JP2000333454A - Dc power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To intermittently supply a minimum necessary AC to reduce or completely remove power loss in a power supply by turning the AC input on or off, in matching with the quantity of consumed power in a load. SOLUTION: This equipment is provided with an AC switch SSR control circuit 7. When a decrease in the load power is detected and it is deemed that a load is in a stand-by state, and the AC switch SSR is turned off. While the load is in a stand-by state, the input voltage of a DC-DC converter 4 is monitored. When the input voltage drops to a prescribed value, the AC switch SSR is turned on for a prescribed period of time. When the increase in the load power is detected, the AC switch SSR is turned on continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply, and more particularly, to a rectifier / smoothing unit, a DC-DC converter unit, and a DC stabilizing unit after inputting AC power to a noise filter unit via an AC switch. And a DC power supply for supplying a DC voltage, which has been sequentially converted, to a load.

[0002]

2. Description of the Related Art While there has been a call for reducing power consumption during standby to prevent global warming, conventional energy-saving measures have been to reduce load power and power conversion loss. Since it is supplied, a small amount of loss power is consumed in the filter section, the smoothing section, and the like.

FIG. 4 is a diagram showing a conventional DC power supply device. In the figure, an AC power is supplied from an AC power supply 1 via an AC switch SSR that can be turned on and off, a noise filter unit 2, a rectification / smoothing unit 3, a DC-DC converter unit 4,
After passing through the C stabilizing unit 5 sequentially, it is converted into a DC voltage and supplied to the load unit 6.

[0004] The noise filter section 2 is provided to suppress noise generation to a predetermined level or less. A DC power supply device using a switching regulator, such as the illustrated DC-DC converter unit 4, includes a switching circuit, and thus can be a noise generation source that generates conduction noise and radiation noise. When this is connected to AC power supply 1,
The noise generated at the noise source is A
The noise returns to the C power supply side as conduction noise, and at that time, radiation noise from the AC cord also occurs. In order to suppress such noise, conventionally, for example, a noise filter unit 2 including a choke coil L and a capacitor C as exemplified above is used.
The noise filter unit 2 is provided with an AC switch SSR even when the load power consumption during standby is small.
As long as is ON, a leak current flows and consumes a small amount of power.

In the rectifying / smoothing unit 3 for rectifying and smoothing AC into DC by the full-wave rectifier circuit 10, similarly, even when the load power consumption during standby is small, the charging current flows through the capacitor C1. Consumes very little power.

[0006] The DC-DC converter unit 4 uses the DC voltage rectified and smoothed by the rectification / smoothing unit 3 as an input voltage.
Switching is performed by a switching element (transistor Tr in the drawing) and supplied to the primary side of a transformer T, and the secondary side output of the transformer T is rectified by a diode D2 to be converted into a direct current again. Such a DC-DC converter unit 4 is provided with snubber units 8 and 9 as illustrated. The snubber sections 8 and 9 are circuits that suppress a surge voltage applied to the switching transistor Tr. Similarly, even when the load power consumption during standby is small, a leak current flows through the snubber sections 8 and 9 as well. Consumes very little power. The DC stabilizing unit 5 is a circuit unit that smoothes the direct current rectified by the diode D2 with the choke coil L2 and the capacitor C2.

Thus, the AC switch SSR is turned on,
By turning off, AC power is supplied to the device power supply unit, and D
Stable DC power is supplied to the load via the C-DC converter 4. However, in the conventional power supply device, the noise filter unit 2, the rectification / smoothing unit 3, the DC-
A voltage is applied to the snubber sections 8 and 9 of the DC converter section 4, and a leakage current or a charging current flows, thereby consuming power.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and supplies the minimum necessary AC power intermittently by turning on and off the AC input according to the power consumption of the load section. The purpose is to reduce or eliminate all power loss inside the power supply.

[0009]

According to the DC power supply of the present invention, after inputting AC power to a noise filter section 2 through an AC switch SSR, a rectifying / smoothing section 3, a DC-DC converter section 4, and a DC The DC voltage converted through the stabilizing unit 5 is supplied to the load. An AC switch SSR control circuit 7 is provided to control the AC switch SSR to be off when it is determined that the load is standby by detecting a decrease in the load power, and to perform the DC-DC during the load standby.
The input voltage of the converter unit 4 is monitored, and when the input voltage drops to a predetermined value, the AC switch SS
R is turned on, and when the load power rises again, this is detected and the AC switch SSR is continuously turned on. As a result, the present invention prevents the power consumption due to the leakage current or the charge current flowing by intermittently turning on the AC switch SSR when the load power consumption during standby is small.

Further, the AC switch SSR control circuit provided in the DC power supply of the present invention detects a decrease in load power and determines that the load is in standby.
In addition to controlling the operation of the DC-DC converter unit 4 to OFF together with the switch SSR, the load standby timer
The on / off operation of the AC switch SSR and the DC-DC converter unit 4 is repeated, and when the load power rises again, this is detected and the AC switch SSR and DC
-The DC converter unit 4 is continuously turned on.

Further, the DC power supply of the present invention detects a decrease or an increase in load power by detecting a current flowing through a switching element (transistor Tr) for controlling the DC-DC converter section.

[0012]

FIG. 1 is a diagram illustrating a circuit embodying a DC power supply device of the present invention. In the figure, AC
Power is supplied from an AC power supply 1 through an AC switch SSR that can be turned on and off, for example, a noise filter unit 2 including a choke coil L and a capacitor C as illustrated, and a rectifying / smoothing unit that rectifies and smoothes AC to DC. 3. The DC voltage rectified and smoothed by the rectification / smoothing unit 3 is switched by a switching element (transistor Tr in the drawing) and supplied to the primary side of a transformer T. The secondary side output of the transformer T is supplied to a diode D2. The DC voltage is converted into a DC voltage and supplied to a load unit through a DC-DC converter unit 4 for rectifying the DC voltage again, and a DC stabilizing unit 5. The basic operation is the same as that of the prior art described above with reference to FIG.

The illustrated DC power supply is thus
By turning on and off the switch SSR, AC power is supplied to the device power supply unit, and stable DC power is supplied to the load unit 6 via the DC-DC converter unit 4. When the circuit 7 is not operating,
Even when the load power consumption during standby is small, when the AC switch SSR is in the ON state, a voltage is applied to the noise filter unit 2, the rectification / smoothing unit 3, the snubber units 8 and 9 of the DC-DC converter unit 4, etc. A current or charge current flows and consumes power.

According to the present invention, when it is determined that the load power is reduced, that is, it is during standby, the AC switch SSR is turned off,
C Supply of electric power is stopped. This reduction in load power is illustrated in FIG.
This can be performed by monitoring the current flowing through the switching transistor Tr for controlling the DC-DC converter section by the photodiode PC-D and detecting a decrease in the current. At this time, in the first example, DC-
The DC converter unit 4 continues to operate and supplies appropriate DC power to the load. The voltage across the rectifying and smoothing capacitor C1, which is the input voltage of the DC-DC converter unit 4, decreases,
Immediately before dividing the low voltage start point of the C-DC converter section 4,
By turning on the AC switch SSR, the operation of the DC-DC converter unit 4 is continued. The leak current of the noise filter unit 2 and the charging current of the smoothing capacitor C1 during the stop of the AC supply become unnecessary.

In FIG. 1, a current monitor is used to connect a current flowing through a switching transistor Tr to a resistor R in series with the switching transistor Tr.
, And is converted into light and detected by a photodiode PC-D constituting a photocoupler. This in turn controls the phototransistor PC-T that makes up the photocoupler, which in turn controls the AC switch SSR. This operation will be further described with reference to FIG.

FIG. 2 is a diagram showing operation waveforms of each section in the first example described above. In the figure, when the current flowing through the uppermost switching transistor Tr falls below the reference value, it is determined that the apparatus is in the standby state. This is detected by turning off the photocoupler PC. When the photocoupler PC is turned off, the AC switch SSR is turned off, and the supply of AC power is stopped. As a result, the voltage Vc1 across the capacitor C1 of the rectifying / smoothing unit 3, that is,
The operating voltage of the DC-DC converter unit 4 starts to decrease,
Detecting that this has decreased to a predetermined value, the AC switch SSR is turned on via the SSR control circuit 7, and AC power is supplied for a predetermined fixed time. During this fixed time, the output voltage of the DC-DC
As shown in the figure, the C voltage is selected so as to be maintained at a substantially constant value. When the load section restarts, this is because the current flowing through the switching transistor Tr has risen above the reference value, and the photodiode PC-
D returns to the normal operating state, that is, the continuous ON state of the AC switch SSR.

FIG. 3 shows a capacitor C1 of the rectifying / smoothing unit 3.
It is a figure for explaining operation in the 2nd example which controls using a time switch instead of detecting voltage Vc1 of both ends. As described above, the standby state is detected by the photocoupler PC when the current flowing through the switching transistor Tr drops below the reference value. Thereafter, the time switch repeats the off-on-off of the AC switch SSR by the time switch until the load section operates again. At the same time, in this second example,
The DC-DC converter unit 4 also repeats the operation-stop. D
The stop of the C-DC converter unit 4 can be performed by controlling the switching transistor Tr to be off. The time switch is set so that the DC voltage to the load does not fluctuate even if the DC-DC converter unit 4 repeatedly operates and stops. In this manner, when the AC supply is intermittently stopped, the DC-DC converter section 4 also intermittently stops operation, and stops the leakage current of the noise filter section and the smoothing capacitor C.
In addition to the charge current of 1, the power loss of the snubber of the DC-DC converter 4 is also reduced.

Then, when the load section operates again, similarly,
This is because the current flowing through the switching transistor Tr has risen above the reference value, and the photodiode P
CD, the normal operating state, ie, AC
The switch SSR returns to the continuous ON state.

[0019]

According to the present invention, the minimum necessary AC supply is intermittently performed by turning on and off the AC input in accordance with the power consumption of the load unit. This has the effect of making it possible to reduce or eradicate all the loss power inside the power supply.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a circuit embodying a DC power supply device of the present invention.

FIG. 2 is a diagram showing operation waveforms of each unit in the first example.

FIG. 3 is a diagram for explaining an operation in a second example in which control is performed using a time switch instead of detecting the voltage Vc1 across the capacitor C1 of the rectifying / smoothing unit 3 in FIG. 1;

FIG. 4 is a diagram showing a conventional DC power supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 Noise filter part 3 Rectifier / smoothing part 4 DC-DC converter part 5 DC stabilization part 6 Load part 7 SSR control circuit 8 Snubber part 9 Snubber part 10 Full wave rectification circuit

Claims (3)

[Claims] 1. After AC power is input to a noise filter unit via an AC switch, a DC voltage converted through a rectifying / smoothing unit, a DC-DC converter unit, and a DC stabilizing unit is sequentially supplied to a load. In the DC power supply, the AC switch is turned off when it is determined that the load is standby by detecting a decrease in load power, and the input voltage of the DC-DC converter unit is monitored during the load standby. When the input voltage falls to a predetermined value, the AC switch is controlled to be turned on for a predetermined time, and when the load power rises again, this is detected and the A is detected.
A DC power supply device, comprising: an AC switch control circuit for continuously turning on a C switch. 2. An AC power is input to a noise filter unit via an AC switch, and then a DC voltage converted through a rectifying / smoothing unit, a DC-DC converter unit, and a DC stabilizing unit is supplied to a load. In the DC power supply, when it is determined that the load standby state is detected by detecting a decrease in load power, the AC switch and the DC-DC
The operation of the converter unit is controlled to be off, and the AC switch and the DC-D
The operation of the C converter section is repeatedly turned on and off, and when the load power rises again, this is detected and the A
A DC power supply, comprising: a C switch and an AC switch control circuit that continuously controls the DC-DC converter to be turned on. 3. The DC power supply device according to claim 1, wherein the detection of the decrease or increase of the load power is performed by detecting a current flowing through a switching element for controlling the DC-DC converter unit.