1. An apparatus, comprising:
a transformer having a primary winding and a secondary winding;
a first switching device coupled to the primary winding for generating changes in voltage across the primary winding such that the primary winding transfers energy to the secondary winding;
an output filter having an inductor and a capacitor in series;
a first rectifier coupled between a first end of the secondary winding and the output filter, wherein the first rectifier is a synchronous rectifier;
a second rectifier in parallel with the output filter and coupled between a second end of the secondary winding and the first rectifier; and
post regulation logic configured to adjust a parameter of the synchronous rectifier based on an output of the apparatus in an effort to match a target output.
2. The apparatus of claim 1, wherein the parameter is a resistance of the synchronous rectifier or a voltage drop across the synchronous rectifier.
3. The apparatus of claim 2, wherein the post regulation logic is configured to linearly adjust the resistance of the synchronous rectifier.
4. The apparatus of claim 2, wherein the synchronous rectifier is a metal oxide semiconductor field effect transistor (MOSFET) and the post regulation logic is configured to linearly adjust the voltage drop across the synchronous rectifier from a drain-to-source on-resistance (RDS,on) multiplied with a current through the synchronous rectifier to a forward voltage drop of a body diode of the MOSFET.
5. The apparatus of claim 2, wherein the post regulation logic is configured to adjust the resistance of the synchronous rectifier by pulse width modulating the resistance between a first resistance and a second resistance.
6. The apparatus of claim 5, wherein the first resistance is a drain-to-source on-resistance (RDS,on) of a metal oxide semiconductor field effect transistor (MOSFET) and the second resistance is a drain-to-source off-resistance (RDS,off) of the MOSFET.
7. The apparatus of claim 2, wherein the post regulation logic is configured to adjust the voltage drop across the synchronous rectifier by pulse width modulating the voltage drop between a first level and a second level.
8. The apparatus of claim 7, wherein the synchronous rectifier is a metal oxide semiconductor field effect transistor (MOSFET), the first level is a drain-to-source on-resistance (RDS,on) of the MOSFET multiplied with a current through the synchronous rectifier, and the second level is a forward voltage drop of a body diode of the MOSFET.
9. The apparatus of claim 1, wherein the output is an output voltage across the capacitor, an output current to a load, or an output power delivered to a load, and the target output is a target output voltage, a target output current, or a target output power.
10. The apparatus of claim 1, wherein the second rectifier is a silicon diode, a Schottky diode, or an n-channel metal oxide semiconductor field effect transistor (MOSFET).
11. An apparatus, comprising:
a transformer having a primary winding and a secondary winding;
a means for switching coupled to the primary winding for generating changes in voltage across the primary winding such that the primary winding transfers energy to the secondary winding;
a means for filtering an output of the apparatus;
a first means for rectifying coupled between a first end of the secondary winding and the means for filtering, wherein the first means for rectifying is a synchronous rectifier;
a second means for rectifying disposed in parallel with the means for filtering and coupled between a second end of the secondary winding and the first means for rectifying; and
means for adjusting a parameter of the synchronous rectifier such that an output of the apparatus is post regulated to meet a target output.
12. The apparatus of claim 11, wherein the parameter is a resistance of the synchronous rectifier or a voltage drop across the synchronous rectifier.
13. The apparatus of claim 12, wherein the means for adjusting is configured to linearly adjust the resistance of the synchronous rectifier.
14. The apparatus of claim 12, wherein the means for adjusting is configured to adjust the resistance of the synchronous rectifier or the voltage drop across the synchronous rectifier by pulse width modulating the resistance or the voltage drop between a first level and a second level.
15. The apparatus of claim 11, wherein the output is an output voltage, an output current, or an output power delivered to a load, and the target output is a target output voltage, a target output current, or a target output power.
16. A method, comprising:
in a first state, closing a switching device coupled to a primary winding of a transformer such that current flows through a first rectifier coupled between an output filter and a first end of a secondary winding of the transformer, through an output inductor of the output filter, and through a load in parallel with an output capacitor of the output filter, wherein the first rectifier is a synchronous rectifier and the output inductor and the output capacitor are in series;
in a second state, opening the switching device such that current flows through the output inductor, the load, and a second rectifier in parallel with the output filter and coupled between the first rectifier and a second end of the secondary winding;
alternating between the first state and the second state; and
adjusting a parameter of the synchronous rectifier such that an output associated with the load is post regulated to meet a target output.
17. The method of claim 16, wherein adjusting the parameter comprises adjusting a resistance of the synchronous rectifier or a voltage drop across the synchronous rectifier.
18. The method of claim 17, wherein adjusting the parameter comprises linearly adjusting the resistance of the synchronous rectifier.
19. The method of claim 17, wherein adjusting the parameter comprises pulse width modulating the resistance of the synchronous rectifier or the voltage drop across the synchronous rectifier between a first level and a second level.
20. The method of claim 16, wherein the output associated with the load is an output voltage, an output current, or an output power delivered to the load, and the target output is a target output voltage, a target output current, or a target output power.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A lens module comprising:
a first lens comprising an imaging portion and a non-imaging portion surrounding the imaging portion, the non-imaging portion defining an annular conic surface;
an annular conic opaque plate contacting with the annular conic surface; and
a second lens comprising an imaging portion and a non-imaging portion surrounding the imaging portion, the object-side surface of the non-imaging portion being ladder-like shaped and comprising at least two step surfaces, and a junction of two adjacent step surfaces abutting against the opaque plate.
2. The lens module of claim 1, further comprising a lens barrel, wherein the first lens, the second lens, and the annular conic opaque plate are received in the lens barrel, the lens barrel comprises a main body and an annular aperture plate positioned at the object-side end of the main body, a first engaging portion is positioned on the inner surface of the annular aperture plate, a second engaging portion is positioned on the object-side surface of the non-imaging portion of the first lens, and the first engaging portion fittingly engages with the second engaging portion to locate the first lens on the inner surface of the aperture plate.
3. The lens module of claim 2, wherein the first engaging portion is a cylindrical-shaped protrusion, the second engaging portion is a cylindrical-shaped groove, and the protrusion is received in the groove.
4. The lens module of claim 1, wherein the opaque plate is non-reflective.
5. The lens module of claim 2, wherein the annular aperture plate defines an aperture opening at the center thereof to allow light rays from objects of interest to enter the lens barrel.
6. The lens module of claim 5, wherein the aperture opening tapers towards the image-side of the lens barrel.
7. The lens module of claim 1, wherein a flange bulges along the periphery of the non-imaging portion of the first lens, the annular conic surface extends from the flange to the imaging portion, the at least two step surfaces comprises a first step surface, and the first step surface is positioned on and contacts the flange of the first lens.
8. The lens module of claim 7, wherein the at least two step surfaces further comprises a second step surface and a third step surface, and a junction of the second step surface and the third step surface abuts against the opaque plate.
9. The lens module of claim 8, further comprising a third lens, the image-side surface of the non-imaging portion of the second lens is step-like shaped and comprises a fourth step surface and a fifth step surface, the object-side surface of the non-imaging portion of the third lens is step-like shaped and comprises a sixth step surface and a seventh step surface, the sixth step surface is shaped corresponding to the fourth step surface, the seventh step surface is shaped corresponding to the fifth step surface, the fourth step surface abuts against the sixth step surface, and the fifth step surface abuts against the seventh step surface.
10. The lens module of claim 9, wherein an adhesive layer is coated between the seventh step surface and the fifth step surface to firmly attach the third lens on the image-side surface of the non-imaging portion of the second lens.
11. The lens module of claim 10, wherein the adhesive layer is comprised of opaque materials.
12. A lens module, comprising:
a lens barrel defining an aperture opening;
a first lens received in the lens barrel and having an object-side surface and an image-side surface opposite to the object-side surface, the object-side surface being adjacent to the aperture opening, and the image-side surface having an annular conic surface;
a second lens received in the lens barrel; and
an annular opaque plate received in the lens barrel and sandwiched between the first and second lenses, the opaque plate contacting the annular conic portion.
13. The lens module of claim 12, wherein the first lens, the second lens and the annular opaque plate are substantially coaxially received in the lens barrel.
14. The lens module of claim 12, wherein the annular opaque plate is conic shaped and completely contacts the annular conic surface.
15. The lens module of claim 12, wherein the first lens comprises an imaging portion and a non-imaging portion surrounding the imaging portion, a flange bulges along the periphery of the non-imaging potion, the flange contacts the second lens, and the annular conic surface extends from the flange to the imaging portion.
16. The lens module of claim 15, wherein a first engaging is positioned on an inner surface of the lens barrel, a second engaging portion is positioned on the image-side surface of the first lens, and the first engaging portion engages with the second engaging portion to locate the first lens on the lens barrel.
17. The lens module of claim 15, wherein the second lens has an object-side surface and an image-side surface opposite to the object-side surface, the object-side surface comprises at least two step surfaces, and a junction of two adjacent step surfaces contacts the annular opaque plate.
18. The lens module of claim 17, wherein the at least two step surfaces comprises a first step surface, a second step surface and a third step surface, the first step surface contacts the flange, and a junction of the second step surface and the third step surface abuts against the annular opaque plate.
19. The lens module of claim 18, further comprising a third lens received in the lens barrel and contacting the image-side surface of the second lens.
20. The lens module of claim 19, wherein the second lens comprises a fourth step surface and a fifth step surface, the third lens comprises a sixth step surface and a seventh step surface, the fourth step surface contacts the sixth step surface, and the fifth step surface contacts the seventh step surface.