JPH06319259A - Switching power supply apparatus - Google Patents

Abstract

PURPOSE:To economize in power by intermittently supplying a DC which is gained by rectifying an input AC power supply with a main switch to the primary side of a transformer and detecting a DC which is rectified on the secondary side of the transformer to determine whether it is in the state of a steady-state load or in a pause state and to set up a duty ratio to not more than 1/2 at the time of the pause state. CONSTITUTION:A DC which is gained by rectifying 22 an AC power supply is fed to the primary side of a transformer 24 through a main switch element 25. It is converted into a predetermined voltage by the transformer 24 and then rectified by diodes 26, 27 to be supplied to an external load through a smoothing choke 28. An output current on the secondary side is detected 30 and then delivered to a frequency divider 32 to input the secondary output voltage to a duty control part 31. The oscillation frequency of an oscillator 33 is applied to the gate of a main switch element 35 through the frequency divider 32 and the duty control part 31. A load current is always monitored in a secondary current detecting part 30, thereby lowering the oscillation frequency of the oscillator 33 at the time of a pause state to lower the duty ratio of the main switch element 25 down to not more than 1/2 of that at the time of a steady-state load. Thereby, the consumed power is reduced.

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 The present invention is required to reduce current consumption in information equipment, especially portable equipment, because a secondary battery supplies electric power. In addition, due to the manifestation of environmental problems,
It is necessary to reduce the power consumption of information equipment. As a solution to this problem, to reduce the current consumption of the main body circuit, the operation of the microprocessor, which consumes the most current in the main body circuit, is constantly monitored, and the clock frequency is lowered according to the required operating capacity to suppress the current consumption as much as possible. Such a process is performed. 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 the main switching element of the switching power supply unit mounted on the information equipment,
As shown in FIG. 4, a current flows when voltage is applied to the element at turn-on and turn-off, resulting in excessive loss. Since this loss exists even at a low output current, the efficiency is lowered.

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]

SUMMARY OF THE INVENTION The present invention for achieving the above object comprises an input power source, a transformer or a boost coil or a step-down coil, and a main power source connected to the input power source and the transformer or the boost coil or the step-down coil. A switching element, a control unit that detects the output voltage and duty-controls the main switching element, an oscillator that oscillates a rectangular wave signal that is duty-controlled, and a frequency divider that divides the signal from the oscillator, The rectangular signal input to the duty control unit is controlled by a control signal from an electronic device that monitors the power consumption outside the power supply unit. It is characterized by that.

[0006]

According to the present invention, the switching operation of the main switching element is intermittently operated at a low output current by the above-mentioned configuration, and the number of turn-on and turn-off within a fixed time is reduced to reduce the loss. The efficiency of the power supply device is improved by the loss reduction means at the time of this low output current (FIG. 5).

[0007]

【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 detects an input power supply, a transformer 13 or a step-up coil or a step-down coil, a main switching element 12 connected to the input power supply and a transformer, a step-up coil or a step-down coil, and an output voltage. Control unit 18 for duty-controlling the main switching element
And an oscillator 2 for oscillating a rectangular wave signal for duty control
0 and a frequency divider 19 for dividing the signal from the oscillator. The duty control unit 18 detects the voltage on the secondary side and transmits an optimum duty control signal to the main switch element 12 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 load state (rated load) or a rest load state (light load) to the frequency divider 19. The frequency divider 19 operates from the pulse oscillator 20 to the duty control unit 18 in response to a signal from the control unit 21 in the main circuit.
The switching pulse to is transmitted to the steady load state without being divided, and to the rest load state, the divided pulse shown in FIG. 5 is transmitted.

FIG. 3 shows the output current and its efficiency characteristics 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 detects an input power supply, a transformer 24 or a step-up coil or a step-down coil, a main switching element 25 connected to the input power supply and a transformer, a step-up coil or a step-down coil, and an output voltage. The main switching device is provided with a control unit 31 for duty control, an oscillator 33 for oscillating a rectangular wave signal for duty control, and a frequency divider 32 for dividing the frequency of the signal from the oscillator. The duty control unit 31 detects the voltage on the secondary side and transmits an optimum duty control signal to the main switch element 25 so as to match the preset voltage and controls the main switch element 25. Reference numeral 30 denotes a secondary side current detection unit that monitors the power consumption in the main body circuit and transmits a signal indicating that the main body circuit is in a steady state (rated load) or in a rest state (light load) to the frequency divider 32. The frequency divider 32 controls the switching pulse, and transmits the switching pulse from the pulse oscillator 33 to the duty control unit 31 to the steady load state without frequency division by the signal from the secondary side current detection unit 30. In the idle load state, the divided pulse shown in FIG. 5 is transmitted.

FIG. 3 shows the output current and its efficiency characteristics 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.

[0011]

According to the switching power supply device of the present invention, the efficiency of the power supply when the information equipment equipped with the switching power supply device is in the idle state is improved and the current consumption is reduced.

[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 efficiency according to load current of a conventional product and a power supply device according to the present invention.

FIG. 4 is a current, voltage applied to the main switching element,
It is a figure which shows the example of a loss waveform.

FIG. 5 is a diagram showing switching pulses in a steady load state and a rest load state.

[Explanation of symbols]

 10,22 Primary side smoothing diode 11,17,23,29 Capacitor 12,25 Main switch element 13,24 Transformer 14,15,26,27 Secondary side smoothing diode 16,28 Smoothing choke 18,31 Duty controller 19 , 32 Frequency divider 20, 33 Oscillator 21 Control section in main circuit 30 Secondary side current detection section

Claims (2)

[Claims] 1. An input power supply, a transformer, a step-up coil or a step-down coil, a main switching element connected to the input power supply and the transformer, the step-up coil or a step-down coil, and an output voltage to detect the main switching element. A control signal from an electronic device that includes a duty-controlled control unit, an oscillator that oscillates a duty-controlled rectangular wave signal, and a frequency divider that divides the signal from the oscillator, and that monitors power consumption outside the power supply device. Therefore, the rectangular signal input to the duty control unit is halved by the frequency divider when the power consumption is lower than that at the rated power.
A switching power supply device characterized in that it is configured by means for dividing the frequency below. 2. The switching power supply device according to claim 1, wherein the control signal is input to the frequency divider from a means for detecting an output current.