METHOD OF TAKING POWER WITH LOW-VOLTAGE BYPASS BY INTEGRATED CIRCUIT FOR AC DIRECT DRIVING LEDS AND THE INTEGRATED CIRCUIT

摘要

The prior integrated circuits (ICs) for AC direct driving LEDs all adopt a method of taking power direct from an AC high voltage to supply power to the ICs, but such ICs have the disadvantages of large power consumption, poor reliability and high cost, etc. The present invention provides a method of taking power with low-voltage bypass for supplying low-voltage power to an IC. The present invention also provides an IC for AC direct driving LEDs, which is applicable to the method of taking power with low-voltage bypass. The IC comprises a voltage stabilizing circuit, a low-voltage electronic switching circuit, an under-voltage control circuit and a comparing and amplifying circuit, and is provided with three pins, i.e., a positive power-supplied terminal, a zero potential reference terminal and a common terminal for current sampling and low-voltage electronic switching. The method of taking power with low-voltage bypass to supply low-voltage power to the IC for AC direct driving LEDs and the IC suitable for applying the method of taking power in accordance with the present invention have the prominent technical effects that the product has the advantages of low power consumption, high efficiency, high reliability, low cost, less pins, less external components and convenient use, etc.

主权项

1. A method of taking power with low-voltage bypass by an integrated circuit (IC) for AC direct driving LEDs,
wherein: the IC for AC direct driving LEDs is provided to have three pins, i.e., a positive power-supplied terminal, a zero potential reference terminal and a common terminal for current sampling and low-voltage electronic switching; and a LEDs-load unit, comprising a group of LEDs, together with a current sampling resistor, is suitable for being provided external to the IC, wherein the LEDs-load unit comprises several or dozens 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, where the negative end is connected to one end of a current sampling resistor Rs, and the other end of the current sampling resistor Rs has a zero potential reference terminal node; wherein the IC comprises: 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 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, wherein the method of taking power by the IC is a method of taking power with low-voltage bypass, 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 maximum peak voltage, which is equal to a transient voltage across the LEDs-load unit and is much lower than a peak voltage of AC, and has a frequency twice of that of AC mains.