Method of soft-starting a switching power supply having time-based pulse triggering control
View Patent ↗A method of operating a power controller that converts a line voltage to an RMS load voltage includes a soft start in which a conduction angle or duty cycle is gradually increased to a steady state value that defines the RMS load voltage. The controller has a circuit with a time-based signal source that triggers conduction independently of line voltage magnitude and a transistor switch whose gate receives signals from the time-based signal source to trigger the circuit. When starting the power controller, a microcontroller increases a rate and/or duration of the signals from the time-based signal source in successive cycles of the load voltage to provide the soft start. The power controller may be in a voltage conversion circuit that converts a line voltage at a lamp terminal to the RMS load voltage usable by a light emitting element of the lamp.
1. A method of operating a power controller that converts a line voltage to an RMS load voltage and that has a circuit that clips or modulates a load voltage to provide the RMS load voltage, the circuit including a time-based signal source that triggers conduction in the circuit independently of line voltage magnitude and a transistor switch whose gate receives signals from the time-based signal source to trigger the circuit, the method comprising the steps of:
when starting the power controller, increasing one of a rate and a duration of the signals from the time-based signal source sent to the gate of the transistor switch, the one of the rate and duration increasing in plural steps from a first value to a steady state value that defines the RMS load voltage; and
during subsequent operation of the power controller, sending the signals from the time-based signal source at constant time intervals to the gate of the transistor switch to cause the power controller to provide the RMS load voltage independently of line voltage magnitude.
2. The method of claim 1 , wherein the circuit clips the load voltage immediately following each polarity change of the load voltage and wherein the duration of the signals is increased when starting the power controller to increase a conduction angle of the circuit.
3. The method of claim 1 , wherein the circuit clips the load voltage immediately before each polarity change of the load voltage and wherein the duration of the signals is increased when starting the power controller to increase a conduction angle of the circuit.
4. The method of claim 1 , wherein the time-based signal source sends the signals to the gate of the transistor switch to cause the transistor switch to be on during time periods that span from before to after polarity changes of the load voltage and to be off between the time periods and wherein the duration of the time periods increases when starting the power controller to increase a conduction angle of the circuit.
5. The method of claim 1 , wherein at least one of the frequency and the duration of the signals is increased when starting the power controller to increase a duty cycle of the circuit to the steady state value and wherein the circuit pulse width modulates the load voltage after starting the power controller.
6. The method of claim 1 , further comprising the step of giving the signals a positive polarity at the gate of the transistor switch.
7. The method of claim 1 , further comprising the step of connecting the power controller between a terminal of a lamp and a light emitting element of the lamp.