Average input current estimation based on primary side current sense
View Patent ↗The embodiments herein describe a power converter including a controller that estimates input current of the power converter. The controller estimates the input current without explicitly sensing the input current. The estimated input current can be used in various applications such as regulating power factor and total harmonic distortion as well as estimating current required to maintain proper operation of a dimmer switch in light emitting diode lamp systems.
1. A switching power converter comprising:
a magnetic component coupled to an input voltage and an output of the switching power converter;
a switch coupled to the magnetic component to control current through at least part of the magnetic component, current through at least the part of the magnetic component generated while the switch is turned on and not being generated while the switch is turned off;
a controller including a pin for sensing the current through at least the part of the magnetic component, the controller configured to generate a control signal to turn on or turn off the switch during a plurality of switching cycles of the switch;
a resistive voltage divider including a first resistor and a second resistor, the current through at least the part of the magnetic component flows through the first resistor but not through the second resistor; and
wherein the controller is configured to estimate an average input current of the switching power converter based on the following equation:
I
in_avg
=
1
2
·
D
ISENSE
R
SNS
·
T
on
T
P
where I in — avg is the estimated average input current, D ISENSE is a value representing a target peak current through at least the part of the magnetic component, R SNS is an impedance of the first resistor, T on is an on-time of the switch during a switching cycle of the power converter, and T p is a period of the switching cycle.
2. The switching power converter of claim 1 , wherein the controller is further configured to regulate the estimated average input current of the switching power converter to follow a reference current.
3. The switching power converter of claim 1 , wherein an impedance of the second resistor is proportional to the impendence of the first resistor by a scaling factor.
4. The switching power converter of claim 1 , wherein the controller is configured to supply a current via a path including the second resistor followed by the first resistor during a measurement mode of the controller to determine the impedance of the first resistor based on a voltage measured across the resistive voltage divider, the supplied current, and a relationship between the impedance of the first resistor and an impedance of the second resistor.
5. In a controller, a method of controlling a switching power converter, the switching power converter including a magnetic component coupled to an input voltage and an output of the switching power converter and a switch coupled to the magnetic component to control current through at least a part of the magnetic component, current through at least the part of the magnetic component being generated while the switch is turned on and not being generated while the switch is turned off, the switching power converter further including a resistive voltage divider including a first resistor and a second resistor, the current through at least the part of the magnetic component flows through the first resistor but not through the second resistor, the method comprising:
generating a control signal to turn on or turn off the switch during a plurality of switching cycles of the switch; and
estimating an average input current of the switching power converter based on the following equation:
I
in_avg
=
1
2
·
D
ISENSE
R
SNS
·
T
on
T
P
where I in — avg is the estimated average input current, D ISENSE is a value representing a target peak current through at least the part of the magnetic component, R SNS is an impedance of the first resistor, T on is an on-time of the switch during a switching cycle of the power converter, and T p , is a period of the switching cycle.
6. The method of claim 5 , further comprising:
regulating the estimated average input current of the switching power converter to follow a reference current.
7. The method of claim 5 , further comprising:
supplying a current via a path including the second resistor followed by the first resistor during a measurement mode of the controller;
determining the impedance of the first resistor based on a voltage measured across the resistive voltage divider, the supplied current, and a relationship between the impedance of the first resistor and an impedance of the second resistor.
8. A switching power converter comprising:
a magnetic component coupled to an input voltage and an output of the switching power converter;
a switch coupled to the magnetic component to control current through at least part of the magnetic component, current through at least the part of the magnetic component generated while the switch is turned on and not being generated while the switch is turned off;
a controller including a pin for sensing the current through at least the part of the magnetic component, the controller configured to generate a control signal to turn on or turn off the switch during a plurality of switching cycles of the switch;
a resistive voltage divider including a first resistor and a second resistor, the current through at least the part of the magnetic component flows through the first resistor but not through the second resistor;
wherein the controller is configured to supply a current via a path including the second resistor followed by the first resistor during a measurement mode of the controller to determine an impedance of the first resistor based on a voltage measured across the resistive voltage divider, the supplied current, and a relationship between the impedance of the first resistor and an impedance of the second resistor; and
wherein the controller is configured to estimate an average input current of the switching power converter based on a value representing a target peak current through at least the part of the magnetic component and the determined impedance of the first resistor.
9. The switching power converter of claim 8 , wherein the controller is further configured to regulate the estimated average input current of the switching power converter to follow a reference current.
10. The switching power converter of claim 8 , wherein the impedance of the second resistor is proportional to the impendence of the first resistor by a scaling factor.
11. In a controller, a method of controlling a switching power converter, the switching power converter including a magnetic component coupled to an input voltage and an output of the switching power converter and a switch coupled to the magnetic component to control current through at least a part of the magnetic component, current through at least the part of the magnetic component being generated while the switch is turned on and not being generated while the switch is turned off, the switching power converter further including a resistive voltage divider including a first resistor and a second resistor, the current through at least the part of the magnetic component flows through the first resistor but not through the second resistor, the method comprising:
generating a control signal to turn on or turn off the switch during a plurality of switching cycles of the switch;
supplying a current via a path including the second resistor followed by the first resistor during a measurement mode of the controller;
determining an impedance of the first resistor based on a voltage measured across the resistive voltage divider, the supplied current, and a relationship between the impedance of the first resistor and an impedance of the second resistor; and
estimating an average input current of the switching power converter based on a value representing a target peak current through at least the part of the magnetic component and the determined impedance of the first resistor.
12. The method of claim 11 , further comprising:
regulating the estimated average input current of the switching power converter to follow a reference current.
13. The method of claim 11 , wherein the impedance of the second resistor is proportional to the impendence of the first resistor by a scaling factor.