CN210123938U - Power tube driving circuit - Google Patents
Power tube driving circuit Download PDFInfo
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- CN210123938U CN210123938U CN201921537606.3U CN201921537606U CN210123938U CN 210123938 U CN210123938 U CN 210123938U CN 201921537606 U CN201921537606 U CN 201921537606U CN 210123938 U CN210123938 U CN 210123938U
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Abstract
The utility model provides a drive circuit of power tube relates to the power electronic transform field. Before the power tube is turned off, partial charges of the grid electrode of the power tube are discharged in advance through a pre-closing process, and therefore the power tube is turned off at the beginning. And adaptively adjusting the starting time of the pre-closing in the next period according to the time interval between the ending time of the pre-closing in the current period and the turn-off time of the power tube. The method can effectively ensure the smooth start and end of the pre-closing by adaptively adjusting the start time of the pre-closing, and particularly can ensure that the start time and the end time of the pre-closing can be adaptively adjusted in DCM, CCM and even depth CCM when being applied to driving a synchronous rectification power tube, thereby ensuring the smooth start and end of the pre-closing.
Description
Technical Field
The utility model relates to a power electronic transform field, more specifically relates to a power tube drive circuit.
Background
With the development of electronic technology, power transistors are used as switching elements in circuits, and the power transistors are increasingly used. However, in an application circuit such as synchronous rectification, the power tube always has the problem that the turn-off speed is too slow. If the more gate charges Qg need to be discharged when the power tube is turned off, the more the gate (G) to source (S) voltage V of the power tubeGSThe longer the transition time down to 0V, the slower the speed at which the power tube is turned off.
The slow turn-off speed of the power tube can bring adverse effects to the circuit where the power tube is located, especially in the ordinary flyback synchronous rectification circuit shown in fig. 1. FIG. 2 is a waveform diagram corresponding to FIG. 1, and it can be seen from FIG. 2 that the drain-source voltage V of the synchronous rectification power tubeDSLag time T from negative voltage to 0V voltage to real turn-off of synchronous rectification power tubedly_sumConsisting of two parts, i.e. zero volt comparator response time Tdly_cmpAnd the grid source voltage V of the synchronous power tubeGSTransition time T down to 0Vdly_gs. If the more grid charges Qg need to be discharged when the synchronous rectification power tube is turned off, Tdly_gsThe longer the time, the slower the power tube turn-off speed. Due to the turn-off lag of the synchronous rectification power tube, before the synchronous rectification power tube is completely turned off, reverse current flows from the drain electrode to the source electrode through the leakage inductance of the transformer (such as the Iout waveform of figure 2) to generate leakage inductance energy; after the synchronous rectification power tube is switched off, the leakage inductance and the output capacitance of the synchronous rectification power tube form resonance, and the drain-source voltage V of the synchronous rectification power tubeDSA leakage inductance spike voltage (point 2 in fig. 2) is generated. Especially in Continuous Current Mode (CCM), if the leakage inductance energy generated by the non-timely turn-off is very large, the peak voltage of the leakage inductance is very high (e.g. point 2 in fig. 2), and exceeds the breakdown voltage of the synchronous rectification power tube, which may cause the breakdown of the synchronous rectification power tube and damage to the system.
SUMMERY OF THE UTILITY MODEL
In view of the above, the present invention discloses a driving circuit of a power transistor; the power tube is pre-closed, redundant input charges of the grid electrode of the power tube are discharged in advance, the turn-off speed of the power tube can be greatly improved, and the defect that the power tube and a system are damaged due to turn-off lag in the prior art is overcome.
The utility model discloses a power tube driving circuit, which comprises a detection module, a pre-closing execution circuit module, a power tube switch signal generation module and a control logic module;
the output end of the detection module is connected with the control logic module, two control signal output ends of the control logic module are respectively connected with the pre-closing execution circuit module and the power tube switching signal generation module, and the output ends of the pre-closing execution circuit module and the power tube switching signal generation module are both connected with the grid electrode of the power tube;
the detection module is used for detecting the drain-source voltage V of the power tubeDS(ii) a The pre-closing execution circuit module is used for pre-closing the conducted power tube, namely, before the power tube is closed, part of charges of a grid electrode of the power tube are discharged in advance; the power tube switching signal generating module is used for periodically generating a first signal for switching on the power tube and a second signal for switching off the power tube; the control logic module comprises a self-adaptive adjusting module which is used for generating a third signal for starting the pre-closing execution circuit module and a fourth signal for stopping the pre-closing execution circuit module; the output end of the power tube switching signal generating module is connected with the self-adaptive adjusting module; the adaptive adjusting module can adjust the pre-closing starting time t1 of the next period triggering third signal according to the size of the time interval td between the pre-closing ending time t2 of the current period generating the fourth signal and the power tube turning-off time t3 of the current period generating the second signal.
Preferably, the adaptive adjusting module at least comprises a time comparing module and a pre-closing starting time generating module; the time comparison module is used for comparing the time interval td in the current period with a first time threshold Tth1And a second time threshold Tth2And generates the next cycle pre-shutdown start-up time t1The regulation control signal of (2); wherein the first time threshold Tth1And a second time threshold Tth2Is a fixed parameter set in advance, and a first time threshold Tth1Greater than a second time threshold Tth2(ii) a And the pre-closing starting moment generation module is used for generating a time sequence signal corresponding to the t1 moment according to the adjusting control signal.
Preferably, the time comparison module comprises an input end of a first enabling signal; the first enable signal is active high for the time interval td of the current cycle; the input end of the first enabling signal is connected with the control end of the first switch tube, and the input end of the first enabling signal is connected with the control end of the second switch tube after passing through the NOT gate; one end of the first switch tube is connected to a voltage source VDD through a first current source, the other end of the first switch tube is grounded through a first capacitor, and the first capacitor is connected with the second switch tube in parallel; the connection point of the first switch tube and the first capacitor is also connected with the positive input ends of a first comparator and a second comparator; the negative input end of the first comparator is connected with a first voltage threshold value Vth1The negative input end of the second comparator is connected with a second voltage threshold value Vth2(ii) a Wherein the first voltage threshold Vth1Is the first time threshold Tth1The voltage threshold value converted into, the second voltage threshold value Vth2Is the second time threshold Tth2The converted voltage threshold; the time comparison module also comprises an n-bit counter which is used for generating the adjusting control signal according to the output values of the first comparator and the second comparator.
Preferably, the n-bit counter comprises an add-one signal input, a hold signal input, and an n-bit output; the signal output end of the first comparator is connected with the plus one signal input end, and the inverted signal output end of the first comparator and the signal output end of the second comparator are connected to the holding signal input end through an AND gate; when the holding signal is at high level, the output of n bits is kept unchanged; when the holding signal is at low level and the adding signal is at high level, the n-bit output executes an adding action; and when the holding signal and the adding signal are both in a low level, the n-bit output of the holding signal and the adding signal performs a subtraction action, and the n-bit counter is set to be triggered to perform the operation of counting the value only when the first enabling signal changes from an active high level to an inactive low level.
Preferably, the pre-shutdown starting time generation module comprises an input end of a second enabling signal; the second enabling signal is effective between the time when the power tube is conducted in the next period and the pre-closing starting time t1 in the next period; the input end of the second enable signal is connected with the control end of the third switching tube, and the input end of the second enable signal is connected with the control end of the fourth switching tube after passing through the NOT gate; one end of the third switching tube is connected to the voltage source VDD through a second current source, the other end of the third switching tube is grounded through n parallel controlled capacitor circuits, and the controlled capacitor circuits are also connected with the fourth switching tube in parallel; each controlled capacitor circuit is formed by connecting a time-base capacitor and a time-base switching tube in series; the control ends of the n time-base switch tubes are correspondingly connected with the n bit outputs of the n bit counter one by one; the connection point of the controlled capacitor circuit and the third switching tube is also connected to the positive input end of a third comparator; the negative input end of the third comparator is connected with a reference voltage Vref(ii) a When the output signal of the third comparator is high, the next cycle pre-shutdown starting time t1 is reached.
Preferably, the control logic module further comprises an inflection point detection module; the input end of the inflection point detection module is connected with the detection module and is used for detecting the drain-source voltage V of the power tube during the pre-closing period of the power tubeDSThe inflection point of (a); the output end of the inflection point detection module is connected with the self-adaptive adjusting module, and the self-adaptive adjusting module detects the drain-source voltage V of the power tube in the inflection point detection moduleDSGenerating a fourth signal to stop the pre-shutdown execution circuit.
Preferably, a zero-volt voltage comparator is further included in the control logic module; the input end of the zero-volt voltage comparator is connected with the detection moduleConfigured to continuously determine the drain-source voltage V of the power tubeDSWhether a zero crossing is reached; the zero-volt voltage comparator detects the drain-source voltage V of the power tubeDSWhen the zero crossing point is changed from positive voltage to negative voltage, triggering the power tube switch signal generating module to generate a first signal for conducting the power tube; when the drain-source voltage V of the power tube is detectedDSAnd when the voltage is changed from the negative voltage to the zero crossing point of the positive voltage, triggering the power tube switching signal generation module to generate a second signal for turning off the power tube.
Preferably, the pre-close execution circuit comprises a controllable switch and a current source which are connected in series between the grid electrode and the source electrode of the power tube, or the pre-close execution circuit comprises a controllable switch and a resistor which are connected in series between the grid electrode and the source electrode of the power tube; wherein the controllable switch is controlled by the adaptive adjustment module.
Preferably, the power tube driving circuit is used for driving a synchronous rectification power tube in a synchronous rectification circuit.
Preferably, when the synchronous rectification circuit is an active clamp flyback synchronous rectification circuit or an LLC resonant synchronous rectification circuit, a lower limit value of the pre-shutdown start-up time t1 in the current cycle is also set in the adaptive adjustment module, and the lower limit value is half of the on-time period ton of the power tube switch in the previous cycle.
Drawings
The above and other objects, features and advantages of the present disclosure will be more readily understood from the following description of embodiments thereof with reference to the accompanying drawings. The drawings are only for the purpose of illustrating the principles of the disclosure. In the drawings:
fig. 1 shows a synchronous rectified switching power supply configuration;
FIG. 2 illustrates a prior art synchronous rectification control principle waveform diagram;
fig. 3 shows a block diagram of the power transistor driving circuit according to the present invention;
FIG. 4 shows the drain-source resistance R after the power transistor is turned onDS(on) and VGSA relationship diagram of (1);
fig. 5 shows an embodiment of a pre-shutdown execution circuit module in the present invention;
fig. 6(a) shows an embodiment of the time comparison module in the adaptive adjustment module of the present invention;
fig. 6(b) shows an embodiment of the pre-close start time generation module in the adaptive adjustment module of the present invention;
FIG. 7 illustrates the use of a power tube driver circuit in a synchronous rectifier circuit;
FIG. 8 is a waveform diagram of circuit parameters when the power tube driving circuit is used for a synchronous rectification circuit;
fig. 9 shows a waveform of the current output in an active clamp flyback or LLC resonant switching power supply;
Detailed Description
Exemplary embodiments of the present disclosure will be described hereinafter with reference to the accompanying drawings. In the interest of clarity and conciseness, not all features of an actual embodiment are described in the specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions may be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another.
Here, it should be further noted that, in order to avoid obscuring the present disclosure with unnecessary details, only the device structure closely related to the scheme according to the present disclosure is shown in the drawings, and other details not so related to the present disclosure are omitted.
It is to be understood that the disclosure is not limited to the described embodiments, as described below with reference to the drawings. In this context, embodiments may be combined with each other, features may be replaced or borrowed between different embodiments, one or more features may be omitted in one embodiment, where feasible.
Fig. 3 shows a block diagram of a power tube driving circuit according to an embodiment of the present invention.
As shown in fig. 3, the power tube driving circuit of the present invention includes a detection module 1, a pre-closing execution circuit 2, a power tube switch signal generation module 3, and a control logic module 4. The control logic module 4 includes an inflection point detecting module 41, a zero-volt comparator 42, and an adaptive adjusting module 43.
The detection module 1 detects the drain-source voltage V of the power tubeDSTo a knee detection block 41 and a zero volt voltage comparator 42 in the control logic block 4. The detection module 1 may adopt a voltage detection circuit in the prior art, and is not limited in particular.
The zero-volt comparator 42 is used for detecting the drain-source voltage V of the power tubeDSAnd if the zero crossing point is reached, the output end of the zero crossing point is connected with the power tube switch signal generating module 3.
The power tube switch signal generating module 3 detects the drain-source voltage V of the power tube at the zero-volt voltage comparator 42DSGenerating a signal for conducting the power tube when the positive voltage changes towards a zero crossing point of the negative voltage; drain-source voltage V at power tubeDSWhen the negative voltage changes to the zero crossing point of the positive voltage, a signal for turning off the power tube is generated.
The output end of the power tube switch signal generating module 3 is connected to the grid of the corresponding power tube and is used for generating a signal capable of directly controlling the power tube to be switched on and off. Meanwhile, the output terminal of the power transistor switch signal generating module 3 is further connected to the adaptive adjusting module 43, and is configured to provide the adaptive adjusting module 43 with an enable signal at time 0 while generating the on power transistor signal, and provide the adaptive adjusting module 43 with an end enable signal at time t3 while generating the off power transistor signal.
The inflection point detecting module 41 is used for detecting the drain-source voltage V of the power tube at the pre-shutdown stage of the power tubeDSIf an inflection point occurs, the output end of the inflection point is connected with the adaptive adjusting module 43.
The adaptive adjusting module 43 may adjust the value of the pre-close start time t1 of the power tube for the next period according to the size of the time interval td between the pre-close end time t2 of the power tube in the current period and the time t3 of the power tube switch signal generating module 3 for generating the close power tube signal.
Further, the adaptive adjustment module 43 is provided with an initial value of the pre-off start time t1 for the power tube in the first period in advance.
The adaptive adjustment module 43 generates a control signal that activates the pre-close execution module when time t1 is reached. FIG. 4 shows the drain-source resistance R of the power transistorDS(on)And gate source voltage VGSAs can be seen from FIG. 4, when the gate-source voltage V of the power transistor is appliedGSFalls to a certain value (after point 4 in fig. 4, its drain-source resistance RDS(on)The resistance value increase slope of (1) is steep, and at the moment of point 4, I can be considered asoutInvariably, from the formula
VDS＝-RDS(on)×Iout(1)
To know that VDSThe voltage will increase negatively, VDSProducing an inflection point (point 4 in fig. 4);
the utility model discloses in, reach the end moment t2 that the power tube of current cycle closed in advance promptly after this inflection point is detected to control logic module, control logic module changes control signal and closes control state in advance, stops holding the discharge to the S end to the G of power tube M1, closes in advance and finishes, and V1 is held in advanceGSAnd remains constant after the end of the pre-close.
The utility model discloses in, a particular embodiment of inflection point detection module 41 does, has preset threshold value V in inflection point detection module 41DS_thNegative, inflection point detect module 41 continuously records V during pre-close phaseDSAnd comparing the value of V sampled at the current timeDS(n) V sampled from the previous timeDS(n-1) difference, and judging whether the difference is less than VDS_thTo immediately judge VDS(n)-VDS(n-1)<VDS_thWhether or not this is true. If yes, V sampled at the moment is describedDSThe voltage point is an inflection point, at the moment, the self-adaptive adjusting module generates a control signal for stopping the pre-closing execution circuit, and the pre-closing of the synchronous rectification power tube is finished.
Adopt the utility model discloses a power tube drive circuit can make wherein zero volt voltage comparator 42 compare and have faster response speed in prior art. This is because V is set after the pre-closing of the power tube is finishedGSRemains constant, RDS(on)Constant, IoutContinuing to decrease, V is given by equation (1)DSStarts to decrease negatively due to the current VGSValue corresponds to RDS(on)Is large, resulting in VDSThe slope of the change is greater than the pre-off period, so the zero volt comparator 42 of the present invention has a faster response speed.
Further, the zero volt comparator 42 is always on if the zero volt comparator 42 detects V at any time during the power tube conduction periodDSAnd the power tube is immediately turned off from the zero crossing point of the change of the negative voltage to the positive voltage, so that the power tube can be protected under the abnormal condition.
Fig. 5 shows an embodiment of the pre-close execution circuit 2 of the present invention, wherein the pre-close execution circuit 2 comprises a controllable switch and a current source I connected in series between the gate and the source of the power transistorpreOr a controllable switch and a resistor R connected in series between the gate and the source of the power tube. The controllable switch is controlled by a pre-closing control signal output by the self-adaptive adjusting module, and when the pre-closing control signal is effective, the controllable switch is switched on, and the grid-source voltage V of the power tubeGSBy means of a current source IpreThe energy is discharged to realize voltage reduction, and when the pre-closing control signal is invalid, the controllable switch is turned off, and VGSThe voltage remains constant.
Fig. 6(a) and 6(b) show two main circuit configurations inside the adaptive adjustment module.
The time comparison module shown in fig. 6(a), wherein the first enable signal t2_ t3_ enable is used to control the on/off of the first switch tube k1 and the second switch tube k 2. The first enable signal t2_ t3_ enable is valid between the pre-shutdown end time t2 of the power tube in the current period and the time t3 when the power tube switch signal generation module 3 generates the shutdown power tube signal.
When the first enable signal t2_ t3_ enable is asserted, the first switch tube k1 is turned on, the second switch tube k2 is turned off, the voltage source VDD is grounded through the first current source I1 and the first capacitor C1, and the voltage Vx at the positive input ends of the first comparator and the second comparator is the voltage at the two ends of the first capacitor C1.
When the first enable signal t2_ t3_ enable changes to a low level, the first switch tube k1 is turned off, the second switch tube k2 is turned on, two ends of the first capacitor C1 are shorted, and the voltage Vx at the positive input ends of the first comparator and the second comparator is grounded through the second switch tube k 2.
Thus, the time interval td between t2 and t3 can be converted to its corresponding voltage value Vx by the first enable signal t2_ t3_ enable and the above-described circuitry controlled thereby, which is active only between times t2 and t 3.
Further, the negative input end of the first comparator is connected with a voltage threshold Vth1The negative input end of the second comparator is connected with a voltage threshold value Vth2(ii) a Wherein the voltage threshold value Vth1And Vth2Respectively, a time threshold value Tth1And Tth2The converted voltage threshold.
The first comparator outputs an ADD signal to an adding signal input end of the n-bit counter, and an inverted signal output end of the first comparator and a signal output end of the second comparator output a HOLD signal to a holding signal input end of the n-bit counter after passing through an AND gate.
Since the voltage Vx is increasing when t2_ t3_ enable is active high, the voltage Vx corresponds to the time interval td between t2 and t3 only at the instant of the transition from active high to inactive low at t2_ t3_ enable,therefore, the n-bit counter is set to be triggered to perform the counting operation only when the first enable signal t2_ t3_ enable changes from high level to low level, and all the rest of the time latches the original value.
The value of an n-Bit counter is kept constant when HOLD is 1, the n-Bit counter performs an adding operation when HOLD is 0 and ADD is 1, and performs a subtracting operation when HOLD is 0 and ADD is 0, resulting in an n-Bit counter value Bit [0: n-1] by generating ADD and HOLD signals by a first comparator and a second comparator.
The pre-shutdown start-up time generation module shown in FIG. 6(b), in which the value of the n-Bit counter is Bit [0: n-1]]For controlling n times in the pre-shutdown startup time generation module respectivelyBase switch tube S0～Sn-1To further control n time-base capacitors CS respectively0～CSn-1Whether it is switched into the circuit. Wherein CSi＝(CS0)i+1，0<i<n-1, e.g. CS02pF, then CS1＝4pF，CS2＝8pF。
In fig. 6(b), the second enable signal 0_ t1_ enable is used to control the on/off of the third switching tube k3 and the fourth switching tube k 4. The second enable signal 0_ t1_ enable is active between time 0 and time t1 in the next cycle, that is, from time 0 when the power transistor switch signal generating module generates the power transistor signal in the next cycle, the second enable signal 0_ t1_ enable becomes active at high level, and when the third comparator outputs high level, that is, at time t1 in the next cycle, the second enable signal 0_ t1_ enable becomes inactive at low level. It should be further noted that the next cycle in fig. 6(b) is referred to relative to the current cycle in fig. 6 (a).
When the second enable signal 0_ t1_ enable is asserted, as shown in FIG. 6(b), the voltage signal Vy is converted by the voltage source VDD, the second current source I2 and the time-base capacitor selectively connected to the circuit by the n-bit counter,
where Ctotal is the sum of the capacitance values of the time-based capacitors selected by the n-bit counter for connection into the circuit.
The voltage signal Vy is input to the positive input terminal of the third comparator, and the reference signal VrefInput to the negative input terminal of the third comparator when the voltage signal Vy is greater than the reference voltage VrefAt this time, the third comparator output goes active high, which is at time t1 when the pre-shutdown circuit is enabled.
Due to the fact thatWith simultaneous reference to voltage VrefIs a fixed voltage value set in advance, and therefore Vy is increasing to a fixed voltage value VrefIs selectively connected to the circuit by the n-bit counterIs determined by the total capacitance Ctotal. Therefore, when the capacitance value connected to the circuit increases in the next cycle, i.e., Ctotal increases, the time t1 when the pre-shutdown circuit is activated in the next cycle is delayed backward relative to the time t1 of the current cycle, and vice versa, the time is advanced.
From the above, the two circuits in fig. 6 jointly realize that the time interval td passing through the time instants of the current periods T2 and T3 is equal to the threshold Tth1And Tth2Is used for adaptively adjusting the time T1 for starting the pre-shutdown circuit in the next period, so that the time interval td is finally at the preset threshold value Tth1And Tth2In the meantime. Meanwhile, in practical applications, the range value of the time interval td after reaching the steady state in the adaptive adjustment control, that is, the range value corresponds to the threshold T, needs to be set according to the hardware circuit usedth1And Tth2Thereby ensuring the turn-off effect of the power tube.
The utility model discloses a power tube drive circuit is particularly useful for among the synchronous rectification switching power supply for drive synchronous rectification power tube.
In a synchronous rectification switching power supply, the shutdown delay of a synchronous rectification power tube can cause damage to the power tube and a system. Although the prior art also proposes a control mode for pre-closing the synchronous rectification power tube, the drain-source voltage V of the synchronous rectification power tube is mainly setDSAs control of pre-shutdown start-up and end. The disadvantage of this method is that when the switching power supply is in CCM (continuous current mode), due to the difference of current continuity, if a single voltage threshold is used to determine the starting moment of pre-shutdown, the drain-source voltage V of the power tube is in deep CCMDSThe threshold voltage cannot be reached until the power tube needs to be turned off, so that pre-turn-off cannot be started, and the leakage inductance peak voltage is very high; if the voltage threshold at the pre-off start-up time is increased in a negative direction in order to allow the deep CCM to enter the pre-off state, the pre-off start-up time is too early in the shallow CCM or DCM (discontinuous current mode), and the time for maintaining the driving voltage of the switching tube at the on threshold voltage point is too long, which results in a low synchronous rectification efficiency.
Fig. 7 is the utility model discloses well power tube drive circuit is in the application of ordinary flyback synchronous rectifier circuit, synchronous rectifier circuit includes transformer T1 at least, is located the switching tube K1 on transformer T1 former limit and is located the synchronous rectification switching tube M1 on transformer T1 secondary side, and the power tube drive circuit who takes the self-adaptation to close in advance connects synchronous rectification switching tube M1 for control M1 open, turn-off and close in advance. The power tube driving circuit is the same as the previous embodiment.
Fig. 8 is a waveform diagram of the operation of the middle power transistor driving circuit of the present invention when it is used in the synchronous rectification circuit.
The utility model discloses can both self-adaptation adjustment in advance close the beginning and end moment at DCM, CCM degree of depth CCM even, avoid adopting threshold voltage as the defect of judgement condition. The utility model can reduce the response time of the zero-volt voltage comparator and the time for turning off the power tube, and compared with the turn-off lag time of figure 8 and figure 2, the total turn-off lag time is greatly shortened; the drain-source voltage V of the synchronous rectification power tube is compared with the point 2 in FIG. 2 through the point 6 in FIG. 8DSThe voltage cannot overshoot, and the effect of protecting the synchronous rectification power tube can be achieved.
Further, the power tube driving circuit of the present invention can also be applied to other topology switching power supply applications besides fig. 7.
In some types of switching power supply applications, such as active clamp flyback switching power supply or LLC resonant switching power supply, I is used during the conduction period of the power tubeoutThe output is sinusoidal, as shown in fig. 9, if only the control strategy of the ordinary flyback switching power supply is used, when the time t1 appears in the first half of the conduction interval of the power tube, V isDSThe waveform of (a) will also show a trend of increasing in the negative direction, and the inflection point detection module 41 will trigger erroneously, resulting in early termination of pre-shutdown of the power tube. Therefore, it is necessary to ensure that the pre-turn-off of the power transistor is started after half of the turn-on interval of the previous switching cycle.
It will be understood that the terms "comprises" and/or "comprising," when used herein, specify the presence of stated features, integers, steps, or components, but do not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.
It is to be understood that features described and/or illustrated with respect to one embodiment may be used in the same or a similar manner in one or more other embodiments, in combination with or instead of the features of the other embodiments, without departing from the spirit of the present disclosure.
The present disclosure has been described in conjunction with specific embodiments, but it should be understood by those skilled in the art that these descriptions are intended to be illustrative, and not limiting, of the scope of the present disclosure. Various modifications and alterations of this disclosure will become apparent to those skilled in the art from the spirit and principles of this disclosure, and such modifications and alterations are also within the scope of this disclosure.
Claims (10)
1. A power tube driving circuit is characterized by comprising a detection module, a control logic module, a pre-closing execution circuit module and a power tube switch signal generation module;
the output end of the detection module is connected with the control logic module, two control signal output ends of the control logic module are respectively connected with the pre-closing execution circuit module and the power tube switching signal generation module, and the output ends of the pre-closing execution circuit module and the power tube switching signal generation module are both connected with the grid electrode of the power tube;
the detection module is used for detecting the drain-source voltage V of the power tubeDS；
The pre-closing execution circuit module is used for pre-closing the conducted power tube, namely, before the power tube is closed, part of charges of a grid electrode of the power tube are discharged in advance;
the power tube switching signal generating module is used for periodically generating a first signal for switching on the power tube and a second signal for switching off the power tube;
the control logic module comprises a self-adaptive adjusting module, and the self-adaptive adjusting module can generate a third signal for starting the pre-closing execution circuit module and a fourth signal for stopping the pre-closing execution circuit module; the output end of the power tube switching signal generating module is connected with the self-adaptive adjusting module; the adaptive adjusting module can adjust the pre-close starting time t1 of the third signal generated in the next period according to the size of the time interval td between the pre-close ending time t2 of the fourth signal generated in the current period and the power tube turn-off time t3 of the second signal generated in the next period.
2. The power tube driving circuit according to claim 1, wherein the adaptive adjusting module at least comprises a time comparing module and a pre-off starting time generating module; the time comparison module is used for comparing the time interval td in the current period with a first time threshold Tth1And a second time threshold Tth2And generating a regulation control signal of the next cycle pre-shutdown starting time t 1; wherein the first time threshold Tth1And a second time threshold Tth2Is a fixed parameter set in advance, and a first time threshold Tth1Greater than a second time threshold Tth2(ii) a And the pre-closing starting moment generation module is used for generating a time sequence signal corresponding to the t1 moment according to the adjusting control signal.
3. The power transistor driving circuit as claimed in claim 2, wherein said time comparison module includes an input terminal for a first enable signal; the first enable signal is active high for the time interval td of the current cycle; the input end of the first enabling signal is connected with the control end of the first switch tube, and the input end of the first enabling signal is connected with the control end of the second switch tube after passing through the NOT gate; one end of the first switch tube is connected to a voltage source VDD through a first current source, the other end of the first switch tube is grounded through a first capacitor, and the first capacitor is connected with the second switch tube in parallel; the connection point of the first switch tube and the first capacitor is also connected with the positive input ends of a first comparator and a second comparator; the negative input end of the first comparator is connected with a first voltage threshold value Vth1Of said second comparatorNegative input end is connected with second voltage threshold value Vth2(ii) a Wherein the first voltage threshold Vth1Is the first time threshold Tth1The voltage threshold value converted into, the second voltage threshold value Vth2Is the second time threshold Tth2The converted voltage threshold; the time comparison module also comprises an n-bit counter which is used for generating the adjusting control signal according to the output values of the first comparator and the second comparator.
4. The power transistor driver circuit of claim 3, wherein said n-bit counter comprises an add-one signal input, a hold signal input, and an n-bit output; the signal output end of the first comparator is connected with the signal input end, and the inverted signal output end of the first comparator and the signal output end of the second comparator are connected with the signal input end after passing through an AND gate; when the holding signal of the n-bit counter is at a high level, the output of n bits of the n-bit counter is kept unchanged; when the holding signal is at low level and the adding signal is at high level, the n-bit output executes an adding action; when the holding signal and the adding signal are both in low level, the n-bit output executes the action of subtracting one; the n-bit counter is set to be triggered to perform the operation of counting the value only when the first enabling signal changes from high-level active to low-level inactive.
5. The power transistor driving circuit as claimed in claim 4, wherein said pre-shutdown start-up time generation module includes an input terminal for a second enable signal; the second enabling signal is effective between the time when the power tube is conducted in the next period and the pre-closing starting time t1 in the next period; the input end of the second enable signal is connected with the control end of the third switching tube, and the input end of the second enable signal is connected with the control end of the fourth switching tube after passing through the NOT gate; one end of the third switching tube is connected to the voltage source VDD after passing through a second current source, the other end of the third switching tube is grounded after passing through n parallel controlled capacitor circuits, and the controlled capacitor circuits and the fourth switching tube are connected simultaneouslyThe switch tubes are connected in parallel; each controlled capacitor circuit is formed by connecting a time-base capacitor and a time-base switching tube in series; the control ends of the n time-base switch tubes are correspondingly connected with the n bit outputs of the n bit counter one by one; the connection point of the controlled capacitor circuit and the third switching tube is also connected to the positive input end of a third comparator; the negative input end of the third comparator is connected with a reference voltage Vref(ii) a When the output signal of the third comparator is high, the next cycle pre-shutdown starting time t1 is reached.
6. The power transistor drive circuit of claim 1,
the control logic module also comprises an inflection point detection module;
the input end of the inflection point detection module is connected with the detection module and is used for detecting the drain-source voltage V of the power tube during the pre-closing period of the power tubeDSThe inflection point of (a);
the output end of the inflection point detection module is connected with the self-adaptive adjusting module, and the self-adaptive adjusting module detects the drain-source voltage V of the power tube in the inflection point detection moduleDSGenerating a fourth signal to stop the pre-shutdown execution circuit.
7. The power transistor drive circuit of claim 1,
the control logic module also comprises a zero-volt voltage comparator;
the input end of the zero-volt voltage comparator is connected with the detection module and is configured to continuously judge the drain-source voltage V of the power tubeDSWhether a zero crossing is reached;
the zero-volt voltage comparator detects the drain-source voltage V of the power tubeDSWhen the zero crossing point is changed from positive voltage to negative voltage, triggering the power tube switch signal generating module to generate a first signal for conducting the power tube; when the drain-source voltage V of the power tube is detectedDSThe power tube switch signal generating module is triggered to generate a second power tube switch-off signal for switching off the power tube when the negative voltage changes to the zero crossing point of the positive voltageA signal.
8. The power transistor driving circuit as claimed in claim 1, wherein the pre-turn-off performing circuit comprises a controllable switch and a current source connected in series between the gate and the source of the power transistor, or the pre-turn-off performing circuit comprises a controllable switch and a resistor connected in series between the gate and the source of the power transistor; wherein the controllable switch is controlled by the adaptive adjustment module.
9. A power transistor driving circuit as claimed in any one of claims 1 to 8, wherein the power transistor driving circuit is adapted to drive a synchronous rectification power transistor in a synchronous rectification circuit.
10. A power transistor driving circuit as claimed in claim 9,
when the synchronous rectification circuit is an active clamping flyback synchronous rectification circuit or an LLC resonant synchronous rectification circuit, a lower limit value of the pre-closing starting time t1 of the current period is also set in the self-adaptive regulation module, and the lower limit value is half of the conduction time period ton of the last period of the synchronous rectification power tube.
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| CN201921537606.3U CN210123938U (en) | 2019-09-16 | 2019-09-16 | Power tube driving circuit |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110492724A (en) * | 2019-09-16 | 2019-11-22 | 安徽省东科半导体有限公司 | A kind of power tube drive circuit and driving method |
| CN111953186A (en) * | 2020-08-12 | 2020-11-17 | 安徽省东科半导体有限公司 | Switching power supply control circuit |
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2019
- 2019-09-16 CN CN201921537606.3U patent/CN210123938U/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110492724A (en) * | 2019-09-16 | 2019-11-22 | 安徽省东科半导体有限公司 | A kind of power tube drive circuit and driving method |
| CN110492724B (en) * | 2019-09-16 | 2024-03-29 | 东科半导体(安徽)股份有限公司 | Power tube driving circuit and driving method |
| CN111953186A (en) * | 2020-08-12 | 2020-11-17 | 安徽省东科半导体有限公司 | Switching power supply control circuit |
| CN111953186B (en) * | 2020-08-12 | 2024-03-29 | 东科半导体(安徽)股份有限公司 | Switching power supply control circuit |
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