JPH0224278Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a driving circuit for a switching element suitable for use in a so-called electromagnetic cooker.

BACKGROUND ART AND PROBLEMS A conventional electromagnetic cooker will be explained with reference to FIG.
1a and 1b are power supply terminals connected to commercial AC power supply terminals, 2 is a power switch, 3 is a rectifier circuit, 4 is a smoothing circuit, 5 is a work coil, 6 is a resonance capacitor, 7 is a damper diode, 8 is a GCS, etc. , and 9 represents the drive circuit as a whole. 10a and 10b are DC power supply terminals,
10a is for example +12V, 10b is for example -11V
It is.

Furthermore, 11a and 11b are complementary connected output transistors, 12 is a transistor at the previous stage thereof, 12a is an oscillation pulse input terminal, and 13 and 14 are resistors, respectively. The emitters of the transistors 11a and 11b are connected through a diode 15, and the connection point between the diode 15 and the emitter of the transistor 11b is connected to the gate of the switching element 8 through an inductance coil 16. 1
7 is a resistor, and 18 is a diode.

A capacitor 19 is connected between the collector of the transistor 11a and ground. With this configuration, the current _I1 flowing through the gate of the switching element 8 becomes as shown in FIG. 2A.

Therefore, assuming that the output transistor 11a is turned on by the switching signal supplied to the base of the transistor 12, current is supplied from the power supply terminal 10a through the collector-emitter of this transistor. At the same time, the charge accumulated in the capacitor 19 is also transferred to this transistor 11a.
Since the current flows through the switching element 8, a large current can be supplied when the switching element 8 is turned on, and appropriate control can be performed.

Next, when the output transistor 11b is turned on by the signal supplied to the transistor 12 (the output transistor 11a is turned off), the power supply terminal 10a is connected to the capacitor 19 through the resistor 13 as the transistor 11a is turned off. Current begins to flow, which causes current to begin flowing to capacitor 19,
This is charged. Since the impedance of the capacitor 19 is extremely low, the charge current in this case exhibits extremely sharp characteristics as is clear from the current I ₂ shown in FIG. 2B. That is, an extremely sharp impulse will occur.
This means that high frequency components will be generated in the current _I2 distribution system, which may cause serious interference to television receivers and the like.

Purpose of the invention In view of the above-mentioned points, the present invention is designed to prevent such sharp impulses from occurring.

Summary of the invention This invention consists of a capacitor and a charging impedance element connected in parallel to a series circuit consisting of the collector-emitter of an output transistor of a drive circuit that drives a switching element that turns on and off the flow of a large current, and the above-mentioned switching element. A series circuit is connected to the impedance element, and a series circuit consisting of a diode and a discharge impedance element is connected in parallel to the impedance element, and when the output transistor is on, the current of the capacitor flows through the diode. The feature is that the flow is selected in the direction in which it can flow.

Embodiment An example of a circuit according to the present invention will be described below with reference to FIG.

Components corresponding to those in FIG. 1 are given the same reference numerals and their explanations will be omitted.

That is, in the present invention, a charging impedance element 20 is further connected in series with the capacitor 19. In this case, the impedance element 20 is configured with a series circuit of a resistor 20a and an inductance coil 20b. Furthermore, such an impedance element 20
In contrast, a series circuit of a diode 21 and an impedance element 22 is connected in parallel.
This is a case where an inductance coil is used as this impedance element 22.

According to such a configuration, as described above, when the output transistor 11a is off, a current is supplied to the capacitor 19 through the inductance element 20, so that the current value at this time is the first
This is extremely low compared to the case shown in the figure (see FIG. 2C), and therefore no impulse as shown in FIG. 2B is generated. Of course, in this case, the charging time will be longer than in the case of FIG.
It is quite sufficient.

When the output transistor 11a is turned on after the capacitor 19 is charged in this way, this charging current is supplied through the transistor 11a and the switching element 8 through the diode 21, and therefore, as described at the beginning, a large current is generated. It has the characteristics that the switching element can be turned on by switching, therefore, the switching characteristics can be improved, and a small constant current is sufficient. Moreover, as mentioned above, the capacitor 1
9, no impulses as shown in FIG. 2B are generated, so there is no risk of causing trouble to a television receiver or the like. Moreover, it has the great feature of improving switching characteristics.

Effects of the invention According to the invention described above, by only adding the impedance elements 20, 22 and the diode 21, interference to the television receiver can be avoided, and the switching characteristics can be expected to have a feature with almost no risk of being impaired. It's something you get.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing an example of a conventional electromagnetic cooker, FIG. 2 is a waveform diagram for explaining the same, and FIG. 3 is a connection diagram showing an example of a circuit according to the present invention. 5 is a work coil, 8 is a switching element, 9
1 is a drive circuit, 11a and 11b are output transistors, 19 is a capacitor, 20 and 22 are impedance elements, and 21 is a diode.

Claims (1)

[Scope of utility model registration request] As a drive circuit that drives a switching element that turns on and off the current in the work coil of an electromagnetic cooker, it consists of a push-pull type switching circuit in which the emitters of one and the other complementary transistors are connected to each other, and from this common emitter. a drive current is supplied to the control electrode of the switching element, the collector of the one transistor is connected to one end of the power supply, and the collector of the other transistor is connected to the other end of the power supply via a first resistor, The connection point between the first resistor and the collector of the transistor is grounded via a series circuit of a capacitor, a second resistor, and a first coil, and the connection point between the capacitor and the second resistor is connected to a diode. A driving circuit for a switching element, wherein the switching element is grounded through a second coil, and the diode is selected in a direction such that the current of the capacitor can flow through the diode when the other transistor is on.