LED drive circuit
View Patent ↗An LED drive circuit that can increase the amount of light with a compact structure. This circuit includes series-connected LEDs, first and second DC power supplies connected in series so as to apply a forward bias to the LEDs, a coil that is series-connected with the LEDs and can accumulate energy from current generated by the DC power supplies, a rectifying element whose cathode is connected between the DC power supplies, a transfer switching element connected to the anode of the rectifying element, and a control apparatus for controlling the transfer switching element. A first closed circuit is formed by the LEDs, the DC power supplies, and the coil when the transfer switching element is switched on by the control apparatus, and a second closed circuit is formed by the LEDs, the second DC power supply, the coil, and the rectifying element when the transfer switching element is switched off.
1. An LED drive circuit comprising:
a plurality of LEDs that are connected in series;
a first DC power supply that is connected in series to the plurality of LEDs so as to apply a forward bias to the plurality of LEDs;
a second DC power supply that is connected in series to the first DC power supply and is connected to the plurality of LEDs so as to apply a forward bias to the plurality of LEDs;
a coil that is connected in series with the plurality of LEDs and can accumulate energy from current generated by the first DC power supply and the second DC power supply;
a rectifying element whose cathode is connected between the first DC power supply and the second DC power supply, wherein the rectifying element is configured to allow current to flow from the plurality of LEDs to between the first DC power supply and the second DC power supply;
a transfer switching element that is connected to an anode of the rectifying element, wherein the transfer switching element is configured to connect the plurality of LEDs and the first power supply when the transfer switching element is switched on and is configured to allow current to flow from the plurality of LEDs to the rectifying element when the transfer switching element is switched off; and
a control unit for controlling the transfer switching element,
wherein a first closed circuit is formed by the plurality of LEDs, the first DC power supply, the second DC power supply, and the coil when the transfer switching element is switched on under control of the control unit, and a second closed circuit is formed by the plurality of LEDs, the second DC power supply, the coil, and the rectifying element when the transfer switching element is switched off under control of the control apparatus.
2. The LED drive circuit according to claim 1 , wherein a voltage of the second DC power supply is lower than a required voltage of the second closed circuit, and a sum of a voltage of the first DC power supply and the voltage of the second DC power supply is greater than a required voltage of the first closed circuit.
3. The LED drive circuit according to claim 1 , further comprising:
a voltage sensing element for sensing a voltage drop in the plurality of LEDs; and
a cut-off switching element for cutting off the first closed circuit and the second closed circuit,
wherein the control apparatus controls the on/off state of the cut-off switching element based on the voltage sensing performed by the voltage sensing element.
4. The LED drive circuit according to any of claims 1 to 3 , wherein the plurality of LEDs are each an ultraviolet LED, and the LED drive circuit is disposed in an ultraviolet irradiation apparatus.