Current shaping for dimmable LED
Aspects of the disclosure provide a circuit that includes a detector and a controller. The detector is configured to detect a firing start by a triode for alternating current (TRIAC) in a power supply. The controller is configured to control a switch in connection with a magnetic component in response to the firing start to shape a profile of a current pulled from the power supply to satisfy a latch current requirement and a hold current requirement of the TRIAC.
1. A circuit, comprising:
a detector configured to detect a start of turning on a triode for alternating current (TRIAC) in a power supply; and
a controller configured to control a switch in connection with a magnetic component in response to the start of turning on the TRIAC in the power supply to adjust a switching current flowing through the magnetic component to have at least a first peak current and a second peak current, the adjustment of the switching current flowing through the magnetic component causing a current pulled from the power supply to satisfy a latch current requirement when the switching current is adjusted to have the first peak current and to satisfy a hold current requirement of the TRIAC when the switching current is adjusted to have the second peak current.
2. The circuit of claim 1 , wherein the controller is configured to adjust the switching current to cause the current at a first level to enable enough latch current for the TRIAC at the start of turning on the TRIAC in the power supply.
3. The circuit of claim 1 , wherein the detector is configured to detect the switching current passing through the switch, and the controller is configured to control the switch according to the detected switching current to shape the current pulled from the power supply.
4. The circuit of claim 2 , wherein the controller is configured to adjust the switching current to cause the current at a second level that is lower than the first level to enable enough hold current for the TRIAC after the start of turning on the TRIAC in the power supply.
5. The circuit of claim 3 , wherein the current pulled from the power supply includes the switching current, and a damping current by a damping circuit.
6. The circuit of claim 3 , wherein the controller is configured to control at least one of a rising edge delay for the current to rise to the first level, a rising edge slope for the current to rise to the first level, a duration for the current to above a threshold, and a falling edge slope for the current to fall from the first level to the second level.
7. The circuit of claim 5 , wherein a capacitance of the damping circuit is smaller than a specific value.
8. An apparatus, comprising:
a switch in connection with a magnetic component for transferring energy from an energy source to a load; and
an integrated circuit (IC) chip comprising:
a detector configured to detect a start of turning on a triode for alternating current (TRIAC) in the energy source; and
a controller configured to control the switch in response to the start of turning on the TRIAC in the energy source to adjust a switching current flowing through the magnetic component to have at least a first peak current and a second peak current, the adjustment of the switching current flowing through the magnetic component causing a current pulled from the energy source to satisfy a latch current requirement when the switching current is adjusted to have the first peak current and to satisfy a hold current requirement of the TRIAC when the switching current is adjusted to have the second peak current.
9. The apparatus of claim 8 , wherein the controller is configured to adjust the switching current to cause the current at a first level to enable enough latch current for the TRIAC at the start of turning on the TRIAC in the energy source.
10. The apparatus of claim 8 , wherein the detector is configured to detect the switching current passing through the switch, and the controller is configured to control the switch according to the detected switching current to shape the current pulled from the power supply.
11. The apparatus of claim 8 , further comprising:
a damping circuit configured to pull a damping current in response to the start of turning on the TRIAC in the energy source, and the current pulled from the energy source including the switching current, and the damping current.
12. The apparatus of claim 8 , wherein the apparatus does not include a damping circuit, and the controller is configured to control the switch in response to the start of turning on the TRIAC in the energy source to shape the switching current to satisfy operation requirements of the TRIAC.
13. The apparatus of claim 9 , wherein the controller is configured to adjust the switching current to cause the current at a second level that is lower than the first level to enable enough hold current for the TRIAC after the start of turning on the TRIAC in the energy source.
14. The apparatus of claim 10 , wherein the controller is configured to control at least one of a rising edge delay for the current to rise to the first level, a rising edge slope for the current to rise to the first level, a duration for the current to above a threshold, and a falling edge slope for the current to fall from the first level to the second level.
15. A method, comprising:
detecting a start of turning on a triode for alternating current (TRIAC) in a power supply; and
switching on/off a switch in connection with a magnetic component in response to the start of turning on the TRIAC in the power supply to adjust a switching current flowing through the magnetic component to have at least a first peak current and a second peak current, the adjustment of the switching current flowing through the magnetic component causing a current pulled from the power supply to satisfy a latch current requirement when the switching current is adjusted to have the first peak current and to satisfy a hold current requirement of the TRIAC when the switching current is adjusted to have the second peak current.
16. The method of claim 15 , wherein switching on/off the switch in connection with the magnetic component in response to the start of turning on the TRIAC in the power supply to adjust the switching current flowing through the magnetic component further comprises:
switching on/off the switch to pull the current at a first level to enable enough latch current for the TRIAC at the start of turning on the TRIAC in the power supply.
17. The method of claim 15 , wherein switching on/off the switch in connection with the magnetic component in response to the start of turning on the TRIAC in the power supply to adjust the switching current flowing through the magnetic component further comprises:
switching on/off the switch to pull the current at a second level that is lower than the first level to enable enough hold current for the TRIAC after the start of turning on the TRIAC in the power supply.
18. The method of claim 17 , further comprising:
switching on/off the switch to control at least one of a rising edge delay for the current to rise to the first level, a rising edge slope for the current to rise to the first level, a duration for the current to above a threshold, and a falling edge slope for the current to fall from the first level to the second level.
19. The method of claim 15 , further comprising:
detecting the switching current passing through the switch; and
switching on/off the switch according to the detected switching current to shape the current pulled from the power supply.
20. The method of claim 15 , further comprising:
flowing a damping current by a damping circuit in response to the start of turning on the TRIAC in the power supply to satisfy a latch current requirement for the TRIAC.