JPS626870Y2 - - Google Patents

Description

[Detailed description of the invention] In the present invention, for example, a primary coil and a secondary coil are wound around a magnetic core having a nonlinear region, and magnetic flux is orthogonally coupled to the primary coil and secondary coil. Regarding the protection circuit of an isolated constant voltage power supply device configured using a transformer wrapped with a control coil for magnetic flux control, we particularly aim to ensure the protection function and eliminate the consumption of reactive power during protection operation. This is what I did.

First, a primary coil and a secondary coil are wound around a magnetic core having a nonlinear region, and this first coil is wound around a magnetic core having a nonlinear region.
Figure 1 shows a protection circuit for an insulated constant voltage power supply constructed using a transformer around which a control coil for magnetic flux control is wound so that the magnetic flux is orthogonally coupled to the secondary coil and the secondary coil. There is something like that. That is, in FIG. 1, AC voltage from a commercial AC power source 1 is supplied to a rectifier and smoothing circuit 2 to convert it into a DC voltage, and the output terminal of this rectifier and smoothing circuit 2 is connected to a transformer 3.
It is connected to the collector of an NPN transistor 5 for switching through a series circuit of the primary coil N ₁ and the choke coil 4, and the emitter of this transistor 5 is grounded, and a damper diode is connected between the collector and emitter of this transistor 5. 6
and a parallel circuit of a resonance capacitor 7 is connected. Further, 8 indicates an oscillator that oscillates at a frequency of, for example, 15 kHz to 20 kHz, and supplies the output signal of this oscillator 8 to the base of an NPN type transistor 9 for driving.
The emitter of this transistor 9 is grounded and the collector of this transistor 9 is connected to the driving transformer 1.
0 primary coil 10a and a low-pass filter 11 made up of a resistor 11a and a capacitor 11b. Through a series circuit with a low-pass filter 11 consisting of a resistor 11a and a capacitor 11b, a DC voltage force approximately half of the output DC voltage of the rectifying and smoothing circuit ₂ is obtained. ₂
The collector of this transistor 9 is grounded via a series circuit of a capacitor 12 and a resistor 13, and the secondary coil 1 of the drive transformer 10
A switching signal having a frequency of, for example, 15 kHz to 20 kHz is supplied from 0b to the base of the switching transistor 5. The middle point of _the secondary coil _N2 of the transformer 3 is grounded, and a small capacitor 14 for parametric oscillation and waveform shaping is connected between both ends of the secondary coil N2.
N ₂ is connected to a rectifier circuit 15 consisting of two diodes, and the output side of this rectifier circuit 15 is grounded via a smoothing capacitor 16, and the DC output voltage Eo obtained at the output side of this rectifier circuit 15 is so as to supply it to the load 18 via the fuse 17,
Also, the output side of the rectifier circuit 15 is connected to this DC output voltage Eo.
A control circuit 19 is provided which detects the magnitude of and supplies a control current Ic to the control coil Nc of the transformer 3.

Here, the transformer 3 has a structure as shown, for example, in FIG. The cores 20, 2 have magnetic legs 3A, 3B, 3C, and 3D extending in the direction and having the same cross-sectional area.
1 is magnetic legs 3A, 3B, 3C, 3D and 3A, 3
B, 3C, and 3D face each other with their ends touching each other, and are therefore assembled to form a cube or rectangular parallelepiped as a whole. In addition,
The cores 20 and 21 are made of ferrite material, for example.

Furthermore, the primary coil N _{1 is wound across the magnetic legs 3B and 3D of the core 20, and the secondary coil N 2 is} wound across the magnetic legs 3A and 3C of the core 20, A control coil Nc is wound around the magnetic legs 3A and 3B of the core 21. Therefore, in this case, coils N ₁ and N ₂ are transformer coupled, and coils N ₁ , N ₂ and Nc are orthogonally coupled, but the coupling coefficient between coils N ₁ and N ₂ in this case is 0.5.
It is said to be about ~0.6.

The magnetic flux distribution state of such a transformer 3 is shown in FIGS. 3A and 3B. That is, the excitation current of coil N ₁ is I ₁ ,
If the oscillation current of coil N ₂ is I ₂ and the load current taken out from coil N ₂ is I _L , then the total magnetomotive force I of this transformer 3 is: NI=N ₁ I ₁ + N ₂ I ₂ −N ₂ I _L ......(1). The magnetic flux generated during the positive half cycle of the output voltage due to this magnetomotive force NI is +φ _S (Figure 3A), and the magnetic flux generated during the negative half cycle is -
φ _S (Fig. 3B), and the control coil Nc,
The magnetic flux generated by the control current Ic flowing through this is φ
_C , then during the positive half-cycle period (Fig. 3A), the magnetic fluxes φ _S and φ _C subtract each other in the magnetic legs 3A and 3B, and the magnetic fluxes φ _S and φ _C in the magnetic legs 3B and 3C
are added together, resulting in a negative half-cycle period (Figure 3B)
has an inverse relationship.

Therefore, for example, in the B-H characteristic (magnetization characteristic) of FIG. 4, the operating point of the magnetic legs 3A, 3D at the peak of the positive half cycle period is point a,
The operating point of the magnetic legs 3B, 3C is point b, and the magnetic legs 3B, 3C at the peak of the negative half cycle period.
The operating point of is point c, and the operating point of magnetic legs 3A and 3D is point d. Therefore, the operating range of the magnetic legs 3A, 3D is the section indicated by the arrow 1A, the operating region of the magnetic legs 3B, 3C is the section indicated by the arrow 1B, and the output voltage during the positive half-cycle period is the range indicated by the magnetic legs 3A, 3D at point a. It is determined by the magnetic flux density of 3D + Bs, and the output voltage during the negative half cycle period is determined by the magnetic flux density of magnetic legs 3B and 3C at point c - Bs
It will be decided.

Points a and c change depending on the magnetic flux φ _C , and the magnetic flux φ _C changes depending on the control current Ic, so if the current Ic is controlled, the output voltage can be controlled. This output voltage Eo(t) is Eo(t)=d/dtφ(t)=d/dt{Li(t)
} =Ldi(t)/dt+i(t)dL/dt...
...(2) =Ndφ(t)/dt+i(t)dL/dt...
...(2)', where the first term is the voltage induced by the transformer coupling, and the second term is the voltage induced by the parametric coupling. That is, the output voltage Eo(t) includes a voltage due to transformer coupling and a voltage due to parametric oscillation. Note that the ratio of both voltages differs depending on the coupling coefficient between the coils N ₁ and N ₂ , that is, the shape of the core and the method of winding the coils.

Therefore, as shown in FIG. 5, the magnetic flux when Ic=0 is φ ₁ , the magnetic flux in the above additive state is φ ₂ , the magnetic flux in the above subtractive state is φ ₃ , the magnetic fluxes φ ₁ and φ ₂ ,
If the changes from φ ₃ are Δφ ₂ and Δφ ₃ , Ic=
The output voltage e _O in the case of 0 is e _O =Nd(φ ₁ +φ ₁ )/dt+R/N(φ ₁ +
φ ₁ )dL/dt =2φ ₁ (KNf+R/N dL/dt)……(
3) becomes. In addition, the output voltage e _OS when Ic≠0 and the magnetic flux φ is in the nonlinear region is e _OS = Nd (φ ₂ + φ ₃ )/dt+R/N (φ ₂ +
φ ₃ ) dL/dt = {2φ ₁ (Δφ ₃ −Δφ ₂ )} {KNf+R/N dL/dt} (4).

Since Δφ ₃ >Δφ ₂ due to the nonlinearity of the B-H characteristic, e _O −e _OS =(Δφ ₃ −Δφ ₂ )(KNf+R/N dL/
dt)......(5) Furthermore, if points e and b are in the saturation region, Δφ ₂ 〓0, so e _O −e _OS = Δφ ₃ (KNf+R/N dL/dt)...
… (5)′ becomes. Therefore, according to this equation, it can be seen that the output voltage can be controlled by controlling the change in magnetic flux Δφ ₃ using the control current Ic.

According to the power supply device shown in FIG. 1 using such a transformer 3, an operation similar to that of a horizontal deflection circuit of a television receiver is performed according to the on/off switching operation of the transistor 5, and the collector of the transistor 5 is The voltage changes as shown in FIG. 6A, and an exciting current _I1 as shown in FIG. 6B flows through the primary coil _N1 of the transformer 3. Here, the choke coil 4 limits the collector current of the transistor 5 during its on period to stabilize its switching operation. Since the transformer 3 is excited by the current I ₁ ,
The output voltage and _current I ₂ having the waveforms shown in FIG. DC voltage is supplied.
FIG. 6E shows the induced voltage in the magnetic legs 3A and 3D of the transformer 3, and FIG. 6F shows the induced voltage in the magnetic legs 3B and 3C, respectively. In addition, Fig. 6G shows the transformer 3
The current flowing through the center tap of the secondary coil N ₂ is unbalanced because the current I ₁ is unbalanced between the positive half cycle period and the negative half cycle period.

Furthermore, the DC output voltage Eo from the rectifier circuit 15
is detected by the control circuit 19, and a control current Ic is applied to the control coil Nc of the transformer 3 according to the detected output.
flow. That is, for example, if the DC output voltage Eo increases, the control current Ic increases and the maximum magnetic flux density increases.
As Bs becomes smaller, the DC output voltage Eo becomes lower, and conversely, when the DC output voltage Eo becomes lower, the DC output voltage Eo is controlled to be increased, and the DC output voltage Eo is stabilized at a constant level.

The power supply device shown in FIG. 1 has an input side and an output side connected by a transformer 3, so that it constitutes an isolated constant voltage power supply device.

The protection circuit of the conventional insulated constant voltage power supply as shown in FIG. 1 was constructed as follows. That is, in Fig. 1, the primary coil of transformer 3 N ₁
and the connecting point of the chiyoke coil 4 to the capacitor 2
2. Ground through a series circuit of resistors 23 and 24, connect the connection point of these resistors 23 and 24 to the cathode of a Zener diode 25 for overvoltage detection, and connect the anode of this Zener diode 25 to the resistor 26 and An SCR 28 that is grounded through a parallel circuit of a capacitor 27 and connects the anode of this Zener diode 25 to an SCR 28 that constitutes a switching element.
The cathode of this SCR 28 is grounded, and the anode of this SCR 28 is connected to the connection point of the low-pass filter 11 and the primary coil 10a of the drive transformer 10. The connection point with the next coil 10a is grounded via the SCR 28.

In the protection circuit of the conventional isolated constant voltage power supply as shown in FIG. 1, when the DC output voltage Eo supplied to the load 18 becomes an overvoltage, the secondary coil _N2 of the transformer 3 becomes an overvoltage. This transformer 3
The primary coil _N1 also becomes overvoltage, and when this overvoltage is detected by Zener diode 25,
Since the gate signal is supplied to the gate of the SCR 28, this SCR 28 is turned on, and since the connection point of the low-pass filter 11 and the primary coil 10a of the transformer 10 is grounded, the switching signal is not supplied to the base of the transistor 5, and the transistor 5 is turned on. The switching operation of the power supply device is stopped, and the operation of the power supply device is stopped, so that the power supply device can be protected.

In Fig. 1, an overvoltage protection circuit is connected to the primary coil _N1 side of the insulated constant voltage power supply.
The Zener diode 25 detects the AC output voltage from the connection midpoint of the primary coil _N1 and the choke coil 4, conducts the SCR 28 in the event of an overvoltage, and grounds the power supply to the drive transistor 9 of the switching transistor 5 to eliminate the overvoltage. However, because the primary coil N ₁ and the secondary coil N ₂ are loosely coupled, the secondary DC output voltage Eo and 1
When the AC input voltage is abnormally high and the load-side fuse 17 is disconnected due to a load short circuit, the influence of leakage magnetic flux increases, and the correlation between the next-side AC input voltage and the next-side AC input voltage increases, resulting in an overvoltage condition. In addition, even if the overvoltage protection circuit operates in such an uncontrollable state, the AC input voltage will be applied to the rectifying and smoothing circuit 2 and the live state will continue, which is dangerous. However, there is a drawback that power continues to be wasted through the discharging resistors R ₁ and R ₂ of the smoothing capacitor of the rectifying and smoothing circuit 2.

In view of these points, the present invention is designed to improve the above-mentioned drawbacks.

An embodiment of the protection circuit of the insulated constant voltage power supply according to the present invention will be described below with reference to FIG. In FIG. 7, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In the example shown in FIG. 7, one end of the commercial AC power source 1 is connected to the input side of the rectifying and smoothing circuit 2 via a connection switch 29a whose on/off is controlled by an electromagnetic device 29, which will be described later. Resistor R ₁ that can obtain a DC voltage approximately 1/2 of the output voltage
The connection point of R ₂ is connected to a drive transistor via a series circuit of a connection switch 29b whose on/off is controlled in conjunction with a connection switch 29a by an electromagnetic device 29 (described later), a resistor 11a, and a primary coil 10a of the drive transformer 10. Connect to the collector of 9. Also, both ends of this commercial AC power supply 1 are connected to each other via a main power switch 30 and a series circuit of a primary coil 31a of a transformer 31.
One end of the secondary coil 31b is grounded, the other end of this coil 31b is connected to a rectifier circuit 32, and the output side of this rectifier circuit 32 constitutes a switching element via a parallel circuit of an electromagnetic device 29 and a diode 33. It is connected to the collector of an npn transistor 34, and the emitter of this transistor 34 is grounded via a diode 35. Further, 36 indicates a flip-flop circuit, and this flip-flop circuit 36
is configured so that its output side is always at a high level "1" when the main power switch 30 is turned on, and the output side of this flip-flop circuit 36 is connected to the base of the transistor 34, and this transistor 3
4 is grounded via a resistor 37. In this case, when the main power switch 30 is turned on, the output side of the flip-flop circuit 36 becomes high level "1", so the transistor 34 becomes conductive, and the direct current from the rectifier circuit 32 flows through the electromagnetic device 29, and the connection is made. Switches 29a and 29b are turned on, respectively. Further, 36a indicates a trigger terminal of the flip-flop circuit 36 to which a power control signal from a remote control device (not shown) is supplied, and each time the power control signal is supplied to the trigger terminal 36a, the output side of the flip-flop circuit 36 is Since the signal level can be inverted, the transistor 34 can be turned on and off, and the connection switches 29a and 29b can be turned on and off using a remote control device.

In this example, the output side of the rectifier circuit 15 is grounded through a series circuit of resistors 23 and 24 constituting an overvoltage detection circuit, and the connection point of the resistors 23 and 24 is connected to a Zener diode 25 for overvoltage detection. and the anode of this Zener diode 25 is connected to the resistor 26 and the capacitor 2.
The Zener diode 25 is grounded through a parallel circuit of 7, and the anode of the Zener diode 25 is connected to the gate of an SCR 28 constituting a switching element. Also, while grounding the cathode of this SCR28,
Connect the anode of SCR 28 to the base of transistor 34. The rest of the structure is the same as in FIG. 1.

In this invention, when the main power switch 30 is turned on, the output side of the flip-flop circuit 36 becomes high level "1" and the transistor 34 is turned on, so the electromagnetic device 29 is operated and the connection switches 29a and 29b are turned on. shall be. 1st during steady state
It operates in the same manner as shown in the figure and can supply a constant voltage to the load 18. In addition, the input side and output side are transformers 3,
Since they are connected through 31, an insulated constant voltage power supply device is constructed in the same manner as in FIG. Further, in this example, the electromagnetic device 29 can be controlled by a control signal from a remote control device to turn on and off the connection switches 29a and 29b constituting the power switch, so that remote control is possible.
In addition, in the present invention, when the DC output voltage Eo supplied to the load 18 becomes an overvoltage, a gate signal is supplied to the gate of the SCR 28 via the Zener diode 25 for overvoltage detection, turning on the SCR 28 and turning on the transistor 34. ground the base of
When this transistor 34 is turned off, the electromagnetic device 29
is inoperative, and the connection switches 29a and 29b constituting the power switch are turned off. Therefore, the operation of the power supply device is stopped and the live parts are quickly eliminated, and at the same time, power loss during the operation of the protection circuit is eliminated. According to experiments, when the resistance values of resistors 11a, R ₁ and R ₂ were set to 4.4 kΩ, 150 kΩ and 150 kΩ, respectively, and the commercial AC power supply was set to 100 V, the power loss was 4.1 W compared to the conventional example shown in Figure 1. It was confirmed that the

As described above, in the present invention, when the constant voltage control function is impaired or the DC output voltage becomes an overvoltage due to the load 18 being opened, the overvoltage protection circuit is activated and the component or load 18 is activated. can protect against damage. In addition, in the present invention, a connection switch 2 that detects overvoltage on the secondary coil _N2 side (load side) and configures a power switch is installed.
Since 9a and 29b are turned off and the AC power input circuit is open, the protection function is ensured, and there is no active part during the operation of the protection circuit, which has the advantage of eliminating reactive power consumption.

Further, FIGS. 8 and 9 show other embodiments of the present invention, and in FIGS. 8 and 9, parts corresponding to those in FIG. Omitted. In FIG. 8, the output side of the rectifier circuit 15 is grounded through a series circuit of resistors 23 and 24 constituting a voltage detection circuit, and the connection point of the resistors 23 and 24 is connected to a pnp transistor 38 constituting a switching element. The emitter of this transistor 38 is grounded via a Zener diode 25a for overvoltage detection, and the emitter of this transistor 38 is connected to the output side of the rectifier circuit 32 via a resistor 39.
8 collector with electromagnetic device 29 and diode 33
It is connected to the collector of the transistor 34 through a parallel circuit. The rest of the structure is the same as that shown in FIG. 7.

In this Figure 8, under normal conditions, transistor 3
The voltage supplied to the base of 8 is low and this transistor 38 is on, and when there is an overvoltage, the voltage at the base of this transistor 38 becomes high, so this transistor 38 is turned off and the power supply to the electromagnetic device 29 etc. is stopped. . Therefore, it is easy to understand that the same effect as in FIG. 7 can be obtained in FIG. 8 as well.

In FIG. 9, the voltage dividing resistors 19a and 19b for error voltage detection of the control circuit 19 in FIG. 7 are also used as resistors 23 and 24 constituting the overvoltage detection circuit, and the resistors 23 and 24 are omitted. The rest of the structure is the same as that shown in FIG. 7. It is easy to understand that the same effect as in FIG. 7 can be obtained in FIG. 9 as well.

It goes without saying that the present invention is not limited to the above-described embodiments, and that various other configurations may be adopted without departing from the gist of the present invention.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an example of a protection circuit of a conventional isolated constant voltage power supply device, Fig. 2, Fig. 3, Fig. 4,
Figures 5 and 6 are diagrams for explaining the transformer, Figure 7 is a configuration diagram showing an embodiment of the protection circuit of the insulated constant voltage power supply of the present invention, and Figures 8 and 9 are diagrams for explaining the transformer. FIG. 3 is a configuration diagram showing another embodiment of the present invention. 1 is a commercial AC power supply, 2 is a rectifier and smoothing circuit, 3, 1
0 and 31 are transformers, 5, 9 and 34 are transistors, 8 is an oscillator, 15 and 32 are rectifier circuits, 18 is a load, 19 is a control circuit, 2
5 is a Zener diode, 28 is an SCR, 29 is an electromagnetic device, 29a and 29b are connection switches, 36 is a flip-flop circuit, and 36a is a power supply control signal input terminal.

Claims (1)

[Scope of utility model registration request] The commercial power supply is rectified and smoothed through a relay-driven power switch, and the rectified and smoothed output signal is supplied to a switching element that intermittents at high frequency through the primary coil of the output transformer, and then rectified from the secondary coil of the transformer. The insulation is configured to supply a DC output voltage to a load via a smoothing circuit, and to stabilize the DC output voltage by supplying a control current that changes according to the DC output voltage to an output stabilization control circuit. In the protection circuit of a constant voltage power supply, the relay for the power switch is used to turn on and off the isolated constant voltage power supply.
It is controlled by a signal from a remote control device that is always operating regardless of whether it is off or not, and voltage abnormality is detected from the DC output voltage side, and when an abnormal voltage is detected, the relay is controlled to turn off the power switch. 1. A protection circuit for an isolated constant voltage power supply device.