Universal system structure for low power adapters
View Patent ↗A two-stage power converter architecture including an isolation transformer and rectification of the isolation transformer output by an LLC resonant circuit and methodology for operating the same feeds an output voltage back to a circuit for generating waveforms for controlling a totem pole circuit to provide output voltage regulation as well as rectification of AC input voltage. The circuit for controlling the totem pole circuit may also be responsive to the AC input power waveform to provide power factor correction (PFC), in which case, the feedback signal provides additional pulse width modulation of the PFC signals. Bus capacitor size may also be reduced by injecting harmonics of the AC input waveform into the feedback signal which also serves to substantially maintain efficiency of the (preferably LLC) resonant second stage.
1. A power converter architecture including
a first stage comprising a totem pole circuit and a controller for switches in said totem pole circuit,
a second stage comprising a resonant direct current transformer (DCX) circuit and connected to said first stage by a voltage bus,
a feedback circuit connecting an output of said DCX to said controller of said totem pole circuit whereby said totem pole circuit provides output voltage regulation as well as rectification of AC input power,
a comparator in said feedback circuit for comparing an output voltage with a reference voltage, and
a voltage adder for injecting at least one harmonic of an AC input voltage into a control signal output by said comparator.
2. The power converter architecture as recited in claim 1 , further comprising
an additional comparator for comparing said control signal with a ramp waveform to develop a pulse width modulated signal.
3. The power converter architecture as recited in claim 2 , further including
a pulse width modulator to generate pulse width modulated signals for controlling said totem pole circuit and further pulse width modulating said pulse width modulated signals to achieve voltage regulation.
4. The power converter architecture as recited in claim 3 , wherein said pulse width modulator is responsive to a waveform of AC input power to provide power factor correction.
5. The power converter architecture as recited in claim 1 , wherein said comparator comprises an amplifier providing gain in said feedback circuit.
6. The power converter architecture as recited in claim 5 , further comprising
an additional comparator for comparing said control signal with a ramp waveform to develop a pulse width modulated signal.
7. The power converter architecture as recited in claim 6 , further including
a pulse width modulator to generate pulse width modulated signals for controlling said totem pole circuit and further pulse width modulating said pulse width modulated signals to achieve voltage regulation.
8. The power converter architecture as recited in claim 7 , wherein said pulse width modulator is responsive to a waveform of AC input power to provide power factor correction.
9. A method of operating a power converter, said method comprising steps of
rectifying input AC voltage with a totem pole switching circuit to provide DC power,
periodically connecting and disconnecting a primary winding of an isolation transformer to said DC power,
rectifying a voltage on a secondary winding of said isolation transformer to provide an output voltage, and
controlling a circuit for driving switches of said totem pole switching circuit in accordance with said output voltage to provide regulation of said output voltage,
providing amplification of said control feedback signal,
injecting at least one harmonic of said AC power into said control feedback signal, and
comparing said output voltage with a reference voltage to provide a control feedback voltage,
wherein said controlling step is also responsive to a waveform of said AC input voltage to perform power factor correction,
wherein said step of periodically connecting and disconnecting said primary winding of said isolation transformer to said DC power is performed at a constant frequency.
10. A method of operating a power converter, said method comprising steps of
rectifying input AC voltage with a totem pole switching circuit to provide DC power,
periodically connecting and disconnecting a primary winding of an isolation transformer to said DC power,
rectifying a voltage on a secondary winding of said isolation transformer to provide an output voltage,
controlling a circuit for driving switches of said totem pole switching circuit in accordance with said output voltage to provide regulation of said output voltage, and
injecting at least one harmonic of said AC power into said control feedback signal.