Switching power supply device having failure protection function, and method for controlling the same

Patent metadata

Field	Value
Publication number	US-11095226-B2
Application number	US-201916591482-A
Country	US
Kind code	B2
Filing date	Oct 2, 2019
Priority date	Oct 3, 2018
Publication date	Aug 17, 2021
Grant date	Aug 17, 2021

Abstract

A switching power supply device includes a voltage conversion transformer, a primary-side control semiconductor device, a rectification and smoothing circuit, an output voltage detection circuit, a failure detection circuit, and a switch. The primary-side control semiconductor device generates a driving signal which controls a switching element connected to a primary winding of the transformer. The rectification and smoothing circuit is connected to a secondary winding of the transformer. The output voltage detection circuit detects a secondary-side output voltage of the transformer and transmits a feedback signal corresponding to the output voltage to the primary-side control semiconductor device through an insulated signal transmitter. The failure detection circuit detects a failure on a secondary side of the transformer. The switch cuts off a current flowing to the insulated signal transmitter if the failure detection circuit detects a failure.

First claim

What is claimed is:

1. A switching power supply device comprising:
a voltage conversion transformer including an auxiliary winding;
a primary-side control semiconductor device that generates a driving signal which controls turn-on and turn-off of a switching element connected in series to a primary winding of the voltage conversion transformer;
a rectification and smoothing circuit that is connected to a secondary winding of the voltage conversion transformer;
an output voltage detection circuit that detects a secondary-side output voltage of the voltage conversion transformer and transmits a feedback signal corresponding to the secondary-side output voltage to the primary-side control semiconductor device through an insulated signal transmitter;
a failure detection circuit including a current detection terminal that detects a secondary-side current of the voltage conversion transformer and a voltage detection terminal that detects the secondary-side output voltage; and
a switch that cuts off a current flowing to the insulated signal transmitter,
wherein:
the primary-side control semiconductor device comprises:
a first external terminal to which a voltage corresponding to the feedback signal supplied from the output voltage detection circuit is input;
a second external terminal to which a voltage induced in the auxiliary winding or a voltage obtained by dividing the induced voltage is input; and
an overvoltage detection circuit including a first voltage comparator that detects whether a voltage of the first external terminal is higher than a first predetermined threshold voltage and a second voltage comparator that detects whether a voltage of the second external terminal is higher than a second predetermined threshold voltage,

in a case where the first voltage comparator and the second voltage comparator determine that the voltage of the first external terminal and the voltage of the second external terminal exceed the first threshold voltage and the second threshold voltage, respectively, the overvoltage detection circuit generates a signal to stop generation of the driving signal, and
in a case where the failure detection circuit detects an overvoltage or an overcurrent on the secondary side of the voltage conversion transformer, the switch is controlled such that the current flowing to the insulated signal transmitter is cut off and the voltages input to the first external terminal and the second external terminal rise.

2. The switching power supply device according to claim 1 , wherein:
the overvoltage detection circuit further includes a timer circuit that measures a predetermined time, and
the overvoltage detection circuit generates the signal to stop generation of the driving signal for the switching element in a case where the first voltage comparator and the second voltage comparator determine that the voltage of the first external terminal and the voltage of the second external terminal exceed the first threshold voltage and the second threshold voltage, respectively, when the timer circuit measures a predetermined time after the switching element is turned off.

3. The switching power supply device according to claim 1 , wherein:
the insulated signal transmitter comprises a photocoupler,
the switch is connected in series to a photodiode forming the photocoupler, and
in a case where the failure detection circuit detects the overvoltage or the overcurrent on the secondary side of the voltage conversion transformer, the failure detection circuit turns off the switch such that a current flowing to the photodiode is cut off.

4. The switching power supply device according to claim 1 , further comprising:
a switch that is connected between the rectification and smoothing circuit and a secondary-side output terminal,
wherein the switch is turned off by the failure detection circuit when the current flowing to the insulated signal transmitter is cut off.

5. The switching power supply device according to claim 1 , wherein:
the rectification and smoothing circuit includes a MOS transistor as a rectification element,
a synchronous rectification control circuit that controls turn-on and turn-off of the MOS transistor based on a drain voltage and a source voltage of the MOS transistor is provided on the secondary side of the voltage conversion transformer,
the failure detection circuit is an open state detection circuit that detects an open state of a drain terminal and/or a gate terminal of the MOS transistor based on the drain voltage and the source voltage of the MOS transistor, and
in a case where the open state detection circuit detects the open state, the failure detection circuit generates and outputs a signal to cut off the current flowing to the insulated signal transmitter.

6. The switching power supply device according to claim 1 , further comprising:
a temperature detection element on the secondary side of the voltage conversion transformer,
wherein, in a case where it is detected that temperature is equal to or greater than a predetermined value based on a signal from the temperature detection element, the failure detection circuit generates and outputs a signal to cut off the current flowing to the insulated signal transmitter.

7. The switching power supply device according to claim 1 , wherein:
the failure detection circuit has a terminal that receives a signal notifying occurrence of a failure from an external device, and
in a case where the signal notifying the occurrence of the failure is received, the failure detection circuit generates and outputs a signal to cut off the current flowing to the insulated signal transmitter.

8. A switching power supply device comprising:
a voltage conversion transformer including an auxiliary winding;
a primary-side control semiconductor device that generates a driving signal which controls turn-on and turn-off of a switching element connected in series to a primary winding of the voltage conversion transformer;
a rectification and smoothing circuit that is connected to a secondary winding of the voltage conversion transformer;
an output voltage detection circuit that detects a secondary-side output voltage of the voltage conversion transformer and transmits a feedback signal corresponding to the secondary-side output voltage to the primary-side control semiconductor device through an insulated signal transmitter;
a failure detection circuit including a current detection terminal that detects a secondary-side current of the voltage conversion transformer and a voltage detection terminal that detects the secondary-side output voltage; and
a switch that cuts off a current flowing to the insulated signal transmitter,
wherein:
the primary-side control semiconductor device comprises:
a first external terminal to which a voltage corresponding to the feedback signal supplied from the output voltage detection circuit is input;
a second external terminal to which a voltage induced in the auxiliary winding or a voltage obtained by dividing the induced voltage is input; and
an overvoltage detection circuit including a first voltage comparator that compares a voltage of the first external terminal with a first predetermined threshold voltage and a second voltage comparator that compares a voltage of the second external terminal with a second predetermined threshold voltage, and

in a case where the failure detection circuit detects that the secondary-side current or the secondary-side output voltage of the voltage conversion transformer exceeds a predetermined value, the switch is controlled such that the current flowing to the insulated signal transmitter is cut off, and outputs of the first voltage comparator and the second voltage comparator are inverted to stop the

Assignees

• Arima Satoshi
• Matsuda Hiroki
• Mitsumi Electric Co Ltd

Inventors

• Arima Satoshi
• Matsuda Hiroki

Classifications

• H02M3/33592 Primary

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

• H02M3/33523

  with galvanic isolation between input and output of both the power stage and the feedback loop · CPC title

• H02H7/1213

  for DC-DC converters · CPC title

• H02H1/0007

  concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445) · CPC title

• H02H7/1227

  responsive to abnormalities in the output circuit, e.g. short circuit · CPC title