JP2001251857A - Dc power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control heat caused when a malfunction in load is generated. SOLUTION: A DC power supply is used in a DC power supply, in which a voltage as a DC output is lowered by changing a voltage dividing ration from reference value to a smaller value than the reference value in a voltage dividing circuit which is used for error detection of output voltage. When a DC output of 112 V as object of error detection is a reference DC voltage, the DC output voltages obtained by subtracting the reference DC output 112 V from a plurality of DC outputs is observed, by using an malfunction detecting unit 9 and a main controller 10. When the monitored voltage becomes lower than a predetermined given voltage, the voltage dividing ratio of the voltage- driving circuit is changed to the smaller value.

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 device having a plurality of DC outputs, and more particularly, to a method of changing a voltage of a DC output by changing a voltage dividing ratio of a voltage dividing circuit for error detection. The present invention relates to a DC power supply device to be dropped.

[0002]

2. Description of the Related Art In a television, when a mode is shifted from an operation mode to a standby mode, it is required to stop the operation of the television section while preventing spots from remaining. In addition, the control microcomputer is required to supply a DC output of a predetermined voltage even in the standby state. A DC power supply for satisfying this requirement has been proposed as Japanese Patent Application Laid-Open No. Hei 8-130874. That is, in this technique, the voltage dividing ratio of the voltage dividing circuit provided in the error detection circuit can be changed. And
When the mode changes to the standby mode, control is performed to reduce the partial pressure ratio. Therefore, assuming that the target value of the control in the operation mode is, for example, 112 V, the target value of the control is, for example, 40 V in the standby mode. Therefore, when the mode shifts from the operation mode to the standby mode, the voltage of the DC output (referred to as the first DC output) supplied to the television unit is changed from 112V to 40V.
Drop towards V. For this reason, the television unit stops operating without causing spot remaining. Also,
A step-down regulator is used as a power supply for the microcomputer.
In the standby mode, the DC output that becomes 8.5 V (the second DC output) is reduced to 5 V. Therefore, even when the standby mode is set and the voltage of the second DC output drops, the microcomputer is supplied with the standard value of 5 V.

[0003]

SUMMARY OF THE INVENTION The present invention is to suppress heat generation when a problem occurs in a load in the prior art. For this reason, when the voltage of the DC output for which error detection is not performed becomes equal to or lower than a predetermined value, the present invention reduces the voltage division ratio and lowers the DC output voltage to generate heat due to the occurrence of a load failure. It is an object of the present invention to provide a DC power supply device capable of suppressing the occurrence of a power supply.

[0004]

In order to solve the above-mentioned problems, a DC power supply according to the present invention comprises a plurality of DC outputs,
An output voltage error is detected based on a divided voltage of a voltage dividing circuit that divides one of the plurality of DC outputs, and the detected error is fed back to the primary side switching circuit. The division ratio is applied from a reference value to a DC power supply device that reduces the DC output voltage by changing the DC output voltage to a value smaller than the reference value. When the one DC output is used as a reference DC output, a plurality of DC outputs are used. The voltage of the DC output excluding the reference DC output is monitored, and when the monitored voltage becomes lower than a preset voltage, the voltage dividing ratio of the voltage dividing circuit is changed to the small value. That is, when the monitored voltage becomes lower than the preset voltage is when the resistance value of the load of the DC output becomes small, such as a short circuit of the load. On the other hand, when the voltage dividing ratio of the voltage dividing circuit is reduced, the DC output excluding the reference DC output has an increased equivalent internal resistance. Therefore, even if the resistance value of the load is small, the amount of heat generated is small since the flowing current is small.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
This will be described with reference to the drawings. FIG. 1 is a block diagram showing an electrical configuration of an embodiment of a DC power supply device according to the present invention, and shows a configuration when applied to a video-integrated television.

In the figure, a television unit 4 includes a tuner unit,
The block is provided with a processing section for the output signal of the tuner section, a CRT, and the like. The video section 3 is a block for performing recording and playback, and includes a recording and playback section, a mechanism for running a video cassette tape, and the like.

[0007] The switching circuit 1 is a block including a switching transistor, a control transistor for controlling a base current of the switching transistor, and the like, and a DC source obtained by rectifying and smoothing a commercial power supply is led. Further, a primary coil L1 wound around the transformer 2 and a base coil L2 are connected. Then, the switching of the current flowing through the primary coil L1 is performed based on the error output given from the error detection circuit 8 via the photocoupler 7.

The transformer 2 has two secondary coils L3 and L4 having no tap and a secondary coil L having a tap provided.
5 is wound, and the output of each of the secondary coils L3 to L5 is rectified and smoothed by a diode and a capacitor.
Specifically, a DC output of 8 V obtained by rectifying and smoothing the output of the secondary coil L3 serves as a power supply for a microcomputer. Further, the DC output 12V obtained by rectifying and smoothing the output of the secondary coil L4 is used for the motor of the television unit 4 and the video unit 3, the audio signal circuit, and
It is a power supply for other analog signal circuits.
Further, a DC output 112 V obtained by rectifying and smoothing the output of the end terminal of the secondary coil L <b> 5 serves as a power supply for the horizontal circuit of the television unit 4. Also, a DC output 27V obtained by rectifying and smoothing the output of the tap of the secondary coil L5 is a power source for the vertical circuit of the television unit 4.

From the above, in the operation mode, that is, when the voltage dividing ratio of the voltage dividing circuit of the error detecting circuit 8 is a specified value, the voltage of the DC output 8V is 8V, the voltage of the DC output 12V is 12V, The voltage of the output 27V is 27V, and the voltage of the DC output 112V is 112V. In the standby mode, that is, when the voltage division ratio becomes smaller than the specified value, the DC output voltage of 8 V is 2.3 V and the DC output voltage is 12 V.
The voltage of V is 4V, the voltage of DC output 27V is 8.5V, and the voltage of DC output 112V is 40V.

The error detection circuit 8 includes a voltage dividing circuit for dividing the DC output 112 V (reference DC output described in claims), a reference voltage generating circuit, a circuit for detecting a difference between the divided voltage and the reference voltage, and the like. It is a block provided with. Then, a voltage error between the divided voltage of the DC output 112 V and the reference voltage is detected, and the photocoupler 7 is driven with a current corresponding to the detected voltage error. Further, the voltage dividing ratio of the voltage dividing circuit can be changed.

The bleeder circuit 5 is a block provided with a bleeder resistor serving as a load of a DC output 112 V, a switch for opening and closing the connection of the bleeder resistor, and the like. The switch circuit 6 is a block for switching the input of the step-down regulator 11 to a DC output of 8 V or a DC output of 27 V. In addition, the step-down regulator 11
The DC output from the switch circuit 6 is stepped down to 5 V, and the stepped-down output 22 is supplied to the microcomputer 12.

The abnormality detector 9 has four DC outputs 8V, 1
Of the 2V, 27V, and 112V, the DC output 112V that is the reference DC output is excluded, and the DC output 8V that is the power supply of the microcomputer 12 in the operation mode is removed.
It is a block for monitoring the voltages of the two DC outputs 12V and 27V. When at least one of the DC outputs 12V and 27V is close to a predetermined value of 0V, the main control unit 1 outputs an output 24 indicating a voltage drop.
Send to 0.

The main control section 10 includes a video section 3 and a television section 4.
Is a block for mainly performing the control of. Also,
By controlling the voltage dividing ratio of the voltage dividing circuit provided in the error detecting circuit 8, the video section 3 and the television section 4 are switched to the operation mode or the standby mode. Further, the connection of the switch circuit 6 is switched in accordance with the mode switching. Further, it controls the bleeder circuit 5. In addition, when the output 24 indicating the voltage drop is sent from the abnormality detection unit 9 in the operation mode, the voltage dividing ratio of the error detection circuit 8 is changed from the specified value to a value smaller than the specified value, and all the DC outputs are changed. 8
Control is performed to decrease the voltages of V, 12 V, 27 V, and 112 V.

The main control unit 10 is mainly composed of software executed by the microcomputer 12, and receives instructions from a remote controller and switches on an operation panel. 4
The block is required to be in the operating state even during the period when the video section 3 does not operate. The abnormality detection unit 9 is a block configured as a part of a peripheral circuit of the microcomputer 12.

FIG. 2 is a circuit diagram showing a detailed electric connection of the error detection circuit 8, FIG. 3 is a circuit diagram showing a detailed electric connection between the switch circuit 6 and the step-down regulator 11, and FIG.
Is a circuit diagram showing detailed electrical connection of the bleeder circuit 5,
FIG. 5 is a circuit diagram showing the detailed electrical connection of the abnormality detection unit 9.

The detailed configuration of the error detection circuit 8 will be described below with reference to FIG. The transistor Q1 is an element that detects a voltage error of the DC output 112V and drives the light emitting diode D1 with a current corresponding to the detected error. Therefore, the reference voltage generated by the Zener diode D2 is applied to the emitter.
A divided voltage of a voltage dividing circuit including resistors R3 and R4 is applied to the base. The resistance R5 is equal to the resistance R
This is an element for changing the voltage dividing ratio (specified value) of the voltage dividing circuit composed of R3 and R4 to a value smaller than the specified value.

That is, when the transistor Q2 whose on / off is controlled by the output 21 from the main control unit 10 is set to the on state, the anode potential of the diode D3 becomes lower than the cathode potential, and the resistor R5 is disconnected from the resistor R4. It is. On the other hand, when the transistor Q2 is turned off, a current flows through the diode D3, and the resistor R5 is connected to the resistor R4.
Is equivalent to a state of being connected in parallel to In summary, when the transistor Q2 is turned on, the voltage dividing ratio of the voltage dividing circuit becomes a specified value, and the transistor Q1 performs error detection so that the voltage of the DC output 112V becomes 112V. On the other hand, when the transistor Q2 is turned off, the voltage division ratio decreases,
The transistor Q1 has a DC output voltage of 112 V of 40 V
Error detection is performed so that

The circuit composed of the resistor R7 and the Zener diode D4 is a block for generating a 32 V voltage for a tuner. The resistor R6 is connected to the transistor Q
When 2 is turned off, it is an element for flowing the DC output 27V into the voltage dividing circuit, and slightly lowers the speed of the voltage drop of the DC output 27V when the voltage dividing ratio is reduced. The output 25 sent from the collector of the transistor Q2 is an output obtained by inverting the logic of the output 21 of the main control unit 10, and serves as a signal for switching the connection of the switch circuit 6, as described later. ing.

Hereinafter, the configurations of the switch circuit 6 and the step-down regulator 11 will be described in detail with reference to FIG. The transistor Q3 provided in the switch circuit 6
This is an element for turning on / off the DC output 27V.
That is, when the transistor Q3 is turned on, the voltage at the cathode of the diode D5 becomes higher than the voltage at the anode, and the DC output 8V is disconnected from the step-down regulator 11. Therefore, when the transistor Q3 is turned on, a DC output of 27 V is sent to the step-down regulator 11. On the other hand, when the transistor Q3 is turned off, the DC output 27V is disconnected from the step-down regulator 11, and the DC output 8V is sent to the step-down regulator 11.

On / off of the transistor Q3 is as follows.
It is necessary to operate in conjunction with the switching of the voltage division ratio of the error detection circuit 8. When the voltage division ratio is a specified value, the transistor Q3 needs to be turned off, and when the voltage division ratio is small, the transistor Q3 needs to be turned on. Therefore, the ON / OFF of the transistor Q3
The off control may be performed by inverting the level of the output 21 of the main control unit 10. Therefore, the transistor Q3
Has a diode D to prevent current from flowing in
An output 25 sent from the error detection circuit 8 is led through 6.

In FIG. 1, for simplification of the control relationship, the switch circuit 6 is shown as a configuration in which the connection is switched by an output from the main control unit 10. However, in the actual machine, as shown in FIGS. 2 and 3, in order to reduce the number of output lines of the microcomputer 12, the connection of the switch circuit 6 is established by using the output 25 inverted by the error detection circuit 8. It is configured to switch.

The step-down regulator 11 generates and outputs a 5 V DC output 22 serving as an operating power supply of the microcomputer 12. Therefore, a voltage stabilized by the Zener diode D7 is applied to the base of the transistor Q4. Note that the lower limit of the input voltage that can stabilize the DC output 22 to 5 V is about 7 V in the present embodiment.

Hereinafter, the configuration of the bleeder circuit 5 will be described in detail with reference to FIG. One terminal of a bleeder resistor R15 is connected to the DC output 112V. Also,
The other terminal of the bleeder resistor R15 is connected to the transistor Q6
Connected to the collector. And the transistor Q
6 is turned on / off by an output 23 from the main control unit 10. Therefore, when the transistor Q6 is turned on, the bleeder resistor R15 is connected to the DC output 112V, and when the transistor Q6 is turned off, the connection of the bleeder resistor R15 is disconnected.

Hereinafter, the abnormality detecting section 9 will be described with reference to FIG.
Will be described in detail. A resistor R21 having one terminal connected to + 5V and a resistor R22 having one terminal connected to the other terminal of the resistor R21 and the other terminal connected to the secondary-side ground level are divided by + 5V. It is a pressure circuit. Further, the divided voltage output 24 is at a level at which the main control unit 10 can recognize the H level, and specifically, is set to 3.5V. A DC output of 12 V, 2 is connected to a connection point between the resistors R21 and R22 via diodes D9 and D10 for preventing current from flowing.
7V is connected.

Therefore, when a problem occurs in the load of the DC output 12V and the voltage of the DC output 12V becomes close to 0V, the output 24 becomes L level. Further, when a failure occurs in the load of the DC output 27V and the voltage of the DC output 27V becomes close to 0V, the output 24 becomes L level. That is, the abnormality detection unit 9 sets the output 24 to the L level, thereby notifying the main control unit 10 that a failure has occurred in at least one of the loads of the DC outputs 12V and 27V.

FIG. 6 is an explanatory diagram showing changes in main signals of the embodiment, and FIG. 7 is an explanatory diagram showing voltage changes of the DC outputs 27V and 112V. While referring to the figure as necessary,
The operation of the embodiment will be described.

In a mode in which only the television section 4 or the television section 4 and the video section 3 are operated, the main control section 10
Sets the horizontal circuit of the television unit 4 to the ON state. Further, by setting the output 21 to the H level and setting the voltage dividing ratio to a specified value, the DC outputs 8V, 12V, 27V, 112V
Are set to 8V, 12V, 27V, 112V
Set to. When the output 21 is at the H level, the output 25 is at the L level. Therefore, DC output 8V
Is guided to the step-down regulator 11 via the switch circuit 6. Further, by setting the output 23 to the L level, the connection of the bleeder resistor R15 is opened.

When the operation mode shifts from the operation mode to the standby mode in which the operations of the television unit 4 and the video unit 3 are stopped, the output 21 is set to the L level and the output 23 is set to the H level (time T1). When the output 21 goes to the L level, the voltage dividing ratio of the voltage dividing circuit of the error detecting circuit 8 decreases, and the voltages of the DC outputs 8V, 12V, 27V, and 112V start decreasing. Also, since the output 23 goes to the H level, the bleeder resistor R15 is connected to the DC output 112V. Therefore, the voltage of the DC output 112V rapidly decreases from 112V toward 40V.

When the output 21 goes to L level, the output 25 goes to H level.
7V is led. Therefore, the voltage of the DC output 27V is
7.5V (7V which is the lower limit of the step-down regulator 11)
(A value obtained by adding the drop of the switch circuit 6). On the other hand, after the time T1, the voltage of the DC output 112V rapidly decreases as indicated by 53 in FIG. Therefore, the time until the supply power from the primary side increases is short. That is, the voltage of the DC output 27V is 8.
Before the voltage drops below 5 V, the power supplied from the primary side increases. Therefore, the voltage of the DC output 27V is prevented from becoming 8.5V or less (see 54).

The broken line 51 in FIG. 7 shows the voltage change of the DC output 112 V when the bleeder resistor R15 is not connected, and the voltage drop speed is slow. Therefore, the voltage of the DC output 27V temporarily becomes lower than the voltage V1 (7.5V) as shown by the broken line 52. However, the bleeder resistance R
15 is connected and the voltage drop of the DC output 112V is accelerated, the voltage of the DC output 27V is maintained at a value equal to or higher than V1. Therefore, the value of the bleeder resistor R15 is determined by checking the voltage change of the DC output 27V after the time T1 in the actual device.
The voltage of the DC output 27V is set to a value that does not fall below V1.

The voltage of the DC output 112 V is 40 V
After falling to prevent power consumption from increasing,
By setting output 23 to L level, DC output 112
The bleeder resistor R15 is disconnected from V (time T2). Thereafter, the horizontal circuit of the television unit 4 is turned off (at time T
3).

A case will be described below in which only the video section 3 is operated without operating the television section 4 such as timer recording and discharging of a video cassette. When only the video section 3 is operated, the output 21 is set to the H level while the horizontal circuit of the television section 4 is kept in the off state. Also, by setting the output 23 to the H level, the bleeder resistor R15 is connected to the DC output 112V (at time T).
4).

When the output 21 becomes H level, the voltage dividing ratio of the voltage dividing circuit of the error detecting circuit 8 becomes a specified value, and the DC output 11
Control is started so that the voltage of 2V becomes 112V.
At this time, the bleeder resistor R15 is connected to the DC output 112V. Therefore, when the voltage of the DC output 12V, 27V decreases, the voltage of the DC output 112V also decreases, so that the DC output 8V, 12V, 27V,
Each voltage of 112V is 8V, 12V, 27V, 112V
It is controlled so that As a result, even when the motor of the video section 3 is driven to increase the load of the DC output 12V, the voltage of the DC output 12V is maintained at 12V.

When the operation of the video section 3 is stopped from the state in which only the video section 3 is operated, the output 21 is set to the L level and the voltage dividing ratio is reduced to thereby reduce the voltage of the DC outputs 8V, 12V, 27V and 112V. Is lowered (time T5). At this time, the bleeder resistance R15 is
Since it is connected to the DC output 112 V, the voltage of the DC output 27 V is maintained at 8 V or more. Then, after the voltage of the DC output 112 V has dropped to 40 V, the output 23 is set to the L level so that the DC output 112 V
From the bleeder resistor R15 (time T6).

On the other hand, by setting the output 21 to the H level, only the television section 4 or the video section 3 or both the television section 4 and the video section 3 are operated in a state where both the television section 4 and the video section 3 are operated. Suppose that a malfunction occurs in the DC power supply 3 and the voltages of the DC outputs 12 V and 27 V have dropped to near 0 V. At this time, the output 24 of the abnormality detector 9 changes from the H level to the L level. When the output 24 is at the L level while the output 21 is at the H level, the main control unit 10 determines that a failure has occurred in the television unit 4 or the video unit 3 and changes the output 21 to the L level. .

When the output 21 is at the L level, the DC outputs 12 V and 27 V have an equivalent internal resistance that is large. Therefore, even if a short circuit or the like occurs in the television unit 4 or the video unit 3 as a defect, for example, the DC output 12
The current values of V and 27V remain small. Therefore, the amount of heat generated due to the occurrence of the problem is suppressed, and the temperature rise of the television unit 4 and the video unit 3 is prevented.

Hereinafter, other embodiments will be described.

The configuration of the bleeder circuit 5 in this embodiment is such that a bleeder resistor R15 is always connected between a DC output 112V that is a reference DC output and a DC output 27V whose voltage is lower than the DC output 112V. Therefore, the configuration of the bleeder circuit 5 is different from the configuration shown in FIG. 4 in that the transistor Q6 is omitted and two resistors connected to the base of the transistor Q6 are omitted. That is, the bleeder circuit 5 has a DC output of 112 V
And the other terminal is only the bleeder resistor R15 connected to the DC output 27V as shown by the broken line.

In the above embodiment, the DC output 112
A current always flows through V due to the bleeder resistor R15. Therefore, when the output 21 changes from the H level to the L level, the television unit 4 is connected via the bleeder resistor R15.
, The voltage of the DC output 112V immediately drops toward 40V. Therefore, the voltage of the DC output 27V is prevented from becoming a voltage lower than the voltage V1 due to a synergistic effect of the fast falling rate of the voltage of the DC output 112V and the current supplied through the bleeder resistor R15. .

[0040]

According to the DC power supply device of the present invention, the voltage dividing ratio of the voltage dividing circuit used for detecting the error of the output voltage is calculated from the reference value.
When applied to a DC power supply that reduces the DC output voltage by changing it to a value smaller than the reference value, and when the DC output subject to error detection is used as the reference DC output, the reference DC output is excluded from the plurality of DC outputs. The DC output voltage is monitored, and when the monitored voltage becomes lower than a preset voltage, the voltage dividing ratio of the voltage dividing circuit is changed to the small value. That is, when the voltage of the DC output for which error detection is not performed becomes equal to or lower than the predetermined value, the voltage of the DC output is decreased by reducing the voltage dividing ratio. For this reason, it is possible to suppress heat generation due to occurrence of a load defect.

[Brief description of the drawings]

FIG. 1 is a block line showing an electric configuration of an embodiment of a DC power supply device according to the present invention.

FIG. 2 is a circuit diagram showing detailed electrical connections of an error detection circuit.

FIG. 3 is a circuit diagram showing detailed electrical connection between a switch circuit and a step-down regulator.

FIG. 4 is a circuit diagram showing detailed electrical connections of a bleeder circuit.

FIG. 5 is a circuit diagram showing detailed electrical connection of an abnormality detection unit.

FIG. 6 is an explanatory diagram showing changes in main signals according to the embodiment.

FIG. 7 is an explanatory diagram showing a voltage change of a DC output.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 switching circuit 3 video section 4 television section 5 bleeder circuit 6 switch circuit 11 step-down regulator 12 microcomputer 8 V, 12 V, 27 V DC output 112 V reference DC output Q2 Transistors R3 and R4 for switching voltage division ratio Constituting voltage division circuit Resistance R5 Resistance to reduce the voltage division ratio R15 Bleeder resistance

Claims (1)

[Claims] An output voltage error is detected based on a divided voltage of a voltage dividing circuit that divides one of the plurality of DC outputs and outputs the detected error to a primary side. A DC power supply device for reducing the voltage of the DC output by changing the voltage dividing ratio of the voltage dividing circuit from the reference value to a value smaller than the reference value, while feeding back the one DC output to the reference DC. When the output, the voltage of the DC output excluding the reference DC output from the plurality of DC outputs is monitored, and when the monitored voltage becomes lower than a preset voltage, the voltage dividing ratio of the voltage dividing circuit is set to the small value. DC power supply characterized by changing.