JP2006345624A - Undervoltage/overvoltage protection circuit for control power circuits - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an undervoltage/overvoltage protection circuit for control power circuits that is capable of detecting any anomaly in supplied power supply voltage even when a control power circuit is not started and makes it possible to reduce power consumed for an anomaly detection circuit and the size of the anomaly detection circuit. <P>SOLUTION: A control power circuit 1 transforms received alternating-current voltage into a direct current, and outputs it as control power supply. A transformer 25 for standby energy reduction has a sub-winding 28 in addition to a primary winding 26 and a secondary winding 27. The voltage of inputted power supply is determined based on the voltage of the sub-winding 28. When the voltage of the power supply is out of a range of normal value, an anomaly signal is generated. The input voltage of a transformer 4 for main power supply is turned off according to this anomaly signal. Alternatively, the range of inputted power supply voltage is determined based on the voltage of the sub-winding 28. The tap of the transformer 4 for main power supply is changed based on the result of the determination and tap change data stored in storage means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a protection circuit for a control power supply circuit, and in particular, uses a standby power supply transformer to detect a shortage and overvoltage of a voltage input to a primary side, and control to prevent failure and destruction of a device. In addition, the present invention relates to an under / overvoltage protection circuit capable of saving power.

The power supply circuit that supplies control voltage to electronic control equipment, etc. is equipped with a protection circuit to prevent the equipment from failing or being destroyed due to insufficient input voltage or excessive voltage. There is something. One related to this prior art is disclosed in Japanese Utility Model Laid-Open No. 3-3134 (Patent Document 1). The protection monitoring circuit relating to the switching power supply device described in Japanese Utility Model Publication No. H3-33-3134 (Patent Document 1) detects that the voltage induced in the transformer of the switching power supply device deviates from the low-grade range and supplies it. Assuming that the power supply voltage to be abnormal is abnormal, the operation of the switching power supply device is stopped or the abnormality is notified. As a result, when an abnormality is detected in the switching control circuit after startup, the operation is immediately stopped, and problems such as defective control operation and destruction of circuit elements can be prevented.
Japanese Utility Model Publication No.3-3134

  However, the above prior art has a problem that an abnormality in the power supply voltage cannot be detected unless the switching power supply device is activated. Accordingly, if an abnormal power supply voltage is input after the switching power supply device is activated, the switching power supply device operates abnormally for a short time, which may cause destruction of circuit elements. In the above prior art, a sub-winding is applied to the main power supply transformer of the switching power supply device, and an abnormality of the supplied power voltage is detected by a voltage induced in the sub-winding. Therefore, it is necessary to operate the main power supply transformer, and there is a problem that a large amount of power is consumed for the abnormality detection circuit. In addition, the sub-winding is wound around the main power supply transformer, and there is a problem that the transformer becomes large.

  In view of the above-described conventional problems, the object of the present invention is to detect an abnormality in the power supply voltage supplied even when the control power supply circuit is not activated, to reduce power consumed for the abnormality detection circuit, and to detect an abnormality. An object of the present invention is to provide a shortage / overvoltage protection circuit for a control power supply circuit that can reduce the circuit size.

The gist of the invention according to claim 1 of the present invention is that, in a control power supply circuit that converts a received AC power supply voltage into a direct current and outputs it as a control power supply, in addition to the primary winding and the secondary winding, A standby power reduction transformer provided, and a shortage / overvoltage protection means for determining a voltage of an input power supply based on the voltage of the auxiliary winding and protecting an undervoltage and an overvoltage. It exists in the control power circuit.
According to a second aspect of the present invention, there is provided a storage means for storing a normal value range of a predetermined power supply voltage, wherein the shortage / overvoltage protection means is based on the voltage of the sub winding. The control power supply circuit according to claim 1, wherein the control power supply circuit is protected by determining that the voltage of the power supply being used is outside the range of the normal value range.
According to a third aspect of the present invention, there is provided a main power supply transformer connected to the power supply, wherein the shortage / overvoltage protection means includes a power supply voltage outside the normal value range. The control power supply circuit according to claim 1 or 2, wherein an input voltage of the main power supply transformer is turned off by an abnormal signal generated at a certain time.
According to a fourth aspect of the present invention, there is provided a main power supply switching power supply connected to the power supply, wherein the shortage / overvoltage protection means includes a power supply voltage outside the normal value range. The control power supply circuit according to claim 1 or 2, wherein the input voltage of the switching power supply for main power supply is turned off by an abnormal signal generated when
The gist of the invention according to claim 5 of the present invention is that the under / overvoltage protection means causes the light emitting diode to blink by a blinking signal generated when the voltage of the power source is outside the normal value range. The control power supply circuit according to claim 3 or 4, further comprising means for notifying abnormality.
A gist of the invention according to claim 6 of the present invention is that a primary power supply transformer having a tap on a primary winding connected to a power source and switching data for switching the tap according to a range of a power supply voltage. Is stored in advance, the shortage / overvoltage protection means determines the range of the input power supply voltage based on the voltage of the auxiliary winding, and the determination result and the storage means are stored in the storage means The control power supply circuit according to claim 1, wherein the tap is switched based on switching data.

According to the present invention, it is possible to detect an abnormality in the power supply voltage supplied even when the control power supply circuit is not activated.
In addition, there is an effect that power consumed for the abnormality detection circuit can be reduced.
Further, there is an effect that the abnormality detection circuit can be reduced in size.

Next, the best mode for carrying out the present invention will be specifically described with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram for explaining an under / overvoltage protection circuit according to a first embodiment of the present invention.

  In FIG. 1, reference numeral 1 denotes a control power supply circuit including an under / overvoltage protection circuit. A plug 2 is inserted into an AC power outlet and receives power. Reference numeral 3 denotes an input ON / OFF element that turns on and off the input power from the plug 2. A main power supply transformer 4 supplies control power. The main power supply transformer 4 includes a primary winding 23 and a secondary winding 24. A primary voltage input from the input ON / OFF element 3 is applied to the primary winding 23. Reference numeral 5 denotes a diode bridge, which rectifies the secondary voltage from the secondary winding 24 and converts it into a DC voltage. A DC smoothing capacitor 6 smoothes a DC voltage including pulsation from the diode bridge 5. The DC voltage smoothed by the DC smoothing capacitor 6 is supplied to each control circuit as a control main power source of the control device.

  Reference numeral 25 denotes a standby power reduction transformer provided for the purpose of reducing standby power. The standby power reduction transformer 25 includes a primary winding 26, a secondary winding 27, and a sub-winding 28. A diode bridge 7 rectifies the secondary voltage from the secondary winding 27 and converts it into a DC voltage. A DC smoothing capacitor 8 smoothes a DC voltage including pulsation from the diode bridge 7.

  Reference numeral 9 denotes a system control element constant voltage element (such as a three-terminal regulator) that supplies control power to the system control element 10. The DC voltage smoothed by the DC smoothing capacitor 8 is input to the system control element constant voltage element 9, and the system control element constant voltage element 9 supplies a predetermined stable DC voltage to the system control element 10. The system control element 10 is a control unit including a microcomputer (microcontroller).

  A diode 11 rectifies the voltage from the sub-winding 28 and outputs the rectified voltage to the DC smoothing capacitor 12. The DC smoothing capacitor 12 smoothes the voltage from the diode 11. Reference numerals 13 and 14 denote voltage dividing resistors connected between the DC smoothing capacitors 12. A voltage obtained by dividing the voltage across the DC smoothing capacitor 12 is taken out from the connection point of these voltage dividing resistors, and the system control element 10. Is input.

  15 is a resistor, 16 is a light emitting diode (LED), and 17 is a transistor. One end of the resistor 15 is connected to the output terminal of the system control element constant voltage element 9, and the other end is connected to the anode of the light emitting diode 16. The cathode of the light emitting diode 16 is connected to the collector of the transistor 17, and the emitter of the transistor 17 is connected to the ground line of the system control element constant voltage element 9. A blinking signal output from the system control element 10 when the input power supply is abnormal is input to the base of the transistor 17. The power supply abnormality signal is a periodic pulse signal so that the light emitting diode 16 blinks and emits light.

  The input ON / OFF element 3 includes switch elements 18 and 19 and a control coil 20 that controls opening and closing of the switch. A diode 21 suppresses a surge voltage of the control coil 20 that accompanies opening and closing of the switch elements 18 and 19. Reference numeral 22 denotes a transistor. One end of the control coil 20 is connected to the collector of the transistor 22, and the emitter of the transistor 22 is connected to the ground line of the system control element constant voltage element 9. The other end of the control coil 20 is connected to the output terminal of the system control element constant voltage element 9. A power supply abnormality display signal output when the input power supply is abnormal is input from the system control element 10 to the base of the transistor 22.

Next, the operation of the control power supply circuit 1 configured as described above will be described.
The power supply voltage input from the plug 2 is irrespective of whether or not the voltage is supplied to the main power supply transformer 4 (regardless of whether the switch elements 18 and 19 of the input ON / OFF element 3 are ON or OFF). The standby power reduction transformer 25 is applied. Therefore, the system control element 10 operates even during standby, and inputs a DC voltage obtained by rectifying and dividing the voltage from the sub-winding 28 to monitor an abnormality in the power supply voltage.

  The system control element 10 stores a predetermined normal value range (set voltage range) of the power supply voltage. If the voltage from the sub-winding 28 is within the set voltage range, the system control element 10 sends a signal for turning on (ON) the switch elements 18 and 19 provided at the input of the main power supply transformer 4 to the transistor 22. Output to the base terminal. As a result, the transistor 22 becomes conductive, the output voltage of the system control element constant voltage element 9 is applied to the control coil 20, and the switch elements 18 and 19 become conductive (ON).

  If the voltage from the sub-winding 28 is outside the set voltage range, the system control element 10 outputs a signal for turning off the switch elements 18 and 19 provided in the input section of the main power supply transformer 4 to the transistor. It outputs to 22 base terminals. As a result, the transistor 22 is turned OFF, no voltage is applied to the control coil 20, and the switch elements 18 and 19 are turned off (OFF). Further, a blinking signal indicating a power supply abnormality is input to the base terminal of the transistor 17. As a result, the light emitting diode 16 can blink to notify the abnormality of the power supply voltage.

  As described above, in the present embodiment, the input power supply voltage can be monitored by the auxiliary winding 28 of the standby power reduction transformer 25, and the voltage is supplied to the main power supply transformer 4 within the set voltage range. Thus, if the voltage is out of the set voltage range, the voltage can be prevented from being supplied to the main power supply transformer 4.

  Therefore, according to the present embodiment, it is possible to detect an abnormality in the power supply voltage supplied by the standby power reduction transformer 25 even when the control power supply circuit is not activated, and the auxiliary winding of the standby power reduction transformer 25 is used. Therefore, the power consumed for the abnormality detection circuit can be reduced, and since the auxiliary winding of the standby power reduction transformer 25 is used, the abnormality detection circuit transformer can be miniaturized.

(Second Embodiment)
FIG. 2 is a diagram illustrating an under / overvoltage protection circuit according to the second embodiment of the present invention.

  In FIG. 2, reference numeral 45 denotes a control power supply circuit having an under / overvoltage protection circuit. A plug 2 is inserted into an AC power outlet and receives power. Reference numeral 3 denotes an input ON / OFF element that turns on and off the input power from the plug 2.

  Reference numeral 30 denotes a choke coil. A diode bridge 31 rectifies the voltage from the choke coil 30 and converts it into a DC voltage. Reference numeral 32 denotes a DC smoothing capacitor that smoothes a DC voltage including pulsation from the diode bridge 31. The DC voltage smoothed by the DC smoothing capacitor 32 is supplied to the switching transformer 36. The switching transformer 36 includes a primary winding 37, a secondary winding 38 and a sub winding 39. Reference numeral 33 denotes a starting resistor, 34 denotes a switch element driving circuit, 35 denotes a transistor, and 40 denotes a diode. 41 is a diode, and 42 is a DC smoothing capacitor. The elements 30 to 42 constitute a main power supply switching power supply circuit. The output of the main power supply switching power supply circuit is supplied to each control circuit as a control main power supply for the control device.

  The elements 7 to 22 and 25 to 28 for detecting the abnormality of the power supply voltage and performing the protection operation are the same as those in the first embodiment shown in FIG. Detailed description is omitted.

  Comparing the present embodiment with the first embodiment, the present embodiment is the configuration of the main power supply unit shown in FIG. 1 (part composed of elements 4-6, 23, and 24). Is replaced with a switching power supply (part constituted by elements 30 to 42), and thus the protection operation is the same as that of the first embodiment. Also in the present embodiment, the input power supply voltage can be monitored by the sub-winding 28 of the standby power reduction transformer 25, and the main power is supplied within the set voltage range. If so, the main power can be prevented from being supplied.

  Therefore, according to the present embodiment, it is possible to detect an abnormality in the power supply voltage supplied by the standby power reduction transformer 25 even when the control power supply circuit is not activated, and the auxiliary winding of the standby power reduction transformer 25 is used. Therefore, the power consumed for the abnormality detection circuit can be reduced, and since the auxiliary winding of the standby power reduction transformer 25 is used, the abnormality detection circuit transformer can be miniaturized.

(Third embodiment)
FIG. 3 is a diagram for explaining an under / overvoltage protection circuit according to a third embodiment of the present invention.

  In FIG. 3, reference numeral 46 denotes a control power supply circuit provided with an under / overvoltage protection circuit. A plug 2 is inserted into an AC power outlet and receives power. An input switching element 51 is selectively switched according to the voltage level of the input power supply from the plug 2. 52 is a main power supply transformer with an input tap for supplying control power. The main power supply transformer 52 with an input tap includes a primary winding 55 and a secondary winding 56. The primary winding 55 is selected and connected depending on the magnitude of the voltage, but is provided with taps 58 to 61. The input switching element 51 includes a switch 57 having contacts 62 to 66, the contact 62 is connected to the tap 58, the contact 63 is connected to the tap 59, the contact 64 is connected to the tap 60, and the contact 65 is connected to the tap 61. It is connected. The contact 66 is not connected to the main power supply transformer 52 with an input tap (used as a contact for main power supply OFF). FIG. 3 shows an example in which the tap 58 applied to the primary power supply transformer 52 with input tap is 100V, the tap 59 is 120V, the tap 60 is 220V, and the tap 61 is 240V.

  A diode bridge 53 rectifies the secondary voltage from the secondary winding 56 and converts it into a DC voltage. Reference numeral 54 denotes a DC smoothing capacitor that smoothes a DC voltage including pulsation from the diode bridge 53. The DC voltage smoothed by the DC smoothing capacitor 54 is supplied to each control circuit as a control main power source of the control device.

  Reference numeral 25 denotes a standby power reduction transformer provided for the purpose of reducing standby power. The standby power reduction transformer 25 includes a primary winding 26, a secondary winding 27, and a sub-winding 28. A diode bridge 7 rectifies the secondary voltage from the secondary winding 27 and converts it into a DC voltage. A DC smoothing capacitor 8 smoothes a DC voltage including pulsation from the diode bridge 7.

  Reference numeral 9 denotes a system control element constant voltage element (such as a three-terminal regulator) that supplies control power to the system control element 50. The DC voltage smoothed by the DC smoothing capacitor 8 is input to the system control element constant voltage element 9, and the system control element constant voltage element 9 supplies a predetermined stable DC voltage to the system control element 50. The system control element 50 is a control unit including a microcomputer (microcontroller).

  Reference numeral 11 denotes a diode, which rectifies the voltage from the auxiliary winding 27 and outputs it to the DC smoothing capacitor 12. The DC smoothing capacitor 12 smoothes the voltage from the diode 11. Reference numerals 13 and 14 denote voltage dividing resistors connected between the DC smoothing capacitors 12. The voltage obtained by dividing the voltage across the DC smoothing capacitor 12 is taken out from the connection point of these voltage dividing resistors, and the system control element 50 Is input. A switching signal corresponding to the voltage value of the input power supply is output from the system control element 50 to the input switching element 51.

Next, the operation of the control power supply circuit 1 configured as described above will be described.
The power supply voltage input from the plug 2 is applied to the standby power reduction transformer 25 regardless of whether the voltage is supplied to the main power supply transformer 52 with an input tap. Therefore, the system control element 50 is operating even during standby, and inputs a DC voltage obtained by rectifying and dividing the voltage from the auxiliary winding 28 and monitoring the magnitude of the power supply voltage.

  In the system control element 50, switching data for switching the contact of the input switching element 51 according to the range of the power supply voltage is stored in advance. For example, 3-bit data is stored according to the range of the power supply voltage. As an example, if the voltage value of the input power source is 90V to 110V, the switching data is set to 001 and the contact 62 connected to the 100V tap 58 is switched. If 110V to 130V, the switching data is set to 010 and the 120V tap 59 is switched. If it is 210V to 230V, the switching data is 011 and the switching data is switched to the contact 64 connected to the 220V tap 60. If it is 230V to 250V, the switching data is 100 and the 240V is connected to the 240V tap 59. Switch to the contact 65 made. When the power supply voltage is out of the above range, the switching data is set to 101 and the contact 66 is switched to turn off the primary voltage of the main power supply transformer 52 with the input tap.

  As described above, in the present embodiment, the value of the input power supply voltage is monitored by the sub-winding 28 of the standby power reduction transformer 25, and one of the main power supply transformers 52 with an input tap is selected according to the value of the power supply voltage. The next winding tap can be switched.

  Therefore, according to the present embodiment, it is possible to detect an abnormality in the power supply voltage supplied by the standby power reduction transformer 25 even when the control power supply circuit is not activated, and the auxiliary winding of the standby power reduction transformer 25 is used. Therefore, the power consumed for the abnormality detection circuit can be reduced, and since the auxiliary winding of the standby power reduction transformer 25 is used, the abnormality detection circuit transformer can be miniaturized. Furthermore, according to the present embodiment, the value of the power supply voltage can be monitored, and the applied voltage of the main power supply transformer 52 with the input tap can be set to an appropriate value.

  As described above, the present invention has been specifically described with reference to the first to third embodiments. However, the present invention is not limited to the above-described embodiments, and can be changed and implemented without changing the gist of the present invention. Needless to say.

  The present invention can be widely used for a protection circuit that protects a device from an abnormal voltage of an input power supply voltage of a control power supply circuit.

It is a figure explaining the under / overvoltage protection circuit by the 1st Embodiment of this invention. It is a figure explaining the under / overvoltage protection circuit by the 2nd Embodiment of this invention. It is a figure explaining the under / overvoltage protection circuit by the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 45, 46 ... Control power supply circuit 2 ... Plug 3 ... Input ON / OFF element 4 ... Main power supply transformer 5, 7, 31, 53 ... Diode bridge 6, 8, 12 32, 42, 54 ... DC smoothing capacitor 9 ... System control element constant voltage element 10, 50 ... System control element 11, 21, 40, 41 ... Diode 13, 14 ... min Resistance 15 ... Resistance 33 ... Starting resistance 16 ... Light emitting diode (LED)
17, 22, 35 ... transistors 18, 19 ... switch element 20 ... control coil 23 ... primary winding 24 ... secondary winding 25 ... stand-by power reduction transformer 26 ... Primary winding 27 ... Secondary winding 28 ... Sub winding 30 ... Choke coil 34 ... Switch element drive circuit 36 ... Switching transformer 37 ... Primary winding 38 ... Secondary winding 39 ... sub winding 51 ... input switching element 52 ... main power supply transformer 55 with input tap ... primary winding 56 ... secondary winding 57 ... switch 58 ... 61 ... Taps 62 to 66 ... Contacts

Claims (6)

In the control power supply circuit that converts the received AC power supply voltage to DC and outputs it as a control power supply,
Standby power reduction transformer with secondary winding in addition to primary winding and secondary winding,
A control power supply circuit comprising a shortage / overvoltage protection means for protecting a shortage voltage and an overvoltage by determining a voltage of an input power supply based on the voltage of the sub winding. Comprising storage means for storing a normal value range of a predetermined power supply voltage;
2. The under / overvoltage protection means protects by determining that an input power supply voltage is outside the normal value range based on the voltage of the sub-winding. The control power supply circuit described. A main power supply transformer connected to the power source;
The under / overvoltage protection means turns off the input voltage of the main power supply transformer by an abnormal signal generated when the voltage of the power source is outside the range of the normal value range. The control power supply circuit according to claim 1 or 2. A mains power switching power supply connected to the power supply,
The under / overvoltage protection means turns off the input voltage of the main power supply switching power supply by an abnormal signal generated when the power supply voltage is outside the normal value range. The control power supply circuit according to claim 1 or 2.   The under / overvoltage protection means includes means for informing an abnormality by blinking a light emitting diode by a blink signal generated when the voltage of the power source is outside the range of the normal value range. The control power supply circuit according to claim 3 or 4. A primary power supply transformer with a tap on the primary winding connected to the power supply;
Comprising storage means for storing switching data for switching the tap according to the range of the power supply voltage;
The under / overvoltage protection means determines a range of the input power supply voltage based on the voltage of the sub winding, and switches the tap based on the result of the determination and switching data stored in the storage means. The control power supply circuit according to claim 1.

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