Switch mode converter and improved primary switch drive therefor

A switch mode converter for providing an output voltage comprising:

• at least two primary switches each having a first input adapted to be coupled to an input voltage, a second input, and an output, and each switch being switchable between on and off states respectively coupling and decoupling the input voltage at the first input and the output in response to control signals supplied to the respective second input;
• and
• controller means coupled to the second input of each of the primary switches for providing control signals thereto, the controller means providing at least one turn-on control signal during a first time period to turn a first primary switch on during the first time period, and at least one turn-on control signal during a second time period to turn a second primary switch on during the second time period, the controller means providing a third time period between each adjacent first time period and second time period during which no turn-on signals are supplied by the controller means, the controller means supplying the turn-on control signals during the first and second time periods in response to a condition of the output voltage, the controller means comprising:
• a transformer coupled to each primary switch having a primary winding and a secondary winding, the secondary winding of the respective transformer being coupled to the respective second input of the respective primary switch and supplying said control signals thereto;
• first current supplying means coupled to each of the primary windings of the trnsformers for supplying current to the respective transformer primary winding;
• second current supplying means respectively coupled to the output of each of the primary switches and to each of the primary windings of the transformers for supplying current to the respective transformer primary winding from the input voltage when it is coupled to the output of the respective switch in the on state thereof;
• and
• switch means coupled to each of the primary windings of the transformers for selectively permitting and preventing current flow through the respective transformer primary winding;
• the transformers and the first and second current supplying means cooperating to provide a turn-off control signal to switch a respective primary switch off when the switch means permits current to flow through the respective transformer primary winding and to maintain the respective primary switch off while current is permitted to flow, and to provide a turn-on control signal to switch the respective primary switch on when the switch means prevents current from flowing through the respective transformer primary winding and to maintain the respective primary switch on while current is prevented from flowing, the respective second current supplying means supplying current to the respective transformer primary winding when a respective switch is in the on state during only an initial portion of the time in which current is permitted to flow through the respective transformer primary winding effective to cause the respective transformer to switch the respective primary switch off, and the respective first current supplying means supplying current at least after the initial portion of the time in which current is permitted to flow through the respective transformer primary winding effective to cause the respective transformer to maintain the respective primary switch off and to enable the respective transformer to switch the respective primary switch back on when current is next permitted to flow through the respective transformer primary winding.

A switch mode converter for providing an output voltage from an input voltage comprising:

• at least two transistors adapted to be coupled to an input voltage to be controlled and switchable to conduct the input voltage through the transistor to an output thereof, and controller means coupled to the base of each transistor for providing control signals thereto, the controller means providing at least one turn-on control signal during a first time period to turn a first transistor on during the first time period, and at least one turn-on control signal during a second time period to turn a second transistor on during the second time period, the controller means providing a third time period between each adjacent first time period and second time period during which no turn-on signals are supplied by the controller means, the controller means supplying the turn-on control signals during the first and second time periods in response to a condition of the output voltage, the controller means comprising:
• a transformer coupled to each transistor having a primary winding and a secondary winding, the secondary winding of the respective transformer being coupled to the respective base of the respective transistor and supplying said signals thereto;
• first current supplying means coupled to each of the primary windings of the trnsformers for supplying current to the respective transformer primary winding;
• second current supplying means respectively coupled to the output of each of the transistors and to each of the primary windings of the transformers for supplying current to the respective transformer primary winding from the input voltage when it is switched to the output of the respective transistor in the on state thereof;
• and
• switch means coupled to each of the primary windings of the transformers for selectely permitting and preventing current flow through the respective transformer primary winding;
• the transformers and the first and second current supplying means cooperating to provide a turn-off control signal to switch a respective transistor off when the switch means permits current to flow through the respective transformer primary winding and to maintain the respective transistor off while current is permitted to flow, and to provide a turn-on control signal to switch a respective transistor on when the switch means prevents current from flowing through the respective transformer primary winding and to maintain the respective transistor on while current is prevented from flowing, the respective second current supplying means supplying current to the respective transformer primary winding when the respective transistor is on during only an initial portion of the time in which current is permitted to flow through the respective transformer primary winding effective to cause the respective transformer to switch the respective transistor off, and the second current supplying means supplying current at least after said initial portion of the time during which current is permitted to flow through the respective transformer primary winding effective to cause the respective transformer to switch the respective transistor off and to enable the respective transformer to switch the respective transistor back on when current is next prevented from flowing through the respective transformer primary winding.