Inductor current detection circuit for dc-dc converter and dc-dc converter

Abstract

Embodiments of the present disclosure provide an inductor current detection circuit for a DC-DC converter and the DC-DC converter. The inductor current detection circuit includes a switching circuit, first and second control circuits, and an output circuit. The switching circuit transfers a voltage at a first end of an inductor of the DC-DC converter to a first node during a first control signal is at an active level. The first control circuit generates a voltage difference between a second node and the first node equal to a first delta value. The second control circuit records a history voltage positively correlated to the voltage of the first node during a second control signal is at an active level, and generates a voltage difference between the second node and the first node equal to a second delta value according to the history voltage such that the voltage difference between the second node and the first node is equal to a sum of the first and second delta values. The output circuit generates a reverse current detection signal according to the voltage of the second node. The reverse current detection signal flips to an active level when the voltage of the second node rises to a flip threshold for turning off a freewheeling diode.

Description

Technical Field

[0001] Embodiments of this disclosure relate to the field of integrated circuit technology, and more specifically, to an inductor current detection circuit for a DC-DC converter and a DC-DC converter. Background Technology

[0002] DC-DC converters are widely used as power supplies 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 current occurs. Excessive reverse current may draw energy back from the BUCK's output energy storage capacitor, causing a negative voltage at the BUCK's output and potentially damaging the load. To prevent repeated energy transfer between the input power supply and the output voltage, the BUCK's freewheeling diode needs to be disconnected promptly when the inductor current approaches zero, reducing the BUCK's power consumption in light load mode. Therefore, accurate detection of the DC-DC converter's inductor current is desirable. Summary of the Invention

[0003] The embodiments described herein provide an inductor current sensing circuit for a DC-DC converter, and a DC-DC converter.

[0004] According to a first aspect of this 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 transfer a voltage at a first terminal of an inductor in the DC-DC converter to a first node during a first control signal at an active level. The first terminal of the inductor is directly coupled to the second terminal of a freewheeling diode in the DC-DC converter. The first control signal is active during the freewheeling period when the freewheeling diode is conducting and during a dead time immediately following the freewheeling period. The first control circuit is configured to generate a voltage difference between a second node and the first node 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 the second control signal at an active level, and generate a voltage difference between the second node and the first node equal to a second increment value based on the historical voltage, 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. The second control signal is active 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 the signal output terminal of the inductor current detection circuit. The reverse current detection signal flips to an active level when the voltage at the second node rises to the flip threshold to turn off the freewheeling diode.

[0005] In some embodiments of this disclosure, the effective level of the reverse current detection signal is high. 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 a second node. The first electrode of the first transistor is coupled to the first electrode of a freewheeling diode. The second electrode of the first transistor is coupled to the output terminal of the first constant current source and the input terminal of the inverter. The output terminal of the inverter is coupled to a signal output terminal.

[0006] In some embodiments of this disclosure, the effective level of the reverse current detection signal is low. 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 a second node. The first electrode of the first transistor is coupled to the first electrode of a 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.

[0007] In some embodiments of this 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 a first constant current. The control electrode and the second electrode of the second transistor are coupled to a second node and the output terminal of the second constant current source. The first electrode of the second transistor is coupled to a first node.

[0008] In some embodiments of this disclosure, the second transistor has the same dimensions as the first transistor.

[0009] In some embodiments of this 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 is less than a first constant current. The anode of the diode is coupled to a second node and the output terminal of the second constant current source. The cathode of the diode is coupled to a first node.

[0010] In some embodiments of this disclosure, the threshold voltage of the diode is equal to the threshold voltage of the first transistor.

[0011] In some embodiments of this disclosure, the second control circuit includes: a first switch, a third transistor, and a capacitor. The controlled terminal of the first switch is provided with a second control signal. 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 the control electrode of the third transistor. A second terminal of the capacitor is coupled to a first electrode of the first transistor. A first electrode of the third transistor is coupled to a second node. A second electrode of the third transistor is coupled to a first voltage terminal.

[0012] In some embodiments of this disclosure, the first switch is a fourth transistor. A second control signal is provided to the control electrode of the fourth transistor. The first electrode of the fourth transistor is coupled to a first terminal of a capacitor and the control electrode of a third transistor. The second electrode of the fourth transistor is coupled to a first node.

[0013] In some embodiments of this disclosure, the switching circuit includes: a second switch. A first control signal is provided to the 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.

[0014] In some embodiments of this disclosure, the DC-DC converter operates in discontinuous switching mode (DCM).

[0015] According to a second aspect of this 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 the freewheeling diode of the DC-DC converter. The second electrode of the first transistor is coupled to the output terminal of the first constant current source and the input terminal of the inverter. The output terminal of the inverter is coupled to the signal output terminal of the inductor current detection circuit. A reverse current detection signal is output from the signal output terminal. The effective level of the reverse current detection signal is used to turn off 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 terminal 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. A first control signal is provided to the controlled terminal of the second switch. The second terminal of the second switch is coupled to the first terminal of the inductor of the DC-DC converter and the second terminal of the freewheeling diode. A first control signal is active during the freewheeling period when the freewheeling diode is on and immediately following the freewheeling period in the dead time. A second control signal is provided to the controlled terminal of the first switch. The second terminal of the first switch is coupled to the first terminal of a capacitor and the control terminal of a third transistor. The second control signal is active during the dead time. The second terminal of the capacitor is coupled to the first terminal of the first transistor. The second terminal of the third transistor is coupled to a first voltage terminal.

[0016] According to a third aspect of this disclosure, a DC-DC converter is provided. The DC-DC converter includes an inductor current detection circuit as described in a first or second aspect of this disclosure.

[0017] According to a fourth aspect of this disclosure, a chip is provided. The chip includes the DC-DC converter described in a third aspect of this disclosure.

[0018] According to a fifth aspect of this disclosure, an electronic device is provided. The electronic device includes the chip described in a fourth aspect of this disclosure. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. It should be understood that the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure, wherein:

[0020] Figure 1 An exemplary topology diagram of a DC-DC converter;

[0021] Figure 2 yes Figure 1 The waveforms of some signals of the DC-DC converter shown are in the absence of reverse current.

[0022] Figure 3 yes Figure 1 The waveforms of some signals of the DC-DC converter shown are displayed under reverse current conditions.

[0023] Figure 4 This is a schematic block diagram of an inductor current detection circuit for a DC-DC converter according to an embodiment of the present disclosure;

[0024] Figure 5 This is an exemplary circuit diagram of an inductor current sensing circuit for a DC-DC converter according to an embodiment of the present disclosure;

[0025] Figure 6 This is another exemplary circuit diagram of an inductor current sensing circuit for a DC-DC converter according to embodiments of the present disclosure.

[0026] In the accompanying diagram, markers with the same last two digits correspond to the same elements. It should be noted that the elements in the diagram are schematic and not drawn to scale. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are also within the scope of protection of this disclosure.

[0028] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this subject matter pertains. It will be further understood that terms such as those defined in commonly used dictionaries shall be interpreted as having the meaning consistent with their meaning in the context of the specification and in the relevant art, and shall not be interpreted in an idealized or overly formal form unless otherwise explicitly defined herein. As used herein, the statement of “connecting” or “coupling” two or more parts together shall mean that these parts are directly joined together or joined through one or more intermediate components.

[0029] In all embodiments of this disclosure, since the source and drain of a metal-oxide-semiconductor (MOS) transistor are symmetrical, and the conduction current directions between the source and drain of an N-type transistor and a P-type transistor are opposite, the controlled middle terminal of the MOS transistor is referred to as the control terminal, and the remaining two terminals of the MOS transistor are referred to as the first terminal and the second terminal, respectively. Furthermore, for the sake of consistency, in this context, the base of a bipolar junction transistor (BJT) is referred to as the control terminal, the emitter of the BJT as the first terminal, and the collector of the BJT as the second terminal. Additionally, terms such as "first" and "second" are used only to distinguish one component (or part of a component) from another component (or another part of a component).

[0030] Figure 1 An exemplary topology diagram of a DC-DC converter (synchronous BUCK) is shown. Figure 1 In the example, the DC-DC converter generates the output voltage Vout based on the input voltage VIN. The control loop in the DC-DC converter generates the upper transistor control signal HG and the lower transistor control signal LG to control the power transistor MH and the freewheeling transistor ML to conduct alternately. The first terminal of the inductor L (node ​​LX) is directly coupled to the power transistor MH and the freewheeling transistor ML, and the second terminal of the inductor L is directly coupled to the output energy storage capacitor Cout and the output voltage terminal Vout. Figure 1 The diagram also shows the load resistor RL. Under normal conditions, the inductor current IL flows from the first terminal of inductor L to the second terminal. Under light load conditions, when the load current decreases below the inductor current IL, a reverse inductor current IL occurs (i.e., the inductor current IL flows from the second terminal of inductor L to the first terminal).

[0031] Figure 2 The voltage V at node LX is shown. LXS The waveform diagram shows the DC-DC converter without reverse inductor current. At time T1, the lower transistor control signal LG flips to low, thus turning off the freewheeling transistor ML, and the inductor current IL freewheels through the body diode of the freewheeling transistor ML. After the conduction delay of inductor L, at time T2, the voltage V at node LX is...LXS A negative value appears. At time T3, the upper transistor control signal HG flips to a high level, thereby controlling the power transistor MH to conduct. At this time, the voltage V at node LX is... LXS The voltage gradually rises to the input voltage VIN. The time period between time T1 and time T3 is usually called the "dead time". Figure 2 It can be seen that during the dead time, if no reverse current occurs, the voltage V at node LX will be... LXS It will not exceed 0V.

[0032] Figure 3 The voltage V at node LX is shown. LXS Waveform diagram showing the presence of reverse inductor current in the DC-DC converter. Before time T1, if reverse inductor current IL occurs, the voltage V at node LX will be... LXS The voltage will be raised. At this time, the lower diode control signal LG is at a high level, the freewheeling diode ML is turned on, therefore the voltage V at node LX will be raised. LXS The voltage can be increased up to the threshold voltage of the freewheeling diode ML. Since the threshold voltage of the freewheeling diode ML is relatively small compared to the input voltage VIN, therefore... Figure 3 The voltage V is not visible in the middle. LXS A slight rise. At time T1, the lower transistor control signal LG flips to a low level, thereby controlling the freewheeling transistor ML to turn off. After the conduction delay of inductor L, at time T2, the voltage V at node LX... LXS It begins to gradually increase. When the reverse inductor current IL is large, the reverse inductor current IL can discharge to the input voltage terminal VIN through the body diode of the power transistor MH, thereby increasing the voltage V at node LX. LXS The voltage rises above the input voltage VIN. In this case, the voltage V... LXS The waveform is shown in curve 31. If the reverse inductance current IL is small, only the overshoot caused by the reverse inductance current IL charging the parasitic capacitance at node LX is observed. In this case, the voltage V LXS The waveform is shown in curve 32 or curve 33. Curves 32 and 33 are used to represent different upward impulse amplitudes.

[0033] In this context, a voltage V exceeding 0V LXS This can be referred to as flyback-surging.

[0034] Existing zero-crossing detection circuits for inductor current mostly detect whether the inductor current has crossed zero, without considering adaptive adjustment of the zero-crossing detection threshold. Therefore, the magnitude of the backflip voltage at node LX is highly uncertain. If existing zero-crossing detection circuits for inductor current are used, the DC-DC converter may disconnect the freewheeling diode due to the detection of reverse current, or it may trigger freewheeling during the dead time, resulting in poor freewheeling diode disconnection response. It may also disconnect the freewheeling diode before turning on the power transistor due to the transition from freewheeling to charging conduction.

[0035] To address this, this disclosure proposes an inductor current detection circuit for a DC-DC converter. It assesses the presence of reverse inductor current when the freewheeling diode is disconnected by utilizing the magnitude of the recoil voltage that may occur during freewheeling diode disconnection. Furthermore, it adaptively adjusts the current detection threshold using the recoil voltage within the dead time, ensuring that the current detection threshold eventually converges to a target value. The target value can be zero current or a target reverse current (negative current). Correspondingly, the recoil voltage also converges to the target voltage value. The converged, stable recoil voltage improves the freewheeling diode's open-circuit response (meaning that freewheeling is not triggered within the dead time when reverse current is present). If the current detection threshold eventually converges to a negative value, the converged recoil voltage, after charging the parasitic capacitance at node LX, reduces the voltage drop required to turn on the power transistor, thus improving output voltage stability.

[0036] Figure 4 A schematic block diagram of an inductor current sensing circuit 400 for a DC-DC converter according to an embodiment of the present disclosure is shown. In some embodiments of the present disclosure, the DC-DC converter operates in discontinuous switching mode (DCM). Figure 4 The example illustrates a power transistor MH, a freewheeling transistor ML, and an inductor L in a DC-DC converter. The input of an inductor current sensing circuit 400 is coupled to node LX of the DC-DC converter. This inductor current sensing circuit 400 includes a switching circuit 410, a first control circuit 420, a second control circuit 430, and an output circuit 440.

[0037] The first terminal of the switching 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 switching 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 switching circuit 410 is configured to: during the period when the first control signal Cr1 is at an active level, reduce the voltage V at the first terminal of the inductor L of the DC-DC converter. LXS The signal is transmitted to the first node N1. The first terminal of the inductor L is directly coupled to the second terminal of the freewheeling diode ML of the DC-DC converter. The first control signal Cr1 is at an active level during the freewheeling period when the freewheeling diode ML is conducting and during the dead time immediately following the freewheeling period.

[0038] In some embodiments of this disclosure, the first control signal Cr1 may be generated based on the upper MOSFET control signal HG and the lower MOSFET control signal LG. The first control signal Cr1 is at an active level during the time period between the lower MOSFET control signal LG turning to an active level and the upper MOSFET control signal HG turning to an active level. The inductor current detection circuit 400 may also include circuitry for generating the first control signal Cr1.

[0039] The first terminal of the first control circuit 420 is coupled to the second terminal of the switching circuit 410 and the first terminal of the second control circuit 430 via the first node N1. The second terminal of the first control circuit 420 is coupled to the input terminal of the output circuit 440 and the second terminal of the second control circuit 430 via the second node N2. The first control circuit 420 is configured to generate a voltage difference equal to a first increment value between the second node N2 and the first node N1. When the first node N1 is not floating (i.e., during the period when the first control signal Cr1 is at an active level), the first increment value is greater than 0V.

[0040] The first terminal of the second control circuit 430 is coupled to the second terminal of the switching circuit 410 and the first terminal of the first control circuit 420 via the first node N1. The 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 the second node N2. The second control circuit 430 is configured to: record a historical voltage positively correlated with the voltage of the first node N1 during the period when the second control signal Cr2 is at an active level, and generate a voltage difference equal to a second increment value between the second node N2 and the first node N1 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 increment value and the second increment value. The second control signal Cr2 is at an active level during the dead time. Therefore, the second control circuit 430 can record the relevant voltage information of the node LX during the dead time. In some embodiments of this disclosure, when the historical voltage is greater than 0V, the second increment value is greater than 0V. When the historical voltage is equal to or less than 0V, the second increment value is equal to 0V.

[0041] In some embodiments of this disclosure, the second control signal Cr2 may be generated based on the upper MOSFET control signal HG and the lower MOSFET control signal LG. The second control signal Cr2 is at an active level during the time period between the lower MOSFET control signal LG turning to an inactive level and the upper MOSFET control signal HG turning to an active level. The inductor current detection circuit 400 may also include circuitry for generating the second control signal Cr2.

[0042] Output circuit 440 is coupled to the second terminal of first control circuit 420 and the second terminal of second control circuit 430 via second node N2. The output terminal of output circuit 440 serves as the signal output terminal of inductor current detection circuit 400. Output circuit 440 is configured to generate a reverse current detection signal RCD based on the voltage of second node N2 and output the reverse current detection signal RCD from the signal output terminal of inductor current detection circuit 400. The reverse current detection signal RCD is at an invalid level when the voltage of second node N2 is below the flip-flop threshold. The reverse current detection signal RCD flips to an active level when the voltage of second node N2 rises to the flip-flop threshold to turn off the freewheeling diode ML. In practical applications, the flip-flop threshold can be a fixed voltage value set according to the target backflush voltage, the first increment value, and the second increment value. The target backflush voltage is the voltage V at the first terminal of inductor L when the inductor current flowing through inductor L equals the target reverse current during the freewheeling period when freewheeling diode ML is conducting. LXS Here, the second incremental value used to set the switching threshold is positively correlated with the recoil voltage of the cycle preceding the occurrence of the target recoil voltage. In this context, "cycle" refers to the switching cycle of the DC-DC converter.

[0043] When the DC-DC converter using the inductor current detection circuit 400 does not exhibit reverse inductor current IL (the direction of inductor current IL is...) Figure 4 (The arrows in the image point indicate the same direction). Under the control of a pulse width modulation (PWM) signal (not shown), the lower tube control signal LG controls the freewheeling tube ML to turn on and off according to a preset duty cycle.

[0044] Assume that in the nth cycle, the DC-DC converter using the inductor current detection circuit 400 experiences a reverse inductor current IL (the direction of the inductor current IL is opposite to that of the DC-DC converter). Figure 4 (The arrows in the diagram indicate opposite directions). Therefore, during the conduction of the freewheeling diode ML, the voltage V at node LX is... LXS A slight voltage rise (not exceeding the threshold voltage of the freewheeling diode ML). Switching circuit 410 will increase voltage V. LXS The voltage difference is transmitted to the first node N1. The first control circuit 420 can generate a voltage difference equal to the first increment value between the second node N2 and the first node N1. If the historical voltage recorded by the second control circuit 430 is not large enough (e.g., the recoil voltage in the previous cycle (n-1 cycle) was small, or no recoil voltage occurred), then the voltage difference equal to the second increment value generated by the second control circuit 430 between the second node N2 and the first node N1 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 increment value and the second increment value, the recoil voltage V at node LX is small. LXSThe voltage at node N2 cannot be pushed up above the toggling threshold; therefore, the reverse current detection signal RCD will not toggle to an active level. (Reference) Figure 3 After the freewheeling diode ML is disconnected, the backflush voltage V LXS The rise can be significantly increased. At this point, the recoil voltage V... LXS The voltage can be supplied 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+1)th cycle).

[0045] In the next cycle (the (n+1)th cycle), if the reverse inductor current IL still occurs, due to the large historical voltage, the second incremental value will also be large, resulting in a larger recoil voltage V. LXS The voltage at node N2 can be pushed up to exceed the switching threshold without needing to reach the value of the previous cycle (cycle n). At this point, the reverse current detection signal RCD flips to an active level, causing the lower transistor control signal LG to flip to an inactive level earlier, thus turning off the freewheeling transistor ML earlier. Consequently, the reverse inductor current IL in the next cycle (cycle n+2) will decrease accordingly, thereby reducing the recoil voltage V. LXS Reduced. By setting the recoil voltage V during the dead time. LXS The transfer coefficient between the historical voltage and the recoil voltage V recorded by the second control circuit 430 (historical voltage and recoil voltage V) LXS The ratio of the reverse inductor current IL to the recoil voltage V can cause the reverse inductor current IL to gradually converge. LXS It gradually converges and eventually reaches stability. Here, the transfer coefficient should be set to less than 1. Furthermore, by setting the flip threshold, the recoil voltage V can be made more stable. LXS The current eventually converges to the target recoil voltage, thus causing the reverse inductor current IL to eventually converge to the target reverse current. The target recoil voltage and target reverse current can be determined based on the specific application.

[0046] Figure 5 An exemplary circuit diagram of an inductor current detection circuit 500 for a DC-DC converter according to an embodiment of the present disclosure is shown. Figure 5 In the example, the effective level of the reverse current detection signal RCD is high. 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 is 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 transistor 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 a signal output terminal.

[0047] exist Figure 5 In the example, the first control circuit 520 includes a second constant current source CC2 and a second transistor M2. The second constant current source CC2 is 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 the second node N2 and the output terminal of the second constant current source CC2. The first electrode of the second transistor M2 is coupled to the first node N1.

[0048] In some embodiments of this disclosure, the second transistor M2 has the same dimensions as the first transistor M1.

[0049] exist Figure 5 In the example, the second control circuit 530 includes: a first switch S1, a third transistor M3, and a capacitor C. The controlled terminal of the first switch S1 is provided with a second control signal Cr2. The first terminal of the first switch S1 is coupled to a first node N1. The second terminal of the first switch S1 is coupled to the first terminal of the capacitor C and the control terminal of the third transistor M3. The second terminal of the capacitor C is coupled to the first terminal of the first transistor M1. The first terminal of the third transistor M3 is coupled to a second node N2. The second terminal of the third transistor M3 is coupled to a first voltage terminal V1.

[0050] In some embodiments of this disclosure, the first switch S1 can be implemented by a transistor. For ease of reference, this transistor is referred to as the fourth transistor. The control electrode of the fourth transistor is provided with a second control signal Cr2. The first electrode of the fourth transistor is coupled to the first terminal of capacitor C and the control electrode of the third transistor M3. The second electrode of the fourth transistor is coupled to the first node N1. The recoil voltage V during the dead time... LXS The transfer coefficient of the historical voltage recorded by the second control circuit 430 can be set by the internal resistance of the fourth transistor.

[0051] exist Figure 5 In the example, the switching circuit 510 includes a second switch S2. The controlled terminal of the second switch S2 is provided with a first control signal Cr1. The first terminal of the second switch S2 is coupled to a first node N1. The second terminal of the second switch S2 is directly coupled to the first terminal of the inductor L of the DC-DC converter and the second terminal of the freewheeling diode ML (i.e., node LX).

[0052] Figure 6 An exemplary circuit diagram of an inductor current detection circuit 600 for a DC-DC converter according to an embodiment of the present disclosure is shown. Figure 6 The output circuit 640 and the first control circuit 620 are Figure 5 A variation of the output circuit 540 and the first control circuit 520. Figure 6In the example, the effective level of the reverse current detection signal RCD is low. The output circuit 640 includes a first constant current source CC1 and a first transistor M1. The first constant current source CC1 is 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 transistor ML. The second electrode of the first transistor M1 is coupled to the output terminal of the first constant current source CC1 and the signal output terminal.

[0053] exist Figure 6 In the example, the first control circuit 620 includes a second constant current source CC2 and a diode D. The second constant current source CC2 is 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.

[0054] In some embodiments of this disclosure, the threshold voltage of diode D is equal to the threshold voltage of the first transistor M1.

[0055] exist Figure 5 and Figure 6 In the example, 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 can 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, based on the above inventive concept... Figure 5 and Figure 6 Any modifications to the circuit shown should also fall within the scope of this disclosure. In such modifications, the transistor and voltage terminals may also have the same characteristics as described above. Figure 5 and Figure 6 The examples shown have different settings.

[0056] The following is combined with Figure 5 The following example illustrates the operation of the inductor current detection circuit 500 according to an embodiment of the present disclosure.

[0057] When the DC-DC converter using the inductor current detection circuit 500 does not exhibit reverse inductor current IL (the direction of inductor current IL is...) Figure 5 (The arrows in the image point indicate the same direction). Under the control of the PWM signal (not shown), the lower tube control signal LG controls the freewheeling tube ML to turn on and off according to the preset duty cycle.

[0058] Assume that in the nth cycle, the DC-DC converter using the inductor current detection circuit 500 experiences a reverse inductor current IL (the direction of the inductor current IL is opposite to that of the DC-DC converter). Figure 5(The arrows in the diagram indicate opposite directions). Therefore, during the conduction of the freewheeling diode ML, the voltage V at node LX is... LXS A slight voltage rise (not exceeding the threshold voltage of the freewheeling diode ML). At this time, the first control signal Cr1 is at an active level, the second switch closes, thereby increasing the voltage V. LXS The current 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 equal to the first increment value (equal to the threshold voltage of the second transistor M2). If the recoil voltage in the previous cycle (the (n-1)th cycle) is small, or no recoil voltage occurs, then the charge stored on capacitor C is insufficient (the historical voltage is not large enough), and the third transistor M3 is not fully turned on or is in the off state (the second increment 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 increment value and the second increment value, the recoil voltage V at node LX is... LXS The voltage at node N2 cannot be pushed up above the toggling threshold; therefore, the reverse current detection signal RCD will not toggle to an active level. From a current perspective, if the voltage V at node LX... LXS Since the first transistor M1 and the second transistor M2 are 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 an active level.

[0059] refer to Figure 3 After the freewheeling diode ML is disconnected, the backflush voltage V LXS The rise can be significantly increased. At this point, the recoil voltage V... LXS It can be supplied to the first switch S1 via the first node N1. Because the first switch S1 has internal resistance, the recoil voltage V... LXS After being multiplied by the transfer factor, the current is stored at the first terminal of capacitor C for use in the next cycle (the (n+1)th cycle). At this time, since the freewheeling diode ML is already off, even if the reverse current detection signal RCD flips to an active level, it will not affect the normal operation of the DC-DC converter.

[0060] In the next cycle (the (n+1)th cycle), if the reverse inductor current IL still occurs, because the voltage at the first terminal of capacitor C (historical voltage) is relatively large, the voltage at the second node N2 is pulled up accordingly (the second increment is the historical voltage minus the gate-source voltage of the third transistor), and the recoil voltage V... LXSThe voltage at node N2 can be pushed up to exceed the switching threshold without needing to reach the value of the previous cycle (cycle n). At this point, the reverse current detection signal RCD flips to an active level, causing the lower transistor control signal LG to flip to an inactive level earlier, thus turning off the freewheeling transistor ML earlier. Consequently, the reverse inductor current IL in the next cycle (cycle n+2) will decrease accordingly, thereby reducing the recoil voltage V. LXS Reduce. By appropriately setting the internal resistance value of the first switch S1, the reverse inductor current IL can be gradually reduced, and the recoil voltage V... LXS It gradually converges and eventually reaches stability. Here, the internal resistance of the first switch S1 is set such that the transfer coefficient is less than 1. Furthermore, by setting the flip threshold, the recoil voltage V can be adjusted. LXS The current eventually converges to the target recoil voltage, thus causing the reverse inductor current IL to eventually converge to the target reverse current. The target recoil voltage and target reverse current can be determined based on the specific application.

[0061] Figure 6 The working process of the inductor current detection circuit 600 in the middle and Figure 5 The operation of the inductor current detection circuit 500 is similar and will not be described in detail here. It should be noted that... Figure 6 In this process, by using diode D, a voltage difference of the first incremental value can also be generated between the second node N2 and the first node N1. Figure 6 Diode D in the diagram can be used to replace... Figure 5 The second transistor M2 in the process.

[0062] Embodiments of this disclosure also provide a chip. This chip includes a DC-DC converter according to embodiments of this disclosure. This chip is, for example, a power management chip.

[0063] Embodiments of this disclosure also provide an electronic device. This electronic device includes a chip according to embodiments of this disclosure. The electronic device is, for example, a smart terminal device, such as a tablet computer or smartphone.

[0064] In summary, the inductor current detection circuit for a DC-DC converter according to embodiments of this disclosure adaptively adjusts the inductor current detection threshold using the recoil voltage during the dead time. This causes the inductor current value when the reverse current detection signal flips to an effective level to gradually converge and eventually stabilize. Consequently, the recoil voltage also gradually converges and eventually stabilizes. The converged and stable recoil voltage improves the freewheeling diode's open-circuit response (meaning that the freewheeling diode is not triggered during the dead time when reverse current is present). If the current detection threshold eventually converges to a negative value, the converged recoil voltage, after charging the parasitic capacitance at node LX, reduces the voltage drop required to turn on the power transistor, thus improving output voltage stability. Accordingly, the DC-DC converter employing the inductor current detection circuit according to embodiments of this disclosure also possesses the aforementioned advantages.

[0065] Unless otherwise expressly indicated by the context, the singular form of words used herein and in the appended claims includes the plural form, and vice versa. Thus, when referring to the singular, the plural form of the corresponding term is generally included. Similarly, the terms “comprising” and “including” shall be interpreted as including rather than exclusively. Likewise, the terms “including” and “or” shall be interpreted as including unless such interpretation is expressly prohibited herein. Where the term “example” is used herein, particularly when it follows a set of terms, the “example” is merely exemplary and illustrative and should not be considered exclusive or extensive.

[0066] Further aspects and scope of adaptation become apparent from the description provided herein. It should be understood that various aspects of this application may be implemented individually or in combination with one or more other aspects. It should also be understood that the descriptions and specific embodiments herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0067] Several embodiments of this disclosure have been described in detail above. However, it is obvious that those skilled in the art can make various modifications and variations to the embodiments of this disclosure without departing from the spirit and scope of this disclosure. The scope of protection of this disclosure is defined by the appended claims.

Claims

1. An inductor current detection circuit for a DC-DC converter, comprising: Switching circuit, first control circuit, second control circuit, output circuit. The switching circuit is configured to transfer the voltage at the first terminal of the inductor of the DC-DC converter to the first node during the period when the first control signal is at an effective level. The first terminal of the inductor is directly coupled to the second terminal of the freewheeling diode of the DC-DC converter. The first control signal is at the effective level during the freewheeling period when the freewheeling diode is turned on and during the dead time immediately following the freewheeling period. The first control circuit is configured to generate a voltage difference equal to a first increment value between the second node and the first node; The second control circuit is configured to: record a historical voltage 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, such 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, wherein the second control signal is at the active level during the dead time; The output circuit is configured to generate a reverse current detection signal based on the voltage of the second node and output the reverse current detection signal from the signal output terminal of the inductor current detection circuit. The reverse current detection signal flips to an active level when the voltage of the second node rises to a flip threshold to turn off the freewheeling diode.

2. The inductor current detection circuit according to claim 1, wherein, The effective level of the reverse current detection signal is high, and 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 terminal of the first transistor is coupled to the second node, the first terminal of the first transistor is coupled to the first terminal of the freewheeling diode, and the second terminal of the first transistor is coupled to the output terminal of the first constant current source and the input terminal 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 low, and 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, and the second electrode of the first transistor is coupled to the output terminal of the first constant current source and the signal output terminal.

4. The inductor current detection circuit according to claim 2 or 3, wherein, 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, wherein the second constant current is less than the first constant current. The control electrode and the second electrode of the second transistor are coupled to the output terminal of the second node and the second constant current source, and the first electrode of the second transistor is coupled to the first node.

5. The inductor current detection circuit according to claim 4, wherein, The second transistor has the same dimensions as 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 and a diode. The second constant current source is configured to output a second constant current, wherein the second constant current is 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.

7. The inductor current detection circuit according to claim 6, wherein, The threshold voltage of the diode is equal to the 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 controlled terminal of the first switch is provided with the second control signal, the first terminal of the first switch is coupled to the first node, and the second terminal of the first switch is coupled to the first terminal of the capacitor and the control electrode of the third transistor. The second terminal of the capacitor is coupled to the first terminal of the first transistor; The first terminal of the third transistor is coupled to the second node, and the second terminal of the third transistor is coupled to the first voltage terminal.

9. An inductor current detection circuit for a DC-DC converter, comprising: First transistor, second transistor, third transistor, first constant current source, second constant current source, capacitor, first switch, second switch, inverter. The first constant current source is configured to output a first constant current; The control terminal of the first transistor is coupled to the control terminal and the second terminal of the second transistor; the first terminal of the first transistor is coupled to the first terminal of the freewheeling diode of the DC-DC converter; and the second terminal of the first transistor is coupled to the output terminal of the first constant current source and the input terminal of the inverter. The output terminal of the inverter is coupled to the signal output terminal of the inductor current detection circuit, and a reverse current detection signal is output from the signal output terminal. The effective level of the reverse current detection signal is used to turn off the freewheeling diode. The second constant current source is configured to output a second constant current, wherein the second constant current is less than the first constant current; The control electrode of the second transistor is coupled to the output terminal 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 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, and the second terminal of the second switch is coupled to the first terminal of the inductor of the DC-DC converter and the second terminal of the freewheeling diode. The first control signal is at an active level during the freewheeling period when the freewheeling diode is turned on and during the dead time immediately following the freewheeling period. The controlled terminal of the first switch is provided with a second control signal, the second terminal of the first switch is coupled to the first terminal of the capacitor and the control electrode of the third transistor, and the second control signal is at an active level during the dead time; The second terminal of the capacitor is coupled to the first terminal of the first transistor; The second terminal of the third transistor is coupled to the first voltage terminal.

10. A DC-DC converter, the DC-DC converter comprising: The inductor current detection circuit according to any one of claims 1 to 9.

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