JPH077952A - Fan motor drive circuit for air conditioner - Google Patents

Abstract

(57) [Abstract] [Purpose] To downsize the components of the fan motor drive circuit and reduce the circuit mounting scale. [Structure] A voltage for driving the fan motor 1 is created by a converter circuit 6 and a step-down chopper circuit 5. On the other hand, the control power supplied to the control unit 12 is one of a high frequency transformer 7 connected to the converter circuit, a switching circuit 8 connected to the high frequency transformer, and a plurality of secondary windings of the high frequency transformer. Connected to one secondary winding 7c,
It is connected to the first rectifying / smoothing circuit 9 for supplying the rectified and smoothed output to the inverter 2 and the step-down chopper circuit and another secondary winding 7d, and supplies the rectified and smoothed output to the control unit. And a second rectifying / smoothing circuit 10 for As the converter circuit, a switching converter that makes the output voltage 1 / n (n is a number of 1 or more) of the input voltage can also be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fan motor drive circuit for an air conditioner, and more particularly to the structure of a drive power supply and a control power supply for a fan motor incorporating an inverter.

[0002]

2. Description of the Related Art Conventionally, as a drive circuit of a DC fan motor (hereinafter, simply referred to as a fan motor) mounted on an indoor unit of an air conditioner, a voltage applied to the fan motor is arbitrarily changed by an external step-down circuit. A PAM control method is used to control the number of rotations. FIG. 4 shows an example of a conventionally known fan motor drive circuit of this system. As is clear from this figure, when performing PAM control, the AC-DC converter 14 and the switching circuit 1
8, switching transformer 19, rectifying / smoothing circuit 2
0, a control unit 17 that controls the rotation speed of the fan motor 21 by controlling the duty of the current that flows through the switching transformer 19, the control unit 17 and the fan motor 2
1 requires a low-frequency transformer 15 and a control voltage generating circuit 16 for supplying electric power.

In the fan motor drive circuit of this system, since a relatively large current is applied, there is a limit to the miniaturization of the switching circuit 18, the switching transformer 19, and the smoothing circuit 20, so that the indoor unit can be miniaturized, or It was difficult to increase the degree of freedom in designing indoor units. Therefore, in order to eliminate such inconvenience, conventionally, a high-voltage inverter circuit is built in the motor, and a simple circuit configuration using a drive circuit and a step-down chopper circuit of a method of controlling a current duty ratio while maintaining a high voltage. Has proposed a drive circuit that obtains an arbitrary smoothed voltage.

FIG. 5 shows an example of a circuit configuration in the case where a high voltage inverter circuit composed of power elements Q _{1 to} Q ₆ is incorporated in a motor (described in Japanese Utility Model Publication No. 57-59191). In the inverter circuit configuration of this example, as a power supply for controlling the bases of the power elements Q _{1 to} Q ₆ , one set of power supplies for Q _{4 to} Q ₆ to which the emitters are commonly connected and the emitters are independent. in which Q _1, Q _2, Q ₃ a power supply for 3
In total, four sets of independent power supplies are required. Therefore, in the drive circuit of FIG. 5, five pairs of secondary windings are provided in the switching transformer Tr, and a rectifying diode D and a smoothing capacitor C ₀ are connected to each secondary winding. For power elements Q _{4 to} Q ₆ and Q ₁ , Q ₂ , Q ₃
Power supply V ₁ -V ₄ for the control power supply V _C and the control power supply V _C for the other set. According to this circuit, since the switching power supply is used as the power supply of the high-voltage inverter circuit, the transformer can be downsized and the smoothing capacitor can be downsized, and the circuit can be downsized.
However, the number of parts is still large, and the use of a fan motor with a built-in high-voltage inverter causes a disadvantage that the cost is rather increased.

On the other hand, when the motor voltage is obtained by using the step-down chopper circuit, the power supply for driving the fan motor is connected to the AC input, so that a new power supply insulated from the control unit is required. That is, in addition to the conventional control power supply, it is necessary to add one more power supply, which causes a disadvantage that the transformer and the rectifying / smoothing circuit are enlarged.

[0006]

In order to solve the disadvantages of the prior art and downsize the drive circuit of the fan motor having the built-in inverter, the control power supply is simply changed to a switching circuit or the inverter drive power supply is simply changed. It is not enough to configure with a high-voltage chopper circuit, and it is necessary to develop a circuit configuration in which the control power supply and the inverter drive power supply are insulated and made into a common component.

The present invention has been made to solve the above problems, and an object thereof is to miniaturize a drive circuit of a fan motor incorporating an inverter.

[0008]

In order to solve the above-mentioned problems, the present invention provides a fan motor having a built-in inverter,
A control unit that controls each part of the air conditioner including the rotation speed control of the fan motor, a converter circuit that converts an AC input into a DC output, and the output of the converter circuit is stepped down according to a command from the control unit, In a fan motor drive circuit of an air conditioner, which comprises a step-down chopper circuit for supplying power to the fan motor, and a power supply circuit for supplying power to the inverter and the control unit and the step-down chopper circuit,
A high-frequency transformer having a primary winding connected to the high-potential side of the converter circuit output and a plurality of secondary windings, and an emitter-collector in series with the primary winding of the high-frequency transformer. A switching circuit that is connected and whose base is connected to a high-frequency switching signal source to supply high-frequency current to the primary winding of the high-frequency transformer; and one of the secondary windings of the secondary winding of the high-frequency transformer. A first rectifying / smoothing circuit that is connected and supplies the rectified and smoothed output to the inverter and the step-down chopper circuit and another secondary winding, and the rectified and smoothed output is connected to the control unit. And a second rectifying / smoothing circuit for supplying

In the converter circuit, in order to replace the components of the switching power supply and the high-voltage chopper circuit with low-voltage components, after converting the AC input into the DC output, the input voltage is 1 / n (where n is It is particularly preferable to include a switching converter that outputs a number of 1 or more).

[0010]

When a high frequency transformer having a plurality of secondary windings is provided, and a power supply for driving an inverter (fan motor) and a power supply for control are obtained from each of the plurality of secondary windings, the respective power supplies are mutually isolated. Insulation is prevented, mutual interference between power sources is prevented, and the size and cost of the transformer and smoothing capacitor can be reduced. Further, if the configuration is such that the DC power on the primary side of the power source is obtained from the converter circuit for driving the fan motor, it is not necessary to separately provide a circuit for extracting the DC power, and therefore the circuit configuration becomes simple.
On the other hand, if a circuit configuration that creates a voltage for driving a fan motor using a converter circuit and a step-down chopper circuit that is connected to the output side of the converter circuit, the circuit configuration is simpler than that of the method using a conventional switching transformer. Therefore, the number of parts can be reduced. Further, by increasing the frequency, it is possible to reduce the size and cost of the reactor and the capacitor that form the step-down chopper circuit. Therefore, it is possible to reduce the size and cost of the drive circuit of the fan motor having the built-in inverter.

[0011]

FIG. 1 shows an embodiment of a fan motor drive circuit according to the present invention. As is clear from this figure, the fan motor drive circuit of this example has a built-in inverter 2 and is capable of controlling the number of revolutions according to the magnitude of the input voltage, and the input voltage of the fan motor 1. For controlling the switching element 4, a duty control circuit 3 for controlling the operation of the switching element 4, a reactor L ₀ ,
Step-down chopper circuit 5 having a capacitor C ₀ and a freewheeling diode D ₀ , a converter circuit 6 for converting an AC input into a DC output, a high frequency transformer 7 having a primary winding and two secondary windings, and the high frequency wave. A switching circuit 8 for energizing the primary winding of the transformer 7 with a high frequency, a controller 12 for controlling each part of the air conditioner including control of the fan motor speed, and a rectifying and smoothing output of one of the secondary windings. The external power supply 9 supplied to the inverter 2 and the duty control circuit 3, and the control power supply 10 that rectifies and smoothes the output of the other secondary winding and supplies the output to the control unit 12, and the control unit 1.
The level shift circuit 13 insulates the rotation speed command output from the fan motor 1 to the fan motor 1. Reference numeral 11 in the figure denotes a high frequency transformer 7 and a switching circuit 8.
And a switching power supply including an external power supply 9 and a control power supply 10.

FIG. 2 shows a more specific circuit configuration of the switching power supply 11. As is clear from the figure, the switching circuit 8 of this example includes a transistor Tr ₁ , diodes D _{1 to} D ₃ , a Zener diode ZD _1, and a resistor R _1.
It is composed of _{1 to} R ₅ and capacitors C _{1 to} C ₃ .

The operation of the fan motor drive circuit according to this example will be described below.

An AC input is applied to the converter circuit 6,
When a DC output is output from the converter circuit 6, the switching circuit 8 of the switching power supply 11 operates. When a direct current (140 V) is applied to the switching power supply 11,
A high frequency current flows through the primary winding 7a of the high frequency transformer 7. The electric power stored in the primary winding 7a at the timing when the transistor Tr ₁ is turned off is
₁ base control winding 7b and two secondary windings 7c, 7d
And a high frequency voltage is induced in each winding. The voltage induced in the base control winding 7b is rectified and smoothed by the rectifying diode D ₁ and the smoothing capacitor C ₂ , and discharged through the resistor R ₂ . The base current of the transistor Tr ₁ is the voltage induced in the opposite to the base control winding 7b, resistors R ₁ and is fed through capacitor C _1, to turn on the transistor Tr _1. The voltage induced in each of the secondary windings 7c and 7d is rectified and smoothed by the external power supply 9 or the control power supply 10 to become a DC power supply. The output voltage of the external power supply 9 is supplied to the inverter 2 and the duty control circuit 3 shown in FIG.
The output voltage of is supplied to the control unit 12. Control unit 12
Starts operation when a voltage is supplied, controls the air conditioner, and outputs the fan motor rotation speed command as a digital signal in response to a command from the user and the output of various sensors provided in the air conditioner. Output to the level shift circuit 13. When the digital signal is input, the level shift circuit 13 insulates the signal, smoothes it, and outputs it to the duty control circuit 3 as an analog command voltage. The duty control circuit 3 controls the energizing current by turning on / off the switching element 4 at a high frequency (about 50 kHz) with a duty corresponding to the command voltage value.
When the switching element 4 is turned on, a current flows from the converter circuit 6 to the reactor L _0, to charge the capacitor C _0. When the switching element 4 is turned off, the current flowing through the reactor L ₀ as the return current continues to flow to the reactor L ₀ through the freewheeling diode D _0. On this occasion,
A smoothed voltage is output across the capacitor C ₀ according to the on-duty ratio and the current flowing through the fan motor 1.
The fan motor 1 has a built-in inverter 2 and drives the fan motor 1 at a rotation speed corresponding to the smoothed voltage.

In the fan motor drive circuit of this embodiment, the high frequency transformer 7 is used to obtain the fan motor drive power source and the control unit power source. Therefore, the high frequency transformer 7, the external power source 9 and the control power source 10 have a small smoothing capacitor. Can be converted. Further, since the DC power on the primary side of the switching power supply 11 is obtained from the output of the converter circuit 6 for the fan motor, there is no need to provide a circuit for extracting the DC power, and the circuit configuration can be simplified. it can. Further, since the step-down chopper circuit 5 is used to generate the voltage for driving the fan motor, the circuit configuration is simpler and the number of parts can be reduced and the frequency can be increased as compared with the conventional method using the switching transformer. By so doing, the reactor L ₀ and the capacitor C ₀ can be downsized. Therefore, it is possible to reduce the size and cost of the drive circuit of the fan motor having the built-in inverter.

Incidentally, in place of the converter circuit 6 in the above embodiment, as shown in FIG. 5, when n is defined as a number of 1 or more, it is possible to use a switching converter which makes the output voltage 1 / n. is there. When this switching converter is used as the converter circuit, the parts of the step-down chopper circuit 5 and the switching power supply 11 can be replaced with low-voltage parts, and the circuit can be further downsized and the cost can be reduced. Furthermore, if a resonance type converter is used, switching loss can be reduced, so that the frequency of the circuit can be increased, and the converter circuit can be miniaturized.

[0017]

As described above, according to the present invention,
Since the input voltage of the fan motor is controlled by the step-down chopper circuit, the circuit configuration becomes simpler and the size and cost can be reduced as compared with the case where the conventional switching transformer is used.

Further, since the fan motor drive power source and the control unit power source are obtained by using the switching power source equipped with the high frequency transformer, the external dimensions are about 1/3 of those of the commercial frequency transformer. The smoothing capacitor may have a capacity of about 1/10. As a result of further miniaturization, the transformer can be mounted on the printed circuit board, so that the wiring work can be simplified.

Further, since the inverter and the peripheral circuit for controlling the operation of the inverter are integrally formed into a monolithic IC and the fan motor incorporated in the motor is used, the power supply for driving the fan motor can be one power supply.
The power supply circuit can be downsized.

Since the switching circuit has a feedback function, the output voltage can be stabilized.

Further, in the present invention, the DC power on the primary side of the power supply is obtained from the output of the converter circuit for the fan motor, and there is no need to provide a circuit for extracting the DC power, so that the circuit configuration is simple. You can

[Brief description of drawings]

FIG. 1 is a circuit diagram of a fan motor drive circuit according to an embodiment.

FIG. 2 is a circuit diagram of a switching power supply according to an example.

FIG. 3 is a circuit diagram of a converter according to another embodiment.

FIG. 4 is a circuit diagram of a fan motor drive circuit according to a conventional example.

FIG. 5 is a circuit diagram of an inverter drive power supply circuit according to a conventional example.

[Explanation of symbols]

 1 Motor 2 Inverter 3 Duty Control Circuit 4 Switching Circuit 5 Step-Down Chopper Circuit 6 Converter Circuit 7 High Frequency Transformer 8 Switching Circuit 9 External Power Supply 10 Control Power Supply 11 Switching Power Supply 12 Controller 13 Level Shift Circuit 14 Converter Circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Iizuka 800 Tomita, Ohira-cho, Shimotsuga-gun, Tochigi Prefecture Living Equipment Division, Hitachi, Ltd.

Claims (2)

[Claims] 1. A fan motor having a built-in inverter,
A control unit that controls each part of the air conditioner including the rotation speed control of the fan motor, a converter circuit that converts an AC input into a DC output, and the output of the converter circuit is stepped down according to a command from the control unit, In a fan motor drive circuit for an air conditioner, which comprises a step-down chopper circuit for supplying power to the fan motor, and a power supply circuit for supplying power to the inverter and the control unit and the step-down chopper circuit, wherein the power supply circuit is one of the converter circuit outputs. A high frequency transformer having a primary winding connected to the high potential side and a plurality of secondary windings, an emitter and a collector are connected in series to the primary winding of the high frequency transformer, and a base serves as a high frequency switching signal source. A switching circuit that is connected and conducts high frequency electricity to the primary winding of the high frequency transformer, and a secondary winding of the high frequency transformer. The first rectifying / smoothing circuit, which is connected to any one of the secondary windings and supplies the rectified and smoothed output to the inverter and the step-down chopper circuit, and the other one of the secondary windings. A fan motor drive circuit for an air conditioner, comprising a second rectifying / smoothing circuit connected to the control unit and supplying the rectified and smoothed output to the control unit. 2. The switching circuit according to claim 1, wherein the converter circuit includes a switching converter that converts an AC input into a DC output and then outputs an input voltage of 1 / n (n is a number of 1 or more). A fan motor drive circuit for a characteristic air conditioner.