Tracking
or envelope Power Supply Amplifier
If we reconnect the
"H"
topology to a Buck converter and tracking the input signal in
proportion with the VCC amplitude via Boosting
voltage that can made with a Buck converter or any other
Switching Power Supply topology.
This
technique uses one variable Buss rail power supply. At low levels,
+VCC stays fixed at 10V for example, and it is determined by variable
ref, of full wave rectifier. MOSFET maintain PWM at 10V regulated.
When input signal is applied PWM start modulating the
rectified full wave signal , then BUCK regulator
follows the output voltage mounted on 10V output, , like an envelope voltage
over the output signal. Some designers call this topology
Envelope power supply amplifier.
In
this way power dissipation and efficiency are optimized for
higher power levels.
Tracking
power supply or envelope power supply is basically a combination
of Class H, AB,& D topologies.
Advantages:
Similar
or slightly higher to Class H in efficiency.
A
very efficient amplifier which can deliver the specified output
power with smaller power supply transformer and heat-sink.
No
switching noise due to linear output.
Disadvantages:
Circuit
complexity increases, adding cost
Bad
transient response
EMI
filter is required on power supply section.
Conclusion:
Variations
of Class H are used in high efficiency amplifiers where cost is
not an object and the major limitation is heat-sink size.
