Voltage converter, control method and voltage conversion device

Abstract

The invention provides a voltage converter, a control method and a voltage conversion device. The voltage converter includes a voltage threshold generation circuit, a comparison circuit, a controller, a driving circuit, a high-side switch, and a low-side switch. The voltage threshold generation circuit outputs a first threshold voltage as a comparison threshold voltage. The comparison circuit is used for outputting a comparison signal according to a comparison result of the comparison threshold voltage and the output voltage. The controller is used for outputting a timing signal according to the comparison signal. The driving circuit is used for correspondingly controlling the high-side switch and the low-side switch to be switched on or switched off according to the enable signal, the comparison signal and the timing signal. Therefore, according to the voltage converter, the control method and the voltage conversion device provided by the invention, the high-side switch and the low-side switch can be switched on or switched off at regular time according to the negative current threshold value, so that the power switch tube is prevented from being damaged due to overlarge negative current, and the output voltage of the voltage conversion device is enabled to return to a reference voltage level.

Description

Technical Field

[0001] The present application relates to the field of voltage converters, and in particular, to a voltage converter, a control method and a voltage conversion device. Background Art

[0002] The voltage conversion device includes a voltage converter, an output inductor, and an output capacitor. The voltage converter usually includes a half-bridge circuit and a driver circuit. The half-bridge circuit includes a high-side switch and a low-side switch. The connection point between the high-side switch and the low-side switch outputs current to supply power to the load through the energy storage inductor. The driver circuit controls the on and off of the high-side switch and the low-side switch respectively. However, due to the sudden decrease in load and the influence of the synchronous rectification mode, the driver circuit controls the low-side switch to be continuously turned on. At this time, the inductor current flowing through the energy storage inductor will drop rapidly, and the output voltage of the voltage converter will rise accordingly and exceed the reference voltage value, which is also called overshoot.

[0003] When the inductor current drops to zero and turns to negative current, the negative current will generate a large voltage on the low-side switch. This voltage may exceed the maximum withstand voltage value specified in the safe operating area (SOA) of the low-side switch, which may cause damage to the low-side switch.

[0004] To prevent the absolute value of the negative current from increasing without limit, when the negative current reaches the negative current threshold, the drive circuit can control both the high-side switch and the low-side switch to be disconnected, so that the inductor current becomes zero, reducing the adverse effect of the negative current on the low-side switch. However, the output voltage of the voltage converter is still in an overshoot state and cannot be restored to the reference voltage.

[0005] For example, Figure 1 As shown, IL is the current of the energy storage inductor in the voltage converter, and Vout is the output voltage of the voltage conversion device. At T1-T2, the high-side switch and the low-side switch are continuously turned on or off according to the normal working principle of the voltage converter, IL is stably maintained at the level of the reference current Iref, and Vout is stably maintained at the level of the reference voltage Vref.

[0006] At the moment T2-T3, the high-side switch is continuously disconnected and the low-side switch is continuously turned on. At this time, IL drops rapidly. Due to the back electromotive force of the energy storage inductor, Vout will rise accordingly and cause overshoot.

[0007] At time T3-T4, IL turns to negative current, and the absolute value of the negative current becomes larger and larger. At time T4, the low-side switch is turned off. In order to keep IL continuous, IL flows through the body diode of the high-side switch until IL becomes zero. However, Vout does not return to Vref. Summary of the invention

[0008] The present application provides a voltage converter, a control method and a voltage conversion device, which can time the high-side switch and the low-side switch to be turned on or off according to the negative current threshold, thereby preventing the power switch tube from being damaged due to excessive negative current, and allowing the output voltage of the voltage conversion device to return to a reference voltage level.

[0009] In a first aspect, the present application provides a voltage converter. The voltage converter includes a half-bridge circuit and a control circuit, the half-bridge circuit includes a high-side switch and a low-side switch, and the control circuit includes a voltage threshold generation circuit, a comparison circuit, a controller and a drive circuit. The voltage threshold generation circuit includes a first voltage threshold generation circuit, the first voltage threshold generation circuit includes a limiting current source and a tracking circuit, the limiting current source is connected in series with the tracking circuit, the equivalent resistance value of the tracking circuit is proportional to the equivalent resistance value of the low-side switch, the output current of the limiting current source is proportional to the preset negative current threshold, and the output end of the first voltage threshold generation circuit outputs a first threshold voltage as a comparison threshold voltage. The comparison circuit is used to receive the comparison threshold voltage and the output voltage of the voltage converter, and output a comparison signal according to the comparison result of the comparison threshold voltage and the output voltage. The controller is used to receive the comparison signal and output a timing signal according to the comparison signal. The drive circuit is used to control the high-side switch and the low-side switch to be turned on or off according to the enable signal, the comparison signal and the timing signal.

[0010] In combination with the first aspect, in a possible implementation manner, the tracking circuit includes at least one tracking power tube, and the type of each tracking power tube is the same as that of the low-side switch.

[0011] In combination with the first aspect, in one possible implementation, the comparison signal has a first state and a second state, and the comparison signal is output according to the comparison result of the comparison threshold voltage and the output voltage, including: when the comparison threshold voltage is less than the output voltage, the comparison circuit outputs the comparison signal of the first state, otherwise it outputs the comparison signal of the second state.

[0012] In combination with the first aspect, in a possible implementation, the timing signal has a first state and a second state, and the timing signal is output according to the comparison signal, including: when a comparison signal of the first state is received, the controller outputs the timing signal of the first state, and after a preset current limiting time, the timing signal is switched to the second state.

[0013] In combination with the first aspect, in a possible implementation, the enable signal has a first state, and according to the enable signal, the comparison signal and the timing signal, the high-side switch and the low-side switch are controlled to be turned on or off, including: when the enable signal of the first state, the comparison signal of the second state, and the timing signal of the second state are received, the low-side switch is driven to be turned on. When the enable signal of the first state and the timing signal of the first state are received, the high-side switch and the low-side switch are driven to be turned off.

[0014] In combination with the first aspect, in a possible implementation, the enable signal also has a second state, the voltage threshold generation circuit also includes a negative current control switch and a zero current control switch, one end of the zero current control switch receives the second threshold voltage, the other end of the zero current control switch is electrically connected to the input end of the comparison circuit, and the two ends of the negative current control switch are respectively electrically connected to the output end of the limiting current source and the input end of the comparison circuit. In response to the enable signal of the first state, the negative current control switch is turned on, the zero current control switch is turned off, and the voltage threshold generation circuit outputs the first threshold voltage as the comparison threshold voltage. In response to the enable signal of the second state, the negative current control switch is turned off, the zero current control switch is turned on, and the voltage threshold generation circuit outputs the second threshold voltage as the comparison threshold voltage.

[0015] In combination with the first aspect, in a possible implementation, the driving circuit is used to control the high-side switch and the low-side switch to be turned on or off according to the enable signal and the comparison signal of the second state. When the enable signal of the second state and the comparison signal of the first state are received, the low-side switch is driven to be turned off.

[0016] In combination with the first aspect, in a possible implementation, the comparison circuit includes a comparator and an offset compensation circuit, the offset compensation circuit includes a multiplexer and an offset control circuit, the first input end of the comparator receives the output voltage of the voltage converter, the second input end of the comparator is electrically connected to the output end of the multiplexer, the output end of the comparator is electrically connected to the offset compensation circuit, and the offset compensation circuit is also electrically connected to the control end of the multiplexer. The multiplexer includes at least one input switch, each input switch is used to receive a comparison threshold voltage, and is used to reduce the offset of the comparison threshold voltage, and different input switches correspondingly reduce different offsets. The offset compensation circuit is used to control the conduction or disconnection of at least one input switch in sequence according to the state of the comparison signal to adjust the offset of the comparison threshold voltage.

[0017] In a second aspect, the present application provides a control method for a voltage converter. The control method is applied to a voltage converter in any possible implementation of the first aspect, and the control method includes: generating a first threshold voltage according to a preset negative current threshold. When the enable signal is in a first state, a first threshold voltage is generated as a comparison threshold voltage, and when the enable signal is in a second state, a second threshold voltage is generated as a comparison threshold voltage, wherein the second threshold voltage is zero voltage. The comparison threshold voltage and the output voltage are compared to generate a comparison signal. According to the comparison signal and the enable signal, the high-side switch and the low-side switch are controlled to be turned on or off accordingly.

[0018] In combination with the second aspect, in a possible implementation, according to the comparison signal and the enable signal, the high-side switch and the low-side switch are controlled to be turned on or off, including: when the enable signal is in the first state and the comparison signal is in the first state, a timing signal of the first state is generated, and after a preset current limiting time, the timing signal generated is replaced with the timing signal of the second state. In response to the enable signal of the first state and the timing signal of the first state, the low-side switch and the high-side switch are controlled to be turned off. In response to the enable signal of the first state and the timing signal of the second state, the low-side switch is controlled to be turned on. In response to the enable signal of the second state and the comparison signal of the first state, the low-side switch is controlled to be turned off.

[0019] In combination with the second aspect, in a possible implementation manner, the control method further includes: adjusting an offset of the comparison threshold voltage according to a state of the comparison signal.

[0020] In a third aspect, the present application provides a voltage conversion device, including an output inductor, an output capacitor, and a voltage converter as in any possible implementation of the first aspect, wherein one end of the output inductor is electrically connected to the output end of the voltage converter, the other end of the output inductor is electrically connected to one end of the output capacitor, and the other end of the output inductor is used to electrically connect to a load. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 FIG. 4 is a timing diagram of the inductor current and the output voltage of the voltage conversion device.

[0022] Figure 2 A schematic diagram of a voltage conversion device provided in one embodiment of the present application.

[0023] Figure 3 A schematic diagram of a control circuit provided in accordance with an embodiment of the present application.

[0024] Figure 4 A signal timing diagram of a voltage conversion device provided in one embodiment of the present application.

[0025] Figure 5 Another signal timing diagram of a voltage conversion device provided in an embodiment of the present application.

[0026] Figure 6 A schematic diagram of the power conversion efficiency of a voltage converter provided according to an embodiment of the present application.

[0027] Figure 7 A schematic diagram of a comparison circuit provided according to an embodiment of the present application.

[0028] Figure 8 A schematic diagram of the difference between the offsets OFF1 to OFF8 provided in an embodiment of the present application.

[0029] Fig. 9 A schematic diagram of a comparison error of a comparison circuit provided in an embodiment of the present application.

[0030] Fig.10 A schematic diagram of a voltage converter implementing a DVS function according to an embodiment of the present application.

[0031] Fig.11 A flow chart of a control method for a voltage converter provided in an embodiment of the present application.

[0032] Main component symbols 10-voltage converter; 100-control circuit; 11-half-bridge circuit; 12-drive circuit; L1-output inductor; C1-output capacitor; M1-high-side switch; M2-low-side switch; M3-following power tube; 131-voltage threshold generation circuit; 132-comparison circuit; 133-controller; ILIM-limiting current source; 1311-following circuit; S1-negative current control switch; S2-zero current control switch; 1321-comparator; 1322-offset compensation circuit; OFS1-OFS8-input switches; MUX-multiplexer. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application.

[0034] It is understandable that the connection relationship described in this application refers to direct or indirect connection. For example, the connection between A and B can be either a direct connection between A and B or an indirect connection between A and B through one or more other electrical components. For example, A and C can be directly connected, and C and B can be directly connected, so that A and B are connected through C. It is also understandable that the "A connects B" described in this application can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0035] In the description of this application, unless otherwise specified, " / " means "or", for example, A / B can mean A or B. "And / or" in this article is only a way to describe the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0036] In the description of this application, words such as "first" and "second" are only used to distinguish different objects, and do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit differences. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0037] See also Figure 2 , Figure 2 Schematic diagram of a voltage conversion device provided in an embodiment of the present application. The voltage conversion device includes a voltage converter 10, an output inductor L1 and an output capacitor C1. The voltage converter 10 includes a half-bridge circuit 11 and a control circuit 100. The half-bridge circuit 11 includes a high-side switch M1 and a low-side switch M2.

[0038] The first end of the high-side switch M1 receives the input voltage VIN, and the second end of the high-side switch M1, the first end of the low-side switch M2, and one end of the output inductor L1 are electrically connected to the output end LX of the voltage converter 10. The other end of the output inductor L1 is the output end of the voltage conversion device. The output end voltage of the voltage conversion device is the output voltage Vout, and the output end of the voltage conversion device is also electrically connected to one end of the output capacitor C1 and the load ( Figure 1 (not shown), the other end of the output capacitor C1 is grounded.

[0039] Here, an example is given in which the positive direction of the inductor current IL flows out from the output terminal LX of the voltage converter 10, and the negative direction of the inductor current IL flows into the output terminal LX of the voltage converter 10. That is, when the inductor current IL is a positive current, the inductor current IL flows out from the output terminal LX of the voltage converter 10 to the output inductor L1, and when the inductor current IL is a negative current, the inductor current IL flows from the output inductor L1 to the output terminal LX of the voltage converter 10.

[0040] The second end of the low-side switch M2 is grounded. The third end of the high-side switch M1 and the third end of the low-side switch M2 are both electrically connected to the control circuit 100 .

[0041] The control circuit 100 is used to output a high-side drive signal UG and a low-side drive signal LG according to a switch cycle signal TON, so that the high-side switch M1 and the low-side switch M2 are normally turned on or off within a switch cycle, that is, the high-side switch M1 and the low-side switch M2 operate normally within a switch cycle. TON can be generated by the control circuit 100, and TON can be a pulse width modulation (PWM) signal.

[0042] The control circuit 100 is also used to receive an enable signal NLIM_EN, and output a drive signal to the third end of the high-side switch M1 and the third end of the low-side switch M2 according to the enable signal NLIM_EN. Wherein, the drive signal includes a high-side drive signal UG and a low-side drive signal LG, and the high-side drive signal UG is used to control the on-off of the high-side switch M1. The low-side drive signal LG is used to control the on-off of the low-side switch M2. Specifically, the high-side drive signal UG has a first state and a second state, and the first state of the high-side drive signal UG is used to control the high-side switch M1 to be disconnected, and the second state of the high-side drive signal UG is used to control the high-side switch M1 to be turned on. The low-side drive signal LG has a first state and a second state, and the first state of the low-side drive signal LG is used to control the low-side switch M2 to be turned on, and the second state of the low-side drive signal LG is used to control the low-side switch M2 to be disconnected.

[0043] In some embodiments, the enable signal NLIM_EN can be controlled by the enable unit ( Figure 2 The control enable unit may include a voltage comparator, a digital controller, and an operation trigger circuit. For example, the control enable unit may generate the enable signal NLIM_EN by at least the following methods and combinations thereof.

[0044] The control enable unit can output a corresponding enable signal NLIM_EN to adjust the output voltage Vout according to the comparison result between the output voltage Vout, the overvoltage threshold Vovp, and the reference voltage Vref. For example, when the output voltage Vout exceeds the overvoltage threshold Vovp, the control enable unit can output a corresponding enable signal NLIM_EN, so that the output voltage Vout is quickly reduced to a level less than the overvoltage threshold Vovp. For another example, when the output voltage Vout overshoots and exceeds the reference voltage Vref, the control enable unit can output a corresponding enable signal NLIM_EN, so that the output voltage Vout is restored to the level of the reference voltage Vref. Among them, the comparison result between the output voltage Vout, the overvoltage threshold Vovp, and the reference voltage Vref can be achieved by a voltage comparator.

[0045] The control enable unit can also output a corresponding enable signal NLIM_EN in response to an operation instruction from outside the voltage converter 10. The operation trigger circuit can receive an operation instruction from outside the voltage converter 10 and output an enable signal NLIM_EN according to the operation instruction from outside the voltage converter 10.

[0046] The control enable unit can also output a corresponding enable signal NLIM_EN in response to a drop in the reference voltage Vref, so that the output voltage Vout quickly follows the drop in the reference voltage Vref. The digital controller can output a corresponding enable signal NLIM_EN in response to a drop in the reference voltage Vref.

[0047] In some embodiments, the high-side switch M1 is a PMOS tube, and accordingly, the first end of the high-side switch M1 is a source, the second end of the high-side switch M1 is a drain, and the third end of the high-side switch M1 is a gate.

[0048] In some embodiments, the low-side switch M2 is an NMOS tube, and correspondingly, the first end of the low-side switch M2 is a drain, the second end of the low-side switch M2 is a source, and the third end of the low-side switch M2 is a gate.

[0049] See also Figure 3 , Figure 3 Schematic diagram of a control circuit 100 provided in an embodiment of the present application. The control circuit 100 includes a voltage threshold generating circuit 131, a comparison circuit 132, a controller 133, and a driving circuit 12. The voltage threshold generating circuit 131 includes a first threshold voltage generating circuit, a negative current control switch S1, and a zero current control switch S2. The first threshold voltage generating circuit includes a limiting current source ILIM and a tracking circuit 1311. The tracking circuit 1311 includes at least one tracking power tube M3.

[0050] Here, the tracking circuit 1311 includes two tracking power tubes M3 as an example for description, but the present application does not impose any limitation on the number of tracking power tubes M3. When the number of tracking power tubes M3 is greater than 2, the connection relationship and working principle between the multiple tracking power tubes M3 can refer to the embodiment of two tracking power tubes M3, which will not be repeated here.

[0051] The two tracking power tubes M3 are connected in series. Specifically, the first end of one of the tracking power tubes M3 is electrically connected to the output end of the limiting current source ILIM, and the second end of the tracking power tube M3 is electrically connected to the first end of the other tracking power tube M3. The second end of the other tracking power tube M3 is grounded. The two tracking power tubes M3 work in the linear region, so that the limiting current source ILIM is connected in series with the tracking circuit 1311. The tracking circuit 1311 can serve as a load of the limiting current source ILIM.

[0052] The voltage at the output terminal V of the first threshold voltage generating circuit is the first threshold voltage Vt. The first threshold voltage Vt can be determined by the output current of the limiting current source ILIM and the equivalent total resistance value of the tracking circuit 1311. Specifically, according to Ohm's law, the first threshold voltage Vt is equal to the product of the output current of the limiting current source ILIM and the equivalent total resistance value of the tracking circuit 1311.

[0053] One end of the negative current control switch S1 is electrically connected to the output end of the limiting current source ILIM, and the other end of the negative current control switch S1 is electrically connected to the comparison circuit 132. The negative current control switch S1 is a controlled switch. The negative current control switch S1 can receive an enable signal NLIM_EN, and then turn on or off according to different states of the enable signal NLIM_EN. For example, the enable signal NLIM_EN has a first state and a second state. The negative current control switch S1 is turned on in response to the enable signal NLIM_EN in the first state, so that the first threshold voltage Vt is output to the comparison circuit 132 as the comparison threshold voltage Vcmp. The negative current control switch S1 is also turned off in response to the enable signal NLIM_EN in the second state.

[0054] One end of the zero current control switch S2 receives the second threshold voltage Vg, and the other end of the zero current control switch S2 is electrically connected to the comparison circuit 132 .

[0055] Among them, the zero current control switch S2 is a controlled switch. The zero current control switch S2 can receive the inverted signal of the enable signal NLIM_EN through an inverter, and then turn on or off according to the enable signal NLIM_EN. For example, the zero current control switch S2 is turned off in response to the enable signal NLIM_EN in the first state (at this time, the inverted signal of the enable signal NLIM_EN is the second state), and is turned on in response to the enable signal NLIM_EN in the second state (at this time, the inverted signal of the enable signal NLIM_EN is the first state), so that the second threshold voltage Vg is output to the comparison circuit 132 as the comparison threshold voltage Vcmp.

[0056] The comparison circuit 132 includes a first input terminal, a second input terminal and an output terminal, wherein the first input terminal of the comparison circuit 132 is used to receive the output voltage VLX of the output terminal LX of the voltage converter 10. The second input terminal of the comparison circuit 132 is electrically connected to the other end of the negative current control switch S1, and is electrically connected to the other end of the zero current control switch S2. Therefore, the second input terminal of the comparison circuit 132 is used to receive the comparison threshold voltage Vcmp output by the voltage threshold generation circuit 131. Specifically, when the negative current control switch S1 is turned on and the zero current control switch S2 is turned off, the comparison threshold voltage Vcmp is the first threshold voltage Vt, and when the zero current control switch S2 is turned on and the negative current control switch S1 is turned off, the comparison threshold voltage Vcmp is the second threshold voltage Vg. The output terminal of the comparison circuit 132 is electrically connected to the controller 133 and the drive circuit 12.

[0057] The comparison circuit 132 is used to compare the voltages of the first input terminal and the second input terminal, thereby outputting a corresponding comparison signal CMP_OUT to the controller 133 and the driving circuit 12. The comparison signal CMP_OUT has a first state and a second state. Specifically, when the voltage of the first input terminal is greater than or equal to the voltage of the second input terminal, the comparison circuit 132 outputs the comparison signal CMP_OUT of the first state. Otherwise, the comparison circuit 132 outputs the comparison signal CMP_OUT of the second state.

[0058] The controller 133 is used to respond to the comparison signal CMP_OUT in the first state and output the timing signal NI_NLIM to the driving circuit 12. The timing signal NI_NLIM has a first state and a second state. Specifically, the controller 133 responds to the comparison signal CMP_OUT in the first state and outputs the timing signal NI_NLIM in the first state, and switches to the timing signal NI_NLIM in the second state after a preset current limiting time.

[0059] In some embodiments, the preset current limiting time can be set according to the operating speed of the comparison circuit 132 .

[0060] The driving circuit 12 is used to output a high-side driving signal UG and a low-side driving signal LG according to the switching cycle signal TON, so that the high-side switch M1 and the low-side switch M2 are normally turned on or off within a switching cycle, that is, the high-side switch M1 and the low-side switch M2 operate normally within a switching cycle.

[0061] The driving circuit 12 is further configured to output a high-side driving signal UG and a low-side driving signal LG correspondingly according to the enable signal NLIM_EN, the comparison signal CMP_OUT, and the timing signal NI_NLIM.

[0062] The working principle of the voltage converter 10 when it works in the negative current mode is described below. When the voltage converter 10 works in the negative current mode, the enable signal NLIM_EN is in the first state.

[0063] At this time, the negative current control switch S1 is turned on, and the zero current control switch S2 is turned off. The voltage threshold generation circuit 131 is used to select the first threshold voltage Vt as the comparison threshold voltage Vcmp and output it to the comparison circuit 132 in response to the enable signal NLIM_EN in the first state.

[0064] In some embodiments, the equivalent total resistance value of the tracking circuit 1311 is proportional to the equivalent resistance value of the low-side switch M2. The output current of the limiting current source ILIM is also set proportionally to the negative current threshold It. In this way, the product of the equivalent total resistance value of the tracking circuit 1311 and the output current of the limiting current source ILIM is substantially equal to the product of the equivalent resistance value of the low-side switch M2 and the negative current threshold It. Among them, the former product is the first threshold voltage Vt, and the latter product is the drain-source voltage Vds of the low-side switch M2 when the inductor current IL flowing through the low-side switch M2 is the negative current threshold It. Therefore, the first threshold voltage Vt is substantially equal to the drain-source voltage Vds of the low-side switch M2.

[0065] The negative current threshold It can be set to be lower than the maximum current value specified by the SOA of the low-side switch M2, so that when the inductor current IL flowing through the low-side switch M2 is equal to the negative current threshold It, the low-side switch M2 is still within the SOA and the risk of damage is low.

[0066] In some embodiments, the type of the tracking power tube M3 is the same as that of the low-side switch M2. For example, the material and device of the tracking power tube M3 are the same as those of the low-side switch M2. Thus, the resistance change characteristics of the tracking power tube M3 are the same as those of the low-side switch M2. In other words, the tracking power tube M3 can follow the device characteristics of the low-side switch M2. In this way, for example, when the equivalent resistance of the low-side switch M2 varies due to factors such as process, voltage, and temperature, the equivalent resistance of the tracking power tube M3 will also vary accordingly, thereby reducing the error caused by the first threshold voltage Vt and the drain-source voltage Vds of the low-side switch M2 not being equal when the equivalent resistance of the tracking power tube M3 does not follow the variation of the equivalent resistance of the low-side switch M2 due to the variation of the equivalent resistance of the low-side switch M2.

[0067] At this time, the comparison circuit 132 compares the output voltage VLX with the first threshold voltage Vt. The drain-source voltage Vds of the low-side switch M2 is equal to the output voltage VLX. In addition, the drain-source voltage Vds of the low-side switch M2 is the product of the negative current flowing through the low-side switch M2 and the equivalent resistance of the low-side switch M2.

[0068] That is, when the negative current flowing through the low-side switch M2 is less than the negative current threshold It, the drain-source voltage Vds of the low-side switch M2 should be less than the first threshold voltage Vt. That is, at this time, the output voltage VLX should be less than the first threshold voltage Vt. Therefore, when the comparison circuit 132 compares the output voltage VLX with the first threshold voltage Vt, if the output voltage VLX is less than the first threshold voltage Vt, it means that the negative current flowing through the low-side switch M2 has not reached It, and the comparison circuit 132 outputs the comparison signal CMP_OUT of the second state to the controller 133.

[0069] When the negative current flowing through the low-side switch M2 reaches the negative current threshold It, the drain-source voltage Vds of the low-side switch M2 should be equal to the first threshold voltage Vt. That is, at this time, the output voltage VLX should be greater than or equal to the first threshold voltage Vt. Therefore, when the comparison circuit 132 compares the output voltage VLX with the first threshold voltage Vt, if the output voltage VLX is greater than or equal to the first threshold voltage Vt, it means that the negative current flowing through the low-side switch M2 reaches the negative current threshold It, and the comparison circuit 132 outputs CMP_OUT of the first state to the controller 133.

[0070] In response to the comparison signal CMP_OUT of the first state, the controller 133 outputs the timing signal NI_NLIM of the first state to the driving circuit 12. After the preset current limiting time, the controller 133 replaces the timing signal NI_NLIM of the first state with the timing signal NI_NLIM of the second state.

[0071] The driving circuit 12 responds to the enable signal NLIM_EN of the first state and the timing signal NI_NLIM of the first state, and outputs the low-side driving signal LG of the second state and the high-side driving signal UG of the first state, so as to control the low-side switch M2 and the high-side switch M1 to be disconnected. In this way, when the inductor current IL is a negative current, the negative current can flow through the body diode of the high-side switch M1, and the absolute value of the inductor current IL decreases, thereby reducing the risk of damage to the low-side switch M2 when the inductor current IL reaches the negative current threshold It.

[0072] The driving circuit 12 also responds to the enable signal NLIM_EN of the first state and the timing signal NI_NLIM of the second state, and outputs the low-side driving signal LG of the first state to control the low-side switch M2 to be turned on. In this way, when the inductor current IL is a negative current, the negative current can flow to the ground through the low-side switch M2, and the absolute value of the inductor current IL rises rapidly, and the output voltage Vout decreases accordingly, so that the overshooting output voltage Vout can return to the target level of the reference voltage Vref as soon as possible.

[0073] The comparison circuit 132 has a crossover pulse comparison characteristic. That is, the comparison circuit 132 can output a comparison signal CMP_OUT of the first state only when the voltage at the first input terminal rises to be greater than or equal to the voltage at the second input terminal. The comparison signal CMP_OUT of the first state is a pulse signal.

[0074] The following describes the working principle of the voltage converter 10 when it works in the zero current detection (ZCD) mode. When the voltage converter 10 works in the ZCD mode, the enable signal NLIM_EN is in the second state.

[0075] At this time, the zero current control switch S2 is turned on, and the negative current control switch S1 is turned off. The comparison circuit 132 receives the second threshold voltage Vg, that is, the voltage threshold generation circuit 131 is used to respond to the enable signal NLIM_EN of the second state and output the second threshold voltage Vg to the comparison circuit 132. The second threshold voltage Vg is zero voltage.

[0076] At this time, the comparison circuit 132 compares the output voltage VLX and the second threshold voltage Vg. When the inductor current IL is a positive current and the low-side switch M2 is turned on, the inductor current IL flows through the low-side switch M2 to the ground, so that the inductor current IL gradually decreases. At this time, the output voltage VLX is a negative voltage, and the output voltage VLX rises as the inductor current IL decreases. After the inductor current IL drops to zero current, the output voltage VLX rises to zero voltage accordingly. Therefore, when the comparison circuit 132 compares the output voltage VLX and the second threshold voltage Vg, based on the crossover pulse comparison characteristics of the comparison circuit 132, if the output voltage VLX is greater than or equal to the second threshold voltage Vg, it means that the inductor current IL drops to zero current, and the comparison circuit 132 outputs the comparison signal CMP_OUT of the first state to the drive circuit 12.

[0077] The driving circuit 12 responds to the enable signal NLIM_EN of the second state and the comparison signal CMP_OUT of the first state, and outputs the low-side driving signal LG of the second state to control the low-side switch M2 to be disconnected. In this way, when the inductor current IL drops to zero, the low-side switch M2 is disconnected, and the zero current switching of the low-side switch M2 can be achieved, the switching loss of the voltage converter 10 is reduced, and the energy conversion efficiency of the voltage converter 10 is improved.

[0078] Therefore, in the voltage converter 10 provided by an embodiment of the present application, one end of the negative current control switch S1 and the zero current control switch S2 are both electrically connected to the second input end of the comparison circuit 132, so that under the control of the enable signal NLIM_EN in different states, the comparison threshold voltage Vcmp received by the comparison circuit 132 is respectively a different threshold voltage. Therefore, the circuit structure of the voltage converter 10 is simple, but it can realize different functions.

[0079] For example, when the enable signal NLIM_EN of the first state is received, the comparison threshold voltage Vcmp is the first threshold voltage Vt, and the driving circuit 12 can control the conduction or disconnection of the high-side switch M1 and the low-side switch M2 according to the enable signal NLIM_EN of the first state and the timing signal NI_NLIM of different states, thereby limiting the absolute value of the negative current to not exceed the negative current threshold It, preventing the absolute value of the negative current from being greater than the negative current threshold It and causing damage to the low-side switch M2, and making the output voltage Vout gradually return to the reference voltage Vref level, thereby improving the working stability of the voltage converter 10.

[0080] When the enable signal NLIM_EN of the second state is received, the comparison threshold voltage Vcmp is equal to the second threshold voltage Vg, so that zero current switching of the low-side switch M2 can be achieved, thereby reducing the switching loss of the voltage converter 10 and improving the energy conversion efficiency of the voltage converter 10.

[0081] See also Figure 4 , Figure 4 A signal timing diagram of a voltage converter 10 provided in an embodiment of the present application.

[0082] Wherein, the output voltage Vout is the output voltage of the voltage conversion device. Vref is the reference voltage, which is also the target level of the output voltage Vout. VLX is the output voltage of the output terminal LX of the voltage converter 10. IL is the current flowing through the output inductor L1. It is the negative current threshold, which is the lower limit value when the inductor current IL is a negative current. CMP_OUT is the comparison signal output by the comparison circuit 132. The enable signal NLIM_EN is the enable signal. The timing signal NI_NLIM is the timing signal. LG is the low-side drive signal. UG is the high-side drive signal.

[0083] In the present application, the first state is a high level state, such as VIN, and the second state is a low level state, such as GND.

[0084] Before time T3, the voltage converter 10 is in a normal operating mode. The high-side drive signal UG and the low-side drive signal LG alternate between high and low level states according to the state of the switching cycle signal TON. As a result, the high-side switch M1 and the low-side switch M2 are alternately turned on, and the inductor current IL is a positive current and fluctuates at the reference current Iref level. The output voltage VLX correspondingly alternates between a positive voltage and zero, and the output voltage Vout is substantially stable at the Vref level.

[0085] During the T3-T4 period, the voltage converter 10 switches from the heavy load mode to the light load mode, and the high-side drive signal UG and the low-side drive signal LG are both in a high level state. As a result, the high-side switch M1 is disconnected and the low-side switch M2 is turned on. The inductor current IL flows to the ground through the low-side switch M2, causing the inductor current IL to decrease in the positive direction. The output voltage VLX corresponds to zero. Due to the influence of the back electromotive force of the output inductor L1, the output voltage Vout increases and causes overshoot.

[0086] At time T4, the inductor current IL decreases to zero in the positive direction, and the operation instruction outside the voltage converter 10 indicates that the inductor current IL needs to be controlled to be a negative current. The operation trigger circuit correspondingly outputs the enable signal NLIM_EN of the first state, so that the enable signal NLIM_EN becomes a high level state.

[0087] During the T4-T5 period, the high-side drive signal UG and the low-side drive signal LG are still in the high level state. After the inductor current IL decreases to zero in the positive direction, it becomes a negative current, and the absolute value of the negative current gradually increases. The output voltage VLX is zero accordingly. The output voltage Vout decreases slightly but is still in the overshoot state.

[0088] At time T5, the inductor current IL reaches the negative current threshold It. At this time, the output voltage VLX is greater than or equal to the first threshold voltage Vt. The voltage threshold generation circuit 131 responds to the enable signal NLIM_EN in the high level state and outputs the first threshold voltage Vt to the comparison circuit 132. The comparison circuit 132 responds to the output voltage VLX being greater than or equal to the first threshold voltage Vt and outputs the comparison signal CMP_OUT in the high level state. The controller 133 responds to the comparison signal CMP_OUT in the high level state and outputs the timing signal NI_NLIM in the high level state. The drive circuit 12 responds to the enable signal NLIM_EN in the high level state and the timing signal NI_NLIM in the high level state, outputs the high-side drive signal UG in the high level state and the low-side drive signal LG in the low level state, thereby driving the high-side switch M1 and the low-side switch M2 to be disconnected.

[0089] During the T5-T6 period, since both the high-side switch M1 and the low-side switch M2 are turned off, the inductor current IL flows through the body diode of the high-side switch M1. The absolute value of the inductor current IL decreases. The output voltage Vout rises and then falls accordingly, and is still in an overshoot state.

[0090] At time T6, the preset current limiting time has passed since time T5, so the controller 133 switches the timing signal NI_NLIM to a low level state. Correspondingly, the drive circuit 12 responds to the enable signal NLIM_EN in a high level state, the comparison signal CMP_OUT in a low level state, and the timing signal NI_NLIM in a low level state, outputs a high-side drive signal UG in a high level state and a low-side drive signal LG in a high level state, thereby driving the high-side switch M1 to turn off and the low-side switch M2 to turn on. In this example, the preset current limiting time is the period from T5 to T6.

[0091] During the period T6-T7, the high-side drive signal UG and the low-side drive signal LG are both in a high level state. The changes of the inductor current IL, the output voltage VLX, and the output voltage Vout are the same as those during the period T4-T5, and will not be repeated here.

[0092] During the period T7-T8, the high-side drive signal UG remains at a high level, and the low-side drive signal LG alternates between high and low level states. As a result, the high-side switch M1 is continuously turned off, and the low-side switch M2 alternates between on and off, so that the inductor current IL is a negative current, and the inductor current IL changes continuously, and the output voltage VLX changes alternately between a positive voltage and zero, and the output voltage Vout gradually decreases.

[0093] At time T8, the output voltage Vout drops back to the target level of Vref. At this time, the voltage comparator in the control enable unit outputs the enable signal NLIM_EN of the second state. That is, the enable signal NLIM_EN becomes a low level state. The drive circuit 12 corresponds to outputting the low-side drive signal LG in the low level state, thereby driving the low-side switch M2 to be disconnected, and the inductor current IL flows through the body diode of the high-side switch M1. The absolute value of the inductor current IL decreases. The output voltage Vout rises accordingly.

[0094] During the T8-T9 period, after the inductor current IL is reduced to zero, it becomes a positive current and continues to increase. Thereafter, the voltage converter 10 is in a normal operating mode. The high-side drive signal UG and the low-side drive signal LG alternate between high and low level states according to the state of the switching cycle signal TON. The changes of the inductor current IL, the output voltage VLX, the output voltage Vout, the high-side drive signal UG, and the low-side drive signal LG are the same as before the T3 moment, and are not repeated here.

[0095] Thus, in the voltage converter 10 provided by the present application, when the inductor current IL reaches the negative current threshold It, the low-side switch M2 is disconnected, so that the absolute value of the inductor current IL decreases, reducing the risk of the low-side switch M2 being damaged by the negative current. After the preset current limiting time, the low-side switch M2 is turned on again, so that the overshoot output voltage Vout drops rapidly to return to the level of the reference voltage Vref as soon as possible.

[0096] See also Figure 5 , Figure 5 Another signal timing diagram of the voltage converter 10 provided in an embodiment of the present application.

[0097] Among them, the signal meanings of Vout, IL, VLX, CMP_OUT, NLIM_EN, UG, and LG are the same as Figure 4 The external operation instruction of the voltage converter 10 indicates that the zero current switching of the low-side switch M2 needs to be realized, and the operation trigger circuit outputs the enable signal NLIM_EN of the second state accordingly, so that the enable signal NLIM_EN continues to be in a low level state.

[0098] Before time T1, the high-side drive signal UG is in a high level state, and the low-side drive signal LG is in a low level state. Thus, both the high-side switch M1 and the low-side switch M2 are disconnected, and the inductor current IL is continuously zero.

[0099] At time T1, the high-side drive signal UG becomes a low-level state, and the low-side drive signal LG remains a low-level state. As a result, the high-side switch M1 is turned on, and the low-side switch M2 is turned off. Therefore, during the T1-T2 period, the output voltage VLX corresponds to the positive voltage VIN, and the inductor current IL is a positive current and continues to rise.

[0100] At time T2, the inductor current IL rises to a peak value, and then, during the period T2-T3, the high-side drive signal UG becomes a high level state, and the low-side drive signal LG becomes a high level state. As a result, the high-side switch M1 is turned off, and the low-side switch M2 is turned on. The inductor current IL is a positive current and continues to decrease. The output voltage VLX is a negative voltage and continues to increase.

[0101] At time T3, the inductor current IL drops to zero. In response to the enable signal NLIM_EN in the low level state, the zero current control switch S2 is turned on, and the comparison circuit 132 receives the second threshold voltage Vg. At this time, the second threshold voltage Vg is zero voltage. In response to the output voltage VLX being equal to the second threshold voltage Vg, the comparison circuit 132 outputs a comparison signal CMP_OUT in the high level state. The drive circuit 12 responds to the enable signal NLIM_EN in the low level state and the comparison signal CMP_OUT in the high level state, and outputs a low-side drive signal LG in the low level state, thereby driving the low-side switch M2 to disconnect.

[0102] Thus, in the voltage converter 10 provided by the present application, when the inductor current IL decreases to zero, the low-side switch M2 is disconnected, thereby achieving zero current switching of the low-side switch M2.

[0103] See also Figure 6 , Figure 6 A schematic diagram of the power conversion efficiency of the voltage converter 10 provided according to an embodiment of the present application.

[0104] Among them, curve L1 is the corresponding relationship curve between the power conversion efficiency and the load current of the voltage converter 10 provided by the present application. Curve L2 is the corresponding relationship curve between the power conversion efficiency and the load current of the existing voltage converter. It can be seen that in the existing voltage converter, due to the need to prevent the negative current from being too large to damage the low-side switch M2, the driving ability of the low-side switch M2 is relatively conservative, making the power conversion efficiency of the existing voltage converter low. The voltage converter 10 of the present application, on the premise of preventing the negative current from being too large to damage the low-side switch M2, can also improve the driving ability of the low-side switch M2, thereby improving the power conversion efficiency.

[0105] In some embodiments, the comparison circuit 132 may include a comparator. In other embodiments, see Figure 7 , Figure 7 Schematic diagram of a comparison circuit 132 provided in an embodiment of the present application. The comparison circuit 132 may also include a comparator 1321 and an offset compensation circuit 1322. The offset compensation circuit 1322 includes a compensation control circuit 1320 and a multiplexer MUX. The multiplexer MUX includes an output terminal, a control terminal, and a plurality of input switches. Here, an example is taken that the multiplexer MUX includes 8 input switches OFS1-OFS8, but the present application does not impose any limitation on the number of input switches included in the multiplexer MUX.

[0106] The first input terminal of the comparator 1321 receives the output voltage VLX, and the second input terminal of the comparator 1321 is electrically connected to the output terminal of the multiplexer MUX. In some embodiments, the first input terminal of the comparator 1321 is a non-inverting input terminal (positive input terminal), and the second input terminal of the comparator 1321 is an inverting input terminal (negative input terminal).

[0107] One end of each input switch of the multiplexer MUX is used to receive the comparison threshold voltage Vcmp. The control end of the multiplexer MUX is electrically connected to the compensation control circuit 1320. The compensation control circuit 1320 is also electrically connected to the output end of the comparator 1321. The output end of the comparator 1321 is used to output the comparison signal CMP_OUT.

[0108] In some embodiments, the comparator 1321 may be a multi-stage comparator, so that the comparison speed and the working efficiency of the comparator 1321 can be increased by setting the comparator 1321 as a multi-stage comparator.

[0109] There may be an offset difference between the first input terminal and the second input terminal of the comparator 1321. If the offset difference between the first input terminal and the second input terminal is large, it may affect the state of the comparison signal CMP_OUT, thereby reducing the accuracy and precision of the comparison circuit 132. Therefore, the offset compensation circuit 1322 can reduce the offset difference between the first input terminal and the second input terminal of the comparator 1321, thereby improving the accuracy and precision of the comparison circuit 132.

[0110] Specifically, when the comparison threshold voltage Vcmp is input to the second input terminal of the comparator 1321 through the input switch, the input switch can reduce the offset of the comparison threshold voltage Vcmp, thereby reducing the offset difference between the first input terminal and the second input terminal of the comparator 1321. Each different input switch corresponds to a different reduction in offset. Here, the input switches OFS1-OFS8 correspond to the offsets OFF1-OFF8, respectively, for example. Figure 8 As shown, the differences between the offsets OFF1-OFF8 are not equal.

[0111] The compensation control circuit 1320 is used to output different offset control signals to the control terminal of the multiplexer MUX in sequence according to the state of the comparison signal CMP_OUT. Correspondingly, the multiplexer MUX can turn on or off different input switches according to different offset control signals.

[0112] Specifically, the compensation control circuit 1320 can determine in sequence whether each input switch needs to be turned on or off according to the state of the comparison signal CMP_OUT. When the comparison threshold voltage Vcmp is less than the output voltage VLX, when the ideal offset difference between the first input terminal and the second input terminal of the comparator 1321 is 0, the comparison signal CMP_OUT should be in the second state. Therefore, when the comparison signal CMP_OUT is in the first state, the real-time offset difference between the first input terminal and the second input terminal is large, resulting in an error in the state of the comparison signal CMP_OUT. At this time, the compensation control circuit 1320 can respond to the comparison signal CMP_OUT in the first state, turn on the input switch OFS1, and turn off other input switches.

[0113] After the input switch OFS1 is turned on, the real-time offset of the comparison threshold voltage Vcmp changes to the difference between the original initial offset and the offset OFF1 corresponding to the input switch OFS1. At this time, the offset difference between the first input terminal and the second input terminal of the comparator 1321 also changes, and the comparison signal CMP_OUT may also change accordingly.

[0114] When the comparison signal CMP_OUT is still in the first state, it means that the real-time offset of the comparison threshold voltage Vcmp is still insufficient to make the comparison signal CMP_OUT in the correct state, that is, the second state. Therefore, the real-time offset of the comparison threshold voltage Vcmp is still large and needs to be further reduced. The compensation control circuit 1320 can continuously turn on the input switch OFS1, turn on the input switch OFS2, and turn off other input switches.

[0115] After the input switch OFS2 is turned on, the real-time offset of the comparison threshold voltage Vcmp is further reduced by the offset OFF2 corresponding to the input switch OFS2. When the comparison signal CMP_OUT is still in the first state, the real-time offset of the comparison threshold voltage Vcmp is still large and needs to be further reduced. The compensation control circuit 1320 can continuously turn on the input switch OFS2 and the input switch OFS3 on the basis of continuously turning on the input switch OFS1, while turning off other input switches.

[0116] When the comparison signal CMP_OUT changes to the second state, the real-time offset of the comparison threshold voltage Vcmp may be too small, which may increase the offset difference between the first input terminal and the second input terminal. Therefore, the compensation control circuit 1320 can disconnect the input switch OFS2 and turn on the input switch OFS3 on the basis of continuously turning on the input switch OFS1, while disconnecting other input switches.

[0117] By analogy, the compensation control circuit 1320 can turn on one of the input switches at a time. If the comparison signal CMP_OUT is still in the first state after the input switch is turned on, the input switch is kept turned on. If the comparison signal CMP_OUT changes to the second state, the input switch is turned off until the on or off state of all the input switches is determined.

[0118] In this way, the compensation control circuit 1320 can quickly improve the accuracy of the comparison signal CMP_OUT by gradually adjusting the voltage offset of the second input terminal of the comparator 1321. In addition, since the differences between the offsets OFF1 to OFF8 are unequal, the compensation control circuit 1320 can quickly and significantly improve the accuracy of the comparison signal CMP_OUT each time it adjusts the offset, with high efficiency.

[0119] See also Fig. 9 , Fig. 9A comparison error diagram of a comparison circuit 132 provided in an embodiment of the present application is provided. A Monte Carlo simulation experiment is performed on the comparison circuit 132, with a sample size of 500, and 500 corresponding comparison error results are obtained. As shown in the histogram, the 500 comparison error results satisfy a normal distribution, with an average value μ of 0.188 mV, a standard deviation σ of 0.145 mV, and 3σ of 0.435 mV. It can be seen that the comparison error of the comparison circuit 132 provided in the present application is small and the comparison accuracy is high.

[0120] In addition, the voltage converter 10 provided in an embodiment of the present application can also implement a dynamic voltage scaling (DVS) function.

[0121] Specifically, see Fig.10 , Fig.10 This is a schematic diagram of a voltage converter 10 according to an embodiment of the present application implementing a DVS function. The meanings of the signals Vref, Vout, IL, NLIM_EN, and NI_NLIM are the same as those in the previous text and will not be repeated here.

[0122] In the DVS function of the voltage converter 10 , the reference voltage Vref can be lowered according to actual needs. Since the output voltage Vout of the voltage conversion device follows the level of the reference voltage Vref, the output voltage Vout decreases as Vref decreases, thereby achieving the DVS function of the voltage converter 10 .

[0123] At this time, in response to the reference voltage Vref decreasing, the digital controller alternately outputs the enable signal NLIM_EN of the first state and the enable signal NLIM_EN of the second state. In this way, when the inductor current IL is a negative current, the output voltage Vout can be quickly reduced, thereby increasing the speed at which the output voltage Vout decreases to the level of Vref, and realizing the DVS function of the voltage converter 10.

[0124] In some other embodiments, the voltage converter 10 can also implement an overvoltage protection (OVP) function. Specifically, when the output voltage Vout exceeds the overvoltage threshold Vovp, the voltage comparator in the control enabling unit outputs an enable signal NLIM_EN in the first state. At this time, the voltage converter 10 operates in a negative current mode, and the inductor current IL is a negative current and its absolute value gradually increases, so that the output voltage Vout can be quickly reduced until it is less than the overvoltage threshold Vovp.

[0125] See also Fig.11 , Fig.11This is a flow chart of a control method of a voltage converter 10 provided in an embodiment of the present application. The control method can be applied to the voltage converter 10 and executed by the control circuit 100. Specifically, the control method of the voltage converter includes the following steps.

[0126] Step S91 , generating a first threshold voltage Vt according to the negative current threshold It.

[0127] Wherein, step S91 may be specifically performed by the voltage threshold generating circuit 131 .

[0128] Since the output current of the limiting current source ILIM is proportional to the negative current threshold It, the equivalent resistance of the tracking circuit 1311 is proportional to the equivalent resistance of the low-side switch M2, so the output voltage of the first threshold voltage generating circuit is the first threshold voltage Vt.

[0129] Step S92 , generating a comparison threshold voltage Vcmp according to the enable signal NLIM_EN.

[0130] Wherein, step S92 may be specifically executed by the voltage threshold generating circuit 131 .

[0131] When the enable signal NLIM_EN is in the first state, the negative current control switch S1 in the voltage threshold generation circuit 131 is turned on, the zero current control switch S2 is turned off, and the comparison threshold voltage Vcmp outputted by the voltage threshold generation circuit 131 is the first threshold voltage Vt.

[0132] When the enable signal NLIM_EN is in the second state, the negative current control switch S1 in the voltage threshold generation circuit 131 is turned off, the zero current control switch S2 is turned on, and the comparison threshold voltage Vcmp outputted by the voltage threshold generation circuit 131 is the second threshold voltage Vg.

[0133] In step S93 , the comparison threshold voltage Vcmp is compared with the output voltage VLX of the voltage converter 10 to generate a comparison signal CMP_OUT.

[0134] Wherein, step S93 may be specifically executed by the comparison circuit 132 .

[0135] When the output voltage VLX is greater than or equal to the comparison threshold voltage Vcmp, the comparison circuit 132 generates a comparison signal CMP_OUT in a first state. Otherwise, the comparison circuit 132 generates a comparison signal CMP_OUT in a second state.

[0136] Step S94 , generating a high-side driving signal UG and a low-side driving signal LG according to the comparison signal CMP_OUT and the enable signal NLIM_EN.

[0137] Wherein, step S94 may be specifically executed by the driving circuit 12 .

[0138] When the enable signal NLIM_EN is in the first state and the comparison signal CMP_OUT is in the first state, the controller 133 correspondingly outputs the timing signal NI_NLIM of the first state to the drive circuit 12. The drive circuit 12 responds to the enable signal NLIM_EN of the first state and the timing signal NI_NLIM of the first state, and outputs the low-side drive signal LG of the second state and the high-side drive signal UG of the first state to control the low-side switch M2 and the high-side switch M1 to be disconnected.

[0139] When the enable signal NLIM_EN is in the first state and the comparison signal CMP_OUT is in the second state, the controller 133 correspondingly outputs the timing signal NI_NLIM of the second state to the drive circuit 12. The drive circuit 12 responds to the enable signal NLIM_EN of the first state and the timing signal NI_NLIM of the second state, and outputs the low-side drive signal LG of the first state to control the low-side switch M2 to be turned on.

[0140] When the enable signal NLIM_EN is in the second state and the comparison signal CMP_OUT is in the first state, the drive circuit 12 outputs the low-side drive signal LG in the second state in response to the enable signal NLIM_EN in the second state and the comparison signal CMP_OUT in the first state to control the low-side switch M2 to be turned off.

[0141] In some embodiments, before step S91, the control method further includes: step S90 (not shown in the figure), performing offset compensation on the comparison circuit 132. Specifically, step S90 can be performed by the offset compensation circuit 1322. For specific description, please refer to the functional description of the offset compensation circuit 1322 above, which will not be repeated here.

[0142] In summary, the voltage converter 10, control method and voltage conversion device provided in the present application can time the high-side switch M1 and the low-side switch M2 to be turned on or off according to the negative current threshold It, thereby preventing the negative current from exceeding the negative current threshold It and causing damage to the power switch tube, and making the output voltage Vout of the voltage conversion device return to the level of the reference voltage Vref, thereby improving the working stability of the voltage converter 10.

[0143] In addition, since the voltage threshold generating circuit 131 in the voltage converter 10 includes a negative current control switch S1 and a zero current control switch S2, and the enable signal NLIM_EN in different states can control one of the negative current control switch S1 and the zero current control switch S2 to be turned on and the other to be turned off, therefore, the voltage converter 10 can switch between the negative current mode and the zero current detection mode by only changing the state of the enable signal NLIM_EN, thereby improving the working efficiency of the voltage converter 10 and increasing the application scenarios of the voltage converter 10.

[0144] Furthermore, since the limiting current source ILIM in the voltage converter 10 is proportional to the negative current threshold It, and the equivalent resistance of the tracking circuit 1311 is proportional to the equivalent resistance of the low-side switch M2, the first threshold voltage Vt outputted by the output terminal V of the first threshold voltage generating circuit is equal to the output voltage VLX of the voltage converter 10 when the negative current flowing through the low-side switch M2 reaches the negative current threshold It. Therefore, by comparing the output voltage VLX of the voltage converter 10 with the first threshold voltage Vt, it can be determined whether the negative current flowing through the low-side switch M2 reaches the negative current threshold It, thereby correspondingly controlling the low-side switch M2 to be turned on or off.

[0145] Furthermore, since the type of the tracking power tube M3, such as materials and components, is the same as that of the low-side switch M2, the resistance change characteristics of the tracking power tube M3 are the same as those of the low-side switch M2, thereby reducing the error caused by the first threshold voltage Vt and the drain-source voltage Vds of the low-side switch M2 being unequal when the equivalent resistance of the tracking power tube M3 does not follow the variation of the equivalent resistance of the low-side switch M2 due to the variation of the equivalent resistance of the low-side switch M2.

[0146] In addition, under the effect of the offset compensation mechanism, the accuracy and precision of the comparison circuit 132 can be improved, thereby improving the conversion efficiency of the voltage converter 10 .

[0147] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present application and are not intended to be limiting of the present application. As long as they are within the spirit and scope of the present application, appropriate changes and modifications to the above embodiments are within the scope of protection claimed in the present application.

Claims

1. A voltage converter, characterized in that: The voltage converter comprises a half-bridge circuit and a control circuit, the half-bridge circuit comprises a high-side switch and a low-side switch, and the control circuit comprises a voltage threshold generating circuit, a comparison circuit, a controller and a driving circuit; The voltage threshold generating circuit comprises a first voltage threshold generating circuit, the first voltage threshold generating circuit comprises a limiting current source and a tracking circuit, the limiting current source is connected in series with the tracking circuit, an equivalent resistance value of the tracking circuit is proportional to an equivalent resistance value of the low-side switch, an output current of the limiting current source is proportional to a preset negative current threshold, and an output end of the first voltage threshold generating circuit outputs a first threshold voltage as a comparison threshold voltage; The comparison circuit is used to receive the comparison threshold voltage and the output voltage of the voltage converter, and output a comparison signal according to a comparison result between the comparison threshold voltage and the output voltage; The controller is used to receive the comparison signal and output a timing signal according to the comparison signal; The driving circuit is used to control the high-side switch and the low-side switch to be turned on or off according to the enable signal, the comparison signal and the timing signal.

2. The voltage converter according to claim 1, wherein: The tracking circuit includes at least one tracking power tube, and the type of each tracking power tube is the same as that of the low-side switch.

3. The voltage converter according to claim 1, wherein: The comparison signal has a first state and a second state, and outputting the comparison signal according to the comparison result between the comparison threshold voltage and the output voltage includes: When the comparison threshold voltage is less than the output voltage, the comparison circuit outputs the comparison signal of the first state, otherwise, the comparison circuit outputs the comparison signal of the second state.

4. The voltage converter according to claim 3, wherein: The timing signal has a first state and a second state, and outputting the timing signal according to the comparison signal comprises: When receiving the comparison signal of the first state, the controller outputs the timing signal of the first state, and after a preset current limiting time, switches the timing signal to the second state.

5. The voltage converter according to claim 4, wherein: The enable signal has a first state, and the high-side switch and the low-side switch are controlled to be turned on or off according to the enable signal, the comparison signal and the timing signal, including: When receiving the enable signal of the first state, the comparison signal of the second state, and the timing signal of the second state, driving the low-side switch to turn on; When the enable signal of the first state and the timing signal of the first state are received, the high-side switch and the low-side switch are driven to be turned off.

6. The voltage converter according to claim 3, wherein: The enable signal also has a second state, the voltage threshold generating circuit further includes a negative current control switch and a zero current control switch, one end of the zero current control switch receives the second threshold voltage, the other end of the zero current control switch is electrically connected to the input end of the comparison circuit, and the two ends of the negative current control switch are electrically connected to the output end of the limiting current source and the input end of the comparison circuit respectively; In response to the enable signal of the first state, the negative current control switch is turned on, the zero current control switch is turned off, and the voltage threshold generation circuit outputs the first threshold voltage as the comparison threshold voltage; In response to the enable signal in the second state, the negative current control switch is turned off, the zero current control switch is turned on, and the voltage threshold generation circuit outputs the second threshold voltage as the comparison threshold voltage.

7. The voltage converter according to claim 6, wherein: The driving circuit is used to control the high-side switch and the low-side switch to be turned on or off according to the enable signal and the comparison signal in the second state; When the enable signal of the second state and the comparison signal of the first state are received, the low-side switch is driven to be turned off.

8. The voltage converter according to any one of claims 1 to 7, characterized in that: The comparison circuit includes a comparator and an offset compensation circuit, the offset compensation circuit includes a multiplexer and an offset control circuit, the first input terminal of the comparator receives the output voltage of the voltage converter, the second input terminal of the comparator is electrically connected to the output terminal of the multiplexer, the output terminal of the comparator is electrically connected to the offset compensation circuit, and the offset compensation circuit is also electrically connected to the control terminal of the multiplexer; The multiplexer includes at least one input switch, each input switch is used to receive the comparison threshold voltage and to reduce the offset of the comparison threshold voltage, and different input switches correspondingly reduce different offsets; The offset compensation circuit is used to control the on or off of the at least one input switch one by one according to the state of the comparison signal, so as to adjust the offset of the comparison threshold voltage.

9. A control method for a voltage converter, characterized in that: The control method is applied to the voltage converter according to any one of claims 1 to 8, and the control method comprises: generating the first threshold voltage according to a preset negative current threshold; When the enable signal is in a first state, the first threshold voltage is generated as the comparison threshold voltage, and when the enable signal is in a second state, a second threshold voltage is generated as the comparison threshold voltage, wherein the second threshold voltage is zero voltage; comparing the comparison threshold voltage and the output voltage to generate the comparison signal; According to the comparison signal and the enable signal, the high-side switch and the low-side switch are controlled to be turned on or off accordingly.

10. The control method according to claim 9, characterized in that: According to the comparison signal and the enable signal, correspondingly controlling the high-side switch and the low-side switch to be turned on or off includes: When the enable signal is in the first state and the comparison signal is in the first state, a timing signal of the first state is generated, and after a preset current limiting time, the timing signal of the second state is replaced; In response to the enable signal of the first state and the timing signal of the first state, controlling both the low-side switch and the high-side switch to be turned off; In response to the enable signal in the first state and the timing signal in the second state, controlling the low-side switch to be turned on; In response to the enable signal in the second state and the comparison signal in the first state, the low-side switch is controlled to be turned off.

11. The control method according to claim 10, characterized in that: The control method further comprises: According to the state of the comparison signal, the offset of the comparison threshold voltage is adjusted.

12. A voltage conversion device, characterized in that: An output inductor, an output capacitor and a voltage converter according to any one of claims 1 to 8, wherein one end of the output inductor is electrically connected to the output end of the voltage converter, the other end of the output inductor is electrically connected to one end of the output capacitor, and the other end of the output inductor is used to electrically connect to a load.

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