Multi-mode dimmer interfacing including attach state control
A system and method includes a controller that is configured to coordinate (i) a low impedance path for a dimmer current, (ii) attaching a dimmer to a power converter system at the leading edge of a phase-cut, rectified input voltage, (iii), control of switch mode power conversion, and (iv) an inactive state to, for example, reduce the dimmer current while allowing a dimmer to function normally from cycle to cycle of an alternating current (AC) supply voltage. In at least one embodiment, the dimmer functions normally when the dimmer conducts at a correct phase angle indicated by a dimmer input setting and avoids prematurely resetting while conducting. In at least one embodiment, by coordinating functions (i), (ii), (iii), and (iv) the controller controls a power converter system that is compatible with a triac-based dimmer.
1. A method wherein a dimmer voltage to a power converter system comprises four states that occur from:
A. an approximately zero volt crossing of the dimmer voltage of a dimmer until a phase cut, leading edge of the dimmer voltage;
B. an end of state A until a steady state value of a dimmer current has reached a predetermined hold value;
C. an end of state B until energy transferred to a load is sufficient to meet at least one energy transfer parameter; and
D. an end of state C until a beginning of state A;
the method comprising:
for state A, enabling a low impedance path for a dimmer current of the dimmer,
wherein the impedance of the low impedance path is sufficiently low to maintain a stable phase angle of the dimmer;
for state B:
enabling control of switch mode power conversion of the dimmer voltage;
sensing a leading edge of a dimmer input voltage; and
after the sensing the leading edge of the dimmer input voltage, actively controlling a decreasing transition of a current through a triac-based dimmer to prevent a triac of the dimmer from prematurely resetting;
for state C, controlling switch mode power conversion to maintain the dimmer current above a threshold; and
for state D, entering an inactive state, wherein during the inactive state the low impedance path and the control of mode power conversion is disabled.
2. The method of claim 1 wherein the steady state value of the dimmer current is a member of a group consisting of a steady state mean value of the dimmer current, a steady state root mean square value of the dimmer current, or a steady state peak value of the dimmer current.
3. The method of claim 1 wherein the at least one energy transfer parameter comprises a link voltage threshold value, the method further comprising:
determining when a link voltage is less than the link voltage threshold value, wherein sufficient energy is transferred to the load when the link voltage is less than the link voltage threshold value.
4. The method of claim 1 wherein actively controlling a decreasing transition of a current through a triac-based dimmer to prevent a triac of the dimmer from prematurely resetting comprises:
damping the current through the triac-based dimmer to ramp down the current through the triac-based dimmer to a predetermined hold value.
5. The method of claim 1 wherein the predetermined hold value is within the range of 25 am to 75 mA.
6. The method of claim 1 wherein actively controlling a decreasing transition of a current through a triac-based dimmer to prevent a triac of the dimmer from prematurely resetting comprises transitioning the dimmer current from a peak attach current value to an approximately constant steady state current value.
7. The method of claim 6 wherein the peak attach current value is in a range of 300-800 mA, and the approximately constant steady state current value is in a range of 25-75 mA.
8. An apparatus wherein a dimmer voltage to a power converter system comprises four states that occur from:
A. an approximately zero volt crossing of the dimmer voltage of a dimmer until a phase cut, leading edge of the dimmer voltage;
B. an end of state A until a steady state value of a dimmer current has reached a predetermined hold value;
C. an end of state B until energy transferred to a load is sufficient to meet at least one energy transfer parameter; and
D. an end of state C until a beginning of state A;
the apparatus comprising:
a controller configured to:
for state A, enable a low impedance path for a dimmer current of the dimmer, wherein the impedance of the low impedance path is sufficiently low to maintain a stable phase angle of the dimmer;
for state B:
enable control of switch mode power conversion of the dimmer voltage;
sense a leading edge of a dimmer input voltage; and
after the sensing the leading edge of the dimmer input voltage, actively control a decreasing transition of a current through a triac-based dimmer to prevent a triac of the dimmer from prematurely resetting;
for state C, control switch mode power conversion to maintain the dimmer current above a threshold; and
for state D, enter an inactive state, wherein during the inactive state the low impedance path and the control of mode power conversion is disabled.
9. The apparatus of claim 8 wherein the steady state value of the dimmer current is a member of a group consisting of a steady state mean value of the dimmer current, a steady state root mean square value of the dimmer current, or a steady state peak value of the dimmer current.
10. The apparatus of claim 8 wherein the at least one energy transfer parameter comprises a link voltage threshold value, the method further comprising:
determining when a link voltage is less than the link voltage threshold value, wherein sufficient energy is transferred to the load when the link voltage is less than the link voltage threshold value.
11. The apparatus of claim 8 wherein to actively control a decreasing transition of a current through a triac-based dimmer to prevent a triac of the dimmer from prematurely resetting the controller is configured to:
damp the current through the triac-based dimmer to ramp down the current through the triac-based dimmer to a predetermined hold value.
12. The apparatus of claim 8 wherein the predetermined hold value is within the range of 25 am to 75 mA.
13. The apparatus of claim 8 wherein to actively control a decreasing transition of a current through a triac-based dimmer to prevent a triac of the dimmer from prematurely resetting the controller is configured to:
transition the dimmer current from a peak attach current value to an approximately constant steady state current value.
14. The apparatus of claim 8 wherein the peak attach current value is in a range of 300-800 mA, and the approximately constant steady state current value is in a range of 25-75mA.