Tuesday
Aug102010

One World, One Power Supply? Universal AC input voltage.

Yes!

PowerPhysics' switch-mode power supplies feature automatic input voltage selection. This circuit adjusts the power supply to accept an AC line voltage anywhere in the range from 88 to 275 Volts.

And better yet, the user doesn't have to do anything. Just plug in the power supply and it does the rest.

Tuesday
Aug102010

What is Power Factor Correction (PFC)?

PFC is required by the European Union CE mark for amplifiers greater than 600 Watts*. It makes sure the power supply does not create cycling currents in the AC power grid.

The PFC circuit is in the input stage of the power supply. It aligns the phase between the AC voltage and current to use all of the available circuit breaker current for amplifier power. With PFC you can run more amplifiers from a given circuit breaker.

With PFC the power supply becomes a resistive load which does not force the AC wiring in the house or building to carry cycling or "imaginary" currents. These currents are labeled imaginary by engineers because they never generate power for the speaker. However, they do cycle through the building's AC circuit breaker so a small non-PFC amplifier can trip a large breaker.

 

* The actual specification is for harmonic content and you have to calculate the amplifier power.

Tuesday
Aug102010

Why are Class-D amplifiers so efficient?

Class-D amplifiers transfer power directly to the load. The output switches (MOSFETs) are either ON or OFF. 

In the ON state the switch is saturated or "shorted". It can pass lots of current with very little loss because there is only a small voltage across the switch.

Power = Voltage x Current. If Voltage or Current are zero then the power (in this case power lost to heat) is also zero.

In the OFF condition the switch is an open circuit and there is zero current flowing through the switch.

In a linear (Class A, A/B or B) amplifier the output devices have both voltage and current across them at the same time. This creates large losses and the requirement for low bus voltages and/or massive heat sinks.

Monday
Aug092010

What is special about One-Cycle Sound?

One-Cycle SoundTM is the fastest reacting PWM control law. It compares the audio input directly to the PWM waveform using non-linear feedback. This creates high-fidelity, transparent audio amplification. 

A typical PowerPhysics One-Cycle SoundTlM amplifier has 300,000 switching cycles per second. OCSTM makes 2 corrections per cycle or 600,000 corrections per second! 

One-Cycle SoundTM corrects:
  • Audio signal changes
  • Power supply noise and ripple
  • Amplifier power stage (MOSFET) errors
  • PWM rise and dead time errors

And it happens every 1.7 micro seconds. 

No other amplifier works as fast to deliver high quality audio.

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