Switching power supply device and electronic appliance therewith

Patent metadata

Field	Value
Publication number	US-9240717-B2
Application number	US-201214113241-A
Country	US
Kind code	B2
Filing date	Apr 19, 2012
Priority date	Apr 25, 2011
Publication date	Jan 19, 2016
Grant date	Jan 19, 2016

Abstract

Provided is a switching power source device in which fluctuation of the switching frequency can be suppressed without impairing the advantages of a non-linear control system. A switching power source device is provided with: switching control units of non-linear control type that generate an output voltage (out) from an input voltage (IN) by performing ON/OFF control of switching elements in accordance with the results of comparing a feedback voltage (FB) and reference voltage (REF); and an ON time setting unit that monitors switching voltage (SW) appearing at one end of the switch terminals, and sets the ON time (Ton) of the switching element in the switching control units based on the duty of the switching voltage (SW).

First claim

The invention claimed is:

1. A switching power supply device comprising:
a switching controller of a non-linear control type, for generating an output voltage from an input voltage by performing on/off control of a switching element according to a result of comparison of a feedback voltage with a reference voltage; and
an on-period setter for monitoring a switch voltage appearing at an end of the switching element so as to set, based on a duty of the switch voltage, an on-period of the switching element in the switching controller,
wherein the on-period setter increases the on-period of the switching element the higher the duty of the switch voltage is, and decreases the on-period of the switching element the lower the duty of the switch voltage is,
wherein the on-period setter includes:
a first voltage generation circuit for generating a first voltage according to charging/discharging operation of a capacitor;
a second voltage generation circuit for generating a second voltage according to the duty of the switch voltage; and
a first comparator for generating a first control signal by comparing the first voltage with the second voltage,

wherein the first voltage generation circuit includes:
a constant-current source for generating a constant charge current that does not depend on the input voltage;
a capacitor connected to the constant-current source; and
a charge/discharge switch for switching between charging and discharging of the capacitor according to the on/off control of the switching element,

wherein the second voltage generation circuit includes:
a level shifter for shifting a level of the switch voltage;
a buffer for shaping a waveform of an output of the level shifter; and
a filter for generating the second voltage by smoothing an output of the buffer, and

wherein the constant-current source and the level shifter operate by being fed with a same internal supply voltage.

2. The switching power supply device according to claim 1 , wherein the second voltage generation circuit includes a current feedback portion for offsetting the second voltage according to an output current of the switching element.

3. The switching power supply device according to claim 2 , wherein the current feedback portion includes:
a differential amplifier for differentially amplifying a voltage between both ends of the switching element; and
an adder for adding an output of the differential amplifier to the second voltage.

4. The switching power supply device according to claim 1 , wherein the switching controller includes:
a feedback voltage generator for generating the feedback voltage by dividing the output voltage;
a reference voltage generator for generating the reference voltage;
a second comparator for generating a second control signal by comparing the feedback voltage with the reference voltage;
a flip-flop yielding an output signal of which a logical level switches according to the first and second control signals; and
a driver for performing the on/off control of the switching element according to the output signal of the flip-flop.

5. An electronic appliance comprising the switching power supply device according to claim 1 as a power supply for supplying electric power to different sections in the appliance.

6. The electronic appliance according to claim 5 , wherein the electronic appliance is a television receiver.

7. The electronic appliance according to claim 5 , wherein the electronic appliance is a set-top box.

8. The electronic appliance according to claim 1 wherein the level shifter is arranged to receive the switch voltage and to generate as its output a voltage signal that is driven to pulsate between the internal supply voltage and a predetermined voltage.

9. The electronic appliance according to claim 8 wherein the predetermined voltage is ground.

Assignees

• Hara Hideo
• Higashida Yoshio
• Murakami Kazuhiro
• Rohm Co Ltd

Inventors

• Hara Hideo
• Higashida Yoshio
• Murakami Kazuhiro

Classifications

• H02M3/158 Primary

  including plural semiconductor devices as final control devices for a single load · CPC title

• H02M3/156 Primary

  with automatic control of output voltage or current, e.g. switching regulators · CPC title