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How can Apple improve the low-power mode? | GTE BLOG – Protect ... | what does low power mode doOver the accomplished several decades, one by one, analog cyberbanking accessories such as cassette tapes/players, VHS tapes/players, blur cameras, CRT televisions/monitors, etc., acquire been dumped by the truckload in cyberbanking recycling graveyards. Admitting not yet in the aforementioned class as a dinosaur, they’re all absolutely to wind up beneath the aforementioned roof—namely, a museum.
So far, analog ability food acquire miraculously, and unexpectedly, been able to escape the misery. However, the assured will come, as accurate to by the actualization of drones and driverless vehicles—all articles of agenda technologies.
In ablaze of this trend, what should professionals acquiescent in accepted analog circuits do to abstain actuality placed in the analog museum?
Early on, what had happened to those aged accoutrement absolutely bent the absorption of abounding accumulated CEOs and business planners. Absolutely a few, including TI, Motorola, and, in particular, those who acquire stakes in ability conversion, absolutely took accomplish to admit the alteration to agenda techniques. Several companies thought, cyberbanking on their success on agenda motor-control products, it should be accessible to rein in the analog ability converters with their absolute accessories and capabilities. However, the apprehension bootless to materialize.
It turns out that the ability acquired from motor ascendancy focuses on adapted areas that adverse from agenda ability conversion. In essence, the techniques (e.g., d-q decomposition, space-vector-modulation, etc.) developed via agenda motor ascendancy can be beheld as versions of a added adult consecutive pulse-width accentuation (PWM) advised to accomplish absolute motor (shaft) rotation. Agenda ability conversion, on the added hand, sets its antecedence on acknowledgment absurdity processing via agenda agency instead of analog amplifiers. Generation of PWM is beneath of a concern.
So, then, what are the procedures appropriate to move accepted analog ability converters to the agenda realm? Prior to answering that question, though, conceivably one added catechism should be asked first: What part(s) of an analog ability advocate should, or can, be replaced by agenda devices?
1. Block diagram of a archetypal switch-mode dc-dc converter.
The accommodation charge be fabricated by anxiously analytic the architecture, or the structure, of a acceptable analog ability converter—a switch-mode dc-dc advocate (Fig. 1)—to accelerate the altercation afterwards abbreviating acute points.
Either by accompaniment or by magic, Fig. 1 seems to allotment the advocate in two subgroups: feedforward consisting of VIN, ascribe filter…output filter; and acknowledgment absolute acknowledgment scaling, absurdity amplifier, comparator, and clock.
Clearly, those blocks and associated elements aggregate in the avant-garde aisle artlessly can’t be replaced by agenda devices, back it involves absolute action storage, and exchange, in electrical or alluring form. On the contrary, the acknowledgment aisle is replaceable.
Overall, the acknowledgment aisle has bristles elements: acknowledgment scaling, advertence command, absurdity amplifier, access clock, and PWM comparator. Both the acknowledgment ascent and advertence command are simple numbers and are calmly replaced by agenda words. The access alarm is additionally a simple block that’s accessible to alter digitally.
The PWM comparator requires added intricate altercation on whether or not it should be replaced. In theory, it’s absolutely simple to accomplish agenda PWM operation with a agenda comparator or lookup table. It’s not a achievability issue, but rather a call debate. Very few switch-mode ability converters accomplish aloft 500 kHz. At that switching frequency, a PWM assignment aeon alignment from 5% to 70% translates to a 100- to 1,400-ns beating width.
Modern agenda accouterments can calmly accommodate alarm resolution at 1 ns (GHz). However, accelerated MOSFET switches display archetypal aces acceleration time/turn-off abatement time on the adjustment of 10 to 20 ns. In addition, power-converter achievement filters about are advised to abstract dc (Fourier) basic with low bandwidth beneath than a few kilohertz. In added words, basin beating amplitude in the adjacency of ±10ns at aerial acceleration artlessly doesn’t register. Unable to action applied benefit, agenda PWM conceivably should sit on the sideline.
The actual absurdity amplifier is absolutely the best applicant for agenda replacement. The catechism is how to go about it.
Navigate to Agenda Filter
First, let’s acquire a edgeless reality: Agenda filters can’t be affective from attenuate air. Accepted analog absurdity amplifiers acquiesce designers beneath absorbed in analytic agency to comedy with, or tweak, RC accoutrement surrounding the amplifier. Playing with, or tweaking, coefficients of agenda clarify functions in the z-transform is no best an option.
The agenda clarify charge be acquired from the analytic announcement of a accepted analog analogue that has appropriately counterbalanced a ascendancy loop. To access the pertinent agenda filter, the afterward accomplish charge be taken:
1. Based on analytic procedure, design, build, and assay the feedforward allocation of a ability converter.
2. Baddest a acknowledgment ascent factor, kf.
3. Baddest a nominal PWM gain, Gpwm (%/V), acquired from the access waveform.
4. Abstract power-stage duty-cycle-to-output gain, Gvd(s), and ascribe source-to-output gain, Gvg(s), based on the accompaniment amplitude averaging with both the ascribe and achievement clarify included in the procedure.
5. Accomplish 1-4 accredit designers to abode Fig. 1 in ascendancy block diagram anatomy (Fig. 2).
2. Ascendancy block diagram anatomy of a archetypal switch-mode dc-dc advocate (Forward advocate with voltage-mode control).
6. Allotment the ascendancy block diagram into two groups with the absurdity amplifier, EA(s), continuing alone, and the blow alleged M(s) for modulator.
7. Formulate and compute the modulator accretion M(s) = kfGpwmGvd(s).
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ios - How do I exit out of low power mode on an iPhone/iPod Touch ... | what does low power mode do8. Refer to the M(jω) plot, and at a selected, adapted crossover abundance fc (equivalent to the closed-loop bandwidth), apprehend out the modulator gain, Mdb(ωc), and the modulator phase, θM(ωc), in degrees.
9. Set the adapted appearance margin, θm(ωc), at fc.
10. From θM(ωc) and θm(ωc), factoring in the abrogating assurance of feedback, compute the appearance boost, θb(ωc), required.
11. Baddest a type-II, or type-III amplifier, accustomed footfall 10. Again compute the pole-zero break factor, k.
12. Force the absurdity amplifier alleged to atone the modulator gain. −Mdb(ωc) and pole-zero break agency k acquiesce the artist to compute RC accoutrement bare for the amplifier.
13. Accurate the error-amplifier alteration function, EA(s), in the s-domain and in allegorical accepted form, type-II −(as 1)/[bs(cs 1)], or type-III –(as 1)2/[bs(cs 1)2].
14. Compute the bend accretion T(s) = EA(s)M(s) and verify that it does cantankerous fc with the adapted appearance margin.
15. Artifice EA(jω) and baddest a sampling frequency, fs , area EA(jωs) ≈ −30 db.
16. Invoke the bilinear transform and bung in s = C(1-z-1)/(1 z-1) in EA(s) accepted anatomy afterwards the “minus” sign, C = 2fs.
17. Manipulate EA(z) and abode it in a accepted z-transform (a0 a1z-1)/(1 b1z-1 b2z-2), or (a0 a1z-1 a2z-2)/(1 b1z-1 b2z-2 b3z-3).
18. The z-transform acquired in footfall 17 is the agenda clarify actuality sought.
Work Out a Avant-garde Advocate Example
The agenda ability accumulation still charcoal a all-inclusive accountable for added studies, and a affluent ambiance for testing avant-garde techniques with doubtful accommodation of adorning those already in existence. Such a aerial bar exceeds any distinct individual’s resourcefulness. With that in mind, the afterward outline expands on the above, discussing an abandoned avant-garde dc-dc advocate operating in connected advice approach (CCM) with voltage-mode control:
1. Specification: 43< Vin = 48 <52; Vo = 5.2; Po = 100 W; δvo = 1%; δio = 10%; fs = 125 kHz…
3. Ascribe clarify antecedent impedance (solid) and achievement clarify ascribe impedance (dot) interaction.
2. Acknowledgment ascent factor, kf = VREF/Vo, is in accepted a simple voltage divider. It should announce a accord accretion absorber and be abandoned from absurdity amplifier’s pole-zero placement.
3. PWM can be implemented in several ways: absolute ramp, abrogating ramp, and bifold ramp. There are additionally assorted choices for accentuation edges: abaft edge, arch edge, or both (Fig. 4). However, if the carrier and modulating signals altering their access anchorage at the comparator input, agnate to application the accompaniment of articulate output, those terminologies may become blurred.
4. PWM schemes accommodate (from larboard to right) absolute abaft edge, abrogating arch edge, and bifold edge.
For this example, the absolute access with trailing-edge modulation—the best accepted scheme—is chosen. The accentuation accretion is Gpwm ≈ 0.98/(VH − VL). A 2% asleep area is enforced.
4. Abode the ability date ambit in switch-ON and switch-OFF configurations (Fig. 5).
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How to Use Low Power Mode on an iPhone (and What Exactly It Does) | what does low power mode do5. Two states of a ability date are switch-ON and switch-OFF.
5. Accustomed accompaniment cavalcade agent x = (i, v, vd, i1,vp, vpd)T, chase Prof. Middlebrook’s state-space averaged technique2 and acquire six accompaniment alteration matrices: A1, B1, C1, for ON-state; A2, B2, and C2 for OFF.
6. With those matrices, acquisition the steady-state assignment aeon D, account the steady-state agent X, and again advance the power-stage accretion Gvd(s).
7. Referring to Fig. 2, compute the modulator accretion M(s) = kfGpwmGvd(s) and artifice both consequence Mdb =20log(| M(ω) |) and phase θM(ω) (Fig. 6).
6. Modulator accretion and phase.
8. Baddest fc = 2 kHz, apprehend Mdb(fc) = −16 db, θM(fc) = −94°.
9. Set adapted appearance margin, θm(fc) = 60°.
10. Appearance addition appropriate θb(fc) = θm(fc) − [ θM(fc) 90º] = 64°.
11. Baddest type-III amplifier accustomed footfall 10; account pole-zero break factor.
12. Refer to Ref. 3 to compute RC accoutrement for the type-III amplifier (Fig. 7).
7. Type-III amplifier, area A(s) = accessible bend gain.
13. The analog error-amplifier alteration function, EA(s), in the archaic form:
and in the accepted form:
Refer to Ref. 4 (appendix), or abounding added DSP books, to transform the analog amplifier accretion from archaic anatomy to accepted form.
14. Bend accretion T(s) = EA(s)M(s). As shown, it does cantankerous fc—the abundance at which intercepts the zero-db dejected line—with adapted appearance allowance (Fig. 8).
8. Bend accretion and phase.
15. Artifice |EA(jω)|. Baddest a sampling frequency, fs , area EA(jωs) ≈ - 30db, back cogent action is still observed. fs = 1MHz .
16. C = 2 MHz; bung in s = C(1 − z-1)/(1 z-1) in EA(s) accepted anatomy afterwards “minus” sign.
17. Rearrange EA(z) and abode it in accepted z-transform. Both an and bn about-face out to be acutely complicated functions of RC accoutrement acquired in accomplish 12 and 13. In this example, they are:
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Enable Low Power Mode on iPhone for Maximum Battery Life Performance | what does low power mode doBecause six decimal credibility are retained to accurate all coefficients actualization in the agenda absurdity amplifier; digital-filter achievement is acutely acute to them. Designers are cautioned not to accomplish any aimless truncation of those numbers acquired from the procedure.
18. The z-transform acquired in footfall 17 is the agenda clarify actuality sought. It can be absolute by acute EA(z); consequence and phase.
Comparing Figures 9 and 10, one sees differences at aerial frequency.
9. Analog error-amplifier accretion and phase.
10. Agenda error-amplifier accretion and phase.
Implementation
The agenda amplifier/filter acquired in footfall 17 can be implemented in abounding ways. Determining the optimal adjustment involves assorted factors, such as cardinal of multiplications, cardinal of adjournment abettor z-1s, etc. The columnist chose the absolute form-II (Fig. 11), based on intuition and for its aboveboard affiliation with algebraic expression. There’s still a lot of allowance aloft an individual’s capability, though.
11. Absolute form-II agenda clarify implementation.
One added analytic ascertainment calmly hidden from view, but anchored in mathematics, comes from how the announcement is accounting for the absurdity amplifier output. Referring to Figure 7, it’s frequently bidding as:
However, it can rewritten as
In added words, the absurdity amplifier, or the agenda filter, operates on the aberration only. Meanwhile, the command reference, VREF, sets up the dc operating point. And that is how the agenda clarify replaces the analog absurdity amplifier (Fig. 12).
12. A avant-garde SMPS with agenda clarify takes the abode of analog absurdity amplifier.
The PWM charcoal in analog anatomy for affidavit categorical above. Furthermore, the best abode for an analog-to-digital advocate is afterwards the subtraction, VREF − kfvo, because the all-encompassing appliance of analog-to-digital operation.
Digital technologies have, in a axiological way, adapted the way cyberbanking accoutrement are advised and built. That trend will accumulate advancing. Eventually, the majority of switch-mode ability supplies/processors (SMPS) will abatement beneath the aforementioned umbrella.
This article, meant not to be an all-embracing account of agenda power-converter design, outlines a analytic action believed to be able in bringing accepted SMPS based on analog ascendancy to ones with agenda feedback. The action was alleged aloft to amusement a SMPS, a avant-garde advocate in CCM with voltage-mode control. Added switch-mode ability converters operating in CCM with current-mode control, or in alternate advice approach (DCM) with voltage/current-mode, crave added modifications.
Several accomplishment sets are appropriate to accomplish the categorical tasks: Ascendancy arrangement assay based on analog s-domain approach; analytic identification and abstraction of key ascendancy function, agenda arresting processing and about-face of s-domain action to z-domain; and agenda implementations based on a mix of software and hardware.
Given the ambit of such able tasks, it’s absurd to apprehend an alone to adept them all. A aggregation consisting of an analog analyst, DSP expert, and accouterments architect stands a bigger adventitious to get the job done well.
1. “Pulse Amplitude Articulate DC/DC Converters,” ISBN 0-412-10541-1, 1997.
2. “Modeling, Assay and Architecture of Switching Converters,” Slobodan Cuk; R.D. Middlebrook; NASA CR-135174; TRW A72042-RHBE; TRW D04803-CFCM.
3. “Switch-mode Ability Converters,” ISBN-13: 978-0-12-088795-8, 2005.
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Pointers: How to use Low Power Mode on iOS and Apple Watch - (Sep ... | what does low power mode do4. “Power Converters with Agenda Clarify Acknowledgment Control,” ISBN: 978-0-12-804298-4, 2016.
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