Constant current and voltage controller in a three-pin package operating in critical conduction mode

• US 20100002480A1
• Filed: 07/01/2008
• Published: 01/07/2010
• Est. Priority Date: 07/01/2008
• Status: Active Grant

• Current Assignee: Active-Semi, Inc. (Qorvo, Inc.)
• Original Assignee: Active-Semi, Inc. (Qorvo, Inc.)
• Inventors: Yang, Jian, Chen, Mingliang, Huynh, Steven
• Granted Patent: US 8,125,798 B2
• Time in Patent Office: Days
• US Class Current: 363/90
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 3/335 using semiconductor devices only
• 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

Abstract

A self-oscillating flyback converter includes a controller integrated circuit housed in a 3-pin package. A switch control terminal is coupled to the base of an inductor switch that controls the current through a primary inductor of the converter. The controller IC adjusts the on time of the switch such that output current remains constant in constant current mode and output voltage remains constant in constant voltage mode. A signal received on a switch control terminal turns the switch off and provides an indication of the output current when the switch is on. A signal received on a feedback terminal powers the controller IC and provides an indication of the output voltage when the switch is off. The controller IC is grounded through a ground terminal. The flyback converter transitions from critical conduction mode to discontinuous conduction mode at light loads to prevent its efficiency from deteriorating at high switching frequencies.

Claims

1. An integrated circuit package, comprising:

a switch control terminal that is coupled to an inductor switch, wherein the inductor switch is turned off by an inductor switch control signal that has an on time, wherein a controller integrated circuit contained in the integrated circuit package adjusts the on time in a constant current mode such that an output current of a flyback converter remains constant and adjusts the on time in a constant voltage mode such that an output voltage of the flyback converter remains constant;

a feedback terminal through which the controller integrated circuit receives power; and

a ground terminal through which the controller integrated circuit is grounded.

2. The integrated circuit package of claim 1, wherein the flyback converter is self-oscillating.

3. The integrated circuit package of claim 1, wherein the integrated circuit package includes no terminals other than the switch control terminal, the feedback terminal and the ground terminal.

4. The integrated circuit package of claim 1, wherein the flyback converter operates in critical conduction mode during the constant current mode.

5. The integrated circuit package of claim 1, wherein a base signal is received on the switch control terminal, and wherein the base signal is indicative of a current flowing through an inductor of the flyback converter.

6. The integrated circuit package of claim 5, wherein the controller integrated circuit includes an auto-zeroing circuit, wherein the inductor switch exhibits a base-emitter offset voltage, wherein the base signal has a voltage, and wherein the auto-zeroing circuit determines the current flowing through the inductor by auto-zeroing the voltage of the base signal such that the base-emitter offset voltage is subtracted out.

7. The integrated circuit package of claim 5, wherein the inductor switch has a base and a collector, wherein the switch control terminal is coupled to the base, and wherein the collector is coupled to the inductor.

8. The integrated circuit package of claim 1, wherein a feedback signal is received on the feedback terminal, and wherein the feedback signal is indicative of a voltage across an inductor of the flyback converter.

9. An integrated circuit package, comprising:

a switch control terminal that is coupled to an external inductor switch and to an internal power switch, wherein the internal power switch is turned off by an inductor switch control signal that has an on time, and wherein a controller integrated circuit contained in the integrated circuit package adjusts the on time such that an output voltage of a flyback converter remains constant;

a feedback terminal that receives a feedback signal, wherein the feedback signal is derived from a voltage across a first inductor of the flyback converter, wherein the feedback signal provides power to the controller integrated circuit, and wherein the feedback signal is used by the controller integrated circuit to generate the inductor switch control signal; and

a ground terminal through which the controller integrated circuit is grounded, wherein the integrated circuit package includes no terminals other than the switch control terminal, the feedback terminal and the ground terminal.

10. The integrated circuit package of claim 9, wherein the controller integrated circuit adjusts the on time in a constant voltage mode such that the output voltage of the flyback converter remains constant, wherein the controller integrated circuit adjusts the on time in a constant current mode such that an output current of the flyback converter remains constant, and wherein the flyback converter operates in critical conduction mode during the constant current mode.

11. The integrated circuit package of claim 9, wherein the feedback signal provides power to the controller integrated circuit when the external inductor switch is on, and wherein the feedback signal is used by the controller integrated circuit to determine the output voltage of the flyback converter when the external inductor switch is off.

12. The integrated circuit package of claim 9, wherein the voltage across the first inductor is a feedback voltage, wherein the controller integrated circuit includes a switch capacitor circuit, wherein the output voltage of the flyback converter is determined by the switch capacitor circuit providing the feedback voltage with a negative magnitude to a plate of a capacitor and a reference voltage of a similar positive magnitude to another plate of the capacitor.

13. The integrated circuit package of claim 9, wherein a base signal is received on the switch control terminal, and wherein the base signal is indicative of a rate at which current flows through a second inductor of the flyback converter.

14. The integrated circuit package of claim 13, wherein the first inductor is an auxiliary inductor of the flyback converter, and wherein the second inductor is a primary inductor of the flyback converter.

15. The integrated circuit package of claim 9, wherein in a constant voltage mode the output current of the flyback converter is less than a predetermined current limit, and wherein in the constant voltage mode the controller integrated circuit adjusts the on time such that the output voltage of the flyback converter remains constant, and wherein the flyback converter operates in discontinuous conduction mode in the constant voltage mode when the output current of the flyback converter falls below a set percentage of the predetermined current limit.

16. A power converter, comprising:

a primary inductor;

an inductor switch coupled to the primary inductor, wherein the inductor switch has a base;

an auxiliary inductor that is magnetically coupled to the primary inductor; and

a controller integrated circuit having an internal power switch, a feedback bond pad, a base bond pad and a ground bond pad, wherein the base bond pad is coupled to the internal power switch and to the base of the inductor switch, wherein the internal power switch is turned off by an inductor switch control signal that has an on time, wherein the controller integrated circuit receives power through the feedback bond pad, wherein the feedback bond pad receives a feedback signal that is used by the controller integrated circuit to generate the inductor switch control signal, and wherein the controller integrated circuit adjusts the on time of the inductor switch control signal in a constant current mode such that an output current of the power converter remains constant.

17. The power converter of claim 16, wherein the inductor switch control signal is deasserted during the on time of the inductor switch control signal.

18. The power converter of claim 16, wherein the power converter operates in critical conduction mode in the constant current mode.

19. The power converter of claim 16, wherein the controller integrated circuit has no bond pads other than the feedback bond pad, the base bond pad and the ground bond pad.

20. The power converter of claim 16, wherein the feedback signal is derived from a voltage across the auxiliary inductor, and wherein the controller integrated circuit adjusts the on time of the inductor switch control signal in a constant voltage mode using the feedback signal when the inductor switch is off.

21. The power converter of claim 16, wherein a base signal is received onto the base bond pad, wherein the base signal is indicative of a current flowing through the primary inductor, and wherein the controller integrated circuit adjusts the on time of the inductor switch control signal in a constant current mode using the base signal when the inductor switch is on.

22. The power converter of claim 16, wherein an inductor current flowing through the primary inductor has a magnitude, wherein the inductor switch exhibits a base-emitter offset voltage, wherein a base signal having a voltage is received onto the base bond pad, wherein the controller integrated circuit generates an auto-zeroed voltage of the base signal by subtracting the base-emitter offset voltage from the voltage of the base signal, and wherein the controller integrated circuit determines the magnitude of the inductor current using the auto-zeroed voltage of the base signal.

23. A method comprising:

magnetically coupling a primary inductor to an auxiliary inductor of a power converter, wherein an inductor current flows through the primary inductor during an on time of an inductor switch, wherein the power converter has a controller integrated circuit with a feedback bond pad and a base bond pad, and wherein the power converter generates an output current and an output voltage;

receiving onto the feedback bond pad a feedback signal that is derived from a voltage across the auxiliary inductor;

powering the controller integrated circuit using the feedback signal;

determining the output voltage using the feedback signal;

receiving onto the base bond pad a base signal that is indicative of the inductor current;

turning off the inductor switch using the base signal; and

determining the output current using the base signal.

24. The method of claim 23, further comprising:

adjusting the on time of the inductor switch using the base signal such that the output voltage remains constant while the output current is below a predetermined current limit; and

adjusting the on time of the inductor switch using the base signal such that the output current remains constant at the predetermined current limit.

25. The method of claim 23, wherein the output voltage is determined using the feedback signal while the inductor switch is off.

26. The method of claim 23, wherein the output current is determined using the base signal while the inductor switch is on.

27. The method of claim 23, wherein the controller integrated circuit is contained in an integrated circuit package, wherein the integrated circuit package has a feedback terminal, a switch control terminal and a ground terminal, wherein the controller integrated circuit has a ground bond pad, wherein the feedback terminal is coupled to the feedback bond pad, the switch control terminal is coupled to the base bond pad and the ground terminal is coupled to the ground bond pad, and wherein the integrated circuit package includes no terminals other than the feedback terminal, the switch control terminal and the ground terminal.

28. A power converter, comprising:

an inductor switch having a collector and a base, wherein the inductor switch has an on time;

a primary inductor coupled to the collector of the inductor switch;

an auxiliary inductor that is magnetically coupled to the primary inductor; and

a base bond pad of a controller integrated circuit, wherein the base bond pad is coupled to the base of the inductor switch, wherein a base signal present on the base bond pad turns off the inductor switch; and

means for receiving a feedback signal that is derived from a voltage across the auxiliary inductor, wherein the feedback signal is used both to power the controller integrated circuit and to adjust the on time of the inductor switch such that an output voltage of the power converter remains constant.

29. The power converter of claim 28, further comprising:

a ground bond pad of the controller integrated circuit, wherein no current is conveyed to or from the controller integrated circuit except through the base bond pad, the ground bond pad and the means.

30. The power converter of claim 28, wherein the controller integrated circuit is packaged in an integrated circuit package that includes a switch control terminal, a feedback terminal and a ground terminal, wherein the base bond pad is coupled to the switch control terminal, wherein the means is coupled to the feedback terminal, and wherein the integrated circuit package includes no more than three terminals.

31. The power converter of claim 28, wherein the inductor switch, the primary inductor, the auxiliary inductor, the base bond pad and the means are on a primary side of the power converter, wherein a secondary inductor is on a secondary side of the power converter, and wherein the controller integrated circuit receives no signal from the secondary side.