Patent ID: 9301355
Filing Date: 2016-03-29
CPC Classification: H05B

Claim Text:
1. A method of taking power with low-voltage bypass by an integrated circuit (IC) for AC direct driving of a LEDs-load unit, wherein: the IC for AC direct driving the LEDs-load unit is provided to have three pins, a positive power-supplied terminal, a zero potential reference terminal and a common terminal for current sampling and low-voltage electronic switching; and the LEDs-load unit, includes a group of LEDs, together with a current sampling resistor, is suitable for being provided external to the IC, wherein the LED group, includes a plurality of LEDs connected in series in the same direction, and has a positive end with a positive power-taken node and a negative end with a common terminal node for current sampling and low-voltage electronic switching, wherein the negative end is connected to one end of the current sampling resistor (Rs), and the other end of the current sampling resistor has a zero potential reference terminal node; wherein the IC includes a voltage stabilizing circuit configured to have a stabilized output voltage of 2.4V; a low-voltage electronic switching circuit configured to function to control switching-in or short-circuiting of the LEDs-load unit according to current intensity of a sampled current; an under-voltage control circuit configured to have a threshold voltage of 3.0V, and be suitable for causing the low-voltage electronic switching circuit to become an open circuit so as to switch in the LEDs-load unit when a transient voltage across the IC obtained by taking power with the low-voltage bypass is lower than the threshold voltage; and a comparing and amplifying circuit configured to have a reference voltage of 1.2V, and be suitable for outputting a control level to control switching of the low-voltage electronic switching circuit upon comparing and amplifying a voltage across the current sampling resistor with the reference voltage, so that the low-voltage electronic switching circuit switches in the LEDs-load unit when the voltage across the current sampling resistor is greater than the reference voltage, and the low-voltage electronic switching circuit short-circuits the LEDs-load unit when the voltage across the current sampling resistor is less than the reference voltage, the method comprising: connecting the positive power-supplied terminal of the IC to the positive power-taken node of the LEDs-load unit; connecting the common terminal of the IC for current sampling and low-voltage electronic switching to the common terminal node, of the LEDs-load unit, for current sampling and low-voltage electronic switching; and connecting the zero potential reference terminal of the IC to the zero potential reference terminal node of the LEDs-load unit, so that a voltage obtained by the method is a unidirectional pulsating low voltage, wherein the unidirectional pulsating low voltage has a peak voltage, which is equal to a maximum transient voltage across the LEDs-load unit, is less than a peak voltage of AC, and has a frequency twice of that of AC mains.