JPH06319260A - Switching power supply apparatus - Google Patents

Abstract

PURPOSE:To increase the conversion efficiency of a switching power supply apparatus in information equipment at the time of a light load. CONSTITUTION:This switching power supply apparatus is provided with an input power supply, a transformer 13, a main switching element 18 connected to the input power supply and the transformer, smoothing diodes 14, 15 on the output side of the transformer and a control part 19 for detecting the output voltage and controlling the main switching means in duty and is constituted of a means for changing the switching frequency of the duty control means to not more than 1/2 at the time of low power consumption as compared to that at the time of a rated power. With the switching power supply apparatus, the efficiency of the power supply of information equipment at the time of a pause state is increased to realize the low consumption of a current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply device for information equipment.

[0002]

2. Description of the Related Art In information equipment, especially portable equipment,
Since the secondary battery is used to supply electric power, low current consumption is required. Also, due to the emergence of environmental problems, it is necessary to reduce the power consumption of information equipment. As a solution to this problem, as the current consumption of the main circuit is reduced, the operation of the microprocessor with the highest current consumption in the main circuit is constantly monitored,
Processing is performed to reduce current consumption as much as possible by lowering the clock frequency according to the required operating capacity. However, the efficiency of the conventional switching power supply unit is reduced when the current consumption is low, which has been an obstacle to the practical reduction of the current consumption.

[0003]

In a normal switching power supply device, its switching frequency is fixed by the time constant of the control circuit. At present, the switching frequency is shifting to a higher frequency due to the demand for miniaturization of equipment. However, as the switching frequency is increased, the efficiency of the power supply device is reduced as shown in FIG.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a switching power supply device capable of improving the efficiency under a light load.

[0005]

The present invention for achieving the above object provides an input power source, a transformer, a main switching element connected to the input power source and the transformer, and a smoothing diode on the output side of the transformer. And a smoothing choke connected to a smoothing diode, and a control unit for detecting the output voltage and controlling the duty of the main switching means. The duty is controlled by a control signal from an electronic device that monitors power consumption outside the power supply device. It is characterized in that it is constituted by means for varying the switching frequency in the control unit to ½ or less when the power consumption is low compared to the rated power.

[0006]

With the above-described structure, the present invention supplies high-output power by high-frequency switching as before in the vicinity of the rated output of the power supply device (during steady operation), lowers the switching frequency when the power consumption is low, and Improve efficiency.

Since the power supply of the power supply is proportional to the switching frequency, the power supply decreases when the frequency is lowered according to the present invention, but the operating current is small when the main circuit is in the idle state, so sufficient operating power is obtained. Can be supplied.

The power supply of the present invention uses the secondary smoothing choke having the DC superposition characteristic shown in FIG. The reason for this is that in a forward type power supply generally used for switching power supplies, the inductance required for the secondary side smoothing choke is expressed by the following equation. L = {D (1-D) (1 + K) / 2f (1-K) Io} * (Ns / Np) * Vi (Formula 1) K = (Ivs / Ips) Here, L: inductance D: switching duty Ratio f: Switching frequency Io: Output current Np: Number of primary windings of transformer Ns: Number of secondary windings of transformer Vi: Input voltage Ivs: Minimum value of smoothing choke coil Ips: Maximum value of smoothing choke coil

According to (Equation 1), when the switching frequency is lowered when the current consumption is low, it is necessary to increase the inductance of the secondary side smooth choke. Therefore, in the present invention, the smoothing choke having the DC superposition characteristic shown in FIG. 3 suppresses the output ripple voltage when the switching frequency is low, that is, when the current consumption is low. A choke with this characteristic can be achieved with a swinging choke coil.
Alternatively, a plurality of chokes corresponding to the rated power consumption and the low power consumption may be combined.

[0010]

【Example】

(Embodiment 1) FIG. 1 is a schematic block diagram of Embodiment 1 of the present invention. The switching power supply device of the present embodiment is connected to an input power supply, a transformer 13, a main switching element 18 connected to the input power supply and the transformer, smoothing diodes 14 and 15 on the output side of the transformer, and a smoothing diode. It also comprises a smoothing choke 16 and a control section 19 for detecting the output voltage and controlling the duty of the main switching means. The duty control unit 19 detects the voltage on the secondary side and transmits an optimum duty control signal to the main switch element 18 to control it so as to match the preset voltage. Reference numeral 21 denotes a control unit in the main body circuit, which constantly monitors the power consumption state of the main body and transmits a signal indicating a steady state or a rest state to 20. The switching frequency control unit 20 controls the switching frequency of the duty control unit 19 based on a signal from the control unit 21 in the main circuit. The smooth choke 16 is a secondary smooth choke according to claim 3.

FIG. 4 shows the output current and its efficiency characteristic of the switching power supply device according to the present invention. Compared with the conventional switching power supply device, the efficiency is improved in the vicinity of 1 A when the current consumption is low.

(Second Embodiment) FIG. 2 is a schematic block diagram of a second embodiment of the present invention. The switching power supply device of the present embodiment is connected to an input power supply, a transformer 24, a main switching element 32 connected to the input power supply and the transformer, smoothing diodes 25 and 26 on the output side of the transformer, and a smoothing diode. It comprises a smoothed choke 27 and a controller 30 for detecting the output voltage and controlling the duty of the main switching means. The duty control unit 30 detects the voltage on the secondary side, transmits an optimum duty control signal to the main switch element 32 so as to match the preset voltage, and controls the main switch element 32.
Reference numeral 28 denotes a secondary-side current detection unit, which monitors the power consumption of the main body circuit and outputs a signal 31 indicating whether the main body circuit is in a steady state or a rest state.
Communicate to. A switching frequency control unit 31 controls the switching frequency of the duty control unit 30 based on a signal from the secondary side current detection unit 28. Smooth chalk 2
7 is the secondary side smooth choke according to claim 3.

FIG. 4 shows the output current and its efficiency characteristic of the switching power supply device according to the present invention. Compared with the conventional switching power supply device, the efficiency is improved in the vicinity of 1 A when the current consumption is low.

[0014]

With the switching power supply according to the present invention,
The efficiency of the power supply in the hibernation state of the information equipment equipped with this is improved, and low current consumption is realized.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment.

FIG. 2 is a diagram showing a second embodiment.

FIG. 3 is a diagram showing an example of DC superimposition characteristics of a smooth choke according to claim 3;

FIG. 4 is a diagram showing efficiency examples depending on load currents of a conventional product and a power supply device according to the present invention.

FIG. 5 is a diagram showing an example of switching frequency and efficiency in a switching power supply.

[Explanation of symbols]

 11,22 Primary side smoothing diode 12,17,23,29 Capacitor 13,24 Transformer 14,15 Secondary side smoothing diode 16,27 Smoothing choke 18,32 Main switch element 19,30 Duty control section 20,31 Switching frequency Control unit 21 Control unit in main circuit 25, 26 Diode 28 Secondary side current detection unit

Claims (3)

[Claims] 1. An input power supply, a transformer, a main switching element connected to the input power supply and the transformer, a smoothing diode on the output side of the transformer, a smoothing choke connected to the smoothing diode, and an output voltage. A control unit for detecting the duty of the main switching means and controlling the duty of the main switching means by a control signal from an electronic device that monitors the power consumption outside the power supply device, and the switching frequency in the duty control portion when the power consumption is lower than the rated power consumption. A switching power supply device characterized in that it is constituted by means for changing to 1/2 or less. 2. The switching power supply device according to claim 1, wherein in the means for varying the switching frequency, the control signal is input from a current detection section for detecting an output current. 3. The switching power supply device according to claim 1, wherein the smoothing choke has an inductance that is at least twice as large as that during normal power consumption at a low output current, that is, at a low frequency switching frequency.