Flyback converter with improved response
A flyback converter is described, configured to operate in a continuous mode with two primary side switches and one secondary side switch, wherein operation contains three switch states; a Primary state wherein both primary side switches are on and current increases in a transformer primary, a Circulate state wherein only one primary switch is on and current circulates in the transformer primary, and a Secondary state wherein both primary switches are off, the secondary side switch is on, and current flows from a transformer secondary into an output of the converter.
1 . An electronic circuit comprising:
a flyback converter configured to operate in a continuous mode, the flyback converter including:
a coupled inductor having a primary winding and a secondary winding;
a first switch having a first input terminal, a first output terminal, and a first control terminal, wherein the first input terminal is coupled to a voltage input terminal and the first output terminal is coupled to a first end of the primary winding;
a second switch having a second input terminal, a second output terminal, and a second control terminal, wherein the second input terminal is coupled to a second end of the primary winding; and
a third switch having a third input terminal, a third output terminal, and a third control terminal, wherein the third input terminal is coupled to a first end of the secondary winding;
wherein the flyback converter is configured to transition between three switch states, the three switch states including:
a primary state wherein the first and second switches are on and current increases in the primary winding of the coupled inductor,
a circulate state wherein exactly one of the first and second switches is on and current circulates in the primary winding of the coupled inductor, and
a secondary state wherein both the first and second switches are off, the third switch is on, and current flows from the secondary winding of the coupled inductor into an output of the flyback converter; and
a processing logic configured to automatically control a respective state of each of the first, second, and third switches, wherein the processing logic is configured to transition the flyback converter between the three switch states, and is configured to transition from the primary state through the circulate state to the secondary state.
2 . The electronic circuit of claim 1 , wherein the coupled inductor is a transformer.
3 . The electronic circuit of claim 1 , wherein the primary winding and the secondary winding have opposite polarities.
4 . The electronic circuit of claim 1 , wherein the processing logic comprises a single controller configured to control the first, second, and third switches.
5 . A power converter comprising a plurality of the electronic circuit of claim 1 , wherein respective outputs of the flyback converters of the plurality of electronic circuit are provided in a plurality of interleaved phases.
6 . The power converter of claim 5 , wherein, at any given time, at least one phase of the plurality of interleaved phases is in the secondary state, delivering current to the output.
7 . The electronic circuit of claim 1 , wherein each of the first, second, and third switches comprises a respective metal oxide silicon field effect transistor (MOSFET).
8 . The electronic circuit of claim 1 , wherein the primary winding of the coupled inductor is supplied with a pre-bias current.
9 . The electronic circuit of claim 1 , wherein the flyback converter further includes:
an output capacitor coupled to a second end of the secondary winding.
10 . A continuous-mode flyback converter, comprising:
a transformer having a primary winding and a secondary winding;
a first switch having a first input terminal, a first output terminal, and a first control terminal, wherein the first input terminal is coupled to a voltage input terminal and the first output terminal is coupled to a first end of the primary winding;
a second switch having a second input terminal, a second output terminal, and a second control terminal, wherein the second input terminal is coupled to a second end of the primary winding;
a third switch having a third input terminal, a third output terminal, and a third control terminal, wherein the third input terminal is coupled to a first end of the secondary winding;
wherein the continuous-mode flyback converter is configured to transition between three different switch states, the three switch states including:
a primary state wherein the first and second switches are on and current increases in the primary winding of the transformer,
a circulate state wherein only one of the first and second switches is on and current circulates in the primary winding of the transformer, and
a secondary state wherein both the first and second switches are off, the third switch is on, and current flows from the secondary winding of the transformer into an output of the continuous-mode flyback converter; and
a processing logic configured to automatically control a respective state of each of the first, second, and third switches, wherein the processing logic is configured to transition the flyback converter between the three switch states, and is configured to transition from the primary state through the circulate state to the secondary state.
11 . The continuous-mode flyback converter of claim 10 , wherein each of the first, second, and third switches comprises a respective metal oxide silicon field effect transistor (MOSFET).
12 . The continuous-mode flyback converter of claim 10 , further comprising:
a resistor-capacitor (RC) snubber including a snubber resistor and a snubber capacitor, wherein the RC snubber is coupled to the first end of the secondary winding.
13 . The continuous-mode flyback converter of claim 10 , further comprising:
an output capacitor coupled to a second end of the secondary winding.
14 . A method for converting a DC input voltage to a DC output voltage, the method comprising:
transitioning a continuous-mode flyback converter between three different switch states using a processing logic, wherein the continuous-mode flyback converter includes a transformer, two primary side switches, and one secondary side switch, and the three respective switch states include:
a primary state wherein the two primary side switches are on and current increases in a primary side of the transformer;
a circulate state wherein only one of the two primary side switches is on and current circulates in the primary side of the transformer; and
a secondary state wherein the two primary side switches are off, the one secondary side switch is on, and current flows from a secondary side of the transformer into an output of the continuous-mode flyback converter;
wherein the processing logic is configured to automatically control a respective state of each of the two primary side switches and the one secondary side switch, and to transition from the primary state through the circulate state to the secondary state.
15 . The method for converting the DC input voltage to the DC output voltage of claim 14 , the method further comprising:
interleaving a respective output of each of a plurality of the continuous-mode flyback converters of claim 14 .