Emergency lighting system
An emergency power system ( 100 ) and emergency lighting dimming method are disclosed. The emergency power system ( 100 ) includes a power source ( 10 ), a phase-cut waveform generator ( 11, 13, 300, 310, 311, 400, 410, 411 ) coupled to the output of the power source ( 10 ) and arranged to provide a phase-cut waveform (FIGS. 2 and 3 ) to a load ( 12 ). The load may be one or more emergency lighting devices. A feedback detection module ( 14, 201 ) may be is used to monitor the voltage and/or current data supplied to the load ( 12 ) by the phase-cut waveform generator. A controller ( 13, 202 - 205 ) controls the phase-cur waveform generator ( 11, 13, 300, 310, 311, 400, 410, 411 ) to adjust the power level of the load ( 12 ) by modifying the phase-cur waveform based upon the monitored voltage and/or current data and reference data to achieve the appropriate dimming level.
1 . An emergency power system, comprising:
a power source,
a phase-cut waveform generator including a wave generator coupled to the output of the power source and arranged to provide a phase-cut waveform to a load, by modulating an on-time step function to a sinusoidal pulse width modulation signal and filtering to generate the phase-cut waveform;
a detection module arranged to monitor voltage and/or current data supplied to the load by the phase-cut waveform generator; and
a controller arranged to control the phase-cut waveform generator to adjust a power level of the load by modifying the phase-cut waveform based upon the monitored voltage and/or current data and reference data.
2 . The emergency power system of claim 1 , wherein the phase-cut waveform generator generates the phase-cut waveform from a sine, rectangular and/or triangular wave.
3 . The emergency power system of claim 1 , wherein the reference data is in the form of a look up table for various dimming power levels, or reference waveforms for various dimming power levels, or voltage/current levels thresholds for various dimming power levels.
4 . The emergency power system of claim 1 , wherein the controller generates a PWM control signal to control the phase-cut waveform generator.
5 . The emergency power system of claim 1 , wherein the detection module include a voltage and/or current sensor.
6 . The emergency power system of claim 1 , wherein the controller upon initiation of the emergency power system makes a determination to dynamically update the reference data based upon the monitored voltage and/or current data at full power to the load.
7 . The emergency power system of claim 5 , wherein the controller generates a PWM control signal to adjust the phase-cut waveform generator based upon one or more present conditions that occur while the emergency power system is activated.
8 . The emergency power system of claim 7 , wherein the one or more present conditions include an amount of time the emergency power system ( 100 ) has been activated and/or a remaining runtime of the power source and/or temperature of the power source.
9 . The emergency power system of claim 1 further comprising an interface to allow a user to control/adjust the power level of the load.
10 . A method for dimming an emergency lighting device comprising the steps of:
measuring a load voltage and current of the emergency lighting device;
comparing reference dimming data with the measured load voltage and current;
determining a dimming control signal based upon the comparison;
generating a phase-cut waveform based upon the dimming control signal to reduce the load voltage and current of the emergency lighting device, wherein the phase-cut waveform is generated from a sinusoidal pulse width modulation signal, by modulating an on-time step function to a PWM signal and filtering to generate the phase-cut waveform.