Switching control circuit and power supply circuit

Patent metadata

Field	Value
Publication number	US-2021111631-A1
Application number	US-202017001168-A
Country	US
Kind code	A1
Filing date	Aug 24, 2020
Priority date	Oct 15, 2019
Publication date	Apr 15, 2021
Grant date	—

Abstract

A switching control circuit for controlling a power supply circuit having a transformer and a transistor. The switching control circuit is configured to operate based on a power supply voltage that corresponds to a voltage from an auxiliary coil of the transformer. The switching control circuit includes a drive signal output circuit that outputs a drive signal that corresponds to an operation mode of the power supply circuit, the operation mode including a burst mode, a drive circuit that performs switching of the transistor based on the drive signal outputted by the drive signal output circuit, and a control circuit that outputs, to the drive signal output circuit, a control signal for operating the power supply circuit in the burst mode, when a first transition condition or a second transition condition is satisfied, the first transition condition including time as a condition, and the second transition condition not including time as a condition.

First claim

What is claimed is:

1 . A switching control circuit for controlling a power supply circuit that includes
a transformer including a primary coil provided on a primary side, a secondary coil provided on a secondary side, and an auxiliary coil magnetically coupled to the primary coil or the secondary coil, and a transistor that controls a current of the primary coil, and that is configured to generate an output voltage of a target level on the secondary side, the power supply circuit having a load connected to an output thereof, the switching control circuit being configured to operate based on a power supply voltage that corresponds to a voltage from the auxiliary coil of the power supply circuit, and control switching of the transistor, the switching control circuit comprising: a drive signal output circuit that outputs a drive signal that corresponds to an operation mode of the power supply circuit, the operation mode including a burst mode; a drive circuit that performs the switching of the transistor based on the drive signal outputted by the drive signal output circuit; and a control circuit that outputs, to the drive signal output circuit, a control signal for operating the power supply circuit in the burst mode, when a first transition condition or a second transition condition is satisfied, the first transition condition including time as a condition, the second transition condition not including time as a condition.

2 . The switching control circuit according to claim 1 , wherein
the first transition condition is that a state in which the load is a light load continues for a predetermined time period.

3 . The switching control circuit according to claim 1 , wherein
the second transition condition is that the power supply voltage drops below a first level.

4 . The switching control circuit according to claim 3 , wherein
the second transition condition is that the load is a light load and the power supply voltage drops below the first level.

5 . The switching control circuit according to claim 1 , wherein
the control circuit determines whether the load is a light load based on a feedback voltage corresponding to the output voltage and/or a voltage corresponding to input power on the primary side.

6 . The switching control circuit according to claim 1 , wherein
the control circuit causes the drive circuit to stop driving the transistor, when the output voltage rises above the target level and a feedback voltage corresponding to the output voltage reaches a second level.

7 . The switching control circuit according to claim 1 , wherein
the operation mode includes a normal mode, and a plurality of burst modes including said burst mode, the control circuit sends the control signal to the drive signal output circuit, to thereby cause the drive signal output circuit to output the drive signal for operating the power supply circuit in one of the burst modes that corresponds to power consumption of the load, when the power consumption of the load decreases during an operation of the power supply circuit in the normal mode, and in the normal mode, when the power consumption of the load increases during the operation of the power supply circuit in one of the burst modes in which the load has lowest power consumption.

8 . The switching control circuit according to claim 7 , wherein
the control circuit causes the drive signal output circuit to output the drive signal for operating the power supply circuit in the normal mode, at a time of transition to the normal mode from the one burst mode in which the load has the lowest power consumption.

9 . A switching control circuit for controlling a power supply circuit that includes
a transformer including a primary coil provided on a primary side, a secondary coil provided on a secondary side, and an auxiliary coil magnetically coupled to the primary coil or the secondary coil, and a transistor that controls a current of the primary coil, and that is configured to generate an output voltage of a target level on the secondary side, the power supply circuit having a load connected to an output thereof, the switching control circuit being configured to operate based on a power supply voltage that corresponds to a voltage from the auxiliary coil of the power supply circuit, and control switching of the transistor, the switching control circuit comprising: a drive signal output circuit that outputs a drive signal that corresponds to an operation mode of the power supply circuit, the operation mode including a normal mode and a plurality of burst modes; a drive circuit that performs the switching of the transistor based on the drive signal outputted by the drive signal output circuit; and a control circuit that sends a control signal to the drive signal output circuit, to thereby cause the drive signal output circuit to output the drive signal for operating the power supply circuit
in one of the burst modes that corresponds to power consumption of the load, when the power consumption of the load decreases during an operation of the power supply circuit in the normal mode, and
in the normal mode, when the power consumption of the load increases during an operation of the power supply circuit in one of the burst modes in which the load has lowest power consumption.

10 . The switching control circuit according to claim 9 , wherein
the control circuit causes the drive signal output circuit to output the drive signal for operating the power supply circuit in the normal mode, at a time of transition to the normal mode from the one burst mode in which the load has the lowest power consumption.

11 . A power supply circuit comprising:
a transformer that includes a primary coil provided on a primary side, a secondary coil provided on a secondary side, and an auxiliary coil magnetically coupled to the primary coil or the secondary coil; a transistor that controls a current of the primary coil; and a switching control circuit that operates based on a power supply voltage that corresponds to a voltage from the auxiliary coil, and controls switching of the transistor, the power supply circuit being configured to generate an output voltage of a target level on the secondary side, the switching control circuit including a drive signal output circuit that outputs a drive signal that corresponds to an operation mode of the power supply circuit, the operation mode including a burst mode, a drive circuit that performs the switching of the transistor based on the drive signal outputted by the drive signal output circuit, and a control circuit that outputs, to the drive signal output circuit, a control signal for operating the power supply circuit in the burst mode, when a first transition condition or a second transition condition is satisfied, the first transition condition including time as a condition, the second transition condition not including time as a condition.

12 . A power supply circuit having a load connected to an output thereof, comprising:
a transformer that includes a primary coil provided on a primary side, a secondary coil provided on a secondary side, and an auxiliary coil magnetically coupled to the primary coil or the secondary coil; a transistor that controls a current of the primary coil; and a switching control circuit that operates based on a power supply voltage that corresponds to a voltage from the auxiliary coil, and controls switching of the transistor, the power supply circuit being configured to generate an output voltage of a target level on the secondary side, the switching control circuit including a drive signal output circuit that outputs a drive signal that cor

Assignees

• Fuji Electric Co Ltd

Inventors

• Kobayashi Yoshinori
• Chen Jian

Classifications

• H02M3/33569 Primary

  having several active switching elements (H02M3/3353 takes precedence) · CPC title

• H02M1/0035 Primary

  using burst mode control · CPC title

• H02M3/33571

  Half-bridge at primary side of an isolation transformer · CPC title

• H02M3/01

  Resonant DC/DC converters · CPC title

• Y02B70/10

  Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes · CPC title