(Compositive and 1) , auxiliary slant buy power source, reach primary side and sub side for LM5036 yuan power supply of parts of an apparatus, need not exterior and auxiliary power source, reduce circuit board dimension and cost, conduce to density of implementation high power and good hot dependability.

 

(2) , increase slant beforehand the buy function that start can realize laden belt to press when starting, those who output voltage is drab increase by degrees and avoid to flow backward electric current.

 

(3) , match improvement through pulse pursue restriction of periodic electric current, produce even output electric current to restrict a level inside input voltage limits thereby, and still can prevent transformer saturation.

 

Electric current is protected piece

 

The voltaic limitation that pulse matchs protects a mechanism:

 

Constant current restricts problem and solution:

 

During chasing cycle to move, measure signal ISENSE to achieve when electric flu when threshold value IPOS_LIM, activation CBC electric current restricts an operation. Controller basically is behaved control for mode of peak value electric current, during CBC is operated voltage loop is opened. Pilot of mode of peak value electric current a common problem is to become what half bridge develop attacks to occupy sky comparing to be more than 0.25 (step-down converter is 0.5) when occurrence second harmonic oscillation.

 

Experience law is to increase compensation brae, its slope must set the output inductor electric current that to pass electric current to detect resistor changes primary side declivous at least half. If hope,second harmonic oscillation is eliminated after a switch is periodic, must compensate slope the setting to be one times what output slope of be issued to lower levels of inductance electric current. This is called not to have difference to take control.

 

But, can appear after adding slope to compensate another problem. Voltaic limitation n follows input tension and change, following plan institute are shown. Because differ,the slope compensation extent below input voltage differs, n of limitation of practical electric current follows the input tension that gives in-house electric current to limit threshold value and change. Such mechanism makes tolerance of limitation of output electric current poorer. Need more design surplus, bring about power density poorer.

 

Blame is constant voltaic limitation

 

LM5036 ensures through marrying the Ton time of primary MOSFET stable CBC is operated. Limit threshold value through electric current of VIN adjustment peak value, reduce limitation of output electric current in order to ensure to follow the change that inputs voltage. All these functions bring foot and relevant exterior resistor setting by 3 CS. Form of computation of use LM5036 design can be calculated the value of these resistor. Positive electricity shedding and negative electric current (bring about output voltage to drop to damage even) will be felt to measure with limitation.

 

 

LM5036 parts of an apparatus developed a kind of new technology – input voltage compensation. Compensate the additional signal that the function that regards an input as voltage adds over signal through signal and slope are being measured in electric flu, can be inside limits of whole input voltage the smallest the change that spends electric current to restrict a cost, can get thereby more the output power restriction with standard essence, the biggest the threshold value that changes the ground to avoid to output power changes as what input voltage and change. In LM5036 parts of an apparatus, slope compensation signal is ISLOPE of signal of toothed electric current, in oscillator frequency (of switch frequency double) on from 0 increase 50μA (typical cost) .

 

The electric current after compensation detects signal is OK now derivation is:

 

 

Next pictures are different interior of circuit, LM5036 is received to realize signal circuit outside chasing what periodic electric current restricts for LM5036.

 

 

Right graph measures the composition of signal to explain for electric flu. Visible LM5036 detects in electric current go up to detect not only to electric current, RLIM resistor and VLIM of inner current source are received to promote the electric current that voltaic feeling measures the value outside still be being passed, thereby so that feel,put apart measures a space measure retrorse electric current and setting threshold value of retrorse electric current. Because introduce signal of input voltage VIN to feel to electric current,measure at the same time on, make feeling measure electric current to contain input voltage information. Come true to input limits in whole voltage thereby inside, voltaic threshold value maintains inside a very little scope.

 

Meanwhile, LM5036 has pulse to match a mechanism, maintain during Cycle-By-Cycle moves advocate the magnetic flux balance of transformer. Two fall on advocate of MOSFET occupy match condition than maintaining from beginning to end for nothing, in order to ensure second of transformer bend over accumulates a balance, prevent transformer saturation effectively.

 

Pulse matchs pattern following plan institute are shown. Electric current should be achieved in the 1st phase when limitation, the FLAG signal of LM5036 interior by low become tall. The RAMP signal rise in FLAG signal along by sampling, issue half switch phasicly in Gao Bian MOSFET next will maintain inside cycle collect sample originally and move normally. When high side phasic RAMP signal rises when sampling is worth above, pulse of high side PWM is shut, so final meeting makes two occupy sky comparing phasicly to match.

 

Pulse matchs a mechanism

 

The LM5036 in shedding protection too and traditional DC/DC control are identical it is to be in break away from voltage to control and enter electric current to control mode. But in voltaic mode because add inclined wave compensation, introduced input voltage thereby. Right now upper limit of traditional pilot electric current can be followed input the change of voltage and differ. But in LM5036, because electric current detects,also detect input voltage value, pass built-in control, can remove the effect that input voltage commutation brings effectively. In the meantime, in shedding protection too, if detect,electric current reached threshold value, LM5036 matchs the consistency of the enlightened time that can assure to be in charge of up and down through pulse, avoid the risk of transformer saturation thereby.

 

LM5306 can enter belch mode when shedding protection too. Its cycle can bring a foot to go up by RES outside receive capacitance to undertake configuration. Besides the tradition shed belch mode too, LM5036 returns support to flow backward protection of voltaic belch mode. Should flow backward when electric current appears repeatedly, LM5036 is accessibility also belch mode. Belch restarts capacitor handles setting 15μA current source.

 

Slant beforehand buy is started piece

 

Slant beforehand buy starts:

 

Slant beforehand in what can not accuse completely below the place situation that start, the SR of sub side closes may prematurely guide absorb electric current with outputting capacitor from what charge beforehand, deliver input end, cause the condition that now of capacitance report extrude falls so. If this process is brought about voltage has been reduced big, may bring about the new load that start to damage even share of class of power of power source converter. Can see from inside next graphs, in did not slant beforehand occurrence voltage of voltage of the output in the starting process of buy adjustment declines and too strong case.

 

Slant beforehand without what adjust completely buy is started

 

And LM5036 uses brand-new complete stabilized voltage to slant beforehand buy starts program, rise with ensuring those who output voltage is drab reach shun retrorse electricity. Here slant beforehand the buy process that start basically includes primary side MOSFET and sub side SR soft start.

 

Of primary side FET slant beforehand buy is soft start (what the picture of systematic electrify order in pursueing as follows shows) :

 

1, the rise that inputs voltage VIN to be able to accompany voltage of exterior place to load and rise, once VIN>15V and VCC/REF prep above its UV threshold value, the sub side that Fly-buck produces assists power source VAUX2 to be able to be started. Here VAUX2 besides power supply of yuan of parts of an apparatus that provides sub side beyond, make as at the same time can signal is participated in slant beforehand in the buy process that start.

 

2, exceed 1.25V when UVLO and VCC/REF prep above when its UV threshold value, SS brings the connective on the foot the soft capacitance that start begins to charge. When SS <2V, VAUX2 maintains condition ” is shut in “ . Namely TH of voltage of VAUX2> threshold value (install according to the design) , right now meeting activation makes output the restoration circuit that voltage consults VREF discharges, thereby VREF of clamp down on is worth the ground. This ensured opto-coupler produces 0 ％ to take sky comparing order. Exceed 1.25V when UVLO and when the UV threshold value with VCC and REF corresponding prep above, the soft capacitance that start begins to charge, SS brings crural voltage to begin to rise.

 

3, when SS>=2V, VAUX2 voltage value enters “ to open condition ” (VAUX2<TH, the voltage scale concern that the “ of VAUX2 shuts condition ” and “ to open condition ” is 1.4: 1) , auxiliary power source guides generation electrify is pressed.

 

4, when VAUX2<TH, VREF arrives to be released from ground be goinged to by clamp down on, output voltage begins to have the soft process that start. Occupy sky comparing to be controlled by feedback annulus road, and do not suffer SS capacitor voltage to affect (because of Vcomp<Vss) .

 

5, when VREF>Vo (beforehand bias voltage) when, vcomp begins to rise.

 

6, when Vcomp>1V (0 ％ occupy correspondence to be compared for nothing) when, of primary FET occupy sky comparing to begin to increase (Vo rises) . Meanwhile, synchronous commutate SR is soft start capacitance of the SSSR that cite a base to begin to charge.

 

 

The soft starting process of sub side SR:

 

1, before SSSR>=1V, LM5036 job is in SR SYNC mode, following graph grade the position of 3, right now SR and advocate FET maintains complete synchronism, such main effect are: 1) conduce to those who reduce SR conducting loss; 2) avoid to appear the risk of retrorse electric current.

 

2, increase gradually as primary FET and SR pulse width, right now Vo rises gradually, the output voltage that because the difference of the voltage drop between body diode and SR Rdson is caused,the kind with wide arteries and veins of this kind of step up prevents effectively is disturbed.

 

3, the rise as SSSR voltage, when SSSR>1V, what LM5036 begins cycle of SR follow on current is soft start.

 

4, SR1 and SR2 put through at the same time during follow on current.

 

5, when cycle of SR follow on current ends, be in advocate the ascendant edge of clock, SR and next power transmit cycle advocate FET condition is relevant. Continue to keep enlightened in phase, break related different. (following plan institute are shown, SR1 and HSG are belonged to debut in phase, be in 5 advocate SR1 of place of Clk ascendant edge holds liberal position, because because this maintains,SR2 is surprise appearance close position, just in time of second half cycle is contrary. )

 

6, when power transmits periodic end, advocate FET and inphase SR are shut at the same time. After the soft end that start, SR pulse will with corresponding advocate FET is complementary.

 

 

Because sub side slants beforehand buy is soft started process, can control sub side effectively to consult voltage brae rises, output SR of the activation when voltage in prep above of referenced n VREF only. Assured to won’t appear in the whole process that start so the phenomenon that SR draws energy of output electric capacity, also won’t appear naturally the circumstance that capacitance voltage declines. Following plan institute are shown, be in whole soft in opening a process, output voltage keeps drab and smooth rise, can ensure circuit of the number inside the system begins the work with right order effectively.

 

 

Be based on the design of LM5036

 

Ask an attention, when the design takes the DC/DC converter of LM5036, the user need not consider this kind to slant beforehand buy starts a process, because this is LM5036 itself,be over complete pilot function.

 

Auxiliary power source piece

 

Compositive and auxiliary source:

 

When auxiliary power source is being received outside be being done not have to be in half bridge driver, the system needs to slant alone buy power source and more component. Cannot adjust easily bias voltage comes to sub side control system is flexible the process that start. Because need here alone outside receive power source and more component, can take up finally greatly board class area.

 

 

And LM5036 oneself is compositive have constant to guide surely a time control mode (the Fly-buck controller of COT) control mode, can use LM5036 and primary side and power supply of sub side parts of an apparatus. And the Ron that can pass Pin-6 will undertake the time length of the ON Time in the COT control mode here installing. RFB1 and RFB2 are received to be able to install VAUX1 outside needing only, the voltage of VAUX2 is worth. A small auxiliary source transformer is received outside needing only, can realize power supply of VCC of LM5036 primary side, sub side keeps apart drive power supply, carry of segregation smooth Ou puts the power supply that wait (the power supply source that institute of as above plan shows departmental branch) . VAUX2 was participated in at the same time slant beforehand buy starts a process, communicate primary side and sub side as make can signal, pass and of discharge restoration circuit cooperate to come true to slant beforehand the sequential control that buy starts. Can see VAUX2 finished the communication of primary side and sub side here, and avoid to use additional segregation signal circuit. Reduce BOM amount to increase power density thereby secondhand. In addition, to assisting the design of transformer, can pass a simple tool completely to design computational form to realize the design of transformer and relevant parts of an apparatus. Application is simple, save board class area and integrated cost greatly. Following plan institute are shown, need only adscititious a small auxiliary transformer (maize part) can realize these functions easily, increase systematic power density greatly.

 

 

Institute of as above plan is shown, SW_AUX is the output end of Fly-buck, l3 is the output side inductance of Buck circuit, c36 is output side capacitance, r22 and R23 approach resistance for feedback cent, r24, c34 and C35 make the ripple infuse circuit of Type-3. When use computation tool, input the basic message of a few auxiliary power source above all, frequency, load current value, inductance takes a cost. Can calculate a corresponding capacitance type selecting.

To FB resistor, can according to Flybuck before the voltage of the class after class is reached will calculate a corresponding FB resistor, if place of form of Auxiliary Feedback Circuit is shown.

 

 

As to the parameter choice of circuit of RCC ripple infuse, there are 3 kinds of different circuit choices in computational form, after choosing TYPE-3, can input the ripple voltage value of the target and value of ripple electric current, can calculate a value of corresponding RCC block look. Here secures the value of Cac and Rr commonly, can undertake corresponding type selecting according to computational value as to Cr.

 

 

Plan institute is shown on is the layout regulation that is based on the reference of LM5036 to judge appraise board, on half part is circuit of input filter wave, half bridge circuit, output circuit of side synchronism commutate and output filter wave. Below half part is parts of an apparatus of LM5036 circumjacent key, circuit of auxiliary power source and feedback loop adjust circuit, assist what power source uses minimum to occupy board the effect that the area achieves with one action to be gotten more however. The common 200W brick power source in industry uses the territory of 1/8 brick normally. As a result of LM5036 tall compositive degree, 200W power power supply is already OK now can come true on 1/16 brick module, same power can accomplish smaller domain area to go up.