There is a problem with LED dimmers
At the time of the thyristor, the AC market voltage is applied almost simultaneously to the LC input filter for the LED lamp. The voltage step that is applied to the inductance causes the oscillation. If the dimmer current is below the thyristor current during the oscillation, the thyristor will stop conducting. The thyristor triggers the circuit to charge and releads the light dimmer. This irregular multi-silicon controlled restart can make LED lights produce unwanted audio noise and blinking. Designing a simpler EMI filter helps reduce this unnecessary oscillation. To achieve a successful adjustment, input EMI filter inductors and capacitors must also be as small as possible. Oscillation of the worst condition characterized by the phase Angle of 90 degrees (at this point, the input voltage peak sine wave, suddenly the input applied to the LED lamp), and for high input voltage (at this time, the forward current of dimmer to lowest level). Premature closing occurs when the depth of light is required (such as the phase Angle near 180 degrees) and the low input voltage is required. To reliably lower the luminosity, the thyristor must be monotonic and stay at the point where AC voltage is almost zero. For thyristor, the maintenance current required to maintain the conductance is usually between 8 and 40 mA. Incandescent lamp is easier to maintain the current size, but for the power consumption to only 10% of the equivalent of incandescent lamp LED lights, the current can be reduced to maintain under the current thyristor, thyristor premature shutoff. This will cause scintillation and/or limit tunable.
To achieve the dimming, the LED lamp must be able to analyze the variable phase Angle output of the thyristor controller to make a one-way adjustment to the constant flow to the LED. It is difficult to do this while maintaining the tuner's work, often resulting in poor performance. Problems can be shown to be slow, blinking, unevenly lit, or flashing when adjusting for brightness. In addition, there is a mismatch between the components and the audio noise that the LED lights don't need. These adverse events are usually caused by the combination of false triggers or premature closing of the thyristor and LED current control. The root cause of the false trigger is a current oscillation when the thyristor is conducted.
Leds used to replace standard incandescent bulbs usually contain an LED array to ensure a uniform illumination. These leds are connected in tandem. The brightness of each LED is determined by its current, and the positive voltage of the LED is about 3.4 volts, usually between 2.8 and 4.2 volts. Leds should be driven by a constant current supply, which must be tightly controlled to ensure a high degree of matching between adjacent LED lights.
There are many other challenges in designing LED lighting. Energy star solid-state lighting specification requires that the commercial and industrial application must meet the minimum power factor of 0.9, lighting products must meet the efficiency, output current tolerance and EMI are strict requirements, and the power supply must also occurs in the LED load under the condition of short circuit or open circuit to make the security response.
