Methods and systems for improving load transient response in LLC converters
View Patent ↗Methods and systems for improving load transient response in LLC converters are provided herein. The method includes coupling a current sensing circuit to an output of the LLC converter, sensing load current of the LLC converter, and increasing a setpoint voltage for a power factor correction (PFC) circuit output based on the sensed load current.
1. A method of improving load transient response in an inductor-inductor-capacitor (LLC) converter, said method comprising:
providing a transformer that includes a primary side for receiving voltage output by a power factor correction (PFC) circuit, a secondary side for generating output voltage, and an isolation barrier that isolates the primary and secondary sides, the primary side including a resonant capacitor coupled thereto;
coupling a current sensing circuit to the resonant capacitor on the primary side of the LLC converter;
indirectly sensing, by the current sensing circuit, load current across the resonant capacitor on the primary side of the LLC converter;
automatically transmitting, by the current sensing circuit, the sensed load current to a boost controller before output voltage of the LLC converter begins to sag upon sensing a change in the load current; and
increasing, by the boost controller, a setpoint voltage for the PFC circuit output based solely on the indirectly sensed load current to operate the LLC converter at approximately a resonant frequency of the LLC converter.
2. The method according to claim 1 , wherein the LLC converter includes a boost controller, said method further comprises feeding the sensed current to the boost controller.
3. The method according to claim 2 , further comprising feeding the sensed current as an analog signal to an analog-to-digital (A/D) converter of the boost controller.
4. The method according to claim 3 , further comprising:
converting the analog signal to a digital signal; and
transmitting the digital signal to a digital signal processor (DSP) of the boost controller.
5. The method according to claim 4 , further comprising pulse width modulating the digital signal to activate a switch associated with the PFC circuit.
6. The method according to claim 1 , further comprising automatically responding, by the current sensing circuit, to a change in load current before output voltage of the LLC converter begins to sag.
7. An inductor-inductor-capacitor (LLC) converter comprising:
a power factor correction (PFC) circuit;
a transformer coupled downstream from said PFC circuit, said transformer comprising a primary side for receiving voltage output by said PFC circuit, a secondary side for generating output voltage, and an isolation barrier that isolates the primary and secondary sides, the primary side including a resonant capacitor coupled thereto;
a current sensing circuit configured to:
indirectly sense load current across said resonant capacitor on the primary side of said LLC converter; and
automatically transmit the sensed load current to a boost controller before output voltage of the LLC converter begins to sag upon sensing a change in the load current; and
a boost controller coupled to said current sensing circuit on the primary side, said boost controller configured to activate a PFC circuit switch to increase a setpoint voltage for said PFC circuit output based solely on the indirectly sensed load current to operate said LLC converter at approximately a resonant frequency of said LLC converter.
8. The converter according to claim 7 , wherein said boost controller comprises an analog-to-digital (A/D) converter configured to receive an analog signal from said current sensing circuit.
9. The converter according to claim 8 , wherein said A/D converter is further configured to:
convert the analog signal to a digital signal; and
transmit the digital signal to a digital signal processor (DSP) of said boost controller.
10. The converter according to claim 9 , wherein said DSP comprises a pulse width modulator configured to activate said PFC circuit switch.
11. The converter according to claim 7 , wherein said current sensing circuit is configured to automatically respond to a change in load current before output voltage of the LLC converter begins to sag.
12. An alternating current (AC) to direct current (DC) converter comprising:
a rectifier;
a power factor correction (PFC) circuit coupled to said rectifier; and
an inductor-inductor-capacitor (LLC) converter coupled to said PFC circuit, said LLC converter comprising:
a transformer coupled downstream from said PFC circuit, said transformer comprising a primary side for receiving voltage output by said PFC circuit, a secondary side for generating output voltage, and an isolation barrier that isolates the primary and secondary sides, the primary side including a resonant capacitor coupled thereto;
a current sensing circuit configured to:
indirectly sense load current across said resonant capacitor on the primary side of said LLC converter; and
automatically transmit the sensed load current to a boost controller before output voltage of the LLC converter begins to sag upon sensing a change in the load current; and
a boost controller coupled to said current sensing circuit on the primary side, said boost controller configured to activate a PFC circuit switch to increase a setpoint voltage for said PFC circuit output based solely on the indirectly sensed load current to operate said LLC converter at approximately a resonant frequency of said LLC converter.
13. The converter according to claim 12 , wherein said boost controller comprises an analog-to-digital (A/D) converter configured to receive an analog signal from said current sensing circuit.
14. The converter according to claim 12 , wherein said current sensing circuit is configured to automatically respond to a change in load current before output voltage of the LLC converter begins to sag.