| 摘要 |
A circuit includes a transformer with a primary, secondary, and auxiliary. A first control circuit actuates a first switch circuit based on a wake-up signal to cause the primary to transmit power to the secondary. A second control circuit actuates a second switch circuit based on an output voltage at the secondary being less than a threshold to generate the wake-up signal to the secondary for transmission to the auxiliary. The second switch circuit has a transistor with a source coupled to a reference node, a gate coupled to the second control circuit. A first diode has an anode coupled to the source and a cathode coupled to the drain, and blocks flow of current from the drain to the source. A second diode has an anode coupled to the substrate and a cathode coupled to the drain, and blocks flow of current from the drain to the substrate. |
| 主权项 |
1. A circuit, comprising:
a transformer having a primary winding, a secondary winding, and an auxiliary winding; a first switch circuit coupled in series between the primary winding and a first reference node; a second switch circuit coupled in series between the secondary winding and a second reference node; a first control circuit coupled to the auxiliary winding and configured to actuate the first switch circuit in response to receipt of a wake-up signal so as to cause the primary winding to transmit power to the secondary winding to thereby provide a regulated output signal; a second control circuit configured to actuate the second switch circuit in response to an output voltage at the secondary winding being less than a threshold value so as to generate the wake-up signal to the secondary winding for transmission to the auxiliary winding; wherein the second switch circuit comprises an integrated circuit having components integrated therein comprising:
a power transistor having a drain, a source coupled to the second reference node, a gate coupled to the second control circuit, and a substrate,a first diode formed from parasitic junctions of the power transistor, the first diode having an anode coupled to the source of the power transistor and a cathode coupled to the drain of the power transistor, the first diode configured to block flow of current from the drain of the power transistor to the source of the power transistor,a second diode formed from parasitic junctions of the power transistor, the second diode having an anode coupled to the substrate of the power transistor and a cathode coupled to the drain of the power transistor, the second diode configured to block flow of current from the drain of the power transistor to the substrate of the power transistor,a third diode having an anode coupled to the secondary winding of the transformer and a cathode coupled to the drain of the power transistor, anda third switch coupled in parallel with the third diode between the secondary winding of the transformer and the drain of the power transistor, the third switch being configured to be controlled by the second control circuit such that the third switch closes when the power transistor is actuated. |
