JPH0330281A - Induction heating cooker - Google Patents

Abstract

PURPOSE:To prevent an increase of the input power with a setting smaller than the large setting of a power control volume handle by deforming the output of a RC charge/discharge circuit in a PWM circuit so that the maximum pulse width of the on-pulse signal of a drive of switching elements does not exceed 1/2 of the oscillation cycle. CONSTITUTION:A waveform of a chopping wave output from a RC charge/ discharge circuit 11 is deformed so that the maximum pulse width of the on- pulse of a drive of switching elements 6, 7 output from a PWM circuit 13 does not exceed 1/2 of the oscillation cycle. Consequently, even if the output of a reference voltage setting circuit 12 going up and down in proportion to the sliding position of a power control volume handle as an input setting means 14 is dispersed higher than the set value at the time of setting for the large setting of the power control volume handle, the on-pulse width does not exceed 1/2 of the oscillation cycle. An inconvenience that the input power is increased with a setting smaller than the large setting of the power control volume handle is thus eliminated.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an induction heating cooker.

2. Description of the Related Art Conventionally, this type of induction heating cooker has a structure as shown in FIG.
1 has the circuit configuration as shown in FIG. The waveform was as shown in FIG. 9, and the relationship between the slide position of the power controller volume control 119 of the input setting section 114 and the input power was as shown in FIG.

That is, the switching element 105 in the inverter circuit 108 is driven by the triangular wave that is the output (Z) of the RC charge/discharge circuit 111 in the PWM circuit 113 and the input setting section 11.
Output (y) of the reference voltage setting circuit 112 that moves up and down in proportion to the slide position of the power conditioner volume knob 119 of No. 4.
The comparator circuit 110 compares the on-pulse with the output (Z) of the RC charging/discharging circuit 111 being lower than the output (ty) of the reference voltage setting circuit 112.
The waveform of the triangular wave which is the output (Z) of the Re charging/discharging circuit 111 was as shown in FIG. 7b.

Problems to be Solved by the Invention However, in an RC charging/discharging circuit with such a triangular wave output, in the case of an induction heating cooker with a half-pridge inverter circuit, the slide position of the power conditioner volume housing 119 is slightly smaller than the strong input setting. However, there was a problem in that the input power may become larger when the input setting is smaller.

In the case of an induction heating cooker with a half-pridge inverter circuit, the input power reaches its maximum value when the on-pulse width of the switching element 107 of the half-pridge inverter circuit 108 is 1/2 of the oscillation period, and this on-pulse width is the oscillation period. Since there is a property that the input power decreases when the cycle becomes larger than 1/2, even if the slide position of the power converter volume housing 119 is set to high, the output 2 of the Re charging/discharging circuit 111 and the reference voltage Even if the on-pulse width of the switching element 107 determined by the output y of the setting circuit 112 is designed to be 172 times the oscillation period, variations in the output 2 of the Re charging/discharging circuit 111 and the reference voltage setting circuit 11
Due to variations in the output y of the switching element, the on-pulse width of the switching element deviates by 1/2 of the oscillation period, and if the on-pulse width varies in the direction of widening, the above problem will occur. .

Therefore, even if the output of the reference voltage setting circuit fluctuates, the present invention maintains the pulse width of the on-pulse signal of the switching element at 1/2 of the oscillation period when the strong input is set, and increases the slide position of the power controller volume knob. The purpose is to prevent the input power from decreasing when it is moved toward the setting side.

Means for Solving the Problems and In order to achieve the above object, the present invention provides an RC charging method so that the maximum pulse width of the on-pulse of the drive of the switching element, which is the output of the PWM circuit, does not exceed 1/2 of the oscillation period. This modifies the waveform of the triangular wave that is the output of the discharge circuit.

Function The induction heating cooker of the present invention has the above-mentioned structure, so that the output of the reference voltage setting circuit, which goes up and down in proportion to the sliding position of the power controller volume knob, which is the input setting means, is adjusted to the level of the power controller volume knob. Even if the variation is higher than the designed value when the strong setting is made, the modified triangular wave that is the output of the RC charging/discharging circuit will reduce the maximum pulse width of the on-pulse of the switching element drive of the inverter circuit to 1/2 of the oscillation period.
The on-pulse width does not exceed 1/2 of the oscillation period. As a result, the inconvenience that the input power becomes larger when the power conditioner volume is set to a lower setting than a high setting is eliminated.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

In Figures 1 to 3, 1 is a DC power supply, 8 is a half bridge inverter circuit consisting of a resonant capacitor 2, a heating coil 3, diodes 4, 6, and switching elements 6, 7, and 9 is a switching element 6 and 7. 13 is a PWM circuit that determines the on-pulse width of each drive of the switching elements 6 and 7;
The WM circuit 13 includes an RC charging/discharging circuit 11 having an output with a triangular waveform modified so that the on-pulse width of the drive of the switching element 7 is not more than 1/2 of the oscillation period, and a power controller volume increaser of the input setting section 14. The output of the reference voltage setting circuit 12, which has a reference voltage output that increases and decreases in proportion to the slide position of the IO charging/discharging circuit 19, and the output of the RC charging/discharging circuit 11 and the reference voltage setting circuit 12 are compared, and the output of the IO charging/discharging circuit 11 is determined as the standard. The comparator circuit 1o has an output that generates an on-pulse signal for the switching element 7 when the voltage is smaller than the output of the voltage setting circuit 12, and generates an on-pulse signal for the switching element 6 during other periods.

To explain the circuit structure of the main parts of the RC charging/discharging circuit 11 and the waveforms of each part, the charging/discharging circuit consisting of a resistor 16, a capacitor 17, and a transistor 16 is controlled by an input a, which is the base of the transistor 16, , a terminal b for rapidly charging the capacitor 17 after 1/2 of the oscillation period from the moment the transistor 16 is turned on and the output 0 becomes Low is connected to the output C via the diode 18. Due to this terminal b, the output C of the RC charging/discharging circuit 119 becomes High instantaneously after 1/2 of the oscillation period from the moment when the transistor 16 is turned on and the output C becomes Low, and its waveform is shown in Figure 2b. It is a modified version of the triangular wave shown in .

1. FIG. 3 shows the state of the puff control volume knob 19 of the input setting section 14. When the puff control volume knob 19 is slid from the weak side to the strong side, the volume changes in proportion to the slide position. The output d of the reference voltage setting circuit 12 is designed to rise. For convenience of explanation, let us define the slide position of the power controller volume knob 19 as shown in Figure 3.

Next, the operation of the structure of this embodiment is shown in FIGS. 4 and 6.
This will be explained using figures.

This is the reference voltage setting circuit when the output C of the RC charging/discharging circuit 11 is as shown in 20 in FIG. When the output of 12 is in the state as shown in 21, the ON signal for driving the switching element 7 is 1/1 of the oscillation period as shown in 23.
2, and the relationship between the sliding position of the power controller volume knob 19 of the input setting section 14 and the input power is as shown by the solid line 24 in FIG.

Next, even if the output of the reference voltage setting circuit 12 fluctuates to a high level as shown in 22 (dotted line) when the power controller volume knob 19 of the input setting section 14 is set to high, the RC charging/discharging circuit 1
1's output C instantly goes High after 1/2 of the oscillation period from the moment the output C goes Low, as shown in waveform 20.
Therefore, the ON signal for driving the switching element 7 determined by the output 2o of the Re charging/discharging circuit 11 and the output 22 of the reference voltage setting circuit 12 is determined by the output of the reference voltage setting circuit 12 as shown in 23. When it is not set (when the output d of the reference voltage setting circuit 12 is 21), it is set to 1/2 of the oscillation period. 6
It will look like 26 (dotted line) in the figure. As a result, the input power when the strong input setting is set does not become smaller than the input power when the input setting is slightly smaller than the strong input setting.

゜Effects of the Invention As described above, the present invention provides an RC charging/discharging circuit in the PWM circuit so that the maximum pulse width of the on-pulse signal of the drive of the switching element, which is the output of the PWM circuit, does not exceed 1/2 of the oscillation period. Since this is a modified version of the triangular waveform that is the output of the puff component, it is possible to eliminate the inconvenience that the input power becomes larger when the setting is smaller than the strong setting of the puff component housing.

[Brief Description of the Drawings] Figure 1 is a schematic circuit block diagram of the induction cooking device of the present invention, and Figures 2a and b are schematic circuit diagrams of the RC charging and discharging circuit of the induction cooking device and waveforms of each part thereof. Figure 3 is a front view of the area around the power controller volume knob of the same induction heating cooker, Figure 4 is
The figure is an operation waveform diagram of the PWM circuit of the same induction heating cooker.
The figure is a graph of the input power versus the sliding position of the power control volume knob of the induction heating cooker, Figure 6 is a schematic circuit block diagram of a conventional induction heating cooker, and Figures 7a and b are the same induction heating cooking. A schematic circuit diagram of the RC charging/discharging circuit of the cooker and waveform diagrams of each part, Figure 8 is a front view of the area around the bow control volume trench of the induction cooker, and Figure 9 is the PWM circuit of the induction cooker. FIG. 10 is a graph of the input power with respect to the sliding position of the power control volume knob of the induction heating cooker. 8... Inverter circuit, 7... Switching element, 11... FIG charge/discharge circuit, 12
...Reference voltage setting circuit, 1o ... Comparison circuit, 20 ... Waveform obtained by modifying a triangular wave.

Claims (1)

[Claims] In a PWM circuit including an RC charge/discharge circuit that determines the on-pulse width of the drive of a switching element of an inverter circuit, a reference voltage setting circuit, a comparison circuit that compares the output of the RC photodischarge circuit and the output of the reference voltage setting circuit, etc. The maximum pulse width of the on-pulse for driving the switching element, which is the output of the PWM circuit, is 1/1 of the oscillation period.
An induction heating cooker characterized in that the waveform of the triangular wave, which is the output voltage of the RC photodischarge circuit, is modified so that the voltage does not exceed 2.