Reply to thread

Message: <blockquote data-quote="Buck" data-source="post: 8762795" data-attributes="member: 591582">I'm trying to understand the differences between half-bridge and full-bridge amps."Energy Flow  – In linear amplifiers the energy flow is always from supply to the load, and in Full bridge Class D amplifiers this is also true. A half-bridge Class D amplifier however is different, as the energy flow can be bi-directional, which leads to the “Bus pumping” phenomena, which causes the bus capacitors to be charged up by the energy flow from the load back to the supply. This occurs mainly at the low audio frequencies i.e. below 100Hz.""Similar to conventional Class AB amplifiers, Class D amplifiers can be categorized into two topologies, half-bridge and full-bridge configurations. Each topology has pros and cons. In brief, a half-bridge is potentially simpler, while a full-bridge is better in audio performance. The full-bridge topology requires two half-bridge amplifiers, and thus, more components. However, the differential output structure of the bridge topology inherently can cancel even the order of harmonic distortion components and DC offsets, as in Class AB amplifiers. A fullbridge topology allows of the use of a better PWM modulation scheme, such as the three level PWM which essentially has fewer errors due to quantization.In the half-bridge topology, the power supply might suffer from the energy being pumped back from the amplifier, resulting in severe bus voltage fluctuations when the amplifier outputs low frequency audio signals to the load. This kickback energy to the power supply is a fundamental characteristic of Class D amplification. Complementary switching legs in the full-bridge tend to consume energy from the other side of the leg, so there is no energy being pumped back towards the power supply. <a href="https://m.eet.com/media/1063439/IRTable1Large.JPG" target="_blank"> Table 1</a> shows the summary of the comparison."[URL unfurl="true"]https://www.eetimes.com/how-class-d-audio-amplifiers-work/[/URL]"Class D Amplifier Terminology, and Differential vs. Single-Ended VersionsFigure 3 shows a differential implementation of the output transistors and LC filter in a Class D amplifier. This H-bridge has two half-bridge switching circuits that supply pulses of opposite polarity to the filter, which comprises two inductors, two capacitors, and the speaker. Each half-bridge contains two output transistors—a high-side transistor (MH) connected to the positive power supply, and a low-side transistor (ML) connected to the negative supply. The diagrams here show high-side pMOS transistors. High-side nMOS transistors are often used to reduce size and capacitance, but special gate-drive techniques are required to control them (Further Reading 1).Full H-bridge circuits generally run from a single supply (VDD), with ground used for the negative supply terminal (VSS). For a given VDD and VSS, the differential nature of the bridge means that it can deliver twice the output signal and four times the output power of single-ended implementations. Half-bridge circuits can be powered from bipolar power supplies or a single supply, but the single-supply version imposes a potentially harmful dc bias voltage, VDD/2, across the speaker, unless a blocking capacitor is added.The power supply voltage buses of half-bridge circuits can be “pumped” beyond their nominal values by large inductor currents from the LC filter. The dV/dt of the pumping transient can be limited by adding large decoupling capacitors between VDD and VSS. Full-bridge circuits do not suffer from bus pumping, because inductor current flowing into one of the half-bridges flows out of the other one, creating a local current loop that minimally disturbs the power supplies."[URL unfurl="true"]https://www.analog.com/en/analog-dialogue/articles/class-d-audio-amplifiers.html[/URL]I think what could be going on, possibly, is that a half-bridge amp allows energy flow from changes of voltage from inside of the amp into your 12v power wires.  It almost seems like a half-bridge amp makes your car's 12v electrical system part of the amplifier system.  Full-bridge amps seems to only draw current from the 12v system, where it seems like a half-bridge amp can pulsate both + and - into your vehicle's 12v system.  Half-bridge seems like your vehicle's batteries and everything now determine electrical factors for how the power from them interacts with your amp feeding power back into the 12v system.  I think high charge/discharge capacitors or something like the lithium banks would really help dampen the the amp pulsations.  They would possibly like a giant 12v + and - dampener for your entire system.I know some people with very large systems, with lithium ion banks, super caps, and they all run what seem to be half bridge amps. The loudest people that I actually know run a lot of extra electrical components in between the alternator 12v and the subwoofer amp.  All of that extra equipment seems to act as a dampening system for both the alts and the amplifiers, which would theorectically translate to your subwoofers moving exactly like they're supposed to be at all frequencies.  I could be a massive noob; I'm not sure.Like, is the the Sundown Salt 8k a half-bridge amp (8000w)?:   <a href="https://sundownaudio.com/lv/sa/amplifiers/salt-series/salt-8/" target="_blank">https://sundownaudio.com/lv/sa/amplifiers/salt-series/salt-8/</a>Here's the Sundown SFB 8000, labeled as a full bridge (8000w):  <a href="https://sundownaudio.com/lv/sa/amplifiers/sfb-series/sfb-8000d/" target="_blank">https://sundownaudio.com/lv/sa/amplifiers/sfb-series/sfb-8000d/</a>The Salt 8 is literally about twice the size of the SFB 8000.  That has to make the Salt sound much better.  It seems like the not-full bridge car audio amps tend to have better musical performance over the full-bridge amps.  It also seems like a lot of full-bridge amps have a lower dampening factor than the half-bridge.  I can't find the dampening factor on some of the full-bridges.  The Salt 8 has a dampening factor of 400<.  That's pretty high, from what I've seen.  The dampening factor seems to really play a role in the amplifier controlling the woofer across a relatively wide bandwidth of notes, for something like a ported box. I would really consider these things when you're setting up your audio system.I think box design + overall quality of amplified signal into subs are wayyyyyyy more important than the type of sub you have.</blockquote>

Verification

Top

What's new

Forum list