Dimming driver circuit and control method thereof

A dimming driver circuit for adjusting brightness of a light emitting diode, the dimming driver circuit comprising:

• a power converting unit comprising an input side, an output side and a switch element, wherein the power converting unit receives an input voltage from the input side, wherein during a switching operation of the switch element, the input voltage is converted into an output voltage, and the output voltage is outputted from the output side;
• an input voltage detection unit electrically connected with the input side for detecting a voltage value of the input voltage and generating a first detecting signal according to a detecting result of the input voltage detection unit;
• an output voltage detection unit electrically connected with the output side for detecting a voltage value of the output voltage and generating a second detecting signal according to a detecting result of the output voltage detection unit;
• a low-side driving unit electrically connected with the switch element for driving the switch element;
• and
• a control unit electrically connected with the low-side driving unit, the input voltage detection unit and the output voltage detection unit, wherein the control unit previously defines an initial control signal composed of plural pulses at a pulse frequency, the control unit receives and processes a dimming signal so as to generate a corresponding dimming current, and the control unit compares the dimming current with a preset current threshold value, wherein if the dimming current is higher than the preset current threshold value, the control unit calculates an on time period of the switch element in a switching cycle according to the first detecting signal, the second detecting signal and the dimming current and defines a first setting according to the on time period, wherein if the dimming current is lower than or equal to the preset current threshold value, the control unit calculates the on time period of the switch element in the switching cycle according to the first detecting signal, the second detecting signal and the preset current threshold value, divides the switching operation of the switch element into plural chopping cycles, calculates a pulse ratio in at least one chopping cycle according to the dimming current and the preset current threshold value, and defines a second setting according to the on time period and the pulse ratio,
• wherein the control unit adjusts the plural pulses of the initial control signal according to the first setting or the second setting, so that a corresponding real control signal is generated to the low-side driving unit, wherein the switching operation of the switch element is controlled by the low-side driving unit according to the real control signal, and an output current corresponding to the dimming signal is generated from the power converting unit to the light emitting diode so as to control the brightness of the light emitting diode.

A dimming driver circuit for adjusting brightness of a light emitting diode, the dimming driver circuit comprising:

• a power converting unit comprising an input side, an output side, a first inductor and at least one switch element, wherein the first inductor is electrically connected with an end of the switch element, and the power converting unit receives an input voltage from the input side, wherein during a switching operation of the at least one switch element, the input voltage is converted into an output voltage, and the output voltage is outputted from the output side;
• an inductor current detecting unit electrically connected with the first inductor, wherein the inductor current detecting unit generates at least one detecting signal according to a result of detecting an inductor current that flows through the first inductor;
• a low-side driving unit electrically connected with the switch element for driving the switch element;
• and
• a control unit electrically connected with the low-side driving unit and the inductor current detecting unit, wherein the control unit previously defines an initial control signal composed of plural pulses at a pulse frequency, the control unit receives and processes a dimming signal so as to generate a corresponding dimming current, and the control unit compares the dimming current with a preset current threshold value, wherein if the dimming current is higher than the preset current threshold value, the control unit controls the switch element to be switched from the off state to the on state when the detecting signal is equal to a first preset value, controls the switch element to be switched from the on state to the off state when the detecting signal is equal to a second preset value, and defines a first setting, wherein if the dimming current is lower than or equal to the preset current threshold value, the control unit controls the switch element to be switched from the off state to the on state when the detecting signal is equal to the first preset value, controls the switch element to be switched from the on state to the off state when the detecting signal is equal to two times of the preset current threshold value, divides the switching operation of the switch element into plural chopping cycles, calculates a pulse ratio in at least one chopping cycle according to the dimming current and the preset current threshold value, and defines a second setting according to the first preset value, two times of the preset current threshold value and the pulse ratio,
• wherein the control unit adjusts the plural pulses of the initial control signal according to the first setting or the second setting, so that a corresponding real control signal is generated to the low-side driving unit, wherein the switching operation of the switch element is controlled by the low-side driving unit according to the real control signal, and an output current corresponding to the dimming signal is generated from the power converting unit to the light emitting diode so as to control the brightness of the light emitting diode.