KR940004893B1 - Electric rice cooker - Google Patents

Abstract

The heating power compensation circuit and method of an electric rice cooker comprises a power level detector for detecting a level of an input power source, a microprocessor for controlling the whole operation of the electric rice cooker, a 110V/220V changeover portion, a heater driver for supplying and cutting off an alternating current power source, and a bias supplier for supplying a bias power source to the 110/220V changeover portion and the heater driver, thereby compensating a variation in heating power caused by a voltage variation.

Description

Thermal Compensation Circuit and Method of Electric Rice Cooker

1 is a thermal compensation circuit diagram of an electric rice cooker to which the present invention is applied.

2 is a control flowchart showing a thermal power compensation method of the present invention.

* Explanation of symbols for the main parts of the drawings

1: power level detection unit 2: microcomputer

3: 110v / 220v switching unit 4: Heater driving unit

5: bias supply

The present invention relates to a thermal compensation circuit and a method of an electric rice cooker to adjust the on / off time of the heater according to the variation of the commercial power source so that the thermal power is constant regardless of the input voltage variation.

In general, commercial power supply varies slightly depending on the usage area and time, and changes to 110V.

In general, the commercial power supply varies slightly depending on the region of use or the time of use. In the case of 110V, it varies from 85V to 132V, and in the case of 220V, it varies from 187V to 235V.

However, various electric appliances including rice cooker can perform 110V / 220V automatic switching function by distinguishing 110V or 220V when receiving commercial power, but compensation for voltage fluctuation is not made because local voltage fluctuation is ignored. I couldn't.

For this reason, in the case of the electric rice cooker, a lower or higher voltage than the rated voltage (110V, 220V) is applied to the heater, thereby causing a problem in that the heating power of the heater is changed and the rice taste cannot be properly produced.

In other words, when cooking rice, the thermal power and heating time are important, but when the commercial power is lower than the rated voltage of the heater, the thermal power is weakened, and when it is higher than the rated voltage, the thermal power becomes stronger, so that the set thermal power cannot be maintained. You lose.

Accordingly, it is an object of the present invention to provide a thermal compensation circuit and a method of an electric rice cooker which can compensate for thermal fluctuations caused by voltage fluctuations by detecting a change amount of a commercial power source and adjusting a heating time accordingly.

It is another object of the present invention to provide a thermal compensation circuit and a method of an electric rice cooker to improve the taste of rice by appropriately controlling the thermal power regardless of the fluctuation of the input power source.

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

FIG. 1 is a thermal compensation circuit diagram of an electric rice cooker to which the present invention is applied. As shown therein, a power level detection unit 1 detects a level of an input power supply by lowering and smoothing an AC power input through a power cord PC. And a microcomputer 2 for controlling the overall operation of the rice cooker by outputting a signal for controlling 110V / 220V switching and a heater on / off time according to the output level of the power level detector 1, and the microcomputer 2 110V / 220V switching unit 3 for switching AC power to the 220V terminal or the 110V terminal of the primary side of the power transformer T1, and is switched according to the control signal of the microcomputer 2 A heater driver 4 for supplying and cutting off AC power to the heaters H1-H3, and lowering the input AC power to a constant voltage to bias the 110V / 220V switching unit 3 and the heater driver 4. Such as a bias supply part 5 for supplying power Consists of

Here, reference numeral C1, which has not been described, is a noise removing capacitor, TNR is a surge current removing varistor, and REG is a smoothing level of the power level detection unit 1 to supply operating power to the maincom 2. Is a regulator.

Referring to the operation and effects of the thermal compensation circuit of the electric rice cooker configured as described above in detail as follows.

First, the power level detection unit 1 detects the level of the AC power input through the power cord PC, where the power level detection unit 1 includes a transformer T1 for dropping the input AC power and the transformer. A diode D1-D3 for full-wave rectifying the AC power dropped by T1, a capacitor C2 for peace of the power rectified by the diodes D1-D3, and a smoothing of the capacitor C2. It consists of resistors R1 and R2 which divide the DC voltage and input them to the terminals A / D of the microcomputer 2.

When the AC power is input as shown in Table 1 below, the power level detecting unit 1 configured as described above drops the input power through the transformer T1 and performs full-wave rectification with the diodes D1-D3. The rectified power is smoothed by a capacitor C2 to make a DC voltage of a predetermined level, divided by resistors R1 and R2, and applied to the microcomputer 2, whereby the microcomputer 2 inputs the input voltage. Search for and determine whether it is higher or lower than rated voltage and compensates for the difference when driving load.

TABLE 1

That is, the microcomputer 2 recognizes the input voltage according to Table 1 above, and outputs a 110V / 220V switching control signal according to the recognition result.

In response to the voltage switching control signal of the microcomputer 2, the 110V / 220V switching unit 3 switches a voltage by controlling a relay, where the 110V / 220V switching unit 3 is a terminal of the microcomputer 2 ( Resistor R3 connected to Q1), transistor TR1 turned on and off under the control of the microcomputer 2, resistor R4 connected between the base and emitter of transistor TR1, and transistor TR1. And a relay RL1 for switching the input path of the AC power supply and the relay RL1 protection diode D4.

The 110V / 220V switching unit 3 configured as described above outputs a low potential signal through the terminal Q1 of the microcomputer 2 when the AC power input is 110V when the relay RL1 switch is connected to the 220V terminal. Therefore, the transistor TR1 is turned on by this signal, and the relay RL1 is driven so that the relay RL1 switch is switched to the 110V terminal of the transformer T1.

Similarly, if 220V is input while the relay RL1 switch is connected to the 220V terminal, a high potential signal is output through the terminal Q1 of the microcomputer 2 so that the transistor TR1 is turned off to drive the relay RL1. Since the relay RL1 is not driven, the relay RL1 maintains the connection to the 220V terminal of the transformer T1.

The heater driver 4 is controlled to drive the heaters H1-H3 under the control of the microcomputer 2, where the heater driver 4 is the terminals Q2-Q4 of the microcomputer 2. Resistors R5-R7 connected to the transistors, transistors TR2-TR4 turned on and off according to the control signal of the microcomputer 2, and resistors R8-R10 connected to the transistors TR2-TR4, respectively. And a relay RL2 RL3 and a triac TRI1 which operate according to the switching state of the transistors TR2-TR4 to supply and cut off AC power to the cooking heaters H1 and H2 and the warming heater H3. ) And relays RL2 and RL3 for protection diodes D5 and D6.

The heater driving unit 4 configured as described above operates the heaters H1-H3 differently in the cooking mode and the warming mode. When 110V is input in the cooking mode, the terminal Q3 (Q4) of the microcomputer 2 is provided. Since the low potential signal is output from the terminal and the high potential signal is output from the terminal Q2, only the transistor TR2 is turned on. Accordingly, the relay RL2 is driven to connect the relay RL2 switch.

According to the connection of the relay RL2 switch, the 110V cooking heater H1 generates heat, and the other transistors RL3 and RL4 are turned off, so that the relay RL3 switch and the triac TRI1 are turned off to 220V. The cooking heater H2 and the warming heater H3 do not generate heat.

In the warm mode, since the high potential signal is output through the terminals Q2-Q4 of the microcomputer 2, the transistors TR2 and TR3 are turned off and only the transistor TR4 is turned on.

When the transistors TR2 and TR3 are turned off, the relays RL2 and RL3 are not driven so that the switches are all turned off, and triac TRI1 is turned on by the conduction of the transistor TR4. Since the power flows to the conductive triac TRI1, the warming heater H3 and the 220V cooking heater H2 connected thereto generate heat.

At this time, the heat generation amount of the heaters H1-H3 is controlled by the input signal and the control signal of the microcomputer 2, and when the on / off time of the transistors TR2-TR4 is changed by the control signal, the heaters H1-H3. Since the thermal power can be adjusted, the thermal power of the heater (H2) (H3) will be able to weaken.

The bias supply unit 5 drops the AC power input to supply the bias power to the 110V / 220V switching unit 3 and the heater driving unit 4, wherein the bias supply unit 5 supplies the input AC power. The capacitor C3 and the resistor R11 to drop, the diodes D7 and D8 to rectify the dropped power supply, and the zener diode ZD1-ZD3 to make the rectified power to the constant voltage of the relay RL1-RL3 drive level. ) And a smoothing capacitor (C4), the power of the level of the sum of the Zener voltages of the Zener diodes (ZD1-ZD3) is output and biased to the 110V / 220V switching unit (3) and the heater driver (4). Is supplied.

On the other hand, Figure 2 is a control flow diagram showing a thermal power compensation method performed by the microcomputer (2), which will be described in detail as follows.

When the power is turned on, the microcomputer 2 reads the current commercial power level input from the power level detection unit 11 through the input port A / D (step 11), and the value is stored in the register A. After storing, it is determined in step 12 whether the value of the register A is a constant value, for example, 2.5V or more.

If the value of the register A is less than 2.5V, 110V is recognized as input and outputs a low potential signal through the output terminal Q1 (step 13), and 220V if the value of the register A is 2.5V or more. Recognizes as input and outputs a high potential signal through the output terminal Q1 to perform the 110V / 220V switching function (step 14).

Next, while the cooking key is pressed (step 15), it is determined how many values are stored in the register A to determine the commercial power level (step 16), and the compensation data corresponding to the current commercial power level is preliminarily. From the stored data, a control signal for adjusting the on / off time of the heaters H1-H3 is output through the terminals Q2 to Q4 (step 17).

That is, when the commercial power source is changed while the on / off time of the heaters H1 to H3 is fixed by the program of the microcomputer 2, the heat generation amount of the heaters H1 to H3 is changed. The on / off time of the transistors TR2 to TR4 is varied in accordance with the amount of change in the commercial power source so that the amount of heat generated is equal to that of the rated voltage.

As described above, the present invention compensates the thermal power fluctuations due to the change in the commercial power source, thereby obtaining the desired thermal power, thereby improving the taste of the rice, and eliminating the performance deterioration caused by the voltage fluctuation.

Claims (6)

110V / 220V switching and heater on depending on the output level of the power supply level detector 1 for detecting the level of the input power supply by dropping and smoothing the AC power inputted through the power cord PC. Microcomputer 2 for controlling the overall operation of the rice cooker by outputting a signal for adjusting the on / off time, and is switched according to the control signal of the microcomputer (2) 220V terminal or 110V terminal of the primary side of the power transformer (T1) A 110V / 220V switching unit 3 for inputting AC power, a heater driving unit 4 for switching AC power to the heaters H1-H3 and switching the switch according to the control signal of the microcomputer 2, Thermal compensation circuit of an electric rice cooker comprising a bias supply part 5 for supplying a bias power to the 110V / 220V switching part 3 and the heater driving part 4 by making the input AC power into a constant voltage after a falling time. . 2. The power supply level detecting unit (1) according to claim 1, wherein the power supply level detecting unit (1) includes a transformer (T1) for dropping the input AC power, a diode (D1 to D3) for full-wave rectifying the power dropped by the transformer (T1), and the diode. A capacitor (C2) for smoothing the power rectified by (D1-D3), and a resistor (R1) (R2) for dividing the power smoothed by the capacitor (C2) and inputting it to the microcomputer (2). Compensation circuit of electric rice cooker. 2. The heater driving unit (4) according to claim 1, wherein the heater driving unit (4) includes a resistor (R5 to R7) connected to an output terminal of the microcomputer (2), and transistors (TR to TR4) turned on and off according to a control signal of the microcomputer (2). And the resistors R8 to R10 connected to the transistors TR2 to TR4 and the switching states of the transistors TR2 to TR4, respectively, to operate the AC power supply to the cooking heaters H1, H2 and the warming heater H3. And a relay (RL2) (RL3) and a triac (TRI1) for supplying and interrupting the circuit, and the relay (RL2) (RL3) protection diode (D5) and a thermal compensation circuit of an electric rice cooker, characterized in that it is configured. 4. The bias supply unit (5) according to claim 1, wherein the bias supply unit (5) includes: a capacitor (C3) and a resistor (R11) for dropping the input AC power, and a diode for rectifying the power dropped by the capacitor (C3) and a resistor (R11) ( D7) (D8), Zener diodes (ZD1 to ZD3) which make the power rectified by the diodes (D7) and (D8) the constant voltage of the relay (RL1 to RL3) drive levels, and a smoothing capacitor (C4). Thermal compensation circuit of electric rice cooker. Comparing the current commercial power level detected when the power is turned on with a preset 110V / 220V division level level, determining whether 110V or 220V is performed according to the comparison result, and performing a 110V / 220V switching function; Determining the level by comparing the detected current commercial power level with a preset reference value, extracting compensation data according to the determination result from the set compensation data table, and turning on / off the heater so that the heating value is equal to the rated voltage. Firepower compensation method of an electric rice cooker characterized in that the step consisting of adjusting the off time. The method of claim 5, wherein in the baud mode, determining the level by comparing the detected current commercial power level with a preset reference value, and extracting compensation data according to the determination result from the set compensation data table to determine a heat generation amount. The power compensation method of the electric rice cooker characterized in that it further comprises the step of adjusting the on / off time of the heater to be equal to the voltage.