Background technology
In prior art, because the fet power switch device has characteristics such as driving is easy, switching speed is fast and is used widely in the Power Conversion field.The fet power switch device can be divided into enhancement mode and depletion type two classes, but used fet power switch device mostly is the enhancement mode switching device in Switching Power Supply or the switching power converter at present, turning on and off of it is that pulse width modulating signal by control Driver Circuit provides is controlled, and the amplitude of this pulse width modulating signal is generally 0~15V.That is to say that when the high level of the about 15V of control Driver Circuit output, the enhancement mode switching device is open-minded, when the low level that is output as near 0V, the enhancement mode switching device ends, so existing control Driver Circuit is only applicable to control the enhancement mode switching device.
In recent years, fast as switching speed, the conducting internal resistance is low, withstand voltage high because the semiconductor gallium nitride switching device has the performance characteristics of many excellences, thereby be subjected to the industry extensive concern.But be limited to present manufacturing process, the gallium nitride switching device can only be made depletion type switching element.The characteristics of depletion type switching element are just can conducting near zero the time at its grid, voltage between source electrodes, have only when negative voltage reaches certain value between its grid, source electrode and could turn-off, this just brings difficulty to control, if it is directly applied in existing Switching Power Supply or the switching power converter, situation about can not turn-off will occur.Want the depletion type gallium nitride switching device of function admirable is applied to existing Switching Power Supply or switching power converter, at first should solve the open and close control problem of depletion type switching element.The applicant the Chinese patent of first to file " a kind of can reliable turn-off enhancing-depletion device combinational (application number: 201010112286.4) " solved the open and close control problem of depletion type switching element preferably, can reliable turn-off depletion type gallium nitride switching device.But its turn-off speed is fast inadequately, because the turn-off speed of this unit switch device depends on the size that flows through the depletion type switching element electric current, and the size of this electric current depends on the size of circuit load, again because when load is light, the electric current that flows through depletion type switching element is less, make that the charging current of equivalent capacity is also less between the leakage of enhancement mode switching device, source electrode, thereby cause the turn-off speed of depletion type switching element slow, make the fast characteristics of gallium nitride switching device switching speed be difficult to performance.Therefore, the gallium nitride switching device will obtain the engineering application and give full play to the fast excellent properties of its switching speed, also should solve the problem that it turn-offs fast.
Summary of the invention
The objective of the invention is at the problem that exists in the prior art, but provide a kind of drive circuit of quickly switching off depletion type switching element, emphasis solves its problem of turn-offing fast when being intended to solve the depletion type switching element controllability, next is the security reliability problem with drive circuit opened fast that solves depletion type switching element, thereby depletion type switching element can be applied in Switching Power Supply and the switch converters better.
For achieving the above object, technical scheme of the present invention is as follows:
It mainly comprises a P-channel enhancement type switching device, N channel enhancement switching device and be connected on resistance on these two switching device grids, the drain electrode of the drain electrode of described P-channel enhancement type switching device and N channel enhancement switching device is joined, the source electrode of described P-channel enhancement type switching device directly or by a resistance is connected on the power supply of this drive circuit, the source electrode of described N channel enhancement switching device directly or reference of receiving circuit by a resistance, the grid of described P-channel enhancement type switching device joins by resistance on its grid and signal input end, and the grid of described N channel enhancement switching device joins by resistance on its grid and signal input end.
Further improved technical scheme of the present invention is as follows:
Diode in parallel on the resistance of described P-channel enhancement type switching device, the grid of the negative electrode of this diode and P-channel enhancement type switching device joins, the input of its anode and control signal joins, another diode in parallel on the resistance of described N channel enhancement switching device, the grid of the anode of this diode and N channel enhancement switching device joins, and the input of its negative electrode and control signal joins.
By technique scheme as can be seen, the present invention is connected in series P raceway groove and two enhancement mode switching devices of N raceway groove Q1, Q2, they are alternate conduction under the control of pulse width modulating signal, and will control turning on and off of depletion type switching element between the leakage of N channel enhancement switching device Q2, grid that voltage between source electrodes oppositely is added in depletion type switching element Q3, source electrode.The characteristics of this drive circuit are to pass through the leakage of the electric current while of two branch roads to N channel switches device Q2 when the control depletion type switching element turn-offs, parasitic capacitance charging between source electrode, the electric current of one of them branch road is directly to be provided by P-channel enhancement type switching device Q1 by supply voltage VCC, the influence that it is not changed by circuit load, can make charging voltage reach the required grid of depletion type switching element fast, shutoff negative voltage between source electrode, make its quick shutoff, and still can be when depletion type switching element turn-offs by the leakage of P-channel enhancement type switching device Q1 continuation to N channel switches device Q2, the reliable thoroughly shutoff of depletion type switching element has been guaranteed in parasitic capacitance charging between source electrode.The present invention further one of improvement is a difference parallel diode on the resistance of two enhancement mode switching devices, the one, can quicken the quick conducting of N channel enhancement switching device Q2, and accelerate the speed of opening of depletion type switching element; The 2nd, can avoid the conducting simultaneously of the moment when open and close are changed of two switching devices and produce straight-through phenomenon, guarantee the reliability of drive circuit works.Therefore, the present invention has solved opening fast of depletion type switching element and quick shutoff problem preferably, particularly turn-offs problem fast, can give full play to the fireballing characteristics of depletion type gallium nitride switching device open and close, and is simultaneously, safe and reliable.
Embodiment
Below in conjunction with accompanying drawing structure of the present invention and operation principle thereof are elaborated.
Embodiment 1
Referring to Fig. 1, this drive circuit is by a P-channel enhancement type switching device Q1 (hereinafter to be referred as P-channel device) and a N channel enhancement switching device Q2 (hereinafter to be referred as the N channel device) and be connected on resistance R 1 on these two switching device grids, R2 forms, the drain D of the drain D of P-channel device Q1 and N channel device Q2 is joined, the source S of P-channel device Q1 directly is connected on the power supply VCC of this drive circuit, the source S of N channel device Q2 connects with reference to ground, the grid G of P-channel device Q1 is joined by its resistance R1 and drive control signal input A, the grid of described N channel device Q2 joins by its resistance R2 and drive control signal input A, and the signal output part of this signal input end A and external control drive circuit 1 joins.The drain D of described N channel device Q2 and depletion type switching element Q3 source S are joined, the grid G of the source S of N channel device and depletion type switching element Q3 is joined, thereby makes between the leakage of N channel device Q2, grid that voltage between source electrodes oppositely is added to depletion type switching element Q3, source electrode.
Its operation principle is: the signal input end A point of being delivered to this drive circuit by the control Driver Circuit 1 output pulse width modulation signal PWM of outside.When control Driver Circuit 1 output high level, the grid of P-channel device Q1 is put height, makes grid, the voltage between source electrodes of Q1 approaching zero, and then Q1 ends; Meanwhile, this high level signal charges by the parasitic capacitance of resistance R 2 between N channel device Q2 grid G and source S, when this charging voltage reaches its conducting voltage, and then N channel device Q2 conducting, the leakage of Q2, voltage between source electrodes be near zero, makes depletion type switching element Q3 conducting.When control Driver Circuit 1 output low level, the grid G of N channel device Q2 is changed to low level, and then Q2 ends; Meanwhile, the grid of P-channel device Q1 also is changed to low level, then the reverse current of power supply VCC is by the grid of resistance R 1 to Q1, parasitic capacitance charging between source electrode, when this charging voltage reaches the conducting voltage of Q1, the Q1 conducting, then power supply VCC leaks to N channel switches device Q2 through the electric current of the Q1 electric current that provides and the depletion type switching element of flowing through (also turn-off this moment) simultaneously, parasitic capacitance quick charge between source electrode, along with Q2 leaks, the fast rise of voltage between source electrodes, be applied to the Q3 grid, reverse voltage between source electrode also increases fast, when being increased to the shutoff negative voltage of Q3, Q3 turn-offs.Depletion type switching element Q3 closes and to have no progeny, and P channel switches device Q1 keeps conducting state, and VCC continues parasitic capacitance charging between leakage, source electrode to N channel switches device Q2, thereby has guaranteed that Q3 turn-offs required negative voltage, guarantees the reliable thoroughly shutoff of Q3.
By above-mentioned operation principle as can be seen, in the turn off process of depletion type switching element Q3, supply voltage VCC is through Q1 parasitic capacitance charging between Q2 leakage, source electrode, the size of its charging current is not subjected to the influence of circuit load, can make that Q2 leaks, charging voltage reaches the shutoff voltage of Q3 fast between source electrode, thereby Q3 is turn-offed fast.This shows that this drive circuit has not only been realized the control that depletion type switching element is opened and turn-offed, simultaneously, also have the characteristics of quickly switching off depletion type switching element.
Embodiment 2
Referring to Fig. 2, this example is on the basis of embodiment 1, diode D1 in parallel on the resistance R1 of P-channel enhancement type switching device Q1, the grid of the negative electrode of this diode D1 and P-channel enhancement type switching device Q1 joins, the input A of its anode and control signal joins, another diode D2 in parallel on the resistance R2 of described N channel enhancement switching device Q2, the grid of the anode of this diode D2 and N channel enhancement switching device Q2 joins, and the input A of its negative electrode and control signal joins.
Its operation principle is: when control Driver Circuit 1 output high level, and diode D1 conducting, then this high level signal ends Q1 by the grid that diode D1 is added to P-channel device Q1 rapidly fast; Meanwhile, diode D2 ends, and then this high level signal is by the parasitic capacitance charging of resistance R 2 between N channel device Q2 grid G and source S, when this charging voltage reaches conducting voltage between grid, source electrode, then N channel device Q2 conducting makes depletion type switching element Q3 conducting then.When control Driver Circuit 1 output low level, diode D2 conducting, this low level is moved the grid G of Q2 to low level rapidly by diode D2, and Q2 is ended fast; Meanwhile, low level drags down the grid potential of P-channel device Q1, the Q1 conducting, then power supply VCC is through the parasitic capacitance charging between the leakage of N channel device Q2, source electrode simultaneously of the electric current of the electric current that Q1 provides and the depletion type switching element Q3 that flows through (also turn-off this moment), when this charging voltage reached the shutoff voltage of Q3, Q3 turn-offed.
By above-mentioned operation principle as can be seen, in the process that high level control depletion type switching element Q3 opens, high level can be added to the grid of Q1 immediately by the diode D1 of conducting, Q1 is turn-offed fast, because the quick shutoff of Q1, can make the quick conducting of Q2 (because for avoiding two switch Q1, Q2 series connection straight-through, Q2 is preferably in Q1 and closes the conducting of having no progeny, so closing fast, Q1 has no progeny, Q2 just can be after it conducting fast), then make the Q3 can be open-minded fast, thereby make this drive circuit have the advantages that to open depletion type switching element fast.
In addition, also can avoid the series connection of two switching devices straight-through, improve the reliability of this circuit working by diode D1, D2 are set.Its principle is: when high level arrives, for Q1, this high level is added to the Q1 grid fast by the diode D1 of conducting, Q1 is turn-offed rapidly, and for Q2, this high level is then by resistance R 2 parasitic capacitance charging between the grid of Q2, source electrode, just conducting when this charging voltage reaches the conducting voltage of Q2, guarantee that Q2 closes the hysteresis conducting of having no progeny at Q1, thereby avoided this branch current straight-through; In like manner, when low level arrives, for Q2, this low level is moved the grid of Q2 to low level fast by conducting diode D2, and then Q2 turn-offs rapidly, and for Q1, when low level is put an end of resistance R 1 when low, power supply VCC is by resistance R 1 parasitic capacitance charging between the grid of Q1, source electrode, just conducting when this charging voltage reaches the conducting voltage of Q1, guaranteed that also Q1 closes the just conducting of having no progeny at Q2, thereby also avoided the series connection of two switching devices straight-through.
Embodiment 3
Referring to Fig. 3, in order further to improve the fail safe and the reliability of this drive circuit, current-limiting resistance R3 of series connection on the source electrode of described P-channel enhancement type switching device Q1 flows through the maximum current of switching device Q1 with restriction.
Embodiment 4
Referring to Fig. 4; in order further to improve the practicality of this drive circuit; a current sampling resistor Rs can connect on the source electrode of described N channel enhancement switching device Q2; can sample to the electric current that flows through switching device by this sampling resistor Rs; and can implement to protect or electric current is controlled to it by the control circuit of outside, it is operated under the safe current.
Embodiment 5
Referring to Fig. 5, provided the application example of this drive circuit among the figure, this circuit is the step-up DC-DC converter of current control mode, promptly be this drive circuit in the wherein empty frame, it and depletion type switching element Q3 can substitute original enhancement mode switching device, and they have been finished under the control of original control Driver Circuit 1 and have opened fast and the function of turn-offing fast.Experiment shows that the present invention can not only make this converter operate as normal, and switch performance is superior, safe and reliable.