JP2007127384A - Refrigerator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerator composed by mounting a power supply capable of further flexibly restraining a rush current in lighting an in-refrigerator lamp. <P>SOLUTION: A control circuit 16 regulates the value of a voltage applied to a xenon lamp 9 from a switching power supply 15 by applying a PWM signal to the gate of an FET 19 to PWM-control its turning-on/off. When the xenon lamp 9 is lit, the control circuit 16 gradually raises the application voltage by gradually increasing the duty of the PWM signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a refrigerator provided with an interior lamp driven by a DC power source.

The refrigerator is provided with an interior lamp that turns on and off according to the open / closed state of the door and functions as interior lighting. Many of these interior lamps are driven by an AC power source, but some refrigerators are equipped with interior lamps using a DC power source such as a xenon lamp or LED. This DC power source is a switching power source. Often generated by a circuit.
Patent Document 1 discloses a switching power supply, an interior light drive circuit for turning on / off the interior light by a transistor using the switching power supply as a power supply source, and opening / closing of a refrigerator door, and the interior light drive circuit And a control circuit for controlling the on / off of the transistor via the inside of the refrigerator.
Japanese Patent Laid-Open No. 2001-210480

  However, when driving an interior lamp with a switching power supply, especially when driving a lamp that requires a large current such as a xenon lamp, a sudden load fluctuation occurs when the interior lamp is turned on / off, so the switching power supply May not oscillate stably and may affect the operation of the entire refrigerator system. In particular, since the resistance value of the lamp used for the interior lamp is smaller than when the power is energized when not energized, a large inrush current flows at the time of lighting, that is, immediately after the voltage is applied to the interior lamp. .

In order to reduce such inrush current, a current limiting resistor may be inserted in series in the power supply line to the interior lamp. However, this measure has a problem in that power consumption increases because a current always flows through the current limiting resistor when the interior lamp is lit.
Moreover, the interior lamp driving device of Patent Document 1 includes a zener diode inserted between the base of the driving transistor and the ground in the interior lamp drive circuit, so that the base of the transistor is instantly turned on. The voltage applied to is limited by a Zener voltage so as to suppress an inrush current flowing through the transistor. However, with this configuration, the current value to be limited cannot be set flexibly.

  This invention is made | formed in view of the said situation, The objective is to provide the refrigerator which can control and suppress the inrush current at the time of lighting of the interior lamp driven by DC power supply more flexibly. is there.

  In order to achieve the above-described object, a refrigerator according to the present invention includes a semiconductor switching element inserted between the DC power source and the interior lamp in a refrigerator including an interior lamp driven by a DC power source, A PWM drive circuit for controlling a voltage applied to the interior lamp by outputting a PWM signal for turning on and off the semiconductor switching element, and when the interior lamp is turned on, the duty of the PWM signal is gradually increased. Thus, the voltage applied to the internal lamp is gradually increased.

  The inrush current generated when the interior lamp is turned on increases in proportion to the voltage applied to the interior lamp. Therefore, when turning on the interior lamp, the duty of the PWM signal is gradually increased to control on / off of the semiconductor switching element, and the voltage applied to the interior lamp from the DC power source through the semiconductor switching element is gradually increased. Increase to suppress inrush current.

  According to the refrigerator of the present invention, when the interior lamp driven by the DC power source is turned on, the applied voltage is gradually increased, so that a large inrush current can be prevented from flowing. Moreover, it becomes possible to flexibly change the level for limiting the inrush current only by changing the duty of the PWM signal.

  An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a front view with the refrigerator door omitted. As shown in FIG. 2, the refrigerator main body 1 couple | bonds the outer box 2 made from a steel plate, and the inner box 3 made from plastic, and the heat insulating material (not shown) which consists of urethane foam etc. in the space between them is shown. It is configured as a heat-insulated box filled with foam. In the refrigerator body 1, a plurality of storage rooms, in this embodiment, a refrigeration room 4, a vegetable room 5, a switching room 6 arranged in the left and right, an ice making room 7, and a freezing room 8 are provided in this order.

  Further, a shade (not shown) for covering the interior lamp is disposed near the ceiling inside the refrigerator compartment 4, and a xenon lamp (reference numeral 9 in FIG. Are attached). A hinged open / close heat insulating door (not shown) is provided in front of the refrigerator compartment 4. Further, for example, a door opening / closing detection switch (shown with reference numeral 10 in FIG. 1) for detecting opening / closing of the door is disposed at a contact portion between the refrigerator 4 and the door. In addition, an operation panel (not shown) on which a plurality of input switches for a user to make various settings is provided on the door surface.

  Next, the lighting circuit for the interior lamp will be described with reference to FIG. FIG. 1 shows a configuration of an interior lamp lighting circuit of a refrigerator. A plug 11 connected to a power outlet of an AC power supply is connected to a DC power supply circuit 14 having a full-wave rectifier circuit 12 and a smoothing capacitor 13, and switching is performed on the output side of the DC power supply circuit 14. A power supply circuit 15 (corresponding to a DC power supply) is connected. The switching power supply circuit 15 is a power supply circuit that generates power for operation of each circuit (load) 17 including a power supply for driving the interior lamp and a control circuit 16 (corresponding to a PWM drive circuit) configured by a microcomputer. Each circuit 17 is connected to the output terminal via power buses 31a and 31b.

The interior lamp drive circuit 18 includes a control circuit 16, a P-channel MOSFET 19 (corresponding to a semiconductor switching element), a flywheel diode 20, a coil 21, and a capacitor 22. The FET 19 has a source connected to the power bus 31 a and a drain connected to the power bus 31 b via the coil 21 and the xenon lamp 9.
The flywheel diode 20 is connected in the reverse direction between the drain of the FET 19 and the power supply bus 31b. The smoothing capacitor 22 is connected between the common connection point of the coil 21 and the xenon lamp 9 and the power supply bus 31b.

  A PWM (Pulse Width Modulation) signal output from the control circuit 16 is given to the gate of the FET 19, and on / off of the signal is PWM controlled by the control circuit 16. Therefore, the magnitude of the voltage applied to the xenon lamp 9 is adjusted by varying the duty of the PWM signal applied to the gate of the FET 19. That is, when the duty of the PWM signal is increased, the applied voltage is increased, and when the duty of the PWM signal is decreased, the applied voltage is decreased.

  In addition, an operation switch 23 and a door open / close detection switch 10 for adjusting the brightness of the interior lamp are connected to the control circuit 16. The operation switch 23 is composed of, for example, a variable resistor, and is provided on the operation panel described above. When the user operates the operation switch 23 to adjust the illuminance of the interior lamp, the operation switch 23 outputs a signal having a level corresponding to the operation amount. The control circuit 16 is configured to control the PWM duty when the xenon lamp 9 is lit according to the operation amount of the operation switch 23.

  On the other hand, the door opening / closing detection switch 10 outputs a signal whose level changes according to the opening / closing of the door to the control circuit 16. The control circuit 16 performs PWM control on the voltage applied to the xenon lamp 9 even when the xenon lamp 9 is turned on or off according to this signal. The carrier frequency for PWM control is set to about 32 kHz, for example.

Next, the operation of this embodiment will be described with reference to FIGS. FIG. 3 is a flowchart showing the control contents when the control circuit 16 turns on and off the xenon lamp 9 according to the open / closed state of the door of the refrigerator compartment 4.
First, when the door of the refrigerator compartment 4 is opened by the user, the door opening / closing detection switch 10 changes the signal output to the control circuit 16 to a level indicating door opening. Then, the control circuit 16 determines that the door has been opened due to the change in the signal level (step S1: “YES”).
And the control circuit 16 confirms the signal level of the operation switch 23 which shows the illumination intensity of the interior lamp preset by the user (step S2). Then, the duty of the PWM signal output to the FET 19 is gradually increased from 0%, and the xenon lamp 9 is turned on, and finally turned on with the illuminance set by the user (step S3).

  FIG. 5 is a diagram showing the relationship between the applied voltage and the applied current when the interior lamp is lit by the conventional method. Conventionally, since the interior lamp of the refrigerator is lit by applying a driving voltage immediately after the door is opened, the applied voltage to the xenon lamp 9 increases rapidly as the door is opened as shown in FIG. %become. In this case, the peak value of the current flowing through the xenon lamp 9 at the time of lighting is about 1.5 A even when a current limiting resistor is inserted in series, which is about 1 compared with the normal time (about 0.8 A). A so-called inrush current of 9 times was flowing.

  In contrast, in this embodiment, when the xenon lamp 9 is turned on, as shown in FIG. 4, the applied voltage is gradually increased by PWM control, and after 0.5 seconds, the PWM duty, that is, the applied voltage is 100% ( The xenon lamp 9 is slowly turned on so as to reach the maximum illuminance setting by the user. Therefore, the peak value of the current flowing through the xenon lamp 9 at the time of lighting is about 1 A, which is suppressed to about 1.2 times the current flowing at the normal time (about 0.8 A), and an excessive inrush current does not flow.

If the door is closed from the state where the xenon lamp 9 is lit, that is, the door is opened, the signal output from the door opening / closing detection switch 10 to the control circuit 16 is changed to a level indicating the door closing. Then, the control circuit 16 determines that the door is closed (step S4: “YES”), turns off the xenon lamp 9 (step S5), and returns to step S1.
However, if the user forgets to close the door or if the door is not fully closed but is in a so-called half-open state, the signal level output from the door open / close detection switch 10 does not change. Therefore, in this embodiment, when a predetermined time, for example, 3 minutes elapses without detecting "door closed" by the control circuit 16 (step S4: "NO", step S6: "YES"), the output is made to the FET 19. The duty of the PWM signal to be reduced is gradually reduced, and the voltage applied to the xenon lamp 9 is reduced to 50% (step S7). That is, the xenon lamp 9 is turned on with an illuminance lower than the illuminance set by the user. In this case, the PWM duty is reduced at a rate of 20% / second, for example.

Next, when the xenon lamp 9 remains on as described above and the door is open for 10 minutes, for example (step S8: “NO”, step S9: “YES”), the same as step S7. The PWM duty is gradually reduced to turn off the xenon lamp 9 (step S10). Even after the xenon lamp 9 is turned off, the control circuit 16 continues to monitor the signal level from the door opening / closing detection switch 10 (step S11), and when the signal level changes (step S11: “YES”). Determines that the door is closed and returns to step S1.
If the signal level from the door open / close detection switch 10 changes to the closed side before 10 minutes have passed while the applied voltage is 50% and the xenon lamp 9 is lit (step S8: “YES”). ), The control circuit 16 determines that the door is closed, and turns off the xenon lamp 9 at that time (step S5).

As described above, according to this embodiment, when the door of the refrigerator compartment 4 is opened and the xenon lamp 9 is turned on, the control circuit 16 gradually increases the duty of the PWM signal output to the FET 19 to thereby increase the xenon lamp. The voltage applied to 9 was gradually increased. Therefore, the inrush current at the time of lighting can be suppressed.
Then, by gradually increasing the applied voltage at the time of lighting as described above, the xenon lamp 9 comes on slowly when the door is opened, and has a visual effect that lights up softer than before, A high-class feeling can be given to the user.
Further, since the value of the current flowing through the xenon lamp 9 can be controlled simply by changing the duty of the PWM signal output from the control circuit 16, it is possible to limit the inrush current at the time of lighting more flexibly.

Furthermore, even if the door is left open for a long time, the illuminance of the xenon lamp 9 is reduced after 3 minutes and the xenon lamp 9 is completely turned off after 10 minutes. Even if the door is left open, the heat generation of the xenon lamp 9 and the interior lamp drive circuit 18 can be suppressed to prevent the peripheral components from rising in temperature. Therefore, it is possible to prevent deterioration of peripheral parts including the xenon lamp 9 and the shade.
Here, in the conventional interior light control, when a certain time, for example, 5 minutes elapses with the interior light turned on with the door open, the interior light is turned off because it is necessary to suppress the temperature rise of peripheral components. I was trying to let them. On the other hand, in the present embodiment, as described above, the xenon lamp 9 is turned off after the stage of reducing the illuminance of the xenon lamp 9 and turning on the lamp with the heat generation suppressed to some extent. Therefore, the interior lamp can be lit longer than the conventional method.

  In addition, since the control circuit 16 changes the illuminance of the xenon lamp 9 in accordance with a signal given from the operation switch 23, the user operates the operation switch 23 in advance to set the interior lamp to a desired brightness. Can be adjusted. Therefore, for example, if the brightness of the interior lighting of the refrigerator does not match the interior image because the interior lighting uses a lot of downlights or indirect lighting, etc., change the illumination intensity of the interior lighting. can do.

  Further, when the illuminance of the xenon lamp 9 is reduced, the control circuit 16 gradually decreases the duty of the PWM signal output to the FET 19 so that the voltage applied to the xenon lamp 9 is gradually reduced. The lamp 9 gets dark slowly. Therefore, it does not give the user a sense of incongruity that the interior lamp suddenly becomes dark, and it does not give the user the misunderstanding that the light bulb has been burned out.

The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following modifications or expansions are possible.
The duty of the PWM signal output from the control circuit 16 to the FET 19 may be a preset value, or a separate feedback circuit is provided to monitor the voltage applied to the xenon lamp 9, and the PWM is determined according to the value. You may make it adjust the duty of a signal.
Further, the process of increasing the voltage applied when the xenon lamp 9 is turned on is not limited to a straight line as shown in FIG. 4, and may be increased in a stepped shape or a curved shape as long as the inrush current can be suppressed. .

  The control circuit 16 is configured to change the illuminance of the xenon lamp 9 in accordance with a signal given from the operation switch 23. However, the illuminance pattern data is stored in the control circuit 16 in advance, and is transmitted to the user. It is also possible to change the illuminance so that it is selected. In this case, a non-volatile memory such as an EEPROM may be provided to store the illuminance pattern data. Moreover, what is necessary is just to provide the structure which a user can set illumination intensity as needed.

  In this embodiment, when 3 minutes have passed with the door opened (step S6: “YES”), the voltage applied to the xenon lamp 9 is reduced, and when 10 minutes have passed (step S8: “ YES ”), the xenon lamp 9 is turned off, but depending on the distance between the xenon lamp 9 and peripheral components, the specifications of the semiconductor elements used in the interior lamp driving circuit 18, etc., these steps S6 and S8 The elapsed time for making the determination may be changed. Further, in this case, if the maximum lighting time of the xenon lamp 9 is shortened, the heat generation of the xenon lamp 9 itself can be suppressed accordingly, so that the distance between the xenon lamp 9 and peripheral components can be made closer. It is possible to increase the internal volume.

  In step S7, the applied voltage is uniformly reduced to 50% after a predetermined time has elapsed with the xenon lamp 9 turned on, but the applied voltage is not limited to 50%. Further, the applied voltage may be automatically changed based on conditions such as heat generation of the xenon lamp 9, temperature rise of peripheral components, and internal temperature. Further, when reducing the illuminance, it is not always necessary to gradually decrease the PWM duty. Furthermore, the control when the open state continues may be performed as necessary.

  In the interior lamp drive circuit 18, the semiconductor switching element is configured using a P-channel MOSFET, but may be configured using an N-channel MOSFET or a bipolar transistor. Further, the DC power supply is not limited to the switching power supply circuit, and may be configured by a combination of a transformer and a regulator. Further, the PWM drive circuit may be configured only by hardware without using the control circuit 16 configured by a microcomputer.

The figure which is one Example of this invention and shows the structure of the interior lamp lighting circuit of a refrigerator Front view with refrigerator door omitted The flowchart which shows the control content of the control circuit at the time of turning on and off the interior lamp according to opening and closing of the door The figure which shows the relationship between the applied voltage and the applied current when the interior lamp is lit FIG. 4 equivalent diagram showing the prior art

Explanation of symbols

  In the drawing, 9 is a xenon lamp (inside lamp), 15 is a switching power supply circuit (DC power supply), 16 is a control circuit (PWM drive circuit), and 19 is a P-channel MOSFET (semiconductor switching element).

Claims (3)

In a refrigerator equipped with an interior lamp driven by a DC power source,
A semiconductor switching element inserted between the DC power source and the interior lamp;
A PWM drive circuit for controlling a voltage applied to the interior lamp by outputting a PWM signal for turning on and off the semiconductor switching element;
When turning on the interior lamp, the voltage applied to the interior lamp is gradually increased by gradually increasing the duty of the PWM signal.   2. The refrigerator according to claim 1, wherein when a predetermined time elapses with the interior lamp lit, the applied voltage is reduced to a predetermined level. 3. The refrigerator according to claim 2, wherein when the applied voltage is lowered, the duty of the PWM signal is gradually reduced by gradually reducing the duty of the PWM signal.

Images