Method to control a minimum pulsewidth in a switch mode power supply
First Claim
1. A method of controlling a switching mode power converter, the method comprising:
- configuring a switching mode power converter comprising a transformer having a primary winding coupled to an input supply voltage and a secondary winding, a switch coupled in series to the primary winding, a controller coupled to the switch, and a primary side auxiliary winding electrically coupled to the controller and magnetically coupled to the secondary winding;
determining a minimum voltage across the secondary winding to enable energy transfer from a primary side of the transformer to a secondary side;
turning ON the switch;
comparing a voltage across the auxiliary winding to a threshold voltage while the switch is ON, wherein the threshold voltage is proportional to the minimum voltage; and
turning OFF the switch once the voltage across the auxiliary winding reaches the threshold voltage, wherein a time period between turning ON the switch and turning OFF the switch is a minimum pulse width of the switch corresponding to a minimum energy necessary to enable the energy transfer from the primary side to the secondary side.
3 Assignments
0 Petitions
Accused Products
Abstract
A power converter circuit includes a transformer and a main switch controller by a primary side controller. A sensing circuit is implemented that senses the voltage at an auxiliary winding of the transformer while the main switch is ON. The auxiliary winding is another winding on the primary side of the transformer, magnetically coupled to the secondary winding and electrically isolated from the primary winding. When the voltage across the auxiliary winding reaches a predefined threshold voltage level, the main switch is switched OFF. The threshold voltage level is set at a value that minimizes an amount of energy transferred per pulse to the secondary side of the circuit while maintaining a minimum amount of energy transfer to enable output voltage sensing at the auxiliary winding.
-
Citations
21 Claims
-
1. A method of controlling a switching mode power converter, the method comprising:
-
configuring a switching mode power converter comprising a transformer having a primary winding coupled to an input supply voltage and a secondary winding, a switch coupled in series to the primary winding, a controller coupled to the switch, and a primary side auxiliary winding electrically coupled to the controller and magnetically coupled to the secondary winding; determining a minimum voltage across the secondary winding to enable energy transfer from a primary side of the transformer to a secondary side; turning ON the switch; comparing a voltage across the auxiliary winding to a threshold voltage while the switch is ON, wherein the threshold voltage is proportional to the minimum voltage; and turning OFF the switch once the voltage across the auxiliary winding reaches the threshold voltage, wherein a time period between turning ON the switch and turning OFF the switch is a minimum pulse width of the switch corresponding to a minimum energy necessary to enable the energy transfer from the primary side to the secondary side. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
-
-
12. A switching mode power converter comprising:
-
a transformer having a primary winding coupled to an input supply voltage and a secondary winding; a switch coupled in series to the primary winding; a controller coupled to the switch, wherein the controller is configured to turn the switch ON and OFF; a primary side auxiliary winding magnetically coupled to the secondary winding; and a threshold voltage detection circuit coupled to the auxiliary winding and to the controller, wherein the threshold voltage detection circuit is configured to compare a voltage across the auxiliary winding to a minimum voltage while the switch is ON and to send a signal to the controller once the voltage across the auxiliary winding reaches the minimum voltage, wherein the minimum voltage is a minimum voltage across the secondary winding to enable energy transfer from a primary side of the transformer to a secondary side of the transformer, wherein the controller is configured to switch OFF the switch in response to receiving the signal from the threshold voltage detection circuit such that a minimum energy is stored in the primary winding necessary to enable energy transfer from the primary side of the transformer to the secondary side. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
-
Specification