JP2533432B2 - Phase detection circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase detection circuit for a heat sensitive wire or the like whose phase angle changes.

[0002]

2. Description of the Related Art As an example of a circuit for detecting a phase difference between a voltage applied to an object to be measured such as a heat sensitive wire and a current flowing through the object, a technique disclosed in Japanese Patent Laid-Open No. 3-77036 is known.

[0003]

SUMMARY OF THE INVENTION In the above conventional technique,
The time corresponding to the phase difference between voltage and current is detected by detecting the zero point of the voltage applied to the DUT and the zero point of the current flowing through it, and measuring the section between these zero points with the measuring means. Since the width is obtained, there is a problem that the number of parts is increased as a whole.

SUMMARY OF THE INVENTION The present invention solves the above problems of the prior art, and an object of the present invention is to provide a circuit capable of detecting the phase difference of an object to be measured with an extremely simple structure.

[0005]

In order to achieve the above object, the phase detection circuit of the present invention connects one end of an AC power supply to the base of a transistor through a device under test whose phase angle changes, In parallel with the base and emitter of the transistor,
The diode D1 is connected so as to have a polarity opposite to the base-emitter polarity of the transistor, and the other end of the AC power supply is
The voltage applied to the DUT from the connection point of the diode D2 and the resistor is connected to the collector of the same transistor through the resistor and the diode D2, the AC power source is divided and applied to the emitter of the transistor. The output is obtained with a time width corresponding to the phase difference between the flowing currents. The base-emitter characteristic of a transistor is equivalent to that of a diode. In a PNP transistor, the base corresponds to the cathode of the diode, and in the NPN transistor, the base corresponds to the anode of the diode. Therefore, the transistor and the diode D1 are connected so that their characteristics, that is, polarities are reversed.

[0006]

When a negative half-wave current flows through the device under test, the base current flows through the transistor and the emitter and collector are in a conductive state, while the positive half wave is applied to the device under test. At this time, a voltage corresponding to the power supply is applied between the emitter and collector of the transistor. When these two states are both satisfied, an output having a time width corresponding to the phase difference between the voltage applied to the DUT and the current flowing through the DUT is output from the connecting portion between the diode D2 and the resistor.

[0007]

1 is a circuit diagram in which the circuit 2 of the present invention is applied to a temperature control device for a heating tool such as an electric carpet.
When the voltage is applied, the temperature-sensitive layer 7 of the object to be measured mounted on the heater 8
Indicates that the phase between the applied voltage and the flowing current changes in accordance with the temperature, and this phase difference is detected by the phase detection circuit 2.

The phase difference signal P detected by the phase detection circuit 2 is divided and output to the control unit 3 in the next stage. The divided signal P is transferred from the transistor Q2 to the NAND gate 4,
It is processed by the capacitor C, the variable resistor VR, the inverter 5 and the D-type flip-flop 6, and the transistor Q corresponds to the output from the D-type flip-flop 6.
3 turns on / off a relay 9 as a switch means.

FIG. 2 is a circuit diagram showing an essential part of the present invention. Resistors R1 and R2 are connected in series to a power source 1. At this connection and one end of the power source 1, the emitter-base of the transistor Q1 and the DUT 10 are connected. Are connected in series. In addition, the diode D1 is placed between the emitter and the base of the transistor Q1 so that the polarity is opposite to the polarity between the base and the emitter of the transistor.
Are connected in parallel, and the collector of transistor Q1 and power supply 1
A diode D2 and a resistor R3 are connected in series to the other end of the.

FIG. 3 is a waveform diagram of the voltage v applied to the device under test 10 and the current i flowing therein, and FIG. 4 is the transistor Q1.
Of the base current iB, the current i flows from the diode D1 to the ground side during the time t1 to t3 and the base current iB does not flow, and flows between the emitter and the base of the transistor Q1 during the time t3 to t5. Flowing.

FIG. 5 shows the collector voltage v of the transistor Q1.
C, the voltage v1 is applied between the emitter and collector of the transistor Q1 between times t2 and t4, and the voltage v1 is applied between times t4 and t4.
Between 6 is blocked by the diode D2 and no voltage is applied to the collector.

Therefore, the voltage v1 is applied to the resistor R3 when the base current iB of the transistor Q1 flows and the voltage is applied in the forward direction to the diode D2 (when the transistor Q1 and the diode D2 are both conductive). That is, between time t3 and t4, this time width is 1:
Correspond to 1. At this time, a current flows through the diode D2 to the resistor R3, and a current flows through the connection point P between the two, as shown in FIG.

It should be noted that another resistor R4 is interposed in series between the diode D2 and the resistor R3 (FIG. 1) to divide the voltage, and both resistors R3,
When the base of the transistor Q2 is connected to the connection point of R4, the collector output S of the transistor Q2 is adjusted as shown in FIG. 7, and the operation of the subsequent stage is stabilized.

FIG. 8 shows the output T of the inverter 5. The time widths T1 and T2 of the low potential "L" are adjusted by the variable resistor VR, and the output T is "L" at the time of the falling point of the output P.
At this time, as shown in FIG. 9, the output U of the D-type flip-flop 6 becomes "L", and the transistor Q3 turns off the relay 9. On the other hand, contrary to the above, when the output T is at the high potential "H" at the time of the falling point of the output P, the output U becomes "H" and the transistor Q3 turns on the relay 9.

In the above, the transistor Q1 is set to PN.
Although explained as a P type, it is also possible to make it an NPN type. In this case, the transistor Q2 is a PNP type, and ▲ +
The same effect can be obtained if the power source is used as the power source. A Zener diode may be used instead of the transistor Q2.

[0016]

As described above, according to the present invention, the time width corresponding to the phase difference between the voltage applied to the DUT and the flowing current can be obtained with the transistor, the diode, and the parts having a small resistance. Thus, it is possible to provide a phase detection device which can be made smaller and cheaper than the conventional one. Further, since a low voltage obtained by arbitrarily dividing the power supply voltage by two resistors is applied to the transistor and the device under test, the transistor and the device under test may have a low withstand voltage standard. When the DUT is short-circuited, the transistor will not be destroyed and its collector output will be zero.On the other hand, when the DUT is disconnected, the base input of the transistor will be lost, so its collector output will be zero, and if the short-circuit or disconnection is restored. The operation of the phase detection circuit naturally returns to normal. Further, when the object to be measured is a heat-sensitive wire, the transistor detects and outputs the phase difference corresponding to only the heat-sensitive wire, so that the phase difference corresponding to temperature can be obtained regardless of the dimensional accuracy of the heat-sensitive wire.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a heating tool having a temperature control device using a circuit of the present invention.

FIG. 2 is a circuit diagram showing a main part of the present invention.

FIG. 3 is a waveform diagram of a voltage applied to the object to be measured and a current flowing through the voltage.

FIG. 4 is a waveform diagram of a base current of a transistor Q1.

FIG. 5 is a waveform diagram of a collector voltage of a transistor Q1.

FIG. 6 is an output waveform diagram of point P in FIG.

FIG. 7 is an output waveform diagram at point S in FIG.

FIG. 8 is an output waveform diagram at point T in FIG.

FIG. 9 is an output waveform diagram at a point U in FIG.

[Explanation of symbols]

 1 AC power supply 2 Phase detection circuit 3 Control unit 10 DUT Q1 Transistors D1, D2 Diodes R1, R2, R3, R4 Resistance

Claims (1)

(57) [Claims] 1. An alternating current power supply is connected to a base of a transistor through an object to be measured whose phase angle changes, and the base and emitter of the transistor are connected in parallel to the base-emitter polarity of the transistor and a reverse polarity. , The other end of the AC power supply is connected to the collector of the transistor through a resistor and a diode D2, and the AC power supply is divided and applied to the emitter of the transistor.
A phase detection circuit characterized in that an output having a time width corresponding to a phase difference between a voltage applied to an object to be measured and a current flowing therethrough is obtained from a connection point between the diode D2 and a resistor.