Trigger circuitry for fast, low-power state transitions

An article of manufacture comprising a flyback converter, the flyback converter comprising:

• a primary side comprising an input port;
• a secondary side comprising an output port, wherein the secondary side is galvanically isolated from the primary side;
• and
• a power transformer configured to transfer input power received at the input port to provide output power at the output port, wherein:
• the primary side further comprises a primary-side switch configured to selectively enable the input power at the input port to be transferred via the power transformer to the output power at the output port;
• the secondary side further comprises a demand pulse generator that (i) determines when to turn on the primary-side switch based on output voltage or output current at the output port and (ii) generates corresponding demand pulses;
• the primary side comprises a primary-side magnetically coupled conductor;
• the secondary side comprises a secondary-side magnetically coupled conductor configured to be magnetically coupled to the primary-side magnetically coupled conductor to convey the demand pulses from the secondary side to the primary side;
• the primary-side switch is turned on in response to a demand pulse conveyed from the secondary side to the primary side;
• the demand pulse generator comprises:
• an n-type transistor having a base, a collector, and an emitter and characterized by a turn-on threshold voltage;
• a p-type transistor having a base, a collector, and an emitter and characterized by a turn-on threshold voltage, wherein the collector and emitter of the n-type transistor are connected in series with the collector and emitter of the p-type transistor such that, when the two transistors are turned on, current flows from the collector of the n-type transistor to the collector of the p-type transistor;
• and
• a positive-feedback capacitor connected between the collector of a first of the two transistors and the base of a second of the two transistors, wherein:
• the demand pulse generator is configured such that (i) the two transistors turn on together when the voltage at the base of the n-type transistor exceeds the voltage at the base of the p-type transistor by at least the sum of the turn-on threshold voltages of the two transistors and (i) the two transistors turn off together when the voltage at the base of the n-type transistor fails to exceed the voltage at the base of the p-type transistor by at least the sum of the turn-on threshold voltages of the two transistors;
• and
• the positive-feedback capacitor ensures that the two transistors turn fully on and off together.