[introduction]In the application of power source converter that seeks tall changeover efficiency, the converter of LLC syntonic power source that uses LLC resonance (Resonant Power Converter) circuit framework is behaved because of its exceedingly good efficiency, in become quite popular in recent years. Be in for converter of power source of farther promotional LLC the work efficiency when burden, synchronous commutate also was used in succession in devising example (Synchronous Rectification, SR) the power loss that will decrease to export side commutate component as transformer with diode originally. In addition, be aimed at what carry efficiency gently is promotional, have do not change at operating the pulse frequency with state idiomatic institute to move normally (Pulse Frequency Modulation, PFM) , a lot of special controller also were offerred record control pattern gently (Light-load Mode) will reduce switch loss.

In the application of power source converter that seeks tall changeover efficiency, the converter of LLC syntonic power source that uses LLC resonance (Resonant Power Converter) circuit framework is behaved because of its exceedingly good efficiency, in become quite popular in recent years. Be in for converter of power source of farther promotional LLC the work efficiency when burden, synchronous commutate also was used in succession in devising example (Synchronous Rectification, SR) the power loss that will decrease to export side commutate component as transformer with diode originally. In addition, be aimed at what carry efficiency gently is promotional, have do not change at operating the pulse frequency with state idiomatic institute to move normally (Pulse Frequency Modulation, PFM) , a lot of special controller also were offerred record control pattern gently (Light-load Mode) will reduce switch loss.

LLC synchronous commutate applies circuit and working principle

NCP4318 is the synchronous commutate controller that applies to LLC framework, if pursue,its use circuit 1 is shown, and if pursue,its job principle is summarized 2. NCP4318 passes through VD and VS foot will detect the draw water of SR power switch extremely (Drain, d) with the source extremely (Source, s) the voltage between (VDS) , decide its VG foot with this drive signal condition. Of drive signal spark cent is LOW or HIGH for DLY_EN flag two kinds of states. Usually, when VD and VS foot the voltage between allows under VTH-ON when, it is VG output HIGH instantly. But when DLY_EN flag is HIGH, VD and VS foot voltage allows a defer time that should keep a paragraph of TON-DLY2 under VTH-ON, VG just can be outputted for HIGH. When VG output is HIGH, through diagnose VD and VTH-OFF of VS voltage prep above to allow, NCP4318 can close VG signal. This VTH-OFF is a fluctuant value in the design of NCP4318. By means of adjusts VTH-OFF, NCP4318 can ensure close VD voltage to rise from VG the time that amounts to VTH-HGH is wrong, time of i.e. dead band (Dead Time) , keep changeless below the state of different load.

Graph 1 NCP4318 uses circuit figure basically

Principle of main action of graph 2 NCP4318

Record control pattern gently

The LLC that a lot of manufacturer roll out controlled special IC to be offerred record control pattern gently. Although its touch hair condition and operation detail to have difference each, but the principle of applicable to both or all is the brake side extremely a package that signal control passes a design for (Packet, Pattern, Package) , readjust seals the distance between Bao Zhi, change in order to achieve the air of power. These seal a bag to have shorter front normally brake pole pulse (Gate Pulse) , use the syntonic pitch LLC (Resonant Tank) store can condition is operated can convey the condition of energy, next the brake of reuse follow-up extremely pulse delivers energy side. With the NCP13992 of Onsemi the department is labelled exemple, if pursue 3 are shown, the brake of side extremely signal is arranged according to the order of Q2 of → of Q2 → Q1, and there are all a paragraph of dam up waters between Bao Zhi extremely signal all is low accurate silent (Dormant) time. By means of records control pattern gently, LLC circuit can avoid to be operated to be in when carrying gently taller switch frequency (Switching Frequency) , reduce switch loss thereby (Switching Loss) .

Of graph 3 NCP13992/NCP13994 record operation pattern gently

Compatibility challenge

Operate mode to carry gently when side operation, the electric current of 2 side is undee meeting and normally pulse frequency air becomes quite different. Above all, as a result of side guide connect time to be able to have accident change, because 2 times this the electric current of side guides,connect time to also can change somewhat. In addition, not be of each one second side brake pole pulse can be in 2 times side generation guides electrify flows. Actually, inspect the design sealing a bag that differs to record operation pattern gently, 2 times the electric current of side guides the condition that know kind also can differ somewhat. Have some of one second side brake pole pulse can not let side 2 times appear piece guide electrify flows, and some can guide only part-time. It is even inside silent time, electric conductance knows resonance antrum the rest diode of noumenon of side power switch (Body Diode) when, 2 times side also can have brief electric conductance to connect sometimes.

When 2 times side guides electrify flows, the noumenon diode that can allow SR power switch above all guides. Right now, what SR controller can diagnose VD and VS voltage is low accurate, send a VG pulse then. However, in recording operation pattern gently, 2 times the electric current of side is met ignore big ignore small, grow suddenly ignore short, have suddenly do not have suddenly, this brings more challenge to SR controller.

Parameter adjusts strategy

Fortunately, NCP4318 has adjustable parameter, can come through the partial parameter that adjusts its to allow to adjust promotional its and the compatibility that record operation pattern gently. Describe what its part to adjust direction with next listing that more relevant parameter reachs:

One, shorten TON-DLY2

The TON-DLY2 of NCP4318 is designed, investigate its former by, it is for the operation at under syntonic frequency mode (Below Resonance) converter of LLC power source, the conductance of 2 side report when carrying gently understands the mechanism that characteristic place devises. Should be in only spark the negative electric current of NCP4318 is diagnosed (SRCINV) , or it is pulse jumps frequency mode (Skip Mode) when, side amounts to enough length without the time of pulse (TGRN2-ENT) , DLY_EN flag can turn namely voice is HIGH. And it is very easy in all sorts of instantaneous processes that carry gently that negative electric current is diagnosed spark. For example, burden jumps to carry gently, or it is the pulse when carrying gently jumps the process of pass in and out of frequency mode, narrow very easily in 2 side electric current and shorten its guide in the switch cycle that tells time, spark negative electric current is diagnosed. Accordingly, in carry a state gently to fall, the DLY_EN flag of NCP4318 is HIGH normally.

Graph 4 under syntonic frequency mode hold character of model of side electric current gently 2 times

Carry the controller that operates mode gently to having, the switch that can let should guide electrify flows normally on the design extremely pulse can guide an electric current that comparative, and the wave of every pulse is broad also the tendency is inferior to growing in that way under syntonic frequency mode, however more be bordering on mode of frequency of prep above resonance (Above Resonance) undee. Accordingly, if pursue 4 need to comparative in that way the state of length TON-DLY2 normally not common operate mode at carrying gently. Be based on the consideration of the utilization rate of switch of promotional SR power, the proposal gets TON-DLY2 parameter set shorter. The TON-DLY2 of NCP4318 is the shortest can set arrives 240 Ns.

2, contractible KTON1/2, TINV

Because if pursue,be accompanied easily in the process of switch 5 shown noise, these noise may make VDS crosses VTH-OFF high. Accordingly, NCP4318 was designed the shortest guide a time (TON-MIN) will prevent VG pulse to be closed by premature ground. Of NCP4318 the shortest guide the design is a time the synchronous whole conductance that cycle of a switch measures tells time (SRCOND[n-1] ) a fixed scale. This scale depends on condition of DLY_EN banner target, can be KTON1 or KTON2, if pursue 2 are shown. In the shortest guide a time inside, VTH-OFF can be disabled to change, but VG still can pass through protective mechanism (for example SRCINV) will close. However, through protection the mechanism closes VG, always need to satisfy time of a paragraph of defer more (Delay Time) , this meeting makes pass time a bit a few later. The defer time of SRCINV is TINV. If SR brake extremely signal guides because of its switch the electric current that connect by turning to lose and need to be closed, wait for period of time more, also make negative electric current much accumulate a bit time, switch of synchronous commutate power will be caused to go up when closing bigger voltage stress.

Because carry the electric conductance that operates mode gently to tell time,can grow suddenly ignore short, to avoid among them by long when shortening, guide shortly connect time to fall into TON-MIN in, you can get the KTON1 of NCP4318 and KTON2 set a bit shorter. The set of the shortest parameter that NCP4318 place provides is KTON1=34% , KTON2=17% .

Additional, if the short arteries and veins of side is wide,can adjust, also suggest to adjust it a few longlier than KTON2. If the short arteries and veins of side is wide,cannot spin a little, hard to avoid or meeting need involve the state of VG through SRCINV. Accordingly, you can get the defer time set of SRCINV a bit shorter. But, should notice not so short that let be like a graph The noise of 5 sparked SRCINV. The TINV of NCP4318 but set limits is 170 ~ 620 Ns.

Graph 5 VG guides the VDS noise when connecting

3, shorten TOFF-MIN

Just closed in pulse of a brake pole normally when, guide to prevented to be affected by noise and be touched by accident the act that open, we can add on one paragraph after closing the shortest pass time (TOFF-MIN) , in order to ensure of brake pole signal close condition to be maintained at least so period of time. In the graph 3 in mention, recording operation pattern gently is to be being sealed normally silent time is inserted to adjust energy to deliver between Bao Zhi. Seal the first pulse in the bag and the last pulse to fall in normally same a brake pole signal on, pursue for example The example of 3 is in Q2. Successive two Q2 pulse, if silent time is shorter, same a SR power switch is likely need is closing before long hind debut instantly again. Accordingly, you can be the TOFF-MIN set of NCP4318 shorter option. For example, low frequency version (NCP4318xLx) TOFF-MIN parameter is S of 2 μ , you can choose 700 Ns additionally; And high frequency version (NCP4318xHx) TOFF-MIN parameter is S of 1 μ , you can be chosen additionally for 500 Ns.

Graph 6 TOFF-MIN makes VG cannot debut in real time

The place on put together is narrated, collocation records operation pattern gently, the NCP4318 parameter of the proposal chooses to be mixed for short TON-DLY2, small KTON, short TINV short TOFF-MIN. When article compose, all parameter that still mention above place without the NCP4318 of onefold version adjust acme. According to the norms manual of the NCP4318 when article compose, at present the TON-DLY2 of all version is the shortest set. The version that has lesser KTON has NCP4318ALGP. As to TINV, the version of the shortest set includes to have NCP4318AHD, NCP4318ALGP. And TOFF-MIN set includes NCP4318ALS for the version of shorter value.

The parameter of NCP4318 adjusts pattern is the programmed control after enclosing (In-package Programming) . Current product policy is avery kind of different set make it can order spare parts number individually (Orderable Part Number, OPN) . If you have a guest to make the demand of parameter set, can contact with Onsemi business delegate of place or product agent.

Express what 1 NCP4318 composes instantly in the article to be able to order version list

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