JP2000287451A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a power supply to realize a low power factor even during power saving period with a small load current. SOLUTION: An AC power supply 1 of the AC 100 V system and AC 200 V system is rectified by a rectifying circuit 2, an output voltage of this rectifying circuit 2 is compared with the preset reference voltage with a comparing means, and only when an output of the rectifying circuit 2 is compared to determine as lower than the reference voltage with this comparing means, the rectifying circuit 2 and smoothing circuit 4 are connected with a switch and an output voltage smoothed with the smoothing circuit 4 is outputted to the load 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a power supply device,
In particular, the present invention relates to a power supply device capable of accepting AC power input of AC100V system and AC200V system.

[0002]

2. Description of the Related Art A conventional power supply unit can continuously respond to AC power supply of AC 100 V system and AC 200 V system, and as shown in FIG.
The rectifying circuit includes a rectifying circuit including a diode 6, a diode 7, a diode 8, and a diode 9 for rectifying the AC power supply 1, and a smoothing capacitor 10. As shown in FIG.
The voltage between both ends of the smoothing capacitor 10 increases in accordance with the voltage of the AC power supply 1, and is maximum in the case of the AC 200 V system.

Further, the conventional power supply device switches between AC 100 V system and AC 200 V system AC power supply input, and A
In the case of C100V system, double voltage rectification and smoothing
As shown in FIG. 8, an AC power supply 1 for supplying power, a diode 6, a diode 7 for rectifying the AC power supply 1, a diode 7, and a diode A rectifier circuit composed of a diode 8 and diodes 9, smoothing capacitors 10 and 11, and an input voltage of the AC power supply 1 are detected, and the circuit is connected in the case of a 100V AC system, and is switched off in the case of a 200V AC system. It is composed of a circuit 21.

[0004] In this example of the power supply device, as shown in FIG.
In the case of 0V system, the rectified voltage of about 2
Double the voltage, that is, the equivalent voltage of AC200V system.
From the standpoint of power saving, during standby when the load current is very small, power loss depends on voltage rather than current, so the higher the AC input voltage or rectified voltage, the higher the power loss was there.

[0005]

However, since the conventional power supply unit continuously responds to AC power supply of AC 100 V system and AC 200 V system, the voltage provided to the subsequent circuit depends on the AC input voltage. And the power loss at the time of power saving also increases according to the input voltage.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power supply device which realizes a low power loss even at the time of power saving where a load current is very small.

[0007]

In order to solve the above-mentioned problems, a power supply according to the present invention comprises an AC100V system and an AC2.
A rectifier circuit for rectifying a 00V AC power supply to output an output voltage, a smoothing circuit for smoothing an output voltage output from the rectifier circuit, and comparing an output voltage of the rectifier circuit with a preset reference voltage. And a switch circuit having a switch for connecting the rectifier circuit and the smoothing circuit only when the output voltage of the rectifier circuit is lower than the reference voltage by the comparator. And

[0008]

Next, a power supply device according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a power supply device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of the power supply device according to the first embodiment of the present invention.

FIG. 3 is a voltage waveform diagram according to the first embodiment of the present invention.

As shown in FIGS. 1 to 3, a power supply according to a first embodiment of the present invention has
Rectifier circuit 2 of diode bridges 6, 7, 8, 9 for rectifying 200V AC power supply 1 and outputting an output voltage, smoothing circuit 4 for smoothing the output voltage output from rectifier circuit 2, and rectifier circuit Means for comparing the output voltage of the rectifier circuit 2 with a preset reference voltage, and connects the rectifier circuit 2 and the smoothing circuit 4 only when the output voltage of the rectifier circuit 2 is compared with the reference voltage by the comparator means. And a load 5 to which the output voltage smoothed by the smoothing circuit 4 is provided.

The switch circuit 3 includes a constant voltage diode 14 for detecting an output voltage of the rectifier circuit 2 and a voltage dividing resistor 1.
2, 1 and the transistor 1 for stopping the operation of the transistor 14 for connecting the rectifying circuit 2 and the smoothing capacitor 6 when the voltage becomes equal to or higher than the Zener voltage of the constant voltage diode 14.
5 and 16 and resistors 17 and 18.

Next, the operation of the power supply according to the first embodiment of the present invention will be described with reference to the drawings.

The operation of the power supply device according to the first embodiment of the present invention, as shown in FIGS. 1 to 3, is as follows. First, after the AC power supply 1 is rectified by the rectification circuit 2 and smoothed by the smoothing circuit 4, The voltage is divided by the resistors 12 and 13 and
If the Zener value is less than or equal to, the transistor 15 of the switch circuit 2 does not operate, so that the transistor 18 operates and the transistor 19 also operates, and the rectifier circuit 2 and the smoothing circuit 4 are connected.

Second, when the voltage divided by the resistors 12 and 13 is equal to or greater than the Zener value of the constant voltage diode 14, the transistor 15 of the switch circuit 2 operates, the transistor 18 does not operate, and the transistor 19 does not operate. Does not operate, the rectifier circuit 2 and the smoothing circuit 4 are cut off. When the voltage of the rectified voltage rises to the Zener voltage of the constant voltage diode 14, the rectifier circuit 2 and the smoothing circuit 4 are cut off, and When the voltage drops below the Zener voltage of the constant voltage diode 14 in the process of voltage drop, an operation of connecting the rectifier circuit 2 and the smoothing circuit 4 is performed.

Third, when the voltage cut off by the switch circuit 2 is set to be equal to or lower than the rectified voltage of the AC 100 V system, the rectifier circuit is connected to the zener voltage of the constant voltage diode 14 as described above under all AC power supply input conditions. 2 and the smoothing circuit 4 are interrupted, and the rectified voltage is maintained at a predetermined voltage set by the resistors 12 and 13 and the constant voltage diode 14.

Fourth, when the voltage cut off by the switch circuit 2 is set to be higher than the rectified voltage of the AC 100 V system and lower than the rectified voltage of the AC 200 V system, the upper limit of the rectified voltage is determined by the resistors 12 and 13 and the constant voltage diode 14. , Is maintained at a predetermined voltage set in advance, and becomes the lower limit value when the AC input voltage is the lowest.

Therefore, the rectifier circuit 2 is controlled by the voltage preset by the resistors 12 and 13 and the constant voltage diode 14.
And the smoothing circuit 4 are interrupted, and the voltage applied to the smoothing circuit is suppressed to a predetermined voltage value.

Next, a power supply device according to a second embodiment of the present invention will be described with reference to the drawings.

FIG. 4 is a circuit diagram of a power supply device according to a second embodiment of the present invention.

As shown in FIG. 4, the operation of the power supply device according to the second embodiment of the present invention is as follows. First, after the AC power supply 1 is rectified by the rectifier circuit 2 and smoothed by the smoothing circuit 4, the resistor 1
2 and 13, the reference voltage from the shunt regulator is input to the comparator and compared with the voltage divided by the resistors 12 and 13. When the divided voltage is smaller than the reference voltage, the comparison is performed. Since the transistor does not output and the transistor 15 does not operate, the transistors 18 and 19 operate, and the rectifier circuit 2 and the smoothing circuit 4 are connected.

Second, as a result of the comparison, if the voltage divided by the resistors 12 and 13 is higher than the reference voltage, the comparator outputs, the transistor 15 operates and the transistor 18 does not operate. Since the transistor 19 does not operate, the rectifier circuit 2 and the smoothing circuit 4 are shut off. When the voltage divided by the resistors 12 and 13 exceeds the reference voltage in the process of increasing the rectified voltage, the rectifier circuit 2 and the smoothing circuit 4 are disconnected. The circuit 4 is shut off, and when the voltage divided by the resistors 12 and 13 falls below the reference voltage in the process of decreasing the rectified voltage, the rectifier circuit 2
And the smoothing circuit 4 are connected.

Therefore, the rectifying circuit 2 and the smoothing circuit 4 are set at a voltage preset by the resistors 12 and 13 and the reference voltage.
Are interrupted, and the voltage applied to the smoothing circuit is suppressed to a predetermined voltage value as in the power supply device according to the first embodiment of the present invention.

Next, a power supply device according to a third embodiment of the present invention will be described with reference to the drawings.

FIG. 5 is a circuit diagram of a power supply device according to a third embodiment of the present invention.

The operation of the power supply according to the third embodiment of the present invention is such that the reference voltage of the power supply according to the second embodiment of the present invention is a system using a constant voltage diode.
As shown in (1), first, the AC power supply 1 is rectified by the rectifier circuit 2, smoothed by the smoothing circuit 4, and then divided by the resistors 12 and 13.

Second, a reference voltage from a constant voltage diode is input to the comparator and compared with the voltage divided by the resistors 12 and 13. If the voltage divided by the resistors 12 and 13 is smaller than the reference voltage as a result of the comparison, the comparator does not output and the transistor 15 does not operate, so that the transistor 18 operates and the transistor 19 operates. The rectifier circuit 2 and the smoothing circuit 4 are connected.

Third, as a result of the comparison, if the voltage divided by the resistors 12 and 13 is higher than the reference voltage, the comparator outputs, the transistor 15 operates, and the transistor 18 does not operate. Since the transistor 19 does not operate, the rectifier circuit 2 and the smoothing circuit 4 are shut off. When the voltage divided by the resistors 12 and 13 exceeds the reference voltage in the process of increasing the rectified voltage, the rectifier circuit 2 and the smoothing circuit 4 are disconnected. When the circuit 4 is cut off and the voltage divided by the resistors 12 and 13 falls below the reference voltage in the process of decreasing the rectified voltage, the rectifier circuit 2
And the smoothing circuit 4 are connected.

Therefore, the rectifier circuit 2 and the smoothing circuit 4 are set at a voltage preset by the resistors 12 and 13 and the reference voltage.
Is interrupted, and the voltage applied to the smoothing circuit is suppressed to a predetermined voltage value, similarly to the power supply devices according to the first and second embodiments of the present invention.

[0031]

As described above, according to the power supply device of the present invention, the connection between the rectifier circuit and the smoothing circuit connected to the AC power supply of 100 V AC and 200 V AC is performed by the switch circuit, and the output of the rectifier circuit is output. Only when the voltage exceeds a predetermined value, to cut off the connection between the rectifier circuit and the smoothing circuit,
The upper limit of the DC voltage output to the subsequent stage is determined by a preset voltage, and a voltage lower than the voltage after rectification and smoothing at the time of AC 200 V input can be obtained, so that the power loss can be reduced during standby when the load current becomes very small. effective.

[Brief description of the drawings]

FIG. 1 is a block diagram of a power supply device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of the power supply device according to the first embodiment of the present invention.

FIG. 3 is a voltage waveform diagram of the power supply device according to the first embodiment of the present invention.

FIG. 4 is a circuit diagram of a power supply device according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram of a power supply device according to a third embodiment of the present invention.

FIG. 6 is a circuit diagram of a conventional power supply device.

FIG. 7 is a voltage waveform diagram of a conventional power supply device.

FIG. 8 is a circuit diagram of a conventional power supply device.

FIG. 9 is a voltage waveform diagram of a conventional power supply device.

[Explanation of symbols]

 Reference Signs List 1 AC power supply 2 Rectifier circuit 3 Switch circuit 4 Smoothing circuit 5 Load 6, 7, 8, 9 Diode 10, 11 Capacitor 12, 13, 16, 17 Resistor 14, 23 Constant voltage diode 15, 18, 20 Transistor 21 Switching circuit 22 Shunt regulator

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomoya Kusunose 1-4-24 Shiromi, Chuo-ku, Osaka-shi, Osaka Within NEC Home Electronics Co., Ltd. (72) Inventor Jiro Miyamoto Shiromi, Chuo-ku, Osaka-shi, Osaka No. 1-4-24 NEC Home Electronics Co., Ltd. F-term (reference) 5H006 CA01 CA07 CB01 CC08 DA04 DB01 DB05 DC05

Claims (1)

[Claims] 1. A rectifier circuit for rectifying an AC power supply of 100 VAC and 200 VAC to output an output voltage, a smoothing circuit for smoothing an output voltage output from the rectifier circuit, A switching circuit for comparing the rectifier circuit and the smoothing circuit only when the output voltage of the rectifier circuit is lower than the reference voltage by the comparator means; A power supply device comprising: