Multi-mode flyback control for a switching power converter
In at least one embodiment, an electronic system and method includes a controller to control a switching power converter in at least two different modes of operation depending on whether the controller detects a dimmer or not and/or whether a load requests more power than either of the two operational modes can provide. In at least one embodiment, the controller detects whether a dimmer is phase cutting an input voltage to a switching power converter. The controller operates the switching power converter in a first mode if the dimmer is detected, and the controller operates the switching power converter in a second mode if the dimmer is not detected. The controller also transitions between operating the switching power converter in the first mode and the second mode if a status of detection of the dimmer changes.
1. An method comprising:
detecting whether a dimmer is phase cutting an input voltage to a switching power converter;
operating the switching power converter in a first mode if the dimmer is detected;
operating the switching power converter in a second mode if phase cutting of the input voltage is not detected;
transitioning between operating the switching power converter in the first mode and the second mode if a status of a detection of the dimmer changes; and
operating the switching power converter in both the first and second modes to meet a power demand of a load coupled to the switching power converter, wherein operating the switching power converter in both the first and second modes to meet power a power demand of a load coupled to the switching power converter comprises:
setting an average input current target value for an input current to the switching power converter for operation of the switching power converter in the first mode, wherein the average input current target is insufficient to allow the switching power converter to provide a sufficient charge to meet a charge demand by a load coupled to the switching power converter; and
operating the switching power converter in the second mode to allow the switching power converter to provide the sufficient charge to meet the charge demand by the load coupled to the switching power converter.
2. The method of claim 1 further comprising:
generating a control signal to control a switch to control a current in the switching power converter;
wherein operating the switching power converter in the first mode if the dimmer is detected comprises operating the switching power converter to draw a substantially constant average input current to the switching power converter during an active time of the control signal.
3. The method of claim 1 wherein operating the switching power converter in the second mode if the dimmer is not detected comprises operating the switching power converter to draw an input current to the switching power converter to provide a power factor correction.
4. The method of claim 1 wherein the switching power converter is a single stage flyback-type switching power converter.
5. The method of claim 1 wherein detecting whether a dimmer is phase cutting an input voltage to the switching power converter comprises:
detecting the dimmer if less than a substantial amount of the input voltage is not passed by the dimmer; and
not detecting the dimmer if at least a substantial amount of the input voltage is passed by the dimmer;
wherein the substantial amount of the input voltage is passed if the dimmer passes at least 170 degrees of the input voltage for a cycle of the input voltage, and the cycle of the input voltage ranges from 0-180°.
6. The method of claim 1 wherein:
operating the switching power converter in the first mode if the dimmer is detected comprises operating the switching power converter in the first mode to regulate an output current to a load;
operating the switching power converter in the second mode if the dimmer is not detected comprises operating the switching power converter in the second mode to regulate the output current to the load; and
the load comprises one or more light emitting diodes.
7. The method of claim 1 further comprising:
initiating operation of the switching power converter in the first mode prior to detecting whether a dimmer is phase cutting the input voltage to the switching power converter.
8. The method of claim 7 wherein:
operating the switching power converter in the first, second, and transition modes comprises:
determining a peak value of an input current to the switching power converter; and
controlling the input current to a switch coupled to the switching power converter so that the switch conducts the input current until the input current reaches the peak value and then turning the switch off; and
transitioning between operating the switching power converter in the first mode and the second mode if a status of detection of the dimmer changes comprises transitioning between emphasis of a first term to emphasis of a second term of the following equation for determining the peak value of the input current to the switching power converter:
I
PEAK
=
(
2
×
i
IN
_
AVG
_
T
×
TT
T
1
)
+
(
Q
e
×
V
IN
V
IN
_
PEAK
)
i IN — AVG — T represents the average target value of an input current to the switching power converter;
TT equals a switching period of a control signal that controls input current to the switching power converter, and value of TT is measured from a previous cycle of the control signal;
T 1 is a pulse width of the control signal measured from a previous cycle of the control signal;
V IN is an input voltage to the switching power converter;
V IN —PEAK is a peak input voltage during a switching cycle of the control signal; and
Q e is a charge integration error;
(
2
×
i
IN
_
AVG
_
T
×
TT
T
1
)
wherein
is the first term of the equation, and
(
Q
e
×
V
IN
V
IN
_
PEAK
)
is the second term of the equation.
9. The method of claim 8 wherein transitioning between operating the switching power converter in the first mode and the second mode if a status of detection of the dimmer changes comprises:
approximately instantly transitioning from operating the switching power converter using the first term of the following equation to using the second term of the following equation by predetermining the value of Qe.
10. The method of claim 1 wherein operating the switching power converter in a first mode if the dimmer is detected comprises:
utilizing the first mode to determine a first peak value component of an input current to the switching power converter using a target average input current value, wherein the target average input current value is insufficient to allow the switching power converter to meet power demands of the load; and
utilizing the second mode to determine a second peak value component of the input current to allow the switching power converter to meet the power demands of the load.
11. An apparatus comprising:
a switching power converter;
a controller coupled to the switching power converter, wherein the controller is configured to:
detect whether a dimmer is phase cutting an input voltage to a switching power converter;
operate the switching power converter in a first mode if the dimmer is detected;
operate the switching power converter in a second mode if phase cutting of the input voltage is not detected;
transition between operating the switching power converter in the first mode and the second mode if a status of detection of the dimmer changes
operate the switching power converter in both the first and second mode to meet a power demand of a load coupled to the switching power converter, wherein to operate the switching power converter in both the first and second modes to meet the power demand of a load coupled to the switching power converter comprises:
to set an average input current target value for an input current to the switching power converter for operation of the switching power converter in the first mode, wherein the average input current target is insufficient to allow the switching power converter to provide a sufficient charge to meet a charge demand by the load coupled to the switching power converter; and
to operate the switching power converter in the second mode to allow the switching power converter to provide the sufficient charge to meet the charge demand by the load coupled to the switching power converter.
12. An apparatus comprising:
a switching power converter; and
a controller coupled to the switching power converter, wherein the controller includes a dimmer detector and the dimmer detector generates a dimmer detection output that controls operational characteristics of the switching power converter in one of at least two different operational modes depending on whether the detector detects a dimmer.
wherein the controller is configured to:
operate the switching power converter in both the first and second modes to meet a power demand of a load coupled to the switching power converter, wherein to operate the switching power converter in both the first and second mode to meet the power demand of a load coupled to the switching power converter comprises:
to set an average input current target value for an input current to the switching power converter for operation of the switching power converter in the first mode, wherein the average input current target is insufficient to allow the switching power converter to provide a sufficient charge to meet a charge demand by the load coupled to the switching power converter; and
to also operate the switching power converter in the second mode to allow the switching power converter to provide the sufficient charge to meet the charge demand by the load coupled to the switching power converter.
13. An apparatus comprising:
a controller to control a switching power converter, wherein the controller is configured to:
detect whether a dimmer is phase cutting an input voltage to the switching power converter;
operate the switching power converter in a first mode if the dimmer is detected;
operate the switching power converter in a second mode if phase cutting of the input voltage is not detected;
transition between operating the switching power converter in the first mode and the second mode if a status of detection of the dimmer changes; and
operate the switching power converter in both the first mode and the second mode to meet a power demand of a load coupled to the switching power converter, wherein to operate the switching power converter in both the first mode and the second mode to meet power the power demand of the load coupled to the switching power converter, the controller is further configured to:
set an average input current target value for an input current to the switching power converter for operation of the switching power converter in the first mode, wherein the average input current target is insufficient to allow the switching power converter to provide a sufficient charge to meet a charge demand by the load coupled to the switching power converter; and
also operate the switching power converter in the second mode to allow the switching power converter to provide the sufficient charge to meet the charge demand by the load coupled to the switching power converter.
14. The apparatus of claim 13 wherein the controller is further configured to:
generate a control signal to control a switch to control current in the switching power converter;
wherein to operate the switching power converter in the first mode if the dimmer is detected, the controller is further configured to operate the switching power converter to draw a substantially constant average input current to the switching power converter during an active time of the control signal.
15. The apparatus of claim 13 wherein to operate the switching power converter in the second mode if the dimmer is not detected, the controller is further configured to operate the switching power converter to draw an input current to the switching power converter to provide a power factor correction.
16. The apparatus of claim 13 wherein the switching power converter is a single stage flyback-type switching power converter.
17. The apparatus of claim 13 wherein to detect whether a dimmer is phase cutting an input voltage to the switching power converter, the controller is further configured to:
detect the dimmer if less than a substantial amount of the input voltage is not passed by the dimmer; and
not detect the dimmer if at least a substantial amount of the input voltage is passed by the dimmer;
wherein the substantial amount of the input voltage is passed if the dimmer passes at least 170 degrees of the input voltage for a cycle of the input voltage, and the cycle of the input voltage ranges from 0-180°.
18. The apparatus of claim 13 further comprising:
the switching power converter; and
a load coupled to the switching power converter, wherein the load comprises one or more light emitting diodes.
19. The apparatus of claim 13 wherein the controller is further configured to:
initiate operation of the switching power converter in the first mode prior to detecting whether a dimmer is phase cutting the input voltage to the switching power converter.
20. The apparatus of claim 13 wherein:
to operate the switching power converter in the first, second, and transition modes, the controller is further configured to:
determine a peak value of an input current to the switching power converter; and
control the input current to a switch coupled to the switching power converter so that the switch conducts the input current until the input current reaches the peak value and then turning the switch off; and
to transition between operating the switching power converter in the first mode and the second mode if a status of detection of the dimmer changes, the controller is further configured to transition between operating the switching power converter in the first mode and the second mode if a status of detection of the dimmer changes comprises transitioning between emphasis of a first term to emphasis of a second term of the following equation for determining the peak value of the input current to the switching power converter:
I
PEAK
=
(
2
×
i
IN
_
AVG
_
T
×
TT
T
1
)
+
(
Q
e
×
V
IN
V
IN
_
PEAK
)
i IN — AVG — T represents the average target value of an input current to the switching power converter;
TT equals a switching period of a control signal that controls input current to the switching power converter, and value of TT is measured from a previous cycle of the control signal;
T 1 is a pulse width of the control signal measured from a previous cycle of the control signal;
V IN is an input voltage to the switching power converter;
V IN — PEAK is a peak input voltage during a switching cycle of the control signal; and
Qe is a charge integration error;
(
2
×
i
IN
_
AVG
_
T
×
TT
T
1
)
wherein
is the first term of the equation, and
(
Q
e
×
V
IN
V
IN
_
PEAK
)
is the second term of the equation.
21. The apparatus of claim 20 wherein to transition between operating the switching power converter in the first mode and the second mode if a status of detection of the dimmer changes, the controller is further configured to:
approximately instantly transition from operating the switching power converter using the first term of the following equation to using the second term of the following equation by predetermining the value of Qe.
22. The apparatus of claim 13 wherein to operate the switching power converter in a first mode if the dimmer is detected, the controller is further configured to:
utilize the first mode to determine a first peak value component of an input current to the switching power converter using a target average input current value, wherein the target average input current value is insufficient to allow the switching power converter to meet power demands of the load; and
utilize the second mode to determine a second peak value component of the input current to allow the switching power converter to meet the power demands of the load.