Time control circuit for backlight inverter
View Patent ↗In a time control circuit, a capacitor is connected between a connecting pin and a ground. A first current source supplies a first current to the connecting pin. A first comparator element has a non-inverse terminal connected to a voltage of the capacitor and a pre-set first reference voltage, and controls the initial startup time. A second comparator element has an inverse terminal connected to the voltage of the capacitor and a pre-set second reference voltage, and controls the soft start time. Further, a current bypass controller includes a current bypass path between the connecting pin and the ground, which connects the current bypass path after the soft start time and blocks it at an input of a protective signal. Additionally, a third comparator element has an inverse terminal connected to the voltage of the capacitor and a pre-set third reference voltage, and controls the shutdown time.
1. A time control circuit for a backlight inverter comprising:
a first current source connected between a connecting pin and a power terminal, for supplying a pre-set first current;
a second current source for selectively supplying a pre-set second current to the connecting pin;
a capacitor connected between the connecting pin and a ground, wherein the capacitor is configured to be charged by either: the first current source, or the first current source and the second current source;
a first comparator element for comparing a voltage of the capacitor at the connecting pin and a pre-set first reference voltage to control an initial startup time;
a second comparator element for comparing the voltage of the capacitor at the connecting pin and a pre-set second reference voltage to control a soft start time;
a current bypass controller including a current bypass path formed between the connecting pin and the ground, for connecting the current bypass path after the soft start time and blocking the current bypass path at an input of a protective signal; and
a third comparator element for comparing the voltage of the capacitor at the connecting pin and a pre-set third reference voltage to control a shutdown time;
wherein
the first comparator element and the second comparator element are configured to output a high voltage level at power-on,
a first period, during which the output of the first comparator element is transited from the high level to a low level, corresponds to the initial startup time, and
a second period, during which the output of the second comparator element is transited from the high level to the low level, corresponds to the soft start time.
2. The time control circuit for the backlight inverter according to claim 1 , further comprising a constant voltage element connected to the connecting pin, for supplying a pre-set constant voltage.
3. The time control circuit for the backlight inverter according to claim 1 , further comprising:
a first switch connected between the second current source and the connecting pin and configured to disconnect the second current source from the connecting pin after the soft start time determined by the second comparator element;
wherein the second current source has one end connected to the power terminal.
4. The time control circuit for the backlight inverter according to claim 1 , wherein the second reference voltage is set higher than the first reference voltage and lower than the third reference voltage.
5. The time control circuit for the backlight inverter according to claim 2 , wherein the constant voltage of the constant voltage element is set higher than the third reference voltage.
6. The time control circuit for the backlight inverter according to claim 1 , wherein the first current of the first current source is set lower than the second current of the second current source.
7. The time control circuit for the backlight inverter according to claim 1 , wherein the first comparator element is disabled after the soft start time determined by the second comparator element.
8. The time control circuit for the backlight inverter according to claim 1 , wherein the second comparator element comprises a comparator for comparing the voltage of the capacitor and the second reference voltage, and a first latch for outputting an output signal from the comparator, the first latch being reset at power-off.
9. The time control circuit for the backlight inverter according to claim 1 , wherein the third comparator element comprises a comparator for comparing the voltage of the capacitor and the third reference voltage, and a second latch for outputting an output signal from the comparator, the second latch being reset at power-off.
10. The time control circuit for the backlight inverter according to claim 1 , wherein the bypass controller comprises a second switch connected between the connecting pin and the ground, and a logical operation element for logically summing up a first protective signal and a second protective signal to provide a switching signal to the second switch, the logical operation element being enabled after the soft start time determined by the second comparator element.