CN114362488B - Power tube driving control circuit and driving control method - Google Patents
Power tube driving control circuit and driving control method Download PDFInfo
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Abstract
The invention provides a power tube driving control circuit and a driving control method, comprising the following steps: the first driving module is used for providing a first driving current for the grid electrode of the power tube so as to control the conduction of the power tube, wherein the first driving current is smaller than a preset value; the second driving module is configured to provide a second driving current for the grid electrode of the power tube from a first moment, and the first moment is positioned in a second stage before the end of the miller platform; wherein the capacitance of the miller capacitance is smaller in the first stage of the miller stage than in the second stage of the miller stage. According to the invention, on the premise of ensuring that the switching speed of the power tube is unchanged (namely, the condition of not influencing the EMI), the second stage of capturing the Miller platform of the power tube by detecting the drain voltage of the power tube is realized, and when the drain voltage of the power tube drops below the reference voltage, the driving capability is enhanced, so that the turn-on loss and the turn-on loss are reduced, the efficiency is improved, and the EMI is not influenced.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a power tube driving control circuit and a driving control method.
Background
In most of the applications of high-power switching power supplies, in order to match with the EMI (electro magnetic interference ) effect or to meet the EMI mass production consistency, it is common practice to adjust the current driving capability of the on-power MOSFET (SJ MOSFET, silicon superjunction transistor) to be weak so as to achieve better EMI characteristics. As shown in fig. 1, the output end of the driving module 1 is connected to the gate of the power MOSFET Q1 via a resistor Ra, and two ends of the resistor Ra are connected in parallel with a diode D and a resistor Rb in series, wherein the cathode of the diode D is connected to the driving module 1, and the anode is connected to the gate of the power MOSFET Q1 via the resistor Rb; the resistance value of the resistor Ra is made larger, so that the driving current flowing through the resistor Ra can be reduced, and the effect of reducing EMI interference is achieved.
As shown in fig. 2, for the power MOSFET, during the turn-on process, the miller plateau, i.e., the interval t2-t4, is generated during the turn-on process due to the miller capacitance, and the gate-source voltage VGS remains unchanged. Due to the nature of power MOSFETs, especially SJ MOSFETs, there are two segments of Crss and Coss (t 2-t3 depletion longitudinally, t3-t4 depletion laterally), and when the drain-source voltage VDS drops to a certain value, the lateral capacitance becomes very large (t 3-t4 lateral capacitance), which may be hundreds of times the value of VDS at high voltage (before t 3). In order to match with the EMI effect, the driving capability in the prior art is very weak, and the interval from t3 to t4 becomes very long, which tends to cause the increase of the turn-on loss (t 3 to t 4) and the turn-on loss (t 4 to t5, rdson reduction zone), thereby affecting the overall efficiency and the power MOSFET temperature.
Therefore, how to reduce the turn-on loss and turn-on loss of the power MOSFET without affecting the EMI effect has become one of the problems to be solved by those skilled in the art.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a power tube driving control circuit and a driving control method, which are used for solving the problem that the EMI effect, the turn-on loss and the turn-on loss cannot be considered in the prior art.
To achieve the above and other related objects, the present invention provides a power tube driving control circuit, including at least:
the first driving module is used for providing a first driving current for the grid electrode of the power tube so as to drive the power tube to be conducted, wherein the first driving current is smaller than a preset value;
the second driving module is configured to provide a second driving current to the grid electrode of the power tube from a first moment, and the first moment is positioned in a second stage before the end of the miller platform;
wherein the capacitance of the miller capacitance is smaller in the first stage of the miller stage than in the second stage of the miller stage.
Optionally, the second driving module is configured to detect a drain-source voltage of the power tube, and provide a second driving current to the gate of the power tube when the drain-source voltage is less than a reference voltage.
More optionally, from the first time, the first driving current and the second driving current are supplied together to the gate of the power tube to drive the power tube.
More optionally, the second drive current is greater than the first drive current.
More optionally, from the first time, the first driving current stops being supplied to the gate of the power tube, and the second driving current is used to drive the power tube.
Optionally, the first driving module includes a first driving tube connected between a supply voltage and a gate of the power tube, the first driving tube being turned on when a PWM control signal of the power tube is active to provide a conduction path for the first driving current, and turned off when the PWM control signal is inactive; the power supply circuit further comprises a second driving tube connected between the grid electrode of the power tube and the reference ground, wherein the second driving tube is turned on when the PWM control signal is invalid so as to provide an energy release path for the grid electrode of the power tube, and is turned off when the PWM control signal is valid.
More optionally, the first driving module includes a driving control unit, a first resistor, a second resistor, and a diode; the driving control unit generates a driving signal of the power tube based on the PWM control signal; one end of the first resistor is connected with the output end of the drive control unit, and the other end of the first resistor is connected with the grid electrode of the power tube; one end of the second resistor is connected with the output end of the drive control unit, and the other end of the second resistor is connected with the cathode of the diode; and the anode of the diode is connected with the grid electrode of the power tube.
Optionally, the second driving module includes:
the sampling unit is configured to sample the drain-source voltage of the power tube when the power tube is conducted so as to generate a sampling signal; a comparison unit configured to compare the sampling signal with a reference signal; and
and a second driving current generating unit configured to generate the second driving current when the sampling signal is smaller than the reference signal, and stop generating the second driving current when the sampling signal is larger than the reference signal.
More optionally, the sampling unit includes: the top cutting unit is configured to output a signal representing the drain-source voltage of the power tube when the power tube is turned on, and output a preset voltage when the power tube is turned off; wherein the preset voltage is greater than the reference signal;
the sampling unit further includes: and the voltage dividing unit is used for dividing the output signal of the topping unit so as to generate the sampling signal, wherein the sampling signal is proportional to the output signal of the topping unit.
More optionally, the topping unit includes a first switching tube and a voltage source; the first end of the first switch tube is connected with the drain electrode of the power tube, the control end of the first switch tube is connected with the voltage source, and the second end of the first switch tube is connected with the voltage dividing unit.
More optionally, the second driving current generating unit includes a second switching tube and a third switching tube; the second switching tube is controlled by the output signal of the comparison unit, and is conducted when the sampling signal is smaller than the reference signal; the third switching tube is controlled by the voltage of the first end of the second switching tube, and is conducted when the second switching tube is conducted so as to provide a conducting path for the second driving current.
More optionally, the second driving current generating unit includes a third resistor, a fourth resistor, a second switching tube and a third switching tube; one end of the third resistor is grounded, and the other end of the third resistor is connected with the first end of the second switching tube; the control end of the second switching tube is connected with the output end of the comparison unit, and the second end of the second switching tube is connected with the power supply voltage through the fourth resistor; the first end of the third switching tube is connected with the power supply voltage, the control end of the third switching tube is connected with the second end of the second switching tube, and the second end of the third switching tube is connected with the grid electrode of the power tube.
More optionally, the second driving module further includes a pull-down unit; the pull-down unit is connected to the output end of the comparison unit, and turns off the second driving current when the power tube is turned off.
More optionally, the pull-down unit includes a pull-down tube, a first end of the pull-down tube is connected to the output end of the comparing unit, a control end receives an inverse signal of the PWM control signal, and a second end is grounded.
To achieve the above and other related objects, the present invention provides a power tube driving control method, which at least includes:
providing a first driving current to drive the power tube so as to conduct the power tube, wherein the first driving current is smaller than a preset value so as to reduce electromagnetic interference of the power tube;
providing a second driving current for the grid electrode of the power tube from a first moment along with the decrease of the drain-source voltage of the power tube, wherein the first moment is positioned in a second stage before the end of the Miller platform so as to strengthen the driving capability;
wherein the capacitance of the miller capacitance is smaller in the first stage of the miller stage than in the second stage of the miller stage.
Optionally, comparing the drain-source voltage of the power tube with a reference voltage, and providing the second driving current when the drain-source voltage of the power tube is smaller than the reference voltage.
More optionally, from the first time, the first driving current and the second driving current are supplied together to the gate of the power tube to drive the power tube.
More optionally, the second drive current is greater than the first drive current.
More optionally, from the first time, the first driving current stops being supplied to the gate of the power tube, and the second driving current is used to drive the power tube.
Optionally, the second drive current is turned off when the power transistor is turned off.
As described above, the power tube driving control circuit and the driving control method of the present invention have the following advantages:
the power tube driving control circuit and the driving control method of the invention capture the second stage of the miller platform of the power tube by detecting the drain-source voltage of the power tube on the premise of ensuring the switching speed of the power tube to be unchanged (namely, the condition of not influencing the EMI), and strengthen the driving capability when the drain-source voltage of the power tube is smaller than the reference voltage, thereby reducing the turn-on loss and the turn-on loss, improving the efficiency and having no influence on the EMI.
Drawings
Fig. 1 is a schematic diagram showing a circuit structure for realizing a good EMI characteristic in the prior art.
Fig. 2 is a waveform diagram showing the gate-source voltage, drain-source voltage and drain current of a prior art power MOSFET.
Fig. 3 is a schematic diagram of a power tube driving control circuit according to the present invention.
Fig. 4 is a schematic diagram of another structure of the power tube driving control circuit of the present invention.
Fig. 5 is a schematic diagram of a power tube driving control method according to the present invention.
Description of element reference numerals
1. Driving module
2. Power tube driving control circuit
21. First driving module
211. Drive control unit
22. Second driving module
221. Sampling unit
221a roof cutting unit
221b voltage dividing unit
222. Comparison unit
223. Second driving current generating unit
224. Pull-down unit
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
Please refer to fig. 3-5. It should be noted that, the illustrations provided in the present embodiment merely illustrate the basic concept of the present invention by way of illustration, and only the components related to the present invention are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.
Example 1
As shown in fig. 3, the present embodiment provides a power tube driving control circuit 2 for driving a power tube Q1, wherein for simplicity of illustration, the source of the power tube Q1 is connected to the reference ground, and the drain-source voltage is the drain-source voltage. It should be understood that, when the source electrode of the power transistor Q1 floats, those skilled in the art can make foreseeable corresponding changes to the driving control circuit to be applicable, which falls within the protection scope of the present invention. The power tube drive control circuit 2 includes:
the first driving module 21 and the second driving module 22.
As shown in fig. 3, the first driving module 21 provides a first driving current to the gate of the power tube Q1 to control the power tube Q1 to be turned on, wherein the first driving current is smaller than a preset value. As an example, the first drive current is typically 3-50 mA.
Specifically, in the present embodiment, the first driving module 21 includes a first driving tube Q2, a second driving tube Q3; the first driving tube Q2 is connected between a power supply voltage VDD and a grid electrode of the power tube Q1, and is turned on when a PWM control signal of the power tube Q1 is effective so as to provide a conduction path for the first driving current, and is turned off when the PWM control signal is ineffective; the second driving tube Q3 is connected between the gate of the power tube Q1 and the ground, and is turned on when the PWM control signal is inactive, to provide an energy release path for the gate of the power tube Q1, and is turned off when the PWM control signal is active. The first end of the first driving tube Q2 is connected with a power supply voltage VDD, and the second end of the first driving tube Q2 is connected with the second end of the second driving tube Q3; the first end of the second driving tube Q3 is grounded; the control ends of the first driving tube Q2 and the second driving tube Q3 receive inverse signals of PWM control signals for controlling the on and off of the power tube Q1; in this embodiment, the first driving tube Q2 is a PMOS tube, and the second driving tube Q3 is an NMOS tube; at this time, the first end of the first driving tube Q2 is a source, the second end is a drain, and the control end is a gate; the first end of the second driving tube Q3 is a source electrode, the second end is a drain electrode, and the control end is a grid electrode; in practical use, the types of the devices of the first driving tube Q2 and the second driving tube Q3 may be selected according to needs, which is not limited to the present embodiment. As an example, the first driving module 21 further includes two inverters for receiving a PWM control signal and providing an inverse of the PWM control signal. When the PWM control signal is at a high level, the first driving transistor Q2 is controlled to be turned on, so that a first driving current is provided to the power transistor Q1 from the power supply voltage VDD via the first driving transistor Q2; when the PWM control signal is at a low level, the second driving transistor Q3 is controlled to be turned on, so as to turn off the power transistor Q1, so as to provide an energy release path for the gate of the power transistor Q1. In actual use, the relation between the level of the PWM control signal and the working state of the power tube can be set according to the need, which is not limited by the present embodiment; for example, when the first driving transistor Q2 is an NMOS transistor and the second driving transistor Q3 is a PMOS transistor, the gates of the two transistors are directly controlled by the PWM control signal.
It should be noted that, the on-resistance Ron of the first driving tube Q2 is larger, so that the first driving current provided by the first driving module 21 is smaller than a preset value, so as to reduce electromagnetic interference of the power tube. The preset value may be set according to a specific circuit structure and device parameters, which are not described in detail herein.
As shown in fig. 3, the second driving module 22 is configured to provide a second driving current to the gate of the power tube Q1 when the power tube Q1 reaches the second stage of the miller stage. It should be noted that, as described above, the miller stage is divided into a first stage and a second stage, the first stage being V GS The value of the Miller capacitance at high voltage is smaller, namely the stage t2-t3 in the figure 2; the second stage isV GS Unchanged but drain-source voltage V DS Having fallen to a small value, the abrupt change at low voltage of the miller capacitance is large, i.e. stage t3-t4 in fig. 2. It should be appreciated that there are a variety of ways to determine the power tube entering the second stage of the miller stage, such as by detecting V DS Is determined by the rate of change of (V when entering the second stage) DS The rate of change of (2) is greatly reduced compared with the first stage), and can also be directly detected by detecting V DS For SJ MOSFETs, generally referred to as V DS Falling below 50V and beginning to enter the second stage. Thus, V can be easily recovered by DS Detecting, when it drops to the reference voltage, controlling the second driving module 22 to supply the second driving current to the gate of the power transistor Q1, the method only detecting the drain-source voltage V DS The implementation is simpler. In order to ensure that the switching tube enters the second stage when the second driving current is provided, the reference voltage needs to be less than 50V, for example, 10-20V.
In the present embodiment, after the power transistor Q1 reaches the second stage of the miller stage, the first driving current and the second driving current are commonly supplied to the gate thereof to increase the driving capability. The second drive current is set to be greater than the first drive current, and is 200mA as an example. Of course, it will be appreciated by those skilled in the art that after the power transistor Q1 reaches the second stage of the miller stage, the first drive current may cease to be provided, and only the second drive current may be provided to the gate of the power transistor Q1. Since the second drive current is much larger than the first drive current, the drive capability of the second stage can also be improved. Therefore, a person skilled in the art can make adaptive changes to the driving circuit of the present invention, so as to achieve the object, and these adaptive changes are all within the protection scope of the present invention.
Specifically, the second driving module 22 includes a sampling unit 221, a comparing unit 222, and a second driving current generating unit 223.
More specifically, the sampling unit 221 is configured to sample the drain-source voltage V of the power transistor Q1 when the power transistor Q1 is turned on DS Obtaining a sampling signal Vd; since the present invention is exemplified by a source ground, the present inventionI.e. sampling drain voltage V DS . In this embodiment, the sampling unit 222 includes a truncated unit 221a and a voltage dividing unit 221b. The input end of the clipping unit 221a is connected to the drain electrode of the power tube Q1, when the power tube Q1 is turned on, the voltage of the output end of the clipping unit 221 is consistent with the voltage of the drain electrode of the power tube Q1, and when the power tube Q1 is turned off, the voltage Vs of the output end of the clipping unit 221 is clamped at a preset voltage. As an example, the topping unit 221a includes a first switching tube Q4 and a voltage source V1; the first end of the first switch tube Q4 is connected to the drain electrode of the power tube Q1, the control end is connected to the voltage source V1, and the second end is connected to the voltage dividing unit 221b; in this embodiment, the first switching tube Q4 is an NMOS tube, where a first end of the first switching tube Q4 is a drain electrode, a second end is a source electrode, and a control end is a gate electrode; in practical use, the device type of the first switching tube Q4 may be selected according to needs, which is not limited by the embodiment. When the power tube Q1 is conducted, the drain voltage of the power tube Q1 is pulled down, the first switch tube Q4 is conducted, and the second end voltage Vs of the first switch tube Q4 is equal to the drain voltage of the power tube Q1; when the power tube Q1 is turned off, the drain voltage of the power tube Q1 is pulled high, the first switch tube Q4 is turned off, and the second end voltage Vs of the first switch tube Q4 is clamped at a preset voltage V1-Vth, where V1 is a voltage value of the voltage source, and Vth is a gate-source threshold voltage of the first switch tube Q4. It should be appreciated that when the switching tubes in the skiving unit 221 are other types of switching tubes, the preset voltage may also be v1+vth. As an example, the preset voltage is greater than the reference signal.
The voltage dividing unit 221b is for avoiding the received drain-source voltage V DS Is too large to exceed the chip supply voltage VDD, thereby providing a drain-source voltage V for reception DS Dividing to obtain the characterization drain-source voltage V DS Is provided for the sampling signal Vd. Specifically, the voltage dividing unit 221b is connected to the output terminal of the topping unit 221a, and divides the signal at the output terminal of the topping unit 221a, so as to generate the sampling signal Vd, where the sampling signal Vd is proportional to the output signal of the topping unit 221 a. As an example, the voltage dividing unit 221b includes a first resistor R6 and a second resistor R7, where the first resistor R6 and the second resistor R7 are connected in series between the output end of the topping unit 221a and the reference ground, so as to generate a sampling signal Vd at a common connection end of the first resistor R6 and the second resistor R7, where vd= kVs, k is a proportionality coefficient of the voltage dividing unit. Any circuit structure capable of dividing the signal at the output end of the topping unit 221 is suitable, and will not be described in detail herein.
More specifically, the comparing unit 222 compares the sampling signal Vd with the reference signal REF, and in this embodiment, an inverting input terminal of the comparing unit 222 is connected to an output terminal of the sampling unit 221, and a non-inverting input terminal is connected to the reference signal REF, so as to obtain a comparison result of the sampling signal Vd and the reference signal REF. The comparison unit 222 outputs a high level when the sampling signal Vd is smaller than the reference signal REF, and the comparison unit 222 outputs a low level when the sampling signal Vd is greater than the reference signal REF. It will be appreciated that the reference signal REF is thus set in dependence on the drain-source voltage corresponding to the start of the second stage of the Miller stage and the scaling factor of the voltage divider unit, the setting of the reference signal REF being required to ensure the drain-source voltages V of the different power MOSFETs in order to meet the chip compatibility with the different power MOSFETs DS When the sampled signal falls to the reference signal REF, the second stage of the miller stage is entered. Further, as described above, when the power transistor Q1 is turned off, the sampling signal vd= kVs =k (V1-Vth), at which time Vd is desirably larger than the reference signal REF, that is, the setting of the voltage source V1 needs to cause the comparing unit 222 to always output a low level when the power transistor Q1 is turned off.
More specifically, the second driving current generating unit 223 is connected between the output terminal of the comparing unit 222 and the gate of the power transistor Q1, and provides the second driving current when the sampling signal Vd is smaller than the reference signal REF, and turns off when the sampling signal Vd is greater than the reference signal REF.
In the present embodiment, the second driving current generating unit 223 includes a second switching tube Q5 and a third switching tube Q6; wherein the second switching tube Q5 is controlled by the output signal of the comparing unit 222, and is turned on when the sampling signal Vd is smaller than the reference signal REF; the third switching tube Q6 is controlled by the voltage of the first end of the second switching tube Q5, and is turned on when the second switching tube Q5 is turned on, so as to provide a conduction path for the second driving current.
As an example, the second driving current generating unit 223 includes a third resistor R3, a fourth resistor R4, a second switching tube Q5, and a third switching tube Q6. One end of the third resistor R3 is grounded, and the other end of the third resistor R3 is connected with the first end of the second switching tube Q5; the control end of the second switching tube Q5 is connected to the output end of the comparing unit 222, and the second end is connected to the supply voltage VDD via the fourth resistor R4; the first end of the third switching tube Q6 is connected with the power supply voltage VDD, the control end of the third switching tube Q6 is connected with the second end of the second switching tube Q5, and the second end of the third switching tube Q6 is connected with the grid electrode of the power tube Q1. In this embodiment, the second switching tube Q5 is an NMOS tube, and the third switching tube Q6 is a PMOS tube; at this time, the first end of the second switching tube Q5 is a source electrode, the second end is a drain electrode, and the control end is a gate electrode; the first end of the third switching tube Q6 is a source electrode, the second end is a drain electrode, and the control end is a grid electrode; in practical use, the device types of the second switching tube Q5 and the third switching tube Q6 may be selected according to the needs, which is not limited by the embodiment. When the comparison result is high level, the second switching tube Q5 is turned on, the control end of the third switching tube Q6 is pulled down, the third switching tube Q6 is turned on, the power supply voltage VDD provides a second driving current for the gate of the power tube Q1 through the third switching tube Q6, and the on-resistance Ron of the third switching tube Q6 is smaller, so that the second driving current is larger than the first driving current. In this embodiment, the driving current of the power tube Q1 is the sum of the first driving current and the second driving current, so that the power tube Q1 passes through the saturation region and the linear region rapidly, thereby improving efficiency. When the comparison result is low level, the second switching tube Q5 is turned off, the control end of the third switching tube Q6 is pulled high, and the third switching tube Q6 is turned off and no current is output. It should be appreciated that in other embodiments, the second drive current may be provided separately, with the first drive current not being active at this time. As another example, the second driving current generating unit 223 further includes a fifth resistor R5, where the fifth resistor R5 is connected between the second end of the third switching tube Q6 and the gate of the power tube Q1, and is used to limit the magnitude of the second driving current, so as to avoid the second driving current from being too large to damage the power tube Q1.
Specifically, as another implementation of the present invention, the second driving module 22 further includes a pull-down unit 224. The pull-down unit 224 is connected to the output end of the comparing unit 222, and turns off the second driving current when the power transistor Q1 is turned off. As an example, the pull-down unit 224 includes a pull-down tube Q7, where a first end of the pull-down tube Q7 is connected to the output end of the comparing unit 222, a control end receives an inverse signal of the PWM control signal, and a second end is grounded; in this embodiment, the pull-down tube Q7 is an NMOS tube, and at this time, the first end of the pull-down tube Q7 is a drain, the second end is a source, and the control end is a gate; in practical use, the device type of the pull-down tube Q7 may be selected according to needs, which is not limited to the present embodiment. As an example, the pull-down unit 224 further includes an inverter, where an input terminal of the inverter receives the PWM control signal, and an output terminal of the inverter is connected to the control terminal of the pull-down tube Q7, and is configured to provide an inverse signal of the PWM control signal. When the power tube Q1 is turned off, the pull-down tube Q7 is turned on to pull the output of the comparing unit 222 low, so as to turn off (disable) the second driving module 22; when the power tube Q1 is turned on, the pull-down tube Q7 is turned off, and the second driving current generating unit 223 generates the second driving current based on the output result of the comparing unit 222; in practical use, the relationship between the level of the PWM control signal and the on state of the pull-down tube can be set according to the need, which is not limited by the present embodiment.
In this embodiment, the first driving module 21 and the second driving module 22 are integrated in the same chip, and the power transistor Q1 is also integrated in the chip.
Example two
As shown in fig. 4, the present embodiment provides a power tube driving control circuit 2, which is different from the first embodiment in that the first driving module 21 is a module for driving the power tube Q1 in a general driving chip; the second driving module 22 is added on the basis of the original general driving chip, and is used for increasing the driving current of the second stage of the miller stage.
Specifically, the first driving module 21 includes a driving control unit 211, and the driving control unit 211 generates a driving signal of the power tube Q1 based on a PWM control signal; in order to adapt to the driving requirements of different switching tubes, a first resistor R1, a second resistor R2 and a diode D are required to be externally connected, one end of the first resistor R1 is connected to the output end of the driving control unit 211, and the other end is connected to the gate of the power tube Q1. One end of the second resistor R2 is connected to the output end of the driving control unit 211, and the other end is connected to the cathode of the diode D; the anode of the diode D is connected with the grid electrode of the power tube Q1.
It should be noted that other structures are the same as those of the first embodiment, and are not described in detail herein. In this embodiment, the first driving module 21 provides the power tube Q1 with a first driving current smaller than a preset value in a series resistance current limiting manner, the second driving module 22 is separately integrated in a chip, and the first driving module 21 and the power tube Q1 are disposed outside the chip.
It should be understood that when the power tube starts to be conducted, the first driving current is used to drive the power tube, and when the drain-source voltage of the power tube drops below the reference voltage through detection, that is, in the second stage before the miller platform is finished, the second driving current is used to drive the power tube, wherein the second driving current is larger than the first driving current, so that the turn-on loss and the conduction loss are further reduced. The above embodiments only show two implementations of the driving current, and other circuits that can provide the driving current to the power tube can be applied in the present invention, and the present invention does not limit the generation of the driving current.
Example III
As shown in fig. 5, the present embodiment provides a power tube driving control method, which is implemented based on the power tube driving control circuit 2 of the first embodiment or the second embodiment, and any hardware or software capable of implementing the method is suitable for practical use; the power tube driving control method comprises the following steps:
providing a first driving current to drive the power tube so as to conduct the power tube, wherein the first driving current is smaller than a preset value so as to reduce electromagnetic interference of the power tube;
with the drain-source voltage V of the power tube DS And when the second stage of the Miller platform is reached, providing a second driving current to drive the power tube so as to strengthen the driving capability.
It should be noted that, the first moment provides the second driving current to the gate of the power tube, and the first moment is located in the second stage before the end of the miller stage; wherein the capacitance of the miller capacitance is smaller in the first stage of the miller stage than in the second stage of the miller stage.
As an example, the second drive current is greater than the first drive current. Starting from the first moment, stopping the first driving current from being supplied to the grid electrode of the power tube, wherein the second driving current is used for driving the power tube; or from the first moment, the first driving current and the second driving current are supplied to the grid electrode of the power tube together so as to drive the power tube.
Specifically, in this embodiment, the drain-source voltage of the power tube is compared with a reference voltage, and when the drain-source voltage of the power tube is smaller than the reference voltage, it is determined that the power tube reaches the second stage of the miller stage.
As shown in fig. 5, at time t0, the first driving module 21 starts to operate to supply a first driving current to the power tube Q1, and the gate-source voltage V of the power tube Q1 GS Beginning to slowly increase, and at the moment, the power tube Q1 is in an off state; the gate-source voltage V of the power tube Q1 at the time t1 GS Greater than the threshold voltage V of the power tube Q1 TH When the power tube Q1 starts to conduct, the drain current I of the power tube Q1 D Starts to increase slowly, and the drain-source voltage V of the power tube Q1 DS Start to decrease slowly; with the arrival of time t2, the gate-source voltage V GS Reach V Plat I.e. the miller plateau voltage is reached, the drain current I of the power tube Q1 D Constant. In the first stage of the miller stage (i.e., during t2-t 3), the drain-source voltage V DS The falling rate of (2) is relatively fast, and from the time t3, the Miller capacitance is increased along with V DS The step-down abrupt change is large, and the step-down abrupt change starts to enter the second stage of the Miller platform, and the drain-source voltage V DS The descent speed of (2) decreases. At time t3a, the drain-source voltage V DS When the voltage drops below the reference voltage Vref, the second driving module 22 starts to operate. That is, the drain-source voltage V of the power tube Q1 DS When the reference voltage Vref is greater than the reference voltage Vref, the power tube Q1 is driven to provide smaller driving capability based on the first driving current provided by the first driving module 21, and the first driving current is set to 3 mA-50 mA as an example to meet the EMI requirement. When the drain-source voltage V of the power tube Q1 DS When the reference voltage Vref is smaller than the reference voltage Vref, the first driving module 21 and the second driving module 22 operate simultaneously to drive the power tube Q1 by the sum of the first driving current and the second driving current, so that the gate voltage V of the power tube Q1 is from time t3a GS Rapidly rises, and at the time t4, the power tube is completely conducted. Wherein the dotted line at the time t3a to t6 is V when the second driving current is not increased GS From the change curve of (2), it can be seen that when the second driving current is not increased, the miller stage ends from the time t5 to the time t6, and the power tube is completely turned on, that is, by adopting the two-stage driving method of the embodiment of the invention, the driving time can be shortened, and the turn-on loss can be reduced. When the power tube is completely turned on (i.e. after time t 4), the driving current may be the sum of the first driving current and the second driving current, or may be other values, which is not limited by the present invention. When the power tube is turned off, the first driving current and the second driving current are turned off.
Example IV
As shown in fig. 3 and 4, the present embodiment provides a switching power supply system, including:
the switching power supply circuit and the power tube drive control circuit 2 according to the first or second embodiment.
Specifically, the power tube driving control circuit 2 obtains a feedback signal from the switching power supply circuit, and generates a driving control signal DRV for controlling the power tube Q1 in the switching power supply circuit. In this embodiment, the switching power supply circuit only illustrates the inductor T1, the power tube Q1, and the sampling resistor Rcs, and other devices and connection relationships are set based on a specific structure; as an example, the inductor T1 is a primary winding of a transformer, the power transistor Q1 is a silicon super junction transistor, and the sampling resistor Rcs is connected to a source of the power transistor Q1. The switching power supply circuit includes, but is not limited to, a BUCK structure, a BOOST structure, a BUCK-BOOST structure, a fliback structure, etc., and any power supply structure controlled by a switch is suitable for the present invention, and is not described in detail herein.
The power tube driving control circuit and the driving control method adopt the II-stage driving reinforcing circuit under the condition that the switching speed (10% -90%) is completely consistent, the circuit is in a CCM (continuous conduction mode) or QR (quasi-resonance mode) state, the corresponding full-load efficiency is obviously improved, the loss of the power tube is greatly reduced, the temperature of the power tube is improved, the overall efficiency of the system is improved, and the EMI is not affected.
In summary, the present invention provides a power tube driving control circuit and a driving control method, including: the first driving module is used for providing a first driving current for the grid electrode of the power tube so as to control the conduction of the power tube, wherein the first driving current is smaller than a preset value; the second driving module is configured to provide a second driving current to the grid electrode of the power tube from a first moment, and the first moment is positioned in a second stage before the end of the miller platform; wherein the capacitance of the miller capacitance is smaller in the first stage of the miller stage than in the second stage of the miller stage. According to the power tube driving control circuit and the driving control method, on the premise that the switching speed of the power tube is unchanged (namely, the condition that the EMI is not influenced), the second stage of the Miller platform of the power tube is captured by detecting the drain voltage of the power tube, and when the drain voltage of the power tube is smaller than the reference voltage, the driving capability is enhanced, so that the turn-on loss and the turn-on loss are reduced, the efficiency is improved, and the EMI is not influenced. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.
Claims (18)
1. A power tube drive control circuit, characterized in that the power tube drive control circuit comprises:
the first driving module is used for providing a first driving current for the grid electrode of the power tube so as to drive the power tube to be conducted, wherein the first driving current is smaller than a preset value;
the second driving module is configured to provide a second driving current to the grid electrode of the power tube from a first moment, and the first moment is positioned in a second stage before the end of the miller platform; the second driving module includes: the sampling unit is configured to sample the drain-source voltage of the power tube when the power tube is conducted so as to generate a sampling signal; a comparison unit configured to compare the sampling signal with a reference signal; a second driving current generating unit configured to generate the second driving current when the sampling signal is smaller than the reference signal, and stop generating the second driving current when the sampling signal is larger than the reference signal; the pull-down unit is connected to the output end of the comparison unit, and turns off the second driving current when the power tube is turned off;
wherein the capacitance of the miller capacitance in the first stage of the miller platform is smaller than the capacitance of the miller platform in the second stage; the first stage of the miller stage, the power tube is longitudinally depleted; and in the second stage of the Miller platform, the power tube is transversely exhausted.
2. The power tube driving control circuit according to claim 1, wherein: the second driving module is configured to detect a drain-source voltage of the power tube, and provide a second driving current to a gate of the power tube when the drain-source voltage is less than a reference voltage.
3. The power tube driving control circuit according to claim 1 or 2, wherein: the first driving current and the second driving current are supplied to the gate of the power tube together from the first time to drive the power tube.
4. The power tube driving control circuit according to claim 1 or 2, wherein: the second drive current is greater than the first drive current.
5. The power tube driving control circuit according to claim 4, wherein: from the first time, the first driving current stops being supplied to the grid electrode of the power tube, and the second driving current is used for driving the power tube.
6. The power tube driving control circuit according to claim 1, wherein: the first driving module comprises a first driving tube connected between a power supply voltage and a grid electrode of the power tube, the first driving tube is conducted when a PWM control signal of the power tube is effective so as to provide a conduction path for the first driving current, and the first driving tube is turned off when the PWM control signal is ineffective; the power supply circuit further comprises a second driving tube connected between the grid electrode of the power tube and the reference ground, wherein the second driving tube is turned on when the PWM control signal is invalid so as to provide an energy release path for the grid electrode of the power tube, and is turned off when the PWM control signal is valid.
7. The power tube driving control circuit according to claim 1, wherein: the first driving module comprises a driving control unit, a first resistor, a second resistor and a diode; the driving control unit generates a driving signal of the power tube based on the PWM control signal; one end of the first resistor is connected with the output end of the drive control unit, and the other end of the first resistor is connected with the grid electrode of the power tube; one end of the second resistor is connected with the output end of the drive control unit, and the other end of the second resistor is connected with the cathode of the diode; and the anode of the diode is connected with the grid electrode of the power tube.
8. The power tube driving control circuit according to claim 1, wherein: the sampling unit includes: the top cutting unit is configured to output a signal representing the drain-source voltage of the power tube when the power tube is turned on, and output a preset voltage when the power tube is turned off; wherein the preset voltage is greater than the reference signal;
the sampling unit further includes: and the voltage dividing unit is used for dividing the output signal of the topping unit so as to generate the sampling signal, wherein the sampling signal is proportional to the output signal of the topping unit.
9. The power tube driving control circuit according to claim 8, wherein: the topping unit comprises a first switching tube and a voltage source; the first end of the first switch tube is connected with the drain electrode of the power tube, the control end of the first switch tube is connected with the voltage source, and the second end of the first switch tube is connected with the voltage dividing unit.
10. The power tube driving control circuit according to claim 1, wherein: the second driving current generating unit comprises a second switching tube and a third switching tube; the second switching tube is controlled by the output signal of the comparison unit, and is conducted when the sampling signal is smaller than the reference signal; the third switching tube is controlled by the voltage of the first end of the second switching tube, and is conducted when the second switching tube is conducted so as to provide a conducting path for the second driving current.
11. The power tube driving control circuit according to claim 1, wherein: the second driving current generating unit comprises a third resistor, a fourth resistor, a second switching tube and a third switching tube; one end of the third resistor is grounded, and the other end of the third resistor is connected with the first end of the second switching tube; the control end of the second switching tube is connected with the output end of the comparison unit, and the second end of the second switching tube is connected with the power supply voltage through the fourth resistor; the first end of the third switching tube is connected with the power supply voltage, the control end of the third switching tube is connected with the second end of the second switching tube, and the second end of the third switching tube is connected with the grid electrode of the power tube.
12. The power tube driving control circuit according to claim 1, wherein: the pull-down unit comprises a pull-down tube, a first end of the pull-down tube is connected with the output end of the comparison unit, a control end receives a reverse signal of the PWM control signal of the power tube, and a second end of the pull-down tube is grounded.
13. A power tube driving control method, implemented based on the power tube driving control circuit according to any one of claims 1-12, characterized in that the power tube driving control method at least comprises:
providing a first driving current to drive the power tube so as to conduct the power tube, wherein the first driving current is smaller than a preset value so as to reduce electromagnetic interference of the power tube;
providing a second driving current for the grid electrode of the power tube from a first moment along with the decrease of the drain-source voltage of the power tube, wherein the first moment is positioned in a second stage before the end of the Miller platform so as to strengthen the driving capability;
wherein the capacitance of the miller capacitance in the first stage of the miller platform is smaller than the capacitance of the miller platform in the second stage; the first stage of the miller stage, the power tube is longitudinally depleted; and in the second stage of the Miller platform, the power tube is transversely exhausted.
14. The power tube driving control method according to claim 13, wherein: comparing the drain-source voltage of the power tube with a reference voltage, and providing the second driving current when the drain-source voltage of the power tube is smaller than the reference voltage.
15. The power tube driving control method according to claim 13 or 14, characterized in that: the first driving current and the second driving current are supplied to the gate of the power tube together from the first time to drive the power tube.
16. The power tube driving control method according to claim 13 or 14, characterized in that: the second drive current is greater than the first drive current.
17. The power tube driving control method according to claim 16, wherein: from the first time, the first driving current stops being supplied to the grid electrode of the power tube, and the second driving current is used for driving the power tube.
18. The power tube driving control method according to claim 13, wherein: the second drive current is turned off when the power tube is turned off.
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