JP2003111460A - Fan motor with surge current blocking circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fan motor provided with a switching noise blocking capacitor being driven through a rectified power supply circuit in which the surge current can be reduced at the start of the fan motor. SOLUTION: An MOS-FET is connected between a power supply circuit and a drive circuit and the gate of the MOS-FET is controlled by the output voltage from a time constant circuit comprising a resistor and a capacitor thus reducing the surge current and resetting normal operation.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fan motor driven by a current supplied from a rectifier circuit, and more particularly to a fan motor having a rush current prevention circuit at startup. . 2. Description of the Related Art FIG.
It is an example of a drive circuit of a fan motor to which a current is supplied from a rectifier circuit. In FIG. 4A, 1 is a rectifier circuit for supplying power, 2 is a switch, 3 is a backflow prevention diode, 4 is a Hall element, 5 is a conduction control signal generation circuit, 6
And 7 are switching transistors, 8 and 9 are stator windings of the motor, and 10 is a switching noise preventing capacitor. The drive circuit shown in FIG. 4A is supplied with a direct current from a rectifier circuit 1 through a switch 2 by a diode 3 and a switching control signal is generated by an energization control signal generating circuit 5 which receives the output of a Hall element 4. Transistors 6 and 7
To alternately energize the two motor stator windings 8 and 9 to rotate the rotor in one direction to operate as a fan motor. [0004] However, FIG. 4 (a)
In order to start the fan motor from the stationary state by the drive circuit of FIG.
As shown in FIG. 3C, in addition to the starting current to the motor, a charging current to the switching noise preventing capacitor 10 flows, and the current of the rectifier circuit 1 is higher than the rated current for operating the fan motor in a steady state. As a result, there is a concern that the overcurrent protection circuit of the rectifier circuit operates and the start cannot be performed, and there arises a problem that it is necessary to change the rating of the rectifier circuit to one having more margin. An object of the present invention is to provide a fan motor that can suppress the inrush current with a simple circuit configuration without changing the rating of the rectifier circuit. Conventionally, various means for reducing the inrush current by charging the switching noise preventing capacitor have been proposed and implemented. The circuit shown in FIG. 2 is different from the conventional circuit shown in FIG. 4 in that a switching noise preventing capacitor 10, a diode 3, a conduction control signal generating circuit 5, and two stator windings 9 and 10 are provided. In this configuration, a resistor 11 is inserted between connection points. In the configuration of FIG. 2, the voltage applied to the switching noise preventing capacitor 10 is reduced by the resistor 11, so that the charging current is reduced and the inrush current is suppressed, but the noise reduction effect is reduced. Has the disadvantage of FIG. 3 shows another example of a circuit configuration, which is different from the prior art circuit shown in FIG. 4 in that a capacitor 10 for preventing switching noise, a diode 3, a conduction control signal generating circuit 5, and two stator windings 9 are provided. , 10 between the resistor 11
Are connected in series, and a switch 12 which operates in parallel with the resistor 11 by detecting an output terminal voltage of the resistor 11
At startup, the charging current of the switching noise preventing capacitor 10 is reduced by the voltage drop of the resistor 11 to suppress the inrush current, and after startup, the motor current is reduced and the voltage drop of the resistor is reduced. Therefore, the resistance 11
The output terminal voltage of the resistor 11 rises, and when this voltage is detected, the switch 12-1 operates to short-circuit both ends of the resistor 11. Due to the short-circuit of the resistor 11, no winding current flows through the resistor 11, and heat generation can be avoided without increasing the resistance. However, the circuit configuration is complicated and expensive. According to the present invention, a MOS-type field effect transistor (hereinafter referred to as a MOS-FET) is inserted between a power supply circuit and a switching noise preventing capacitor. The gate voltage of the device
The time constant circuit is used to make a gradual change, the waveform of the charging current for the switching noise prevention capacitor is made gentler, and the inrush current is reduced. It solves by controlling so that it becomes. FIG. 1A is a connection diagram of a drive circuit of a fan motor having an inrush current prevention circuit according to the present invention. FIG. 1A shows a connection between a switch 2 and a diode 3 in the prior art circuit shown in FIG. , A MOS-FET 16 is provided.
A resistor 13 and a resistor 14 are connected in series between the ground and the ground, a capacitor 15 for time constant is arranged between the connection point and the switch 2, and the connection point is connected to a gate terminal of the MOS-FET 16. ing. The operation of the driving circuit according to the present invention shown in FIG. 1A will be described. When the switch 2 is turned on as shown in FIG. 3B, the gate terminal voltage of the MOS-FET 16 gradually increases due to the time constant of the resistors 13, 14, and the capacitor 15 as shown in FIG. As a result, the voltage of the switching noise preventing capacitor 10 gradually increases. When the charging of the time constant capacitor 15 is completed, the gate terminal voltage of the MOS-FET 16 becomes a value obtained by dividing the terminal voltage of the switch 2 by the resistors 13 and 14, and this voltage completely turns on the MOS-FET 16.
State. The output voltage of the MOS-FET 16 in the above-described operation gradually rises as shown in FIG.
16 is completely turned on and the internal resistance is minimized, so that the internal resistance becomes constant and is supplied to the windings as a predetermined voltage for driving the motor. In the present invention, a MOS-FET 16 is connected as a current control means between a power supply terminal and a conduction control circuit to suppress an inrush current due to a charging current of the switching noise preventing capacitor 10, and is used at the time of startup. Is to reduce the charging current of the switching noise preventing capacitor 10 by lowering the voltage, and to increase the voltage after start-up so as to be in normal operation. In addition to the advantage that the control of the MOS-FET 16 is easy, Since the internal resistance during operation is extremely small, the loss can be reduced. The fan motor provided with the inrush current prevention circuit according to the present invention has the above-described configuration, so that not only can the inrush current be suppressed but also the loss due to the internal resistance of the MOS-FET can be minimized. Thus, there is an effect that control can be performed so as to obtain the normal operation state.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of an embodiment according to the present invention and an explanatory diagram for explaining its operation. FIG. 2 is an improved circuit diagram of the prior art. FIG. 3 is another improved circuit diagram of the prior art. FIG. 4 is an explanatory diagram illustrating an example of a circuit diagram of the related art and an operation thereof. [Description of Signs] 1 Rectifier circuit for power supply 2 Switch 3 Diode 4 Hall element 5 Conduction control signal generation circuit 6, 7 Switching transistor 8, 9 Stator winding 10 Switching noise prevention capacitor 11 Resistance 12 Voltage detection circuit 12- 1 switch 13, 14 resistor 15 time constant capacitor 16 MOS-FET

Claims (1)

Claims 1. A stator provided with a stator winding, and a rotor provided with a permanent magnet and a fan, which is rotatably supported opposite to the stator via an air gap and is rotatably supported. A Hall element for detecting the magnetic pole position of the permanent magnet, an energization control circuit for controlling energization to the stator winding by an output voltage of the Hall element, and a backflow prevention between a power supply terminal and the energization control circuit. And a rush current prevention circuit provided with a switching noise prevention capacitor between the output terminal of the diode and the ground, wherein a series connection is provided between the power supply terminal and the conduction control circuit. A connected MOS-type field-effect transistor, two resistors connected in series between a power supply terminal and a ground, and a capacitor between a connection point of the two resistors and a power supply terminal. Mo Juan motor comprising an inrush current preventing circuit to the gate of the form field effect transistor is configured to be connected, characterized by.