LED driver circuit with over-current protection during a short circuit condition

An LED driver circuit comprising:

• an LED current restriction circuit configured to restrict a current flow into the LED, the current restriction circuit further comprising a first switching element coupled in series with the LED;
• a power converter further comprising a second switching element, the power converter configured to receive an input signal from a power source and to control a current output for powering an LED using the second switching element;
• a voltage sensor configured to detect a voltage across the LED;
• a short circuit response circuit configured to control the LED current restriction circuit to restrict current flow to the LED dependent on the voltage detected by the voltage sensor being equal to or below a predetermined threshold value;
• wherein the short circuit response circuit is configured to control the LED current restriction circuit to restrict current flow to the LED dependent on the voltage detected by the voltage sensor being equal to or below a first predetermined threshold value, or above a second predetermined threshold value;
• and
• the short circuit response circuit further comprises
• a first comparator having inputs associated with the voltage detected by the voltage sensor and the first predetermined threshold value, the comparator further having an output coupled to a first input of an AND circuit, and
• a second comparator having inputs associated with the voltage detected by the voltage sensor and the second predetermined threshold value, the comparator further having an output coupled to a second input of the AND circuit,
• wherein an output of the AND circuit is further coupled to the LED restriction circuit.

An LED driver circuit for powering one or more LEDs connected in series, the driver circuit comprising:

• a first switching element coupled in series with the one or more LEDs and configured to switch between a first state where current flows through the LEDs and a second state where current is restricted from flowing through the LEDs;
• a voltage sensor coupled in parallel with the first switching element and the one or more LEDs;
• a current sensor coupled in series with the first switching element and the one or more LEDs;
• a power converter further comprising a second switching element, the power converter configured to receive an input signal from a power source;
• a switch controller coupled to receive a voltage detected by the voltage sensor and to receive a current detected by the current sensor, the switch controller configured to control the switch state of the second switching element and control an output signal from the power converter based on the detected signals;
• a short circuit response circuit configured to control the first switching element to restrict current flow to the one or more LEDs dependent on the voltage detected by the voltage sensor being equal to or below a predetermined threshold value;
• wherein the short circuit response circuit is configured to control the first switching element to restrict current flow to the one or more LEDs dependent on the voltage detected by the voltage sensor being both of equal to or below the predetermined threshold value, and decreasing in value;
• and
• wherein the short circuit response circuit is further configured to continue controlling the first switching element to restrict current flow to the one or more LEDs even if a current is made to flow again from the power source to the LED after observing a short circuit of the LED.