First, LED lighting driving method
1. Netizen asks: Some of the AC-DC conversions are non-isolated. Is there any problem with this circuit in terms of safety? Now the structure mode of high-power products is metal casing and aluminum-based circuit board. The outer casing is closely connected with the circuit board. The electrical isolation is only realized on the aluminum substrate. How do experts think about this problem?
Experts answer: The first question: There are two ways of isolation and non-isolation in the AC-DC power supply, and there are no problems in the safety regulations. The second question: Yes, this is the point that non-isolated LED power supplies should pay attention to in current applications. A typical LED aluminum substrate can achieve an isolation voltage of 4000V.
2. User happy Chen Xintang asked: For small power LEDs, take power from 220 volt AC mains, what kind of scheme does the power supply adopt?
Expert Answer: The easiest way to take power from AC220V AC mains is to use capacitor current limiting buck, but its disadvantage is that the LED is charged, unsafe, and the power factor is extremely low. The best way is to use a switching power converter to make an isolated constant current power supply. The output current is constant and adjustable. Pay attention to the input power factor when designing. The latter already has a lot of mature circuits, but designers have to work hard on switching power supply technology.
3. Netizen swimming fish ask: In addition to the constant current drive, is the pulse drive of the display screen possible? How to control the pulse drive? How to calculate the drive power?
Expert answer: It is ok. With the constant current source mirror circuit + PWM modulation, the theoretical luminous efficiency can be higher, but in fact, the loss at the ON-OFF switching and the leakage current at the OFF are not so efficient, and it is not suitable for use. High power LED driver . In addition, the laser diode is also used for pulse driving, and it will not be known as a new development direction in the future. Can refer to the following.
4. User Edward Chiang asked: I have customers request dimming, they have PWM signal for dimming in the system, the frequency is 90+/-10Hz, the duty ratio is (1%-80%) +/-5%. When we use this signal, we find that the LED is flashing. How to solve it?
Experts answer: It may be that constant current is not achieved, the current is constantly fluctuating, affecting the brightness, and the feeling is flashing. A suitable constant current source can be formed by adding appropriate feedback resistors to the upper and lower bias and the emitter of the triode. In addition, some constant current driver ICs can meet PWM and analog voltage dimming. If there is flicker in PWM mode, the PWM signal can be integrated and then dimmed by analog method, which should meet the requirements.
The Strain Clamp is primarily used to fix the conductor, ground wire terminals on tension towers of overhead lines, distribution lines and distribution equipments in substations, power plants. It also can fix the guy wire terminals on poles. Moreover, it bears all the tension of conductors, ground wires and lightning conductors. According to its configuration and installation means, the strain clamp can be divided into compression type, bolt type and wedge type. Generally, the compression type includes hydraulic compression type and explosive compression type. Generally, malleable cast iron, steel, and aluminum alloy are used as its materials.
All the ferrous metal should be hot-dip galvanized.
Suspension Clamp,Suspension Clamp With Shackle U,Steel Suspension Clamp,Aluminum Alloy Suspension Clamp
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