second control signal Cr2 remains active during the period between when the low-side control signal LG transitions to an inactive level and when the high-side control signal HG transitions to an active level. The inductor current detection circuit 400 may further include circuitry for generating the second control signal Cr2.

[0048] The input end of the output circuit 440 is coupled to the second end of the first control circuit 420 and the second end of the second control circuit 430 via the second node N2. The output end of the output circuit 440 serves as the signal output end of the inductor current detection circuit 400. The output circuit 440 is configured to generate a reverse current detection signal RCD according to the voltage of the second node N2 and output the reverse current detection signal RCD from the signal output end of the inductor current detection circuit 400. The reverse current detection signal RCD is at an invalid level when the voltage of the second node N2 is lower than the flip threshold. When the voltage of the second node N2 rises to the flip threshold, the reverse current detection signal RCD flips to a valid level for turning off the freewheeling tube ML. In actual applications, the flip threshold is a fixed voltage value that can be set according to the target kickback voltage, the first incremental value and the second incremental value. The target kickback voltage is the voltage V at the first end of the inductor L when the inductor current flowing through the inductor L is equal to the target reverse current during the freewheeling period when the freewheeling tube ML is turned on. LXS Here, the second incremental value for setting the flip threshold is positively correlated with the kickback voltage of one cycle before the target kickback voltage occurs. In this context, "cycle" refers to the switching cycle of the DC-DC converter.

[0049] When the DC-DC converter using the inductor current detection circuit 400 does not have a reverse inductor current IL (the direction of the inductor current IL is consistent with the direction indicated by the arrow in FIG4 ), the lower tube control signal LG is controlled by a pulse width modulation (PWM) signal (not shown) to control the freewheeling tube ML to be turned on and off according to a preset duty cycle.

[0050] Assume that in the nth cycle, the DC-DC converter using the inductor current detection circuit 400 has a reverse inductor current IL (the direction of the inductor current IL is opposite to the direction indicated by the arrow in FIG4 ). Then, during the conduction period of the freewheeling transistor ML, the voltage V at the node LX is LXS The switch circuit 410 increases the voltage V LXS is transferred to the first node N1. The first control circuit 420 can generate a voltage difference between the second node N2 and the first node N1 that is equal to the first incremental value. If the historical voltage previously recorded by the second control circuit 430 is not large enough (for example, the kickback voltage in the previous cycle (the n-1 cycle) is small, or no kickback voltage occurs), the voltage difference between the second node N2 and the first node N1 that is equal to the second incremental value generated by the second control circuit 430 is small (or zero). Since the voltage difference between the second node N2 and the first node N1 is equal to the sum of the first incremental value and the second incremental value, the kickback voltage V at the node LX is LXSThe voltage of the second node N2 cannot be pushed up to exceed the flip threshold, so the reverse current detection signal RCD will not flip to the valid level. LXS The rise can be significantly increased. At this time, the kickback voltage V LXS The voltage may be provided to the second control circuit 430 via the first node N1 and converted into a historical voltage by the second control circuit 430. The historical voltage is recorded in the second control circuit 430 for use in the next cycle (the n+1th cycle).

[0051] In the next cycle (cycle n+1), if the reverse inductor current IL still appears, since the historical voltage is large, the second increment value is also large, and the kickback voltage V LXS The voltage of the second node N2 can be pushed up to exceed the flip threshold without increasing to the value of the previous cycle (nth cycle). At this time, the reverse current detection signal RCD flips to the valid level, causing the lower tube control signal LG to flip to the invalid level in advance, thereby turning off the freewheeling tube ML in advance. In this way, the reverse inductor current IL of the next cycle (n+2th cycle) will be reduced accordingly, thereby reducing the kickback voltage V LXS By setting the kickback voltage V LXS The transfer coefficient between the historical voltage recorded by the second control circuit 430 (the historical voltage and the kickback voltage V LXS ratio), which can make the reverse inductor current IL gradually converge, and the kickback voltage V LXS It also gradually converges and eventually reaches stability. Here, the transfer coefficient should be set to be less than 1. In addition, by setting the flip threshold, the kickback voltage V LXS Finally, the target kickback voltage is converged, so that the reverse inductor current IL finally converges to the target reverse current. The target kickback voltage and target reverse current can be determined according to the actual application.

[0052] FIG5 shows an exemplary circuit diagram of an inductor current detection circuit 500 for a DC-DC converter according to an embodiment of the present disclosure. In the example of FIG5 , the effective level of the reverse current detection signal RCD is a high level. The output circuit 540 may include: a first constant current source CC1, a first transistor M1, and an inverter NG. The first constant current source CC1 may be powered by a first voltage V1 from a first voltage terminal V1. The first constant current source CC1 is configured to output a first constant current CC1. The control electrode of the first transistor M1 is coupled to the second node N2. The first electrode of the first transistor M1 is coupled to the first electrode of the freewheeling tube ML. The second electrode of the first transistor M1 is coupled to the output terminal of the first constant current source CC1 and the input terminal of the inverter NG. The output terminal of the inverter NG is coupled to the signal output terminal.

[0053] In the example of FIG. 5 , the first control circuit 520 includes a second constant current source CC2 and a second transistor M2. The second constant current source CC2 can be powered by a first voltage V1. The second constant current source CC2 is configured to output a second constant current CC2. The second constant current CC2 is less than the first constant current CC1. The control electrode and the second electrode of the second transistor M2 are coupled to a second node N2 and an output terminal of the second constant current source CC2. The first electrode of the second transistor M2 is coupled to the first node N1.

[0054] In some embodiments of the present disclosure, the size of the second transistor M2 is the same as the size of the first transistor M1 .

[0055] In the example of FIG5 , the second control circuit 530 includes a first switch S1, a third transistor M3, and a capacitor C. A second control signal Cr2 is provided to a controlled terminal of the first switch S1. A first terminal of the first switch S1 is coupled to a first node N1. A second terminal of the first switch S1 is coupled to a first terminal of the capacitor C and a control terminal of the third transistor M3. A second terminal of the capacitor C is coupled to a first terminal of the first transistor M1. A first terminal of the third transistor M3 is coupled to a second node N2. A second terminal of the third transistor M3 is coupled to a first voltage terminal V1.

[0056] In some embodiments of the present disclosure, the first switch S1 can be implemented by a transistor. For convenience, this transistor is referred to as a fourth transistor. A second control signal Cr2 is provided to a control electrode of the fourth transistor. A first electrode of the fourth transistor is coupled to the first end of the capacitor C and the control electrode of the third transistor M3. A second electrode of the fourth transistor is coupled to the first node N1. The kickback voltage V during the dead time is LXS The transfer coefficient with the historical voltage recorded by the second control circuit 430 can be set by the internal resistance of the fourth transistor.

[0057] In the example of FIG5 , the switching circuit 510 includes a second switch S2. A first control signal Cr1 is provided to a controlled terminal of the second switch S2. A first terminal of the second switch S2 is coupled to a first node N1. A second terminal of the second switch S2 is directly coupled to a first terminal of an inductor L of the DC-DC converter and a second terminal of the freewheeling diode ML (i.e., node LX).

[0058] FIG6 shows an exemplary circuit diagram of an inductor current detection circuit 600 for a DC-DC converter according to an embodiment of the present disclosure. The output circuit 640 and the first control circuit 620 in FIG6 are variations of the output circuit 540 and the first control circuit 520 in FIG5 . In the example of FIG6 , the active level of the reverse current detection signal RCD is a low level. The output circuit 640 includes: a first constant current source CC1 and a first transistor M1. The first constant current source CC1 can be powered by a first voltage V1 from a first voltage terminal V1. The first constant current source CC1 is configured to output a first constant current CC1. The control electrode of the first transistor M1 is coupled to the second node N2. The first electrode of the first transistor M1 is coupled to the first electrode of the freewheeling tube ML. The second electrode of the first transistor M1 is coupled to the output terminal and the signal output terminal of the first constant current source CC1.

[0059] In the example of FIG6 , the first control circuit 620 includes a second constant current source CC2 and a diode D. The second constant current source CC2 can be powered by a first voltage V1. The second constant current source CC2 is configured to output a second constant current CC2. The second constant current CC2 is less than the first constant current CC1. The anode of the diode D is coupled to the second node N2 and the output terminal of the second constant current source CC2. The cathode of the diode D is coupled to the first node N1.

[0060] In some embodiments of the present disclosure, the threshold voltage of the diode D is equal to the threshold voltage of the first transistor M1 .

[0061] In the examples of Figures 5 and 6, a high voltage signal is input from the first voltage terminal V1, and the second voltage terminal V2 is grounded. The first voltage terminal V1 may also be the input voltage terminal VIN. The first transistor M1 to the third transistor M3 are NMOS transistors. Those skilled in the art will understand that variations of the circuits shown in Figures 5 and 6 based on the above-mentioned inventive concepts should also fall within the scope of protection of this disclosure. In such variations, the above-mentioned transistors and voltage terminals may also have different configurations than those shown in the examples of Figures 5 and 6.

[0062] The working process of the inductor current detection circuit 500 according to the embodiment of the present disclosure is described below with reference to the example of FIG. 5 .

[0063] When the DC-DC converter using the inductor current detection circuit 500 does not have a reverse inductor current IL (the direction of the inductor current IL is consistent with the direction indicated by the arrow in FIG5 ), the lower tube control signal LG is controlled by the PWM signal (not shown) to control the freewheeling tube ML to be turned on and off according to a preset duty cycle.

[0064] Assume that in the nth cycle, the DC-DC converter using the inductor current detection circuit 500 has a reverse inductor current IL (the direction of the inductor current IL is opposite to the direction indicated by the arrow in FIG5 ). Then, during the conduction period of the freewheeling transistor ML, the voltage V at the node LX is LXS The first control signal Cr1 is at an effective level, and the second switch is closed, thereby reducing the voltage V LXS is transferred to the first node N1. The second constant current source CC2 turns on the second transistor M2, thereby generating a voltage difference between the second node N2 and the first node N1 that is equal to the first incremental value (equal to the threshold voltage of the second transistor M2). If the kickback voltage in the previous cycle (the n-1 cycle) is small, or no kickback voltage occurs, the charge stored on the capacitor C is not large enough (the historical voltage is not large enough), and the third transistor M3 is not fully turned on or is in the cut-off state (the second incremental value is small or zero). Since the voltage difference between the second node N2 and the first node N1 is equal to the sum of the first incremental value and the second incremental value, the kickback voltage V at the node LX is LXS The voltage of the second node N2 cannot be pushed up to exceed the flip threshold, so the reverse current detection signal RCD will not flip to the valid level. From the current point of view, if the voltage V LXS Since the first transistor M1 and the second transistor M2 have the same size, the current flowing through the first transistor M1 is equal to the current flowing through the second transistor M2 (the second constant current CC2). Therefore, if the reverse inductor current IL is not higher than the difference between the first constant current CC1 and the second constant current CC2, the reverse current detection signal RCD will not flip to the active level.

[0065] Referring to Figure 3, after the freewheeling tube ML is disconnected, the kickback voltage V LXS The rise can be significantly increased. At this time, the kickback voltage V LXS The first node N1 can be provided to the first switch S1. Since the first switch S1 has an internal resistance, the kickback voltage V LXS After being multiplied by the transfer coefficient, it is stored at the first terminal of the capacitor C for use in the next cycle (cycle n+1). At this time, since the freewheeling diode ML is disconnected, the normal operation of the DC-DC converter will not be affected even if the reverse current detection signal RCD flips to the active level.

[0066] In the next cycle (cycle n+1), if the reverse inductor current IL still appears, since the voltage at the first terminal of the capacitor C (historical voltage) is larger, the voltage at the second node N2 is pulled up accordingly (the second increment value is the historical voltage minus the gate-source voltage of the third transistor), and the kickback voltage V LXSThe voltage of the second node N2 can be pushed up to exceed the flip threshold without increasing to the value of the previous cycle (nth cycle). At this time, the reverse current detection signal RCD flips to the valid level, causing the lower tube control signal LG to flip to the invalid level in advance, thereby turning off the freewheeling tube ML in advance. In this way, the reverse inductor current IL of the next cycle (n+2th cycle) will be reduced accordingly, thereby reducing the kickback voltage V LXS By properly setting the internal resistance of the first switch S1, the reverse inductor current IL can be gradually converged, and the kickback voltage V LXS Also gradually converges and finally reaches stability. Here, the internal resistance value of the first switch S1 is set to make the transfer coefficient less than 1. In addition, by setting the flip threshold, the kickback voltage V LXS Finally, the target kickback voltage is converged, so that the reverse inductor current IL finally converges to the target reverse current. The target kickback voltage and target reverse current can be determined according to the actual application.

[0067] The operation of the inductor current detection circuit 600 in FIG6 is similar to that of the inductor current detection circuit 500 in FIG5 and is not further described here. It should be noted that in FIG6 , the use of a diode D can also generate a voltage difference of the first incremental value between the second node N2 and the first node N1. Therefore, the diode D in FIG6 can be used to replace the second transistor M2 in FIG5 .

[0068] The embodiments of the present disclosure further provide a chip. The chip includes a DC-DC converter according to the embodiments of the present disclosure. The chip is, for example, a power management chip.

[0069] An embodiment of the present disclosure further provides an electronic device. The electronic device includes a chip according to an embodiment of the present disclosure. The electronic device is, for example, a smart terminal device such as a tablet computer, a smart phone, etc.

[0070] In summary, according to the inductor current detection circuit for a DC-DC converter according to the embodiment of the present disclosure, the kickback voltage within the dead time is used to adaptively adjust the detection threshold of the inductor current, so that the inductor current value when the reverse current detection signal flips to the valid level gradually converges and eventually reaches stability, so the kickback voltage will also gradually converge and eventually reach stability. The converged stable kickback voltage can improve the circuit-breaking response of the freewheeling tube (meaning that when there is a reverse current, the freewheeling tube is not triggered to continue to flow within the dead time). If the current detection threshold eventually converges to a negative value, the converged kickback voltage can reduce the voltage difference that needs to be increased when the power tube is turned on after charging the parasitic capacitance at the node LX, thereby being more conducive to the stability of the output voltage. Accordingly, the DC-DC converter using the inductor current detection circuit according to the embodiment of the present disclosure also has the above advantages.

[0071] Unless the context clearly indicates otherwise, as used in this disclosure and the appended claims, the singular form of the words includes the plural and vice versa. Thus, when referring to the singular, the plural of the corresponding term is generally included. Similarly, the words "include" and "comprising" are to be interpreted as inclusive rather than exclusive. Likewise, the terms "include" and "or" should be interpreted as inclusive unless such interpretation is expressly prohibited in this disclosure. Where the term "example" is used in this disclosure, particularly when it follows a group of terms, the "example" is merely exemplary and illustrative and should not be considered exclusive or comprehensive.

[0072] Further aspects and scope of adaptability become apparent from the description provided in this disclosure. It should be understood that various aspects of the disclosure can be implemented alone or in combination with one or more other aspects. It should also be understood that the description and specific embodiments in this disclosure are intended to be illustrative only and are not intended to limit the scope of the disclosure.

[0073] Several embodiments of the present disclosure have been described in detail above, but it is obvious that those skilled in the art can make various modifications and variations to the embodiments of the present disclosure without departing from the spirit and scope of the present disclosure. The scope of protection of the present disclosure is defined by the appended claims.

Claims

1. An inductor current detection circuit for a DC-DC converter, comprising: a switch circuit, a first control circuit, a second control circuit, and an output circuit, The switch circuit is configured to: transfer the voltage at the first end of the inductor of the DC-DC converter to the first node during a period when the first control signal is at an effective level, the first end of the inductor is directly coupled to the second pole of the freewheeling tube of the DC-DC converter, and the first control signal is at the effective level during a freewheeling period when the freewheeling tube is turned on and during a dead time immediately after the freewheeling period; The first control circuit is configured to: generate a voltage difference between a second node and the first node that is equal to a first increment value; The second control circuit is configured to: record a historical voltage positively correlated with the voltage of the first node during a period when the second control signal is at an effective level, and generate a voltage difference between the second node and the first node equal to a second incremental value according to the historical voltage so that the voltage difference between the second node and the first node is equal to a sum of the first incremental value and the second incremental value, and the second control signal is at the effective level during the dead time; The output circuit is configured to generate a reverse current detection signal according to the voltage of the second node and output the reverse current detection signal from the signal output end of the inductor current detection circuit, and the reverse current detection signal is flipped to a valid level for turning off the freewheeling tube when the voltage of the second node rises to a flip threshold.

2. The inductor current detection circuit according to claim 1, wherein: The effective level of the reverse current detection signal is a high level, and the output circuit includes: a first constant current source, a first transistor, and an inverter. Wherein, the first constant current source is configured to: output a first constant current; The control electrode of the first transistor is coupled to the second node, the first electrode of the first transistor is coupled to the first electrode of the freewheeling tube, and the second electrode of the first transistor is coupled to the output end of the first constant current source and the input end of the inverter; The output terminal of the inverter is coupled to the signal output terminal.

3. The inductor current detection circuit according to claim 1, wherein: The effective level of the reverse current detection signal is a low level, and the output circuit includes: a first constant current source, a first transistor, Wherein, the first constant current source is configured to: output a first constant current; The control electrode of the first transistor is coupled to the second node, the first electrode of the first transistor is coupled to the first electrode of the freewheeling tube, and the second electrode of the first transistor is coupled to the output end of the first constant current source and the signal output end.

4. The inductor current detection circuit according to claim 2 or 3, wherein: The first control circuit includes: a second constant current source, a second transistor, Wherein, the second constant current source is configured to: output a second constant current, the second constant current being smaller than the first constant current; A control electrode and a second electrode of the second transistor are coupled to the second node and an output end of the second constant current source, and a first electrode of the second transistor is coupled to the first node.

5. The inductor current detection circuit according to claim 4, wherein: The size of the second transistor is the same as the size of the first transistor.

6. The inductor current detection circuit according to claim 2 or 3, wherein: The first control circuit includes: a second constant current source, a diode, Wherein, the second constant current source is configured to: output a second constant current, the second constant current being smaller than the first constant current; An anode of the diode is coupled to the second node and an output end of the second constant current source, and a cathode of the diode is coupled to the first node.

7. The inductor current detection circuit according to claim 6, wherein: A threshold voltage of the diode is equal to a threshold voltage of the first transistor.

8. The inductor current detection circuit according to claim 2 or 3, wherein: The second control circuit includes: a first switch, a third transistor, and a capacitor. The second control signal is provided to the controlled end of the first switch, the first end of the first switch is coupled to the first node, and the second end of the first switch is coupled to the first end of the capacitor and the control electrode of the third transistor; The second terminal of the capacitor is coupled to the first electrode of the first transistor; A first electrode of the third transistor is coupled to the second node, and a second electrode of the third transistor is coupled to the first voltage terminal.

9. The inductor current detection circuit according to claim 8, wherein: The first switch is a fourth transistor; The second control signal is provided to a control electrode of the fourth transistor, a first electrode of the fourth transistor is coupled to the first end of the capacitor and the control electrode of the third transistor, and a second electrode of the fourth transistor is coupled to the first node.

10. The inductor current detection circuit according to claim 1, wherein: The switch circuit includes a second switch; The controlled end of the second switch is provided with the first control signal, the first end of the second switch is coupled to the first node, and the second end of the second switch is coupled to the first end of the inductor of the DC-DC converter and the second pole of the freewheeling tube.

11. The inductor current detection circuit according to claim 1, wherein: The DC-DC converter operates in a discontinuous switching mode.

12. The inductor current detection circuit according to claim 1, wherein: The first end of the switch circuit is coupled to the first end of the inductor and the second pole of the freewheeling tube, and the second end of the switch circuit is coupled to the first end of the first control circuit and the first end of the second control circuit via the first node; The second terminal of the first control circuit is coupled to the input terminal of the output circuit and the second terminal of the second control circuit via the second node; The output end of the output circuit serves as a signal output end of the inductor current detection circuit.

13. The inductor current detection circuit according to claim 1, wherein: The first control signal is generated according to an upper tube control signal and a lower tube control signal, and the first control signal is at an effective level during a period from when the lower tube control signal flips to an effective level to when the upper tube control signal flips to an effective level.

14. The inductor current detection circuit according to claim 1, wherein: The second control signal is generated according to the upper tube control signal and the lower tube control signal, and the second control signal is at a valid level during a time period from when the lower tube control signal flips to an invalid level to when the upper tube control signal flips to a valid level.

15. An inductor current detection circuit for a DC-DC converter, comprising: a first transistor, a second transistor, a third transistor, a first constant current source, a second constant current source, a capacitor, a first switch, a second switch, and an inverter, Wherein, the first constant current source is configured to: output a first constant current; The control electrode of the first transistor is coupled to the control electrode and the second electrode of the second transistor, the first electrode of the first transistor is coupled to the first electrode of the freewheeling tube of the DC-DC converter, and the second electrode of the first transistor is coupled to the output end of the first constant current source and the input end of the inverter; The output end of the inverter is coupled to the signal output end of the inductor current detection circuit, and a reverse current detection signal is output from the signal output end, and the effective level of the reverse current detection signal is used to turn off the freewheeling tube; The second constant current source is configured to: output a second constant current, the second constant current being smaller than the first constant current; The control electrode of the second transistor is coupled to the output end of the second constant current source and the first electrode of the third transistor, and the first electrode of the second transistor is coupled to the first end of the first switch and the first end of the second switch; A first control signal is provided to a controlled end of the second switch, a second end of the second switch is coupled to a first end of the inductor of the DC-DC converter and a second electrode of the freewheeling tube, and the first control signal is at an effective level during a freewheeling period when the freewheeling tube is turned on and during a dead time immediately after the freewheeling period; A second control signal is provided to a controlled end of the first switch, a second end of the first switch is coupled to a first end of the capacitor and a control electrode of the third transistor, and the second control signal is at an effective level during the dead time; The second terminal of the capacitor is coupled to the first electrode of the first transistor; The second electrode of the third transistor is coupled to the first voltage terminal.

16. A DC-DC converter, comprising: An inductor current detection circuit according to any one of claims 1 to 15.

17. A chip comprising the DC-DC converter according to claim 16.

18. An electronic device comprising the chip according to claim 17.

Images