Methods and systems for improving load transient response in LLC converters

• US 9,608,513 B2
• Filed: 03/05/2014
• Issued: 03/28/2017
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Acleap Power Incorporated
• Original Assignee: General Electric Company
• Inventors: Reddy, Raghothama
• Primary Examiner(s): Laxton, Gary L
• Application Number:
  US14/197,529
• Publication Number:
  US 20140268905A1
• Time in Patent Office: 1,119 Days
• Field of Search: 363/21.02, 363/21.03, 323/205, 323/207
• US Class Current: 1/1
• CPC Class Codes: H02M 1/0019 the disturbance parameters being load current fluctuations
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

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.

Claims

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.