JPS61295876A - Inverter - Google Patents

Abstract

PURPOSE:To eliminate an erroneous operation of drive control by conducting a switching element for the prescribed period from the end of the operation of a transistor which operates by detecting a voltage between the cathode and the anode of a diode connected in series with a switching element. CONSTITUTION:An inductance element 2 and a switching element 3 are connected in series with a DC power source 1. A diode 5 is connected in anti- parallel with the element 3, and a resonance capacitor 4 is connected in parallel with the element 2. A diode 6 is connected forward between the element 2 and the negative electrode of the power source 1. A transistor 7 operates by a potential difference between the cathode and the anode of the diode 6, and a controller 10 conducts the element 3 for the prescribed period from the end of the operation of the transistor 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an inverter device that provides a load with a high frequency output generated in a resonant circuit by turning on/off a switching element.

[Background technology]

When increasing the frequency of the output of an inverter device, switching loss of switching elements becomes a major problem. By detecting the conduction timing of the switching element and controlling the on/off drive of the switching element, switching loss can be reduced.

This inverter device, a conventional example of which is shown in FIG. The connected parallel circuits are connected in series, and the oscillation transformer 3 is connected to the load 2.
A chill coil 36 is connected in series to the secondary winding of No. 2 to supply high frequency power to the load Z.

The transistor 34 of this inverter device is shown in FIG.
In this conventional example, the transistor 34 is turned off and the collector voltage Vc changes sinusoidally, and the collector voltage Vc becomes zero. The damper current ID flowing when the current is applied is detected, and the transistor 34 is made conductive. This operation is caused by damper diode 35
A current detection coil 37 that detects the damper current ID flowing in the
, a resistor 38 that converts the detected current of the current detection coil into voltage.
, a capacitor 39 that generates a trigger signal Vp at that voltage.
, a monostable multivibrator 40 operated in response to a trigger signal Vp output from a capacitor 39, and a parallel circuit of a capacitor 41 and a resistor 42 that convert the output of the monostable multivibrator 40 into the base current 1B of the transistor 34. ll stable multivi break 4
The trigger signal Vp applied to the transistor 34 is shown in Figure 6 (bl), and the base current IB applied to the transistor 34 is shown in Figure 6 (C1). Detects the trigger signal vP of the monostable multi-by break 40, and connects the base voltage 1.
5! In order to generate EI B, collector current ■D flows continuously with damper current ID, so transistor 3
The switching loss during the ON operation of 4 is eliminated. The collector current 1c is the base current 1. set by the monostable multi-bi break 40. increases linearly until the period t during which . In this conventional example, since the collector current Ic can be controlled wi by changing the period t, there is an advantage that the output can be varied while maintaining the resonance condition of the circuit. However, in this conventional example, the base current IB is supplied to the transistor 34 immediately after the damper current IQ starts flowing, but the collector current IC starts flowing only after the damper current In disappears. IB becomes wasted and results in 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. In this conventional example, as shown in FIG. 8, a period t1 is set in which the damper current I n finishes flowing in the monostable multivibrator 40, and a base current r after the period tl is set as shown in FIG.
However, in this case, if you try to control the output by changing the period t2 during which the base current IB flows, the damper current 1. Since the period t1 during which the signal flows also changes, this causes a problem.

In the conventional example shown in FIG. 9, an amplifier 44 is connected in place of the capacitor 39, the timing at which the damper current In finishes flowing is detected, and a trigger signal is given to the monostable multi-vibration break 40. Further, in the conventional example shown in FIG. 10, an astable multivibrator 45 is connected in place of the monostable multivibrator 40 in FIG. 9, and forced synchronization is performed by a detection signal of the damper current ID.

In either case, a current detection coil 37 is required,
There is a risk that malfunction may occur due to noise, and the circuit is complicated, resulting in increased cost.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art and to provide an inverter device that has a simple and inexpensive configuration and can efficiently control the drive of switching elements without malfunction.

[Disclosure of the 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 connected in series with the inductance element with respect to a DC power supply, and a first diode connected in antiparallel to the switching element. A resonance capacitor connected in parallel to either one of the inductance elements, a second diode forward-connected between the switching element and the negative electrode of the DC power supply, and a circuit between the cathode and anode of the second diode. The device includes a transistor that operates by detecting a potential difference, and a control circuit that controls the switching element to be conductive for a certain period of time from the end of the operation of the transistor.

According to this invention, there are the following effects. When the switching element is cut off, current flows through the first diode, creating a potential difference between the cathode and anode of the second diode, causing the transistor to operate.

When current stops flowing through the first diode, the potential difference between the cathode and anode of the second diode disappears, and the operation of the transistor ends. When the operation of this transistor is completed, the control circuit turns on the switching element for a certain period of time. Therefore, after the current stops flowing through the first diode and the switching element becomes conductive, the control circuit performs control to make the switching element conductive, so that drive control of the switching element is efficiently performed.

Embodiment FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention. In this inverter device, an oscillation transformer 2 which is an inductance element and a transistor 3 which 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 diodes 5 are connected in antiparallel.

A second diode 6 is connected in the forward direction between the transistor 3 and the negative electrode of the DC power supply 1, the emitter of a transistor 7 is connected to the anode side of the second diode 6, and the emitter of the transistor 7 is connected to the cathode side of the second diode 6. A transistor 70 base is connected via a resistor 8.

A DC voltage VCC is applied to the collector of the transistor 7 via a resistor 9. A control circuit 10 that controls the switching period of the transistor 3 controls whether the transistor 7 is turned on or off.
In synchronization with the OFF operation, a chiller coil 15 and high frequency power are connected to the secondary winding of the zero oscillation transformer 2, which supplies base current to the transistor 3 via a waveform shaping circuit 1.4 consisting of a resistor 1)゜12 and a capacitor 13. The supplied loads Z are connected in series.

FIG. 2 is a circuit diagram showing an example of the configuration of the control circuit 10. As shown in FIG. The IC is a general-purpose timer composed of an integrated circuit, and for example, NE555 manufactured by Sidanetic is commonly used. This general purpose timer IC has 16 resistors and 17,18 capacitors.
Together, they form a monostable multivibrator. The second terminal of the general-purpose timer IC is the trigger terminal, and 1/3
Below Vcc, the general-purpose timer IC requires 16 resistors and 1 capacitor.
Therefore, when the transistor 19 is off, the No. 2 terminal is pulled up to VCC through the resistor 20, and the general-purpose timer IC is not operated. When the transistor 7 is turned on, a positive pulse is supplied to the base of the transistor 19 from the terminal a of the control circuit IO via the capacitor 21.

When the transistor 19 is turned on, the voltage at the second terminal of the general-purpose timer tC becomes 1/3 Vcc or less, and a signal with a timed operation is output to the third terminal, and this signal is sent to the control circuit 10.
is applied to the waveform shaping circuit 14 from the terminal C of. In this control circuit 10, the diode 22 is for discharging the capacitor 21, and the resistor 23 is the base resistor of the transistor 19.

Next, the operation of this embodiment will be explained with reference to the waveform diagram in FIG. FIG. 3(a) shows the collector voltage V of transistor 3.
C% collector current 1c and damper current ID flowing through the first diode 5 (in FIG. 3) is the transistor 7.
Figure 3 shows the collector voltage vc of the transistor 3 (Cl shows the base current ■B of the transistor 3;
, a damper current 10 flows through the resistor 8, the base-emitter of the transistor 7, and the first diode 5. That is, a potential difference is generated between the cathode and anode of the second diode 6, and the transistor 7 is turned on.

While the transistor 7 is on and the damper current TD is flowing, its collector voltage V(
is at a low level. When the damper current ID finishes flowing, the collector voltage V( of the transistor 7 becomes a high level. As the collector voltage V( rises at this time, a positive pulse is applied to the transistor 19 via the capacitor 21 of the control circuit 10. In the above-described operation, an output signal is provided from terminal C of control circuit 10 to waveform shaping circuit 14.

The output of the waveform shaping circuit 14 is applied to the transistor 7 as a base current, as shown in FIG. 3(C). When the base current IB is applied, the transistor turns on, and its collector current 1c flows through the second diode 6. Such operations are repeated, and the high frequency output is efficiently supplied to the load Z.

As described above, in this embodiment, unlike the conventional example, a coil for detecting the damper current ro is not required, and the detection and amplification is performed by the operation of the transistor 7.

Therefore, the circuit configuration for detecting the damper current ID can be realized easily and at low cost, and can also be integrated into an integrated circuit. Furthermore, since a detection coil is not used as in the conventional example to detect the damper current rD, there is no malfunction caused by external noise.Needless to say, after the damper current ID has finished flowing, the base current 1゜ is supplied, so the capacity of the control power source can also be small.

FIG. 4 is a circuit diagram showing the configuration of another embodiment of the invention. In this embodiment, the second diode 6 of the previous embodiment is replaced with a Zener diode. Second
By using a Zener diode as the diode 6, the transistor 7 can be made smaller. 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 In flows through the Zener diode 6, thereby reducing the power loss in the resistor 8 and reducing the transistor 7. Since it can be used for signals, it is effective for integrated circuits. As a reference, even if a series circuit in which two or more diodes are connected in antiparallel to the second diode 6 of the above-mentioned embodiment is provided instead of the Zener diode,
A similar effect can be obtained.

C. Effects of the invention] According to the invention, when a current flows through the first diode connected in antiparallel to the switching element, a potential difference is generated between the cathode and anode of the second diode, the transistor operates, and the first diode is connected in parallel with the switching element. When the current stops flowing through the diode, the operation of the transistor ends, and the control circuit that responds to the operation of the transistor becomes conductive, and then the switching element is controlled to be conductive.
The switching element can be driven IIJrB without malfunction with a simpler and cheaper configuration than the conventional example, and the output efficiency can be improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention, and FIG.
Figure 3 is a circuit diagram showing an example of the configuration of a control circuit, Figure 3 is a waveform diagram for explaining the operation of an embodiment of the present invention, and Figure 4 is a circuit diagram showing the configuration of a further embodiment of the invention. , 5th I!
I is a circuit diagram showing the configuration of a 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 conventional example. A circuit diagram showing the configuration of
FIGS. 9 and 10 are circuit diagrams showing the configuration of other conventional examples. 1... DC power supply, 2... Inductance element, 3...
...Transistor (switching element), 4...Resonance capacitor, 5...First diode, 6...Second 1-, N; Figure 3, Figure 4, Figure 5, Figure 6

Claims (2)

[Claims] (1) An inductance element that generates high-frequency power to be supplied to a load, a switching element connected in series with the inductance element with respect to a DC power supply, a first diode connected in antiparallel to this switching element, the inductance element and a resonant capacitor connected in parallel to either one of the switching elements, a second diode forward-connected between the switching element and the negative electrode of the DC power supply, and a potential difference between the cathode and anode of the second diode. An inverter device comprising: a transistor that detects and operates the switching element; and a control circuit that controls the switching element to be conductive for a certain period of time from the end of the operation of the transistor. (2) The inverter device according to claim (1), wherein the second diode is a Zener diode.