JPH0545109Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Application of the Invention) This invention relates to a power supply starting device, and particularly to a power supply starting device that prevents a large inrush current from flowing when the power supply is started.

(Prior Art) Conventionally, a switching regulator type power supply device has been used as a power supply in a copying machine or the like. In order to allow the user to safely deal with problems such as paper jams in the copying machine, an interlock switch is installed in the power supply that opens and closes in conjunction with the opening of the copying machine cover. It is equipped. That is, when the cover is opened, the interlock switch opens and prevents power from being supplied to the load from the power supply.

Therefore, even if the user opens the cover of the copying machine and touches the equipment inside the copying machine in the event of a problem, the user will not receive an electric shock or the load will move, allowing the user to safely deal with the problem.

(Problems to be Solved by the Invention) FIG. 4 shows a timing diagram of the power supply device.
Figure a shows the on/off state of an interlock switch that opens and closes in conjunction with the cover, Figure b shows the output voltage (Vout) of the power supply, and Figure c shows the output current i.

In the figure, the interlock switch is on until time t1, and the output voltage Vout and output current i of the power supply device output predetermined voltages and currents, respectively, and are supplied to each load of the copying machine. ing.

Now, when the cover of the copying machine is opened for some reason at time t1, the interlock switch is turned off and the output voltage Vout and output current i
each becomes zero. When the cover is closed again at time t2 and the interlock switch is turned on, both the output voltage Vout and the output current i rise. In particular, the output current i rises rapidly, and a large rush current (approximately 150 A) flows through switches, relays, switching regulator transistors, etc.
As a result, the contacts of the switch, relay, etc. may melt and malfunction, or the transistor for the switching regulator may malfunction or malfunction.

Conventionally, this problem has been solved by placing a large chiyok coil in the circuit to reduce the inrush current, but if a large chiyok coil is used in the circuit, the size of the power supply device becomes large and the cost increases. There was a problem.

The purpose of this invention is to provide a power supply device that eliminates the problems of the prior art described above and can reduce rush current without including a large choke coil in the circuit.

(Means and operations for solving the problem) In order to achieve the above object, the present invention turns on the switch means provided between the power supply and the load first when starting the power supply, and then turns on the switch means provided between the power supply and the load. The feature is that a means to start up the power supply is provided.

According to the present invention, the power is turned on shortly after the switch means is turned on, so that inrush current can be reduced. Therefore, the probability of failure of the switch means and electronic components is reduced, and a large chain coil is not required.

(Example) The present invention will be described in detail below with reference to the drawings. FIG. 1 shows a circuit diagram of an embodiment of the present invention. FIG. 1 shows the main parts of a switching regulator type power supply device.

In the figure, 1 is a rectifier that rectifies AC input supplied from a commercial power source, 2 is a transformer, and 3 is a switching regulator transistor connected to the primary side of the rectifier. In addition, 4 is a chiyoke coil connected to its secondary side, 5 is a capacitor,
SW1 is the first interlock switch, 8a~
8n is a load connected via the switch SW1.

Further, 6 is a PWM signal generation circuit that supplies a PWM signal to the transistor 3 to control its on/off duty, 7 monitors the output voltage,
This is a feedback circuit that feeds back the abnormality to the PWM signal generation circuit 6 to suppress the abnormality when it occurs. Further, 9 is an on/off circuit for controlling the on/off operation of the PWM signal generating circuit 6, 10 is a delay circuit, and SW2 is a second interlock switch.

Next, the operation of this embodiment will be explained with reference to FIGS. 1 and 2. Here, FIG. 2 shows a time chart of the main parts of the signals in FIG.

When an AC input is applied to the power supply device from a commercial power supply or the like, the AC input is rectified by a rectifier 1 and supplied to a transformer 2 . At this time,
When the PWM signal generation circuit 6 supplies a PWM signal to the base of the transistor 3, the transistor 3 is turned on when an H level voltage is supplied, and turned off when an L level voltage is supplied.
An AC voltage corresponding to the duty of the PWM signal is generated on the secondary side of the transformer 2, and the AC voltage is rectified by the choke coil 4 and the capacitor 5 and supplied to the loads 8a to 8n.

Now, when an abnormally high or low voltage appears on the secondary side of the transformer, the feedback circuit 7 detects this and sends a negative feedback signal to the PWM.
It is output to the signal generation circuit 6. As a result, the above
The PWM signal generation circuit 6 outputs a PWM signal having a duty of returning the abnormal voltage to the base of the transformer 3, thereby suppressing the abnormal voltage.

When the power supply device is operating as described above, for example, when the cover of a copying machine is opened at time t1 in FIG. 2, the first,
The second interlock switches SW1, SW2 are opened and turned off. For this reason, loads 8a to 8n
is disconnected from the power supply, and the output current i on the secondary side of the power supply becomes zero. Further, the off signal of the second interlock switch SW2 is delayed by a predetermined time Δt by the delay circuit 10,
It is input to the on/off circuit 9. As a result, the on/off circuit 9 outputs a signal that turns off the operation of the PWM signal generation circuit 6, and the PWM signal generation circuit 6 stops operating. Therefore, the transistor 3 stops its switching operation, and the output voltage Vout on the secondary side becomes zero.

Next, at time t2, when the cover of the copying machine is closed, the first and second interlock switches SW1 and SW2 are turned on simultaneously. Therefore, the secondary side of the transformer 2 and the loads 8a to 8n are connected via the first interlock switch SW1. However, when the first interlock switch SW1 is turned on, the
Since the PWM signal generation circuit 6 and the transistor 3 have not started operating, no voltage is applied to the loads 8a to 8n via the first interlock switch SW1, and no current is supplied. .

The on signal of the second interlock switch SW2 is input to the delay circuit 10 and delayed by the predetermined time Δt. The remote signal Vr obtained in this way enters the on-off circuit 9, and the on-signal outputted from the on-off circuit 9 is transmitted to the PWM
The signal is supplied to the signal generation circuit 6. As a result, the applicable
The PWM signal generation circuit 6 starts operating, and the transistor 3 performs on/off operations according to the duty of the PWM signal supplied to its base.

When the transistor 3 starts to turn on and off, a voltage is generated on the secondary side of the transformer 2, and the voltage and current are applied to the first interlock switch.
It is supplied to loads 8a to 8n through SW1.

As described above, according to this embodiment, the first interlock switch SW1 connecting the power supply device and the load
Since the output voltage Vout will be applied to the load after a time Δt after turning on, the output voltage on the secondary side of the transformer 2 will rise with the load connected. Therefore, in the process of the output voltage rising from 0V to a predetermined voltage, the current i
will gradually increase in flow into the load, and the inrush current will become smaller. As a result, melting of the switch contacts is reduced and failures of electronic components such as transistors are eliminated. Furthermore, the choke coil connected to the secondary side of the transformer can be made smaller.

FIG. 3 is a circuit diagram showing a specific example of the on/off circuit 9 shown in FIG. 1. In FIG. The collector of the transistor 9b is connected to the output of the PWM signal generation circuit 6.

Now, when the remote signal Vr is input to the on/off circuit 9, the output of the comparison circuit 9a becomes L level, and the transistor 9b is turned off. As a result, the output of the PWM signal generating circuit 6 is disconnected from the ground, and a PWM signal with a predetermined duty is supplied to the base of the transistor 3. On the other hand, when the second interlock switch SW2 is turned off and a zero remote signal Vr is input to the on/off circuit 9, the output of the comparison circuit 9a becomes H level and the transistor 9b is turned on. As a result,
The output of the PWM signal generating circuit 6 is connected to ground, and the base of the transistor 3 is forcibly connected to ground, stopping its operation.

Although the above embodiment has been described using a copying machine as an example, the present invention is not limited to this and can of course be applied to other devices.

(Effect of the invention) As is clear from the above explanation, according to the power supply device of the invention, the output voltage is generated Δt time after the interlock switch is turned on.
Inrush current is reduced and soft start is possible.

As a result, damage to the switch contacts is reduced and electronic components such as transistors are prevented from malfunctioning or malfunctioning. Furthermore, since the inrush current is small, it is possible to reduce the size of the choke coil for suppressing the inrush current, which has the effect that the size of the power supply device can be reduced and it can be manufactured at low cost. Incidentally, by making the chiyoke coil smaller, the size of the power supply device could be reduced by about 15%.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a timing chart of signals of the main parts of the embodiment, FIG. 3 is a circuit diagram showing a specific example of the on/off circuit of FIG. 1, and FIG. FIG. 4 shows a timing chart similar to that shown in FIG. 2 for a conventional device. DESCRIPTION OF SYMBOLS 1... Rectifier, 2... Transformer, 3... Transistor for switching regulator, 4... Chi York coil, 6... PWM signal generation circuit, 7...
...Feedback circuit, 8a-8n...Load, 9
...On-off circuit, 10...Delay circuit, SW1,
SW2...First and second interlock switch.

Claims (1)

[Claims for Utility Model Registration] (1) In a power supply device having a switching transistor and a PWM signal generating means for driving it on the primary side of a transformer, and a first switching means for turning on/off the output on the secondary side. , comprising an on-off means for outputting a signal for turning on and off the operation of the PWM signal generating means, and a remote signal supply means for supplying a remote signal of ON or OFF to the on-off means, after the switch means is turned on. A power source starting device characterized in that the remote signal is input to the on/off means after a predetermined time. (2) The power supply starting device according to claim 1, wherein the remote signal supply means is comprised of a second switch means and a delay means. (3) The power supply starting device according to claim 1 or 2, wherein the first and second switch means are interlock switches.