DC/DC CONVERTER WITH MULTIPLE OUTPUTS

• US 20120153866A1
• Filed: 12/20/2011
• Published: 06/21/2012
• Est. Priority Date: 12/20/2010
• Status: Active Grant

• Current Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Original Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Inventors: LIU, Da
• Granted Patent: US 8,587,221 B2
• Time in Patent Office: Days
• US Class Current: 315/294
• CPC Class Codes: H02M 3/33561 having more than one ouput with independent control
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

Embodiments of the invention provide a DC/DC converter. The DC/DC converter includes a transformer, a switch controller and a driver controller. The transformer has a primary winding coupled to a power source, a first secondary winding provides a first output voltage to a first load, and a second secondary winding provides a second output voltage to a second load. The switch controller is coupled to the primary winding and controls a first switch coupled to the primary winding to control input power to the primary winding and to regulate the first output voltage based on a power requirement of the first load. The driver controller is coupled to the second secondary winding and generates a pulse modulation signal to alternately turn on and turn off a second switch coupled to the second secondary winding to regulate the second output voltage based on a power requirement of the second load.

Claims

1. A DC/DC converter comprising:

a transformer having a primary winding coupled to a power source, a first secondary winding that provides a first output voltage to a first load, and a second secondary winding that provides a second output voltage to a second load;

a switch controller, coupled to said primary winding, that controls a first switch coupled to said primary winding so as to control input power to said primary winding and to regulate said first output voltage based on a power requirement of said first load; and

a driver controller, coupled to said second secondary winding, that generates a pulse modulation signal to alternately turn on and turn off a second switch coupled to said second secondary winding to regulate said second output voltage based on a power requirement of said second load.

2. The DC/DC converter of claim 1, wherein said transformer further comprises an auxiliary winding that provides a supply voltage to said switch controller.

3. The DC/DC converter of claim 1, wherein a source of said second switch receives said first output voltage from said first secondary winding.

4. The DC/DC converter of claim 1, wherein said DC/DC converter further comprises a transient voltage suppressor coupled between a source and a drain of said second switch.

5. The DC/DC converter of claim 1, wherein said switch controller generates a pulse-width modulation (PWM) signal to alternately turn on and turn off said first switch, and regulates said first output voltage by adjusting a duty cycle of said PWM signal.

6. The DC/DC converter of claim 1, wherein said driver controller comprises:

a reference signal generator that generates a reference signal based on said power requirement of said second load; and

an error amplifier that receives said reference signal and a sensing signal indicative of said second output voltage, and that generates an error signal by comparing said reference signal with said sensing signal.

7. The DC/DC converter of claim 6, wherein said second load comprises a plurality of light sources, and wherein said driver controller further comprises a current regulation unit that balances currents through said plurality of light sources.

8. The DC/DC converter of claim 6, wherein said driver controller further comprises a comparator that compares said error signal with a ramp signal to generate said pulse modulation signal.

9. The DC/DC converter of claim 1, wherein said driver controller further receives a synchronous signal indicative of an operation frequency of said switch controller from said first secondary winding and generates said pulse modulation signal based on said synchronous signal to synchronize an operation frequency of said driver controller with said operation frequency of said switch controller.

10. The DC/DC converter of claim 9, wherein said pulse modulation signal remains at a constant level to turn off said second switch if a voltage of said synchronous signal is at a first level, and wherein said pulse modulation signal comprises a plurality of pulses to alternately turn on and turn off said second switch if said voltage of said synchronous signal is at a second level.

11. The DC/DC converter of claim 1, wherein when a voltage of a feedback signal indicating that said first output voltage is greater than a target regulation voltage or when a voltage of a sensing signal indicating that said second output voltage is greater than a predetermined safety voltage, said driver controller reduces said input power to said primary winding.

12. A driver controller for controlling a first output voltage delivered from a transformer to a first load, said driver controller comprising:

a synchronous terminal that receives a synchronous signal indicative of an operation frequency of a switch controller from a first secondary winding of said transformer;

a voltage sensing terminal that receives a voltage sensing signal indicative of said first output voltage;

a current sensing terminal that receives a current sensing signal indicating a current through said first load; and

a driving terminal that generates a pulse modulation signal based on said synchronous signal, said voltage sensing signal, and said current sensing signal to regulate said first output voltage, and to synchronize an operation frequency of said driver controller with said operation frequency of said switch controller,

wherein said driver controller is coupled to a second secondary winding of said transformer, and

wherein said switch controller generates a pulse-width modulation (PWM) signal to alternately turn on and turn off a first switch coupled to a primary winding of said transformer and controls input power to said primary winding to regulate a second output voltage by adjusting a duty cycle of said PWM signal.

13. The driver controller of claim 12, wherein said pulse modulation signal alternately turns on and turns off a second switch coupled to said second secondary winding to regulate said first output voltage based on a power requirement of said first load.

14. The driver controller of claim 13, wherein a source of said second switch receives said second output voltage from said first secondary winding.

15. The driver controller of claim 12, wherein a current flows through said second secondary winding if said pulse modulation signal is in a first state, and wherein said current of said second secondary winding remains cut-off if said pulse modulation signal is in a second state.

16. The driver controller of claim 15, wherein said pulse modulation signal remains at said second state if a voltage of said synchronous signal is at a first level, and wherein said pulse modulation signal comprises a plurality of pulses if said voltage of said synchronous signal is at a second level.

17. The driver controller of claim 12, wherein said first load comprises a plurality of light sources, and wherein said driver controller further comprises a current regulation unit that balances a plurality of currents through said plurality of light sources.

18. The driver controller of claim 17, wherein said current regulation unit receives said current sensing signal, and controls an ON/OFF status and dimming of said plurality of light sources based on an ON/OFF signal and a dimming signal respectively.

19. The driver controller of claim 12, wherein when a voltage of a feedback signal indicating said second output voltage is greater than a target regulation voltage or when a voltage of said voltage sensing signal is greater than a predetermined safety voltage, said driver controller reduces said input power to said primary winding.

20. The driver controller of claim 19, wherein said driver controller further comprises a third switch coupled between an over-voltage protection circuit and ground, and wherein said over-voltage protection circuit turns on said third switch to pull a compensation signal to zero when said voltage of said feedback signal is greater than said first predetermined safety voltage or when said voltage of said voltage sensing signal is greater than said second predetermined safety voltage.