JP2794229B2 - High frequency drive for electromagnetic cooker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency drive device for an electromagnetic cooker used in, for example, an induction heating cooker, a microwave oven, and the like.

[0002]

2. Description of the Related Art FIG. 5 shows an example of an inverter circuit of a conventional high-frequency drive device used for an induction heating cooker.

In FIG. 5, two DC output terminals of a bridge type full-wave rectifier circuit (2) for full-wave rectification of a single-phase AC power supply (1), ie, a + side output terminal (3p) and a − side output terminal (3n). A choke coil (4) and a smoothing capacitor (5) are connected in series, and an induction heating coil (6) and a series connection circuit of first and second switching elements (7) and (8) using transistors constitute a smoothing capacitor. (5) is connected in parallel. First
A first resonance capacitor (10) is connected to the switching element (7), and a second resonance capacitor (11) is connected to the second switching element (8) in parallel. First switching element
(7) is turned on and off simultaneously by the first drive circuit (12) and the second switching element (8) by the second drive circuit (13), and the two switching elements (7) and (8) are turned on. During this time, current flows through the heating coil (6). The switching element may be one stage, but when the withstand voltage of the element is insufficient, a plurality of switching elements are connected in series as in this example.

The first drive circuit (12) includes a transistor (1)
4), pulse transformer (15) and three resistors (16) (17) (18)
It has. The collector of the transistor (14) is connected to a positive output terminal (19p) and to a positive power terminal (20p) via a resistor (16). Transistor (1
The emitter of 4) is connected to the negative output terminal (19n) and the negative power supply terminal (20n). The base of the transistor (14) is connected to a positive power supply terminal (20p) via a resistor (17). A resistor is connected between the base and the emitter of the transistor (14).
(18) and the secondary winding of the pulse transformer (15) are connected in series. The primary winding of the pulse transformer (15) is connected to two control signal input terminals (21p) and (21n).

[0005] The second drive circuit (13) is a first drive circuit.
It is the same as (12), and the same parts are denoted by the same reference numerals.

The positive output terminal (19) of the first drive circuit (12)
p) is connected to the base of the first switching element (7), and the negative output terminal (19n) is connected to the emitter of the first switching element (7) and the collector of the second switching element (8). Similarly, the + output terminal (19) of the second drive circuit (13)
p) is connected to the base of the second switching element (8), and the negative output terminal (19n) is connected to the emitter of the second switching element (8).

The two power terminals (2) of the first drive circuit (12)
0p) and (20n) are two DC output terminals (23) of the first power supply circuit (22).
p) and (23n) are connected to two power supply terminals (20
p) and (20n) are two DC output terminals (23p) of the second power supply circuit (24)
(23n).

[0008] The first power supply circuit (22) includes a transformer (25), a diode (26), and a capacitor (27). The capacitor (27) is connected between the output terminals (23p) and (23n), and a series connection circuit of a secondary winding of the diode (26) and the transformer (25) is connected in parallel to the capacitor (27). The primary winding of the transformer (25) is connected to the single-phase AC power supply (1). Then, the AC output transformed by the transformer (25) is half-wave rectified by the diode (26), and the DC output is obtained by charging the capacitor (27).

The second power supply circuit (24) is the same as the first power supply circuit (22), and the same parts are denoted by the same reference numerals.

The input terminals (21p) (21) of the first drive circuit (12)
n) and the input terminals (21p) and (21n) of the second drive circuit (13) are connected to the signal output terminals (29p), (29n), (30p) and (30n) of the control circuit (28), respectively. Then, the control circuit (2
8) Output terminal (29p) (29n) (30p) (30n) from positive signal (terminal
When the (29P) (30P) side outputs a positive signal), the first and second switching elements (7) and (8) are turned off, and the negative signal (the terminal (29P) (30P) side is a negative signal) ) Is output, the first
And the second switching elements (7) and (8) are turned on.

That is, in the first drive circuit (12), the output terminal (29p) (29n) of the control circuit (28) is connected to the input terminal (2
When a positive signal is input to (1p) (21n), the pulse transformer (15)
The voltage on the transistor (14) side of the secondary winding becomes positive, a positive base voltage is applied to the transistor (14), and this transistor (14) is turned on. Because of this, the transistor
(14) becomes conductive, the signal at the + side output terminal (19p) becomes L level, and the first switching element (7) is turned off. When a negative signal is input from the output terminal (29p) (29n) of the control circuit (28) to the input terminal (21p) (21n), the voltage on the transistor (14) side of the secondary winding of the pulse transformer (15) is increased. Becomes negative, transistor
When the base voltage of (14) becomes negative, this transistor (14)
Turns off. As a result, the transistor (14) is turned off, and the first power supply terminal (20p) is connected via the resistor (16) to the first power supply terminal (20p).
A positive base voltage is applied to the switching element (7), and the first switching element (7) is turned on.

The same applies to the second drive circuit (13).

[0013]

In the above-described conventional high-frequency drive device, a transformer (22) (24) is connected to power supply circuits (22) (24) for drive circuits (12) (13) of the switching elements (7) (8). 25), which results in a large circuit and a very heavy circuit weight. To eliminate such problems,
For example, Japanese Utility Model Application No. 1-76935 (Japanese Utility Model Application No. 3-14990)
Microfilm of high height as described in FIG.
It is conceivable to use a frequency drive. This high frequency
The drive circuit is for the discharge lamp and is connected in series
DC output for multiple switching elements
To apply DC voltage to each drive circuit.
ing. In this high-frequency drive circuit, switching
A smoothing capacitor is connected in parallel with the element. Soshi
When the power consumption of the load is small like a discharge lamp
Reduces the ripple of DC voltage by this smoothing capacitor.
Since the drive circuit can be made smaller,
It will not be stable. However, the microfill
High-frequency drive circuit as described in the system
When applied as is to an electromagnetic cooker, the power consumption of the load
Is large, the DC voltage can be reduced only by the smoothing capacitor.
Pull cannot be reduced and applied to each drive circuit
Voltage drop of the applied DC voltage increases,
May cause unstable operation of the drive circuit.
Problem.

An object of the present invention is to solve the above problems,
No transformer is required for the power supply of the drive circuit of the switching element , and the DC voltage applied to the drive circuit is reduced.
Prevents large voltage drops and backflow,
An object of the present invention is to provide a high frequency drive device for an electromagnetic cooker which can prevent the operation from becoming unstable .

[0015]

According to a first aspect of the present invention, there is provided a high-frequency driving device in which a plurality of switching elements are connected in series between DC output terminals obtained by rectifying an AC power supply, and a drive circuit is provided for each switching element. An inverter circuit is provided, and a predetermined DC voltage is applied as a power supply of each drive circuit by dividing the DC output with a resistor.
A series connection circuit of a resistor, a diode and a capacitor is provided.
The voltage between the terminals of this capacitor is applied to each drive circuit.
This is what is being applied .

A high-frequency drive device according to a second aspect of the present invention includes an inverter circuit in which a plurality of switching elements are connected in series between DC output terminals obtained by rectifying an AC power supply, and a drive circuit is provided for each switching element. As a power supply for each drive circuit, a predetermined DC voltage is applied by rectifying the AC power supply and then dividing the rectified voltage with a resistor.
A series connection circuit of a resistor, a diode and a capacitor is provided.
The voltage between the terminals of this capacitor is applied to each drive circuit.
This is what is being applied .

[0017]

According to the first aspect of the present invention, since a predetermined DC voltage is applied by dividing a DC output by a resistor as a power supply of a drive circuit of the switching element, a transformer is not required for the power supply of the drive circuit. It is. Ma
In each voltage division, a diode is connected in series with the capacitor.
The power consumption of the load is large because
This diode also reduces DC voltage ripple.
Comb, large DC voltage applied to the drive circuit
Drops and backflow can be prevented and therefore dry
The operation of the circuit is not unstable.

According to the second aspect of the present invention, since a predetermined DC voltage is applied by rectifying an AC power supply and dividing it by a resistor as a power supply for the drive circuit of the switching element, the power supply of the drive circuit is provided. No transformer is required. Also, in this case,
And a diode is provided in series with the capacitor.
Therefore, as in the case of the first invention, the operation of the drive circuit is improper.
No stability.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment. This is also a high-frequency drive device provided with an inverter circuit used for an induction heating cooker, and the same parts as those in the conventional example are denoted by the same reference numerals.

In this case, one power supply circuit (31) is provided instead of the first and second power supply circuits (22) and (24) of the conventional example. This power supply circuit (31) has a DC input terminal connected between the choke coil (4) and the smoothing capacitor (5).
(32), the first + output terminal (33p) connected to the + power supply terminal (20p) of the first drive circuit (12), the first drive circuit (1
2) 1st-side output terminal connected to-side power supply terminal (20n)
(33n), the second + output terminal (34p) connected to the + power supply terminal (20p) of the second drive circuit (13), and the − power supply terminal (20n) of the second drive circuit (13). A second-side output terminal (34n) is provided. Input terminal (32) and first
A first resistor (35) and a first diode (36) are connected in series between the + side output terminal (33p). First diode (36)
Is in the forward direction from the input terminal (32) side to the first + side output terminal (33p) side. A first capacitor (37) is connected between the first + output terminal (33p) and the first-output terminal (33n),
A first constant voltage diode (38) is connected in parallel to this. The first constant voltage diode (38) has a negative output terminal (33n).
From the side to the + side output terminal (33p) side. A second resistor (39) and a second diode (40) are connected in series between the first-side output terminal (33n) and the second-side output terminal (34p). The second diode (40) is connected to the first-side output terminal (3
The forward direction is from the 3n) side to the second + output terminal (34p) side. The second + side output terminal (34p) and the second side output terminal (34p)
n), a second capacitor (41) is connected to the second capacitor (41).
A constant voltage diode (42) is connected in parallel. The second constant voltage diode (42) has a forward direction from the negative output terminal (34n) to the positive output terminal (34p).

FIG. 2 shows an example of the voltage waveform at the input terminal (32) of the power supply circuit (31). This shows a case where the voltage of the AC power supply (1) is 200V. In FIG.
The value of 1 is determined by the load of the smoothing capacitor (5),
When the load is heavy, it is small, and when the load is light, it is large.

In the power supply circuit (31), the input terminal (3
2), the first capacitor (37) is charged through the first resistor (35) and the first diode (36), and the power of the first drive circuit (12) is output through the output terminals (33p) and (33n). DC voltage is applied to terminals (20p) and (20n). Next, from the minus side of the first capacitor (37), the second capacitor (41) is further charged via the second resistor (39) and the second diode (40), and the output terminals (34p) and (34n) are connected. A DC voltage is applied to the power supply terminals (20p) and (20n) of the second drive circuit (13) via the second drive circuit (13). At this time, since the constant voltage diodes (38) and (42) are connected in parallel to the capacitors (37) and (41), the terminal voltage of the capacitors (37) and (41) is changed to the constant voltage diodes (38) and (42). Of the switching elements (7) and (8) is prevented from being applied to the base of the switching elements (7) and (8).

FIG. 3 is a circuit diagram showing the first positive and negative output terminals (33
An example of a voltage waveform between p) and (33n) is shown. In the figure, Vz is the breakdown voltage of the constant voltage diode (38),
s is determined by the capacitance value of the capacitor (37) and mainly the resistance (16) of the first drive circuit (12).

The voltage waveform between the second + side and − side output terminals (34p) and (34n) is the same.

FIG. 4 shows a second embodiment.

FIG. 4 shows only the first and second drive circuits (12) and (13) and the power supply circuit (43) of the same high-frequency drive device as in the first embodiment. The same parts as in the example are denoted by the same reference numerals. The two drive circuits (12) and (13) are the same as those in the first embodiment, and are shown by blocks.

In this case, the DC input terminal (32) of the first embodiment
Instead, two AC input terminals (44a) and (44b) are provided,
A single-phase AC power supply (1) is connected to these. A full-wave rectifier circuit (47) using two diodes (45) and (46) is provided instead of the first diode (36) of the first embodiment,
A first resistor (35) is connected between the output side of the rectifier circuit (47) and the first + output terminal (33p). Others are the same as in the first embodiment.

[0029]

According to the high-frequency drive device for an electromagnetic cooker of the present invention, as described above, a transformer is not required for the power supply of the drive circuit of the switching element, and the transformer can be eliminated to reduce the size and weight. become. Moreover, each
A diode provided in series with the capacitor in the voltage divider
The amount of DC voltage applied to each drive circuit is
Voltage drop and backflow to prevent the drive circuit
The crop can be prevented from becoming unstable.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a high frequency drive device for an electromagnetic cooker according to a first embodiment of the present invention.

FIG. 2 is a time chart showing a voltage waveform of a DC input terminal of the power supply circuit of FIG. 1;

FIG. 3 is a time chart showing a voltage waveform between a first + output terminal and a first-output terminal of the power supply circuit of FIG. 1;

FIG. 4 is an electric circuit diagram of a power supply circuit portion of a high-frequency drive device for an electromagnetic cooker according to a second embodiment of the present invention.

FIG. 5 is an electric circuit diagram of a high-frequency drive device for an electromagnetic cooker showing a conventional example.

[Explanation of symbols]

(1) Single-phase AC power supply (2) Bridge type full-wave rectifier circuit (3p) (3n) DC output terminal (7) (8) Switching element (12) (13) Drive circuit (31) Power supply circuit (35) ( 39) Resistance (36) (40) (45) (46) Diode (37) (41) Capacitor (43) Power supply circuit (47) Full-wave rectifier circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H02M 7/42-7/98 H02M 1/00-1/30 H05B 6/00-6/44

Claims (2)

(57) [Claims] 1. An inverter circuit in which a plurality of switching elements are connected in series between DC output terminals obtained by rectifying an AC power supply, and a drive circuit is provided for each switching element. A predetermined DC voltage is applied by dividing the DC output with a resistor.
A series connection circuit of a resistor, a diode and a capacitor is provided.
The voltage between the terminals of this capacitor is applied to each drive circuit.
Applied high frequency drive for electromagnetic cooker . 2. An inverter circuit in which a plurality of switching elements are connected in series between DC output terminals obtained by rectifying an AC power supply, and a drive circuit is provided for each switching element. It has been made so that a predetermined DC voltage is applied by dividing at resisting After rectifying the AC power, each of the partial pressure
The resistor, diode and capacitor in series
A connection circuit is provided, and the voltage between the terminals of this capacitor
High frequency drive for electromagnetic cooker applied to drive circuit .