Switching converter with valley current detection

Abstract

The invention relates to a switching converter with valley current detection. A DC / DC converter including a low side and a high side is disclosed. The converter includes: a first switching device as part of a low side; a low-side current generator configured to generate a low-side current flowing in the first switching device; a second switching device; a compensation resistor coupled in series to the second switching device; a valley current reference current generator configured to generate a valley current threshold current # imgabs0 # flowing in the second switching device and in the compensation resistor to obtain a first voltage value; and a comparator configured to compare the first voltage value and a reference voltage to generate an error signal according to the comparison, the error signal controlling a conductivity of the first switching device on the low side.

Description

Technical Field

[0001] The present disclosure generally relates to a switching converter with valley current sensing, and a method for controlling a switching converter. Background Art

[0002] As is known, a DC-DC converter or switching converter can be obtained, which generates a DC output voltage from a DC input voltage to supply power to a load. The DC output voltage can be higher or lower than the DC input voltage. The output current of the DC-DC converter or switching converter varies with the load impedance and can also vary according to the switching phase. For example, during the switching phase, the output current can generally vary between a maximum peak current and a minimum valley current. The DC-DC converter or switching converter may include a circuit system for managing a maximum threshold value of the peak current. The DC-DC converter or switching converter may additionally or alternatively include a circuit system for managing a minimum threshold value of the valley current. Summary of the invention

[0003] One embodiment is a DC / DC converter including a low side and a high side. The converter includes: a first switching device as part of the low side; a low side current generator configured to generate a low side current flowing in the first switching device; a second switching device; a compensation resistor coupled in series to the second switching device; a valley current reference current generator configured to generate a valley current threshold current flowing in the second switching device and the compensation resistor to obtain a first voltage value; and a comparator configured to compare the first voltage value with a reference voltage to generate an error signal according to the comparison, the error signal controlling the conductivity of the first switching device on the low side.

[0004] Another embodiment is a converter circuit. The converter circuit includes: a high-side device coupled to a switch node and configured to selectively electrically couple the switch node to a high input voltage node according to a high-side control signal; a low-side device coupled to the switch node and configured to selectively electrically couple the switch node to a low input voltage node according to a low-side control signal; an inductor coupled between the switch node and an output node of the converter circuit; a first switch and a compensation resistor coupled in series with the first switch; and a comparator configured to compare a reference voltage with a voltage equal to the sum of the voltage at the switch node and the voltage drop across the first switch and the compensation resistor, the comparator being configured to generate a valley current threshold signal based in part on the output of the comparator, the valley current threshold signal indicating that the valley current provided to the inductor drops below a threshold current limit. The converter circuit also includes a controller configured to generate a high-side control signal and a low-side control signal based in part on the valley current threshold signal.

[0005] Another embodiment is a method of controlling a DC / DC converter. The method includes: generating a valley current threshold current flowing in a series connection including a first switching device and a compensation resistor; generating a first voltage value based on the valley current threshold current and the series resistance of the first switching device and the compensation resistor; using a comparator to compare the first voltage value and a reference voltage to generate an error signal based on the comparison; and controlling the conductivity of a low-side switching device of the DC / DC converter based in part on the error signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] For a more complete understanding of one or more embodiments of the present disclosure and its advantages, reference is now made to the following description in conjunction with the accompanying drawings, in which:

[0007] Figure 1 shows a schematic circuit diagram of a converter circuit according to some embodiments;

[0008] Figure 2 An example is shown according to some embodiments Figure 1 Schematic waveform diagram of the function of the converter circuit shown in;

[0009] Figure 3 shows a schematic circuit diagram of a valley current threshold detector circuit according to some embodiments;

[0010] Figure 4 An example is shown according to some embodiments Figure 3 Schematic waveform diagram of the function of the valley current threshold detector circuit shown in;

[0011] Figure 5 A schematic circuit diagram showing a valley current threshold detector circuit according to some embodiments; and

[0012] Figure 6 A schematic circuit diagram of a valley current threshold detector circuit according to some embodiments is shown.

[0013] Unless otherwise indicated, corresponding numbers and symbols in different figures generally refer to corresponding parts. The figures are drawn to illustrate relevant aspects of the embodiments and are not necessarily drawn to scale. The edges of features drawn in the figures do not necessarily indicate the end of the range of the features. DETAILED DESCRIPTION

[0014] Exemplary embodiments of the systems and methods of the present disclosure are described below. For the sake of clarity, all features of an actual implementation may not be described in this specification. It should of course be appreciated that in the development of any such actual implementation, many implementation-specific decisions may be made to achieve the developer's specific goals, such as complying with system-related and business-related constraints, which will vary depending on the implementation. In addition, it should be appreciated that such development work may be complex and time-consuming, but in any case remains a routine task for those of ordinary skill in the art who benefit from the present disclosure.

[0015] When depicting devices in the accompanying drawings herein, reference may be made to the spatial relationship between the various components and the spatial orientation of various aspects of the components. However, as will be appreciated by those skilled in the art after reading this disclosure in its entirety, the devices, components, apparatuses, etc. described herein may be positioned in any desired orientation. Therefore, terms such as "above," "below," "upper," "lower," or other similar terms used to describe the spatial relationship between the various components or to describe the spatial orientation of various aspects of such components should be understood to describe the relative relationship between the components or the spatial orientation of various aspects of such components, respectively, because the devices described herein may be oriented in any desired direction.

[0016] The making and use of various embodiments are discussed in detail below. However, it should be appreciated that the various embodiments described herein can be applied to a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the various embodiments, and should not be construed as limiting the scope. Unless otherwise indicated, the expressions "about," "approximately," and "substantially" mean within 10% of a given value, and preferably within 5% of a given value, or, such as in the case of substantially zero, less than 10% and preferably less than 5% of a comparable amount.

[0017] The embodiments discussed herein illustrate various aspects of a DC-DC converter or switching converter technology that provides accurate valley current detection and implementation of a valley current minimum threshold. As the output current of the switching converter continues to increase, it reaches a maximum reliable value. The maximum level is the peak current limit, and when the output current reaches the peak current limit threshold, the high-side transistor is turned off. As a result, the output current is reduced below the maximum reliable value.

[0018] In some embodiments, the on-time is constant and the off-time is controlled from cycle to cycle, and the valley current limit threshold can be detected. In order to detect the valley current limit threshold, the reference current can be forced to enter the low-side transistor replica structure with similar or identical characteristics to the low-side transistor of the switching converter. The target is to trigger the comparator when the output current as sensed by the replica structure becomes lower than the valley current limit threshold. Once triggered, the comparator generates a signal that allows the controller 110 of the DC-DC converter to turn on the high-side transistor. In some embodiments, the valley of the inductor current (or low-side transistor current) can also be used to control the current limit of the DC-DC converter. For example, if the output current does not drop below the valley current threshold, the high-side transistor is not conducting before the next clock cycle of the PWM signal. The valley current limit control can keep the on-time constant.

[0019] Figure 1 A schematic circuit diagram of a converter circuit 100 connected to a load 160 according to some embodiments is shown. The converter circuit 100 includes a controller 110, a high-side device 120, a low-side device 130, a compensator circuit 180, and a valley current threshold detector circuit 170. The converter circuit 100 is configured to receive a target reference voltage at a node VREF, a high reference voltage at a node VIN, and a low reference voltage at a node GND. In response to the received signal, the converter circuit 100 is configured to generate an output voltage for a load 160 at an output node VOUT. For example, the output voltage may be greater than the low reference voltage and less than the high reference voltage. The converter circuit 100 generates an output voltage by controlling a low-side control signal at a node LSG and a high-side control signal at a node HSG to minimize the difference between the feedback voltage at a node Vfb and a reference voltage.

[0020] The compensator circuit 180 receives a feedback voltage at a node Vfb and a target reference voltage at a node VREF. In response to a difference between the feedback voltage and the reference voltage, the compensator circuit 180 is configured to generate a PWM signal at a node PWM.

[0021] In order to generate the output voltage, the controller 110 turns on the high-side device 120 and the low-side device 130 alternately according to the PWM signal. In general, when the controller 110 turns on the high-side device 120, the controller 110 turns off the low-side device 130. Similarly, when the controller 110 turns on the low-side device 130, the controller 110 turns off the high-side device 120. In some embodiments, at least when the high-side device 120 is turned on, the rest of the converter circuit 100 can be modeled and / or considered as a high-side current generator that generates a high-side current flowing through the high-side device 120. Similarly, in some embodiments, at least when the low-side device 130 is turned on, the rest of the converter circuit 100 can be modeled and / or considered as a low-side current generator 135 that generates a low-side current flowing through the low-side device 130.

[0022] In some embodiments, in response to the difference between the feedback voltage and the reference voltage, the compensator circuit 180 is configured to adjust the PWM signal so that the feedback voltage changes to reduce the difference. For example, the compensator circuit 180 can be configured to increase the high time of the PWM signal in response to the feedback voltage being less than the reference voltage. Similarly, the compensator circuit 180 can be configured to reduce the high time of the PWM signal in response to the feedback voltage being greater than the reference voltage.

[0023] In response to the adjusted PWM signal, the controller 110 modifies or controls the ratio of the on-time duration of the high-side device 120 to the on-time duration of the low-side device 130. For example, in response to the adjusted PWM signal, the controller can be configured to increase the ratio, for example, so that during a specific cycle, the high-side device is connected to an increased on-time duration, and in some embodiments, the low-side device is connected to a reduced on-time duration. Similarly, in response to the adjusted PWM signal, the controller 110 can be configured to reduce the ratio, for example, so that during a specific cycle, the high-side device is connected to a reduced on-time duration, and in some embodiments, the low-side device is connected to an increased on-time duration. Thus, the controller 110 modifies or controls the ratio of the on-time duration so that when the converter circuit 100 supplies a load current to the load through a filter including an inductor 140 and a load capacitor 150, the reference voltage is equal to or substantially equal to the reference voltage.

[0024] The converter circuit 100 also includes a valley current threshold detector circuit 170 configured to generate a valley current threshold signal at a node VALCL, wherein the valley current threshold signal indicates whether the valley current provided to the inductor 140 drops below a threshold limit. The valley current threshold signal is then received at the controller 180 via the node VALCL.

[0025] As discussed in further detail below, the valley current threshold detector circuit 170 is designed and manufactured to generate a valley current threshold signal in response to the voltage at the switch node SW increasing to a level sufficient to indicate that the current through the low-side device 130 is less than the valley current minimum threshold current limit. Additionally, as discussed in further detail below, the valley current threshold detector circuit 170 is designed and manufactured to replicate the voltage drop across the low-side device 130 using a replica device having a nominal resistance designed and manufactured to match the nominal resistance of the low-side device 130 when the low-side device 130 is conducting a current equal to the valley current minimum threshold current limit.

[0026] In some embodiments, the resistance of the replica device and the resistance of the low-side device 130 differ by less than any of about 0.05%, about 0.1%, about 0.2%, about 0.3%, about 0.4%, about 0.5%, about 1%, about 2%, about 3%, about 4%, about 5%, about 10%, about 15%, about 20%, and about 25%. For example, the resistance of the replica device and the resistance of the low-side device 130 can differ by between 0% and about 0.5%, or any other limit listed above. In some embodiments, when the converter is operated at any ambient temperature between 40°C and 150°C, the resistance of the replica device and the resistance of the low-side device 130 differ by less than any one of about 0.05%, about 0.1%, about 0.2%, about 0.3%, about 0.4%, about 0.5%, about 1%, about 2%, about 3%, about 4%, about 5%, about 10%, about 15%, about 20%, and about 25%.

[0027] In some embodiments, the voltage drop across the replica device and the voltage drop across the low-side device 130 differ by less than any of about 0.05%, about 0.1%, about 0.2%, about 0.3%, about 0.4%, about 0.5%, about 1%, about 2%, about 3%, about 4%, about 5%, about 10%, about 15%, about 20%, and about 25%. For example, the voltage drop across the replica device and the voltage drop across the low-side device 130 may differ by between 0% and about 0.5%, or any other limit listed above. In some embodiments, when the converter is operated at any ambient temperature between 40°C and 150°C, the voltage drop across the replica device and the voltage drop across the low-side device 130 differ by less than any one of 0.05%, about 0.1%, about 0.2%, about 0.3%, about 0.4%, about 0.5%, about 1%, about 2%, about 3%, about 4%, about 5%, about 10%, about 15%, about 20%, and about 25%.

[0028] The controller 110 receives the valley current threshold signal and controls the on / off cycles of the high-side device 120 and the low-side device 130 according to control principles discussed in embodiments elsewhere herein, for example. Thus, in some embodiments, the conductivity of the high-side device 120 and the low-side device 130 is controlled such that the current to the inductor 140 has a minimum value (valley value) that is less than the maximum threshold limit.

[0029] In some embodiments, a valley current limit is used to prevent the average output current from exceeding a maximum threshold current. By controlling the valley current, the converter can avoid exceeding the peak current limit during the on-time when the high-side switch is turned on. The use of peak current limit and valley current limit control provides redundancy and makes the system more robust.

[0030] Figure 2 An example is shown according to some embodiments Figure 1 Schematic waveform diagram 200 of the functionality of converter circuit 100 is shown in FIG. The schematic waveforms shown illustrate specific embodiments, and other waveforms may be used to implement the inventive aspects discussed herein.

[0031] At the intersection point 205, the inductor current Icoil decreases below the valley current threshold 235, as indicated by the switch node voltage increasing above the valley current threshold limit 220. In response, the valley current threshold detector circuit 170 generates a corresponding valley current threshold signal at the node VALCL. The valley current threshold signal provides an indication that the valley current of the converter circuit 100 has dropped below the target threshold limit.

[0032] In response to the rising edge 210 of the PWM signal at the node PWM, because the valley current threshold signal indicates that the valley current of the converter circuit 100 has dropped below the target threshold limit, the controller 110 causes the low-side control signal at the node LSG to turn off the low-side device 130. In response to the low-side device 130 being turned off, the low-side current I_LS decreases.

[0033] In the illustrated embodiment, in response to the rising edge 210 of the PWM signal at the node PWM, the controller 110 causes the side control signal at the node HSG to turn on the high-side device 120 after a delay, for example, to ensure that the high-side device 120 and the low-side device 130 are not turned on at the same time. In response to turning on, the valley current threshold signal is pulled to ground, the high-side current I_HS increases, the inductor current Icoil increases, and the switch node voltage at the switch node SW increases to or near the high reference voltage at the node VIN.

[0034] In the illustrated embodiment, after the high-side device 120 has been turned on, the controller 110 causes the side control signal at the node HSG to turn off the high-side device 120 after a delay, for example, so that the high-side device 120 is turned on for an on-time duration corresponding to a target ratio of the high-side device 120 on-time to the low-side device 130 on-time in the cycle. In some embodiments, the on-time duration is constant between cycles of the PWM signal. In response to the side device 120 being turned off, the high-side current I_HS decreases.

[0035] In the illustrated embodiment, after the high-side device 120 has been turned off, the controller 110 causes the side control signal at the node LSG to turn on the low-side device 130 after a delay, for example, to ensure that the high-side device 120 and the low-side device 130 are not turned on at the same time. In response to the side device 130 being turned on, the low-side current I_LS increases, the switch node voltage at the switch node SW decreases to below the output voltage at the output node VOUT to or close to the low reference voltage at the node GND, and the inductor current Icoil begins to decrease.

[0036] As the inductor current Icoil decreases, the low side current I_LS correspondingly decreases and the switch node voltage correspondingly increases, and at 230 , as the inductor current Icoil decreases below the valley current threshold 235 , the switch node voltage becomes greater than the valley current threshold limit 220 .

[0037] In response to the rising edge 225 of the PWM signal at the node PWM, the controller 110 does not cause the low side control signal at the node LSG to shut down the low side device 130 because the valley current threshold signal indicates that the valley current of the converter circuit 100 has not dropped below the target threshold limit.

[0038] In response to the inductor current Icoil decreasing to below the valley current threshold 235 and the switch node voltage increasing to above the valley current threshold limit 220, the valley current threshold detector circuit 170 generates a corresponding valley current threshold signal at the node VALCL. In this case, the valley current threshold signal provides an indication that the valley current of the converter circuit 100 has dropped below the target threshold limit, and in response to the valley current threshold signal, because the PWM signal is already high, the controller 110 causes the low-side control signal at the node LSG to turn off the low-side device 130. In response to the low-side device 130 being turned off, the low-side current I_LS decreases.

[0039] In the illustrated embodiment, in response to the valley current threshold signal, the controller 110 causes the side control signal at the node HSG to turn on the high-side device 120 after a delay, for example, to ensure that the high-side device 120 and the low-side device 130 are not turned on at the same time. In response to turning on, the valley current threshold signal is clamped to the node GND, the high-side current I_HS increases, the inductor current Icoil increases, and the switch node voltage at the switch node SW increases.

[0040] In the illustrated embodiment, after the high-side device 120 has been turned on, the controller 110 causes the side control signal at the node HSG to turn off the high-side device 120 after a delay, for example, so that the high-side device 120 is turned on for a duration of time corresponding to a target ratio of the high-side device 120 on time and the low-side device 130 on time within the cycle. In response to the side device 120 being turned off, the high-side current I_HS decreases.

[0041] In the illustrated embodiment, after the high-side device 120 has been turned off, the controller 110 causes the side control signal at the node LSG to turn on the low-side device 130 after a delay, for example, to ensure that the high-side device 120 and the low-side device 130 are not turned on at the same time. In response to the side device 130 being turned on, the low-side current I_LS increases, the switch node voltage at the switch node SW decreases to be lower than the output voltage at the output node VOUT, and the inductor current Icoil begins to decrease.

[0042] Thus, in the illustrated embodiment, at each cycle of the PWM signal, the inductor current Icoil decreases to less than the valley current threshold 235, as indicated by the switch node voltage increasing above the valley current threshold limit 220. If the PWM signal is high when the valley current threshold indicates that the inductor current has decreased to less than the valley current threshold, the controller 110 responds to the valley current threshold signal such that the low-side control signal at the node LSG turns off the low-side device 130. If the PWM signal is low when the valley current threshold indicates that the inductor current has decreased to less than the valley current threshold, the controller 110 responds to the PWM signal going high such that the low-side control signal at the node LSG turns off the low-side device 130.

[0043] Figure 3 A schematic circuit diagram of a valley current threshold detector circuit 300 according to some embodiments is shown. The valley current threshold detector circuit 300 may be used as the valley current threshold detector circuit 170 of a converter, such as the converter circuit 100. The valley current threshold detector circuit 300 includes a replica device 310 including a replica switch 312 and a compensation resistor 314, a valley current reference current generator 320, and a comparator 330.

[0044] The following node equations describe the electrical function of the valley current threshold detector circuit 300 as used in the converter circuit 100:

[0045]

[0046] and

[0047]

[0048] where v SW is the voltage at the switch node SW, ILS is the current in the low-side device 130, α is the percentage of the current of the low-side device 130 flowing through the channel of the low-side device 130, R′ ds,LS is the drain-source resistance of the low-side device 130, w LS is the channel width of the low-side device 130, v1 is the voltage at the node V1, is the reference current of the valley current reference current generator 320, β is the percentage of the current flowing through the replica device 310 that flows through the channel of the replica switch 312, and R′ ds,replica is the drain-source resistance of the replica switch 312, w replica is the channel width of the replica switch 312 , and R1 is the resistance of the compensation resistor 314 .

[0049] Under the comparator threshold condition, ILS is equal to the valley current threshold ILS_VCL and v1 = 0, and:

[0050]

[0051] therefore,

[0052] The valley current threshold detector circuit 300 is designed and fabricated such that

[0053]

[0054] thus,

[0055] and

[0056]

[0057] For example, the replica device 310 may be designed and manufactured to have a nominal impedance or resistance that matches the nominal impedance or resistance of the low-side device of the converter, such that the impedance or resistance of the replica device 310 is at least a first factor value times the impedance or resistance of the low-side device of the converter having the valley current threshold detector circuit 300 at room temperature (T=27° C.). For example, when the valley current threshold detector circuit 300 is used in an embodiment of the converter circuit 100, the replica device 310 may be designed and manufactured to have an impedance or resistance equal to, for example, a factor value of 5000 times the impedance of the low-side device 130 at least at room temperature (T=27° C.), for example because the width of the replica device 310 is 1 / 5000 of the width of the low-side device 130. Other fractional relationships may be used.

[0058] As will be appreciated by those skilled in the art, conventional valley current detector circuits lack resistors corresponding to compensation resistors 314. Therefore, in some cases, such as, for example, at high temperatures, the impedance or resistance of conventional valley current detector circuits will not match the impedance or resistance of low-side devices. Therefore, when the low-side current is equal to the target valley current limit, voltage v1 will not be equal to 0 (i.e., threshold condition). This occurs at least in part because the scaling ratio of the body diode area and channel on resistance (channel on resistance) of the replica device and the low-side device is different. Therefore, the ratio of the current conducted by the body drain diode of the replica device to the current conducted by the body drain diode of the low-side device is different from the ratio of the effective width of the replica device to the low-side device.

[0059] In some embodiments, the resistance of the compensation resistor 314 increases monotonically with increasing temperature of the compensation resistor 314. In some embodiments, the resistance value of the replica resistor is between at least one of 30Ω and 100Ω, 50Ω and 90Ω, and 60Ω and 80Ω for a temperature T<80°C, and between at least one of 60Ω and 200Ω, 60Ω and 150Ω, and 70Ω and 140Ω for a temperature T>80°C.

[0060] In some embodiments, the series resistance of replica switch 312 and compensation resistor 314 matches the resistance of low-side device because compensation resistor 314 has a voltage drop that affects the resistance of replica switch 312. For example, the voltage drop of compensation resistor 314 reduces the drain-source voltage of replica switch 312. Therefore, the forward bias voltage of the body diode of replica switch 312 is reduced and the effective resistance of the body diode is increased. Therefore, replica switch 312 is either not turned on or turned on with a smaller absorption current. In some embodiments, the voltage drop across compensation resistor 314 is between about 30mV and about 70mV.

[0061] In some embodiments, the resistance of the compensation resistor 314 and at least one of the resistance of the low-side device and the resistance of the compensation resistor 314 are temperature dependent, having substantially the same temperature coefficient.

[0062] The valley current reference current generator 320 can be designed and manufactured to provide a current having a second factor value of the valley current minimum threshold current limit when the low-side device conducts a current equal to the valley current minimum threshold current limit at least at room temperature (T=27° C.). Thus, when the valley current threshold detector circuit 300 is used in an embodiment of the converter circuit 100, the valley current reference current generator 320 can be designed and manufactured to provide a current having a factor value equal to 1 / 5000 of the valley current minimum threshold current limit at least when the low-side device conducts a current equal to the valley current minimum threshold current limit. The valley current reference current generator circuit 320 can be designed and manufactured to provide a current having a factor value equal to a fraction of the valley current minimum threshold current limit determined based on the width ratio between the low-side device and the replica switch 310.

[0063] Because, at least when the low-side device conducts a current equal to the valley current minimum threshold current limit, the first factor value and the second factor value have an inverse relationship, the voltage drop across the replica device 310 can be approximately equal to or substantially equal to or effectively equal to the voltage drop across the low-side device when the low-side device conducts a current having a value equal to the valley current minimum threshold current limit.

[0064] In some embodiments, the first factor value and the second factor value differ by less than any one of about 0.5%, about 1%, about 2%, about 3%, about 4%, about 5%, about 10%, about 15%, about 20%, and about 25%. For example, the first factor value and the second factor value differ by between 0% and about 0.5%, or any other limit listed above. In some embodiments, when the converter is operated at any ambient temperature between -40°C and 150°C, the first factor value and the second factor value differ by less than any one of about 0.5%, about 1%, about 2%, about 3%, about 4%, about 5%, about 10%, about 15%, about 20%, and about 25%.

[0065] Thus, when the valley current threshold detector circuit 300 is used in an embodiment of the converter circuit 100, when the switch node voltage increases to become greater than a switch node valley current threshold limit (such as the valley current threshold limit 220), the voltage at the positive input of the comparator 330 increases to be greater than the voltage at the negative input of the comparator 330. Thus, the comparator 330 generates a valley current threshold signal at the node VALCL, wherein the valley current threshold signal indicates that the voltage of the switch node has increased to become greater than the switch node valley current threshold limit, which can be conditionally used as an indication that the valley current of the converter has dropped below the valley current minimum threshold current limit.

[0066] In some embodiments, the compensation resistor 314 can be, for example, a designed resistance element, such as a physical resistor, rather than, for example, a parasitic resistance inherent in the designed components or wiring. In some embodiments, the compensation resistor 314 includes a resistive material, such as polysilicon, doped silicon, doped semiconductor, or other materials used to form a resistor. In some embodiments, the compensation resistor 314 includes a switch or a transistor, such as a MOS transistor.

[0067] When the low-side control signal at node LSG is low, switch 340 is used to disconnect the input of the comparator from the replica device 310. When the high-side control signal at node HSG is high, switch 350 is used to clamp the valley current threshold signal at node VALCL to ground.

[0068] Figure 4 An example is shown according to some embodiments Figure 3 Schematic waveform diagram 400 of the functionality of valley current threshold detector circuit 300 is shown in FIG. The schematic waveforms shown illustrate specific embodiments, and other waveforms may be used to implement the inventive aspects discussed herein.

[0069] At the intersection point 410, the switch node voltage at the node SW increases above the valley current threshold limit 420, and the voltage at the node V1 increases above the reference voltage at the node Vref. In response, the comparator 330 generates a corresponding valley current threshold signal at the node VALCL. The valley current threshold signal provides an indication that the valley current of the converter circuit has dropped below the target threshold limit.

[0070] In response to the PWM signal of the converter being high and the valley current threshold signal being high, the controller of the converter circuit causes the low-side control signal at node LSG to turn off the low-side device of the converter circuit and causes the side control signal at node HSG to turn on the high-side device of the converter after a delay, for example, to ensure that the high-side device and the low-side device are not turned on at the same time. In response to turning on, the valley current threshold signal is pulled to ground, and the switch node voltage at the switch node SW increases, and the voltage at the node V1 increases.

[0071] After the high-side device has been turned on, the controller causes the side control signal at the node HSG to turn off the high-side device after a delay, for example, so that the high-side device is turned on for a duration of on time corresponding to a target ratio of the high-side device on time and the low-side device on time in the cycle. After the high-side device has been turned off, at 450, the controller causes the side control signal at the node LSG to turn on the low-side device after a delay, for example, to ensure that the high-side device and the low-side device are not turned on at the same time. In response to the side device being turned on, the switch node voltage at the switch node SW is reduced to a voltage lower than the output voltage at the output node VOUT, and the voltage at the node V1 is reduced to a voltage lower than the reference voltage.

[0072] In response to a rising edge of a PWM signal of a converter using a valley current threshold detector circuit, at 410, a controller of the converter causes a low-side control signal at node LSG to turn off a low-side device of the converter and turn off the replica switch 312 of the valley current threshold detector circuit 300. In response to the low-side device turning off, the low-side current of the converter decreases.

[0073] Thus, in the illustrated embodiment, the valley current threshold detector circuit 300 functions as described above with reference to Figure 1 and Figure 2 The valley current threshold detector circuit 170 described is similar or identical.

[0074] Figure 5 1 shows a schematic circuit diagram of a valley current threshold detector circuit 500 according to some embodiments. The valley current threshold detector circuit 500 can be used as the valley current threshold detector circuit 170 of a converter (such as the converter circuit 100). The valley current threshold detector circuit 500 includes a replica device 510 including a replica switch 512 and a compensation resistor switch 514, a valley current reference current generator 520, and a comparator 530. The compensation resistor switch 514 is previously discussed. Figure 3 A specific embodiment of the compensation resistor 314.

[0075] The valley current threshold detector circuit 500 may be similar or identical and / or perform similar or identically to the valley current threshold detector circuit described above with reference to the valley current threshold detector circuit 300 , where corresponding elements have similar or identical characteristics and functions.

[0076] Compared with the corresponding elements of some embodiments of the valley current threshold detector circuit 300, the replica switch 512 and the compensation resistor switch 514 can have the same structure, but they can have different sizes. For example, the replica switch 512 and the compensation resistor switch 514 can be similarly formed semiconductor MOSFET switches. Thus, the replica switch can have a first channel and a first diode with a first activation voltage, and the compensation resistor switch 514 can have a second channel and a second diode with a second activation voltage. In addition, when used for a converter circuit, the replica switch 512 and the compensation resistor switch 514 can have the same structure as the low-side device of the converter. Thus, in some converters, the low-side device, the replica switch 512 and the compensation resistor switch 514 can be similarly formed as a semiconductor MOSFET switch.

[0077] When the low-side device, the replica switch 512, and the compensating resistor switch 514 have similar or identical structures, the resistance or impedance of the combination of the replica switch 512 and the compensating resistor switch 514 better matches the resistance or impedance of the low-side device under various processes, temperatures, voltages, currents, and other operating conditions than when non-identical structures are used. Similarly, when the low-side device, the replica switch 512, and the compensating resistor switch 514 have similar or identical structures, the voltage drop across the combination of the replica switch 512 and the compensating resistor switch 514 better matches the voltage drop across the low-side device under various processes, temperatures, voltages, currents, and other operating conditions than when non-identical structures are used.

[0078] In some embodiments, the resistance of the compensation resistor switch 514 increases monotonically as the temperature of the compensation resistor switch 514 increases. In some embodiments, the resistance value of the compensation resistor switch 514 is between at least one of 30Ω and 100Ω, 50Ω and 90Ω, and 60Ω and 80Ω for a temperature T<80°C, and between at least one of 60Ω and 200Ω, 60Ω and 150Ω, and 70Ω and 140Ω for a temperature T>80°C.

[0079] In some embodiments, the resistance of the compensation resistor switch 514 and the resistance of the low-side device are temperature dependent, having substantially the same slope of resistance divided by temperature for temperatures less than 80° C. In some embodiments, the resistance of the compensation resistor switch 514 and the resistance of the compensation resistor 314 are temperature dependent, having substantially the same temperature coefficient.

[0080] Figure 6A schematic circuit diagram of a valley current threshold detector circuit 600 according to some embodiments is shown. The valley current threshold detector circuit 600 may be used as the valley current threshold detector circuit 170 of a converter, such as the converter circuit 100. The valley current threshold detector circuit 600 includes a replica device 610, a valley current reference current generator 620, and a comparator 630. The valley current threshold detector circuit 600 may behave similarly or identically to the valley current threshold detector circuits described above with reference to the valley current threshold detector circuit 300 and / or the valley current threshold detector circuit 500, wherein corresponding elements function correspondingly.

[0081] Compared to the corresponding valley current reference current generators 320 and 520 of some embodiments of the valley current threshold detector circuits 300 and / or 500, the valley current reference current generator 620 can be designed and manufactured to generate a current that varies with one or more operating conditions (such as process, temperature, voltage, current, and other operating conditions). For example, the valley current reference current generator 620 can be designed and manufactured to generate a current that varies with one or more operating conditions, i.e., the valley current threshold current, in order to compensate or partially compensate for the mismatch between the resistance or impedance of the replica device 610 and the low-side device of the converter, and / or compensate for the above reference current. Figure 3 Describes the mismatch between alpha and beta factors.

[0082] In embodiments where the valley current reference current generator 620 compensates or partially compensates for the mismatch between the resistance or impedance of the replica device 610 and the low-side device of the converter, the voltage drop across the replica device 610 better matches the voltage drop across the low-side device under various process, temperature, voltage, current, and other operating conditions than when an uncompensated current source is used.

[0083] In some embodiments, the valley current reference current generator 320 or 520 may have the compensation properties discussed with reference to the valley current reference current generator 620 .

[0084] Examples of the invention are summarized herein. Other examples may also be understood from the overall description and claims submitted herein.

[0085] Example 1. One embodiment is a DC / DC converter including a low side and a high side. The converter includes: a first switching device as part of the low side; a low side current generator configured to generate a low side current flowing in the first switching device; a second switching device; a compensation resistor coupled in series to the second switching device; a valley current reference current generator configured to generate a valley current threshold current flowing in the second switching device and the compensation resistor to obtain a first voltage value; and a comparator configured to compare the first voltage value with a reference voltage to generate an error signal according to the comparison, the error signal controlling the conductivity of the first switching device on the low side.

[0086] Example 2. A DC / DC converter as described in Example 1, wherein the first switching device includes a first channel, wherein the second switching device includes a second channel, and wherein the compensation resistor is designed to have a value based on the respective designed resistance values ​​of the first switching device and the second switching device, a portion of a designed current flowing in the first channel, or a portion of a designed valley current threshold current flowing in the second channel.

[0087] Example 3. The DC / DC converter of Example 1 or 2, wherein the first switching device comprises a first channel, wherein the second switching device comprises a second channel, and wherein the resistance value R1 of the compensation resistor is defined by the following formula: Where α is the percentage of the current flowing through the first switching device that flows through the first channel, where R′ ds,LS is the drain-source resistance of the first switching device, where w sdY is the width of the second switching device, where β is the percentage of the current flowing through the second switching device that flows through the second channel, and where R′ ds,sd2 is the drain-source resistance of the second switching device.

[0088] Example 4. The DC / DC converter of any of Examples 1-3, wherein the resistance value of the compensation resistor increases monotonically with an increase in the temperature of the compensation resistor.

[0089] Example 5. The DC / DC converter of any one of Examples 1-4, wherein the resistance value of the compensation resistor is between at least one of 30Ω and 100Ω, 50Ω and 90Ω, and 60Ω and 80Ω for T<80°C, and between at least one of 60Ω and 200Ω, 60Ω and 150Ω, and 70Ω and 140Ω for T>80°C.

[0090] Example 6. The DC / DC converter of any of Examples 1-5, wherein the resistance value of the compensation resistor and the resistance value of at least one of the first switching device and the second switching device are temperature dependent, having substantially the same resistance divided by temperature slope for T<80°C.

[0091] Example 7. The DC / DC converter of any of Examples 1-6, wherein a series resistance of the second switching device and the compensation resistor differs from an inverse of a resistance of the first switching device by less than 5%.

[0092] Example 8. The DC / DC converter of Example 7, wherein the first switching device includes a first transistor having a first gate configured to receive a first gate voltage, wherein the second switching device includes a second transistor having a second gate configured to receive a second gate voltage, and wherein the first gate voltage is equal to the second gate voltage.

[0093] Example 9. The DC / DC converter of any of Examples 1-8, wherein when the DC / DC converter operates at a temperature of 80°C, a series resistance of the second switching device and the compensation resistor differs by less than 5% from a resistance of the first switching device.

[0094] Example 10. The DC / DC converter of any of Examples 1-9, wherein the compensation resistor comprises a third switching device.

[0095] Example 11. The DC / DC converter of Example 10, wherein the first switching device includes a first transistor having a first gate configured to receive a first gate voltage, wherein the second switching device includes a second transistor having a second gate configured to receive a second gate voltage, wherein the third switching device includes a third transistor having a third gate configured to receive a third gate voltage, and wherein the first gate voltage, the second gate voltage, and the third gate voltage are equal.

[0096] Example 12. Another embodiment is a converter circuit. The converter circuit includes: a high-side device coupled to a switch node and configured to selectively electrically couple the switch node to a high input voltage node according to a high-side control signal; a low-side device coupled to the switch node and configured to selectively electrically couple the switch node to a low input voltage node according to a low-side control signal; an inductor coupled between the switch node and an output node of the converter circuit; a first switch and a compensation resistor coupled in series with the first switch; and a comparator configured to compare a reference voltage with a voltage equal to the sum of the voltage at the switch node and the voltage drop across the first switch and the compensation resistor, the comparator being configured to generate a valley current threshold signal based in part on the output of the comparator, the valley current threshold signal indicating that the valley current provided to the inductor drops below a threshold current limit. The converter circuit also includes a controller configured to generate a high-side control signal and a low-side control signal based in part on the valley current threshold signal.

[0097] Example 13. The converter circuit of Example 12, wherein a resistance of the first switch and the compensation resistor differs from an inverse of a resistance of the low-side device by less than 5%.

[0098] Example 14. The converter circuit of any of Examples 12-13, wherein the first switch includes a first transistor having a first gate configured to receive a first gate voltage, wherein the low-side device includes a second transistor having a second gate configured to receive a second gate voltage, and wherein the first gate voltage is equal to the second gate voltage.

[0099] Example 15. The converter circuit of any of Examples 12-14, wherein the compensation resistor comprises a second switch.

[0100] Example 16. The converter circuit of Example 15, wherein the first switch includes a first gate configured to receive a first gate voltage equal to a gate voltage of the low-side device, and wherein the second switch includes a second gate configured to receive a second gate voltage equal to the gate voltage of the low-side device.

[0101] Example 17. The converter circuit of any of Examples 12-16, wherein the first switch and the compensation resistor have a first voltage drop, wherein the low-side device has a second voltage drop, and wherein the first voltage drop is within 5% of the second voltage drop.

[0102] Example 18. Another embodiment is a method of controlling a DC / DC converter. The method includes: generating a valley current threshold current flowing in a series connection including a first switching device and a compensation resistor; generating a first voltage value based on the valley current threshold current and the series resistance of the first switching device and the compensation resistor; comparing the first voltage value and a reference voltage using a comparator to generate an error signal based on the comparison; and controlling the conductivity of a low-side switching device of the DC / DC converter based in part on the error signal.

[0103] Example 19. The method of Example 18, wherein the first switching device includes a first transistor having a first gate configured to receive a first gate voltage, wherein the low-side switching device includes a second transistor having a second gate configured to receive a second gate voltage, and wherein the first gate voltage is equal to the second gate voltage.

[0104] Example 20. The method of Example 19, wherein the compensation resistor includes a third transistor having a third gate configured to receive a third gate voltage, and wherein the third gate voltage is equal to the first gate voltage and the second gate voltage.

[0105] Although the present invention has been described with reference to exemplary embodiments, this description is not intended to be interpreted as limiting. For those skilled in the art, various modifications and combinations of the exemplary embodiments and other embodiments of the present invention will be clear after reference to the specification. Therefore, the appended claims are intended to cover any such modifications or embodiments.

Claims

1. A DC / DC converter comprising a low side and a high side, the converter comprising: a first switching device as part of the low side; a low-side current generator configured to generate a low-side current flowing in the first switching device; Second switchgear; a compensation resistor coupled in series to the second switching device; A valley current reference current generator configured to generate a valley current threshold current flowing in the second switching device and in the compensation resistor To obtain a first voltage value; as well as A comparator is configured to compare the first voltage value with a reference voltage to generate an error signal according to the comparison, the error signal controlling the conductivity of the first switching device on the low side.

2. The DC / DC converter of claim 1 , wherein the first switching device comprises a first channel, wherein the second switching device comprises a second channel, and wherein the compensation resistor is designed to have a value based on: The corresponding designed resistance values ​​of the first switching device and the second switching device, A portion of the design current flowing in the first channel, or A portion of the designed valley current threshold current flows in the second channel.

3. The DC / DC converter of claim 1 , wherein the first switching device comprises a first channel, wherein the second switching device comprises a second channel, and wherein the resistance value R1 of the compensation resistor is defined by: Where α is the percentage of the current flowing through the first switching device that flows through the first channel, in is the drain-source resistance of the first switching device, Where W sd2 is the width of the second switching device, where β is the percentage of the current flowing through the second switching device that flows through the second channel, and Where R′ ds，sd2 is the drain-source resistance of the second switching device.

4. The DC / DC converter of claim 1, wherein a resistance value of the compensation resistor increases monotonically with an increase in a temperature of the compensation resistor.

5. The DC / DC converter of claim 1 , wherein the resistance value of the compensation resistor is between at least one of the following ranges for T<80° C.: 30Ω and 100Ω, 50Ω and 90Ω, and 60Ω and 80Ω, and between at least one of the following ranges for T>80° C.: 60Ω and 200Ω, 60Ω and 150Ω, and 70Ω and 140Ω.

6. The DC / DC converter of claim 1 , wherein the resistance value of the compensation resistor and the resistance value of at least one of the first switching device and the second switching device are temperature dependent, having substantially the same resistance divided by temperature slope for T<80° C.

7. The DC / DC converter of claim 1, wherein a series resistance of the second switching device and the compensation resistor differs from an inverse of a resistance of the first switching device by less than 5%.

8. The DC / DC converter of claim 7, wherein the first switching device comprises a first transistor having a first gate configured to receive a first gate voltage, wherein the second switching device comprises a second transistor having a second gate configured to receive a second gate voltage, and wherein the first gate voltage is equal to the second gate voltage.

9. The DC / DC converter of claim 1, wherein when the DC / DC converter operates at a temperature of 80°C, a series resistance of the second switching device and the compensation resistor differs from a resistance of the first switching device by less than 5%.

10. The DC / DC converter of claim 1, wherein the compensation resistor comprises a third switching device.

11. The DC / DC converter of claim 10, wherein the first switching device comprises a first transistor having a first gate configured to receive a first gate voltage, wherein the second switching device comprises a second transistor having a second gate configured to receive a second gate voltage, wherein the third switching device comprises a third transistor having a third gate configured to receive a third gate voltage, and wherein the first gate voltage, the second gate voltage, and the third gate voltage are equal.

12. A converter circuit comprising: a high-side device coupled to the switch node and configured to selectively electrically couple the switch node to a high input voltage node based on a high-side control signal; a low-side device coupled to the switch node and configured to selectively electrically couple the switch node to a low input voltage node based on a low-side control signal; an inductor coupled between the switch node and an output node of the converter circuit; a first switch and a compensation resistor coupled in series with the first switch; a comparator configured to compare a reference voltage to a voltage equal to a sum of a voltage at the switch node and a voltage drop across the first switch and the compensation resistor, the comparator configured to generate a valley current threshold signal based in part on an output of the comparator, the valley current threshold signal indicating that a valley current provided to the inductor has dropped below a threshold current limit; as well as A controller is configured to generate a high-side control signal and a low-side control signal based in part on the valley current threshold signal. 13 . The converter circuit of claim 12 , wherein a resistance of the first switch and the compensation resistor differs from an inverse of a resistance of the low-side device by less than 5%.

14. The converter circuit of claim 12, wherein the first switch comprises a first transistor having a first gate configured to receive a first gate voltage, wherein the low-side device comprises a second transistor having a second gate configured to receive a second gate voltage, and wherein the first gate voltage is equal to the second gate voltage.

15. The converter circuit of claim 12, wherein the compensation resistor comprises a second switch.

16. The converter circuit of claim 15, wherein the first switch includes a first gate configured to receive a first gate voltage equal to the gate voltage of the low-side device, and wherein the second switch includes a second gate configured to receive a second gate voltage equal to the gate voltage of the low-side device.

17. The converter circuit of claim 12, wherein the first switch and the compensation resistor have a first voltage drop, wherein the low-side device has a second voltage drop, and wherein the first voltage drop is within 5% of the second voltage drop.

18. A method of controlling a DC / DC converter, the method comprising: generating a valley current threshold current flowing in a series connection including a first switching device and a compensation resistor; generating a first voltage value based on a valley current threshold current and a series resistance of the first switching device and the compensation resistor; comparing the first voltage value and a reference voltage using a comparator to generate an error signal based on the comparison; as well as Based in part on the error signal, conductivity of a low-side switching device of the DC / DC converter is controlled.

19. The method of claim 18, wherein the first switching device comprises a first transistor having a first gate configured to receive a first gate voltage, wherein the low-side switching device comprises a second transistor having a second gate configured to receive a second gate voltage, and wherein the first gate voltage is equal to the second gate voltage. 20 . The method of claim 19 , wherein the compensation resistor comprises a third transistor having a third gate configured to receive a third gate voltage, and wherein the third gate voltage is equal to the first gate voltage and the second gate voltage.

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