LED dimmer circuit and method
An LED dimmer can be connected between a basic LED driver and an LED arrangement. The dimmer is able at least to receive a constant current from a constant current LED driver, and it then uses a boost converter to provide voltage boosting dependent on a required dimming level.
1. An LED dimmer for connection between an LED driver and an LED arrangement, comprising:
an input for receiving a constant current and a constant voltage from the LED driver, wherein an inductor is displaced between the input and an anode of a first diode component;
a means for determining if the LED dimmer is receiving a constant voltage or a constant current, the means comprising a sensor resistor connected in series with the LED arrangement;
a converter circuit providing voltage conversion dependent on a required dimming level, wherein the converter circuit comprises at least one of a boost converter and a buck converter;
a controller for controlling the LED dimmer by controlling the converter circuit in dependence on whether the LED dimmer is receiving a constant voltage or a constant current;
a first output for providing a signal from the converter circuit to a first terminal of the LED arrangement, wherein a cathode of the first diode component is connected to the first output;
a control switch connected between the anode of the first diode component and a current return path to the LED driver;
a second switch in series with the sensor resistor; and
a second diode component connected between the input and a second output for connection to a second terminal of the LED arrangement.
2. An LED dimmer as claimed in claim 1 , wherein the controller is adapted to operate the converter circuit in a first mode when a constant current input is detected, and to operate the converter circuit in a second mode when a constant voltage input below the operating voltage of the LED arrangement is detected.
3. An LED dimmer as claimed in claim 1 , wherein the controller is controlling the control switch.
4. An LED dimmer as claimed in claim 3 , wherein the control switch comprises a transistor.
5. An LED dimmer as claimed in claim 1 , further comprising a capacitor connected between the first output and the current return path.
6. An LED driver arrangement, comprising:
a constant current or constant voltage LED driver; and
an LED dimmer as claimed in claim 1 connected to the output of the LED driver for providing a drive signal to the LED arrangement.
7. A lighting arrangement, comprising:
the LED driver arrangement as claimed in claim 6 ; and
the LED arrangement.
8. A lighting arrangement as claimed in claim 7 , wherein the LED dimmer is provided on a circuit board of the LED arrangement.
9. A driving method for driving an LED arrangement, comprising:
receiving an input signal at an input from an LED driver on an input of a LED dimmer, wherein an inductor is displaced between the input and an anode of a first diode component;
determining, using at least a sensor resistor connected in series with the LED arrangement, if the received input signal is a constant voltage or a constant current;
providing voltage conversion dependent on a required dimming level using a converter circuit, wherein the converter circuit comprises at least one of a boost converter and a buck converter;
controlling the LED dimmer by controlling the converter circuit in dependence on whether the LED dimmer is receiving a constant voltage or a constant current; and
providing a signal from the converter circuit to a first terminal of the LED arrangement, wherein a cathode of the first diode component is connected to the first output, and wherein a control switch is connected between the anode of the first diode component and a current return path to the LED driver, a second switch is in series with the sensor resistor, and a second diode component is connected between the input and a second output for connection to a second terminal of the LED arrangement.
10. The driving method of claim 9 , wherein the converter circuit comprises a boost converter, the method comprising:
if the received input signal is a constant current, providing the boost converter operated in a first mode;
if the received input signal is a constant voltage below the operating voltage of the LED arrangement, providing voltage boosting dependent on the required dimming level using a boost converter operated in a second mode and providing a signal from the boost converter to a first terminal of the LED arrangement.
11. A method as claimed in claim 10 , wherein the converter circuit further comprises a buck converter, the method further comprising, if the received input signal is a constant voltage above the operating voltage of the LED arrangement, providing voltage bucking dependent on the required dimming level using the buck converter and providing a signal from the buck converter to a first terminal of the LED arrangement.