Controllable-load circuit for use with a load control device
A load control device for controlling the amount of power delivered from an AC power source to an electrical load is operable to conduct enough current through a thyristor of a connected dimmer switch to exceed rated latching and holding currents of the thyristor. The load control device comprises a controllable-load circuit operable to conduct a controllable-load current through the thyristor of the dimmer switch. The load control device disables the controllable-load circuit when the phase-control voltage received from the dimmer switch is a reverse phase-control waveform. When the phase-control voltage received from the dimmer switch is a forward phase-control waveform, the load control device is operable to decrease the magnitude of the controllable-load current so as to conduct only enough current as is required in order to exceed rated latching and holding currents of the thyristor.
1. A light-emitting diode (LED) drive system, comprising:
input terminals to receive a phase-control voltage from a dimmer switch;
output terminals to provide an output voltage;
an LED drive control circuit to determine whether the received phase-control voltage comprises a forward phase-control waveform or a reverse phase-control waveform; and
a selectively enablable controllable-load circuit conductively coupled in parallel with an LED lighting load coupled to the output terminals and communicatively coupled to the LED drive control circuit, the controllable-load circuit to permit a controllable-load current to flow through the dimmer switch when enabled;
wherein, responsive to the determination that the phase-control voltage is a forward phase-control waveform, the LED drive control circuit to:
enable the controllable-load circuit; and
adjust a magnitude of the controllable-load current through the dimmer switch such that the controllable-load current exceeds at least one of:
a rated latching current of the dimmer switch; or
a rated holding current of the dimmer switch.
2. The electric load control system of claim 1 wherein, responsive to the determination that the phase-control voltage is a reverse phase-control waveform, the LED drive control circuit to further:
disable the controllable-load circuit such that the controllable-load circuit does not conduct the controllable-load current through the dimmer switch.
3. The electric load control system of claim 1 , the LED drive control circuit to monitor a magnitude of the phase-control voltage received from the dimmer switch to determine whether the phase-control voltage is the forward phase-control waveform or the reverse phase-control waveform.
4. The electric load control system of claim 1 , the LED drive control circuit to compare the magnitude of the phase-control voltage to a voltage threshold after detecting a voltage transition of the phase-control voltage to determine whether the phase-control voltage is the forward phase-control waveform or the reverse phase-control waveform, the LED drive control circuit to determine the phase-control voltage is the forward phase-control waveform if the magnitude of the phase-control voltage is consistently larger than the voltage threshold.
5. A light-emitting diode drive method, comprising:
determining, by an LED drive control circuit, whether a phase-control voltage received from a dimmer switch comprises a forward phase-control waveform or a reverse phase-control waveform; and
responsive to the determination that the phase-control voltage is a forward phase-control waveform:
selectively enabling, by the LED drive control circuit, a controllable-load circuit, the controllable-load circuit conductively coupled in parallel with an LED lighting load, the controllable-load circuit to permit a controllable-load current to flow through the dimmer switch when enabled;
causing, by the LED drive control circuit, an adjustment of the controllable-load current through the dimmer switch such that the controllable-load current exceeds at least one of:
a rated latching current of the dimmer switch; or
a rated holding current of the dimmer switch.
6. The method of claim 5 further comprising:
selectively disabling, by the LED drive circuit, the controllable-load circuit such that the controllable-load circuit does not conduct the controllable-load current through the dimmer switch.
7. The method of claim 5 , further comprising:
monitoring, by the LED drive circuit, a magnitude of the phase-control voltage received from the dimmer switch to determine whether the phase-control voltage is the forward phase-control waveform or the reverse phase-control waveform.
8. The method of claim 5 , further comprising:
comparing, by the LED drive control circuit, the magnitude of the phase-control voltage to a voltage threshold responsive to detection of a voltage transition of the phase-control voltage to determine whether the phase-control voltage is the forward phase-control waveform or the reverse phase-control waveform; and
determining, by the LED drive control circuit, the phase-control voltage is the forward phase-control waveform responsive to the magnitude of the phase-control voltage being consistently larger than the voltage threshold.
9. A non-transitory, machine-readable, storage device that includes instructions that, when executed by a light-emitting diode (LED) drive control circuit, cause the LED drive circuit to:
determine whether a phase-control voltage received from a dimmer switch comprises a forward phase-control waveform or a reverse phase-control waveform; and
responsive to the determination by the LED drive control circuit that the phase-control voltage is a forward phase-control waveform:
selectively enable a controllable-load circuit, the controllable-load circuit conductively coupled in parallel with an LED lighting load, the controllable-load circuit to permit a controllable-load current to flow through the dimmer switch when enabled;
cause an adjustment of the controllable-load current through the dimmer switch such that the controllable-load current exceeds at least one of:
a rated latching current of the dimmer switch; or
a rated holding current of the dimmer switch.
10. The non-transitory, machine-readable, storage device of claim 9 , wherein the instructions, when executed by the LED drive control circuitry, cause the LED drive control circuitry to further:
selectively disable the controllable-load circuit such that the controllable-load circuit does not conduct the controllable-load current through the dimmer switch.
11. The non-transitory, machine-readable, storage device of claim 9 , wherein the instructions, when executed by the LED drive control circuitry, cause the LED drive control circuitry to further:
monitor a magnitude of the phase-control voltage received from the dimmer switch to determine whether the phase-control voltage is the forward phase-control waveform or the reverse phase-control waveform.
12. The non-transitory, machine-readable, storage device of claim 9 , wherein the instructions, when executed by the LED drive control circuitry, cause the LED drive control circuitry to further:
compare the magnitude of the phase-control voltage to a voltage threshold responsive to detection of a voltage transition of the phase-control voltage to determine whether the phase-control voltage is the forward phase-control waveform or the reverse phase-control waveform; and
determine the phase-control voltage is the forward phase-control waveform responsive to the magnitude of the phase-control voltage being consistently larger than the voltage threshold.