JP2010172055A - Gas detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas detector capable of obtaining a stable operation by electric power supplied using a PoE system.
A gas detector having a pump for introducing a gas to be measured, comprising an insulated power circuit that transforms and outputs an input voltage supplied from a power over Ethernet (registered trademark) power supply. I will. The power supply circuit applies the supplied input voltage to the primary winding of the isolation transformer by controlling the switching element on / off, rectifies and outputs the voltage generated in the secondary winding by the rectifier element, and outputs the isolation transformer. The output from the secondary winding can be detected by a photocoupler, and the ratio of the ON time to the OFF time of the switching element can be controlled based on the signal from the photocoupler.
[Selection] Figure 1

Description

  The present invention relates to a gas detector driven by power supplied via a Power over Ethernet system.

In a terminal such as an IP phone, a wireless LAN access point, a personal computer, and a web camera connected to a network, two types of wiring, a communication line and a power line, are usually required. Power is supplied to a terminal using an Ethernet (registered trademark) cable used for transmission.
In the IEEE 802.3af standard, which regulates power supply via an Ethernet (registered trademark) cable, a power over including sending power from a power source device to a power source device (Powered Device). An Ethernet (registered trademark) system has been defined, and various devices using such a system have been proposed (see, for example, Patent Document 1).

JP 2008-294951 A

In such a system, the power supplied from the power supply side device to the power receiving side device is limited to a maximum of 12.95 W and the input voltage is limited to 36 to 57 V. Therefore, in the power receiving side device, a more efficient power supply circuit is provided. It is required to configure.
As the power supply circuit in the power receiving side device, for example, a recommended circuit that outputs a voltage of about 3.3V or 5V is introduced by each device manufacturer.

  Thus, when the Power over Ethernet (registered trademark) system is applied to a gas detector having a relatively large power consumption device such as a pump for introducing a test gas or a pyrolyzer, for example, In order to drive a gas detector including these devices, for example, a voltage of DC 24 V level is required.

  The present invention has been made based on the above circumstances, and provides a gas detector capable of obtaining stable operation by power supplied using a power over Ethernet (registered trademark) system. The purpose is to provide.

The gas detector of the present invention comprises a pump for introducing a test gas,
An insulation type power supply circuit that transforms and outputs an input voltage supplied from a Power over Ethernet (registered trademark) power supply is provided.

  In the gas detector according to the present invention, the power supply circuit applies the supplied input voltage to the primary winding of the insulation transformer by controlling on / off of the switching element, and the voltage generated in the secondary winding is the rectifying element. The output from the secondary winding of the isolation transformer is detected by the photocoupler and the ratio between the on time and the off time of the switching element is controlled based on the signal from the photocoupler. Can be configured.

  Furthermore, in the gas detector of the present invention, the number of turns of the insulation transformer is set so that the voltage and power necessary for the secondary winding of the insulation transformer are obtained, and the number of turns of the insulation transformer is set. Accordingly, it is preferable that the specification of the feedback resistance value connected to the secondary winding of the switching element, the rectifying element, and the insulating transformer is selected.

Furthermore, in the gas detector of the present invention, the switching element is composed of a MOSFET having a rating of 250 V · 7 A or more,
Switching noise reduction circuit comprising a capacitor and a resistor connected between one end of the primary winding of the isolation transformer and an intermediate connection point between the other end of the primary winding of the isolation transformer and the drain of the MOSFET It is preferable that it is set as the structure which has these.

  According to the present invention, it is possible to secure driving power for a pump with relatively large power consumption, and to prevent adverse effects due to a failure or the like between the gas detector on the power receiving side and the power supply side device (power supply). A gas detector that complies with the Power over Ethernet standard without impact is provided.

  When setting the number of turns of the insulation transformer so that the voltage and power required for the secondary winding of the insulation transformer can be obtained, specifications of the feedback resistance value connected to the secondary winding of the switching element, rectifier element, and insulation transformer Is selected according to the number of turns of the insulation transformer, so that the efficiency of the power supply circuit can be increased and the occurrence of problems such as output fluctuations on the secondary side of the insulation transformer can be reliably prevented. And stable output can be obtained.

  Furthermore, when a MOSFET with a relatively large rated voltage and rated current is used as a switching element as one of the circuit components to obtain the voltage and power required for the secondary winding of the isolation transformer Even so, switching noise can be reduced, and stable operation can be reliably obtained.

It is a circuit diagram which shows the structure of the power supply circuit in the gas detector of this invention.

  The gas detector of the present invention is driven by electric power supplied via Power over Ethernet (registered trademark) (hereinafter referred to as “PoE”), and includes a pump for introducing a test gas, Alternatively, a device having a large power consumption such as a pyrolyzer is provided. Here, the pump can be exemplified by a diaphragm type having an electromagnetic drive mechanism, for example.

FIG. 1 is a circuit diagram showing a configuration of a power supply circuit in the gas detector of the present invention.
In FIG. 1, reference numerals 10 and 11 denote diode bridges in which four diodes are connected in a bridge shape, and the power supply side of the diode bridge 10 is transformers 12 and 13 connected to signal pairs 15 and 16 used for signal transmission, respectively. The power supply side of the diode bridge 11 is connected to a spare pair (power supply) 18 that is not used for signal transmission. Further, the diode bridges 10 and 11 The output side is connected in common, and an output voltage control circuit 20 including a circuit (for example, a classification circuit) necessary for receiving power supply via PoE is connected. With such a configuration, the power of the same polarity is always supplied to the output voltage control circuit 20 regardless of which of the signal pair 15 and 16 and the spare pair 18 is supplied with power or the polarity of the supplied power is changed. Can be supplied.

  The output voltage control circuit 20 applies the input voltage supplied from the PoE power supply via the diode bridges 10 and 11 to the primary winding T1 of the isolation transformer 21 by turning on and off the switching elements, and applies the secondary winding T2 to the primary winding T1. Is rectified by a rectifying diode 23 and output, and the output from the secondary winding T2 of the insulating transformer 21 is detected by the photocoupler 30. The insulating transformer 21 and the photocoupler 30 An insulating part that insulates the supply side device and the gas detector as the power receiving side device is configured.

The switching element is composed of, for example, a MOSFET 22 and is turned on when a voltage having a magnitude controlled by the control IC 25 is applied between the gate G and the source S.
In the MOSFET 22, the ratio (duty ratio) between the on time and the off time is controlled based on the signal from the photocoupler 30.
When the control conditions of the MOSFET 22 are shown, for example, the switching frequency is 300 kHz.

The insulation transformer 21 transforms the input voltage supplied to the power supply circuit, for example, 36 to 57V, and the MOSFET 22 is turned on and off so that a voltage necessary for driving the gas detector including the pump, for example, about 24V can be obtained. The winding of the insulating transformer 21 is set in relation to the ratio.
The number of turns of the primary winding T1 and the secondary winding T2 of the insulating transformer 21 is, for example, the same (turn ratio is 1: 1).

  In this output voltage control circuit 20, a capacitor is connected between one end of the primary winding T1 of the insulating transformer 21 and an intermediate connection point between the drain D of the MOSFET 22 and the other end of the primary winding T1 of the insulating transformer 21. A switching noise reduction circuit 35 constituted by C1 and a resistor R1 is connected.

  Thus, in the above power supply circuit, in order to obtain a voltage and power of a necessary magnitude on the secondary side of the insulation transformer 21, not only the number of turns of the insulation transformer 21 is adjusted but also the high efficiency of the power supply circuit. From the standpoint of optimization and thermal countermeasures, MOSFETs, rectifying diodes 23, and feedback resistance values R2 and R3 connected to the secondary winding T2 of the insulating transformer 21 are selected to have appropriate specifications.

  Selection of the specifications of the MOSFET 22, the rectifying diode 23, and the feedback resistance values R2 and R3, for example, compared with those used in an insulated power supply circuit of a conventional power receiving device that outputs a voltage of about 3.3V or 5V, for example. In the power supply circuit described above, the number of turns of the transformer 21 is set larger than that of the conventional power supply circuit. However, the MOSFET 22 is used in the conventional power supply circuit as the number of turns of the insulating transformer 21 is adjusted. A diode having a large rated voltage is selected with respect to the one having a rated voltage of 150 V or 120 V, and the rectifying diode 23 has a large rated voltage as compared with that used in a conventional power supply circuit. The feedback resistance values R2 and R3 are selected to be lower resistance than those used in conventional power supply circuits. The is selected.

  A configuration example of the power supply circuit is as follows. The turn ratio of the insulating transformer 21 is 1: 1, the MOSFET 22 has a maximum rating of 250V · 7A, and the rectifying diode 23 has a maximum rating of 60V · 3A. The feedback resistance value R2 is 33 kΩ, R3 is 3.83 kΩ, the switching frequency is set to 300 kHz, and a voltage of 33 to 57 V, for example, is applied to the primary winding T1 of the insulating transformer 21. The output of the secondary winding T2 of the insulating transformer 21 can be set to, for example, power 13W and output voltage 24V.

Next, the operation in this embodiment will be described.
The power supply side device detects that the gas detector, which is the power receiving side device, is connected to the network, and is classified according to the power required by the gas detector, so that the power supply to the gas detector can be performed. For example, it starts via the spare pair 18 and is supplied to the output voltage control circuit 20 via the diode bridges 10 and 11.
In the output voltage control circuit 20, a voltage is applied to the primary winding T1 of the insulating transformer 21 when the MOSFET 22 is turned on, and the energy stored thereby is rectified when the MOSFET 22 is turned off. Rectified by the diode 23 and outputted, and a current signal outputted when a current flows through the light emitting diode 31 in the photocoupler 30 is detected by the photodiode 32 and fed back to the control IC 25, and the control IC 25 turns on the MOSFET 22. The ratio between the time and the off time is PWM-controlled based on the current signal from the photocoupler 30.
The output from the output voltage control circuit 20 is supplied to the pump to drive the pump, and is transformed as necessary by, for example, a DC-DC converter and supplied to the amplification system circuit and control system circuit of the gas sensor. Then, a predetermined gas detection operation is performed, and the result is transmitted to a monitoring device or the like connected to a common network using, for example, signal pairs 15 and 16.

Thus, according to the gas detector having the above configuration, when the input voltage supplied from the PoE system is transformed by adjusting the number of turns of the isolation transformer 21, the specifications of the MOSFET 22, the specifications of the rectifying diode 23, and the insulation Since the specifications of the feedback resistance values R2 and R3 connected to the secondary winding T2 of the transformer 21 are optimized and the switching noise reduction circuit is provided, the power supply circuit can be made highly efficient and desired. Therefore, it is possible to secure driving power for a pump with relatively large power consumption and to obtain stable operation.
In addition, since the insulating transformer 21 and the photocoupler 30 constitute an insulating portion that insulates the power receiving side gas detector from the power feeding side device (power source), there is no adverse effect due to a failure or the like. .

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment, A various change can be added.

10, 11 Diode bridge 12, 13 Transformer 15, 16 Signal pair 18 Spare pair (power supply)
20 Output voltage control circuit 21 Isolation transformer 22 MOSFET
23 Diode for rectification 25 Control IC
30 Photocoupler 31 Light Emitting Diode 32 Photodiode 35 Switching Noise Reduction Circuit T1 Primary Winding T2 Secondary Winding G Gate S Source D Drain C1 Capacitor R1 Resistance R2, R3 Feedback Resistance Value

Claims (4)

A gas detector having a pump for introducing a test gas,
A gas detector comprising an insulated power supply circuit that transforms and outputs an input voltage supplied from a power over Ethernet (registered trademark) power supply.   The power supply circuit applies the supplied input voltage to the primary winding of the isolation transformer by controlling the switching element on / off, rectifies and outputs the voltage generated in the secondary winding by the rectifier element, and outputs the isolation transformer. The output from the secondary winding is detected by a photocoupler, and the ratio of the ON time to the OFF time of the switching element is controlled based on a signal from the photocoupler. The gas detector according to 1.   The number of turns of the insulation transformer is set so that the voltage and power necessary for the secondary winding of the insulation transformer can be obtained, and the switching element, the rectifier element, and the insulation are set according to the number of turns of the insulation transformer. The gas detector according to claim 2, wherein a specification of a feedback resistance value connected to the secondary winding of the transformer is selected. The switching element is composed of a MOSFET with a rating of 250V · 7A or more,
Switching noise reduction circuit comprising a capacitor and a resistor connected between one end of the primary winding of the isolation transformer and an intermediate connection point between the other end of the primary winding of the isolation transformer and the drain of the MOSFET The gas detector according to claim 3, comprising:

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