Display apparatus using a backlight

1. A display apparatus comprising:

a display panel configured to display an image; and

a backlight unit configured to illuminate the display panel from a back of the display panel, wherein

the backlight unit includes:

N light-emitting diode strings connected in parallel with each other, each of the N light-emitting diode strings includes M light-emitting diodes connected in series, N being an integer of 2 or more and M being an integer of 1 or more;

a power source unit connected in series with the N light-emitting diode strings and configured to generate a voltage;

a drive unit connected in series with the N light-emitting diode strings and the power source unit and configured to supply currents to the N light-emitting diode strings; and

a current regulator configured to regulate current flowing in each of the N light-emitting diode strings,

each of the N light-emitting diode strings illuminates different regions of the display panel, and

the N light-emitting diode strings include a first light-emitting diode string and a second light-emitting diode string, illuminating regions adjacent to each other,

the display apparatus further comprises a light emission controller configured to perform a control so that current is supplied from the drive unit to only the first light-emitting diode string during a first period, that current is supplied from the drive unit to each of the first and second light-emitting diode strings during a second period subsequent to the first period, and that current is supplied from the drive unit to only the second light-emitting diode string during a third period subsequent to the second period.

2. The display apparatus according to claim 1 , wherein the current regulator includes:

a reference voltage generating circuit configured to generate a reference voltage;

a resistor element and current regulating element connected in series with each of the N light-emitting diode string; and

a control circuit configured to control the current regulating element based on the reference voltage generated by the reference voltage generating circuit and a detection voltage detected by the resistor element.

3. The display apparatus according to claim 2 , wherein:

the current regulating element includes a transistor connected in series with each of the N light-emitting diode strings, and

the control circuit includes an amplifier circuit configured to generate a voltage, which controls the transistor, based on the reference voltage and the detection voltage.

4. The display apparatus according to claim 3 , wherein the amplifier circuit includes a differential amplifier circuit.

5. The display apparatus according to claim 2 , wherein:

the current regulating element includes a transistor connected in series with each of the N light-emitting diode strings, and

the control circuit includes a Pulse Width Modulation (PWM) circuit configured to output a PWM signal, which controls the transistor based on the reference voltage and the detection voltage.

6. The display apparatus according to claim 3 , wherein the transistor includes a field-effect transistor.

7. The display apparatus according to claim 1 , wherein

the light emission controller is configured to control, out of the N light-emitting diode strings, K light-emitting diode strings to which the currents are supplied simultaneously from the drive unit,

K is an integer of 2 or more but less than N, and

the current regulator is configured to regulate each current flowing in each of the K light-emitting diode strings.

8. The display apparatus according to claim 7 , wherein:

the light emission controller is configured to perform a control so that the current is supplied from the drive unit to the one or each of the K light-emitting diode strings at a predetermined period, and

the current regulator is configured to regulate each current supplied to the one or each of the K light-emitting diode strings at the predetermined period by the light emission controller.

9. The display apparatus according to claim 1 , wherein

the light emission controller is configured to perform a control so that the current is supplied from the drive unit to each of the N light-emitting diode strings sequentially and one by one, and

the current regulator is configured to regulate each current that is supplied to each of the N light-emitting diode strings sequentially and one by one by the light emission controller.