JP2004096843A - Method and apparatus for controlling oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus for controlling an oscillator for reducing the size of the oscillator or a lower cost, by automatically adjusting the characteristics of an FET element constituting the oscillator used for an unattended transportation system of an electromagnetic induction method, for stable operation of the FET element. <P>SOLUTION: A voltage intermediate point B is provided by a circuit 12, that bisects a DC power supply voltage inputted into an inverter circuit. A voltage average point A is provided by a circuit 14, that averages the output voltage on the secondary side of an AC load; a correction signal circuit part 16 is connected between the voltage intermediate point B and the voltage average point A and forms a correction signal, that equalizes the voltages of the voltage middle point B and the voltage average point; and a PWM circuit part 18 applied by a modulated signal, which is corrected by the correction signal. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device and a control method for an oscillator used in an electromagnetic induction type unmanned transfer system.
[0002]
[Prior art]
In the guided wireless type unmanned transport system, the output of the oscillator is supplied to a guide wire buried in the floor to guide the transport vehicle. As shown in FIG. 3, the oscillator includes a half-bridge type DC / AC inverter circuit using P-type and N-type MOSFETs (Metal Oxide Semiconductor Field Effect Transistor) elements 20. These two MOSFET elements are converted into electric power by a PWM (Pulse Width Modulation) method having a switching frequency of about 100 kHz, and an output of an induction wire is obtained.
[0003]
In order to accurately guide the carrier, it is preferable that the guide wire output is a low distortion sine wave. For that purpose, it is necessary to increase the resonance circuit including the coil and the capacitor shown in FIG. 3 and increase the switching frequency of the two MOSFET elements 20.
[0004]
In addition, in order to reduce the size and cost of the oscillator, it is general to further increase the switching frequency of the MOSFET element 20 from 300 kHz to 500 kHz. However, by increasing the switching frequency, the output of the induction wire between a and b shown in FIG. 3 is distorted near the maximum amplitude.
[0005]
This phenomenon is generally called latch-up, and is considered to be caused by a variation in switching characteristics of the P-type and N-type MOSFET elements 20 (in this case, including a gate drive circuit and an arithmetic circuit). When the static and dynamic characteristics (temporal thermal characteristics and switching characteristics, etc.) of the P-type and N-type MOSFET elements 20 are not in a complementary relationship, the operating point of the switching operation of the MOSFET element 20 is different. It is caused by displacement.
[0006]
Conventionally, in order to eliminate this latch-up, the displacement of the operating point has been corrected by manually adjusting the characteristics of the MOSFET element 20 for each individual oscillator. Specifically, the output waveform of the induction wire is measured with an oscilloscope or the like when adjusting the shipment of the oscillator, and the characteristic is adjusted by manually changing the variable resistance in the PWM circuit. Had been corrected.
[0007]
[Problems to be solved by the invention]
However, even if the characteristics of the MOSFET element 20 are manually adjusted, the characteristics fluctuate due to circuit offset and drift, overheating of the MOSFET element 20, and the like, and the operating point is displaced. That is, the operating point of the switching operation in the P-type and N-type MOSFET elements 20 is constantly displaced, and these MOSFET elements 20 are not operating stably. Therefore, the switching frequency of the MOSFET element 20 cannot be increased, and it has been difficult to reduce the size and cost of the oscillator.
[0008]
An object of the present invention is to automatically adjust the characteristics of FET elements constituting an oscillator used in an electromagnetic induction type unmanned transfer system, stably operate the FET elements, and reduce the size and cost of the oscillator. And a control method for the oscillator.
[0009]
[Means for Solving the Problems]
In the oscillator control device according to the present invention, the oscillator includes a half-bridge type DC / AC inverter circuit, and a voltage midpoint provided by a circuit that divides a DC power supply voltage input to the inverter circuit into two equal parts, It is connected between a voltage average point provided by a circuit for averaging the output voltage on the secondary side of the load and the voltage midpoint and the voltage average point, and equalizes the voltages at the voltage midpoint and the voltage average point. The object is achieved by a configuration including a correction signal circuit unit for forming a correction signal and a PWM circuit unit to which a modulated signal corrected by the correction signal is input.
[0010]
By adopting the above configuration, the corrected modulated signal is input to the PWM circuit, so that the operation of the FET element forming the inverter circuit can be stabilized. In the present invention, that the FET element operates stably means a state in which the operating points of the switching operations of the P-type and N-type MOSFET elements operate in a uniform state.
[0011]
Furthermore, the oscillator control device according to the present invention includes that the correction signal circuit unit in the above-described control device is configured by two anti-parallel photocouplers. By employing this configuration, the voltage difference between the voltage midpoint and the voltage average point can be detected, and the main circuit and the control circuit can be isolated.
[0012]
Further, in the oscillator control method according to the present invention, a voltage midpoint provided by a circuit for bisecting a DC power supply voltage input to a half-bridge type DC / AC inverter circuit constituting the oscillator; A correction signal circuit section connected between a voltage average point provided by a circuit for averaging the output voltage on the secondary side forms a correction signal for equalizing the voltage at the voltage midpoint and the voltage at the voltage average point. And a step of inputting the corrected modulated signal to a PWM circuit section.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
An oscillator control device 10 according to an embodiment of the present invention will be described with reference to the drawings. In the following, the same components as those in the conventional example are denoted by the same reference numerals, and detailed illustration or description thereof is omitted.
[0014]
As shown in FIG. 1, an oscillator control device 10 according to the present embodiment includes a circuit in which an oscillator is formed of a half-bridge type DC / AC inverter circuit and divides a DC power supply voltage input to the inverter circuit into two equal parts. 12 and a voltage average point A provided by a circuit 14 for averaging the output voltage on the secondary side of the AC load, and a connection between the voltage midpoint B and the voltage average point A. And a correction signal circuit section 16 for forming a correction signal for equalizing the voltages at the voltage midpoint B and the voltage average point A, and a PWM circuit section 18 to which a modulated signal corrected by the correction signal is input. Is done.
[0015]
A P-type MOSFET element 20a and an N-type MOSFET element 20b are used in a half-bridge type DC / AC inverter circuit constituting an oscillator. An AC load is connected to a connection line between the source of the P-type MOSFET element 20a and the source of the N-type MOSFET element 20b. The AC load includes a coil, a capacitor, a transformer (not shown), and the like.
[0016]
The circuit 12 for dividing the DC voltage input to the half-bridge DC / AC inverter circuit into two equal parts is configured by connecting two resistance elements having the same resistance value in series. The two resistance elements are provided between the power supply voltages. The midpoint of the connection line connecting the two resistance elements (point B in FIG. 1) is the midpoint of the voltage that divides the DC power supply voltage into two equal parts.
[0017]
The circuit 14 for averaging the output voltage on the secondary side of the AC load is configured by connecting two capacitor elements having the same capacitance value in series. The two capacitor elements are provided between power supply voltages, and an AC load is connected to a middle point of a connection line connecting the two capacitor elements. The middle point (point A in FIG. 1) of the connection line connecting the two capacitor elements is a voltage average point where the output voltage on the secondary side of the AC load is averaged.
[0018]
The correction signal circuit section 16 is connected between the voltage midpoint B and the voltage average point A. The correction signal circuit section 16 is configured by connecting two photocouplers 22 in antiparallel. The two photocouplers 22 form a correction signal using the voltage difference between the voltage middle point B and the voltage average point A. Output lines from the two photocouplers 22 are connected to a PWM circuit 18 described later.
[0019]
As shown in FIG. 2, the PWM circuit section 18 mainly includes a modulated signal transmitter 18a and a comparator 18b. The modulated signal from the modulated signal transmitter 18a and the modulated signal from the modulated signal transmitter 24 are input to the comparator 18b. The potential of the modulated signal from the modulated signal transmitter 24 is corrected by the correction signal formed by the correction signal circuit section 16, and the corrected modulated signal is input to the comparator 18b. The output of the comparator 18b is input to the gate drive circuit, and the gate drive circuit controls the N-type and P-type MOSFETs 20.
[0020]
Next, the operation of the present embodiment will be described. If the characteristics of the P-type and N-type MOSFET elements 20 vary, the voltage at the voltage middle point B (1/2 of the power supply voltage Vcc) and the voltage at the voltage average point A (the output voltage on the secondary side of the AC load) (Averaged voltage). This voltage difference is read by a photocoupler 22 connected in anti-parallel. This makes it possible to detect which of the voltage at the voltage midpoint B and the voltage at the voltage average point A is higher and how much. The feature of the present invention is to detect a voltage difference between the voltage at the voltage midpoint B and the voltage at the voltage average point A, and to eliminate the voltage difference (by changing the voltage at the voltage average point to two minutes of the power supply voltage). (1) to form a correction signal.
[0021]
For example, assume that the voltage at the voltage middle point B is Vb, and the voltage at the voltage average point A is Va. Va and Vb are compared by the photocoupler 22 connected in anti-parallel, and when Va is larger than Vb, a correction signal for decreasing the ON ratio (Duty) of the P-type MOSFET element 20a is supplied to the photocoupler 22. Is formed using the output of Conversely, when Va is smaller than Vb, a correction signal for lowering the ON ratio (Duty) of the N-type MOSFET element 20b is formed using the output of the photocoupler 22.
[0022]
The potential of the signal from the modulated signal transmitter 24 is corrected using the correction signal formed by the correction signal circuit unit 16. By correcting the potential of the signal from the modulated signal transmitter 24, the ON ratio of the P-type or N-type MOSFET element 20 is reduced, and the operating point in the switching operation of each MOSFET element 20 is corrected. As a result, Va and Vb become equal voltages.
[0023]
Therefore, since each MOSFET element 20 operates stably, the output waveform is not distorted near the maximum amplitude even at a high switching frequency. That is, since each MOSFET element 20 can be used at a high switching frequency, it is possible to reduce the size and cost of the oscillator. Further, since each MOSFET element 20 operates stably, the range of the dynamic range of the output voltage (induction line output) in the oscillator is widened, and the guided vehicle can be guided more stably.
[0024]
The present invention can be practiced in various modified, modified, and modified forms based on the knowledge of those skilled in the art without departing from the spirit of the present invention.
[0025]
【The invention's effect】
According to the oscillator control device of the present invention, the MOSFET element is arranged by disposing the anti-parallel-connected photocoupler between the midpoint of the voltage and the average point of the voltage, and correcting the modulated signal using the output of the photocoupler. Can be corrected. Therefore, it becomes possible to automatically correct the displacement of the operating point due to the temperature rise of the MOSFET element over time or the like. That is, since the MOSFET element operates stably, the reliability of the operation of the oscillator is improved.
[0026]
Further, the main circuit (output operation unit such as an AC load) and the control circuit (operation unit such as a PWM circuit) can be insulated simply by using an inexpensive element such as a photocoupler. Therefore, unnecessary signals are not mixed into the control circuit, and the reliability of the oscillator is improved.
[0027]
Further, since it becomes possible to use the MOSFET element at a higher switching frequency than before, it is possible to reduce the size, efficiency, and cost of the oscillator.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an oscillator control device according to the present invention.
FIG. 2 is a configuration diagram of a control circuit portion in the oscillator control device according to the present invention.
FIG. 3 is a configuration diagram of a conventional oscillator control device.
[Explanation of symbols]
10: Oscillator control device 12: Circuit for bisecting the power supply voltage 14: Circuit for averaging the output voltage on the secondary side of the AC load 16: Correction signal circuit 18: PWM circuit 18a: Modulation signal transmitter 18b : Comparator 20: MOSFET element 20 a: P-type MOSFET element 20 b: N-type MOSFET element 22: Photocoupler 24: Modulated signal transmitter

Claims (3)

In an oscillator control device used for an electromagnetic induction type unmanned transfer system,
A voltage midpoint provided by a circuit in which the oscillator is formed of a half-bridge type DC / AC inverter circuit and divides a DC power supply voltage input to the inverter circuit into two equal parts;
A voltage average point provided by a circuit for averaging the output voltage on the secondary side of the AC load;
A correction signal circuit unit that is connected between the voltage midpoint and the voltage average point, and forms a correction signal that equalizes the voltages at the voltage midpoint and the voltage average point,
A PWM circuit to which the modulated signal corrected by the correction signal is input;
Oscillator control device including: 2. The oscillator control device according to claim 1, wherein the correction signal circuit unit includes two photocouplers connected in anti-parallel. In a control method of an oscillator used for an electromagnetic induction type unmanned transfer system,
A circuit for averaging a voltage midpoint provided by a circuit for bisecting a DC power supply voltage input to a half-bridge type DC / AC inverter circuit constituting the oscillator, and a secondary output voltage of an AC load. A correction signal circuit unit connected between the voltage average point provided by the step of forming a correction signal that equalizes the voltage of the voltage midpoint and the voltage average point,
Inputting the corrected modulated signal to a PWM circuit unit;
An oscillator control method including:

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