Switching power source apparatus and direct-current power source apparatus

Patent metadata

Field	Value
Publication number	US-10536089-B2
Application number	US-201916249018-A
Country	US
Kind code	B2
Filing date	Jan 16, 2019
Priority date	Jan 22, 2018
Publication date	Jan 14, 2020
Grant date	Jan 14, 2020

Abstract

A switching power source apparatus includes: a synchronous rectifier switching element for synchronous rectification constituted of an insulated-gate field-effect transistor; and a secondary-side control circuit including a detector circuit and a timer circuit. The secondary-side control circuit performs ON/OFF control of the synchronous rectifier switching element. The detector circuit monitors a voltage of a drain terminal of the synchronous rectifier switching element, and detects an abnormal state in which the voltage of the drain terminal is undetectable. The timer circuit starts up and measures a predetermined time in response to the detector circuit detecting the abnormal state. When the detector circuit detects the abnormal state, and the predetermined time elapses according to the timer circuit, the secondary-side control circuit outputs a detection signal indicating an abnormality to outside.

First claim

What is claimed is:

1. A switching power source apparatus comprising:
a transformer for voltage conversion;
a main switching element connected to a primary-side coil of the transformer in series;
a primary-side control circuit which performs ON/OFF control of the main switching element;
a synchronous rectifier switching element for synchronous rectification connected to a secondary-side coil of the transformer in series; and
a secondary-side control circuit which performs ON/OFF control of the synchronous rectifier switching element,
wherein:
the synchronous rectifier switching element comprises an insulated-gate field-effect transistor,
the secondary-side control circuit includes:
a detector circuit which monitors a voltage of a drain terminal of the synchronous rectifier switching element, and detects an abnormal state in which the voltage of the drain terminal is undetectable; and
a timer circuit which starts up and measures a predetermined time in response to the detector circuit detecting the abnormal state,

when the detector circuit detects the abnormal state, and the predetermined time elapses according to the timer circuit, the secondary-side control circuit outputs a detection signal indicating an abnormality,
the detector circuit includes:
a voltage dividing unit which divides the voltage of the drain terminal of the synchronous rectifier switching element;
a determination circuit which compares (i) a divided voltage obtained by the voltage dividing unit dividing the voltage of the drain terminal with (ii) a reference voltage of a predetermined potential, thereby determining the abnormal state; and
an AND circuit which receives an output signal of the determination circuit and an output signal of the timer circuit as an input,

the timer circuit starts measuring the predetermined time in response to the determination circuit determining that the abnormal state has occurred,
the voltage dividing unit includes a resistor element connected between a voltage monitoring terminal to which the voltage of the drain terminal of the synchronous rectifier switching element is input and a ground point, and
the switching power source apparatus further comprises a clamp circuit including a transistor which is provided between the voltage monitoring terminal and the ground point, and is connected to the resistor element in series.

2. The switching power source apparatus according to claim 1 , further comprising, on a secondary side of the transformer:
a signal sending unit which sends a signal corresponding to an output voltage of the secondary side to the primary-side control circuit; and
a current control unit which is connected to the signal sending unit in series and controls current that flows into the signal sending unit,
wherein:
the current control unit changes the current that flows into the signal sending unit in response to the detection signal output from the secondary-side control circuit, and
the primary-side control circuit detects a change in the signal sent by the signal sending unit, and stops the ON/OFF control of the main switching element.

3. The switching power source apparatus according to claim 1 , further comprising:
a switch unit provided between a terminal of the secondary-side coil of the transformer and a voltage output terminal which outputs a voltage rectified and smoothed on the secondary side, the switch unit supplying/blocking the rectified and smoothed voltage,
wherein the switch unit is ON/OFF controlled in response to the detection signal output from the secondary-side control circuit.

4. The switching power source apparatus according to claim 1 , wherein the secondary-side control circuit is configured as one of: (i) a semiconductor integrated circuit provided on one semiconductor chip, and (ii) a semiconductor device in stalled in one package.

5. A direct-current power source apparatus comprising:
the s witching power source apparatus according to claim 1 ;
a USB Type-C plug connected to an output terminal on a secondary side of the transformer;
a controller which controls the Type-C plug; and
a switch unit connected between a terminal of the secondary-side coil of the transformer and a power supply terminal of the Type-C plug,
wherein:
the detection signal output from the secondary-side control circuit is supplied to the controller, and
the controller controls the switch unit in response to the detection signal.

Assignees

• Hyugaji Takumi
• Kado Minoru
• Mitsumi Electric Co Ltd

Inventors

• Hyugaji Takumi
• Kado Minoru

Classifications

• H02M3/33592 Primary

  having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer · CPC title

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title

• G01R19/155

  Indicating the presence of voltage · CPC title

• H02M1/08

  Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters · CPC title

• H02M1/327

  against abnormal temperatures · CPC title