Patent Application
20130043793
1. Field of the Invention
The invention relates to a lightning-proof AC LED driving device and, in particular, to a lightning-proof AC LED driving device that uses the lightning detection breaker to prevent lightning strikes.
2. Description of Related Art
A general power line may be as short as hundreds of meters or as long as several kilometers. Under a lightning strike, the power line will produce a high voltage of up to several thousand volts. If such a high voltage goes through the power line and enters buildings, it is easy to damage electrical appliances connected to the power line.
A conventional arrester uses two discharge ends and an air gap as protection. The two discharge ends connect respectively to a power line and a ground point. When the lightning produces a voltage greater than an air-gap discharge voltage, there is a discharge from one discharge end through the air gap to the other discharge end connected to the ground point. The above-mentioned arrester can also use an isolation transformer for lightning isolation. The high voltage due to lightning is isolated on the primary side of the isolation transformer, preventing the circuit on the secondary side of the isolation transformer from being damaged by the lightning occurring on the primary side.
When the arrester is struck by lightning, the high voltage through the arrester will produce heat. Moreover, the isolation transformer is bulky. When the isolation transformer is connected to AC power, the arrester produces heat due to the impedance of its internal circuit. For LED lamps used in a limited space, heat dissipation and the size problems all pose a challenge in circuit designs and circuit board layouts.
As described above, the conventional arrester has problems of large size and poor heat dissipation. Therefore, when the LED lamp is equipped with an arrester, there is a lot of difficulty in the circuit design thereof.
An objective of the invention is to provide a lightning-proof AC LED driving device without using a transformer.
To achieve the above-mentioned objective, the lightning-proof LED driving device includes:
a rectifier for converting an AC sine wave power supply to a DC power and outputting the DC power through an anode and a cathode;
an AC LED driver circuit with the rectifier connected to a base and electrically connected to the anode and cathode of the rectifier; and
a lightning detection breaker connected in series between the rectifier and the AC LED driver circuit and electrically connected to the base to determine the potentials at the anode and cathode of the rectifier, wherein the lightning detection breaker automatically conducts when the potentials are different, and disconnects the AC LED driver circuit from the rectifier when the potentials thereof are the same.
When a high voltage caused from the lightning strike enters the rectifier, the anode and cathode of the rectifier are equipotential, leaving the lightning detection breaker connected between the rectifier and the AC LED driver circuit automatically become an open-short circuit, thereby interrupting the path through which the high voltage may pass to the AC LED driver circuit. The AC LED driver circuit is thus protected from the lightning strike.
With reference to
With reference to
The rectifier 10 converts AC sine wave power into DC power. The cathode of the rectifier 10 is connected to a ground point. In this embodiment, the rectifier 10 is a full-wave rectifier.
The AC LED driver circuit 30 has two power supply terminals connected to the anode and the cathode of the rectifier 10, respectively. In this embodiment, the AC LED driver circuit 30 includes a controller 31, a voltage-controlled transistor 32, a current detector 33 and an LED module 34. The controller 31 according to the signal of the current detector 33 turns on or off the voltage-controlled transistor 32. This controls the current of the LED module 34 to be a constant current, stabilizing the illumination of the LED module 34.
One end of the detection resistor 24 is connected to the cathode of the rectifier 10, and the other end is connected to the base 35 of the AC LED driver circuit 30, i.e. the ground.
The lightning detector 23 has two detection terminals and an output terminal. The two detection terminals are connected in series between the detection resistor 24 and the base 35 of the AC LED driver circuit 30. With reference to
The switch 26 has two contacts and a control end by which the two contacts are controlled to open or close. In this embodiment, the switch 26 is a voltage-controlled transistor having a source terminal, a gate terminal and a drain terminal. One of the contacts is the source terminal, connected in series with a resistor 22a to the base 35. The other contact is the drain terminal, connected in series with a resistor 22b and a diode 21 and then to the anode of the rectifier 10. The control end is the gate terminal, connected to the output of the lightning detector 23. The lightning detector 23 controls the contacts of the voltage-controlled transistor to open or close. That is, when both ends of the resistor 28 produce a voltage, the two contacts of the voltage-controlled transistor are connected, i.e. the switch 26 is turned on.
The first differential pressure switch unit 25a has two control ends and two contacts. The first control ends is connected to the cathode of the rectifier 10 and one end of the detection resistor 24. The second control end is connected to the switch 26. The two contacts of the first differential pressure switch unit 25a are respectively connected to the anode of the rectifier 10 and one of the power supply sides of the AC LED driver circuit 30. When the two control ends of the first differential pressure switch unit 25a have different potentials, the two contacts of the first differential pressure switch unit 25a are automatically short-circuited. When the two control ends of the first differential pressure switch unit 25 have the same potential, the two contacts automatically disconnect.
The second differential pressure switch unit 25b has two control ends and two contacts. The first control ends is connected to the cathode of the rectifier 10 and one end of the detection resistor 24. The second control end is connected to the switch 26. The two contacts are respectively connected to the cathode of the rectifier 10 and the other power supply terminal of the AC LED driver circuit 30. When the two control ends have different potentials, the two contacts are automatically short-circuited. When the two control ends have the same potential, the two contacts automatically disconnect.
When normal AC power enters the rectifier 10, the cathode of the rectifier 10 is connected via the detection resistor 24 to the base 35. Since the base 35 and the cathode of the rectifier 10 are equipotential at the ground point, the lightning detector 23 is not triggered, keeping the switch 26 open. The two control ends of the first differential pressure switch unit 25a and the second differential pressure switch unit 25a are connected respectively to the anode and cathode of the rectifier 10. When the two control ends have different potentials, the two differential pressure switch units 25a, 25b are closed. The DC power from the DC rectifier 10 is passed to the two power supply terminals of the AC LED driver circuit 30, so that the LED module 34 therein can illuminate stably.
With reference to
With reference to
In summary, the invention can prevent lightning strikes from damaging the AC LED driver circuit without using a large transformer. Whether the AC LED driver circuit is functioning, the high voltage produced by the lightning strike can always be prevented from entering the AC LED driver circuit, achieving the lightning-proof function.
| Number | Date | Country | Kind |
|---|---|---|---|
| 100129488 | Aug 2011 | TW | national |
