Load control device for a light-emitting diode light source having different operating modes

An LED driver for controlling an intensity of an LED light source, the LED driver comprising:

• an LED drive circuit configured to control a magnitude of a load current conducted through the LED light source to control an amount of power delivered to the LED light source, the LED drive circuit comprising an inverter circuit characterized by a burst duty cycle;
• and
• a control circuit coupled to the LED drive circuit and configured to control an average magnitude of the load current, the control circuit configured to control the inverter circuit to operate in active state periods during which the inverter circuit is active and inactive state periods during which the inverter circuit is inactive, the control circuit further configured to operate in at least a low-end mode, an intermediate mode, and a normal mode, wherein:
• during the low-end mode, the control circuit is configured to keep a length of the active state periods constant and adjust a length of the inactive state periods in order to adjust the burst duty cycle and the average magnitude of the load current,
• during the intermediate mode, the control circuit is configured to keep the length of the inactive state periods constant and adjust the length of the active state periods in order to adjust the burst duty cycle and the average magnitude of the load current, and
• during the normal mode, the control circuit is configured to regulate the average magnitude of the load current by holding the burst duty cycle constant and adjusting a target load current conducted through the LED light source.

An LED driver for controlling an intensity of an LED light source, the LED driver comprising:

• an LED drive circuit configured to control a magnitude of a load current conducted through the LED light source in order to achieve a target intensity of the LED light source, the LED drive circuit comprising an inverter circuit characterized by a burst duty cycle;
• and
• a control circuit coupled to the LED drive circuit and configured to control an average magnitude of the load current, the control circuit configured to control the inverter circuit to operate in active state periods during which the inverter circuit is active and inactive state periods during which the inverter circuit is inactive, the control circuit further configured to operate in a burst mode and a normal mode,
• wherein, during the normal mode, the control circuit is configured to regulate the average magnitude of the load current by holding the burst duty cycle constant and adjusting a target load current conducted through the LED light source, and
• wherein, during the burst mode, the control circuit is configured to adjust the burst duty cycle and the average magnitude of the load current by keeping a length of the active state periods constant and adjusting a length of the inactive state periods if the target intensity of the LED light source is within a first intensity range, and by keeping the length of the inactive state periods constant and adjusting the length of the active state periods if the target intensity of the LED light source is within a second intensity range.