Power supply apparatus

Abstract

A rectifying circuit (18) converts inputted AC power to DC power. An inverter circuit (22) converts the DC power to high-frequency power in accordance with a switching control signal applied thereto from a control circuit (50). A voltage transformer (24) voltage-transforms the voltage of the high-frequency power. An output-side rectifying circuit (40) rectifies the voltage-transformed power. An output detecting circuit (34) detects the magnitude of the voltage of the rectified power, and a signal representative of the detected voltage is applied to the control circuit (50). The control circuit (50) generates such a switching control signal as to make the rectified power have a predetermined value. The value of the voltage from the rectifying circuit (18) is detected by an input detecting circuit (62), and a signal representative of the detected voltage is applied to the control circuit (50). The control circuit (50) controls the operation of the inverter circuit (22) in accordance with the detected voltage representative signal from the input detecting circuit (62) and the saturation magnetic characteristic of the voltage-transformer (24).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block circuit diagram of a power supply apparatus according to one embodiment of the present invention.

FIGS. 2A through 2D are various waveforms for use in explaining the operation of the power supply apparatus shown in FIG. 1.

FIGS. 3A through 3D are waveforms, corresponding to the ones shown in FIGS. 2A through 2D, respectively, developed at various points in a power supply apparatus corresponding to the one shown in FIG. 1 but not including an input detecting circuit.

FIG. 4 is a block circuit diagram according to another embodiment of the present invention.

Claims

1. A power supply apparatus comprising: converting means for converting input AC power to DC power;switching means receiving said DC power and performing switching operation in accordance with a switching control signal, for converting said DC power to high-frequency power;a voltage transformer for transforming a voltage of said high-frequency power;rectifying means for rectifying the power as voltage-transformed by said voltage transformer;first detecting means for detecting a magnitude of said rectified power, a voltage of said rectified power, or a current of said rectified power and developing a first detection signal representative of the detected magnitude of power, voltage or current;control means receiving said first detection signal and developing said switching control signal to cause the magnitude of power, voltage or current as detected by said first detecting means to have a predetermined value; andsecond detecting means for detecting a voltage value of said DC power and developing a second detection signal representative of the detected voltage value;said control means receiving also said second detection signal, and controlling the switching operation of said switching means in accordance with said second detection signal and a saturation magnetic characteristic of said voltage transformer.

2. The power supply apparatus according to claim 1, wherein: current flows from said switching means to said voltage transformer when said switching means is ON; andsaid control means controls a time period during which said switching means is ON, in accordance with said second detection signal.

3. The power supply apparatus according to claim 2, wherein: said switching control signal causes said switching means to perform switching operation by the pulse width modulation system; andsaid control means controls a pulse width of said switching control signal during the time period during which said switching means is ON, in accordance with said second detection signal.

4. The power supply apparatus according to claim 1, wherein said control means comprises: error signal generating means for generating an error signal representative of the difference between said first detection signal and a predetermined reference signal;triangular waveform generating means for generating a triangular waveform signal; andPWM comparing means for comparing said triangular waveform signal with a threshold value, which is a larger one of said second detection signal and said error signal, and generating a PWM control signal for making said switching means ON when said triangular waveform signal is equal to or larger than said threshold value.

5. A power supply apparatus comprising: converting means for converting input AC power to DC power;switching means receiving said DC power and performing switching operation in accordance with a switching control signal, for converting said DC power to high-frequency power;a voltage transformer for transforming a voltage of said high-frequency power;rectifying means for rectifying the power as voltage-transformed by said voltage transformer;first detecting means for detecting a magnitude of said rectified power, a voltage of said rectified power, or a current of said rectified power and developing a first detection signal representative of the detected magnitude of power, voltage or current;control means receiving said first detection signal and developing said switching control signal to cause the magnitude of power, voltage or current as detected by said first detecting means to have a predetermined value; andsecond detecting means for detecting a voltage value of said AC power and developing a second detection signal representative of the detected voltage value;said control means receiving also said second detection signal, and controlling the switching operation of said switching means in accordance with said second detection signal and a saturation magnetic characteristic of said voltage transformer.

6. The power supply apparatus according to claim 5, wherein: current flows from said switching means to said voltage transformer when said switching means is ON; andsaid control means controls a time period during which said switching means is ON, in accordance with said second detection signal.

7. The power supply apparatus according to claim 6, wherein: said switching control signal causes said switching means to perform switching operation by the pulse width modulation system; andsaid control means controls a pulse width of said switching control signal during the time period during which said switching means is ON, in accordance with said second detection signal.

8. The power supply apparatus according to claim 5, wherein said control means comprises: error signal generating means for generating an error signal representative of the difference between said first detection signal and a predetermined reference signal;triangular waveform generating means for generating a triangular waveform signal; andPWM comparing means for comparing said triangular waveform signal with a threshold value, which is a larger one of said second detection signal and said error signal, and generating a PWM control signal for making said switching means ON when said triangular waveform signal is equal to or larger than said threshold value.