ADAPTIVE CURRENT LIMITER AND DIMMER SYSTEM INCLUDING THE SAME

• US 20120026761A1
• Filed: 07/28/2010
• Published: 02/02/2012
• Est. Priority Date: 07/28/2010
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Young, James Roy
• Granted Patent: US 9,124,171 B2
• Time in Patent Office: Days
• US Class Current: 363/44
• CPC Class Codes: H02M 1/0045 Converters combining the concepts of switch-mode regulation and linear regulation, e.g. linear pre-regulator to switching converter, linear and switching converter in parallel, same converter or same transistor operating either in linear or switching mode
• CPC Class Codes: H02M 1/12 Arrangements for reducing harmonics from ac input or output
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: H02M 7/125 Avoiding or suppressing excessive transient voltages or currents
• CPC Class Codes: H05B 45/31 Phase-control circuits
• CPC Class Codes: H05B 45/36 Circuits for reducing or suppressing harmonics, ripples or electromagnetic interferences [EMI]

Abstract

In an embodiment, an adaptive current limiter includes a sense element, a current pass element, and a controller. The sense element includes a first sense terminal coupled to a power supply terminal and a second sense terminal. The sense element generates a sense voltage in response to a feedback current. The current pass element includes a first terminal for receiving the feedback current, a second terminal coupled to the second sense terminal, and a control terminal. The controller is coupled to the sense element and to the control terminal for adjusting the feedback current conducted by the current pass element based on the sense voltage and a time-varying voltage signal.

Claims

1. An adaptive current limiter comprising:

a sense element including a first sense terminal coupled to a power supply terminal and a second sense terminal, the sense element to generate a sense voltage in response to a feedback current;

a current pass element including a first terminal for receiving the feedback current, a second terminal coupled to the second sense terminal, and a control terminal; and

a controller coupled to the sense element and to the control terminal, the controller for adjusting the feedback current conducted by the current pass element based on the sense voltage and a time-varying voltage signal.

2. The adaptive current limiter of claim 1, wherein the controller comprises a reference generator to generate the time-varying voltage signal.

3. The adaptive current limiter of claim 2, wherein the time-varying voltage signal comprises a ramp signal that increases substantially linearly over a pre-determined time.

4. The adaptive current limiter of claim 2, wherein the time-varying voltage signal comprises a ramp signal that increases substantially exponentially over a pre-determined period of time.

5. The adaptive current limiter of claim 2, wherein the controller further comprises:

an amplifier including a first input coupled to the sense element to receive the sense voltage, a second input coupled to the reference generator to receive the time-varying voltage signal, and an output coupled to the control terminal of the current pass element.

6. The adaptive current limiter of claim 1, wherein the controller increases the feedback current conducted by the current pass element from a first current level to a second current level over a pre-determined period of time.

7. The adaptive current limiter of claim 1, wherein the current pass element comprises:

a transistor including a first current electrode for receiving the feedback current, a control electrode coupled to the controller, and a second current electrode coupled to the sense element.

8. The adaptive current limiter of claim 7, wherein the controller comprises:

a second transistor including a first current electrode coupled to the control electrode of the transistor, a control electrode, and a second current electrode coupled to the power supply terminal;

a first resistor including a first terminal coupled to the second sense terminal and a second terminal coupled to the control electrode of the second transistor;

a second resistor including a first terminal coupled to the control terminal of the second transistor and a second terminal coupled to the power supply terminal; and

a third resistor including a first terminal coupled to the second sense terminal and a second terminal; and

a capacitor including a first electrode coupled to the second terminal of the third resistor and a second electrode coupled to the control terminal of the second transistor.

9. The adaptive current limiter of claim 8, wherein the third resistor and the capacitor determine the time-varying voltage signal.

10. A current limiter circuit comprising:

a current pass element including a first current electrode adapted to couple to a load circuit to receive a feedback current, a second current electrode, and a control electrode;

a sense resistor including a first sense terminal adapted to couple to a power supply terminal and a second sense terminal coupled to the second current electrode of the current pass element, the sense resistor for generating a sense voltage proportional to the feedback current; and

a controller coupled to the sense resistor and to the control electrode, the controller for generating a control signal based on the sense voltage and a time-varying signal to controllably increase a current conducted by the current pass element over a pre-determined time.

11. The current limiter circuit of claim 10, wherein the controller comprises:

a reference generator for providing the time-varying signal; and

an amplifier including a first input for receiving the time-varying signal, a second input for receiving the sense voltage, and an output coupled to the control electrode of the current pass element.

12. The current limiter circuit of claim 10, further comprising:

a resistor including a first terminal coupled to the second sense terminal and including a second terminal;

a capacitor including a first electrode coupled to the second terminal of the resistor and a second electrode; and

a transistor including a first terminal coupled to the control electrode of the current pass element, a control terminal coupled to the second electrode of the capacitor, and an second terminal coupled to the first sense terminal of the sense resistor; and

whereby the resistor and the capacitor define a time constant for producing the time-varying signal applied to the control terminal of the transistor.

13. The current limiter circuit of claim 12, wherein the controller further comprises:

a second resistor including a first terminal coupled to the second sense terminal of the sense resistor and including a second terminal coupled to the control terminal of the transistor; and

a second resistor including a first terminal coupled to the control terminal of the transistor and including a second terminal coupled to the first sense terminal of the sense resistor and to the second terminal of the transistor.

14. The current limiter circuit of claim 10, further comprising:

a breakdown diode including an anode coupled to the second sense terminal of the sense resistor and a cathode coupled to the control electrode of the current pass element, the breakdown diode adapted to conduct current from the cathode to the anode when a voltage potential between the control electrode and the second current electrode of the current pass element exceeds a breakdown voltage off the breakdown diode.

15. A phase-cut dimmer system comprising:

first and second supply terminals;

a phase-cut dimmer circuit adapted to be coupled to an alternating current (AC) power supply for generating a phase-cut signal;

a full-wave rectifier coupled to the phase-cut dimmer circuit for generating a rectified version of the phase-cut signal, the full-wave rectifier coupled to the first and second supply terminals for providing a rectified power supply;

an electromagnetic interference (EMI) filter coupled to the first and second supply terminals; and

a current limiter circuit coupled to the second supply terminal and to the EMI filter, the current limiter circuit responsive to a feedback current and to a time-varying signal to adjust the feedback current over a pre-determined time.

16. The phase-cut dimmer system of claim 15, wherein the current limiter circuit increases the feedback current substantially linearly over the pre-determined time.

17. The phase-cut dimmer system of claim 15, wherein the current limiter circuit comprises:

a reference generator for generating the time-varying signal;

a sense resistor for converting the feedback current into a sense voltage;

an amplifier responsive to the time-varying signal and the sense voltage to produce a time-varying control signal; and

a current pass element including a first terminal for receiving the feedback current, a second terminal coupled to the sense resistor, and a control terminal coupled to the amplifier and responsive to the control signal for limiting the feedback current.

18. The phase-cut dimmer system of claim 15, wherein the current limiter circuit comprises:

a first transistor including a first current electrode for receiving the feedback current, a second current electrode, and a control electrode;

a bias circuit including a first terminal coupled to the first supply terminal and a second terminal coupled to the control electrode of the transistor;

a second transistor including a first current electrode coupled to the control electrode of the first transistor, a control electrode, and a second current electrode coupled to the second supply terminal;

a sense resistor including a first sense terminal coupled to the second current electrode of the first transistor and a second sense terminal coupled to the second supply terminal;

a first resistor including a first terminal coupled to the second sense terminal and a second terminal coupled to the control electrode of the second transistor;

a second resistor including a first terminal coupled to the control electrode of the second transistor and a second terminal coupled to the second current electrode of the second transistor; and

a signal generator coupled between the second sense terminal of the sense resistor and the control electrode of the second transistor for providing the time-varying signal.

19. The phase-cut dimmer system of claim 18, wherein the time-varying signal generator comprises:

a third resistor including a first terminal coupled to the second sense terminal of the sense resistor and a second terminal; and

a capacitor including a first electrode coupled to the second terminal of the third resistor and a second electrode coupled to the control electrode of the second transistor.

20. The phase-cut dimmer system of claim 15, further comprising:

first and second output terminals coupled to the EMI filter;

an isolation circuit including a first terminal coupled to the first output terminal and a second terminal coupled to the second output terminal, the isolation circuit adapted to be coupled to a load circuit; and

wherein the load circuit comprises one of a light-emitting diode (LED) lamp, a compact florescent lamp, and a motor.