IEEE PAR1789 Compliant Low-Cost Permanent Emergency Lamp Based on a Series Resonant Converter in Combination with a Low-Dropout Current Regulator

A permanent emergency lamp is a safety device that is always turned on and remains on for a certain period of time when the electric grid is not present. Increasing efficiency and reducing the components number is vital in this kind of devices. On the other hand, pulse width modulation (PWM) can be used to control the luminous flux of the LEDs that form the lamp. However, IEEE PAR1789 recommendations indicate that is advisable to use a high frequency PWM signal to control the lamp current in order to avoid adverse effects of light flicker. To tackle both issues, this paper proposes a solution based on a series resonant converter in combination with a low-dropout current regulator that operates as a battery charger and as an LED driver at the same time. With this solution, a high-efficiency power converter can be designed, allowing for a adequate activity in both normal and emergency operation modes. Furthermore, adverse health effects of flicker from LEDs can be prevented. The proposed converter uses inexpensive and readily available components, which is a suitable solution for situations where budget is a starting condition.