Display device and method for controlling the same

1. A display device comprising:

a light-emitting element which emits light as a current flows through the light-emitting element;

a capacitor;

a drive transistor which passes to the light-emitting element a current dependent on a voltage held at the capacitor;

a voltage detection line;

a switching element which switches between conduction and non-conduction between the voltage detection line and one electrode of the light-emitting element;

a voltage generation circuit configured to supply the voltage detection line with a test voltage for measuring a voltage of the one electrode of the light-emitting element;

a current detection circuit configured to detect a current through the switching element when the switching element is in a conducting state, while the voltage generation circuit is applying the test voltage to the voltage detection line; and

a control circuit configured to update a voltage value of the test voltage, based on a direction of the current detected by the current detection circuit, and cause the voltage generation circuit to output the updated test voltage.

2. The display device according to claim 1 , wherein

the control circuit includes:

a measurement control circuit configured to control when to place the switching element into the conducting state and a non-conducting state; and

a determination circuit configured to decrease the test voltage if the direction of the current detected by the current detection circuit is from the voltage detection line toward the one electrode, and increase the test voltage if the direction of the current detected by the current detection circuit is from the one electrode toward the voltage detection line, and

the determination circuit is configured to determine the test voltage as a measured voltage of the one electrode of the light-emitting element if a rate of change of the test voltage is below or equal to a threshold.

3. The display device according to claim 2 , further comprising:

a selection transistor which switches between conduction and non-conduction between the voltage detection line and the capacitor; and

a switch transistor which is disposed along a path of a current flowing toward the drive transistor and the light-emitting element, and switches between passing the current and not passing the current to the drive transistor and the light-emitting element, wherein

the voltage detection line is a data line which carries a signal voltage to be held at the capacitor, and

in a period for writing the signal voltage to the capacitor, the control circuit is configured to place the selection transistor into the conducting state and write to the capacitor the signal voltage carried by the voltage detection line, and in a period in which the light-emitting element is emitting light, the control circuit is configured to place the switch transistor and the switching element into the conducting state and detect the direction of the current through the switching element.

4. The display device according to claim 3 , further comprising:

pixels disposed in rows and columns and each of which includes the light-emitting element, the drive transistor, and the capacitor, wherein

based on the test voltage determined, by the determination circuit, as the measured voltage of the one electrode, the control circuit is configured to correct, for each of the pixels, the signal voltage which corresponds to the pixel and is output to the data line.

5. A method for controlling a display device which includes a light-emitting element which emits light as a current flows through the light-emitting element, a capacitor, and a drive transistor which passes to the light-emitting element a current dependent on a voltage held at the capacitor, the method comprising:

supplying a voltage detection line with a test voltage for measuring a voltage of the light-emitting element, while the voltage detection line and one electrode of the light-emitting element are in a non-conducting state;

detecting a current through a switching element while the test voltage is being applied to the voltage detection line, after placing into a conducting state the switching element which switches between conduction and non-conduction between the voltage detection line and the one electrode of the light-emitting element; and

updating a voltage value of the test voltage based on a direction of the current detected.

6. The method according to claim 5 , wherein

the supplying, the detecting, and the updating are repeated plural times in listed order,

at kth supplying, a kth test voltage is supplied to the voltage detection line, where k is a natural number greater than or equal to 2,

at kth detecting, a kth current through the switching element is detected, and

at kth updating, a voltage value of the kth test voltage is updated based on the direction of the current through the switching element and a (k+1)th test voltage is generated, and if a voltage difference between the (k+1)th test voltage and the kth test voltage is equal to or below a predetermined value, the (k+1)th test voltage is determined as a measured voltage of the one electrode of the light-emitting element.