JPH0667213B2 - Inverter device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an inverter device that applies a high-frequency output generated in a resonant circuit to a load by on / off driving of a switching element.

[Background technology]

The switching loss of the switching element becomes a serious problem in increasing the frequency of the output of the inverter device. By detecting the conduction timing of the switching element and controlling the on / off driving of the switching element, the switching loss can be reduced.

FIG. 5 shows the conventional example. In this inverter device, a parallel resonance circuit of a primary winding of an oscillation transformer 32 and a resonance capacitor 33 and a parallel circuit in which a damper diode 35 is reversely connected to a transistor 34 are connected in series to a DC power supply 31. A choke coil 36 is connected in series to the secondary winding of the oscillation transformer 32 with respect to the load Z, and supplies high-frequency power to the load Z.

FIG. 6 (a) shows the collector voltage V _C , the collector current I _C of the transistor 34 and the damper current I _D flowing in the damper diode 35 of this inverter device. In this conventional example, the transistor 34 is turned off, the collector voltage V _C changes sinusoidally, and the damper current I _D flowing when the collector voltage V _C becomes zero is detected, and the transistor 34 is made conductive. This operation is performed by the current detection coil 37 that detects the damper current _ID flowing through the damper diode 53, the resistor 38 that converts the detection current of the current detection coil into a voltage, the capacitor 39 that generates the trigger signal V _P at that voltage, and the capacitor 39. The monostable multivibrator 40 that operates by receiving the trigger signal V _P output from
And a parallel circuit of a capacitor 41 and a resistor 42 which makes the output of the monostable multivibrator 40 the base current I _B of the transistor 34. Monostable multivibrator 40
FIG. 6 (b) shows the trigger signal V _P applied to the transistor 34, and FIG. 6 (c) shows the base current I _B applied to the transistor 34.
Is shown in. In the drive control of this transistor 34,
Since the damper current I _D is detected, the trigger signal V _P of the monostable multivibrator 40 is generated, and the base current I _B is generated, the collector current I _C flows out continuously with the damper current I _D.
There is no switching loss when the transistor 34 is on. The collector current I _C is determined by the monostable multivibrator 40
It linearly increases up to the period t during which the base current I _B set by. In this conventional example, since the collector current I _C can be controlled by changing the period t, there is also an advantage that the output can be varied while maintaining the resonance condition of the circuit. However, in this prior art example, the base current I _B is supplied to the transistor 34 immediately after the damper current I _D flows out, since the collector current I _C flows out is from the damper current I _D is disappeared, in the meantime The base current I _B flowing is wasted and causes a loss.

As a solution to this drawback, there is a conventional example in which a monostable multivibrator 43 is further provided after the monostable multivibrator 40 as shown in FIG. This conventional example
As shown in FIG. 8 (a), the monostable multivibrator 40 is used.
Then, the period t ₁ at which the damper current I _D ends is set, and the base current I _B flows after the period t _{1 as} shown in FIG. 8B. However, in this case, if an attempt is made to perform output control while changing the period t _{2 in} which the base current I _B flows, the period t ₁ in which the damper current I _D flows also changes, causing a problem.

In the conventional example shown in FIG. 9, an amplifier 44 is used instead of the capacitor 39.
Is connected to detect the timing when the damper current I _D has finished flowing, and gives a trigger signal to the monostable multivibrator 40. Further, in the conventional example shown in FIG. 10, an astable multivibrator 45 is connected instead of the monostable multivibrator 40 shown in FIG. 9, and forced synchronization is performed by a detection signal of the damper current I _D. In either case,
Since the current detection coil 37 is required, an error may occur due to noise, and the circuit becomes complicated and the cost becomes high.

[Object of the Invention]

An object of the present invention is to solve the problems of the conventional example, and to provide an inverter device capable of efficiently performing drive control of a switching element with a simple and inexpensive structure without malfunction.

[Disclosure of Invention]

The inverter device of the present invention includes an inductance element that generates high-frequency power to be supplied to a load, a switching element that is connected in series to the DC power source with the inductance element, and a first diode that is connected in antiparallel to the switching element. A resonance capacitor connected in parallel to either one of the inductance elements, a second diode connected in the forward direction between the switching element and the negative electrode of the DC power supply, and turned on by the reverse bias voltage of the second diode. And a control circuit for controlling the conduction of the switching element for a certain period after the transistor is switched from ON to OFF.

According to this invention, there are the following effects. When the switching element is cut off, a current flows through the first diode and the reverse bias voltage of the second diode turns on the transistor. When no current flows through the first diode, the reverse bias voltage of the second diode disappears, and the transistor changes from on to off. When this transistor changes from on to off, the control circuit conducts the switching element for a certain period. Therefore, after the current stops flowing through the first diode and the switching element becomes conductive, the control circuit controls the switching element to be conductive, so that the drive control of the switching element is efficiently performed.

Embodiment FIG. 1 is a circuit diagram showing the structure of an embodiment of the present invention. In this inverter device, an oscillation transformer 2 that is an inductance element and a transistor 3 that is a switching element are connected in series to a DC power supply 1, a resonance capacitor 4 is connected in parallel to the oscillation transformer 2, and a first capacitor is connected to the transistor 3. Diode 5 is connected in anti-parallel. A second terminal is provided between the transistor 3 and the negative electrode of the DC power supply 1.
Is connected in the forward direction, the anode side of the second diode 6 is connected to the emitter of the transistor 7, and the cathode side thereof is connected to the base of the transistor 7 via the resistor 8. The direct current voltage V _CC is applied to the collector of the transistor 7 via the resistor 9. Control circuit 10 for controlling the switching cycle of the transistor 3
Is a resistor in synchronization with the on / off operation of the transistor 7.
A base current is supplied to the transistor 3 via a waveform shaping circuit 14 composed of 11, 12 and a capacitor 13. A choke coil 15 and a load Z to which high frequency power is supplied are connected in series to the secondary winding of the oscillation transformer 2.

FIG. 2 is a circuit diagram showing an example of the configuration of the control circuit 10.
The IC is a general-purpose timer composed of an integrated circuit, and for example, NE555 manufactured by Signetic Co. is applied. This general-purpose timer IC, together with the resistor 16 and the capacitors 17 and 18, constitutes a monostable multivibrator. The 2nd terminal of the general-purpose timer IC is the trigger terminal, and the general-purpose timer is 1 / 3V _CC or less.
The IC performs a timed operation determined by the resistor 16 and the capacitor 17.
Therefore, when transistor 19 is off,
No. pin is pulled up to V _CC , and the general-purpose timer IC does not operate. When the transistor 7 is switched from on to off, a positive pulse is supplied from the terminal a of the control circuit 10 via the capacitor 21 to the base of the transistor 19. When the transistor 19 turns on, the voltage of the 2nd terminal of the general-purpose timer IC becomes 1 / 3V _CC or less, and the signal with the timed operation is output to the 3rd terminal. The signal is output from the terminal c of the control circuit 10 to the waveform shaping circuit 14
Given to. In this control circuit 10, the diode 22
Is for discharging the capacitor 21, and the resistor 23 is a transistor
There are 19 base resistors.

Next, the operation of this embodiment will be described with reference to the waveform chart of FIG. FIG. 3A shows the collector voltage V of the transistor 3.
_CE , collector current I _C and damper current I _D flowing through the first diode 5 are shown, FIG. 3 (b) shows the collector voltage v _C of the transistor 7, and FIG. 3 (c) is the base current I of the transistor 3. _B shown. When the transistor 3 is off, the DC power source 1, the resistor 8,
A damper current I _D flows through the base / emitter of the transistor 7 and the first diode 5. That is, a potential is generated between the cathode and the anode of the second diode 6, and the transistor 7 is turned on. While the transistor 7 is turned on and the damper current I _D is flowing, the collector voltage v _C becomes low level as shown in FIG. 3 (b). When the damper current _ID has finished flowing, the collector voltage v _C of the transistor 7 becomes high level. The rising of the collector voltage v _C at this time gives a positive pulse to the transistor 19 via the capacitor 21 of the control circuit 10, and the output signal is given from the terminal c of the control circuit 10 to the waveform shaping circuit 14 by the above-described operation. To be The output of the waveform shaping circuit 14 is given to the transistor 3 as the base current I _B as shown in FIG.
When the base current I _B is applied, the transistor 7 is turned on, and its collector current Ic flows through the second diode 6. By repeating such operations, the high frequency output is efficiently supplied to the load Z.

As described above, this embodiment does not require a coil for detecting the damper current I _D as in the conventional example, and the detection amplification is performed by the operation of the transistor 7. Therefore, the circuit configuration for detecting the damper current I _D can be realized easily at low cost and can be integrated into a circuit. Further, since the detection coil is not used to detect the damper current I _D as in the conventional example, malfunction does not occur due to external noise. Needless to say, since the base current I _B is supplied to the transistor 3 after the damper current I _D has finished flowing, the capacity of the control power supply can be small.

FIG. 4 is a circuit diagram showing the configuration of another embodiment of the present invention. In this embodiment, the second diode 6 of the above-mentioned embodiment is replaced with a Zener diode. Second
The transistor 7 can be miniaturized by using the Zener diode as the diode 6 of FIG. That is, the base current of the transistor 7 is limited by the Zener voltage of the Zener diode 6 and the resistor 8, and most of the damper current I _D flows in the Zener diode 6, so that the power loss in the resistor 8 is reduced and the transistor 7 is turned on. Since it can be used for small signals, it is effective in forming an integrated circuit. Further, as a reference, the same effect can be obtained by providing a series circuit in which two or more diodes are connected in antiparallel with the second diode 6 of the above-described embodiment, instead of the Zener diode.

〔The invention's effect〕

According to the present invention, when a current flows in the first diode connected in anti-parallel to the switching element, a reverse bias voltage is generated in the second diode to turn on the transistor, and when the current stops flowing in the first diode, the transistor is turned on. By switching from ON to OFF, the control circuit responding to the operation of the transistor becomes conductive and then the switching element is made conductive.Therefore, the configuration is simpler and cheaper than the conventional example, and switching is performed without malfunction. It is possible to control the drive of the element and improve the output efficiency.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing the structure of an embodiment of the present invention, and FIG.
FIG. 4 is a circuit diagram showing an example of the configuration of the control circuit, FIG. 3 is a waveform diagram for explaining the operation of an embodiment of the present invention, and FIG. 4 is a circuit diagram showing the configuration of another embodiment of the present invention. 5, FIG. 5 is a circuit diagram showing the configuration of the conventional example, FIG. 6 is a waveform diagram for explaining the operation of the conventional example, FIG. 7 is a circuit diagram showing the configuration of another conventional example, and FIG. 8 is another. Circuit diagram showing a configuration of a conventional example of No. 9,
FIG. 10 to FIG. 10 are circuit diagrams showing configurations of other conventional examples. 1 ... DC power supply, 2 ... Inductance element, 3 ... Transistor (switching element), 4 ... Resonance capacitor, 5 ... First diode, 6 ... Second diode, 7 ... Transistor, 10 ...... Control circuit

Claims (2)

[Claims] 1. An inductance element for generating high-frequency power supplied to a load, a switching element connected in series with the inductance element for a DC power source, a first diode connected in antiparallel to the switching element, and the inductance. A resonance capacitor connected in parallel to either one of the switching element and the switching element, a second diode connected in the forward direction between the switching element and the negative electrode of the DC power supply, and a reverse bias voltage of the second diode. An inverter device comprising: a transistor that is turned on; and a control circuit that controls to electrically connect the switching element for a certain period after the transistor is turned off. 2. The inverter device, wherein the second diode is a Zener diode.