DocumentCode :
821321
Title :
A Class B switch-mode assisted linear amplifier
Author :
Walker, Geoffrey R.
Author_Institution :
Sch. of Inf. Technol. & Electr. Eng., Univ. of Queensland, Brisbane, Australia
Volume :
18
Issue :
6
fYear :
2003
Firstpage :
1278
Lastpage :
1285
Abstract :
A switch-mode assisted linear amplifier (SMALA) combining a linear (Class B) and a switch-mode (Class D) amplifier is presented. The usual single hysteretic controlled half-bridge current dumping stage is replaced by two parallel buck converter stages, in a parallel voltage controlled topology. These operate independently: one buck converter sources current to assist the upper Class B output device, and a complementary converter sinks current to assist the lower device. This topology lends itself to a novel control approach of a dead-band at low power levels where neither class D amplifier assists, allowing the class B amplifier to supply the load without interference, ensuring high fidelity. A 20 W implementation demonstrates 85% efficiency, with distortion below 0.08% measured across the full audio bandwidth at 15 W. The class D amplifier begins assisting at 2 W, and below this value, the distortion was below 0.03%. Complete circuitry is given, showing the simplicity of the additional class D amplifier and its corresponding control circuitry.
Keywords :
amplifiers; bridge circuits; power convertors; switching circuits; voltage control; Class B switch-mode assisted linear amplifier; Class D amplifier; audio bandwidth; dead-band; distortion; efficiency; high fidelity; hysteretic controlled half-bridge current dumping stage; linear amplifier; low power levels; parallel buck converter stages; parallel voltage controlled topology; switch-mode amplifier; Bandwidth; Buck converters; Circuit topology; Electric variables control; High power amplifiers; Hysteresis; Impedance; Low-noise amplifiers; Power amplifiers; Voltage control;
fLanguage :
English
Journal_Title :
Power Electronics, IEEE Transactions on
Publisher :
ieee
ISSN :
0885-8993
Type :
jour
DOI :
10.1109/TPEL.2003.818825
Filename :
1243684
Link To Document :
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