JPH09243675A - Dc voltage detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a simply structured and inexpensive detection circuit by providing a diode bridge for switching DC voltage on a primary side and two switches on a secondary side and by switching at a high frequency by an oscillator. SOLUTION: Switches 11, 12 are alternately turned on/off by an oscillator 13, and consequently voltage V72 of one of secondary coils 7b of a transformer 1 and voltage V73 of the other coil 7c are switched, so that polarity of voltage V71 of a primary coil 7a of the transformer 7 is switched. When the voltage V71 is positive, diodes 4, 5 are conductive, while when it is negative diodes 3, 6 are conductive. The switching of the diodes causes current in proportion to DC input voltage Vin reduced by a shunt resistor 2 to flow to the primary coil 7a of the transformer 7, so that current in proportion to the input voltage Vin flows to the secondary coils 7b, 7c without magnetic saturation of the transformer 7. The secondary coil current is led by the switches 11, 12 to a shunt resistor 15, which converts it into DC output voltage Vout for outputting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device, and more particularly to an effective DC voltage detector applicable to a power supply device that needs to detect a DC voltage signal proportional to a DC voltage in an insulating manner.

[0002]

2. Description of the Related Art Conventionally, this type of detecting means is implemented by a circuit as shown in FIG. That is, the direct current voltage Vin is divided by the resistors 30 and 31 as the first detector, the direct current voltage Vin is detected without being insulated, and Vout is output. Alternatively, means for dividing the DC voltage Vin as a second detector by the voltage divider 32 and converting the divided signal into a frequency, which is implemented by a circuit as shown in FIG. 5 (hereinafter V / F converter 33). To obtain a frequency proportional to the voltage, to insulate this frequency by the photocoupler 34, and to generate a voltage proportional to the frequency by means of converting the frequency from the frequency to a DC voltage (hereinafter, F / V converter 35). The DC voltage Vin was detected and the DC output Vout was output.

FIG. 6 shows an application example of the prior art. The power conversion device 50 of FIG. 6 is a device that receives AC power from the AC input 51 and supplies power to the AC power load 58. As a specific example, an induction motor control device (VVVF
Device), an uninterruptible power supply (UPS device), and the like. The power conversion device 50 is a device that normally controls the AC power by converting the DC voltage 55 obtained by rectifying the input AC voltage 51 by the rectifier 52 into AC by the inverter 56 and controlling the converted AC voltage 59. DC voltage detector 5
A DC voltage detector 4 detects the DC voltage 55 output from the rectifier 52 and supplies the detected voltage signal Vout to the inverter controller 57. Thus, the inverter 56 is controlled in the event of an abnormality such as when the voltage of the AC input drops or rises, and the inverter 56 is protected from the input voltage abnormality.

[0004]

However, in the above-mentioned prior art, the detected voltage and the output detection signal are non-insulated in the first DC voltage detector. For example, in the power conversion device 50 of FIG. The electric potential of the controller 57 becomes the same as the electric potential of the rectifier 52, and a high voltage such as several hundreds of volts is applied to the above-mentioned inverter controller 57 which operates at a low voltage, and the inverter controller has a high withstand voltage such as several hundreds of volts. Semiconductors are needed. Further, the second detector has a large number of parts to be realized, and the photocoupler and V
There is a problem that expensive parts such as the / F and F / V converters are required.

[0005]

SUMMARY OF THE INVENTION A first invention is an insulating transformer having one primary winding and two secondary windings for insulating a detected voltage and a detected output voltage signal, and a primary winding of the insulating transformer. A first shunt resistor on the wire side, a diode bridge for alternately switching the current of the primary winding of the isolation transformer, and a second bridge for alternately switching on and off the current of the two secondary windings of the isolation transformer. Two switches, an oscillator that drives the two switches, a regulated DC voltage source that keeps the secondary voltage of the isolation transformer constant, and an output current output at the outputs of the two switches. Is a DC voltage detector including a second shunt resistor for converting into

The DC current on the primary side of the insulating transformer is switched by alternately switching the two switches to alternately switch the two winding currents on the secondary side of the insulating transformer. The current in the primary winding of the isolation transformer is switched, and the current reduced by the first shunt resistor due to the detected voltage flows in the primary side of the isolation transformer in the positive polarity and the negative polarity. By alternately switching the primary side current of the isolation transformer, magnetic saturation of the isolation transformer is blocked and current is transmitted from the primary side to the secondary side. At this time, the stabilized DC voltage source keeps the exciting current of the insulating transformer constant, thereby reducing the current transmission error due to the exciting current of the insulating transformer. The current transmitted to the secondary side of the isolation transformer is converted into a voltage by the second shunt resistor, and the DC output is taken out.

A second invention is an insulation transformer having two primary windings and two secondary windings for insulating a voltage to be detected from a detected output voltage signal, and a first winding on the primary winding side of the insulation transformer.
Shunt resistor, a diode that alternately switches the currents of the two primary windings of the isolation transformer, and two switches that alternately turn on and off the currents of the two secondary windings of the isolation transformer. , An oscillator that drives the two switches, a stabilized DC voltage source that keeps the secondary side voltage of the isolation transformer constant, and the output of the two switches that converts the output side current into an output detection voltage signal 2 is a DC voltage detector including a second shunt resistor.

The two switches are alternately switched to alternately switch the two winding currents on the secondary side of the insulating transformer, and the direct current on the primary side of the insulating transformer is switched to the two windings. The current of the primary winding of the isolation transformer is alternately switched to two windings, and the current that is reduced by the first shunt resistor due to the detected voltage flows alternately to the primary winding of the isolation transformer by the diode. .
By alternately switching the primary side current of the insulating transformer to two windings, magnetic saturation of the insulating transformer is blocked and current is transmitted from the primary side to the secondary side. At this time, the stabilized DC voltage source keeps the exciting current of the insulating transformer constant, thereby reducing the current transmission error due to the exciting current of the insulating transformer. The current transmitted to the secondary side of the isolation transformer is converted into a voltage by the second shunt resistor, and the DC output is taken out.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention is shown in FIG.
This will be described below. The present invention relates to a shunt resistor 2 and a shunt resistor 1 for dividing a DC voltage 1 shown in FIG.
5, an insulating transformer 7 for electrically insulating the shunt resistor 2 and the shunt resistor 15, and two secondary windings 7b and 7c of the insulating transformer 7 on the secondary side electric path of the insulating transformer 7. The switch 11 and the switch 1 that perform an on / off operation in order to alternately flow the current I2 flowing through the switch 18.
2, an oscillator 13 for alternately turning on / off the switch 11 and the switch 12, and an operation of the switch 11 and the switch 12 to alternately switch the current I1 flowing in the primary side electric path 17 of the insulating transformer 7. The diode bridge 18, the DC voltage source 10 and the transistor 14 which are means for stabilizing the applied voltage on the secondary side of the isolation transformer, and the secondary side DC voltage source 9 of the isolation transformer 7. It is a feature.

In FIG. 1, a switch 11 and a switch 12 are alternately turned on and off by an oscillator 13. When the switch 11 is off and the switch 12 is on, the current I2 supplied from the DC voltage source 9 and flowing through the current reducing resistor 8
Flows through the secondary winding 7b of the insulating transformer 7 and then flows through the shunt resistor 15. On the other hand, when the switch 11 is on and the switch 12 is off, the current I2 supplied from the DC voltage source 9 and flowing through the current reducing resistor 8 flows through the secondary winding 7c of the insulating transformer 7 and the shunt resistor. Flow through 15. By turning on / off the switches 11 and 12, the voltage V72 of one secondary winding 7b of the insulating transformer 7 is switched to the voltage V73 of the other winding 7c. By switching the voltage applied to the secondary winding of the isolation transformer 7 from the windings 7b to 7c, the voltage V of the primary winding 7a of the isolation transformer 7 is changed.
71 is switched from the positive polarity to the negative polarity.

The voltage V7 of the primary winding 7a of the insulation transformer 7
When 1 is positive, the cathode of the diode 3 has a positive polarity and the anode of the diode 6 has a negative polarity, so that the diode 3 and the diode 6 do not conduct but the diode 4 and the diode 5 conduct. On the other hand, when the voltage V71 of the primary winding 7a of the insulating transformer 7 is negative, the cathode of the diode 4 has a positive polarity and the anode of the diode 5 has a negative polarity, so that the diode 4 and the diode 5 do not conduct and the diode 3 And the diode 6 becomes conductive. A current proportional to the DC input voltage Vin that is reduced by the shunt resistor 2 due to the switching of the diode flows to the primary winding 7a of the transformer 7, and the transformer 7 is not subjected to magnetic saturation, and the DC is supplied to the secondary windings 7b and 7c. A current proportional to the input voltage Vin flows. The secondary winding current of the transformer 7 that flows in proportion to the DC input voltage Vin is guided to the shunt resistor 15 by the switch 11 and the switch 12, and the shunt resistor 15
Is converted into a DC output voltage Vout and output as a voltage proportional to Vin.

The DC voltage source 10 has the purpose of keeping the voltages V72 and V73 of the secondary windings 7b and 7c of the transformer 7 constant and keeping the exciting current of the transformer 7 constant. By connecting the base of the PNP transistor 14 to the positive side of the shunt resistor 15, the voltage V of the secondary windings 7b and 7c of the transformer 7 due to the voltage fluctuation of the shunt resistor 15
72 and V73 are compensated. For example, when the voltage of the shunt resistor 15 becomes zero when the switch 11 is on,
The base current of the transistor 14 is maximized, the transistor 14 is fully conductive, and the collector-emitter voltage becomes zero if the semiconductor voltage drop is ignored.
In this state, the voltage V73 of the secondary winding 7c of the transformer 7 becomes equal to the voltage of the DC voltage source 10. On the other hand, switch 1
When 1 is on, the voltage of the shunt resistor 15 is
If it is 0V, the base current of the transistor 14 will decrease and the transistor 14 will be in an unsaturated state,
As for the voltage between the emitters, if the semiconductor voltage drop is ignored,
10V. In this state, the voltage V73 of the secondary winding 7c of the transformer 7 becomes equal to the voltage of the DC voltage source 10 similarly to the above. By making the exciting current constant, the current flowing through the transformer 7 becomes a value proportional to Vin, and the output voltage Vo
ut has a value proportional to the input voltage Vin. That is,
If the winding ratio of the transformer 7 is 1: 1, the output voltage Vout
Is a ratio of the resistance value of the shunt resistor 15 and the resistance value of the shunt resistor 2 and is proportional to the input voltage Vin.

Next, an embodiment of the second invention will be described with reference to FIG. The present invention includes a shunt resistor 2 and a shunt resistor 15 for dividing a DC voltage 1 shown in FIG.
An insulating transformer 77 for electrically insulating the shunt resistor 2 and the shunt resistor 15 and two secondary windings 77c and 77d of the insulating transformer 77 flow to the secondary side electric circuit 18 of the insulating transformer 77. A switch 11 and a switch 12 that perform an on / off operation to alternately flow the current I2, an oscillator 13 that alternately turns on and off the switch 11 and a switch 12, and the switch 11
And the switch 12 operate to alternately switch the current I1 flowing through the primary side electric path 17 of the insulation transformer 77, and the DC voltage of the means for stabilizing the applied voltage on the secondary side of the insulation transformer. The power source 10 and the transistor 14 and the secondary side DC voltage source 9 of the isolation transformer 77 are provided.

In FIG. 2, a switch 11 and a switch 12 are alternately turned on and off by an oscillator 13. When the switch 11 is off and the switch 12 is on, the current I2 supplied from the DC voltage source 9 and flowing through the current reducing resistor 8
Flows through the secondary winding 77c of the isolation transformer 77 and then flows through the shunt resistor 15. On the other hand, when the switch 11 is turned on and the switch 12 is turned off, the current I2 supplied from the DC voltage source 9 and flowing through the current reducing resistor 8 is the insulating transformer 77.
Flowing through the secondary winding 77d and flowing through the shunt resistor 15. By turning on / off the switches 11 and 12, the voltage V of one secondary winding 77c of the insulating transformer 77 is
The voltage is switched from 83 to the voltage V84 of the other winding 77d.
The voltage applied to the secondary winding of the isolation transformer 77 is applied to the winding 77.
Isolation transformer 7 by switching from c to 77d
The voltage of the primary winding 7 changes from positive polarity to negative polarity in the winding 77a. Further, the voltage of the winding 77b is switched from the negative polarity to the positive polarity.

When a positive voltage is applied to the primary winding 77a of the isolation transformer 77, the cathode of the diode 78 becomes positive and the cathode of the diode 79 becomes negative, so that the diode 78 does not conduct and the diode 78 does not conduct. 79 becomes conductive. On the other hand, when the voltage of the primary winding is applied to the primary winding 77b of the insulation transformer 77, the cathode of the diode 79 has a positive polarity and the cathode of the diode 78 has a negative polarity. Does not conduct, and the diode 78 conducts. A current proportional to the DC input voltage Vin reduced by the shunt resistor 2 due to the switching of the diode flows through the primary winding 77a or 77b of the transformer 7 and the secondary winding 77c, 77d without magnetic saturation of the transformer 77. A current that is proportional to the DC input voltage Vin flows through. DC input voltage Vin
The secondary winding current of the transformer 77 that flows in proportion to is guided to the shunt resistor 15 by the switch 11 and the switch 12, and the shunt resistor 15 causes the DC output voltage Vou.
It is converted into t and output as a voltage proportional to Vin.

Here, the DC voltage source 10 is the voltages V83 and V84 of the secondary windings 77c and 77d of the transformer 77, respectively.
Is kept constant and the exciting current of the transformer 77 is kept constant. By connecting the base of the PNP transistor 14 to the positive side of the shunt resistor 15, the shunt resistor 1
Secondary windings 77c, 7 of the transformer 77 due to the voltage fluctuation of 5
The voltage V83 and V84 of 7d are compensated. For example, when the switch 11 is on and the voltage of the shunt resistor 15 becomes zero, the base current of the transistor 14 becomes maximum, the transistor 14 becomes fully conductive, and the collector-emitter voltage becomes a semiconductor voltage drop. Is ignored, it becomes zero. In this state, the secondary winding 7 of the transformer 77
The voltage V83 of 7d becomes equal to the voltage of the DC voltage source 10. On the other hand, when the switch 11 is on, the shunt resistor 1
If the voltage of 5 is, for example, 10 V, the base current of the transistor 14 decreases, the transistor 14 becomes unsaturated, and the collector-emitter voltage becomes 10 V if the semiconductor voltage drop is ignored. In this state, similarly to the above, the voltage V84 of the secondary winding 77d of the transformer 77 becomes equal to the voltage of the DC voltage source 10. By making the exciting current constant, the current flowing through the transformer 77 becomes a value proportional to Vin, and the output voltage Vout becomes a value proportional to the input voltage Vin. That is, the winding ratio of the transformer 77 is 1
In the case of the pair 1, the output voltage Vout is the ratio of the resistance value of the shunt resistor 15 and the resistance value of the shunt resistor 2 to the input voltage Vi.
n.

[0017]

EXAMPLE FIG. 3 shows an example of the present invention. The embodiment of FIG. 3 is different from the embodiment of the first invention of FIG.
0 is changed to two series diodes 20, and switch 11
And 12 are changed to field effect transistors.
When two series diodes 20 are used as the DC voltage source 10, a voltage of about 1.4V is generated between the terminals of the two series diodes 20 while the transistor 14 is in the ON state.
Furthermore, 0.7V between the emitter and base of transistor 4
And a voltage of about 0.7V is generated by using a field effect transistor for the switch 11 or the switch 12. In this state, the secondary winding 7b or 7c of the transformer 7
A stable DC voltage of 2.8 V is applied to. In other operations, if the winding ratio of the transformer 7 is 1: 1, the output voltage Vout is the ratio of the resistance value of the shunt resistor 15 and the resistance value of the shunt resistor 2 as in the embodiment of FIG.
Is proportional to By using field effect transistors for the switches 11 and 12, the switches 11 and 12 can be converted into several tens.
It can operate at a high frequency of 0 kHz, and the transformer 7 can be made compact.

[0018]

As described above, the switch 1 is provided on the secondary side of the transformer 7 having the diode bridge 18 for switching the DC voltage to the primary side and one primary winding and two secondary windings.
By providing 1 and 12 and switching by the oscillator 13 at a high frequency of about 100 kHz, the size of the insulation transformer can be reduced, and a simple structure with a very small number of parts and an inexpensive insulation type DC voltage detection circuit can be formed. .

[Brief description of drawings]

FIG. 1 is a circuit of an embodiment of the first invention.

FIG. 2 is a circuit according to an embodiment of the second invention.

FIG. 3 is a circuit diagram of an embodiment of the first invention.

FIG. 4 is a basic circuit of a first example of the prior art.

FIG. 5 is a basic circuit of a first example of the prior art.

FIG. 6 shows an application of an embodiment of the present invention.

[Explanation of symbols]

 1 Detected DC voltage Vin 2, 15 Shunt resistor 3, 4, 5, 6, 78, 79 Diode 7, 77 Insulation transformer 7a Primary winding 7b, 7c Secondary winding of isolation transformer 7 Reduction 8 Current resistor 9 DC voltage source 10 Stabilized DC voltage source 11, 12 Switch 13 Oscillator 14 Transistor 17, 19 Electric circuit 18 Diode bridge 20 Two series diodes 21, 22 Field effect transistor 23 Detection output signal 50 Power converter 51 Inverter 77a, 77b Primary winding of insulation transformer 77 77c, 77d Secondary winding of insulation transformer 77

Claims (2)

[Claims] 1. An insulating transformer having one primary winding and two secondary windings for insulating a detected voltage signal from a detected output voltage signal, and a first shunt resistor on the primary winding side of the insulating transformer. Driving the two switches, and a diode bridge that alternately switches the current of the primary winding of the isolation transformer, two switches that alternately turn on and off the currents of the two secondary windings of the isolation transformer, and the two switches. Oscillator, a stabilized DC voltage source that keeps the secondary voltage of the isolation transformer constant, and a second shunt resistor that is provided at the outputs of the two switches and that converts the output current to an output detection voltage signal. DC voltage detector consisting of. 2. An insulating transformer having two primary windings and two secondary windings for insulating the detected voltage and the detected output voltage signal, and a first shunt resistor on the primary winding side of the insulating transformer. A diode that alternately switches the currents of the two primary windings of the isolation transformer, two switches that alternately turn on and off the currents of the two secondary windings of the isolation transformer, and the two switches And a stabilized DC voltage source that keeps the secondary voltage of the isolation transformer constant, and a second shunt that is provided at the outputs of the two switches and that converts the output current to an output detection voltage signal. DC voltage detector consisting of a resistor.