Context: LEDs have been developed by Seoul Semiconductor that can operate on AC power without the need for a DC converter. For each half-cycle, part of the LED emits light and part is dark, and this is reversed during the next half-cycle. The efficacy of this type of HP-LED is typically 40 lm/W. A large number of LED elements in series may be able to operate directly from line voltage. In 2009, Seoul Semiconductor released a high DC voltage LED, named as 'Acrich MJT', capable of being driven from AC power with a simple controlling circuit. The low-power dissipation of these LEDs affords them more flexibility than the original AC LED design.

Question: What company has developed LEDs that can operate on AC power?
Answer: Seoul Semiconductor

Question: What is the efficacy of an AC powered HP-LED?
Answer: 40 lm/W

Question: When did Seoul Semiconductor release the first high DC voltage LED?
Answer: 2009

Question: What is so good about ac powered HP-LEDs?
Answer: more flexibility

Question: What did Seoul Semiconductor name their ac powered HP-LED?
Answer: Acrich MJT

Question: What company has developed non-LEDs that can operate on AC power?
Answer: Unanswerable

Question: What is the efficacy of an non-AC powered HP-LED?
Answer: Unanswerable

Question:  When did non-Seoul Semiconductor release the first high DC voltage LED?
Answer: Unanswerable

Question:  What is so good about ac powered non-HP-LEDs?
Answer: Unanswerable