JPH10283045A - Standby power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a standby power unit which can suppress the useless loss of power and the size expansion of printed wiring board to a minimum in the reset of microcomputer with the reduction of output voltage when starting a cooling fan. SOLUTION: Concerning this device, a power supply circuit 11 for driving, power supply circuit 12 for microcomputer and power supply circuit for fan are formed from one transformer and between the power supply circuit 11 for driving and the power supply circuit 12 for microcomputer, a switching means 181, voltage comparing means 182 for comparing a power supply voltage Vm for microcomputer with a prescribed voltage Vms and check diodes 183 and 184 are provided. In the relation of Vm<Vms, the switching means 181 is short-circuitted so as to supply power from the power supply circuit 11 for driving to the power supply circuit for microcomputer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a standby power supply for driving a cooling fan with a standby power supply. In particular, in a video display device equipped with a high-pressure arc discharge lamp, a standby power supply (G03G) for supplying power from a standby power supply to a fan for cooling the lamp.
15/04).

[0002]

2. Description of the Related Art Conventionally, a video display device equipped with a high-pressure arc discharge lamp uses a non-light-emitting display device such as a liquid crystal panel or a digital mirror device. Fan cooling is required. Further, in this video display device, the lamp is heated to a high temperature even after the video is stopped, and thus cooling of the fan is required. However, a video display device equipped with these devices can increase the lamp luminance, and is expected to be developed to a higher luminance.

[0003] 1) The configuration of a conventional main part is shown in FIG.
explain. FIG. 3 omits some of the loads connected to the main power supply and the standby power supply. A flyback type circuit is usually used as the standby power supply.

That is, a standby power supply normally uses one switching transformer 31, and as a secondary side, a drive output voltage Vd, for example, 15 V DC (400 to 800 m).
A), output voltage Vm for microcomputer, for example, DC 8V (30
0 to 600 mA), fan output voltage Vf, for example DC
A circuit for supplying 12 V (200 to 600 mA), a drive power circuit 32, a microcomputer power circuit 33, and a fan power circuit 34 are provided. Each power supply circuit 32, 3
Loads are connected to 3, 34. In FIG. 3, only the cooling fan 34a is shown, and other loads are omitted.

The configuration of each of the power supply circuits 32, 33 and 34 is an ordinary rectifier circuit, for example, a driving power supply circuit 32.
The rectifier diode 321 and the storage capacitor 322 are provided. The microcomputer power supply circuit 33 includes a rectifier diode 331 and a storage capacitor 332. The fan power supply circuit 34 includes a rectifier diode 341 and a storage capacitor 342. It also includes a relay-343 arranged to keep the fan air-cooled for a predetermined time after the video display and lamp are turned off. The basic configuration of the primary side is that the switching transistor 351 is turned on and off by the output signal of the feedback output circuit 361, so that the primary winding 3 of the switching transformer 31 is turned on.
The electric energy is transmitted to the secondary side by charging the electric energy during the ON period and discharging the energy to the secondary winding during the OFF period.

[0006] In order to perform the constant voltage control, a secondary output voltage with a large load and little load fluctuation is usually fed back. For example, the drive output voltage Vd is detected by the voltage detection circuit 36.
2 and the detection signal is transmitted to the feedback output circuit 361 by the photocoupler 363.
The switching transistor 351 is on-off duty driven.

2) In the case where the conventional fan load becomes large, for example, the load current is about 3 A, and the main configuration will be described with reference to FIG.

In FIG. 4, a main power supply is omitted. The standby power supply uses a flyback type circuit with a normal load. In the figure, 32, 321, 32
2, 331, 332, 34, 341, 342, 343,
34a, 351, 361, 362, and 363 are the same as those in FIG. In this case, when the rotation of the fan is started, a starting current that is approximately twice as large as the load current is required.
For example, for 200 to 500 ms, the microcomputer output voltage V
A phenomenon occurs in which m drops below the reset voltage of the microcomputer, and the image is not displayed and is kept in the standby state. This is a configuration used as a method for solving this point.

That is, the winding specification of the switching transformer is increased from the conventional example 1 by increasing the number of windings of the switching transformer 41 for supplying power to the microcomputer power supply circuit 42, and the output voltage Vm
1 is higher than the microcomputer output voltage Vm by, for example, about 5 to 15 V. Output voltage Vm1 is three-terminal regulated.
The voltage is lowered by the power supply 421 and output at Vm. Therefore, the charge stored in the storage capacitor 332 is equal to the voltage difference (Vm
1-Vm), the voltage drop for the microcomputer due to the activation of the fan is supplemented so that the microcomputer is not reset.

3) When the conventional fan load becomes large, for example, a load current of about 3 A, a main part configuration of another embodiment will be described with reference to FIG.

FIG. 5 omits the main power supply. The standby power supply uses a flyback type circuit with a normal load. In the figure, 32, 321, 32
2,331,332,351,361,362,363
Are the same as in FIG. In this case, the fan power supply circuit 51
Are separated and made independent.

That is, the driving power supply circuit 32 and the microcomputer power supply circuit 33 are constituted by the switching transformer 52, and the fan power supply circuit 51 is constituted by the switching transformer 53. A switching transistor 541 provided on the primary side of the switching transformer 53 is connected to a photo-coupler 55 by using a detection signal from a fan voltage detection circuit 551.
2 to form an on-off duty signal in the feedback output circuit 553 and drive the switching transistor 541 to reduce the primary-side electric energy to 2
It is transmitted to the next side. In this case, since the two transformers are used, the microcomputer output voltage is independent of the fan activation, so that the problem of the microcomputer being reset can be solved.

[0013]

However, in the above 1), when the fan load is large, there is a problem that the microcomputer is reset when the fan is started and the standby state is maintained.

In 2), the voltage which is higher than the DC voltage necessary for the microcomputer, for example, 5 to 15 V is reduced by a three-terminal regulator. Therefore, there is a problem that the voltage conversion loss is large. For example, there is a problem that the power loss when the voltage is reduced by 15 V at a current of 600 mA is as high as 9 W.

Further, in 3), since the fan power supply is separated and independent, the cost is increased and the circuit on the primary side is also required, so that the circuit area becomes large (compared to the secondary side).
The distance between Cu foils is large. (Insulation distance between primary and secondary is also required), which is not suitable for miniaturization.

[0016]

In order to solve the above-mentioned problems, a standby power supply according to the present invention supplies power for a fan, a power supply for a microcomputer, and a power supply for driving by a single converter transformer, and supplies a power supply voltage for the microcomputer. And a means for supplying power to the microcomputer power supply when the fan is started from the driving power supply.

According to the present invention, when the microcomputer output voltage drops at the time of starting the fan or the like, power is supplied from the driving power supply to the microcomputer power supply circuit, so that the microcomputer is not reset, and the power loss is small. It is possible to provide a standby power supply device in which the printed circuit board area can be suppressed to a slight increase.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, in a device having a standby power supply and a main power supply, a power supply for a fan, a power supply for a microcomputer, and a power supply for driving are supplied by one converter transformer. Means for detecting the power supply voltage for the microcomputer, and means for supplying power to the microcomputer power supply when the fan is started from the driving power supply, wherein the power supply voltage for the microcomputer is detected when the fan is started. Since the voltage drop is detected by the means and the power is supplied from the driving power supply having a voltage higher than the voltage for the microcomputer, the voltage drop to the voltage lower than the reset voltage of the microcomputer is prevented.

According to a second aspect of the present invention, in an apparatus having a standby power supply and a main power supply, a power supply for a fan,
A standby power supply device comprising a microcomputer power supply and a drive power supply comprising one converter transformer, wherein the drive power supply voltage Vd and the microcomputer power supply voltage Vm satisfy a relationship of Vd> Vm, and Switching means and a microcomputer power supply voltage Vm between the microcomputer power supply
Is provided with a predetermined voltage Vms. When Vm <Vms, the drive power supply supplies power to the microcomputer power supply via the switching means. The voltage drop is detected by means for detecting the power supply voltage Vm, and the microcomputer voltage Vm is detected.
Since the power is supplied from the driving power supply Vd having a voltage higher than m, the voltage is not reduced below the reset voltage of the microcomputer.

According to a third aspect of the present invention, there is provided the standby power supply according to the second aspect, wherein the standby power supply is used for cooling a high-pressure arc discharge lamp, and drives the fan for a predetermined time during the operation of the lamp and after the lamp is turned off. The cooling of the high-pressure arc discharge lamp requires a plurality of cooling fans. Since the voltage drop is detected by the means for detecting the power supply voltage Vm and the power is supplied from the driving power supply Vd having a voltage higher than the microcomputer voltage Vm, the voltage is not reduced below the reset voltage of the microcomputer.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) FIG. 1 is a configuration diagram of a main part of Embodiment 1. In the figure, the main power supply is omitted. Also, the standby power supply is a standby power supply 10
A driving power supply circuit 11 and a microcomputer power supply circuit 1
2. Power is supplied to the fan power supply circuit 13 from one converter transformer 14. In FIG. 1, the loads of the driving power supply circuit 11 and the microcomputer power supply circuit 12 are omitted. The driving power supply circuit 11 is composed of a rectifier diode 111 and a storage capacitor 112.
It is composed of a rectifier diode 121 and a storage capacitor 122. The fan power supply circuit 13 includes a rectifier diode 13.
1, a storage capacitor 132, and a relay 133 for supplying power to the plurality of cooling fans 15 only when cooling the fan. Here, the driving power supply voltage Vd, for example, DC15V
And the microcomputer power supply voltage Vm, for example, DC8V, and the relationship of Vd> Vm is provided. On the other hand, in order to perform the constant voltage control, the drive power supply voltage Vd is detected to be less than or equal to a predetermined voltage by the voltage detection circuit 161, and this detection signal is transmitted to the feedback output circuit 163 by the photocoupler 162. And the switching transistor 17
Is output as a signal for duty driving.

In addition, a switching means 181 and a means 182 for comparing the microcomputer power supply voltage Vm with a predetermined voltage Vms, for example, 4 VDC, are provided between the drive power supply 11 and the microcomputer power supply 12, and the relationship of Vm <Vms is satisfied. , Power is supplied from the driving power supply 11 to the microcomputer power supply 12 via the switching means 181. In order to prevent backflow, backflow prevention diodes 183 and 184 are provided.

(Embodiment 2) FIG. 2 is a configuration diagram of a main part of Embodiment 2. FIG. 3 shows an example of a specific circuit of the switching means and the voltage comparison means of the first embodiment. In the figure, reference numerals 11 and 12 denote portions of the reference numerals 11 and 12 shown in FIG. Also, 111, 1
12, 121, 122, 183 and 184 are the same as those in FIG. That is, as a switching means, the collector of the switching transistor 21, for example, an NPN transistor is connected in series to the cathode side of the backflow prevention diode 183, and the emitter is connected in series to the anode side of the backflow prevention diode 184. I do. As a voltage comparing means, a Zener diode 22, for example, a Zener voltage of 4.8V is used, and the cathode side is a base of the switching transistor 21.
Grounded to the anode side. The resistance 23
Is connected to the collector of the switching transistor 21 and the cathode side of the Zener diode 22 to supply current to the Zener diode 22. Therefore, since the base voltage of the switching transistor 21 is fixed to the Zener voltage of 4.8 V, the emitter voltage is, for example, 0.6 V and the threshold voltage of the backflow prevention diode 184 is 0.6 V. Then, when the microcomputer power supply voltage Vm drops to 3.6 V or less, the switching transistor 21 is turned on, and the power is supplied from the storage capacitor 24 and also from the driving power supply circuit, so that the microcomputer is not reset. . Further, when the microcomputer power supply voltage Vm drops to a predetermined voltage, for example, 8 V or less, power is supplied from the storage capacitor 25.

The above description of the second embodiment shows one example, and the present invention is not limited to this configuration. For example, although an NPN transistor is shown as the switching means, any PNP transistor or MOSFET may be used as long as it has a switching function. Therefore, a standby power supply device including the switching means and the voltage comparison means is included in the present invention.

[0025]

As described above, according to the standby power supply of the present invention, by using the switching means and the voltage comparing means, the reset of the microcomputer caused by the decrease in the output voltage at the time of starting the cooling fan can be performed with unnecessary power. It is possible to minimize the loss and enlargement of the size of the printed wiring board.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram of a standby power supply according to a first embodiment of the present invention;

FIG. 2 is a main part configuration diagram of a standby power supply according to a second embodiment of the present invention;

FIG. 3 is a configuration diagram of a main part of a conventional standby power supply device.

FIG. 4 is a main part configuration diagram of a conventional standby power supply device.

FIG. 5 is a configuration diagram of a main part of a conventional standby power supply device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 drive power supply circuit 111 rectifier diode 112 storage capacitor 12 microcomputer power supply circuit 121 rectifier diode 122 storage capacitor 13 fan power supply circuit 131 rectifier diode 132 storage capacitor 14 switching transformer 15 cooling fan 161 voltage detection circuit 162 Photocoupler 163 Feedback output circuit 17 Switching transistor 181 Switching means 182 Voltage comparing means 183 Backflow prevention diode 184 Backflow prevention diode 21 Switching transistor 22 Zener diode 23 Resistance 24 Storage capacitor 25 Storage capacitor

Claims (3)

[Claims] 1. A standby power supply having a standby power supply and a main power supply, means for supplying power to a fan, a power supply for a microcomputer, and a power supply for driving by a single converter transformer, and detecting the power supply voltage for the microcomputer. Means for supplying power to the microcomputer power supply from the drive power supply when the fan is started up. 2. A standby power supply having a standby power supply and a main power supply, wherein the power supply for a fan, the power supply for a microcomputer, and the power supply for a drive comprise a single converter transformer.
d and the microcomputer power supply voltage Vm satisfy the relationship of Vd> Vm, and the switching means and the microcomputer power supply voltage Vm are provided between the driving power supply and the microcomputer power supply.
2. A standby power supply device according to claim 1, further comprising means for comparing the power supply voltage to a predetermined voltage Vms, and when the relation of Vm <Vms is satisfied, the driving power supply supplies power to the microcomputer power supply via the switching means. . 3. The standby power supply according to claim 2, further comprising a fan power supply for cooling the high-pressure arc discharge lamp and driving the fan for a predetermined period of time while the lamp is turned on and after the lamp is turned off.