A few kinds of commonly used MOSFET drive circuit in switch power source

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MOSFET connects internal resistance because of guiding rate of low, switch is rapid in waiting for an advantage to be applied extensively at switch power source. The drive of MOSFET often chooses appropriate circuit according to the parameter of power source IC and MOSFET. MOSFET is discussed to be used at the drive circuit of switch power source together below. When use MOSFET designs switch power source, major person meets those who consider MOSFET to guide the the electrify block, biggest voltage, biggest electric current. But a lot of moment also considered these factors merely, such circuit perhaps can work normally, but not be a good design program. More meticulous, MOSFET still should consider the parameter of itself parasitism. To an affirmatory MOSFET, its drive circuit, the peak value electricity that drive foot exports, ascendant rate, can affect the switch performance of MOSFET. After be in charge of make choice of when power source IC and MOS, the drive circuit with right choice will join power source IC and MOS canal appear especially important. A good MOSFET drive circuit has the following demand: (1) switch is in charge of enlightened instantaneous, drive circuit should be offerred enough big charging current makes MOSFET bar source extremely voltage rises quickly to place to require a cost, make sure switch canal can debut quickly and the high frequency oscillation of nonexistent ascendant edge. (2) switch guides during connecting, drive circuit can assure MOSFET bar the voltage between source pole keeps stable and guide reliably. (3) closes instantaneous drive circuit to be able to offer as far as possible the access of low impedance offers MOSFET bar the quick release of voltage of the capacitance between source pole, make sure switch canal can close quickly. (Structure of 4) drive circuit is simple reliable, loss is small. (5) brings to bear on according to the circumstance segregation. The commonly used MOSFET drive circuit in power source of a few module introducing below. 1, direct drive of IC of 　 power source of MOSFET of direct drive of graph 1 IC of MOSFET of direct drive of power source IC is our most commonly used drive means, also be the simplest drive way at the same time, use means of this kind of drive, should note a few parameter and the effect of these parameter. The first, examine manual of power source IC, its are the biggest electric current of drive peak value, because of different chip, drive capability is very much moment is different. The 2nd, understand the parasitism electric capacity of MOSFET, if pursue 1 in the value of C1, C2. If the value of C1, C2 is greater, MOS canal guides the energy of the need that understand is compared big, if power source IC does not have electric current of bigger drive peak value, so pipe guides the rate that know is compared slow. If drive capacity is insufficient, ascendant edge may appear high frequency oscillation, although the graph 1 in Rg is reduced, insoluble also problem! Size of capacitance of parasitism of IC drive ability, MOS, MOS provides the element such as switch speed, affect the choice that drive resistor block is worth, so Rg can be not reduced indefinitely. 2, when capacity of drive of power source IC is insufficient if choose MOS to provide parasitism electric capacity bigger, when the drive ability of interior of power source IC is not worth again, need enhances drive ability on drive circuit, often use totem pole circuit to increase capacity of drive of power source IC, if its circuit pursues place of casing of 2 dotted line is shown. Graph action of circuit of this kind of drive depends on 　 of MOS of drive of 2 totem pole, promotion electric current provides capability, finish what input capacitance charge to grid quickly to charge process. This kind of develop attacks increased to guide the time of the need that know place, but decreased to pass time, switch canal can debut quickly and the high frequency oscillation that avoids ascendant edge. 3, drive circuit quickens MOS canal to close time to pursue 3 quicken MOS to close to close instantaneous drive circuit to be able to offer as far as possible the access of low impedance offers MOSFET bar voltage of the capacitance between source pole is fast release, make sure switch canal can close quickly. To make bar source extremely the quick release of capacitance voltage, often go up in drive resistor shunt-wound a resistor and a diode, if the graph is shown 3 times, among them D1 is commonly used is fast restore diode. This makes close time to reduce, reduce the loss when closing at the same time. Rg2 is the electric current when preventing those who close too big, give burn-up power source IC. Graph 4 improve model quicken MOS to close to also have in the totem pole circuit that introduced at 2 o'clock accelerate involve action. When the drive capacity of power source IC is sufficient, to the graph 2 in circuit is improved can quicken MOS canal to pass time, get 4 show circuit is like a graph. Come with dynatron release bar source extremely capacitance voltage is commonner. If of Q1 blast off to do not have resistor extremely, guide when PNP dynatron when connecting, bar source extremely capacitance weak point is received, achieve put charge inside the shortest time, utmost reduces the alternate loss when closing. With the graph 3 develop attack to be compared, still have a profit, it is bar the electric current when the charge release on the capacitance between source pole does not pass power source IC, raised dependability. 4, drive circuit quickens MOS canal to close time to pursue the drive that 5 segregation drive shows high-end MOS 5 times to be in charge of to if pursue,be satisfied, classics regular meeting introduces transformer drive, also use transformer drive to satisfy safe segregation sometimes. Among them R1 purpose is to restrain the inductance of the parasitism on PCB board and C1 to form LC oscillation, the purpose of C1 is to separate dc, pass communication, also can prevent magnetism core saturation at the same time. Besides above drive circuit, still have the drive circuit of form of a lot of other. Doing not have circuit of a kind of drive to various drive circuit is best, combine specific applying only, choose the most appropriate drive. CNC Milling CNC Machining