JPH04245715A - Non-contact-making switching circuit and power supply device - Google Patents

Abstract

PURPOSE:To extend the service life of a contactless switching circuit and to improve its reliability by attaining the contactless switching circuit using an n-channel MOS transistor(TR) by a simple circuit constitution. CONSTITUTION:The contactless switch circuit is provided with an n-channel MOS field effect transistor(FET) inserted into a negative pole side feeder to a load 50 in series so that its source electrode S and drain electrode D are respectively connected to the power supply side and the load side, a bias circuit 52 for applying a bias voltage to the gate electrode G of the MOS FET 51 to turn on the MOS FET 51 and a bias stopping circuit 53 for turning the MOS FET 51 to an OFF state by stopping the impression of the bias voltage by the circuit 52.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact switch circuit using an N-channel MOS field effect transistor, and a power supply device using this non-contact switch circuit. The non-contact switch circuit according to the present invention is particularly suitable for turning on/off a large DC current, and can be used in a DC current on/off circuit in a large capacity power supply, a charger, a large current circuit, etc. There is a demand for circuits that turn on/off such a large amount of direct current to have improved reliability and extended life by being contactless.

0010

2. Description of the Related Art Conventionally, knife switches and no-fuse breakers (circuit breakers) have been known as circuits for turning on and off a large amount of direct current. All of these devices turn on/off direct current using mechanical contact structures.

[0011] The conventional DC current on/off circuit described above turns the DC current on/off using mechanical contacts. The contacts were easily damaged by the sparks generated at the contacts during switching, and there were problems with their lifespan and reliability. Therefore, a method can be considered to make the contacts non-contact using semiconductor elements such as transistors, but such semiconductor elements have a large power loss when conducting, so especially in circuits that turn on/off large amounts of direct current. Conventionally, circuits based on the above-mentioned mechanical contact structure have been used exclusively, even though they have problems with lifespan and reliability.

On the other hand, in recent years, low-loss MOS field effect transistors (hereinafter simply referred to as MOS transistors) have been developed and have reached the stage where they are put into practical use. It became possible to consider using it in place of the structure to make it contactless. In particular, the use of N-channel MOS transistors is desired because their power loss during conduction is small.

[0020]

[Problems to be Solved by the Invention] In order to construct a DC current on/off circuit using an N-channel MOS transistor, the source is connected in series with the positive power supply line to the load, and the drain is connected to the power supply side. A MOS type transistor is inserted with the voltage on the load side, and by controlling its gate-source voltage, the MOS type transistor is turned on/off to supply/cut off direct current.

However, in order to turn on a MOS transistor, it is necessary to make the gate voltage higher than the source voltage to the positive side, and for this purpose, it is necessary to generate a gate voltage higher than the power supply voltage. However, in normal cases, such a high voltage does not exist in the circuit, so it is necessary to create a gate voltage with special circuitry, resulting in a complicated circuit configuration.

The present invention has been made in view of the above circumstances, and its purpose is to realize a non-contact switch circuit using an N-channel MOS transistor with a simple circuit configuration, and to improve the performance of the non-contact switch circuit. The aim is to extend life and improve reliability. Another object of the present invention is to provide a power supply device using such a non-contact switch circuit.

[0030]

[Means for Solving the Problems] FIG. 1 is a diagram illustrating the principle of the present invention. In order to solve the above-mentioned problems, the non-contact switch according to the present invention has an N-channel switch inserted in series with the negative power supply line to the load 50 with the source electrode S on the power supply side and the drain electrode D on the load side. a MOS field effect transistor 51; a bias circuit 52 that applies a bias voltage to the gate electrode G of the MOS field effect transistor 51 to turn on the MOS field effect transistor 51; and application of the bias voltage by the bias circuit 52. The bias stop circuit 53 stops the MOS type field effect transistor 51 and turns it off.

[0031] Furthermore, the non-contact switch circuit according to the present invention includes:
The above-mentioned non-contact switch circuit further includes an overcurrent detection circuit 54 that detects an overcurrent flowing through the load 50, and when an overcurrent is detected by the overcurrent detection circuit 54, the MOS
The device is configured to stop applying a bias voltage to the field effect transistor 51 and turn it off.

[0032] Furthermore, the non-contact switch circuit according to the present invention includes:
In each non-contact switch circuit described above, the bias circuit 5
2 is a voltage divider that generates a bias voltage to be applied between the source electrode and the gate electrode of the MOS field effect transistor by dividing the output voltage of the power supply, and the bias stop circuit 53 divides the gate electrode of the MOS field effect transistor from the source. It is configured to be a switch means for shorting the electrodes.

Further, the power supply device according to the present invention has an AC power supply 6
An AC/DC conversion circuit 62 that converts AC power from 1 to DC power and supplies power to a load; a DC power supply 63; It is equipped with any of the above-mentioned non-contact switch circuits that turn on/off the power supply.

Further, the power supply device according to the present invention is the above-described power supply device, further comprising an AC power supply stop detection circuit 64 that detects the stoppage of the supply of AC power from the AC power supply 61, and the non-contact switch circuit detects the stoppage of the supply of AC power from the AC power supply 61. The inside is in the off state, but when the AC power supply stop detection circuit 64 detects that the AC power supply has stopped, it becomes the on state and supplies DC power from the DC power supply 63 to the load instead of the AC/DC conversion circuit 62. configured to do so.

Further, the power supply device according to the present invention includes a DC power supply 6
3 is a battery, further comprising an over-discharge detection circuit 65 for detecting over-discharge of the battery, and configured to turn off the non-contact switch circuit when over-discharge of the DC power supply 63 is detected by the over-discharge detection circuit 65. be done.

Further, in the power supply device according to the present invention, in each of the power supply devices described above, the DC power from the AC/DC conversion circuit 62 and the DC power from the non-contact switch circuit are supplied to the load via the stabilized DC power supply circuit 67. configured to be powered by the

[0040]

[Operation] In the non-contact switch circuit according to the present invention, the bias voltage generated by the bias circuit 52 is applied to the gate electrode G of the MOS type field effect transistor 51 to turn it on, and the bias voltage is turned on by the bias stop circuit 53. The on/off of the circuit is controlled by turning it off by stopping the application of .

Furthermore, when an overcurrent flows through the load, the overcurrent detection circuit 54 detects it, and accordingly stops applying bias voltage to the MOS field effect transistor 51 to turn it off. Protects the circuit from electrical current.

As the bias circuit 52, a voltage dividing circuit such as a resistor voltage divider can be used to divide the power supply voltage, and as the bias stop circuit 53, a switch can be used to short-circuit between the gate and source of the transistor 51. , This allows the circuit configuration to be simplified.

Further, in the power supply device according to the present invention, power is supplied to the load from the AC power supply 61 during normal times and from the DC power supply 63 during backup. In this case, turning on the power supply from the DC power supply 63 to the load 50 during backup is controlled using the above-mentioned non-contact switch circuit, but since the MOS type field effect transistor 51 is used, the power supply line during power supply is The power loss in the area is reduced. Furthermore, if there is a DC stabilized power supply or the like in the subsequent stage, the input conditions are relaxed.

Furthermore, when the AC power supply 61 experiences a power outage, it is immediately detected by the AC power supply stop detection circuit 64, and the non-contact switch circuit is switched to supply power from the DC power supply 63 side. It is possible to prevent instantaneous interruptions in the power supply.

When a battery is used as the DC power source 63, over-discharge of the battery is detected by the over-discharge detection circuit 65, and when the battery is over-discharged, the non-contact switch circuit is opened to stop the power supply from the battery. Overdischarge can be prevented.

Power is supplied to the load 50 by a DC stabilized power supply 67.
It is possible to supply a more stable DC voltage.

[0050]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the same reference numerals are given to the same circuit elements throughout the figures described below. FIG. 2 shows a non-contact switch circuit as an embodiment of the present invention. In the figure, DCIN is the DC input from the DC power supply, and DCOUT
is the DC output applied to the load. DC input DCI
N is transmitted to the load side by the positive side power supply line 5 and the negative side power supply line 6, respectively, and becomes a DC output DCOUT.

Reference numeral 1 denotes an N-channel MOS type transistor (MOS type field effect transistor) that can handle a large amount of direct current, and its drain D
is inserted on the load side and the source S on the power supply side, so that the supply of DC power to the load can be turned on and off. Resistors 21 and 22 are connected in series between power supply lines 5 and 6 to form a resistive voltage divider circuit 2.
A gate voltage for making the MOS transistor 1 conductive is generated by dividing the voltage at IN, and is applied to the gate G. . The switch 4 is a circuit for shorting the gate G and source S of the MOS transistor 1, and may be a mechanical switch or a semiconductor switch, and a small capacity one is sufficient.

To explain the operation of this embodiment circuit, when it is desired to supply the DC output DCOUT to the load, the switch 4 is opened. As a result, the gate voltage is applied to the MOS transistor 1 from the resistor voltage divider circuit 2 and it becomes conductive, and the DC input DCIN becomes the DC output DCOUT on the load side.
is applied as .

On the other hand, when it is desired to cut off the power supply to the load, the switch 4 is closed. As a result, the gate and source of the MOS transistor 1 are short-circuited, the MOS transistor 1 is cut off, and the power supply to the load is cut off.

Various modifications are possible in implementing the invention. For example, the circuit that applies the gate voltage to the MOS transistor 1 is not limited to the resistor voltage divider circuit 2 of the embodiment, but may be a circuit that generates the gate voltage using a Zener diode, or a circuit that generates the gate voltage using a battery. It may also be a circuit that generates the signal.

Another embodiment of the invention is shown in FIG. The difference from the above embodiment is that an overcurrent detection section 8 and a switch 7 are provided. The overcurrent detection section 8 is inserted in series on the power supply side from the MOS transistor 1 of the negative power supply line 6, and detects when an overcurrent flows through the load. The switch 7 is a switch circuit that has a self-holding function and its release function, and is configured to switch from off to on by receiving an overcurrent detection signal from the overcurrent detection section 8, and to self-maintain that state. Thus, the circuit is connected so that the gate G of the MOS transistor 1 is short-circuited to the source S.

If such an overcurrent detection mechanism is provided, when an overcurrent that requires circuit interruption flows through the load, the overcurrent detection section 8 detects this and sends an overcurrent detection signal to the switch 7. The switch 7 is turned on, thereby cutting off the MOS transistor 1, cutting off the power supply to the load, and protecting the circuit.

The connection position of the overcurrent detection section 8 is not limited to the embodiment shown in FIG. 3; for example, it may be inserted in series with the positive power supply line 5 as shown in FIG. As shown in FIG. 3, it may be inserted in series on the load side of the negative power supply line 6 from the MOS transistor 1.

Next, a power supply device of the present invention using the above-mentioned non-contact switch circuit will be explained. This type of power supply device normally operates on AC power, but in the event of a power outage, it switches to a DC power source such as a backup battery to operate the device, so the system will not go down even in the event of an AC power outage. This is a power supply device that allows you to

FIG. 6 shows a conventional basic configuration of such a power supply device. In the figure, ACIN is an AC input from an AC power source such as a commercial AC, DCIN is a DC input from a DC power source such as a backup battery, and DCOUT is a DC output applied to a load. The AC input ACIN is converted to a predetermined voltage by the power transformer 11, and then the rectifier and smoother 1
2, the DC output is rectified, smoothed, and converted to DC, and then input to the DC stabilized power supply 13, where the DC output is stabilized.
Power is supplied to the load as In addition, the DC input DCIN is input to the DC stabilized power supply 13 via the reverse current prevention diode 14, so that in the event of a power outage of the AC power supply, the AC input ACI
Supplying DC input to the DC stabilized power supply 13 instead of N,
Perform a backup.

In such a power supply device, in order to prevent power from being supplied to the DC stabilized power supply 13 from the DC input DCIN during normal operation, the DC input D
The voltage VIN of CIN is the output side voltage VO of the diode 14
It is designed to be lower than UT. However, such a circuit has the following problems.

a. When using a large current, a large current flows through the diode 14 during backup, resulting in a large voltage drop and power loss in the diode 14. However, in order to be able to use the battery for a long time during backup, it is necessary to minimize such voltage drop and power loss.

b. Since the diode 14 is a reverse current prevention diode, the voltage VIN of the DC input VIN must be lower than the output voltage of the rectifying and smoothing section 12 during normal operation using the AC input ACIN. In order to satisfy this condition over the input voltage fluctuation range of the AC input ACIN, it is necessary to make the minimum input voltage value of the AC input ACIN higher than the maximum input voltage value of the DC input DCIN. As a result, the DC stabilized power supply 13 is necessarily required to have a wide input voltage operating range, and such a DC stabilized power supply is disadvantageous in terms of component voltage withstand characteristics and increases in cost.

[0063] Such problems can be solved by using the above-described non-contact switch circuit according to the present invention in a power supply device. An example thereof is shown in FIG. In this embodiment, instead of the backflow prevention diode 14, the DC input DCIN is supplied to the input side of the DC stabilized power supply 13 via the non-contact switch circuit shown in FIG. In this embodiment, when the AC input ACIN is out of power, the switch 4 is turned off to make the MOS transistor 1 conductive, and the DC input DCIN is connected to the DC stabilized power supply 1.
3 to supply the stabilized DC output DCOUT to the load.

In the power supply device of FIG. 7, the voltage drop and voltage loss in MOS transistor 1 are small. In addition, since the DC input DCIN is normally cut off by the MOS transistor 1, there is no need to adjust the voltage value between it and the AC input ACIN side, thus reducing the input voltage operating range of the DC stabilized power supply 13. can do.

Switch 4 in FIG. 7 is an AC input ACIN.
If the system is configured to automatically detect a power outage and turn off, it is possible to automatically continue supplying power to the load without momentary interruption even in the event of a power outage. FIG. 8 shows a power supply device having such a configuration as another embodiment of the present invention. In the figure, 9 is a photocoupler, which is inserted into the circuit instead of the switch 4. The primary side of this photocoupler 9 is connected to the output side of the transformer 11, and the secondary side is a MOS
It is connected between the gate and source of the type transistor 1. The secondary side of this photocoupler 9 is conductive when there is an AC input ACIN, and is cut off when the AC input ACIN is out of power. Therefore, during normal operation when the AC input ACIN is input, the MOS transistor 1 is off and prohibits power supply from the DC input DCIN, and during a power outage, it is turned on and supplies power from the DC input DCIN to the DC stabilized power supply 13. Work like you do.

Of course, the connection position of the photocoupler 9 is not limited to the secondary side of the transformer 11, but may be connected to the primary side of the transformer 11, for example, as shown in FIG. Furthermore, the circuit may of course be constructed of a relay circuit having a mechanical contact structure, a semiconductor switch, or the like instead of a photocoupler. In addition, in consideration of maintenance such as testing of the power supply device, it is of course possible to configure the circuit so that the operation of this photocoupler is intentionally prohibited during maintenance and the MOS type transistor 1 is turned on/off using a manual switch. It is.

Further, in such a power supply device, a circuit for preventing over-discharge of the battery as a DC power source at the time of backup can be added, and FIG. 10 shows a power supply device as such an embodiment. In the figure, 10 is an overdischarge detection section, which is connected to monitor the voltage of the DC input DCIN (i.e., the output voltage of the backup battery), and when this falls below a predetermined discharge end voltage,
Sends an overdischarge detection signal to switch 7. The switch 7 is a circuit with the above-mentioned self-holding function, and when it receives the over-discharge detection signal, it shorts the source and drain of the MOS transistor 1, turns off the MOS transistor 1, and stops power supply from the battery. This is to prevent over-discharge. This power supply device in FIG.
It can also be used as a charger to charge the battery on the DC input DCIN side.

[0080]

Effects of the Invention As explained above, according to the present invention, it is possible to achieve N
It is possible to provide a non-contact switch circuit that can control on/off of a channel MOS type field effect transistor,
This makes it possible to extend the life of the switch circuit and increase its reliability.

Further, according to the power supply device of the present invention using such a non-contact switch circuit, since the voltage drop at the DC input section can be reduced, the backup time can be extended during backup with a battery, and the DC stabilized power supply can be The input voltage usage range of the DC/DC converter section can be narrowed, which contributes to reducing component withstand voltage characteristics and cost reduction.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a block diagram showing a non-contact switch circuit as an embodiment of the present invention.

FIG. 3 is a block diagram showing a non-contact switch circuit according to another embodiment of the present invention.

FIG. 4 is a block diagram showing a non-contact switch circuit according to another embodiment of the present invention.

FIG. 5 is a block diagram showing a non-contact switch circuit according to still another embodiment of the present invention.

FIG. 6 is a block diagram showing a conventional general power supply device.

FIG. 7 is a block diagram showing a power supply device as an embodiment of the present invention.

FIG. 8 is a block diagram showing a power supply device according to another embodiment of the present invention.

FIG. 9 is a block diagram showing a power supply device according to another embodiment of the present invention.

FIG. 10 is a block diagram showing a power supply device according to still another embodiment of the present invention.

[Explanation of symbols]

1: N-channel MOS type field effect transistor 2: Resistor voltage divider circuit 21, 22: Resistor 4, 7: Switch 5: Positive side power supply line 6: Negative side power supply line 8: Overcurrent detection section 9: Photocoupler 10: Overdischarge detection circuit 11: Transformer 12: Rectification smoothing section 13: DC stabilized power supply 14: Backflow prevention diode

Claims (7)

[Claims] Claim 1: An N-channel MOS field effect transistor (
51), a bias circuit (52) that applies a bias voltage to the gate electrode of the MOS field effect transistor to turn on the MOS field effect transistor, and a bias circuit (52) that stops applying the bias voltage by the bias circuit. The M
A non-contact switch circuit including a bias stop circuit (53) that turns off an OS type field effect transistor. 2. The overcurrent detection circuit further comprises an overcurrent detection circuit (54) for detecting an overcurrent flowing through the load, and when an overcurrent is detected by the overcurrent detection circuit, a bias voltage is applied to the MOS field effect transistor. 2. The non-contact switch circuit according to claim 1, wherein the non-contact switch circuit is configured to stop and turn it off. 3. The bias circuit is a voltage divider that divides a power supply voltage to generate a bias voltage to be applied between the source electrode and the gate electrode of the MOS field effect transistor, and the bias stop circuit generates a bias voltage to be applied between the source electrode and the gate electrode of the MOS field effect transistor. 3. The non-contact switch circuit according to claim 1, wherein the non-contact switch circuit is a switch means for short-circuiting a gate electrode of an effect transistor to the source electrode. 4. An AC/DC conversion circuit (
62), a DC power source (63), and a DC power source (63) inserted between the DC power source and the load to turn on/off the supply of DC power from the DC power source to the load. A power supply device equipped with the non-contact switch circuit described above. 5. Further comprising an AC power supply stop detection circuit (64) for detecting a stop in the supply of AC power from the AC power source,
The non-contact switch circuit is in an OFF state while AC power is being supplied, but when the AC power supply stop detection circuit detects that the AC power supply has stopped, it becomes an ON state and switches on the DC power instead of the AC/DC conversion circuit. 5. The power supply device according to claim 4, wherein the power supply device is configured to supply DC power from a power source to the load. 6. The DC power source is a battery, further comprising an over-discharge detection circuit (65) for detecting over-discharge of the battery, and when over-discharge of the DC power source is detected by the over-discharge detection circuit, the 6. The power supply device according to claim 4, wherein the power supply device is configured to turn off the non-contact switch circuit. 7. A claim configured such that the DC power from the AC/DC conversion circuit and the DC power from the non-contact switch circuit are supplied to the load via a DC stabilized power supply circuit (67). Item 7. The power supply device according to any one of items 4 to 6.