Back to results
US RE37,898 E1Granted
Self-oscillating switching power supply with output voltage regulated from the primary side
AssigneeSTMicroelectronics S.r.l.
InventorGiordano Seragnoli
Life of this patent
Estimating the term…
Abstract
Regulation of the output voltage of a power supply employing a flyback-type self-oscillating DC—DC converter employing a transformer. The primary winding circuit of the transformer senses a current recirculation loop for discharging the energy cyclically stored in an auxiliary winding of the self-oscillation loop of the converter such as to represent a replica of the circuit of the secondary winding of the transformer and by summing a signal representative of the level of the energy stored in the auxiliary winding with a drive signal on a control node of a driver of the power switch of the converter.
Claims32
A self-oscillating, DC—DC converter, comprising:
- a transformer having a primary winding coupled to a primary circuit and a secondary winding coupled to a secondary circuit, said primary circuit including a first switch, functionally connected in series with the primary winding, having a first terminal thereof coupled to an input node;
- a sensing resistance functionally connected between said first switch and a common potential node of the circuit, said first switch being driven by a self-oscillation circuit composed of at least an auxiliary winding having a first and a second terminal magnetically coupled to said primary winding and a first capacitor connected between a control element of said first switch and an intermediate connection node between said auxiliary winding and said first capacitor;
- a second switch device capable of shortcircuiting said control element of deactivating said first switch to said common potential node when a current through the primary winding reaches a preestablished level;
- at least a second capacitor connected between a second terminal of said auxiliary winding and said common potential node;
- at least a diode having an anode coupled to said common potential node and a cathode coupled to said intermediate connection node;
- and
- at least a zener diode connected between said second terminal of said auxiliary winding and a control element of said second switch device.
4 more elements
A DC—DC voltage regulating circuit, comprising:
- an input voltage terminal;
- a first switch;
- a primary winding serially coupled between said input voltage terminal and said first switch;
- a secondary winding magnetically coupled to said primary winding;
- a sensing resistance serially coupled between said first switch and a common potential node;
- and
- a self-oscillation circuit coupled to a first control terminal of said first switch, wherein said self-oscillation circuit comprises an auxiliary winding magnetically coupled to said primary winding and having a first node and a first intermediate node;
- a first capacitive element coupled between said first node and said common potential node;
- a first diode having an anode coupled to said common potential node and a cathode coupled to said first intermediate node;
- a second capacitive element coupled between said first intermediate node and said first control terminal of said first switch;
- a first resistive element coupled between said input voltage terminal and said first control terminal of said first switch;
- a second switch device coupled between said first control terminal of said first switch and said common potential node and having a second control terminal coupled to a second intermediate node connecting said first switch and said sensing resistance;
- and
- a second diode coupled between said first node and said second control terminal.
11 more elements
A power-supply circuit, comprising:
- an output terminal;
- a transformer having a primary winding, having an auxiliary winding, and having a secondary winding coupled to the output terminal and operable to generate an output voltage on the output terminal;
- a device having a variable conductivity and operable to control a flow of current through the primary winding;
- and
- a regulation circuit including the auxiliary winding and a sense element coupled to the device and operable to conduct the current the regulation circuit operable to maintain the output voltage at a constant or an approximately constant level by coupling a regulation signal to the sense element during a period in which the device has a high conductivity.
2 more elements
A power-supply circuit, comprising:
- an input terminal;
- an output terminal operable to provide an output voltage;
- a primary transformer winding coupled to the input terminal;
- a secondary transformer winding coupled to the output terminal, the secondary transformer winding being electrically isolated from and magnetically coupled to the primary transformer winding;
- a switching device having a first drive terminal coupled to the primary transformer winding, having a second drive terminal, and having a control terminal;
- and
- a regulation circuit comprising,
- an auxiliary transformer winding that is electrically isolated from the secondary transformer winding and that is magnetically coupled to the primary and secondary transformer windings,
- a sense element coupled to the second drive terminal of the switching device, and
- wherein the regulation circuit is operable to regulate the output voltage by,
- generating a regulation signal, and
- coupling the regulation signal to the sense element while energy is being stored in the primary transformer winding.
9 more elements
A method for regulating an output voltage, the method comprising:
- storing flyback energy by allowing a charging current to flow through a primary transformer winding and through a sense element during a charging period;
- controlling the duration of the charging period by coupling a regulating signal to the sense element during the charging period;
- generating a primary flyback voltage across the primary transformer winding after the charging period;
- generating an auxiliary flyback voltage across an auxiliary transformer winding in response to the primary flyback voltage;
- generating the regulating signal from the auxiliary flyback voltage;
- generating a secondary flyback voltage across a secondary transformer winding in response to the primary flyback voltage;
- and
- generating the output voltage from the secondary flyback voltage.
5 more elements
A power-supply circuit, comprising:
- an input terminal;
- a supply terminal;
- a regulated output terminal operable to provide an output voltage;
- a primary transformer winding coupled to the input terminal;
- a secondary transformer winding coupled to the regulated output terminal, the secondary transformer winding being electrically isolated from and magnetically coupled to the primary transformer winding;
- a switching device having a first drive terminal coupled to the primary transformer winding, having a second drive terminal, and having a control terminal;
- and
- a regulation circuit comprising,
- an auxiliary transformer winding that has first and second terminals, that is electrically isolated from the secondary transformer winding, and that is magnetically coupled to the primary and secondary transformer windings,
- a sense element coupled between the supply terminal and the second drive terminal of the switching device,
- a diode coupled between the supply terminal and the first terminal of the auxiliary winding,
- a capacitor coupled between the supply terminal and the second terminal of the auxiliary winding,
- a transistor having a first drive terminal coupled to the supply terminal, a second drive terminal coupled to the control terminal of the switching device, and
- a control terminal coupled to the second drive terminal of the switching device, and
- a zener diode coupled between the second terminal of the auxiliary transformer winding and the control terminal of the transistor.
12 more elements
A method for generating a regulated output voltage, the method comprising:
- storing flyback energy by allowing a charging current to flow through a primary transformer winding during a charging period;
- controlling the duration of the charging period by combining a regulating current with the charging current during the charging period;
- generating a primary flyback voltage across the primary transformer winding after the charging period;
- generating an auxiliary flyback voltage across an auxiliary transformer winding in response to the primary flyback voltage;
- generating the regulating current from the auxiliary flyback voltage;
- generating a secondary flyback voltage across a secondary transformer winding in response to the primary flyback voltage;
- and
- generating the regulated output voltage from the secondary flyback voltage.
5 more elements
Dependencies are inferred from the claim text.