JPS5830705B2 - Output control device for high frequency heating equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to an output control device for a high frequency heating device.

Conventionally, output control devices for high-frequency heating devices include devices that switch the capacity using a capacitor, devices that change the input voltage of a current stabilizing transformer, and the like.

Among these, the one that switches the capacitor capacity is equipped with a current stabilizing transformer 1, a high voltage rectifier circuit 2, a high frequency generation source 3 consisting of a magnetron, a magnetron heater circuit 4, etc., as shown in FIG. 1, for example. Capacitors Cty, C2y, and Cs are connected in parallel, and these capacitors C, 2, and Cs are connected by a changeover switch 81. The high frequency output of the high frequency generation source 3 is controlled by selectively switching and connecting the capacitors in the circuit via S2 and changing the combined capacitance of the capacitors.

Capacitors that switch the capacitor capacity can obtain a stable high-frequency output at the operating point where the capacitance is fixed, but they have the disadvantage that the high-frequency output can only be controlled in stages. .

Further, in the case where the input voltage of the current stabilizing transformer is changed, the relationship between the input voltage of the current stabilizing transformer and the anode current of the magnetron is as shown in FIG.

The reason why a current stabilizing transformer (leakage transformer) is used as the high voltage transformer is to obtain a stable high frequency output against voltage fluctuations around its operating voltage.

In such a high-frequency output control device, due to the characteristics of the current stabilizing transformer, the magnetron anode current Ip in the vicinity of the set voltage Vs changes the input voltage of the current stabilizing transformer to △V.
By varying the output voltage by s volts, the output voltage changes continuously and stably by ΔIps without being affected much by the input voltage of the current stabilizing transformer, but there is a drawback that the output variation width ΔIps is small.

In addition, in order to compensate for this drawback, if the input voltage of the current stabilizing transformer is extremely lowered and set near Vtport, the magnetron anode current will change by the AIpt width with respect to the fluctuation width of △■, and the high frequency output control width will become large. .

However, if the magnetron's anode current changes greatly due to small changes in the transformer voltage, the high-frequency output will change significantly even with small changes in the power supply voltage, making it impossible to stabilize the output. It's rare.

Furthermore, as seen in Japanese Patent Application Laid-Open No. 52-30944,
A high-frequency heating device has also been proposed in which the primary side of a transformer is intermittently excited with a variable duty, and the output is controlled by switching the capacitance of a secondary high-voltage rectifier circuit.

However, in this case, the high frequency oscillation becomes intermittent, leading to a shortened lifespan of the high frequency oscillation source.

This invention has been made in view of this point, and one embodiment will be described below.

In FIG. 3, 5 is a current stabilizing transformer, 6 is a voltage regulator such as a slider for adjusting the input voltage of the transformer 5, 7 is a high voltage rectifier circuit connected to the rear stage of the transformer 5, and 8 is a diode, 9 is a capacitor with a capacity of C1, 10 is a capacitor connected in parallel with the capacitor 9 via a changeover switch 11, 12 is a capacitor connected in parallel with the capacitor 9 through a changeover switch 13, 14
1 is a magnetron driven by electricity from the high voltage rectifier circuit 7, and 15 is a heater transformer of the magnetron 14.

FIG. 4 shows the operation control characteristics of the above circuit.

The horizontal axis of this figure is the input voltage value Vi of the current stabilizing transformer 5.
n, and the vertical axis is the anode current value I of the magnetron 14.
p.

The characteristic curve Ipl shows the relationship between the transformer input voltage and the magnetron anode current when only the capacitor 9 is connected in the circuit.

The characteristic curve Ip2 shows the above relationship when, in addition to the capacitor 9, the changeover switch 11 is closed and the capacitor 10 is connected to the circuit.

The characteristic curve Ip3 is obtained by further closing the changeover switch 13,
The above relationship is shown when capacitors 9, 10, and 12 are connected in a circuit.

Then, the input voltage of the current stabilizing transformer 5 is varied by operating the voltage regulator 6 within a band Δ■ in which the variation range of the magnetron anode current is smaller than the variation range of the current stabilizing transformer input voltage.

In setting the input voltage band △■ of such a transformer, the maximum value I of II) 1 current shown in the engineering p1 characteristic curve
p1h is equal to or greater than the lowest current value Ip2t of the Ip2 characteristic curve, and II) the maximum value Ip2h of the Ip2 current shown in the 2 characteristic curve is equal to or greater than the lowest current value Ips7 of the Ip3 characteristic curve. Consider this.

Therefore, by changing the input voltage of the transformer 5 and by changing the capacitor capacity in the high voltage rectifier circuit 7, the magnetron anode current can be maintained continuously from the Iplt value to the IpsL value in a stable state with respect to the power supply voltage. variable while maintaining the

According to the present invention configured as described above, it operates stably against power supply voltage fluctuations and does not involve intermittent oscillation.
It is possible to provide an output control device for a high-frequency heating device that can continuously control high-frequency output.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a conventional example, Fig. 2 is a table showing the control characteristics of the conventional example, Fig. 3 is a diagram showing an embodiment of the present invention, and Fig. 4 is a diagram showing the control characteristics of the same embodiment. FIG. 5... Current stabilizing transformer, 7... High voltage rectifier circuit, 9.10, 12... Capacitor, 11.13...
Changeover switch, 14... High frequency generation source, △■... Stable operating range of current stabilizing transformer.

Claims (1)

[Claims] 1 In a device in which the voltage from the power source is input to a current stabilizing transformer to step up the voltage and then supplied to the high frequency generation source via a high voltage rectifier circuit consisting of a capacitor, etc., the capacitor of the high voltage rectifier circuit An output control device for a high-frequency heating device, comprising a plurality of capacitors, the capacitors being selectively connected via a changeover switch, and the input voltage of the current stabilizing transformer being varied within a stable operating range of the transformer.