JPH09121475A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the voltage of the standby power supply of a standby power supply circuit. SOLUTION: By providing a backup means for keeping a standby voltage at a given value by a voltage obtained from a main power supply circuit 3 when failures such as a momentary power failure caused the drop of the standby voltage of a standby power supply circuit 7 while a main power supply circuit 3 is on, an operation voltage is supplied from the capacitor Cb of this backup means to the standby power supply circuit 7 via a discharging diode D.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device suitable for television receivers, audio equipment and the like.

[0002]

2. Description of the Related Art In a television receiver or the like, there is a part which always needs to be energized not only during operation / non-operation, but in addition to a main power supply circuit for obtaining a main power supply voltage required during operation, there is a standby voltage. A standby power supply circuit is provided. For example, turn on / off the internal microcomputer, infrared remote commander's light receiving part, and the main power supply.
The standby power supply is used for operations required when the main power supply is turned off, such as driving a relay switch for turning off. The standby power supply circuit is configured as a circuit unit that constantly generates a predetermined voltage as long as the power outlet plug of the device is connected to the commercial AC power supply, for example.

FIG. 3 shows an example of a standby power supply circuit.
By connecting the power outlet plug 20 to a commercial AC power source, for example, the AC 10 is connected to the primary side of the power transformer 23.
0 V is applied. The winding ratio of the power transformer 23 is set so as to output AC 24 V to the secondary side, for example.
The AC 24V obtained on the secondary side is converted into a direct current in the rectifying / smoothing circuit 24 by the bridge rectifying circuit and the smoothing capacitor, and is supplied to the regulator 25.

The regulator 25 is supplied with 24V DC
From this, a stabilized power supply voltage of DC 12 V is generated. The direct current 12V output from the regulator 25 is used as a drive voltage for a relay circuit that constitutes the starting switch 21 of the switching power supply circuit 22 that is the main power supply circuit, for example. When the user turns on the power, a microcomputer (not shown) supplies DC 12V to the relay circuit.
By controlling the drive voltage to be applied, the operation switch 21 is turned on and the switching power supply circuit 22 is activated. As a result, for example, the main power supply voltage is DC 12V.
A voltage is generated and supplied to each part.

In the standby power supply circuit, the DC 12V voltage output from the regulator 25 is further used as a stabilized power supply voltage of DC 5V in the regulator 26.
The capacitor C is arranged after each of the regulators 25 and 26 for removing high frequency noise components. The DC 5V from the regulator 26 is supplied as a standby power source for driving the microcomputer and the light receiving section for infrared signals.

[0006]

By the way, in the standby power supply circuit as in the above example, a voltage that is about twice as high as the required standby power supply voltage (12V and 5V) such as 24V on the secondary side of the power transformer 23. Is set to compensate for the reduced voltage of the AC power supply.

That is, even if the commercial AC power supply voltage drops, if it drops to some extent, the standby power supply voltage (12
V and 5V) to stabilize the operation of the device. However, this causes a problem that the power transformer 23 is inevitably increased in size and cost.

Further, when the AC power supply is momentarily cut off, noise is generated in the standby power supply voltage, which may lead to malfunction of the microcomputer, for example.

For example, FIG. 4A shows the voltage state at the output point (point A) of the regulator 25 when the AC power supply is intentionally momentarily cut off, and FIG. 4B shows it. The voltage state at the output point (point B) of the regulator 26 is shown. Although the voltage at the point A will momentarily drop from 12V due to the AC power supply being cut off, if the voltage at the point A drops to 5V or less, the 5V output of the regulator 26 becomes impossible, and as shown in FIG. Thus, a drop is also observed in the voltage at point B.

Such a change in the standby voltage causes malfunction such as resetting of the microcomputer. Such a malfunction particularly occurs while the device is turned on and is performing some operation (for example, television broadcast output), which means that the control of the operation is not normal, which is very preferable. Absent.

[0011]

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to make a power supply transformer in a standby power supply circuit compact and to stabilize the standby power supply voltage. .

In order to achieve the above object, a main power supply circuit section for obtaining a main power supply voltage and a standby power supply circuit section for supplying a necessary standby voltage not only for turning on / off the main power supply circuit section are provided, Provided is a backup means capable of maintaining the standby voltage at a predetermined voltage by the voltage obtained from the power supply circuit unit when the standby voltage drops in the standby power supply circuit unit while the main power supply circuit unit is turned on. did.

Further, the backup means connects the capacitor connected to the first potential point in the main power supply circuit section to the second potential point in the standby power supply circuit section via the discharging diode so as to connect to the second potential point. When the voltage at the potential point drops, the discharge operation from the capacitor is performed so that the voltage at the second potential point can be maintained.

According to the present invention, when the standby voltage drops due to momentary power failure or the like while the main power supply is on, the standby power supply circuit section is discharged from the capacitor of the backup means through the discharging diode. A current is supplied to maintain the operating voltage of the standby power supply circuit unit.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram of the power supply device of this example. When the power outlet plug 1 is connected to a commercial AC power source, AC 100V, for example, is applied to the primary side of the power transformer 4.

The power transformer 4 is, for example, AC15 on the secondary side.
It is a small-sized transformer whose winding ratio is set so as to output about V. The AC voltage obtained on the secondary side is a rectifying and smoothing circuit 5 using a diode bridge and a smoothing capacitor.
Is converted into a direct current and is supplied to the regulator 6. The regulator 6 generates a stabilized power supply voltage of DC 12V from the supplied voltage (DC 15V, for example). The direct current 12V output from the regulator 6 is used as a drive voltage of a relay circuit that constitutes the starting switch 3 of the switching power supply circuit 3 serving as a main power supply circuit, for example.

DC 12V output from the regulator 6
The voltage is further used as a regulated power supply voltage of DC 5V in the regulator 7. The capacitor C is arranged after each of the regulators 25 and 26 for removing high frequency noise components. 5V DC from the regulator 7 is supplied as a standby power supply for driving a microcomputer and a light receiving portion for infrared signals.

When the user turns on the equipment equipped with such a power supply device, the microcomputer controls the relay circuit to apply the DC 12V drive voltage obtained from the regulator 6. By doing so, the operation switch 2 is turned on, and the switching power supply circuit 3 is activated. As a result, for example, a DC 12V voltage is generated as the main power supply voltage and is supplied to each unit.
Further, in this example, the switching power supply circuit 3 also generates a voltage of DC 11V, and the line 9 is connected via the capacitor Cb.
The DC voltage of 11V is output to. The capacitor Cb has a large capacity of about 3300 μF, for example. The capacitor Cb and the output point (12 V potential point) of the regulator 6 shown as A in the figure are connected by the discharging diode D.

In such a power supply device, the regulator 6 serves as a standby power supply circuit section during the period when the switching power supply circuit 3 is off and also during the period when the switching power supply circuit 3 is driven to generate the DC12V and DC11V voltages. , 7 outputs DC12V and DC5V. Considering the period during which the switching power supply circuit 3 is driven, if the input voltage from the AC power source drops during this period, the AC voltage appearing on the secondary side of the power transformer 4 drops, and at this time, Depending on the voltage level of the secondary side of the power transformer 4, even the output voltage (point A voltage) from the regulator 6 may be lowered.

However, in the case of this example, the voltage at the point A decreases,
When the potential difference between the point A and the line 9 becomes the conduction potential difference of the diode D, the discharging operation of the capacitor Cb is performed, that is, the capacitor Cb functions as a power source for the point A and maintains the potential of the point A. As a result, the potential at the point B, which is the output point of the regulator 7 having the potential at the point A as the input voltage, is always stabilized, and the standby voltage for the microcomputer or the like can be stably supplied.

2 (a) and 2 (b) show the voltage states at points A and B when the AC power supply is repeatedly interrupted as in the case of FIG. As shown in FIG. 2 (a), by being backed up by the capacitor Cb, the voltage drop at the point A is reduced even if the AC power supply is interrupted, and the voltage at the point B is accordingly reduced as shown in FIG. 2 (b). So it will be quite stable. In the experiment, AC voltage was reduced by 30%, AC
In the case of a momentary interruption within 2 seconds, a stable standby power supply voltage (DC5V) could be maintained.

By thus stabilizing the potential at the point B, that is, the 5V power supply voltage supplied to the microcomputer or the like, malfunctions such as reset of the microcomputer do not occur, and the stability of operation of the device is improved. Will be.

Further, in the case of the present example, by being backed up by the capacitor Cb, it is not necessary to make the input voltage of the regulator 6 about twice the output voltage, for example. That is, the necessity of canceling the influence of AC power supply fluctuation by increasing the input voltage of the regulator 6 is not so great. Therefore, for example, the voltage on the secondary side of the power transformer 4 can be set low, and the power transformer can be made smaller than before. Also with this, a transformer,
Also, the heat generation amount of the regulator 5 can be reduced. In the above embodiment, the backup power supply is obtained from the line of the power supply voltage 11V, but the main power supply voltage 12V may be backed up via the resistor and the diode.

[0024]

As described above, according to the power supply device of the present invention, when the standby voltage drops in the standby power supply circuit section during the period in which the main power supply circuit section is turned on, the power supply apparatus operates as follows. A backup means is provided which can maintain the standby voltage at a predetermined voltage by the obtained voltage. Then, for example, this backup means connects the capacitor connected to the first potential point in the main power supply circuit section to the second potential point in the standby power supply circuit section through the discharging diode, and When the voltage drops, the discharge operation from the capacitor is performed so that the voltage at the second potential point can be maintained.

Therefore, in the standby power supply circuit section, a large transformer is used to set a considerably high input voltage, and a regulation voltage is generated from the voltage so that the AC voltage reduction can be dealt with to some extent. The need to turn on the transformer is reduced, ie the voltage obtained from the transformer does not have to be much higher than the regulation voltage. Therefore, the size of the transformer can be reduced, and the amount of heat generated by the transformer can be reduced.

Further, the backup means has an effect that the standby power supply voltage can be stably supplied even when the AC power supply is momentarily cut off, and thus the reliability of the device can be improved.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing a voltage state of each part in the power supply device of the embodiment when the AC power supply is experimentally and instantaneously cut off.

FIG. 3 is a block diagram of an example of a conventional standby power supply circuit.

FIG. 4 is an explanatory diagram showing voltage states of respective parts when an AC power source is intentionally momentarily cut off experimentally.

[Explanation of symbols]

 1 Power outlet plug 2 Start switch 3 Switching power supply circuit 4 Power supply transformer 5 Rectifying and smoothing circuit 6 Regulator 7 Regulator Cb capacitor D Discharge diode

Claims (2)

[Claims] 1. A main power supply circuit section for obtaining a main power supply voltage, and a standby power supply circuit section for supplying a necessary standby voltage not only for turning on / off the main power supply circuit section, but also for the main power supply circuit section. When a standby voltage drop occurs in the standby power supply circuit unit during the period when is turned on, a backup means is provided which can maintain the standby voltage at a predetermined voltage by the voltage obtained from the main power supply circuit unit. Characteristic power supply device. 2. The backup means connects a capacitor connected to a first potential point in the main power supply circuit section to a second potential point in the standby power supply circuit section via a discharging diode, A power supply device, characterized in that, when the voltage at the second potential point drops, the discharge operation from the capacitor is performed so that the voltage at the second potential point can be maintained.