Offline LED driving circuits
First Claim
1. An offline LED driving circuit, comprising:
- a controller, generating a switching signal to switch a transformer for providing an output voltage and an output current at an output terminal of said offline LED driving circuit;
a shunt regulator, coupled to said output terminal of said offline LED driving circuit for providing a feedback signal to said controller; and
a dimming circuit, coupled to said shunt regulator to modulate said feedback signal;
wherein said dimming circuit respectively modulates said feedback signal at a first feedback level and a second feedback level in response to a dimming signal; and
wherein a duty cycle of said switching signal is varied in response to said feedback signal, said output voltage is respectively regulated at a first output level and a second output level in response to said first feedback level and said second feedback level of said feedback signal.
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Abstract
An offline LED driving circuit includes a controller, a shunt regulator, an opto-coupler, and a dimming circuit. The controller generates a switching signal to switch a transformer for providing an output voltage and an output current. The shunt regulator is coupled to an output terminal of the LED driving circuit for providing a feedback signal to the controller via the opto-coupler. The dimming circuit coupled to the shunt regulator modulates the feedback signal at a first feedback level and a second feedback level in response to a dimming signal. The output voltage is respectively regulated at a first output level and a second output level in response to the first feedback level and the second feedback level of the feedback signal. The duty cycle of the switching signal will be varied in a soft-start manner when the feedback signal changes from the second feedback level to the first feedback level.
57 Citations
9 Claims
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1. An offline LED driving circuit, comprising:
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a controller, generating a switching signal to switch a transformer for providing an output voltage and an output current at an output terminal of said offline LED driving circuit; a shunt regulator, coupled to said output terminal of said offline LED driving circuit for providing a feedback signal to said controller; and a dimming circuit, coupled to said shunt regulator to modulate said feedback signal; wherein said dimming circuit respectively modulates said feedback signal at a first feedback level and a second feedback level in response to a dimming signal; and wherein a duty cycle of said switching signal is varied in response to said feedback signal, said output voltage is respectively regulated at a first output level and a second output level in response to said first feedback level and said second feedback level of said feedback signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification