JPH09233678A - Power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-loss power supply device which has no influence on the operation of a circuit by limiting rush current by means of a resistor for liming current which is serially connected to a capacitor at the time of turning the power on and shorting the resistor for limiting current in the steady state. SOLUTION: A parallel circuit of a resistor R1 and a transistor Q1 is serially connected to an input capacitor C1 and the gate voltage of the transistor Q1 is supplied by a parallel circuit of a resistor R2 for dividing input voltage and a resistor R3 and a capacitor C2. At that time, a time constant determined by the resistors R2, R3 and the capacitor C2 is set larger than the one determined by the input capacitor C1 and the resistor R1. By this method, the transistor Q1 starts conducting after charging of the capacitor C1 is finished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention proposes a power supply device having a function of limiting an inrush current when the power is turned on.

[0002]

2. Description of the Related Art As a structure of a primary input side of a power supply device, there is a structure shown in FIGS. 1 in the figure
Is a primary power supply input terminal, 2 is a return terminal, 3 is a transformer, 4 is a switch element, and C1 is an input capacitor.

The primary input side circuit of the conventional power supply device is configured as described above, and the switching element switches the DC voltage input from the primary power supply input terminal through the transformer, so that power is supplied to the secondary side of the transformer. To transmit. At this time, the input capacitor supplies an AC current to the transformer and functions as an input filter, so that it is necessary to have a sufficient capacity.

[0004]

Since the primary input side circuit of the conventional power supply device is configured as described above, a large inrush current is input to the capacitor of the input section against a sudden rise of the voltage when the power is turned on. There is a risk that the fuse provided on the upstream side of the primary power source will be blown out and the fuse will blow out. In order to prevent this, if the fuse rating is selected so that it will not be blown by the inrush current when the power is turned on, the fuse rating will be unnecessarily high and the optimum fuse cannot be selected for the abnormal current. there were.

As shown in FIG. 10, there is a method of suppressing an inrush current by providing an inrush current prevention circuit composed of a thyristor or the like in front of the input capacitor. In this case, the inrush current prevention circuit is used as a power line. The loss due to the DC voltage drop may be a problem because it is connected in series.

The present invention has been made to solve the above problems, and its purpose is to limit an inrush current by a current limiting resistor connected in series with a capacitor at the time of power-on, and at the time of steady state. It is to provide a low-loss power supply device that does not affect the operation of the circuit by short-circuiting the current limiting resistor.

[0007]

According to a first aspect of the present invention, there is provided a power supply device in which a parallel circuit of an N-channel field effect transistor (N-channel FET) and a current limiting resistor is inserted in series with an input capacitor and a gate of the N-channel FET is inserted. A capacitor is connected in parallel with the resistor connected between the source terminal and the source terminal.

The power supply device according to the second invention is the first power supply device.
In addition to the invention described above, the gate of the N-channel FET is controlled when an overcurrent is detected, and a transistor is connected so as not to flow more than a constant current.

The power supply device according to the third invention is the second power supply device.
In addition to the invention of (1), a latch circuit that works to hold the N-channel FET at the cutoff when an overcurrent is detected is connected.

The power supply device according to the fourth invention is the third power supply device.
In addition to the invention described above, the N-channel FET is held in a cut-off state when an overcurrent is detected, and a latch circuit that works to stop the operation itself of the switch element is connected.

In the power supply device according to the fifth aspect of the invention, a parallel circuit of an N-channel field effect transistor (N-channel FET) and a current limiting resistor is inserted in series on the return terminal side of the input capacitor, and the gate of the N-channel FET is inserted. The voltage is supplied from the transformer winding.

The power supply device according to the sixth aspect of the invention is the fifth aspect.
In addition to the invention of (1), a latch circuit that works to stop the operation of the switching element itself when an overcurrent is detected is connected.

In the power supply device according to the seventh aspect of the invention, a parallel circuit of an N-channel field effect transistor (N-channel FET) and a current limiting resistor is inserted in series on the primary power supply input terminal side of the input capacitor to obtain an N-channel FET. The gate voltage of is supplied from the transformer winding.

The power supply device according to an eighth aspect of the invention is the seventh aspect.
In addition to the invention of (1), a latch circuit that works to stop the operation of the switching element itself when an overcurrent is detected is connected.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. Embodiment 1 of the present invention will be described below with reference to FIG. In FIG. 1, 1-4 and C1 are the same as the conventional device. R1 is a current limiting resistor, and Q1 is an N-channel FET. R2 and R3 are drive resistors for the N-channel FET, and C2 is a capacitor connected in parallel with R3.

Next, the operation will be described. At the moment when the power is turned on from the primary power supply input terminal 1 and the return terminal 2, Q1 is non-conducting and the input capacitor C1 is charged through R1. Therefore, the charging current to the input capacitor C1 is limited by R1. To be done. On the other hand, at the same time, C2 is R
Although it is charged by 2 and R3, by setting the time constant to be larger than the time constants of the input capacitors C1 and R1, the voltage Vg between the gate and the source of Q1 is set after the charging of the input capacitor C1 is completed. The threshold is exceeded and Q1 conducts.

Embodiment 2 FIG. FIG. 2 shows the second embodiment of the present invention, and is suitable for protection in the case where the input capacitor C1 is once charged and the input capacitor C1 is short-circuited after Q1 becomes conductive. That is, in FIG.
The overcurrent detection resistor R4 is inserted between the source of the Q1 and the return terminal 2 of the first embodiment, and the collector of the NPN transistor Q2 connected between the base and the emitter of this R4 is Q.
It is connected to the gate of 1.

In such a configuration, the operation at power-on is similar to that of the first embodiment, but Q1 is on and Q2 is off during steady operation. When C1 causes a short circuit failure during steady operation, an overcurrent flows in C1 and Q1. R4
Detects an overcurrent below the rated current of Q1 and turns on Q2 to control the gate-source voltage of Q1.
Even if a short circuit occurs, the voltage is suppressed below the level determined by R4.

Embodiment 3 FIG. 3 shows a third embodiment of the present invention, and like the second embodiment, it is suitable for protection when the input capacitor C1 is short-circuited after the input capacitor C1 is once charged and Q1 becomes conductive. . That is, in FIG. 3, CR1 is inserted between the gate of Q1 and the collector of Q2 of the second embodiment, and a latch circuit made up of Q3, Q4, and R5 to R8 that holds the state when Q2 is turned on is connected.

With such a configuration, the operation at power-on is the same as that in the first embodiment, and the same operation as that in the second embodiment is performed at the moment when C1 causes a short-circuit fault during steady operation. Then, in the second embodiment, the current level is changed to R4.
While Q1 is controlled so as to be limited to the overcurrent level determined by, in the third embodiment, Q1 is held in the cutoff state when overcurrent is detected.

Embodiment 4 FIG. FIG. 4 shows a fourth embodiment of the present invention, and like the second embodiment, it is suitable for protection when the input capacitor C1 is short-circuited after the input capacitor C1 is once charged and Q1 becomes conductive. . That is, in FIG. 4, the latch circuit Q3 of the third embodiment is used.
Connected to transmit a latch signal from the collector of the power supply device to the control circuit portion of the power supply device.

With such a configuration, the operation at power-on is the same as that of the first embodiment, and when C1 causes a short circuit fault during the steady operation, the same operation as that of the third embodiment is performed. In the third embodiment, Q1 is only kept in the cutoff state at the time of overcurrent detection, whereas in the fourth embodiment
Then, by further transmitting a latch signal to the control circuit of the power supply device, the operation of the switch element of the power supply device is stopped via the drive circuit, and the operation itself of the power supply device is stopped.

Embodiment 5 FIG. 5 shows Embodiment 5 of the present invention. In FIG. 5, 1-4 and C1, R
1 to R3 and Q1 are the same as those in the first embodiment. C
R2 and C3 are circuits for rectifying and smoothing the voltage from the second winding of the transformer 3, the output of which is Q1 through R2.
Connected to the gate.

Next, the operation will be described. Q is the moment when power is turned on from the primary power input terminal 1 and the return terminal 2.
Since 1 is non-conductive and the input capacitor C1 is charged with electric charge via R1, the charging current to the input capacitor C1 is limited by R1. When the switching element 4 starts switching, the second winding of the transformer 3 starts CR2.
An electric charge is injected into C3 via. Furthermore, this voltage is R
It is applied to the gate of Q1 through 2, the voltage Vg between the gate and source of Q1 exceeds the threshold value, and Q1 becomes conductive.

Embodiment 6 FIG. FIG. 6 shows a sixth embodiment of the present invention, and like the fourth embodiment, it is suitable for protection when the input capacitor C1 is short-circuited after the input capacitor C1 is once charged and Q1 becomes conductive. . That is, in FIG. 6, the overcurrent detection resistor R4 is inserted between the source of the Q1 and the return terminal 2 of the fifth embodiment, and the R4 is connected between the base and the emitter of the NPN transistor Q.
2 and Q3 that keeps that state once Q2 turns on,
A latch circuit composed of Q4 and R5 to R8 is connected, and the collector of Q3 which is the latch circuit is connected to transmit a latch signal to the control circuit section of the power supply device.

In such a configuration, the operation at power-on is the same as that in the fifth embodiment, and the overcurrent is detected at the moment R4 when C1 causes the short-circuit fault during the steady operation.
The latch signal is controlled by the latch circuits Q3 and Q4,
The operation of the switch element 4 is stopped through the drive circuit.
When the operation of the switch element 4 is stopped, the gate voltage of Q1 cannot be obtained, Q1 is cut off, and the operation of the power supply device itself is stopped.

Embodiment 7 FIG. 7 shows Embodiment 7 of the present invention. In FIG. 7, 1-4 and C1, R
1 to R3 and Q1 are the same as those in the first embodiment. However, Q1 and R1 are connected to C1 on the side of the primary power supply input terminal 1 contrary to the first embodiment. CR2, C
3 is a circuit for rectifying and smoothing the voltage from the second winding of the transformer 3 as in the fifth embodiment, the output of which is connected to the gate of Q1 through R2.

Next, the operation will be described. Q is the moment when power is turned on from the primary power input terminal 1 and the return terminal 2.
Since 1 is non-conductive and the input capacitor C1 is charged with electric charge via R1, the charging current to the input capacitor C1 is limited by R1. When the switching element 4 starts switching, the second winding of the transformer 3 starts CR2.
An electric charge is injected into C3 via. Furthermore, this voltage is R
It is applied to the gate of Q1 through 2, the voltage Vg between the gate and source of Q1 exceeds the threshold value, and Q1 becomes conductive.

Embodiment 8 FIG. 8 shows Embodiment 8 of the present invention, and like Embodiment 4, is suitable for protection in the case where the input capacitor C1 is short-circuited after the input capacitor C1 is once charged and Q1 becomes conductive. . That is, in FIG. 8, C1 and the return terminal 2 of the sixth embodiment
Insert an overcurrent detection resistor R4 between them, and use this R4 as a base,
NPN transistor Q2 connected between the emitters, and Q
Q3, Q4, R which keeps the state once 2 turns on
A latch circuit composed of 5 to R8 is connected, and the collector of Q3 which is the latch circuit is connected to transmit a latch signal to the control circuit section of the power supply device.

In such a configuration, the operation at power-on is the same as that in the sixth embodiment, and the overcurrent is detected at the instant R4 when C1 causes the short-circuit fault during the steady operation.
The latch signal is controlled by the latch circuits Q3 and Q4,
The operation of the switch element 4 is stopped through the drive circuit.
When the operation of the switch element 4 is stopped, the gate voltage of Q1 cannot be obtained, Q1 is cut off, and the operation of the power supply device itself is stopped.

[0031]

According to the first invention, the input capacitor C
The resistor R1 inserted in series with 1 can limit the rush power supply to the capacitor when the power is turned on. After charging the capacitor is completed, Q1 conducts, and during steady operation, AC current is supplied to the transformer 3 and the switch element 4 with low impedance, and C1 functions as an input filter. Therefore, there is an effect that it is possible to configure a power supply device in which the fuse is not erroneously blown by the inrush current.

According to the second invention, in addition to the effect of the first invention, even when C1 causes a short-circuit fault during steady operation, R4 detects an overcurrent below the rated current of Q1. , Q2 are turned on to control the gate-source voltage of Q1. Therefore, even if C1 causes a short circuit fault, the current is
Since it is suppressed below the level determined by 4, the overcurrent until the fuse is blown is limited, so that Q1 can be surely protected.

According to the third aspect of the invention, in addition to the second aspect of the invention, when C1 causes a short-circuit fault during steady operation, Q1 is surely kept in a cutoff state when an overcurrent is detected. This also has the effect of limiting the overcurrent level to the current level determined by R1.

According to the fourth aspect of the invention, in addition to the third aspect of the invention, not only can Q1 be reliably kept in the cutoff state at the time of overcurrent detection, but the power supply unit itself can be stopped. Therefore, this protection function has not only the protection at the time of short circuit of C1, but also the effect that it can be shared with the protection circuit of the power supply device itself against an overload or the like.

According to the fifth and seventh aspects of the invention, the resistor R1 inserted in series with the input capacitor C1 allows
It is possible to limit the inrush current to the capacitor when the power is turned on. After the switch element starts switching, Q1 conducts,
During steady operation, AC current is supplied to the transformer 3 and the switch element 4 with low impedance, and C1 functions as an input filter. Therefore, there is an effect that it is possible to configure a low-loss power supply device in which there is no possibility that the fuse is erroneously blown by the inrush current.

According to the sixth and eighth inventions, in addition to the fifth and seventh inventions, the input current can be limited and the operation of the power supply device itself can be stopped when the short circuit failure of C1 occurs. . Therefore, this protection function has not only the protection at the time of short circuit of C1, but also the effect that it can be shared with the protection circuit of the power supply device itself against an overload or the like.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a power supply device according to the present invention.

FIG. 2 is a diagram showing a second embodiment of a power supply device according to the present invention.

FIG. 3 is a diagram showing Embodiment 3 of the power supply device according to the present invention.

FIG. 4 is a diagram showing a power supply device according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a fifth embodiment of a power supply device according to the present invention.

FIG. 6 is a diagram showing a sixth embodiment of a power supply device according to the present invention.

FIG. 7 is a diagram showing Embodiment 7 of a power supply device according to the present invention.

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

FIG. 9 is a diagram showing a conventional DC power supply device.

FIG. 10 is a diagram showing a conventional DC power supply device.

[Explanation of symbols]

1 primary power supply input terminal, 2 return terminal, 3 transformer, 4 switch element, C1 input capacitor, C2
C3 capacitor, CR1, CR2 diode, R1
Current limiting resistors, R2, R3, R5-R8 resistors, R
4 Overcurrent detection resistor, Q1 N-channel field effect transistor, Q2, Q4 NPN transistor, Q3 P
NP transistor.

Claims (8)

[Claims] 1. A primary power supply input terminal, a return terminal paired with the primary power supply input terminal, an input capacitor inserted between the primary power supply input terminal and the return terminal, and a primary winding on the primary power supply input terminal. In a power supply device comprising a transformer connected to one end of the transformer and a switch element connected between the other end of the primary winding of the transformer and the return terminal, a current inserted between the input capacitor and the return terminal. A limiting resistor, an N-channel field effect transistor having a drain connected to one end of the current limiting resistor on the input capacitor side and a source connected to the return terminal side, a gate of the N-channel field effect transistor, and a primary power supply input terminal. A resistor connected between the resistor and a resistor connected between the gate and the source of the N-channel field effect transistor; A power supply device comprising a capacitor connected between the source and the gate. 2. An NPN transistor having a collector connected to the gate, an emitter connected to the return terminal and a base connected to the source, and an overcurrent detection resistor connected between the base and the emitter of the NPN transistor. The power supply device according to claim 1, further comprising: 3. An anode for the gate, a first NPN
A diode inserted to connect the cathode to the collector of the transistor, a PNP transistor having an emitter connected to the primary power supply input terminal, a resistor connected between the base and the emitter of the PNP transistor, and the P
A resistor connected between the base of the NP transistor and the collector of the first NPN transistor, and the first NP
A second NPN transistor having a collector connected to the collector of the N transistor and an emitter connected to the emitter, a resistor connected to the base of the second NPN transistor and the collector of the PNP transistor, and the second NP.
The power supply device according to claim 2, further comprising a resistor connected between the base and the emitter of the N-transistor. 4. The power supply device according to claim 3, wherein a signal from the collector of the PNP transistor is transmitted to a drive circuit for controlling the switch element via a control circuit. 5. A primary power supply input terminal, a return terminal paired with the primary power supply input terminal, an input capacitor inserted between the primary power supply input terminal and the return terminal, and a primary winding on the primary power supply input terminal. In a power supply device comprising a transformer having one end connected to and a switch element connected between the other end of the primary winding of the transformer and the return terminal, a current inserted between the input capacitor and the return terminal. A limiting resistor, an N-channel field effect transistor having a drain connected to one end of the current limiting resistor on the input capacitor side and a source connected to a return terminal side, and one end connected to a source of the N-channel field effect transistor. A second winding of the transformer, a diode having an anode connected to the other end of the second winding, and the diode A capacitor connected between the cathode of the N channel field effect transistor and the source of the N channel field effect transistor, a resistor connected between the cathode of the diode and the gate of the N channel field effect transistor, and a gate of the N channel field effect transistor. A power supply device comprising: a resistor connected between the source and the source. 6. A first NPN transistor having an emitter connected to the return terminal and a base connected to the source, and an overcurrent detection resistor connected between the base and the emitter of the first NPN transistor. A PNP transistor having an emitter connected to the primary power input terminal, a resistor connected between the base and the emitter of the PNP transistor, and a resistor connected between the base of the PNP transistor and the collector of the first NPN transistor. And a second NP having a collector connected to the collector and an emitter connected to the emitter of the first NPN transistor.
An N-transistor, a resistor connected to the base of the second NPN transistor and the collector of the PNP transistor, a resistor connected between the base and the emitter of the second NPN transistor, and a resistor connected from the collector of the PNP transistor. The power supply device according to claim 5, wherein the signal is transmitted to a drive circuit that controls the switch element via a control circuit. 7. A primary power supply input terminal, a return terminal paired with the primary power supply input terminal, an input capacitor inserted between the primary power supply input terminal and the return terminal, and a primary winding on the primary power supply input terminal. A power supply device comprising a transformer having one end connected to it and a switch element connected between the other end of the primary winding of the transformer and the return terminal, the power supply device being inserted between the input capacitor and the primary power supply input terminal. A current limiting resistor, an N channel field effect transistor having a drain connected to the primary power supply input terminal, a source connected to the input capacitor side of the current limiting resistor, and one end connected to the source of the N channel field effect transistor. A second winding of the transformer, a diode having an anode connected to the other end of the second winding, and the diode. A capacitor connected between the cathode of the diode and the source of the N-channel field effect transistor, a resistor connected between the cathode of the diode and the gate of the N-channel field effect transistor, and the N-channel field effect transistor. And a resistor connected between the gate and the source of the power supply. 8. A first NPN transistor having an emitter connected to the return terminal and a base connected to the return terminal side of the input capacitor; and the first NP.
An overcurrent detection resistor connected between the base and the emitter of the N transistor, a PNP transistor having the emitter connected to the primary power supply input terminal, a resistor connected between the base and the emitter of the PNP transistor, and the PNP.
A resistor connected between the base of the transistor and the collector of the first NPN transistor; a second NPN transistor having a collector connected to the collector of the first NPN transistor and an emitter connected to the emitter;
A resistor connected to the base of the NPN transistor and the collector of the PNP transistor, and a resistor connected between the base and the emitter of the second NPN transistor,
The power supply device according to claim 7, wherein a signal from the collector of the PNP transistor is transmitted to a drive circuit that controls the switch element via a control circuit.