Light emitting diode driving circuit
A LED driving circuit includes a bridge rectifier, a high-bias-voltage diode, a balancing capacitor, a driving chip, and a switch. The bridge rectifier receives external AC power and outputs a full-wave or half-wave AC power. One terminal of the high-bias-voltage diode and one terminal of the balancing capacitor are electrically coupled to a balancing node. The other terminals of the high-bias-voltage diode and the balancing capacitor are electrically coupled to the bridge rectifier and grounded respectively. The driving chip receives operating power from the balancing node, and outputs driving signals to operate the switch, so as to drive an LED. Through the arrangement of the forward bias voltage direction of the high-bias-voltage diode, the balancing capacitor is only discharged to the driving chip. Therefore, the capacitance value and the volume of the balancing capacitor, the space occupied by the driving circuit, and the cost of the driving circuit are reduced.
1. A light emitting diode (LED) driving circuit, for receiving external AC power from an AC power source, converting the external AC power, and outputting a driving AC power to at least one LED, the LED driving circuit comprising:
a bridge rectifier, for receiving said external AC power and outputting said driving AC power, and the bridge rectifier comprising:
two rectifying input terminals, electrically coupled to the AC power source;
a rectifying output terminal, for outputting the driving AC power, and one terminal of the LED being electrically coupled to the rectifying output terminal; and
a rectifying ground terminal, for being electrically grounded;
a high-bias-voltage diode, having one terminal electrically coupled to a balancing node and another terminal electrically coupled to the rectifying output terminal, and a forward bias direction of the high-bias-voltage diode being directed from the rectifying output terminal towards the balancing node;
a balancing capacitor, having one terminal electrically coupled to the balancing node and another terminal being grounded;
a driving chip, receiving operating power from the balancing node and outputting a driving signal; and
a switch, having a first terminal point being electrically grounded and a second terminal point, receiving the driving signal to be set to on or set to off, and the other terminal of the LED being electrically coupled to the second terminal point.
2. The LED driving circuit as claimed in claim 1 , wherein the driving chip at least comprises:
a receive pin, electrically coupled to the balancing node to receive the operating power;
a transmit pin, electrically coupled to the switch to output the driving signal for setting the switch; and
at least one ground pin, grounded to obtain a zero potential reference.
3. The LED driving circuit as claimed in claim 1 , wherein the first terminal point is electrically grounded through a voltage dropping resistor.
4. The LED driving circuit as claimed in claim 3 , wherein the driving chip comprises a feedback pin electrically coupled to the first terminal point for detecting a potential of the first terminal point, so as to determine whether the switch is set to on or set to off.
5. The LED driving circuit as claimed in claim 4 , wherein the feedback pin is electrically coupled to the first terminal point through an adjusting resistor.
6. The LED driving circuit as claimed in claim 1 , further comprising a load circuit having:
two load input terminals, one being electrically coupled to the rectifying output terminal and the other being electrically coupled to the second terminal point of the switch;
two load output terminals, electrically coupled to the LED; and
an energy storage capacitor and a rectifier diode, connected to each other in parallel, and two terminals of the energy storage capacitor and two terminals of the rectifier diode being electrically coupled to the two load input terminals, and a forward bias direction of the rectifier diode being directed away from the switch.
7. The LED driving circuit as claimed in claim 6 , further comprising an energy storage inductor with one terminal electrically coupled to the load input terminal and the other electrically coupled to the energy storage capacitor.
8. The LED driving circuit as claimed in claim 1 , wherein the driving AC power is a full-wave AC power or half-wave AC power.