DC-DC converter having protective function of over-voltage and over-current and led driving circuit using the same

1. A DC-DC converter for adjusting a width of a switching pulse-outputted from a Pulse Width Modulation (PWM) controller to control on/off durations of a switch, thereby providing a controlled level of voltage to a load, comprising:

a microcontroller for detecting a voltage at an end of the load, and if the detected voltage is greater than a predetermined reference voltage, generating an alarm signal;

a digital-analogue converter for receiving the alarm signal to output a voltage of 0V; and

an analogue dimmer for receiving the voltage of 0V from the digital-analogue converter to generate a control signal that changes an ‘on’ duration of the switching pulse outputted from the PWM controller to 0 and providing the control signal to the PWM controller.

2. The DC-DC converter according to claim 1 , wherein if the DC-DC converter is a buck DC-DC converter, the microcontroller detects a voltage at a current output end of the load.

3. The DC-DC converter according to claim 1 , wherein if the DC-DC converter is a boost DC-DC converter, the microcontroller detects a voltage at a current input end of the load.

4. The DC-DC converter according to claim 1 , wherein the load comprises an LED array having an LED or at least two LEDs connected in series.

5. An LED driving circuit comprising:

a first DC-DC converter for adjusting a width of a switching pulse outputted from a first Pulse Width Modulation (PWM) controller to control on/off durations of a first switch, thereby providing a predetermined level of voltage to a red LED array having at least two red LEDs connected in series;

a second DC-DC converter for adjusting a width of a switching pulse outputted from a second PWM controller to control on/off durations of a second switch, thereby providing a predetermined level of voltage to a blue LED array having at least two blue LEDs connected in series;

a third DC-DC converter for adjusting a width of a switching pulse outputted from a third PWM controller to control on/off durations of a third switch, thereby providing a predetermined level of voltage to a green LED array having at least two green LEDs connected in series;

a microcontroller for detecting a voltage from each of the red, blue, and green LED arrays, and if the detected voltage is greater than a predetermined voltage, generating an alarm signal indicating abnormality in a corresponding LED array;

a digital-analogue converter for receiving the alarm signal and outputting a voltage of 0V for a corresponding DC-DC converter with the abnormality; and

first to third analogue dimmers each connected to each of the first to third PWM controllers, the analogue dimmers adapted to generate a control signal that changes the ‘on’ duration of the switching pulse outputted from the PWM controller to 0 and provide the control signal to the connected PWM controllers if the voltage of 0V is received from the digital-analogue converter.

6. The DC-DC converter according to claim 5 , wherein if the first to third DC-DC converters are buck DC-DC converters, the microcontroller detects voltages from cathodes of the red, blue and green LED arrays.

7. The DC-DC converter according to claim 5 , wherein if the first to third DC-DC converters are boost DC-DC converters, the microcontroller detects voltages from anodes of the red, blue and green LED arrays.