SWITCHING POWER SUPPLY DEVICE

• US 20140146238A1
• Filed: 10/22/2013
• Published: 05/29/2014
• Est. Priority Date: 10/23/2012
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Murakami, Kazuhiro
• Granted Patent: US 8,970,790 B2
• Time in Patent Office: Days
• US Class Current: 348/730
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 3/1563 without using an external clock H02M3/158 takes precedence
• CPC Class Codes: H04N 5/63 Generation or supply of power specially adapted for television receivers
• CPC Class Codes: Y02B 70/10 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

Abstract

A switching power supply device has a switching controller adapted to generate an output voltage from an input voltage by turning on and off a switching device by a non-linear control method according to a comparison signal and a timer signal, a main comparator adapted to generate the comparison signal by comparing a feedback voltage based on the output voltage with a predetermined reference voltage, a timer adapted to output the timer signal as a one-shot pulse when a predetermined fixed period elapses after the switching device is turned from on to off or vice versa, and a reverse current detector adapted to detect a reverse current to the switching device to forcibly turn off the switching device. The timer and the reverse current detector are turned on at a pulse edge in the comparison signal, and are turned off on ending their respective operation.

Claims

1. A switching power supply device comprising:

a switching control portion that generates an output voltage from an input voltage by performing on/off control of a switch device using a non-linear control method in accordance with a comparison signal and a timer signal;

a main comparator that compares a feedback voltage corresponding to the output voltage and a predetermined reference voltage with each other to generate the comparison signal;

a timer portion that performs a one-shot output of the timer signal at a time point when a predetermined fixed period elapses after the on/off of the switch device is switched; and

a backward flow detection portion that detects a backward flow for the switch device to forcibly turn off the switch device;

wherein

the timer portion and the backward flow detection portion are turned on at a time point when a pulse edge of the comparison signal occurs and turned off at a time point when operation of each of the timer portion and backward flow detection portion is completed.

2. The switching power supply device according to claim 1, further comprising:

a delay portion that performs a one-shot output of a delay comparison signal at a time point when a predetermined delay period elapses after the pulse edge of the comparison signal occurs;

wherein

the switching control portion receives an input of the delay comparison signal instead of the comparison signal and performs the on/off control of the switch device using the non-linear control method in accordance with the delay comparison signal and the timer signal.

3. The switching power supply device according to claim 2, wherein

the delay portion neglects the comparison signal for a predetermined mask period after performing the one-shot output of the delay comparison signal.

4. The switching power supply device according to claim 2, wherein

the timer portion and the backward flow detection portion undergo on/off control when necessary in a sleep mode and are kept in a normally turned-on state in a non-sleep mode.

5. The switching power supply device according to claim 4, wherein

the delay portion performs a one-shot output of the delay comparison signal in the sleep mode and performs a through-output of the comparison signal as the delay comparison signal in the non-sleep mode.

6. The switching power supply device according to claim 4, wherein

the backward flow detection portion operates on a drive current larger than usual in the sleep mode and operates on a usual drive current in the non-sleep mode.

7. The switching power supply device according to claim 1, further comprising:

a startup comparator that compares the feedback voltage and a predetermined threshold value voltage with each other to generate a startup signal;

wherein

the timer portion and the backward flow detection portion receive an input of the startup signal instead of the comparison signal and are turned on at a time point when a pulse edge of the startup signal occurs before the pulse edge of the comparison signal occurs.

8. The switching power supply device according to claim 1, further comprising:

a pulse distribution portion that distributes two pulses, which occur in the comparison signal thanks to variable control of the reference voltage, to a first comparison signal and a second comparison signal;

wherein

the timer portion and the backward flow detection portion receive an input of the first comparison signal instead of the comparison signal and are turned on at a time point when a pulse edge of the first comparison signal occurs before a pulse edge of the second comparison signal occurs; and

the switching control portion receives an input of the second comparison signal instead of the comparison signal and performs the on/off control of the switch device using the non-linear control method in accordance with the second comparison signal and the timer signal.

9. The switching power supply device according to claim 1, wherein

the switch device is connected between a terminal of an inductor and an application terminal for a ground voltage;

and

during an on-period of the switch device, the backward flow detection portion compares a switch voltage appearing at a terminal of the switch device and the ground voltage with each other to generate a zero-cross detection signal.

10. The switching power supply device according to claim 9, further comprising:

a latch portion that generates a skip signal which is set to a first logic level at a pulse edge of the zero-cross detection signal and reset to a second logic level at the pulse edge of the comparison signal;

wherein

the switching control portion forcibly turns off the switch device during a period when the skip signal is kept at the first logic level.

11. A television comprising:

a tuner portion that selects a broadcast signal for a desired channel from a reception signal;

a decoder portion that generates an image signal and a voice signal from the broadcast signal selected by the tuner portion;

a display portion that outputs the image signal as an image;

a speaker portion that outputs the voice signal as a voice;

an operation portion that receives a user operation;

an interface portion that receives an external input signal;

a control portion that controls comprehensively operation of each of the portions; and

a power supply portion that supplies electric power to each of the portions;

wherein

the power supply portion includes the switching power supply device according to claim 1.

12. The switching power supply device according to claim 3, wherein

the timer portion and the backward flow detection portion undergo on/off control when necessary in a sleep mode and are kept in a normally turned-on state in a non-sleep mode.

13. The switching power supply device according to claim 12, wherein

the delay portion performs a one-shot output of the delay comparison signal in the sleep mode and performs a through-output of the comparison signal as the delay comparison signal in the non-sleep mode.

14. The switching power supply device according to claim 5, wherein

the backward flow detection portion operates on a drive current larger than usual in the sleep mode and operates on a usual drive current in the non-sleep mode.

15. The switching power supply device according to claim 12, wherein

the backward flow detection portion operates on a drive current larger than usual in the sleep mode and operates on a usual drive current in the non-sleep mode.

16. The switching power supply device according to claim 13, wherein

the backward flow detection portion operates on a drive current larger than usual in the sleep mode and operates on a usual drive current in the non-sleep mode.