Integrated magnetics with isolated drive circuit
A switch-mode power converter includes a power isolation transformer and a drive transformer having their various windings collectively wound on a magnetic core having a center leg and outer legs. A primary winding and one or more secondary windings of the power transformer are wound on the center leg, and first and second windings of the drive transformer are wound on an outer leg. A primary control circuit controls one or more primary switches to supply the input voltage to the primary winding. A secondary control circuit controls secondary switches connected between the secondary windings and a load. Another control circuit controls operation the primary and secondary control circuits based at least in part on a feedback signal. The drive transformer windings are further configured to provide isolation between the primary control circuit and the synchronous rectifier control circuit.
1. A switch-mode power converter for converting an input voltage from an input source to an output voltage for supply to a load coupled to converter load terminals, the power converter comprising:
a power isolation transformer further comprising a magnetic core having a center leg and outer legs, one or more primary windings and one or more secondary windings of the power transformer being wound on the center leg;
a primary converter circuit comprising one or more primary controllable power switches effective to supply the input voltage to one or more primary windings of the power isolation transformer;
a secondary converter circuit fully isolated from the primary converter circuit and comprising one or more secondary switches being individually switchable and further coupled between the one or more secondary windings and the load terminals;
a primary switch control circuit effective to control conduction of one or more primary controllable power switches;
a secondary switch control circuit effective to control conduction of the one or more secondary switches;
a control circuit effective to control operation of the primary switch control circuit and the secondary switch control circuit based at least in part on a feedback signal;
a drive transformer comprising at least first and second drive transformer windings wound on an outer leg of the magnetic core, the drive transformer windings configured to provide power for controlling the primary and secondary switches, the drive transformer windings further configured to provide isolation between the primary and secondary control circuits;
the voltage across primary windings having voltage waveforms of similar shape as the drive voltage of the controllable power switches except during turn-on and turn-off transitions; and
the windings of the drive transformer tightly coupled with each other on the outer leg, and further loosely coupled with the windings of the power transformer, wherein different voltage waveforms are provided in the windings of the drive transformer and windings of power transformer for a short period of time sufficient to initiate turn-on or turn-off of the controllable switches coupled to the power transformer.
2. The switch-mode power converter of claim 1 , the magnetic core comprising an E-shaped core having a center leg and two outer legs.
3. The switch-mode power converter of claim 2 , comprising:
a primary switch control circuit for each primary controllable power switch;
the drive transformer further comprising two or more drive transformer windings wound on an outer leg of the magnetic core, the first drive transformer winding connected to the control circuit, the other drive transformer windings connected to primary switch control circuits to control operation of the primary controllable switches as well as providing power for controlling the primary controllable power switches,
the drive transformer windings further configured to provide isolation between primary switch control circuits and the synchronous rectifiers control circuit.
4. The switch-mode power converter of claim 1 , further comprising an active clamp circuit effective to clamp a drive voltage for power switches, control circuit and synchronous rectifiers independent of the input voltage.
5. The switch-mode power converter of claim 1 , drive transformer windings being wound in distributed fashion on both of an outer leg and the center leg of the magnetic core.
6. The switch-mode power converter of claim 1 , the magnetic core further comprising a gap in the center leg upon which transformer windings are associated.
7. The switch-mode power converter of claim 6 , further comprising an active clamp circuit effective to clamp a portion of the drive voltage as induced by the outer leg.
8. The switch-mode power converter of claim 7 , the drive transformer further effective to provide power to control circuit and synchronous rectifiers control circuit via first drive transformer winding.
9. The switch-mode power converter of claim 1 , comprising:
an output inductor further comprising an inductor magnetic core having at least one inner leg, a winding being wound on an inner leg, the winding having a voltage waveform of similar shape as that of drive voltage waveforms of the primary controllable switches except during their turn-on and turn-off transitions,
the windings of the drive transformer tightly coupled with each other on an outer leg of the inductor magnetic core, and further loosely coupled with the winding of the output inductor, wherein different voltage waveforms are provided in the windings of the drive transformer and winding of the output inductor for a short period of time sufficient to initiate turn-on or turn-off of the controllable switches coupled to the power transformer.
10. The switch-mode power converter of claim 9 , the drive transformer windings being wound in distributed fashion on both of an outer leg and the center leg of the inductor magnetic core.
11. The switch-mode power converter of claim 9 , further comprising an active clamp circuit effective to clamp a drive voltage for the primary controllable switches independent of the input voltage.
12. The switch-mode power converter of claim 9 , further comprising an active clamp circuit effective to clamp a portion of the drive voltage as induced by the outer leg.
13. The switch-mode power converter of claim 9 , the drive transformer further effective to provide power to control circuit and synchronous rectifiers control circuit via the first drive transformer winding.
14. A switch-mode power converter for converting an input voltage from an input source to an output voltage for supply to a load coupled to converter load terminals, the power converter comprising:
a power isolation transformer further comprising a magnetic core having a center leg and outer legs, one or more primary windings and one or more secondary windings of the power transformer being wound on the center leg;
a primary converter circuit comprising one or more primary controllable power switches effective to supply the input voltage to one or more primary windings of the power isolation transformer;
a secondary converter circuit fully isolated from the primary converter circuit and comprising one or more secondary switches being individually switchable and further coupled between the one or more secondary windings and the load terminals;
a primary switch control circuit effective to control conduction of the one or more primary controllable power switches;
a secondary switch control circuit effective to control conduction of the one or more secondary switches;
an output inductor further comprising an inductor magnetic core having at least one inner leg, an output inductor winding being wound on an inner leg; and
a drive transformer comprising at least first and second drive transformer windings tightly coupled with each other on an outer leg of the inductor magnetic core, and further loosely coupled with the winding of the output inductor, the drive transformer windings configured to provide power for controlling the primary and secondary switches, the drive transformer windings further configured to provide isolation between the primary and secondary control circuits,
wherein different voltage waveforms are provided in the windings of the drive transformer and winding of the output inductor for a short period of time sufficient to initiate turn-on or turn-off of the controllable switches coupled to the power transformer, and
wherein the output inductor winding having a voltage waveform of similar shape as that of drive voltage waveforms of the primary controllable switches except during their turn-on and turn-off transitions.
15. The switch-mode power converter of claim 14 , the drive transformer windings being wound in distributed fashion on both of an outer leg and the center leg of the inductor magnetic core.
16. The switch-mode power converter of claim 14 , further comprising an active clamp circuit effective to clamp a drive voltage for the primary controllable switches independent of the input voltage.
17. The switch-mode power converter of claim 14 , further comprising an active clamp circuit effective to clamp a portion of the drive voltage as induced by the outer leg.
18. A switch-mode power converter for converting an input voltage from an input source to an output voltage for supply to a load coupled to converter load terminals, the power converter comprising:
a power isolation transformer further comprising a magnetic core having a center leg and outer legs, one or more primary windings and one or more secondary windings of the power transformer being wound on the center leg;
a primary converter circuit comprising one or more primary controllable power switches effective to supply the input voltage to one or more primary windings of the power isolation transformer;
a secondary converter circuit fully isolated from the primary converter circuit and comprising one or more secondary switches being individually switchable and further coupled between the one or more secondary windings and the load terminals;
a primary switch control circuit effective to control conduction of one or more primary controllable power switches;
a secondary switch control circuit effective to control conduction of the one or more secondary switches;
a control circuit effective to control operation of the primary switch control circuit and the secondary switch control circuit based at least in part on a feedback signal; and
a drive transformer comprising at least first and second drive transformer windings wound in distributed fashion on both of an outer leg and the center leg of the magnetic core, the drive transformer windings configured to provide power for controlling the primary and secondary switches, the drive transformer windings further configured to provide isolation between the primary and secondary control circuits.