KR19990022303U - Refrigerator fan motor control circuit - Google Patents

Abstract

Disclosed is a fan motor control circuit of a refrigerator capable of improving a return time delay of a motor by preventing a delay of a current drop time when a transistor is switched off in a brushless fan motor driving circuit. The fan motor control circuit of the refrigerator includes a transistor which is switched on when a control signal is applied from a microcomputer, a brushless fan motor driven by receiving power from a driving power source as the transistor is switched on, and a brushless fan motor. A diode contacted in parallel and a zener diode attached in reverse series to the cathode terminal of the diode are provided. Therefore, it is possible to prevent malfunction caused by improving the return time delay of the motor when the brushless fan motor is driven off.

Description

Fan motor control circuit of refrigerator.

The present invention relates to a fan motor control circuit of a refrigerator. In particular, in a brushless fan motor driving circuit, a fan motor control of a refrigerator to improve the return time delay of a fan motor by reducing a drop delay time of a current when a transistor is switched off. It is about a circuit.

Referring to FIG. 1, a control circuit of a general fan motor includes a temperature control switch 80 at a power supply (AC) side and a timer 90 connected at a rear end thereof to a compressor circuit (overload protection) at a terminal T4 of the timer. Connect the device 140, the compressor 130, the starter 120 and the fan motor circuit (fan motor 70, the freezing door switch 50, the refrigerator door switch 40), the refrigerator door switch 40 The power supply AC is connected to the internal lamp 60 or the fan motor circuit to be selectively applied. The terminal T2 of the timer 90 has a defrost control switch 150, a defrost heater 100, and a temperature fuse (). The power source AC is applied through the 110.

At this time, the cam and the terminal operating portion of the timer 90 are composed of a cam (not shown) that is rotated by the timer driving motor 91 and terminals T2 to T4 that are in cross contact with each other by the shape of the cam.

Therefore, when the switching terminals T3 and T4 of the timer 90 are at any position in the compressor operating section of the cam, the contacts of the terminals T3 and T4 are brought into contact with each other so that the terminals T3 and T4 of the timer 90 are in contact. Since the state is connected to the on / off of the temperature control switch 80, the compressor 130 driving circuit and the fan motor 70 driving circuit unit is operated.

On the other hand, when the terminal T4 enters the defrost section of the cam, the terminal T3 is separated from the terminal T4 and comes into contact with the contact point of the terminal T2. Thus, in the circuit diagram, the contacts T3 and T2 of the timer 90 Since the power source AC flows from the contact point T3 to the contact point T2 and the defrost control switch 150, the time driving motor 91 stops operation and the defrost heater 100 generates heat to start defrosting.

Then, when the ambient temperature is increased due to the heating of the defrost heater 100 and the set temperature value of the defrost control switch 150 is greater than the defrost control switch 150 is turned off, the timer drive motor 91 operates and the cam rotates accordingly. In this case, the compressor 130 and the fan motor 70 are operated because the terminals T2 to T3 are separated from each other and the terminals T3 to T4 are contacted.

The driving of the conventional fan motor (Cooling FAN) is driven at a constant speed by using an AC power source (AC) by controlling the fan motor in conjunction with the drive of the compressor on / off.

By the way, the driving of the fan motor by such a switch is relatively high in efficiency and suitable for controlling the speed and position, but has a mechanical switch mechanism called a brush and a commutator.

That is, since the brush and the commutator are frictionally contacted at a high speed, the brush is worn and graphite or metal powder is generated, thereby causing an electrical obstacle.

In order to solve this problem, referring to FIG. 2, a brushless motor (BLDC) is used, which is also referred to as a commutatorless motor, and is similar to a brush of a DC motor. It is a motor that replaces a commutator with a transistor or a silicon controlled rectifier (SCR).

The microcomputer 1 applies a drive signal through the transistor 2 of the fan motor driving unit, and when the transistor 2 is switched on, the BLDC fan motor 3 receives power from the driving power source 4 (Vcc) and the fan is turned on. It will work.

The operation rate is controlled by applying a constant high voltage / low voltage to the BLDC fan motor 3 according to the value calculated through the PWM port of the microcomputer 1.

The operation of the BLDC cooling motor 3 is controlled in conjunction with the operation of the compressor to control the on / off of the fan motor. In response to the internal temperature of the refrigerator, two stages (1,800 rpm) or three stages (2,200 rpm) Cooling is performed by circulating cold air by turning the cooling fan on and off at a speed.

Therefore, the fan motor is controlled at high speed at the initial start-up or at the time of selection of the rapid refrigerating / freezing function, and generally two-stage control is performed to drive the fan motor at low speed.

When the transistor 2 is switched off, the diodes 5 contacted at both ends of the BLDC fan motor absorb surges due to the forward characteristics.

However, when the current flows through the coil of the BLDC motor and the current is suddenly cut off, that is, when the transistor is switched off, the counter electromotive phenomenon occurs in the direction of disturbing the change of the current in the coil, thereby generating a very high voltage.

Therefore, the diode connected in parallel to the BLDC motor absorbs the counter electromotive force generated when the transistor is switched off, but the coil current flowing through the BLDC fan motor coil continues to flow even during the occurrence of the surge, thereby delaying the interruption of the BLDC fan motor. There is a problem that delays the return time and causes a malfunction.

The present invention has been made to solve the above problems, in the BLDC fan motor driving circuit, to improve the delay time of the fan motor by blocking the current by using a Zener diode when switching off the transistor. There is this.

1 is a fan motor control circuit diagram of a conventional refrigerator freezer cold air circulation,

2 is a fan motor control circuit diagram using a conventional BLDC motor;

3 is a circuit diagram of a fan motor control circuit of a refrigerator according to the present invention;

Figure 4 is a graph of the return characteristics of the brushless fan motor according to the present invention.

<Description of Symbols for Main Parts of Drawings>

10 ... microcom 20 ... transistor

30 ... brushless fan motor 40 ... driven power

50 Diodes 60 Zener Diodes

A fan motor control circuit of the present invention refrigerator which achieves the above object comprises: a transistor switched on upon application of a control signal from a microcomputer; A brushless fan motor driven by receiving power from a driving power source as the transistor is switched on; A fan motor having a diode contacted in parallel at both ends of a brushless fan motor; A zener diode is attached to the cathode terminal of the diode in reverse series.

According to a feature of the present invention configured as described above, the fan motor control circuit of the refrigerator according to the present invention is a drive circuit of a BLDC fan motor, by switching off the current by using a Zener diode when switching off the transistor, the return of the fan motor The time delay can be improved.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The fan motor control circuit of the present invention refrigerator, with reference to Figure 3, the transistor 20 is switched on when the control signal is applied from the microcomputer 10; A brushless fan motor 30 driven by receiving power from a driving power source as the transistor 20 is switched on; Diodes 50 connected in parallel to both ends of the brushless fan motor 30; The zener diode 60 is attached to the cathode terminal of the diode 50 in reverse series.

In more detail, the transistor 20 in which the microcomputer 10 and the base terminal are in contact with the emitter ground is switched on when the driving control signal of the BLDC on / off port of the microcomputer 10 is applied to generate a predetermined driving signal. The brushless fan motor 30 is output to a brushless DC motor (BLDC), and the fan motor is driven by the driving power source Vcc.

When the microcomputer 10 controls the duty cycle of the output waveform and applies it to the transistor 20 having one end of the brushless fan motor 30 and the collector terminal contacted, the transistor 20 is switched on to brushless fan. By supplying the input current to the motor 30, the speed of the BLDC fan motor 30 can be automatically adjusted to approach the command value.

On the other hand, if the current flows through the coil of the brushless fan motor 30 and the current is interrupted, the counter electromotive phenomenon occurs in the direction of disturbing the change of the current in the coil to generate a high voltage.

Accordingly, the diode 50 contacted in parallel at both ends of the BLDC fan motor 30 and having the collector terminal of the transistor 20 and the anode contacted by the forward characteristic of the diode 20 when the transistor 20 is switched off. The coil absorbs back electromotive force.

The coil current continues to flow to the brushless fan motor 30 even during the occurrence of a surge, and a zener diode 60 is attached to the cathode terminal of the diode 50 in series with the zener breakdown. This prevents the delay of the current drop time.

Zener breakdown refers to a phenomenon in which when the reverse current of a pn junction is applied with a reverse voltage above a certain value, the zener effect rapidly increases and the operating resistance becomes almost zero. It is called.

The zener voltage of the zener diode 60 is preferably calculated as Vcc + 3V, which is higher than the driving power supply Vcc.

The return characteristics of the brushless fan motor calculated by the inventor's experiment are as shown in the graph of FIG.

Graph 1 shows that back electromotive force occurs when only the surge absorbing diode is attached and the zener diode is not attached, and current blocking continues until b time.

Graph 2 shows that if only the surge absorbing diode was attached, back EMF was absorbed, but current blocking continued until b time. (VF; diode forward voltage)

Graph 3 shows that when the surge absorbing diode and the zener diode are attached, the back EMF is absorbed by the diode and the current blocking is improved by the Zener diode until a time (Vz; Zener voltage of the Zener diode).

The fan motor control circuit of the refrigerator according to the present invention, in the drive circuit of the brushless fan motor, by attaching a zener diode to improve the current blocking performance when switching off the transistor to improve the delay time of the fan motor do.

Claims (1)

A transistor that is switched on when a control signal is applied from a microcomputer, a brushless fan motor driven by receiving power from a driving power source as the transistor is switched on, and a diode contacted in parallel between both ends of the brushless fan motor In one fan motor, And a zener diode attached to the cathode terminal of the diode in reverse series.