Apparatus and method for driving LED display panel
The present disclosure provides devices, circuits, and methods for driving an LED display panel, so as to ensure the delivery of equal global charge at minimum gray scale. In one example, the circuit of the present disclosure includes a current source, a detection module, and a measurement module. The current source is configured to generate a current signal for the LEDs. The detection module is configured to detect a forward voltage of the LEDs in response to a low current applied to the LEDs. The detection module is further configured to hold the detected forward voltage. The measurement module is configured to measure a time period for an anode voltage of the LEDs to rise to the detected forward voltage in response to a display current applied to the LEDs.
1. A circuit for ensuring full content cycle lighting of a light emitting diode array having a plurality of LEDs, the circuit comprising:
a current source that generates a current signal for the LEDs;
a detection module including an inverter and a multiplexer that detects a forward bias voltage of the LEDs in response to a low current applied to the LEDs, the detection module further holds the detected forward bias voltage; and
a measurement module including a counter and a storage unit that measures a time period for an anode voltage of the LEDs to rise to the detected forward bias voltage in response to a display current applied to the LEDs.
2. The circuit of claim 1 , further comprising:
a comparator; and
a three-terminal switch electrically coupled to an output of the comparator, the three-terminal switch being switchable between a first state and a second state,
wherein the first state forms an electrical conduction between the comparator and the detection module, and the second state forms an electrical conduction between the comparator and the measurement module.
3. The circuit of claim 2 , wherein the multiplexer is configured to transmit voltage signals in increments to the comparator.
4. The circuit of claim 2 , wherein the
counter is configured to count a number of clock cycles while the anode voltage is lower than the detected forward bias voltage, the number of clock cycles corresponding to the measured time period; and
the storage unit is configured to retain the measured time period.
5. The circuit of claim 4 , wherein the counter is a six-bit counter and the storage unit is a static random access memory.
6. The circuit of claim 1 , wherein the low current is about 2.0 mA or less, and the forward bias voltage is about 2.2 Volts.
7. A circuit for driving a light emitting diode (LED) display panel having a plurality of LEDs, the circuit comprising:
an initialization unit; and
an operation unit,
wherein the initialization unit comprises:
a detection module including an inverter and a multiplexer configured to detect a forward bias voltage of the LEDs in response to a low current applied to the LEDs, the detection module further configured to hold the detected forward bias voltage; and
a measurement module including a counter and a storage unit configured to measure a time period for an anode voltage of the LEDs to rise to the detected forward bias voltage in response to a display current applied to the LEDs, and
wherein the operation unit comprises:
a signal generator configured to generate a driving signal;
a compensation module configured to modify the driving signal in accordance with the measured time period; and
a current driver configured to receive the modified driving signal and, in response to the modified driving signal, transmit a driving current to the LEDs, so as to illuminate light with desired brightness.
8. The circuit of claim 7 , wherein the driving signal is a pulse width modulation (PWM) voltage signal.
9. The circuit of claim 8 , wherein the compensation module is configured to extend a width of the PWM voltage signal based on the measured time period.
10. An LED display panel, comprising a plurality of LEDs and the circuit as recited in claim 7 , wherein the circuit supplies the driving current to the LEDs.