JPH0446072B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an inverter device that converts low frequency AC power such as commercial frequency AC power into high frequency power.

[Background technology]

FIG. 5 shows an example of the configuration of a conventional single-stone inverter device.

This inverter device includes a rectifier 3 connected to a commercial power source 1 via a power switch 2, a main smoothing capacitor 4 connected to the output end of the rectifier 3, a discharging resistor 5 connected in parallel to the main smoothing capacitor 4, and a main smoothing capacitor 4 connected to the output terminal of the rectifier 3. A series circuit of the primary winding N1 of the transformer 6 connected to the output end of the rectifier 3 in parallel with the smoothing capacitor ₄ , a load 14, and a transistor 7, and a resonant capacitor 8 and a damper diode 9 connected in parallel with the transistor 7. and a drive circuit 10 that provides an on/off drive signal V ₁₀ to the base of the transistor 7.
, a smoothing capacitor 12 for the drive circuit connected to the power input terminal of the drive circuit 10 , a starting capacitor 11 connected between the output terminal of the rectifier 3 and the power input terminal of the drive circuit 10 , and two parts of the transformer 6 . Next winding
A diode 13 rectifies the output of N ₂ and applies it to the power input terminal of the drive circuit 10.

In this case, the primary winding N ₁ of the transformer 6 and the load 1
4 and the resonant capacitor 8 constitute a resonant circuit 15, and the secondary winding _N2 of the transformer 6 and the diode 13 take out a part of the resonant power of the resonant circuit 15, rectify it, and supply it to the power input terminal of the drive circuit 10. The additional power supply circuit 16 is configured.

Next, the operation of this inverter device will be explained with reference to the operating waveform diagram in FIG. 6 and the voltage explanatory diagram in FIG. 7. In FIG. 6, A indicates the on/off drive signal V ₁₀ , B indicates the collector current I _C of the transistor 7, and C indicates the voltage across the resonant capacitor 8, that is, the collector voltage V _C of the transistor 7.
, D indicates the voltage V _N1 across the primary winding N ₁ of the transformer 6, and E indicates the load current I _Z.

This inverter device, as shown in Fig. 6,
When the on/off drive signal V ₁₀ becomes high level, the transistor 7 is turned on, and a linearly increasing collector current I _C flows into the transistor 7 through the primary winding N ₁ of the transformer 6 and the load 14. after that,
When the on/off drive signal V ₁₀ becomes low level, the transistor 7 is turned off and the collector current I _C becomes zero, but the current flowing in the primary winding N ₁ of the transformer 6, that is, the load current I _Z becomes After that, the current continues to flow in the same direction, and the current flows through the resonant capacitor 8.
The voltage flows through the resonant capacitor 8 and charges the resonant capacitor 8, and the voltage across the resonant capacitor 8, that is, the collector voltage V _C of the transistor 7 increases in a sinusoidal manner. Then, when the stored energy in the primary winding _N1 of the transformer 6 becomes zero, a discharge current flows from the resonant capacitor 8 toward the primary winding _N1 of the transformer 6, and the collector voltage V _C becomes sinusoidal. It's going down. When the collector voltage V _C becomes zero, a regenerative current I _D flows through the damper diode 9.

Thereafter, when the on/off drive signal V ₁₀ becomes high level again, the transistor 7 is turned on and the above-described series of operations is repeated.

Next, the operation of the drive circuit 10 and its peripheral parts will be explained with reference to FIG. Set power switch 2 to time
When turned on at t ₀ , the voltage across the main smoothing capacitor 4
V ₄ instantly rises to a certain value. Moreover, since the starting capacitor 11 and the drive circuit smoothing capacitor 12 are connected in series and connected in parallel to the main smoothing capacitor 4, the voltages V ₁₁ and V 12 across both capacitors 11 and ₁₂ at the initial stage of power-on are as follows. The voltage _V4 is divided according to each capacitance.
If the capacitance of the starting capacitor 11 is C ₁₁ and the capacitance of the drive circuit smoothing capacitor 12 is C ₁₂ , then the voltage V ₁₁ across the starting capacitor 11 is V ₁₁ = C ₁₂ /C ₁₁ +C ₁₂・V ₄ , and the driving circuit The voltage V ₁₂ across the circuit smoothing capacitor 12 is V ₁₂ = C ₁₁ /C ₁₁ +C ₁₂ · V ₄ , and the voltage V ₁₂ is V ₁₂ > V _D with respect to the minimum operable power supply voltage V _D of the drive circuit 10. The partial pressure ratio is set so that

Then, by applying the voltage V ₁₂ to the power input terminal of the drive circuit 10, the drive circuit 10 is turned on/off.
The off-drive signal V ₁₀ is output, thereby performing the series of operations described above and supplying high-frequency power to the load 14.

On the other hand, since the power supply input impedance Z of the drive circuit 10 is not infinite but has a predetermined value, after the power is turned on, the voltage V ₁₂ gradually decreases toward zero volts, and the voltage V ₁₁ conversely decreases. Voltage V ₄
However, at a time t _a before the voltage V ₁₂ becomes lower than the minimum operable power supply voltage V _D of the drive circuit 10, the secondary winding of the transformer 6 is turned on and off by the on/off operation of the transistor 7. A voltage is induced in _N2 , and the voltage is rectified by the diode 13 and applied to the power input terminal of the drive circuit 10, that is, both ends of the smoothing capacitor 12 for the drive circuit, and at that point, the voltage _V12 stops decreasing. It stops and remains in a constant state (a constant voltage higher than the minimum operable power supply voltage V _D ), and therefore the voltage V ₁₁ also stops increasing and becomes constant.

Since the voltage V ₁₂ remains higher than the minimum operable power supply voltage V _D , the drive circuit 10 continues to output the on/off drive signal V ₁₀ and the load 14
The supply of high-frequency power will continue.

In this inverter device, if the load 14 is disconnected for some reason during operation, the voltage generated in the secondary winding _N2 of the transformer 6 will disappear, and charging of the drive circuit smoothing capacitor 12 will be interrupted, so the voltage
V ₁₂ drops, voltage V ₁₂ becomes the lowest operating supply voltage
When the voltage drops below V _D , the operation of the drive circuit 10 stops,
Further, the voltage V ₁₁ increases by the amount that the voltage V ₁₂ decreases. After this, even if the load 14 is reconnected,
Voltage across the drive circuit smoothing capacitor 12
Since V ₁₂ remains falling and does not rise, the drive circuit 10 does not operate, and power is not supplied to the load 14 unless the power switch 2 is turned off.

As described above, this conventional example has a feature of high conversion efficiency because a part of the resonance power of the resonance circuit 15 is extracted and supplied to the drive circuit 10 as drive power. Further, once the load 14 is disconnected, even if the load 14 is reconnected, power will not be supplied to the load 14 as it is, so it is safe.

However, the conventional inverter device described above has the following problems. This problem will be explained with reference to FIG. As shown in FIG. 8, after the power is turned on and the voltages V ₄ , V ₁₁ , and V ₁₂ are stabilized, the time t _d
When the power switch 2 is turned off, the power supply from the commercial power supply 1 is stopped, and the voltage V 4 across the main smoothing capacitor ₄ gradually decreases due to discharge through the discharge resistor 5, etc., and as a result, the voltage V ₁₁ , V ₁₂ also changes. In this case, no resistance is connected to the starting capacitor 11, and the power supply input impedance Z of the drive circuit 10 is connected in parallel to the drive circuit smoothing capacitor 12, so that at time t _d Even when the power switch 2 is turned off, the voltage V ₁₁ hardly drops at first, only the voltage V ₁₂ drops somewhat gradually, and after the voltage V ₁₂ drops to zero at time t _e , the voltage V ₁₁ becomes the voltage. It will gradually descend in line with _V4 .

When the power switch 2 is turned on again at time t _f immediately after time t _e , the voltage V ₄ across the main smoothing capacitor 4 immediately rises to its original value, but at this point the starting capacitor 11 has not been sufficiently discharged. Therefore, the residual voltage V ₁₁ ' of the starting capacitor 11 just before the power switch 2 is turned on again is quite high, and the voltage across the starting capacitor 11 and the drive circuit smoothing capacitor 12 immediately after the power switch 2 is turned on again is V ₁₁ , V. ₁₂ is
Since V ₁₁ = V ₁₁ ′+C ₁₂ /C ₁₁ +C ₁₂ (V ₄ −V ₁₁ ′) V ₁₂ =C ₁₁ /C ₁₁ +C ₁₂ (V ₄ −V ₁₁ ′), the voltage V ₁₂ is V ₁₂ <V _D , and the drive circuit 10 does not restart.

Note that the discharge of both capacitors 4 and 11 is performed mainly through the discharge resistor 5 having a high resistance value, and the voltages V ₄ and V ₁₁ drop extremely slowly, so that when the voltage V ₁₁ is turned on again, V ₁₂ > _VD , and even if the power switch 2 is turned on again during this time, the drive circuit 10 will not restart and high frequency power cannot be supplied to the load 14.

[Purpose of the invention]

An object of the present invention is to provide an inverter device that can reliably restart a drive circuit when AC power is turned on again.

[Disclosure of the invention]

The inverter device of the present invention includes a rectifier that rectifies an AC power supply voltage, a main smoothing capacitor connected to the output terminal of the rectifier, a switching element having one end connected to the low voltage side output terminal of the rectifier, and a low voltage side power input terminal. an inductance element connected between the high voltage side output terminal of the rectifier and the other end of the switching element; a resonant circuit consisting of a resonant capacitor connected in parallel to the switching element; a smoothing capacitor for the drive circuit connected between the high-voltage side power input terminal and the low-voltage side power input terminal of the drive circuit; A power supply circuit that includes a secondary winding and a rectifying diode and applies a rectified voltage between the high voltage side power input terminal and the low voltage side power input terminal of the drive circuit, and the high voltage side output terminal of the rectifier and the high voltage side power input terminal of the drive circuit. It includes a starting capacitor connected between the starting capacitor and the starting capacitor, and a discharging resistor connected in parallel to the starting capacitor.

According to the configuration of this invention, since the discharging resistor is connected in parallel with the starting capacitor, it is possible to speed up the discharging of the starting capacitor when the AC power supply is cut off. It is possible to accelerate the drop in voltage between both ends. In other words, the voltage across the drive circuit capacitor is ultimately the value obtained by dividing the voltage across the main smoothing capacitor by the discharging resistor and the power supply input impedance of the drive circuit, and as the voltage across the main smoothing capacitor decreases, It will descend more slowly than in the conventional example.

Therefore, even if the AC power supply is turned on again within a short time after being cut off, by that time the residual voltage of the smoothing capacitor for the drive circuit is sufficiently high, and conversely, the residual voltage of the starting capacitor is sufficiently low. ,
Even when the power is turned on again, the voltage across the drive circuit smoothing capacitor can be made higher than the minimum operable power supply voltage of the drive circuit, and the drive circuit can be restarted immediately.

Embodiment An embodiment of the present invention will be described based on FIGS. 1 to 4. This inverter device includes a rectifier 20 that rectifies a commercial AC power supply voltage, and a main smoothing capacitor 21 connected to the output terminal of the rectifier 20.
and a switching element 23 consisting of a transistor whose one end (emitter) is connected to the low voltage side output terminal (negative side) of the rectifier 20, and the low voltage side power input terminal (negative side) is connected to the low voltage side output terminal (negative side) of the rectifier 20. A drive circuit 24 connected to the switching element 23 and giving an on/off drive signal to the switching element 23, and a transformer (inductance) connected between the high voltage side output terminal (positive electrode side) of the rectifier 20 and the other end (collector) of the switching element 23. element) resonant capacitor 3 connected in parallel to the primary winding of 32 and the switching element 23
0, a drive circuit smoothing capacitor 26 connected between the high voltage side power input terminal (positive pole side) and the low voltage side power input terminal (negative pole side) of the drive circuit 24, and a transformer (inductance element) 3.
a power supply circuit 28 that includes a secondary winding of No. 2 and a rectifying diode 33 and applies a rectified voltage between the high-voltage side power input terminal (positive pole side) and the low-voltage side power input terminal (negative pole side) of the drive circuit 24; and the rectifier 20. A starting capacitor 2 connected between the high voltage side output terminal (positive side) of the drive circuit 24 and the high voltage side power input terminal (positive side) of the drive circuit 24.
5, and a discharging resistor 27 connected in parallel to the starting capacitor 25.

The structural difference between this embodiment and the conventional example is that a discharge resistor 27 is connected in parallel to the starting capacitor 25, and the rest is the same as the conventional example.
That is, in this inverter device, a rectifier 20 is connected to a commercial AC power source 18 via a power switch 19, a discharge resistor 29 is connected in parallel to a main smoothing capacitor 21, and a switching element 23, which is an example of a transistor, is connected to a rectifier 20 via a power switch 19. A resonant capacitor 30 and a damper diode 31 are connected in parallel, and a resonant circuit 34 is configured by the primary winding _N1 of the transformer 32, the load 22, and the resonant capacitor 30,
The secondary winding N ₂ of the transformer 32 and the diode 33 constitute a power supply circuit 28 .

Next, the operation of the smoothing capacitor 26 for the drive circuit of this inverter device and its surrounding parts will be explained in a second manner.
This will be explained with reference to the figures. Set the power switch 19 to the time.
When the power is turned on at t _g , the voltage V ₂₁ across the main smoothing capacitor 21 instantly rises to a constant value. Further, the starting capacitor 25 and the drive circuit smoothing capacitor 26 are connected in series to the main smoothing capacitor 26.
1 in parallel, so when the power is initially turned on,
The voltages V ₂₅ and V 26 across both capacitors 25 and ₂₆ are:
The voltage V ₂₁ is divided according to each capacitance. If the capacitance of the starting capacitor 25 is C ₂₅ and the capacitance of the drive circuit smoothing capacitor 26 is C ₂₆ , the voltage V ₂₅ across the starting capacitor 25 is V ₂₅ = C ₂₆ /C ₂₅ + C ₂₆ · V ₂₁ , and the drive circuit The voltage V ₂₆ across the smoothing capacitor 26 is V ₂₆ = C ₂₅ /C ₂₅ + C ₂₆ · V ₂₁ , and the voltage V ₂₆ is V ₂₆ > V _D with respect to the minimum operable power supply voltage V _D of the drive circuit 24. The partial pressure ratio is set so that

Then, by applying the voltage V ₂₆ to the power input terminal of the drive circuit 24, the drive circuit 24 is turned on/off.
The off-drive signal is output, thereby performing the above-described series of operations and supplying high-frequency power to the load 22.

On the other hand, the power supply input impedance Z of the drive circuit 24 is not infinite but has a predetermined value,
In addition, since the discharge resistor 27 is connected in parallel to the starting capacitor 25, the voltage V ₂₆ after the power is turned on is
The voltage V ₂₁ is divided by the discharging resistor 27 (resistance value R) and the power supply input impedance _Z of the drive circuit ₂₄ , and gradually decreases toward the voltage V ₂₅ , on the contrary, gradually increases, but at a time t _h before the voltage V ₂₆ becomes lower than the minimum operable power supply voltage V _D of the drive circuit 24, the secondary voltage of the transformer 32 is turned off by the on/off operation of the switching element 23. A voltage is induced in the winding _N2 , and the voltage is rectified by the diode 33 and applied to the power input terminal of the drive circuit 24, that is, both ends of the drive circuit smoothing capacitor 26. At that point, the voltage _V26 becomes The voltage V 25 stops increasing and remains constant (a constant voltage higher than the minimum operable power supply voltage V _D ), and therefore the voltage V ₂₅ also stops increasing and becomes constant.

Since the voltage V ₂₆ remains higher than the minimum operable power supply voltage V _D , the drive circuit 24 continues to output the on/off drive signal, and the high-frequency power continues to be supplied to the load 22. .

After the power is turned on and the voltages V ₂₁ , V ₂₅ , and V ₂₆ are stabilized, when the power switch 19 is turned off at operation time t _i , the power supply from the commercial AC power supply 18 is stopped, and the voltage across the main smoothing capacitor 21 is reduced to V ₂₁ is discharge resistor 2
The voltage gradually decreases due to the discharge through 9, etc., and the voltages V ₂₅ and V ₂₆ also change accordingly. In this case, the discharge resistor 27 is connected to the starting capacitor 25, and the power supply input impedance Z of the drive circuit 24 is connected in parallel to the drive circuit smoothing capacitor 26, so that the time t When the power switch 19 is turned off at _i , the voltages V ₂₅ and V ₂₆ decrease in accordance with the decrease in the voltage V ₂₁ . Here, _{the power supply input impedance Z of the drive circuit 24 is not constant, but changes non-linearly with respect to the voltage V 26 as} shown in FIG.
When descending below V _D , the power supply input impedance Z increases rapidly, and therefore Z/(Z+
The value of R) approaches 1, and the value of R/(Z+R) approaches 0.
As a result, the voltage V ₂₆ approaches the discharging resistor 2 when the drive circuit 24 is operating.
After the time t _k when the voltage has decreased to the divided voltage value _V
Even if the voltage V ₂₁ drops, it hardly drops and the voltage
Only V ₂₅ will fall as voltage V ₂₁ falls.

When the power switch 19 is turned on again at time t _j after time t _i , the voltages V ₂₅ and V ₂₆ across the starting capacitor 25 and the drive circuit smoothing capacitor 26 immediately after turning on again are V ₂₅ =V ₂₅ ' +C ₂₆ /C ₂₅ +C ₂₆ (V ₂₁ −V ₂₅ ′−V ₂₆ ′) V ₂₆ =V ₂₆ ′+C ₂₅ /C ₂₅ +C ₂₆ (V ₂₁ −V ₂₅ ′−V ₂₆ ′). The residual voltage V ₂₅ ′ of the starting capacitor 25 just before the power is turned on again is sufficiently low, and the residual voltage V ₂₆ ′ of the drive circuit smoothing capacitor 26 maintains a value sufficiently close to the minimum operable power supply voltage V _D . , the voltage V ₂₆ becomes V ₂₆ >V _D , and the drive circuit 24 is restarted.

Note that the operations of the switching element 23, the resonant circuit 34, etc. in response to the on/off drive signal output from the drive circuit 24 are the same as in the conventional example.

Furthermore, in this embodiment, as shown in FIG. 4, the discharge path of the main smoothing capacitor 21 is formed by connecting the discharge resistor 27 in parallel with the starting capacitor 25, so that the discharge path is particularly connected to the discharge resistor 29. It has the advantage that it does not need to be equipped with.

In the present invention, even if two switching elements are provided, if the power supply section of the drive circuit 24 has the same configuration as in the above-described embodiment, restartability can be similarly improved.

〔Effect of the invention〕

According to the inverter device of the present invention, since the discharging resistor is connected in parallel with the starting capacitor, the starting capacitor can be discharged more quickly when the AC power source is cut off than the conventional inverter device. In other words, the voltage across the drive circuit capacitor is ultimately the value obtained by dividing the voltage across the main smoothing capacitor by the discharging resistor and the power supply input impedance of the drive circuit, and as the voltage across the main smoothing capacitor decreases, It will descend more slowly than in the conventional example.

Therefore, even if the AC power supply is turned on again within a short time after being cut off, by that time the residual voltage of the smoothing capacitor for the drive circuit is sufficiently high, and conversely, the residual voltage of the starting capacitor is sufficiently low. ,
When the power is turned on again, the voltage across the drive circuit smoothing capacitor can be made higher than the minimum operable power supply voltage of the drive circuit, and the drive circuit can be restarted immediately.

In other words, according to the inverter device of this invention,
A discharge resistor is connected in parallel to the starting capacitor connected between the output terminal of the rectifier and the power input terminal of the drive circuit, so that when the power switch is cut off, the accumulated charge in the starting capacitor is quickly released. Because of this structure, even when the power switch is turned off and then turned on again, the voltage across the smoothing capacitor for the drive circuit quickly rises to the voltage at which the drive circuit can operate. Even if the power is turned on again, the drive circuit can be restarted without waiting time and the supply of power to the load can be started.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of the embodiment,
Fig. 3 is a diagram showing the relationship between the impedance of the drive circuit and the voltage _V26 , Fig. 4 is a circuit diagram showing a modified example, Fig. 5 is a circuit diagram showing the configuration of a conventional example, and Figs. 6 and 7 are Diagram for explaining the operation of the conventional example, No. 8
The figure is a diagram for explaining the problems of the conventional example. 20... Rectifier, 21... Main smoothing capacitor, 22
...Load, 23...Switching element, 24...Drive circuit, 25...Starting capacitor, 26...Smoothing capacitor for drive circuit, 27...Discharge resistor, 28...Power supply circuit, 30...Resonance capacitor, 31...Diode, 32...Transformer (inductance element), 3
3...diode, 34...resonant circuit.

Claims (1)

[Claims] 1. A rectifier that rectifies AC power supply voltage, a main smoothing capacitor connected to the output terminal of this rectifier, a switching element whose one end is connected to the low voltage side output terminal of the rectifier, and a low voltage side power input terminal connected to the low voltage side of the rectifier. a drive circuit connected to the output terminal and giving an on/off drive signal to the switching element; an inductance element connected between the high voltage side output terminal of the rectifier and the other end of the switching element; and a parallel connection to the switching element. a resonant circuit consisting of a resonant capacitor, a smoothing capacitor for the drive circuit connected between the high-voltage side power input terminal and the low-voltage side power input terminal of the drive circuit, a secondary winding provided in the inductance element, and a rectifying circuit. A power supply circuit comprising a diode and applying a rectified voltage between a high voltage side power input terminal and a low voltage side power input terminal of the drive circuit, and a power supply circuit connected between the high voltage side output terminal of the rectifier and the high voltage side power input terminal of the drive circuit. An inverter device equipped with a starting capacitor and a discharging resistor connected in parallel to the starting capacitor.